diff --git a/configure.in b/configure.in
index a6165281e34f2b6b01d0458f9b1bddfabacf0205..2054fb2b730b53f8c777c47637bf9e678ae8c8c8 100644
--- a/configure.in
+++ b/configure.in
@@ -74,7 +74,7 @@ GNOMEUI_VERSION=2.2.0
 GCONF_VERSION=1.2.1
 STARTUP_NOTIFICATION_VERSION=0.8
 DBUS_VERSION=0.60
-SQLITE_VERSION=3.8.10.1
+SQLITE_VERSION=3.8.11.1
 
 MSMANIFEST_TOOL=
 
diff --git a/db/sqlite3/src/sqlite3.c b/db/sqlite3/src/sqlite3.c
index 6708aa2d8221045e2c80cd939fd57675fc174afe..1344938873b4ec0840afde73908e47a18bfc7a58 100644
--- a/db/sqlite3/src/sqlite3.c
+++ b/db/sqlite3/src/sqlite3.c
@@ -1,6 +1,6 @@
 /******************************************************************************
 ** This file is an amalgamation of many separate C source files from SQLite
-** version 3.8.10.1.  By combining all the individual C code files into this 
+** version 3.8.11.1.  By combining all the individual C code files into this 
 ** single large file, the entire code can be compiled as a single translation
 ** unit.  This allows many compilers to do optimizations that would not be
 ** possible if the files were compiled separately.  Performance improvements
@@ -158,6 +158,13 @@
 # define _LARGEFILE_SOURCE 1
 #endif
 
+/* What version of GCC is being used.  0 means GCC is not being used */
+#ifdef __GNUC__
+# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
+#else
+# define GCC_VERSION 0
+#endif
+
 /* Needed for various definitions... */
 #if defined(__GNUC__) && !defined(_GNU_SOURCE)
 # define _GNU_SOURCE
@@ -230,7 +237,7 @@
 **
 ** The official C-language API documentation for SQLite is derived
 ** from comments in this file.  This file is the authoritative source
-** on how SQLite interfaces are suppose to operate.
+** on how SQLite interfaces are supposed to operate.
 **
 ** The name of this file under configuration management is "sqlite.h.in".
 ** The makefile makes some minor changes to this file (such as inserting
@@ -318,9 +325,9 @@ extern "C" {
 ** [sqlite3_libversion_number()], [sqlite3_sourceid()],
 ** [sqlite_version()] and [sqlite_source_id()].
 */
-#define SQLITE_VERSION        "3.8.10.1"
-#define SQLITE_VERSION_NUMBER 3008010
-#define SQLITE_SOURCE_ID      "2015-05-09 12:14:55 05b4b1f2a937c06c90db70c09890038f6c98ec40"
+#define SQLITE_VERSION        "3.8.11.1"
+#define SQLITE_VERSION_NUMBER 3008011
+#define SQLITE_SOURCE_ID      "2015-07-29 20:00:57 cf538e2783e468bbc25e7cb2a9ee64d3e0e80b2f"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
@@ -1170,6 +1177,14 @@ struct sqlite3_io_methods {
 ** circumstances in order to fix a problem with priority inversion.
 ** Applications should <em>not</em> use this file-control.
 **
+** <li>[[SQLITE_FCNTL_ZIPVFS]]
+** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
+** VFS should return SQLITE_NOTFOUND for this opcode.
+**
+** <li>[[SQLITE_FCNTL_RBU]]
+** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
+** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
+** this opcode.  
 ** </ul>
 */
 #define SQLITE_FCNTL_LOCKSTATE               1
@@ -1195,6 +1210,8 @@ struct sqlite3_io_methods {
 #define SQLITE_FCNTL_COMMIT_PHASETWO        22
 #define SQLITE_FCNTL_WIN32_SET_HANDLE       23
 #define SQLITE_FCNTL_WAL_BLOCK              24
+#define SQLITE_FCNTL_ZIPVFS                 25
+#define SQLITE_FCNTL_RBU                    26
 
 /* deprecated names */
 #define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
@@ -3597,7 +3614,9 @@ SQLITE_API int SQLITE_STDCALL sqlite3_stmt_busy(sqlite3_stmt*);
 ** Some interfaces require a protected sqlite3_value.  Other interfaces
 ** will accept either a protected or an unprotected sqlite3_value.
 ** Every interface that accepts sqlite3_value arguments specifies
-** whether or not it requires a protected sqlite3_value.
+** whether or not it requires a protected sqlite3_value.  The
+** [sqlite3_value_dup()] interface can be used to construct a new 
+** protected sqlite3_value from an unprotected sqlite3_value.
 **
 ** The terms "protected" and "unprotected" refer to whether or not
 ** a mutex is held.  An internal mutex is held for a protected
@@ -3757,6 +3776,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_bind_text64(sqlite3_stmt*, int, const char
                          void(*)(void*), unsigned char encoding);
 SQLITE_API int SQLITE_STDCALL sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
 SQLITE_API int SQLITE_STDCALL sqlite3_bind_zeroblob(sqlite3_stmt*, int, int n);
+SQLITE_API int SQLITE_STDCALL sqlite3_bind_zeroblob64(sqlite3_stmt*, int, sqlite3_uint64);
 
 /*
 ** CAPI3REF: Number Of SQL Parameters
@@ -4100,8 +4120,6 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** KEYWORDS: {column access functions}
 ** METHOD: sqlite3_stmt
 **
-** These routines form the "result set" interface.
-**
 ** ^These routines return information about a single column of the current
 ** result row of a query.  ^In every case the first argument is a pointer
 ** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
@@ -4161,13 +4179,14 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** even empty strings, are always zero-terminated.  ^The return
 ** value from sqlite3_column_blob() for a zero-length BLOB is a NULL pointer.
 **
-** ^The object returned by [sqlite3_column_value()] is an
-** [unprotected sqlite3_value] object.  An unprotected sqlite3_value object
-** may only be used with [sqlite3_bind_value()] and [sqlite3_result_value()].
+** <b>Warning:</b> ^The object returned by [sqlite3_column_value()] is an
+** [unprotected sqlite3_value] object.  In a multithreaded environment,
+** an unprotected sqlite3_value object may only be used safely with
+** [sqlite3_bind_value()] and [sqlite3_result_value()].
 ** If the [unprotected sqlite3_value] object returned by
 ** [sqlite3_column_value()] is used in any other way, including calls
 ** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
-** or [sqlite3_value_bytes()], then the behavior is undefined.
+** or [sqlite3_value_bytes()], the behavior is not threadsafe.
 **
 ** These routines attempt to convert the value where appropriate.  ^For
 ** example, if the internal representation is FLOAT and a text result
@@ -4198,12 +4217,6 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** </table>
 ** </blockquote>)^
 **
-** The table above makes reference to standard C library functions atoi()
-** and atof().  SQLite does not really use these functions.  It has its
-** own equivalent internal routines.  The atoi() and atof() names are
-** used in the table for brevity and because they are familiar to most
-** C programmers.
-**
 ** Note that when type conversions occur, pointers returned by prior
 ** calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
 ** sqlite3_column_text16() may be invalidated.
@@ -4228,7 +4241,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** of conversion are done in place when it is possible, but sometimes they
 ** are not possible and in those cases prior pointers are invalidated.
 **
-** The safest and easiest to remember policy is to invoke these routines
+** The safest policy is to invoke these routines
 ** in one of the following ways:
 **
 ** <ul>
@@ -4248,7 +4261,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** ^The pointers returned are valid until a type conversion occurs as
 ** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
 ** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
-** and BLOBs is freed automatically.  Do <b>not</b> pass the pointers returned
+** and BLOBs is freed automatically.  Do <em>not</em> pass the pointers returned
 ** from [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
 ** [sqlite3_free()].
 **
@@ -4498,12 +4511,12 @@ SQLITE_API SQLITE_DEPRECATED int SQLITE_STDCALL sqlite3_memory_alarm(void(*)(voi
 #endif
 
 /*
-** CAPI3REF: Obtaining SQL Function Parameter Values
+** CAPI3REF: Obtaining SQL Values
 ** METHOD: sqlite3_value
 **
 ** The C-language implementation of SQL functions and aggregates uses
 ** this set of interface routines to access the parameter values on
-** the function or aggregate.
+** the function or aggregate.  
 **
 ** The xFunc (for scalar functions) or xStep (for aggregates) parameters
 ** to [sqlite3_create_function()] and [sqlite3_create_function16()]
@@ -4556,6 +4569,23 @@ SQLITE_API const void *SQLITE_STDCALL sqlite3_value_text16be(sqlite3_value*);
 SQLITE_API int SQLITE_STDCALL sqlite3_value_type(sqlite3_value*);
 SQLITE_API int SQLITE_STDCALL sqlite3_value_numeric_type(sqlite3_value*);
 
+/*
+** CAPI3REF: Copy And Free SQL Values
+** METHOD: sqlite3_value
+**
+** ^The sqlite3_value_dup(V) interface makes a copy of the [sqlite3_value]
+** object D and returns a pointer to that copy.  ^The [sqlite3_value] returned
+** is a [protected sqlite3_value] object even if the input is not.
+** ^The sqlite3_value_dup(V) interface returns NULL if V is NULL or if a
+** memory allocation fails.
+**
+** ^The sqlite3_value_free(V) interface frees an [sqlite3_value] object
+** previously obtained from [sqlite3_value_dup()].  ^If V is a NULL pointer
+** then sqlite3_value_free(V) is a harmless no-op.
+*/
+SQLITE_API SQLITE_EXPERIMENTAL sqlite3_value *SQLITE_STDCALL sqlite3_value_dup(const sqlite3_value*);
+SQLITE_API SQLITE_EXPERIMENTAL void SQLITE_STDCALL sqlite3_value_free(sqlite3_value*);
+
 /*
 ** CAPI3REF: Obtain Aggregate Function Context
 ** METHOD: sqlite3_context
@@ -4719,9 +4749,9 @@ typedef void (*sqlite3_destructor_type)(void*);
 ** to by the second parameter and which is N bytes long where N is the
 ** third parameter.
 **
-** ^The sqlite3_result_zeroblob() interfaces set the result of
-** the application-defined function to be a BLOB containing all zero
-** bytes and N bytes in size, where N is the value of the 2nd parameter.
+** ^The sqlite3_result_zeroblob(C,N) and sqlite3_result_zeroblob64(C,N)
+** interfaces set the result of the application-defined function to be
+** a BLOB containing all zero bytes and N bytes in size.
 **
 ** ^The sqlite3_result_double() interface sets the result from
 ** an application-defined function to be a floating point value specified
@@ -4803,7 +4833,7 @@ typedef void (*sqlite3_destructor_type)(void*);
 ** from [sqlite3_malloc()] before it returns.
 **
 ** ^The sqlite3_result_value() interface sets the result of
-** the application-defined function to be a copy the
+** the application-defined function to be a copy of the
 ** [unprotected sqlite3_value] object specified by the 2nd parameter.  ^The
 ** sqlite3_result_value() interface makes a copy of the [sqlite3_value]
 ** so that the [sqlite3_value] specified in the parameter may change or
@@ -4836,6 +4866,7 @@ SQLITE_API void SQLITE_STDCALL sqlite3_result_text16le(sqlite3_context*, const v
 SQLITE_API void SQLITE_STDCALL sqlite3_result_text16be(sqlite3_context*, const void*, int,void(*)(void*));
 SQLITE_API void SQLITE_STDCALL sqlite3_result_value(sqlite3_context*, sqlite3_value*);
 SQLITE_API void SQLITE_STDCALL sqlite3_result_zeroblob(sqlite3_context*, int n);
+SQLITE_API int SQLITE_STDCALL sqlite3_result_zeroblob64(sqlite3_context*, sqlite3_uint64 n);
 
 /*
 ** CAPI3REF: Define New Collating Sequences
@@ -6079,7 +6110,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_blob_open(
 **
 ** ^This function sets the database handle error code and message.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_blob_reopen(sqlite3_blob *, sqlite3_int64);
+SQLITE_API int SQLITE_STDCALL sqlite3_blob_reopen(sqlite3_blob *, sqlite3_int64);
 
 /*
 ** CAPI3REF: Close A BLOB Handle
@@ -6476,6 +6507,9 @@ SQLITE_API int SQLITE_STDCALL sqlite3_mutex_notheld(sqlite3_mutex*);
 #define SQLITE_MUTEX_STATIC_APP1      8  /* For use by application */
 #define SQLITE_MUTEX_STATIC_APP2      9  /* For use by application */
 #define SQLITE_MUTEX_STATIC_APP3     10  /* For use by application */
+#define SQLITE_MUTEX_STATIC_VFS1     11  /* For use by built-in VFS */
+#define SQLITE_MUTEX_STATIC_VFS2     12  /* For use by extension VFS */
+#define SQLITE_MUTEX_STATIC_VFS3     13  /* For use by application VFS */
 
 /*
 ** CAPI3REF: Retrieve the mutex for a database connection
@@ -7889,7 +7923,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_vtab_on_conflict(sqlite3 *);
 **
 ** See also: [sqlite3_stmt_scanstatus_reset()]
 */
-SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_stmt_scanstatus(
+SQLITE_API int SQLITE_STDCALL sqlite3_stmt_scanstatus(
   sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
   int idx,                  /* Index of loop to report on */
   int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
@@ -7905,7 +7939,7 @@ SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_stmt_scanstatus(
 ** This API is only available if the library is built with pre-processor
 ** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.
 */
-SQLITE_API SQLITE_EXPERIMENTAL void SQLITE_STDCALL sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);
+SQLITE_API void SQLITE_STDCALL sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);
 
 
 /*
@@ -8020,6 +8054,8 @@ struct sqlite3_rtree_query_info {
   int eParentWithin;                /* Visibility of parent node */
   int eWithin;                      /* OUT: Visiblity */
   sqlite3_rtree_dbl rScore;         /* OUT: Write the score here */
+  /* The following fields are only available in 3.8.11 and later */
+  sqlite3_value **apSqlParam;       /* Original SQL values of parameters */
 };
 
 /*
@@ -8325,6 +8361,20 @@ struct sqlite3_rtree_query_info {
 #  define SQLITE_NOINLINE
 #endif
 
+/*
+** Make sure that the compiler intrinsics we desire are enabled when
+** compiling with an appropriate version of MSVC.
+*/
+#if defined(_MSC_VER) && _MSC_VER>=1300
+#  if !defined(_WIN32_WCE)
+#    include <intrin.h>
+#    pragma intrinsic(_byteswap_ushort)
+#    pragma intrinsic(_byteswap_ulong)
+#  else
+#    include <cmnintrin.h>
+#  endif
+#endif
+
 /*
 ** The SQLITE_THREADSAFE macro must be defined as 0, 1, or 2.
 ** 0 means mutexes are permanently disable and the library is never
@@ -8902,6 +8952,16 @@ SQLITE_PRIVATE void sqlite3HashClear(Hash*);
 # define SQLITE_MAX_WORKER_THREADS SQLITE_DEFAULT_WORKER_THREADS
 #endif
 
+/*
+** The default initial allocation for the pagecache when using separate
+** pagecaches for each database connection.  A positive number is the
+** number of pages.  A negative number N translations means that a buffer
+** of -1024*N bytes is allocated and used for as many pages as it will hold.
+*/
+#ifndef SQLITE_DEFAULT_PCACHE_INITSZ
+# define SQLITE_DEFAULT_PCACHE_INITSZ 100
+#endif
+
 
 /*
 ** GCC does not define the offsetof() macro so we'll have to do it
@@ -9137,7 +9197,9 @@ SQLITE_PRIVATE const int sqlite3one;
 # if defined(__linux__) \
   || defined(_WIN32) \
   || (defined(__APPLE__) && defined(__MACH__)) \
-  || defined(__sun)
+  || defined(__sun) \
+  || defined(__FreeBSD__) \
+  || defined(__DragonFly__)
 #   define SQLITE_MAX_MMAP_SIZE 0x7fff0000  /* 2147418112 */
 # else
 #   define SQLITE_MAX_MMAP_SIZE 0
@@ -9667,13 +9729,14 @@ struct VdbeOp {
   int p1;             /* First operand */
   int p2;             /* Second parameter (often the jump destination) */
   int p3;             /* The third parameter */
-  union {             /* fourth parameter */
+  union p4union {     /* fourth parameter */
     int i;                 /* Integer value if p4type==P4_INT32 */
     void *p;               /* Generic pointer */
     char *z;               /* Pointer to data for string (char array) types */
     i64 *pI64;             /* Used when p4type is P4_INT64 */
     double *pReal;         /* Used when p4type is P4_REAL */
     FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
+    sqlite3_context *pCtx; /* Used when p4type is P4_FUNCCTX */
     CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
     Mem *pMem;             /* Used when p4type is P4_MEM */
     VTable *pVtab;         /* Used when p4type is P4_VTAB */
@@ -9740,6 +9803,7 @@ typedef struct VdbeOpList VdbeOpList;
 #define P4_INTARRAY (-15) /* P4 is a vector of 32-bit integers */
 #define P4_SUBPROGRAM  (-18) /* P4 is a pointer to a SubProgram structure */
 #define P4_ADVANCE  (-19) /* P4 is a pointer to BtreeNext() or BtreePrev() */
+#define P4_FUNCCTX  (-20) /* P4 is a pointer to an sqlite3_context object */
 
 /* Error message codes for OP_Halt */
 #define P5_ConstraintNotNull 1
@@ -9782,42 +9846,42 @@ typedef struct VdbeOpList VdbeOpList;
 /************** Begin file opcodes.h *****************************************/
 /* Automatically generated.  Do not edit */
 /* See the mkopcodeh.awk script for details */
-#define OP_Function        1 /* synopsis: r[P3]=func(r[P2@P5])             */
-#define OP_Savepoint       2
-#define OP_AutoCommit      3
-#define OP_Transaction     4
-#define OP_SorterNext      5
-#define OP_PrevIfOpen      6
-#define OP_NextIfOpen      7
-#define OP_Prev            8
-#define OP_Next            9
-#define OP_AggStep        10 /* synopsis: accum=r[P3] step(r[P2@P5])       */
-#define OP_Checkpoint     11
-#define OP_JournalMode    12
-#define OP_Vacuum         13
-#define OP_VFilter        14 /* synopsis: iplan=r[P3] zplan='P4'           */
-#define OP_VUpdate        15 /* synopsis: data=r[P3@P2]                    */
-#define OP_Goto           16
-#define OP_Gosub          17
-#define OP_Return         18
+#define OP_Savepoint       1
+#define OP_AutoCommit      2
+#define OP_Transaction     3
+#define OP_SorterNext      4
+#define OP_PrevIfOpen      5
+#define OP_NextIfOpen      6
+#define OP_Prev            7
+#define OP_Next            8
+#define OP_Checkpoint      9
+#define OP_JournalMode    10
+#define OP_Vacuum         11
+#define OP_VFilter        12 /* synopsis: iplan=r[P3] zplan='P4'           */
+#define OP_VUpdate        13 /* synopsis: data=r[P3@P2]                    */
+#define OP_Goto           14
+#define OP_Gosub          15
+#define OP_Return         16
+#define OP_InitCoroutine  17
+#define OP_EndCoroutine   18
 #define OP_Not            19 /* same as TK_NOT, synopsis: r[P2]= !r[P1]    */
-#define OP_InitCoroutine  20
-#define OP_EndCoroutine   21
-#define OP_Yield          22
-#define OP_HaltIfNull     23 /* synopsis: if r[P3]=null halt               */
-#define OP_Halt           24
-#define OP_Integer        25 /* synopsis: r[P2]=P1                         */
-#define OP_Int64          26 /* synopsis: r[P2]=P4                         */
-#define OP_String         27 /* synopsis: r[P2]='P4' (len=P1)              */
-#define OP_Null           28 /* synopsis: r[P2..P3]=NULL                   */
-#define OP_SoftNull       29 /* synopsis: r[P1]=NULL                       */
-#define OP_Blob           30 /* synopsis: r[P2]=P4 (len=P1)                */
-#define OP_Variable       31 /* synopsis: r[P2]=parameter(P1,P4)           */
-#define OP_Move           32 /* synopsis: r[P2@P3]=r[P1@P3]                */
-#define OP_Copy           33 /* synopsis: r[P2@P3+1]=r[P1@P3+1]            */
-#define OP_SCopy          34 /* synopsis: r[P2]=r[P1]                      */
-#define OP_ResultRow      35 /* synopsis: output=r[P1@P2]                  */
-#define OP_CollSeq        36
+#define OP_Yield          20
+#define OP_HaltIfNull     21 /* synopsis: if r[P3]=null halt               */
+#define OP_Halt           22
+#define OP_Integer        23 /* synopsis: r[P2]=P1                         */
+#define OP_Int64          24 /* synopsis: r[P2]=P4                         */
+#define OP_String         25 /* synopsis: r[P2]='P4' (len=P1)              */
+#define OP_Null           26 /* synopsis: r[P2..P3]=NULL                   */
+#define OP_SoftNull       27 /* synopsis: r[P1]=NULL                       */
+#define OP_Blob           28 /* synopsis: r[P2]=P4 (len=P1)                */
+#define OP_Variable       29 /* synopsis: r[P2]=parameter(P1,P4)           */
+#define OP_Move           30 /* synopsis: r[P2@P3]=r[P1@P3]                */
+#define OP_Copy           31 /* synopsis: r[P2@P3+1]=r[P1@P3+1]            */
+#define OP_SCopy          32 /* synopsis: r[P2]=r[P1]                      */
+#define OP_ResultRow      33 /* synopsis: output=r[P1@P2]                  */
+#define OP_CollSeq        34
+#define OP_Function0      35 /* synopsis: r[P3]=func(r[P2@P5])             */
+#define OP_Function       36 /* synopsis: r[P3]=func(r[P2@P5])             */
 #define OP_AddImm         37 /* synopsis: r[P1]=r[P1]+P2                   */
 #define OP_MustBeInt      38
 #define OP_RealAffinity   39
@@ -9843,20 +9907,20 @@ typedef struct VdbeOpList VdbeOpList;
 #define OP_SequenceTest   59 /* synopsis: if( cursor[P1].ctr++ ) pc = P2   */
 #define OP_OpenPseudo     60 /* synopsis: P3 columns in r[P2]              */
 #define OP_Close          61
-#define OP_SeekLT         62 /* synopsis: key=r[P3@P4]                     */
-#define OP_SeekLE         63 /* synopsis: key=r[P3@P4]                     */
-#define OP_SeekGE         64 /* synopsis: key=r[P3@P4]                     */
-#define OP_SeekGT         65 /* synopsis: key=r[P3@P4]                     */
-#define OP_Seek           66 /* synopsis: intkey=r[P2]                     */
-#define OP_NoConflict     67 /* synopsis: key=r[P3@P4]                     */
-#define OP_NotFound       68 /* synopsis: key=r[P3@P4]                     */
-#define OP_Found          69 /* synopsis: key=r[P3@P4]                     */
-#define OP_NotExists      70 /* synopsis: intkey=r[P3]                     */
+#define OP_ColumnsUsed    62
+#define OP_SeekLT         63 /* synopsis: key=r[P3@P4]                     */
+#define OP_SeekLE         64 /* synopsis: key=r[P3@P4]                     */
+#define OP_SeekGE         65 /* synopsis: key=r[P3@P4]                     */
+#define OP_SeekGT         66 /* synopsis: key=r[P3@P4]                     */
+#define OP_Seek           67 /* synopsis: intkey=r[P2]                     */
+#define OP_NoConflict     68 /* synopsis: key=r[P3@P4]                     */
+#define OP_NotFound       69 /* synopsis: key=r[P3@P4]                     */
+#define OP_Found          70 /* synopsis: key=r[P3@P4]                     */
 #define OP_Or             71 /* same as TK_OR, synopsis: r[P3]=(r[P1] || r[P2]) */
 #define OP_And            72 /* same as TK_AND, synopsis: r[P3]=(r[P1] && r[P2]) */
-#define OP_Sequence       73 /* synopsis: r[P2]=cursor[P1].ctr++           */
-#define OP_NewRowid       74 /* synopsis: r[P2]=rowid                      */
-#define OP_Insert         75 /* synopsis: intkey=r[P3] data=r[P2]          */
+#define OP_NotExists      73 /* synopsis: intkey=r[P3]                     */
+#define OP_Sequence       74 /* synopsis: r[P2]=cursor[P1].ctr++           */
+#define OP_NewRowid       75 /* synopsis: r[P2]=rowid                      */
 #define OP_IsNull         76 /* same as TK_ISNULL, synopsis: if r[P1]==NULL goto P2 */
 #define OP_NotNull        77 /* same as TK_NOTNULL, synopsis: if r[P1]!=NULL goto P2 */
 #define OP_Ne             78 /* same as TK_NE, synopsis: if r[P1]!=r[P3] goto P2 */
@@ -9865,7 +9929,7 @@ typedef struct VdbeOpList VdbeOpList;
 #define OP_Le             81 /* same as TK_LE, synopsis: if r[P1]<=r[P3] goto P2 */
 #define OP_Lt             82 /* same as TK_LT, synopsis: if r[P1]<r[P3] goto P2 */
 #define OP_Ge             83 /* same as TK_GE, synopsis: if r[P1]>=r[P3] goto P2 */
-#define OP_InsertInt      84 /* synopsis: intkey=P3 data=r[P2]             */
+#define OP_Insert         84 /* synopsis: intkey=r[P3] data=r[P2]          */
 #define OP_BitAnd         85 /* same as TK_BITAND, synopsis: r[P3]=r[P1]&r[P2] */
 #define OP_BitOr          86 /* same as TK_BITOR, synopsis: r[P3]=r[P1]|r[P2] */
 #define OP_ShiftLeft      87 /* same as TK_LSHIFT, synopsis: r[P3]=r[P2]<<r[P1] */
@@ -9876,69 +9940,72 @@ typedef struct VdbeOpList VdbeOpList;
 #define OP_Divide         92 /* same as TK_SLASH, synopsis: r[P3]=r[P2]/r[P1] */
 #define OP_Remainder      93 /* same as TK_REM, synopsis: r[P3]=r[P2]%r[P1] */
 #define OP_Concat         94 /* same as TK_CONCAT, synopsis: r[P3]=r[P2]+r[P1] */
-#define OP_Delete         95
+#define OP_InsertInt      95 /* synopsis: intkey=P3 data=r[P2]             */
 #define OP_BitNot         96 /* same as TK_BITNOT, synopsis: r[P1]= ~r[P1] */
 #define OP_String8        97 /* same as TK_STRING, synopsis: r[P2]='P4'    */
-#define OP_ResetCount     98
-#define OP_SorterCompare  99 /* synopsis: if key(P1)!=trim(r[P3],P4) goto P2 */
-#define OP_SorterData    100 /* synopsis: r[P2]=data                       */
-#define OP_RowKey        101 /* synopsis: r[P2]=key                        */
-#define OP_RowData       102 /* synopsis: r[P2]=data                       */
-#define OP_Rowid         103 /* synopsis: r[P2]=rowid                      */
-#define OP_NullRow       104
-#define OP_Last          105
-#define OP_SorterSort    106
-#define OP_Sort          107
-#define OP_Rewind        108
-#define OP_SorterInsert  109
-#define OP_IdxInsert     110 /* synopsis: key=r[P2]                        */
-#define OP_IdxDelete     111 /* synopsis: key=r[P2@P3]                     */
-#define OP_IdxRowid      112 /* synopsis: r[P2]=rowid                      */
-#define OP_IdxLE         113 /* synopsis: key=r[P3@P4]                     */
-#define OP_IdxGT         114 /* synopsis: key=r[P3@P4]                     */
-#define OP_IdxLT         115 /* synopsis: key=r[P3@P4]                     */
-#define OP_IdxGE         116 /* synopsis: key=r[P3@P4]                     */
-#define OP_Destroy       117
-#define OP_Clear         118
-#define OP_ResetSorter   119
-#define OP_CreateIndex   120 /* synopsis: r[P2]=root iDb=P1                */
-#define OP_CreateTable   121 /* synopsis: r[P2]=root iDb=P1                */
-#define OP_ParseSchema   122
-#define OP_LoadAnalysis  123
-#define OP_DropTable     124
-#define OP_DropIndex     125
-#define OP_DropTrigger   126
-#define OP_IntegrityCk   127
-#define OP_RowSetAdd     128 /* synopsis: rowset(P1)=r[P2]                 */
-#define OP_RowSetRead    129 /* synopsis: r[P3]=rowset(P1)                 */
-#define OP_RowSetTest    130 /* synopsis: if r[P3] in rowset(P1) goto P2   */
-#define OP_Program       131
-#define OP_Param         132
+#define OP_Delete         98
+#define OP_ResetCount     99
+#define OP_SorterCompare 100 /* synopsis: if key(P1)!=trim(r[P3],P4) goto P2 */
+#define OP_SorterData    101 /* synopsis: r[P2]=data                       */
+#define OP_RowKey        102 /* synopsis: r[P2]=key                        */
+#define OP_RowData       103 /* synopsis: r[P2]=data                       */
+#define OP_Rowid         104 /* synopsis: r[P2]=rowid                      */
+#define OP_NullRow       105
+#define OP_Last          106
+#define OP_SorterSort    107
+#define OP_Sort          108
+#define OP_Rewind        109
+#define OP_SorterInsert  110
+#define OP_IdxInsert     111 /* synopsis: key=r[P2]                        */
+#define OP_IdxDelete     112 /* synopsis: key=r[P2@P3]                     */
+#define OP_IdxRowid      113 /* synopsis: r[P2]=rowid                      */
+#define OP_IdxLE         114 /* synopsis: key=r[P3@P4]                     */
+#define OP_IdxGT         115 /* synopsis: key=r[P3@P4]                     */
+#define OP_IdxLT         116 /* synopsis: key=r[P3@P4]                     */
+#define OP_IdxGE         117 /* synopsis: key=r[P3@P4]                     */
+#define OP_Destroy       118
+#define OP_Clear         119
+#define OP_ResetSorter   120
+#define OP_CreateIndex   121 /* synopsis: r[P2]=root iDb=P1                */
+#define OP_CreateTable   122 /* synopsis: r[P2]=root iDb=P1                */
+#define OP_ParseSchema   123
+#define OP_LoadAnalysis  124
+#define OP_DropTable     125
+#define OP_DropIndex     126
+#define OP_DropTrigger   127
+#define OP_IntegrityCk   128
+#define OP_RowSetAdd     129 /* synopsis: rowset(P1)=r[P2]                 */
+#define OP_RowSetRead    130 /* synopsis: r[P3]=rowset(P1)                 */
+#define OP_RowSetTest    131 /* synopsis: if r[P3] in rowset(P1) goto P2   */
+#define OP_Program       132
 #define OP_Real          133 /* same as TK_FLOAT, synopsis: r[P2]=P4       */
-#define OP_FkCounter     134 /* synopsis: fkctr[P1]+=P2                    */
-#define OP_FkIfZero      135 /* synopsis: if fkctr[P1]==0 goto P2          */
-#define OP_MemMax        136 /* synopsis: r[P1]=max(r[P1],r[P2])           */
-#define OP_IfPos         137 /* synopsis: if r[P1]>0 goto P2               */
-#define OP_IfNeg         138 /* synopsis: r[P1]+=P3, if r[P1]<0 goto P2    */
-#define OP_IfNotZero     139 /* synopsis: if r[P1]!=0 then r[P1]+=P3, goto P2 */
-#define OP_DecrJumpZero  140 /* synopsis: if (--r[P1])==0 goto P2          */
-#define OP_JumpZeroIncr  141 /* synopsis: if (r[P1]++)==0 ) goto P2        */
-#define OP_AggFinal      142 /* synopsis: accum=r[P1] N=P2                 */
-#define OP_IncrVacuum    143
-#define OP_Expire        144
-#define OP_TableLock     145 /* synopsis: iDb=P1 root=P2 write=P3          */
-#define OP_VBegin        146
-#define OP_VCreate       147
-#define OP_VDestroy      148
-#define OP_VOpen         149
-#define OP_VColumn       150 /* synopsis: r[P3]=vcolumn(P2)                */
-#define OP_VNext         151
-#define OP_VRename       152
-#define OP_Pagecount     153
-#define OP_MaxPgcnt      154
-#define OP_Init          155 /* synopsis: Start at P2                      */
-#define OP_Noop          156
-#define OP_Explain       157
+#define OP_Param         134
+#define OP_FkCounter     135 /* synopsis: fkctr[P1]+=P2                    */
+#define OP_FkIfZero      136 /* synopsis: if fkctr[P1]==0 goto P2          */
+#define OP_MemMax        137 /* synopsis: r[P1]=max(r[P1],r[P2])           */
+#define OP_IfPos         138 /* synopsis: if r[P1]>0 goto P2               */
+#define OP_IfNeg         139 /* synopsis: r[P1]+=P3, if r[P1]<0 goto P2    */
+#define OP_IfNotZero     140 /* synopsis: if r[P1]!=0 then r[P1]+=P3, goto P2 */
+#define OP_DecrJumpZero  141 /* synopsis: if (--r[P1])==0 goto P2          */
+#define OP_JumpZeroIncr  142 /* synopsis: if (r[P1]++)==0 ) goto P2        */
+#define OP_AggStep0      143 /* synopsis: accum=r[P3] step(r[P2@P5])       */
+#define OP_AggStep       144 /* synopsis: accum=r[P3] step(r[P2@P5])       */
+#define OP_AggFinal      145 /* synopsis: accum=r[P1] N=P2                 */
+#define OP_IncrVacuum    146
+#define OP_Expire        147
+#define OP_TableLock     148 /* synopsis: iDb=P1 root=P2 write=P3          */
+#define OP_VBegin        149
+#define OP_VCreate       150
+#define OP_VDestroy      151
+#define OP_VOpen         152
+#define OP_VColumn       153 /* synopsis: r[P3]=vcolumn(P2)                */
+#define OP_VNext         154
+#define OP_VRename       155
+#define OP_Pagecount     156
+#define OP_MaxPgcnt      157
+#define OP_Init          158 /* synopsis: Start at P2                      */
+#define OP_Noop          159
+#define OP_Explain       160
 
 
 /* Properties such as "out2" or "jump" that are specified in
@@ -9952,26 +10019,27 @@ typedef struct VdbeOpList VdbeOpList;
 #define OPFLG_OUT2            0x0010  /* out2:  P2 is an output */
 #define OPFLG_OUT3            0x0020  /* out3:  P3 is an output */
 #define OPFLG_INITIALIZER {\
-/*   0 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01,\
-/*   8 */ 0x01, 0x01, 0x00, 0x00, 0x10, 0x00, 0x01, 0x00,\
-/*  16 */ 0x01, 0x01, 0x02, 0x12, 0x01, 0x02, 0x03, 0x08,\
-/*  24 */ 0x00, 0x10, 0x10, 0x10, 0x10, 0x00, 0x10, 0x10,\
-/*  32 */ 0x00, 0x00, 0x10, 0x00, 0x00, 0x02, 0x03, 0x02,\
+/*   0 */ 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x01,\
+/*   8 */ 0x01, 0x00, 0x10, 0x00, 0x01, 0x00, 0x01, 0x01,\
+/*  16 */ 0x02, 0x01, 0x02, 0x12, 0x03, 0x08, 0x00, 0x10,\
+/*  24 */ 0x10, 0x10, 0x10, 0x00, 0x10, 0x10, 0x00, 0x00,\
+/*  32 */ 0x10, 0x00, 0x00, 0x00, 0x00, 0x02, 0x03, 0x02,\
 /*  40 */ 0x02, 0x00, 0x00, 0x01, 0x01, 0x03, 0x03, 0x00,\
 /*  48 */ 0x00, 0x00, 0x10, 0x10, 0x08, 0x00, 0x00, 0x00,\
-/*  56 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x09, 0x09,\
-/*  64 */ 0x09, 0x09, 0x04, 0x09, 0x09, 0x09, 0x09, 0x26,\
-/*  72 */ 0x26, 0x10, 0x10, 0x00, 0x03, 0x03, 0x0b, 0x0b,\
+/*  56 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x09,\
+/*  64 */ 0x09, 0x09, 0x09, 0x04, 0x09, 0x09, 0x09, 0x26,\
+/*  72 */ 0x26, 0x09, 0x10, 0x10, 0x03, 0x03, 0x0b, 0x0b,\
 /*  80 */ 0x0b, 0x0b, 0x0b, 0x0b, 0x00, 0x26, 0x26, 0x26,\
 /*  88 */ 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x00,\
-/*  96 */ 0x12, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10,\
-/* 104 */ 0x00, 0x01, 0x01, 0x01, 0x01, 0x04, 0x04, 0x00,\
-/* 112 */ 0x10, 0x01, 0x01, 0x01, 0x01, 0x10, 0x00, 0x00,\
-/* 120 */ 0x10, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
-/* 128 */ 0x06, 0x23, 0x0b, 0x01, 0x10, 0x10, 0x00, 0x01,\
-/* 136 */ 0x04, 0x03, 0x03, 0x03, 0x03, 0x03, 0x00, 0x01,\
-/* 144 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,\
-/* 152 */ 0x00, 0x10, 0x10, 0x01, 0x00, 0x00,}
+/*  96 */ 0x12, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 104 */ 0x10, 0x00, 0x01, 0x01, 0x01, 0x01, 0x04, 0x04,\
+/* 112 */ 0x00, 0x10, 0x01, 0x01, 0x01, 0x01, 0x10, 0x00,\
+/* 120 */ 0x00, 0x10, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 128 */ 0x00, 0x06, 0x23, 0x0b, 0x01, 0x10, 0x10, 0x00,\
+/* 136 */ 0x01, 0x04, 0x03, 0x03, 0x03, 0x03, 0x03, 0x00,\
+/* 144 */ 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,\
+/* 152 */ 0x00, 0x00, 0x01, 0x00, 0x10, 0x10, 0x01, 0x00,\
+/* 160 */ 0x00,}
 
 /************** End of opcodes.h *********************************************/
 /************** Continuing where we left off in vdbe.h ***********************/
@@ -9986,6 +10054,7 @@ SQLITE_PRIVATE int sqlite3VdbeAddOp1(Vdbe*,int,int);
 SQLITE_PRIVATE int sqlite3VdbeAddOp2(Vdbe*,int,int,int);
 SQLITE_PRIVATE int sqlite3VdbeAddOp3(Vdbe*,int,int,int,int);
 SQLITE_PRIVATE int sqlite3VdbeAddOp4(Vdbe*,int,int,int,int,const char *zP4,int);
+SQLITE_PRIVATE int sqlite3VdbeAddOp4Dup8(Vdbe*,int,int,int,int,const u8*,int);
 SQLITE_PRIVATE int sqlite3VdbeAddOp4Int(Vdbe*,int,int,int,int,int);
 SQLITE_PRIVATE int sqlite3VdbeAddOpList(Vdbe*, int nOp, VdbeOpList const *aOp, int iLineno);
 SQLITE_PRIVATE void sqlite3VdbeAddParseSchemaOp(Vdbe*,int,char*);
@@ -10287,7 +10356,9 @@ SQLITE_PRIVATE   int sqlite3PagerWalFramesize(Pager *pPager);
 /* Functions used to query pager state and configuration. */
 SQLITE_PRIVATE u8 sqlite3PagerIsreadonly(Pager*);
 SQLITE_PRIVATE u32 sqlite3PagerDataVersion(Pager*);
-SQLITE_PRIVATE int sqlite3PagerRefcount(Pager*);
+#ifdef SQLITE_DEBUG
+SQLITE_PRIVATE   int sqlite3PagerRefcount(Pager*);
+#endif
 SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager*);
 SQLITE_PRIVATE const char *sqlite3PagerFilename(Pager*, int);
 SQLITE_PRIVATE const sqlite3_vfs *sqlite3PagerVfs(Pager*);
@@ -10378,14 +10449,14 @@ struct PgHdr {
 };
 
 /* Bit values for PgHdr.flags */
-#define PGHDR_DIRTY             0x002  /* Page has changed */
-#define PGHDR_NEED_SYNC         0x004  /* Fsync the rollback journal before
-                                       ** writing this page to the database */
-#define PGHDR_NEED_READ         0x008  /* Content is unread */
-#define PGHDR_REUSE_UNLIKELY    0x010  /* A hint that reuse is unlikely */
-#define PGHDR_DONT_WRITE        0x020  /* Do not write content to disk */
-
-#define PGHDR_MMAP              0x040  /* This is an mmap page object */
+#define PGHDR_CLEAN           0x001  /* Page not on the PCache.pDirty list */
+#define PGHDR_DIRTY           0x002  /* Page is on the PCache.pDirty list */
+#define PGHDR_WRITEABLE       0x004  /* Journaled and ready to modify */
+#define PGHDR_NEED_SYNC       0x008  /* Fsync the rollback journal before
+                                     ** writing this page to the database */
+#define PGHDR_NEED_READ       0x010  /* Content is unread */
+#define PGHDR_DONT_WRITE      0x020  /* Do not write content to disk */
+#define PGHDR_MMAP            0x040  /* This is an mmap page object */
 
 /* Initialize and shutdown the page cache subsystem */
 SQLITE_PRIVATE int sqlite3PcacheInitialize(void);
@@ -11169,6 +11240,7 @@ struct sqlite3 {
 #define SQLITE_QueryOnly      0x02000000  /* Disable database changes */
 #define SQLITE_VdbeEQP        0x04000000  /* Debug EXPLAIN QUERY PLAN */
 #define SQLITE_Vacuum         0x08000000  /* Currently in a VACUUM */
+#define SQLITE_CellSizeCk     0x10000000  /* Check btree cell sizes on load */
 
 
 /*
@@ -11416,9 +11488,9 @@ struct CollSeq {
 ** used as the P4 operand, they will be more readable.
 **
 ** Note also that the numeric types are grouped together so that testing
-** for a numeric type is a single comparison.  And the NONE type is first.
+** for a numeric type is a single comparison.  And the BLOB type is first.
 */
-#define SQLITE_AFF_NONE     'A'
+#define SQLITE_AFF_BLOB     'A'
 #define SQLITE_AFF_TEXT     'B'
 #define SQLITE_AFF_NUMERIC  'C'
 #define SQLITE_AFF_INTEGER  'D'
@@ -11550,8 +11622,9 @@ struct Table {
 #define TF_HasPrimaryKey   0x04    /* Table has a primary key */
 #define TF_Autoincrement   0x08    /* Integer primary key is autoincrement */
 #define TF_Virtual         0x10    /* Is a virtual table */
-#define TF_WithoutRowid    0x20    /* No rowid used. PRIMARY KEY is the key */
-#define TF_OOOHidden       0x40    /* Out-of-Order hidden columns */
+#define TF_WithoutRowid    0x20    /* No rowid.  PRIMARY KEY is the key */
+#define TF_NoVisibleRowid  0x40    /* No user-visible "rowid" column */
+#define TF_OOOHidden       0x80    /* Out-of-Order hidden columns */
 
 
 /*
@@ -11569,6 +11642,7 @@ struct Table {
 
 /* Does the table have a rowid */
 #define HasRowid(X)     (((X)->tabFlags & TF_WithoutRowid)==0)
+#define VisibleRowid(X) (((X)->tabFlags & TF_NoVisibleRowid)==0)
 
 /*
 ** Each foreign key constraint is an instance of the following structure.
@@ -11727,6 +11801,14 @@ struct UnpackedRecord {
 ** and the value of Index.onError indicate the which conflict resolution 
 ** algorithm to employ whenever an attempt is made to insert a non-unique
 ** element.
+**
+** While parsing a CREATE TABLE or CREATE INDEX statement in order to
+** generate VDBE code (as opposed to parsing one read from an sqlite_master
+** table as part of parsing an existing database schema), transient instances
+** of this structure may be created. In this case the Index.tnum variable is
+** used to store the address of a VDBE instruction, not a database page
+** number (it cannot - the database page is not allocated until the VDBE
+** program is executed). See convertToWithoutRowidTable() for details.
 */
 struct Index {
   char *zName;             /* Name of this index */
@@ -12165,7 +12247,7 @@ struct SrcList {
     Expr *pOn;        /* The ON clause of a join */
     IdList *pUsing;   /* The USING clause of a join */
     Bitmask colUsed;  /* Bit N (1<<N) set if column N of pTab is used */
-    char *zIndex;     /* Identifier from "INDEXED BY <zIndex>" clause */
+    char *zIndexedBy; /* Identifier from "INDEXED BY <zIndex>" clause */
     Index *pIndex;    /* Index structure corresponding to zIndex, if any */
   } a[1];             /* One entry for each identifier on the list */
 };
@@ -12301,19 +12383,20 @@ struct Select {
 ** "Select Flag".
 */
 #define SF_Distinct        0x0001  /* Output should be DISTINCT */
-#define SF_Resolved        0x0002  /* Identifiers have been resolved */
-#define SF_Aggregate       0x0004  /* Contains aggregate functions */
-#define SF_UsesEphemeral   0x0008  /* Uses the OpenEphemeral opcode */
-#define SF_Expanded        0x0010  /* sqlite3SelectExpand() called on this */
-#define SF_HasTypeInfo     0x0020  /* FROM subqueries have Table metadata */
-#define SF_Compound        0x0040  /* Part of a compound query */
-#define SF_Values          0x0080  /* Synthesized from VALUES clause */
-#define SF_MultiValue      0x0100  /* Single VALUES term with multiple rows */
-#define SF_NestedFrom      0x0200  /* Part of a parenthesized FROM clause */
-#define SF_MaybeConvert    0x0400  /* Need convertCompoundSelectToSubquery() */
-#define SF_Recursive       0x0800  /* The recursive part of a recursive CTE */
+#define SF_All             0x0002  /* Includes the ALL keyword */
+#define SF_Resolved        0x0004  /* Identifiers have been resolved */
+#define SF_Aggregate       0x0008  /* Contains aggregate functions */
+#define SF_UsesEphemeral   0x0010  /* Uses the OpenEphemeral opcode */
+#define SF_Expanded        0x0020  /* sqlite3SelectExpand() called on this */
+#define SF_HasTypeInfo     0x0040  /* FROM subqueries have Table metadata */
+#define SF_Compound        0x0080  /* Part of a compound query */
+#define SF_Values          0x0100  /* Synthesized from VALUES clause */
+#define SF_MultiValue      0x0200  /* Single VALUES term with multiple rows */
+#define SF_NestedFrom      0x0400  /* Part of a parenthesized FROM clause */
+#define SF_MaybeConvert    0x0800  /* Need convertCompoundSelectToSubquery() */
 #define SF_MinMaxAgg       0x1000  /* Aggregate containing min() or max() */
-#define SF_Converted       0x2000  /* By convertCompoundSelectToSubquery() */
+#define SF_Recursive       0x2000  /* The recursive part of a recursive CTE */
+#define SF_Converted       0x4000  /* By convertCompoundSelectToSubquery() */
 
 
 /*
@@ -12555,7 +12638,6 @@ struct Parse {
   Parse *pToplevel;    /* Parse structure for main program (or NULL) */
   Table *pTriggerTab;  /* Table triggers are being coded for */
   int addrCrTab;       /* Address of OP_CreateTable opcode on CREATE TABLE */
-  int addrSkipPK;      /* Address of instruction to skip PRIMARY KEY index */
   u32 nQueryLoop;      /* Est number of iterations of a query (10*log2(N)) */
   u32 oldmask;         /* Mask of old.* columns referenced */
   u32 newmask;         /* Mask of new.* columns referenced */
@@ -12971,7 +13053,9 @@ SQLITE_PRIVATE int sqlite3CantopenError(int);
 # define sqlite3Isxdigit(x)  isxdigit((unsigned char)(x))
 # define sqlite3Tolower(x)   tolower((unsigned char)(x))
 #endif
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
 SQLITE_PRIVATE int sqlite3IsIdChar(u8);
+#endif
 
 /*
 ** Internal function prototypes
@@ -12999,7 +13083,9 @@ SQLITE_PRIVATE void sqlite3ScratchFree(void*);
 SQLITE_PRIVATE void *sqlite3PageMalloc(int);
 SQLITE_PRIVATE void sqlite3PageFree(void*);
 SQLITE_PRIVATE void sqlite3MemSetDefault(void);
+#ifndef SQLITE_OMIT_BUILTIN_TEST
 SQLITE_PRIVATE void sqlite3BenignMallocHooks(void (*)(void), void (*)(void));
+#endif
 SQLITE_PRIVATE int sqlite3HeapNearlyFull(void);
 
 /*
@@ -13067,7 +13153,6 @@ SQLITE_PRIVATE void sqlite3VXPrintf(StrAccum*, u32, const char*, va_list);
 SQLITE_PRIVATE void sqlite3XPrintf(StrAccum*, u32, const char*, ...);
 SQLITE_PRIVATE char *sqlite3MPrintf(sqlite3*,const char*, ...);
 SQLITE_PRIVATE char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
-SQLITE_PRIVATE char *sqlite3MAppendf(sqlite3*,char*,const char*,...);
 #if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
 SQLITE_PRIVATE   void sqlite3DebugPrintf(const char*, ...);
 #endif
@@ -13076,17 +13161,13 @@ SQLITE_PRIVATE   void *sqlite3TestTextToPtr(const char*);
 #endif
 
 #if defined(SQLITE_DEBUG)
-SQLITE_PRIVATE   TreeView *sqlite3TreeViewPush(TreeView*,u8);
-SQLITE_PRIVATE   void sqlite3TreeViewPop(TreeView*);
-SQLITE_PRIVATE   void sqlite3TreeViewLine(TreeView*, const char*, ...);
-SQLITE_PRIVATE   void sqlite3TreeViewItem(TreeView*, const char*, u8);
 SQLITE_PRIVATE   void sqlite3TreeViewExpr(TreeView*, const Expr*, u8);
 SQLITE_PRIVATE   void sqlite3TreeViewExprList(TreeView*, const ExprList*, u8, const char*);
 SQLITE_PRIVATE   void sqlite3TreeViewSelect(TreeView*, const Select*, u8);
 #endif
 
 
-SQLITE_PRIVATE void sqlite3SetString(char **, sqlite3*, const char*, ...);
+SQLITE_PRIVATE void sqlite3SetString(char **, sqlite3*, const char*);
 SQLITE_PRIVATE void sqlite3ErrorMsg(Parse*, const char*, ...);
 SQLITE_PRIVATE int sqlite3Dequote(char*);
 SQLITE_PRIVATE int sqlite3KeywordCode(const unsigned char*, int);
@@ -13144,11 +13225,14 @@ SQLITE_PRIVATE   int sqlite3FaultSim(int);
 
 SQLITE_PRIVATE Bitvec *sqlite3BitvecCreate(u32);
 SQLITE_PRIVATE int sqlite3BitvecTest(Bitvec*, u32);
+SQLITE_PRIVATE int sqlite3BitvecTestNotNull(Bitvec*, u32);
 SQLITE_PRIVATE int sqlite3BitvecSet(Bitvec*, u32);
 SQLITE_PRIVATE void sqlite3BitvecClear(Bitvec*, u32, void*);
 SQLITE_PRIVATE void sqlite3BitvecDestroy(Bitvec*);
 SQLITE_PRIVATE u32 sqlite3BitvecSize(Bitvec*);
+#ifndef SQLITE_OMIT_BUILTIN_TEST
 SQLITE_PRIVATE int sqlite3BitvecBuiltinTest(int,int*);
+#endif
 
 SQLITE_PRIVATE RowSet *sqlite3RowSetInit(sqlite3*, void*, unsigned int);
 SQLITE_PRIVATE void sqlite3RowSetClear(RowSet*);
@@ -13236,6 +13320,7 @@ SQLITE_PRIVATE int sqlite3ExprCodeExprList(Parse*, ExprList*, int, u8);
 #define SQLITE_ECEL_FACTOR   0x02  /* Factor out constant terms */
 SQLITE_PRIVATE void sqlite3ExprIfTrue(Parse*, Expr*, int, int);
 SQLITE_PRIVATE void sqlite3ExprIfFalse(Parse*, Expr*, int, int);
+SQLITE_PRIVATE void sqlite3ExprIfFalseDup(Parse*, Expr*, int, int);
 SQLITE_PRIVATE Table *sqlite3FindTable(sqlite3*,const char*, const char*);
 SQLITE_PRIVATE Table *sqlite3LocateTable(Parse*,int isView,const char*, const char*);
 SQLITE_PRIVATE Table *sqlite3LocateTableItem(Parse*,int isView,struct SrcList_item *);
@@ -13252,8 +13337,10 @@ SQLITE_PRIVATE void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
 SQLITE_PRIVATE void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
 SQLITE_PRIVATE int sqlite3FunctionUsesThisSrc(Expr*, SrcList*);
 SQLITE_PRIVATE Vdbe *sqlite3GetVdbe(Parse*);
+#ifndef SQLITE_OMIT_BUILTIN_TEST
 SQLITE_PRIVATE void sqlite3PrngSaveState(void);
 SQLITE_PRIVATE void sqlite3PrngRestoreState(void);
+#endif
 SQLITE_PRIVATE void sqlite3RollbackAll(sqlite3*,int);
 SQLITE_PRIVATE void sqlite3CodeVerifySchema(Parse*, int);
 SQLITE_PRIVATE void sqlite3CodeVerifyNamedSchema(Parse*, const char *zDb);
@@ -13471,6 +13558,7 @@ SQLITE_PRIVATE void sqlite3NestedParse(Parse*, const char*, ...);
 SQLITE_PRIVATE void sqlite3ExpirePreparedStatements(sqlite3*);
 SQLITE_PRIVATE int sqlite3CodeSubselect(Parse *, Expr *, int, int);
 SQLITE_PRIVATE void sqlite3SelectPrep(Parse*, Select*, NameContext*);
+SQLITE_PRIVATE void sqlite3SelectWrongNumTermsError(Parse *pParse, Select *p);
 SQLITE_PRIVATE int sqlite3MatchSpanName(const char*, const char*, const char*, const char*);
 SQLITE_PRIVATE int sqlite3ResolveExprNames(NameContext*, Expr*);
 SQLITE_PRIVATE void sqlite3ResolveSelectNames(Parse*, Select*, NameContext*);
@@ -13783,6 +13871,10 @@ SQLITE_PRIVATE int sqlite3ThreadCreate(SQLiteThread**,void*(*)(void*),void*);
 SQLITE_PRIVATE int sqlite3ThreadJoin(SQLiteThread*, void**);
 #endif
 
+#if defined(SQLITE_ENABLE_DBSTAT_VTAB) || defined(SQLITE_TEST)
+SQLITE_PRIVATE int sqlite3DbstatRegister(sqlite3*);
+#endif
+
 #endif /* _SQLITEINT_H_ */
 
 /************** End of sqliteInt.h *******************************************/
@@ -13801,6 +13893,7 @@ SQLITE_PRIVATE int sqlite3ThreadJoin(SQLiteThread*, void**);
 **
 ** This file contains definitions of global variables and constants.
 */
+/* #include "sqliteInt.h" */
 
 /* An array to map all upper-case characters into their corresponding
 ** lower-case character. 
@@ -13974,7 +14067,7 @@ SQLITE_PRIVATE SQLITE_WSD struct Sqlite3Config sqlite3Config = {
    0,                         /* nScratch */
    (void*)0,                  /* pPage */
    0,                         /* szPage */
-   0,                         /* nPage */
+   SQLITE_DEFAULT_PCACHE_INITSZ, /* nPage */
    0,                         /* mxParserStack */
    0,                         /* sharedCacheEnabled */
    SQLITE_SORTER_PMASZ,       /* szPma */
@@ -14040,6 +14133,7 @@ SQLITE_PRIVATE const Token sqlite3IntTokens[] = {
 SQLITE_PRIVATE int sqlite3PendingByte = 0x40000000;
 #endif
 
+/* #include "opcodes.h" */
 /*
 ** Properties of opcodes.  The OPFLG_INITIALIZER macro is
 ** created by mkopcodeh.awk during compilation.  Data is obtained
@@ -14068,6 +14162,7 @@ SQLITE_PRIVATE const unsigned char sqlite3OpcodeProperty[] = OPFLG_INITIALIZER;
 
 #ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
 
+/* #include "sqliteInt.h" */
 
 /*
 ** An array of names of all compile-time options.  This array should 
@@ -14497,6 +14592,7 @@ SQLITE_API const char *SQLITE_STDCALL sqlite3_compileoption_get(int N){
 ** This module implements the sqlite3_status() interface and related
 ** functionality.
 */
+/* #include "sqliteInt.h" */
 /************** Include vdbeInt.h in the middle of status.c ******************/
 /************** Begin file vdbeInt.h *****************************************/
 /*
@@ -14584,6 +14680,9 @@ struct VdbeCursor {
   i64 seqCount;         /* Sequence counter */
   i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */
   VdbeSorter *pSorter;  /* Sorter object for OP_SorterOpen cursors */
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+  u64 maskUsed;         /* Mask of columns used by this cursor */
+#endif
 
   /* Cached information about the header for the data record that the
   ** cursor is currently pointing to.  Only valid if cacheStatus matches
@@ -14687,6 +14786,12 @@ struct Mem {
 #endif
 };
 
+/*
+** Size of struct Mem not including the Mem.zMalloc member or anything that
+** follows.
+*/
+#define MEMCELLSIZE offsetof(Mem,zMalloc)
+
 /* One or more of the following flags are set to indicate the validOK
 ** representations of the value stored in the Mem struct.
 **
@@ -14771,14 +14876,16 @@ struct AuxData {
 ** (Mem) which are only defined there.
 */
 struct sqlite3_context {
-  Mem *pOut;            /* The return value is stored here */
-  FuncDef *pFunc;       /* Pointer to function information */
-  Mem *pMem;            /* Memory cell used to store aggregate context */
-  Vdbe *pVdbe;          /* The VM that owns this context */
-  int iOp;              /* Instruction number of OP_Function */
-  int isError;          /* Error code returned by the function. */
-  u8 skipFlag;          /* Skip accumulator loading if true */
-  u8 fErrorOrAux;       /* isError!=0 or pVdbe->pAuxData modified */
+  Mem *pOut;              /* The return value is stored here */
+  FuncDef *pFunc;         /* Pointer to function information */
+  Mem *pMem;              /* Memory cell used to store aggregate context */
+  Vdbe *pVdbe;            /* The VM that owns this context */
+  int iOp;                /* Instruction number of OP_Function */
+  int isError;            /* Error code returned by the function. */
+  u8 skipFlag;            /* Skip accumulator loading if true */
+  u8 fErrorOrAux;         /* isError!=0 or pVdbe->pAuxData modified */
+  u8 argc;                /* Number of arguments */
+  sqlite3_value *argv[1]; /* Argument set */
 };
 
 /*
@@ -14892,6 +14999,7 @@ struct Vdbe {
 /*
 ** Function prototypes
 */
+SQLITE_PRIVATE void sqlite3VdbeError(Vdbe*, const char *, ...);
 SQLITE_PRIVATE void sqlite3VdbeFreeCursor(Vdbe *, VdbeCursor*);
 void sqliteVdbePopStack(Vdbe*,int);
 SQLITE_PRIVATE int sqlite3VdbeCursorMoveto(VdbeCursor*);
@@ -15368,6 +15476,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_db_status(
 **      Willmann-Bell, Inc
 **      Richmond, Virginia (USA)
 */
+/* #include "sqliteInt.h" */
 /* #include <stdlib.h> */
 /* #include <assert.h> */
 #include <time.h>
@@ -15679,7 +15788,7 @@ static void computeYMD(DateTime *p){
     A = Z + 1 + A - (A/4);
     B = A + 1524;
     C = (int)((B - 122.1)/365.25);
-    D = (36525*C)/100;
+    D = (36525*(C&32767))/100;
     E = (int)((B-D)/30.6001);
     X1 = (int)(30.6001*E);
     p->D = B - D - X1;
@@ -16480,6 +16589,7 @@ SQLITE_PRIVATE void sqlite3RegisterDateTimeFunctions(void){
 ** architectures.
 */
 #define _SQLITE_OS_C_ 1
+/* #include "sqliteInt.h" */
 #undef _SQLITE_OS_C_
 
 /*
@@ -16886,6 +16996,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_vfs_unregister(sqlite3_vfs *pVfs){
 ** during a hash table resize is a benign fault.
 */
 
+/* #include "sqliteInt.h" */
 
 #ifndef SQLITE_OMIT_BUILTIN_TEST
 
@@ -16967,6 +17078,7 @@ SQLITE_PRIVATE void sqlite3EndBenignMalloc(void){
 ** are merely placeholders.  Real drivers must be substituted using
 ** sqlite3_config() before SQLite will operate.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** This version of the memory allocator is the default.  It is
@@ -17053,6 +17165,7 @@ SQLITE_PRIVATE void sqlite3MemSetDefault(void){
 **                                be necessary when compiling for Delphi,
 **                                for example.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** This version of the memory allocator is the default.  It is
@@ -17328,6 +17441,7 @@ SQLITE_PRIVATE void sqlite3MemSetDefault(void){
 ** This file contains implementations of the low-level memory allocation
 ** routines specified in the sqlite3_mem_methods object.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** This version of the memory allocator is used only if the
@@ -17862,6 +17976,7 @@ SQLITE_PRIVATE int sqlite3MemdebugMallocCount(){
 ** This version of the memory allocation subsystem is included
 ** in the build only if SQLITE_ENABLE_MEMSYS3 is defined.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** This version of the memory allocator is only built into the library
@@ -18576,6 +18691,7 @@ SQLITE_PRIVATE const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){
 ** The sqlite3_status() logic tracks the maximum values of n and M so
 ** that an application can, at any time, verify this constraint.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** This version of the memory allocator is used only when 
@@ -19119,6 +19235,7 @@ SQLITE_PRIVATE const sqlite3_mem_methods *sqlite3MemGetMemsys5(void){
 **
 ** This file contains code that is common across all mutex implementations.
 */
+/* #include "sqliteInt.h" */
 
 #if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT)
 /*
@@ -19150,9 +19267,14 @@ SQLITE_PRIVATE int sqlite3MutexInit(void){
     }else{
       pFrom = sqlite3NoopMutex();
     }
-    memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc));
-    memcpy(&pTo->xMutexFree, &pFrom->xMutexFree,
-           sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree));
+    pTo->xMutexInit = pFrom->xMutexInit;
+    pTo->xMutexEnd = pFrom->xMutexEnd;
+    pTo->xMutexFree = pFrom->xMutexFree;
+    pTo->xMutexEnter = pFrom->xMutexEnter;
+    pTo->xMutexTry = pFrom->xMutexTry;
+    pTo->xMutexLeave = pFrom->xMutexLeave;
+    pTo->xMutexHeld = pFrom->xMutexHeld;
+    pTo->xMutexNotheld = pFrom->xMutexNotheld;
     pTo->xMutexAlloc = pFrom->xMutexAlloc;
   }
   rc = sqlite3GlobalConfig.mutex.xMutexInit();
@@ -19287,6 +19409,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_mutex_notheld(sqlite3_mutex *p){
 ** that does error checking on mutexes to make sure they are being
 ** called correctly.
 */
+/* #include "sqliteInt.h" */
 
 #ifndef SQLITE_MUTEX_OMIT
 
@@ -19368,7 +19491,7 @@ static int debugMutexEnd(void){ return SQLITE_OK; }
 ** that means that a mutex could not be allocated. 
 */
 static sqlite3_mutex *debugMutexAlloc(int id){
-  static sqlite3_debug_mutex aStatic[SQLITE_MUTEX_STATIC_APP3 - 1];
+  static sqlite3_debug_mutex aStatic[SQLITE_MUTEX_STATIC_VFS3 - 1];
   sqlite3_debug_mutex *pNew = 0;
   switch( id ){
     case SQLITE_MUTEX_FAST:
@@ -19490,6 +19613,7 @@ SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
 *************************************************************************
 ** This file contains the C functions that implement mutexes for pthreads
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** The code in this file is only used if we are compiling threadsafe
@@ -19583,6 +19707,9 @@ static int pthreadMutexEnd(void){ return SQLITE_OK; }
 ** <li>  SQLITE_MUTEX_STATIC_APP1
 ** <li>  SQLITE_MUTEX_STATIC_APP2
 ** <li>  SQLITE_MUTEX_STATIC_APP3
+** <li>  SQLITE_MUTEX_STATIC_VFS1
+** <li>  SQLITE_MUTEX_STATIC_VFS2
+** <li>  SQLITE_MUTEX_STATIC_VFS3
 ** </ul>
 **
 ** The first two constants cause sqlite3_mutex_alloc() to create
@@ -19619,6 +19746,9 @@ static sqlite3_mutex *pthreadMutexAlloc(int iType){
     SQLITE3_MUTEX_INITIALIZER,
     SQLITE3_MUTEX_INITIALIZER,
     SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
+    SQLITE3_MUTEX_INITIALIZER,
     SQLITE3_MUTEX_INITIALIZER
   };
   sqlite3_mutex *p;
@@ -19858,6 +19988,7 @@ SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
 *************************************************************************
 ** This file contains the C functions that implement mutexes for Win32.
 */
+/* #include "sqliteInt.h" */
 
 #if SQLITE_OS_WIN
 /*
@@ -20225,6 +20356,9 @@ static sqlite3_mutex winMutex_staticMutexes[] = {
   SQLITE3_MUTEX_INITIALIZER,
   SQLITE3_MUTEX_INITIALIZER,
   SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
+  SQLITE3_MUTEX_INITIALIZER,
   SQLITE3_MUTEX_INITIALIZER
 };
 
@@ -20296,6 +20430,9 @@ static int winMutexEnd(void){
 ** <li>  SQLITE_MUTEX_STATIC_APP1
 ** <li>  SQLITE_MUTEX_STATIC_APP2
 ** <li>  SQLITE_MUTEX_STATIC_APP3
+** <li>  SQLITE_MUTEX_STATIC_VFS1
+** <li>  SQLITE_MUTEX_STATIC_VFS2
+** <li>  SQLITE_MUTEX_STATIC_VFS3
 ** </ul>
 **
 ** The first two constants cause sqlite3_mutex_alloc() to create
@@ -20527,6 +20664,7 @@ SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
 **
 ** Memory allocation functions used throughout sqlite.
 */
+/* #include "sqliteInt.h" */
 /* #include <stdarg.h> */
 
 /*
@@ -20707,10 +20845,9 @@ SQLITE_PRIVATE int sqlite3MallocInit(void){
     sqlite3GlobalConfig.nScratch = 0;
   }
   if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
-      || sqlite3GlobalConfig.nPage<1 ){
+      || sqlite3GlobalConfig.nPage<=0 ){
     sqlite3GlobalConfig.pPage = 0;
     sqlite3GlobalConfig.szPage = 0;
-    sqlite3GlobalConfig.nPage = 0;
   }
   rc = sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
   if( rc!=SQLITE_OK ) memset(&mem0, 0, sizeof(mem0));
@@ -20740,10 +20877,8 @@ SQLITE_PRIVATE void sqlite3MallocEnd(void){
 ** Return the amount of memory currently checked out.
 */
 SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3_memory_used(void){
-  int n, mx;
-  sqlite3_int64 res;
-  sqlite3_status(SQLITE_STATUS_MEMORY_USED, &n, &mx, 0);
-  res = (sqlite3_int64)n;  /* Work around bug in Borland C. Ticket #3216 */
+  sqlite3_int64 res, mx;
+  sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, 0);
   return res;
 }
 
@@ -20753,11 +20888,9 @@ SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3_memory_used(void){
 ** or since the most recent reset.
 */
 SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3_memory_highwater(int resetFlag){
-  int n, mx;
-  sqlite3_int64 res;
-  sqlite3_status(SQLITE_STATUS_MEMORY_USED, &n, &mx, resetFlag);
-  res = (sqlite3_int64)mx;  /* Work around bug in Borland C. Ticket #3216 */
-  return res;
+  sqlite3_int64 res, mx;
+  sqlite3_status64(SQLITE_STATUS_MEMORY_USED, &res, &mx, resetFlag);
+  return mx;
 }
 
 /*
@@ -21289,19 +21422,11 @@ SQLITE_PRIVATE char *sqlite3DbStrNDup(sqlite3 *db, const char *z, u64 n){
 }
 
 /*
-** Create a string from the zFromat argument and the va_list that follows.
-** Store the string in memory obtained from sqliteMalloc() and make *pz
-** point to that string.
+** Free any prior content in *pz and replace it with a copy of zNew.
 */
-SQLITE_PRIVATE void sqlite3SetString(char **pz, sqlite3 *db, const char *zFormat, ...){
-  va_list ap;
-  char *z;
-
-  va_start(ap, zFormat);
-  z = sqlite3VMPrintf(db, zFormat, ap);
-  va_end(ap);
+SQLITE_PRIVATE void sqlite3SetString(char **pz, sqlite3 *db, const char *zNew){
   sqlite3DbFree(db, *pz);
-  *pz = z;
+  *pz = sqlite3DbStrDup(db, zNew);
 }
 
 /*
@@ -21322,17 +21447,16 @@ static SQLITE_NOINLINE int apiOomError(sqlite3 *db){
 ** function. However, if a malloc() failure has occurred since the previous
 ** invocation SQLITE_NOMEM is returned instead. 
 **
-** If the first argument, db, is not NULL and a malloc() error has occurred,
-** then the connection error-code (the value returned by sqlite3_errcode())
-** is set to SQLITE_NOMEM.
+** If an OOM as occurred, then the connection error-code (the value
+** returned by sqlite3_errcode()) is set to SQLITE_NOMEM.
 */
 SQLITE_PRIVATE int sqlite3ApiExit(sqlite3* db, int rc){
-  /* If the db handle is not NULL, then we must hold the connection handle
-  ** mutex here. Otherwise the read (and possible write) of db->mallocFailed 
+  /* If the db handle must hold the connection handle mutex here.
+  ** Otherwise the read (and possible write) of db->mallocFailed 
   ** is unsafe, as is the call to sqlite3Error().
   */
-  assert( !db || sqlite3_mutex_held(db->mutex) );
-  if( db==0 ) return rc & 0xff;
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
   if( db->mallocFailed || rc==SQLITE_IOERR_NOMEM ){
     return apiOomError(db);
   }
@@ -21343,18 +21467,16 @@ SQLITE_PRIVATE int sqlite3ApiExit(sqlite3* db, int rc){
 /************** Begin file printf.c ******************************************/
 /*
 ** The "printf" code that follows dates from the 1980's.  It is in
-** the public domain.  The original comments are included here for
-** completeness.  They are very out-of-date but might be useful as
-** an historical reference.  Most of the "enhancements" have been backed
-** out so that the functionality is now the same as standard printf().
+** the public domain. 
 **
 **************************************************************************
 **
 ** This file contains code for a set of "printf"-like routines.  These
 ** routines format strings much like the printf() from the standard C
 ** library, though the implementation here has enhancements to support
-** SQLlite.
+** SQLite.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** Conversion types fall into various categories as defined by the
@@ -22273,24 +22395,6 @@ SQLITE_PRIVATE char *sqlite3MPrintf(sqlite3 *db, const char *zFormat, ...){
   return z;
 }
 
-/*
-** Like sqlite3MPrintf(), but call sqlite3DbFree() on zStr after formatting
-** the string and before returning.  This routine is intended to be used
-** to modify an existing string.  For example:
-**
-**       x = sqlite3MPrintf(db, x, "prefix %s suffix", x);
-**
-*/
-SQLITE_PRIVATE char *sqlite3MAppendf(sqlite3 *db, char *zStr, const char *zFormat, ...){
-  va_list ap;
-  char *z;
-  va_start(ap, zFormat);
-  z = sqlite3VMPrintf(db, zFormat, ap);
-  va_end(ap);
-  sqlite3DbFree(db, zStr);
-  return z;
-}
-
 /*
 ** Print into memory obtained from sqlite3_malloc().  Omit the internal
 ** %-conversion extensions.
@@ -22375,6 +22479,11 @@ SQLITE_API char *SQLITE_CDECL sqlite3_snprintf(int n, char *zBuf, const char *zF
 ** sqlite3_log() must render into a static buffer.  It cannot dynamically
 ** allocate memory because it might be called while the memory allocator
 ** mutex is held.
+**
+** sqlite3VXPrintf() might ask for *temporary* memory allocations for
+** certain format characters (%q) or for very large precisions or widths.
+** Care must be taken that any sqlite3_log() calls that occur while the
+** memory mutex is held do not use these mechanisms.
 */
 static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
   StrAccum acc;                          /* String accumulator */
@@ -22418,22 +22527,46 @@ SQLITE_PRIVATE void sqlite3DebugPrintf(const char *zFormat, ...){
 }
 #endif
 
-#ifdef SQLITE_DEBUG
-/*************************************************************************
-** Routines for implementing the "TreeView" display of hierarchical
-** data structures for debugging.
+
+/*
+** variable-argument wrapper around sqlite3VXPrintf().
+*/
+SQLITE_PRIVATE void sqlite3XPrintf(StrAccum *p, u32 bFlags, const char *zFormat, ...){
+  va_list ap;
+  va_start(ap,zFormat);
+  sqlite3VXPrintf(p, bFlags, zFormat, ap);
+  va_end(ap);
+}
+
+/************** End of printf.c **********************************************/
+/************** Begin file treeview.c ****************************************/
+/*
+** 2015-06-08
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
 **
-** The main entry points (coded elsewhere) are:
-**     sqlite3TreeViewExpr(0, pExpr, 0);
-**     sqlite3TreeViewExprList(0, pList, 0, 0);
-**     sqlite3TreeViewSelect(0, pSelect, 0);
-** Insert calls to those routines while debugging in order to display
-** a diagram of Expr, ExprList, and Select objects.
+*************************************************************************
 **
+** This file contains C code to implement the TreeView debugging routines.
+** These routines print a parse tree to standard output for debugging and
+** analysis. 
+**
+** The interfaces in this file is only available when compiling
+** with SQLITE_DEBUG.
+*/
+/* #include "sqliteInt.h" */
+#ifdef SQLITE_DEBUG
+
+/*
+** Add a new subitem to the tree.  The moreToFollow flag indicates that this
+** is not the last item in the tree.
 */
-/* Add a new subitem to the tree.  The moreToFollow flag indicates that this
-** is not the last item in the tree. */
-SQLITE_PRIVATE TreeView *sqlite3TreeViewPush(TreeView *p, u8 moreToFollow){
+static TreeView *sqlite3TreeViewPush(TreeView *p, u8 moreToFollow){
   if( p==0 ){
     p = sqlite3_malloc64( sizeof(*p) );
     if( p==0 ) return 0;
@@ -22445,15 +22578,21 @@ SQLITE_PRIVATE TreeView *sqlite3TreeViewPush(TreeView *p, u8 moreToFollow){
   if( p->iLevel<sizeof(p->bLine) ) p->bLine[p->iLevel] = moreToFollow;
   return p;
 }
-/* Finished with one layer of the tree */
-SQLITE_PRIVATE void sqlite3TreeViewPop(TreeView *p){
+
+/*
+** Finished with one layer of the tree
+*/
+static void sqlite3TreeViewPop(TreeView *p){
   if( p==0 ) return;
   p->iLevel--;
   if( p->iLevel<0 ) sqlite3_free(p);
 }
-/* Generate a single line of output for the tree, with a prefix that contains
-** all the appropriate tree lines */
-SQLITE_PRIVATE void sqlite3TreeViewLine(TreeView *p, const char *zFormat, ...){
+
+/*
+** Generate a single line of output for the tree, with a prefix that contains
+** all the appropriate tree lines
+*/
+static void sqlite3TreeViewLine(TreeView *p, const char *zFormat, ...){
   va_list ap;
   int i;
   StrAccum acc;
@@ -22473,24 +22612,367 @@ SQLITE_PRIVATE void sqlite3TreeViewLine(TreeView *p, const char *zFormat, ...){
   fprintf(stdout,"%s", zBuf);
   fflush(stdout);
 }
-/* Shorthand for starting a new tree item that consists of a single label */
-SQLITE_PRIVATE void sqlite3TreeViewItem(TreeView *p, const char *zLabel, u8 moreToFollow){
-  p = sqlite3TreeViewPush(p, moreToFollow);
+
+/*
+** Shorthand for starting a new tree item that consists of a single label
+*/
+static void sqlite3TreeViewItem(TreeView *p, const char *zLabel,u8 moreFollows){
+  p = sqlite3TreeViewPush(p, moreFollows);
   sqlite3TreeViewLine(p, "%s", zLabel);
 }
-#endif /* SQLITE_DEBUG */
+
 
 /*
-** variable-argument wrapper around sqlite3VXPrintf().
+** Generate a human-readable description of a the Select object.
 */
-SQLITE_PRIVATE void sqlite3XPrintf(StrAccum *p, u32 bFlags, const char *zFormat, ...){
-  va_list ap;
-  va_start(ap,zFormat);
-  sqlite3VXPrintf(p, bFlags, zFormat, ap);
-  va_end(ap);
+SQLITE_PRIVATE void sqlite3TreeViewSelect(TreeView *pView, const Select *p, u8 moreToFollow){
+  int n = 0;
+  pView = sqlite3TreeViewPush(pView, moreToFollow);
+  sqlite3TreeViewLine(pView, "SELECT%s%s (0x%p) selFlags=0x%x",
+    ((p->selFlags & SF_Distinct) ? " DISTINCT" : ""),
+    ((p->selFlags & SF_Aggregate) ? " agg_flag" : ""), p, p->selFlags
+  );
+  if( p->pSrc && p->pSrc->nSrc ) n++;
+  if( p->pWhere ) n++;
+  if( p->pGroupBy ) n++;
+  if( p->pHaving ) n++;
+  if( p->pOrderBy ) n++;
+  if( p->pLimit ) n++;
+  if( p->pOffset ) n++;
+  if( p->pPrior ) n++;
+  sqlite3TreeViewExprList(pView, p->pEList, (n--)>0, "result-set");
+  if( p->pSrc && p->pSrc->nSrc ){
+    int i;
+    pView = sqlite3TreeViewPush(pView, (n--)>0);
+    sqlite3TreeViewLine(pView, "FROM");
+    for(i=0; i<p->pSrc->nSrc; i++){
+      struct SrcList_item *pItem = &p->pSrc->a[i];
+      StrAccum x;
+      char zLine[100];
+      sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
+      sqlite3XPrintf(&x, 0, "{%d,*}", pItem->iCursor);
+      if( pItem->zDatabase ){
+        sqlite3XPrintf(&x, 0, " %s.%s", pItem->zDatabase, pItem->zName);
+      }else if( pItem->zName ){
+        sqlite3XPrintf(&x, 0, " %s", pItem->zName);
+      }
+      if( pItem->pTab ){
+        sqlite3XPrintf(&x, 0, " tabname=%Q", pItem->pTab->zName);
+      }
+      if( pItem->zAlias ){
+        sqlite3XPrintf(&x, 0, " (AS %s)", pItem->zAlias);
+      }
+      if( pItem->jointype & JT_LEFT ){
+        sqlite3XPrintf(&x, 0, " LEFT-JOIN");
+      }
+      sqlite3StrAccumFinish(&x);
+      sqlite3TreeViewItem(pView, zLine, i<p->pSrc->nSrc-1); 
+      if( pItem->pSelect ){
+        sqlite3TreeViewSelect(pView, pItem->pSelect, 0);
+      }
+      sqlite3TreeViewPop(pView);
+    }
+    sqlite3TreeViewPop(pView);
+  }
+  if( p->pWhere ){
+    sqlite3TreeViewItem(pView, "WHERE", (n--)>0);
+    sqlite3TreeViewExpr(pView, p->pWhere, 0);
+    sqlite3TreeViewPop(pView);
+  }
+  if( p->pGroupBy ){
+    sqlite3TreeViewExprList(pView, p->pGroupBy, (n--)>0, "GROUPBY");
+  }
+  if( p->pHaving ){
+    sqlite3TreeViewItem(pView, "HAVING", (n--)>0);
+    sqlite3TreeViewExpr(pView, p->pHaving, 0);
+    sqlite3TreeViewPop(pView);
+  }
+  if( p->pOrderBy ){
+    sqlite3TreeViewExprList(pView, p->pOrderBy, (n--)>0, "ORDERBY");
+  }
+  if( p->pLimit ){
+    sqlite3TreeViewItem(pView, "LIMIT", (n--)>0);
+    sqlite3TreeViewExpr(pView, p->pLimit, 0);
+    sqlite3TreeViewPop(pView);
+  }
+  if( p->pOffset ){
+    sqlite3TreeViewItem(pView, "OFFSET", (n--)>0);
+    sqlite3TreeViewExpr(pView, p->pOffset, 0);
+    sqlite3TreeViewPop(pView);
+  }
+  if( p->pPrior ){
+    const char *zOp = "UNION";
+    switch( p->op ){
+      case TK_ALL:         zOp = "UNION ALL";  break;
+      case TK_INTERSECT:   zOp = "INTERSECT";  break;
+      case TK_EXCEPT:      zOp = "EXCEPT";     break;
+    }
+    sqlite3TreeViewItem(pView, zOp, (n--)>0);
+    sqlite3TreeViewSelect(pView, p->pPrior, 0);
+    sqlite3TreeViewPop(pView);
+  }
+  sqlite3TreeViewPop(pView);
 }
 
-/************** End of printf.c **********************************************/
+/*
+** Generate a human-readable explanation of an expression tree.
+*/
+SQLITE_PRIVATE void sqlite3TreeViewExpr(TreeView *pView, const Expr *pExpr, u8 moreToFollow){
+  const char *zBinOp = 0;   /* Binary operator */
+  const char *zUniOp = 0;   /* Unary operator */
+  char zFlgs[30];
+  pView = sqlite3TreeViewPush(pView, moreToFollow);
+  if( pExpr==0 ){
+    sqlite3TreeViewLine(pView, "nil");
+    sqlite3TreeViewPop(pView);
+    return;
+  }
+  if( pExpr->flags ){
+    sqlite3_snprintf(sizeof(zFlgs),zFlgs,"  flags=0x%x",pExpr->flags);
+  }else{
+    zFlgs[0] = 0;
+  }
+  switch( pExpr->op ){
+    case TK_AGG_COLUMN: {
+      sqlite3TreeViewLine(pView, "AGG{%d:%d}%s",
+            pExpr->iTable, pExpr->iColumn, zFlgs);
+      break;
+    }
+    case TK_COLUMN: {
+      if( pExpr->iTable<0 ){
+        /* This only happens when coding check constraints */
+        sqlite3TreeViewLine(pView, "COLUMN(%d)%s", pExpr->iColumn, zFlgs);
+      }else{
+        sqlite3TreeViewLine(pView, "{%d:%d}%s",
+                             pExpr->iTable, pExpr->iColumn, zFlgs);
+      }
+      break;
+    }
+    case TK_INTEGER: {
+      if( pExpr->flags & EP_IntValue ){
+        sqlite3TreeViewLine(pView, "%d", pExpr->u.iValue);
+      }else{
+        sqlite3TreeViewLine(pView, "%s", pExpr->u.zToken);
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_FLOATING_POINT
+    case TK_FLOAT: {
+      sqlite3TreeViewLine(pView,"%s", pExpr->u.zToken);
+      break;
+    }
+#endif
+    case TK_STRING: {
+      sqlite3TreeViewLine(pView,"%Q", pExpr->u.zToken);
+      break;
+    }
+    case TK_NULL: {
+      sqlite3TreeViewLine(pView,"NULL");
+      break;
+    }
+#ifndef SQLITE_OMIT_BLOB_LITERAL
+    case TK_BLOB: {
+      sqlite3TreeViewLine(pView,"%s", pExpr->u.zToken);
+      break;
+    }
+#endif
+    case TK_VARIABLE: {
+      sqlite3TreeViewLine(pView,"VARIABLE(%s,%d)",
+                          pExpr->u.zToken, pExpr->iColumn);
+      break;
+    }
+    case TK_REGISTER: {
+      sqlite3TreeViewLine(pView,"REGISTER(%d)", pExpr->iTable);
+      break;
+    }
+    case TK_AS: {
+      sqlite3TreeViewLine(pView,"AS %Q", pExpr->u.zToken);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+    case TK_ID: {
+      sqlite3TreeViewLine(pView,"ID \"%w\"", pExpr->u.zToken);
+      break;
+    }
+#ifndef SQLITE_OMIT_CAST
+    case TK_CAST: {
+      /* Expressions of the form:   CAST(pLeft AS token) */
+      sqlite3TreeViewLine(pView,"CAST %Q", pExpr->u.zToken);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+#endif /* SQLITE_OMIT_CAST */
+    case TK_LT:      zBinOp = "LT";     break;
+    case TK_LE:      zBinOp = "LE";     break;
+    case TK_GT:      zBinOp = "GT";     break;
+    case TK_GE:      zBinOp = "GE";     break;
+    case TK_NE:      zBinOp = "NE";     break;
+    case TK_EQ:      zBinOp = "EQ";     break;
+    case TK_IS:      zBinOp = "IS";     break;
+    case TK_ISNOT:   zBinOp = "ISNOT";  break;
+    case TK_AND:     zBinOp = "AND";    break;
+    case TK_OR:      zBinOp = "OR";     break;
+    case TK_PLUS:    zBinOp = "ADD";    break;
+    case TK_STAR:    zBinOp = "MUL";    break;
+    case TK_MINUS:   zBinOp = "SUB";    break;
+    case TK_REM:     zBinOp = "REM";    break;
+    case TK_BITAND:  zBinOp = "BITAND"; break;
+    case TK_BITOR:   zBinOp = "BITOR";  break;
+    case TK_SLASH:   zBinOp = "DIV";    break;
+    case TK_LSHIFT:  zBinOp = "LSHIFT"; break;
+    case TK_RSHIFT:  zBinOp = "RSHIFT"; break;
+    case TK_CONCAT:  zBinOp = "CONCAT"; break;
+    case TK_DOT:     zBinOp = "DOT";    break;
+
+    case TK_UMINUS:  zUniOp = "UMINUS"; break;
+    case TK_UPLUS:   zUniOp = "UPLUS";  break;
+    case TK_BITNOT:  zUniOp = "BITNOT"; break;
+    case TK_NOT:     zUniOp = "NOT";    break;
+    case TK_ISNULL:  zUniOp = "ISNULL"; break;
+    case TK_NOTNULL: zUniOp = "NOTNULL"; break;
+
+    case TK_COLLATE: {
+      sqlite3TreeViewLine(pView, "COLLATE %Q", pExpr->u.zToken);
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+      break;
+    }
+
+    case TK_AGG_FUNCTION:
+    case TK_FUNCTION: {
+      ExprList *pFarg;       /* List of function arguments */
+      if( ExprHasProperty(pExpr, EP_TokenOnly) ){
+        pFarg = 0;
+      }else{
+        pFarg = pExpr->x.pList;
+      }
+      if( pExpr->op==TK_AGG_FUNCTION ){
+        sqlite3TreeViewLine(pView, "AGG_FUNCTION%d %Q",
+                             pExpr->op2, pExpr->u.zToken);
+      }else{
+        sqlite3TreeViewLine(pView, "FUNCTION %Q", pExpr->u.zToken);
+      }
+      if( pFarg ){
+        sqlite3TreeViewExprList(pView, pFarg, 0, 0);
+      }
+      break;
+    }
+#ifndef SQLITE_OMIT_SUBQUERY
+    case TK_EXISTS: {
+      sqlite3TreeViewLine(pView, "EXISTS-expr");
+      sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
+      break;
+    }
+    case TK_SELECT: {
+      sqlite3TreeViewLine(pView, "SELECT-expr");
+      sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
+      break;
+    }
+    case TK_IN: {
+      sqlite3TreeViewLine(pView, "IN");
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
+      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
+        sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
+      }else{
+        sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
+      }
+      break;
+    }
+#endif /* SQLITE_OMIT_SUBQUERY */
+
+    /*
+    **    x BETWEEN y AND z
+    **
+    ** This is equivalent to
+    **
+    **    x>=y AND x<=z
+    **
+    ** X is stored in pExpr->pLeft.
+    ** Y is stored in pExpr->pList->a[0].pExpr.
+    ** Z is stored in pExpr->pList->a[1].pExpr.
+    */
+    case TK_BETWEEN: {
+      Expr *pX = pExpr->pLeft;
+      Expr *pY = pExpr->x.pList->a[0].pExpr;
+      Expr *pZ = pExpr->x.pList->a[1].pExpr;
+      sqlite3TreeViewLine(pView, "BETWEEN");
+      sqlite3TreeViewExpr(pView, pX, 1);
+      sqlite3TreeViewExpr(pView, pY, 1);
+      sqlite3TreeViewExpr(pView, pZ, 0);
+      break;
+    }
+    case TK_TRIGGER: {
+      /* If the opcode is TK_TRIGGER, then the expression is a reference
+      ** to a column in the new.* or old.* pseudo-tables available to
+      ** trigger programs. In this case Expr.iTable is set to 1 for the
+      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
+      ** is set to the column of the pseudo-table to read, or to -1 to
+      ** read the rowid field.
+      */
+      sqlite3TreeViewLine(pView, "%s(%d)", 
+          pExpr->iTable ? "NEW" : "OLD", pExpr->iColumn);
+      break;
+    }
+    case TK_CASE: {
+      sqlite3TreeViewLine(pView, "CASE");
+      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
+      sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
+      break;
+    }
+#ifndef SQLITE_OMIT_TRIGGER
+    case TK_RAISE: {
+      const char *zType = "unk";
+      switch( pExpr->affinity ){
+        case OE_Rollback:   zType = "rollback";  break;
+        case OE_Abort:      zType = "abort";     break;
+        case OE_Fail:       zType = "fail";      break;
+        case OE_Ignore:     zType = "ignore";    break;
+      }
+      sqlite3TreeViewLine(pView, "RAISE %s(%Q)", zType, pExpr->u.zToken);
+      break;
+    }
+#endif
+    default: {
+      sqlite3TreeViewLine(pView, "op=%d", pExpr->op);
+      break;
+    }
+  }
+  if( zBinOp ){
+    sqlite3TreeViewLine(pView, "%s%s", zBinOp, zFlgs);
+    sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
+    sqlite3TreeViewExpr(pView, pExpr->pRight, 0);
+  }else if( zUniOp ){
+    sqlite3TreeViewLine(pView, "%s%s", zUniOp, zFlgs);
+    sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
+  }
+  sqlite3TreeViewPop(pView);
+}
+
+/*
+** Generate a human-readable explanation of an expression list.
+*/
+SQLITE_PRIVATE void sqlite3TreeViewExprList(
+  TreeView *pView,
+  const ExprList *pList,
+  u8 moreToFollow,
+  const char *zLabel
+){
+  int i;
+  pView = sqlite3TreeViewPush(pView, moreToFollow);
+  if( zLabel==0 || zLabel[0]==0 ) zLabel = "LIST";
+  if( pList==0 ){
+    sqlite3TreeViewLine(pView, "%s (empty)", zLabel);
+  }else{
+    sqlite3TreeViewLine(pView, "%s", zLabel);
+    for(i=0; i<pList->nExpr; i++){
+      sqlite3TreeViewExpr(pView, pList->a[i].pExpr, i<pList->nExpr-1);
+    }
+  }
+  sqlite3TreeViewPop(pView);
+}
+
+#endif /* SQLITE_DEBUG */
+
+/************** End of treeview.c ********************************************/
 /************** Begin file random.c ******************************************/
 /*
 ** 2001 September 15
@@ -22509,6 +22991,7 @@ SQLITE_PRIVATE void sqlite3XPrintf(StrAccum *p, u32 bFlags, const char *zFormat,
 ** Random numbers are used by some of the database backends in order
 ** to generate random integer keys for tables or random filenames.
 */
+/* #include "sqliteInt.h" */
 
 
 /* All threads share a single random number generator.
@@ -22655,7 +23138,9 @@ SQLITE_PRIVATE void sqlite3PrngRestoreState(void){
 ** of multiple cores can do so, while also allowing applications to stay
 ** single-threaded if desired.
 */
+/* #include "sqliteInt.h" */
 #if SQLITE_OS_WIN
+/* #  include "os_win.h" */
 #endif
 
 #if SQLITE_MAX_WORKER_THREADS>0
@@ -22929,7 +23414,9 @@ SQLITE_PRIVATE int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){
 **     0xfe 0xff   big-endian utf-16 follows
 **
 */
+/* #include "sqliteInt.h" */
 /* #include <assert.h> */
+/* #include "vdbeInt.h" */
 
 #ifndef SQLITE_AMALGAMATION
 /*
@@ -23442,6 +23929,7 @@ SQLITE_PRIVATE void sqlite3UtfSelfTest(void){
 ** strings, and stuff like that.
 **
 */
+/* #include "sqliteInt.h" */
 /* #include <stdarg.h> */
 #if HAVE_ISNAN || SQLITE_HAVE_ISNAN
 # include <math.h>
@@ -23531,10 +24019,8 @@ SQLITE_PRIVATE int sqlite3IsNaN(double x){
 ** than 1GiB) the value returned might be less than the true string length.
 */
 SQLITE_PRIVATE int sqlite3Strlen30(const char *z){
-  const char *z2 = z;
   if( z==0 ) return 0;
-  while( *z2 ){ z2++; }
-  return 0x3fffffff & (int)(z2 - z);
+  return 0x3fffffff & (int)strlen(z);
 }
 
 /*
@@ -24506,14 +24992,38 @@ SQLITE_PRIVATE int sqlite3VarintLen(u64 v){
 ** Read or write a four-byte big-endian integer value.
 */
 SQLITE_PRIVATE u32 sqlite3Get4byte(const u8 *p){
+#if SQLITE_BYTEORDER==4321
+  u32 x;
+  memcpy(&x,p,4);
+  return x;
+#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__) && GCC_VERSION>=4003000
+  u32 x;
+  memcpy(&x,p,4);
+  return __builtin_bswap32(x);
+#elif SQLITE_BYTEORDER==1234 && defined(_MSC_VER) && _MSC_VER>=1300
+  u32 x;
+  memcpy(&x,p,4);
+  return _byteswap_ulong(x);
+#else
   testcase( p[0]&0x80 );
   return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
+#endif
 }
 SQLITE_PRIVATE void sqlite3Put4byte(unsigned char *p, u32 v){
+#if SQLITE_BYTEORDER==4321
+  memcpy(p,&v,4);
+#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__) && GCC_VERSION>=4003000
+  u32 x = __builtin_bswap32(v);
+  memcpy(p,&x,4);
+#elif SQLITE_BYTEORDER==1234 && defined(_MSC_VER) && _MSC_VER>=1300
+  u32 x = _byteswap_ulong(v);
+  memcpy(p,&x,4);
+#else
   p[0] = (u8)(v>>24);
   p[1] = (u8)(v>>16);
   p[2] = (u8)(v>>8);
   p[3] = (u8)v;
+#endif
 }
 
 
@@ -24816,6 +25326,7 @@ SQLITE_PRIVATE u64 sqlite3LogEstToInt(LogEst x){
 ** This is the implementation of generic hash-tables
 ** used in SQLite.
 */
+/* #include "sqliteInt.h" */
 /* #include <assert.h> */
 
 /* Turn bulk memory into a hash table object by initializing the
@@ -25081,42 +25592,42 @@ SQLITE_PRIVATE void *sqlite3HashInsert(Hash *pH, const char *pKey, void *data){
 #endif
 SQLITE_PRIVATE const char *sqlite3OpcodeName(int i){
  static const char *const azName[] = { "?",
-     /*   1 */ "Function"         OpHelp("r[P3]=func(r[P2@P5])"),
-     /*   2 */ "Savepoint"        OpHelp(""),
-     /*   3 */ "AutoCommit"       OpHelp(""),
-     /*   4 */ "Transaction"      OpHelp(""),
-     /*   5 */ "SorterNext"       OpHelp(""),
-     /*   6 */ "PrevIfOpen"       OpHelp(""),
-     /*   7 */ "NextIfOpen"       OpHelp(""),
-     /*   8 */ "Prev"             OpHelp(""),
-     /*   9 */ "Next"             OpHelp(""),
-     /*  10 */ "AggStep"          OpHelp("accum=r[P3] step(r[P2@P5])"),
-     /*  11 */ "Checkpoint"       OpHelp(""),
-     /*  12 */ "JournalMode"      OpHelp(""),
-     /*  13 */ "Vacuum"           OpHelp(""),
-     /*  14 */ "VFilter"          OpHelp("iplan=r[P3] zplan='P4'"),
-     /*  15 */ "VUpdate"          OpHelp("data=r[P3@P2]"),
-     /*  16 */ "Goto"             OpHelp(""),
-     /*  17 */ "Gosub"            OpHelp(""),
-     /*  18 */ "Return"           OpHelp(""),
+     /*   1 */ "Savepoint"        OpHelp(""),
+     /*   2 */ "AutoCommit"       OpHelp(""),
+     /*   3 */ "Transaction"      OpHelp(""),
+     /*   4 */ "SorterNext"       OpHelp(""),
+     /*   5 */ "PrevIfOpen"       OpHelp(""),
+     /*   6 */ "NextIfOpen"       OpHelp(""),
+     /*   7 */ "Prev"             OpHelp(""),
+     /*   8 */ "Next"             OpHelp(""),
+     /*   9 */ "Checkpoint"       OpHelp(""),
+     /*  10 */ "JournalMode"      OpHelp(""),
+     /*  11 */ "Vacuum"           OpHelp(""),
+     /*  12 */ "VFilter"          OpHelp("iplan=r[P3] zplan='P4'"),
+     /*  13 */ "VUpdate"          OpHelp("data=r[P3@P2]"),
+     /*  14 */ "Goto"             OpHelp(""),
+     /*  15 */ "Gosub"            OpHelp(""),
+     /*  16 */ "Return"           OpHelp(""),
+     /*  17 */ "InitCoroutine"    OpHelp(""),
+     /*  18 */ "EndCoroutine"     OpHelp(""),
      /*  19 */ "Not"              OpHelp("r[P2]= !r[P1]"),
-     /*  20 */ "InitCoroutine"    OpHelp(""),
-     /*  21 */ "EndCoroutine"     OpHelp(""),
-     /*  22 */ "Yield"            OpHelp(""),
-     /*  23 */ "HaltIfNull"       OpHelp("if r[P3]=null halt"),
-     /*  24 */ "Halt"             OpHelp(""),
-     /*  25 */ "Integer"          OpHelp("r[P2]=P1"),
-     /*  26 */ "Int64"            OpHelp("r[P2]=P4"),
-     /*  27 */ "String"           OpHelp("r[P2]='P4' (len=P1)"),
-     /*  28 */ "Null"             OpHelp("r[P2..P3]=NULL"),
-     /*  29 */ "SoftNull"         OpHelp("r[P1]=NULL"),
-     /*  30 */ "Blob"             OpHelp("r[P2]=P4 (len=P1)"),
-     /*  31 */ "Variable"         OpHelp("r[P2]=parameter(P1,P4)"),
-     /*  32 */ "Move"             OpHelp("r[P2@P3]=r[P1@P3]"),
-     /*  33 */ "Copy"             OpHelp("r[P2@P3+1]=r[P1@P3+1]"),
-     /*  34 */ "SCopy"            OpHelp("r[P2]=r[P1]"),
-     /*  35 */ "ResultRow"        OpHelp("output=r[P1@P2]"),
-     /*  36 */ "CollSeq"          OpHelp(""),
+     /*  20 */ "Yield"            OpHelp(""),
+     /*  21 */ "HaltIfNull"       OpHelp("if r[P3]=null halt"),
+     /*  22 */ "Halt"             OpHelp(""),
+     /*  23 */ "Integer"          OpHelp("r[P2]=P1"),
+     /*  24 */ "Int64"            OpHelp("r[P2]=P4"),
+     /*  25 */ "String"           OpHelp("r[P2]='P4' (len=P1)"),
+     /*  26 */ "Null"             OpHelp("r[P2..P3]=NULL"),
+     /*  27 */ "SoftNull"         OpHelp("r[P1]=NULL"),
+     /*  28 */ "Blob"             OpHelp("r[P2]=P4 (len=P1)"),
+     /*  29 */ "Variable"         OpHelp("r[P2]=parameter(P1,P4)"),
+     /*  30 */ "Move"             OpHelp("r[P2@P3]=r[P1@P3]"),
+     /*  31 */ "Copy"             OpHelp("r[P2@P3+1]=r[P1@P3+1]"),
+     /*  32 */ "SCopy"            OpHelp("r[P2]=r[P1]"),
+     /*  33 */ "ResultRow"        OpHelp("output=r[P1@P2]"),
+     /*  34 */ "CollSeq"          OpHelp(""),
+     /*  35 */ "Function0"        OpHelp("r[P3]=func(r[P2@P5])"),
+     /*  36 */ "Function"         OpHelp("r[P3]=func(r[P2@P5])"),
      /*  37 */ "AddImm"           OpHelp("r[P1]=r[P1]+P2"),
      /*  38 */ "MustBeInt"        OpHelp(""),
      /*  39 */ "RealAffinity"     OpHelp(""),
@@ -25142,20 +25653,20 @@ SQLITE_PRIVATE const char *sqlite3OpcodeName(int i){
      /*  59 */ "SequenceTest"     OpHelp("if( cursor[P1].ctr++ ) pc = P2"),
      /*  60 */ "OpenPseudo"       OpHelp("P3 columns in r[P2]"),
      /*  61 */ "Close"            OpHelp(""),
-     /*  62 */ "SeekLT"           OpHelp("key=r[P3@P4]"),
-     /*  63 */ "SeekLE"           OpHelp("key=r[P3@P4]"),
-     /*  64 */ "SeekGE"           OpHelp("key=r[P3@P4]"),
-     /*  65 */ "SeekGT"           OpHelp("key=r[P3@P4]"),
-     /*  66 */ "Seek"             OpHelp("intkey=r[P2]"),
-     /*  67 */ "NoConflict"       OpHelp("key=r[P3@P4]"),
-     /*  68 */ "NotFound"         OpHelp("key=r[P3@P4]"),
-     /*  69 */ "Found"            OpHelp("key=r[P3@P4]"),
-     /*  70 */ "NotExists"        OpHelp("intkey=r[P3]"),
+     /*  62 */ "ColumnsUsed"      OpHelp(""),
+     /*  63 */ "SeekLT"           OpHelp("key=r[P3@P4]"),
+     /*  64 */ "SeekLE"           OpHelp("key=r[P3@P4]"),
+     /*  65 */ "SeekGE"           OpHelp("key=r[P3@P4]"),
+     /*  66 */ "SeekGT"           OpHelp("key=r[P3@P4]"),
+     /*  67 */ "Seek"             OpHelp("intkey=r[P2]"),
+     /*  68 */ "NoConflict"       OpHelp("key=r[P3@P4]"),
+     /*  69 */ "NotFound"         OpHelp("key=r[P3@P4]"),
+     /*  70 */ "Found"            OpHelp("key=r[P3@P4]"),
      /*  71 */ "Or"               OpHelp("r[P3]=(r[P1] || r[P2])"),
      /*  72 */ "And"              OpHelp("r[P3]=(r[P1] && r[P2])"),
-     /*  73 */ "Sequence"         OpHelp("r[P2]=cursor[P1].ctr++"),
-     /*  74 */ "NewRowid"         OpHelp("r[P2]=rowid"),
-     /*  75 */ "Insert"           OpHelp("intkey=r[P3] data=r[P2]"),
+     /*  73 */ "NotExists"        OpHelp("intkey=r[P3]"),
+     /*  74 */ "Sequence"         OpHelp("r[P2]=cursor[P1].ctr++"),
+     /*  75 */ "NewRowid"         OpHelp("r[P2]=rowid"),
      /*  76 */ "IsNull"           OpHelp("if r[P1]==NULL goto P2"),
      /*  77 */ "NotNull"          OpHelp("if r[P1]!=NULL goto P2"),
      /*  78 */ "Ne"               OpHelp("if r[P1]!=r[P3] goto P2"),
@@ -25164,7 +25675,7 @@ SQLITE_PRIVATE const char *sqlite3OpcodeName(int i){
      /*  81 */ "Le"               OpHelp("if r[P1]<=r[P3] goto P2"),
      /*  82 */ "Lt"               OpHelp("if r[P1]<r[P3] goto P2"),
      /*  83 */ "Ge"               OpHelp("if r[P1]>=r[P3] goto P2"),
-     /*  84 */ "InsertInt"        OpHelp("intkey=P3 data=r[P2]"),
+     /*  84 */ "Insert"           OpHelp("intkey=r[P3] data=r[P2]"),
      /*  85 */ "BitAnd"           OpHelp("r[P3]=r[P1]&r[P2]"),
      /*  86 */ "BitOr"            OpHelp("r[P3]=r[P1]|r[P2]"),
      /*  87 */ "ShiftLeft"        OpHelp("r[P3]=r[P2]<<r[P1]"),
@@ -25175,69 +25686,72 @@ SQLITE_PRIVATE const char *sqlite3OpcodeName(int i){
      /*  92 */ "Divide"           OpHelp("r[P3]=r[P2]/r[P1]"),
      /*  93 */ "Remainder"        OpHelp("r[P3]=r[P2]%r[P1]"),
      /*  94 */ "Concat"           OpHelp("r[P3]=r[P2]+r[P1]"),
-     /*  95 */ "Delete"           OpHelp(""),
+     /*  95 */ "InsertInt"        OpHelp("intkey=P3 data=r[P2]"),
      /*  96 */ "BitNot"           OpHelp("r[P1]= ~r[P1]"),
      /*  97 */ "String8"          OpHelp("r[P2]='P4'"),
-     /*  98 */ "ResetCount"       OpHelp(""),
-     /*  99 */ "SorterCompare"    OpHelp("if key(P1)!=trim(r[P3],P4) goto P2"),
-     /* 100 */ "SorterData"       OpHelp("r[P2]=data"),
-     /* 101 */ "RowKey"           OpHelp("r[P2]=key"),
-     /* 102 */ "RowData"          OpHelp("r[P2]=data"),
-     /* 103 */ "Rowid"            OpHelp("r[P2]=rowid"),
-     /* 104 */ "NullRow"          OpHelp(""),
-     /* 105 */ "Last"             OpHelp(""),
-     /* 106 */ "SorterSort"       OpHelp(""),
-     /* 107 */ "Sort"             OpHelp(""),
-     /* 108 */ "Rewind"           OpHelp(""),
-     /* 109 */ "SorterInsert"     OpHelp(""),
-     /* 110 */ "IdxInsert"        OpHelp("key=r[P2]"),
-     /* 111 */ "IdxDelete"        OpHelp("key=r[P2@P3]"),
-     /* 112 */ "IdxRowid"         OpHelp("r[P2]=rowid"),
-     /* 113 */ "IdxLE"            OpHelp("key=r[P3@P4]"),
-     /* 114 */ "IdxGT"            OpHelp("key=r[P3@P4]"),
-     /* 115 */ "IdxLT"            OpHelp("key=r[P3@P4]"),
-     /* 116 */ "IdxGE"            OpHelp("key=r[P3@P4]"),
-     /* 117 */ "Destroy"          OpHelp(""),
-     /* 118 */ "Clear"            OpHelp(""),
-     /* 119 */ "ResetSorter"      OpHelp(""),
-     /* 120 */ "CreateIndex"      OpHelp("r[P2]=root iDb=P1"),
-     /* 121 */ "CreateTable"      OpHelp("r[P2]=root iDb=P1"),
-     /* 122 */ "ParseSchema"      OpHelp(""),
-     /* 123 */ "LoadAnalysis"     OpHelp(""),
-     /* 124 */ "DropTable"        OpHelp(""),
-     /* 125 */ "DropIndex"        OpHelp(""),
-     /* 126 */ "DropTrigger"      OpHelp(""),
-     /* 127 */ "IntegrityCk"      OpHelp(""),
-     /* 128 */ "RowSetAdd"        OpHelp("rowset(P1)=r[P2]"),
-     /* 129 */ "RowSetRead"       OpHelp("r[P3]=rowset(P1)"),
-     /* 130 */ "RowSetTest"       OpHelp("if r[P3] in rowset(P1) goto P2"),
-     /* 131 */ "Program"          OpHelp(""),
-     /* 132 */ "Param"            OpHelp(""),
+     /*  98 */ "Delete"           OpHelp(""),
+     /*  99 */ "ResetCount"       OpHelp(""),
+     /* 100 */ "SorterCompare"    OpHelp("if key(P1)!=trim(r[P3],P4) goto P2"),
+     /* 101 */ "SorterData"       OpHelp("r[P2]=data"),
+     /* 102 */ "RowKey"           OpHelp("r[P2]=key"),
+     /* 103 */ "RowData"          OpHelp("r[P2]=data"),
+     /* 104 */ "Rowid"            OpHelp("r[P2]=rowid"),
+     /* 105 */ "NullRow"          OpHelp(""),
+     /* 106 */ "Last"             OpHelp(""),
+     /* 107 */ "SorterSort"       OpHelp(""),
+     /* 108 */ "Sort"             OpHelp(""),
+     /* 109 */ "Rewind"           OpHelp(""),
+     /* 110 */ "SorterInsert"     OpHelp(""),
+     /* 111 */ "IdxInsert"        OpHelp("key=r[P2]"),
+     /* 112 */ "IdxDelete"        OpHelp("key=r[P2@P3]"),
+     /* 113 */ "IdxRowid"         OpHelp("r[P2]=rowid"),
+     /* 114 */ "IdxLE"            OpHelp("key=r[P3@P4]"),
+     /* 115 */ "IdxGT"            OpHelp("key=r[P3@P4]"),
+     /* 116 */ "IdxLT"            OpHelp("key=r[P3@P4]"),
+     /* 117 */ "IdxGE"            OpHelp("key=r[P3@P4]"),
+     /* 118 */ "Destroy"          OpHelp(""),
+     /* 119 */ "Clear"            OpHelp(""),
+     /* 120 */ "ResetSorter"      OpHelp(""),
+     /* 121 */ "CreateIndex"      OpHelp("r[P2]=root iDb=P1"),
+     /* 122 */ "CreateTable"      OpHelp("r[P2]=root iDb=P1"),
+     /* 123 */ "ParseSchema"      OpHelp(""),
+     /* 124 */ "LoadAnalysis"     OpHelp(""),
+     /* 125 */ "DropTable"        OpHelp(""),
+     /* 126 */ "DropIndex"        OpHelp(""),
+     /* 127 */ "DropTrigger"      OpHelp(""),
+     /* 128 */ "IntegrityCk"      OpHelp(""),
+     /* 129 */ "RowSetAdd"        OpHelp("rowset(P1)=r[P2]"),
+     /* 130 */ "RowSetRead"       OpHelp("r[P3]=rowset(P1)"),
+     /* 131 */ "RowSetTest"       OpHelp("if r[P3] in rowset(P1) goto P2"),
+     /* 132 */ "Program"          OpHelp(""),
      /* 133 */ "Real"             OpHelp("r[P2]=P4"),
-     /* 134 */ "FkCounter"        OpHelp("fkctr[P1]+=P2"),
-     /* 135 */ "FkIfZero"         OpHelp("if fkctr[P1]==0 goto P2"),
-     /* 136 */ "MemMax"           OpHelp("r[P1]=max(r[P1],r[P2])"),
-     /* 137 */ "IfPos"            OpHelp("if r[P1]>0 goto P2"),
-     /* 138 */ "IfNeg"            OpHelp("r[P1]+=P3, if r[P1]<0 goto P2"),
-     /* 139 */ "IfNotZero"        OpHelp("if r[P1]!=0 then r[P1]+=P3, goto P2"),
-     /* 140 */ "DecrJumpZero"     OpHelp("if (--r[P1])==0 goto P2"),
-     /* 141 */ "JumpZeroIncr"     OpHelp("if (r[P1]++)==0 ) goto P2"),
-     /* 142 */ "AggFinal"         OpHelp("accum=r[P1] N=P2"),
-     /* 143 */ "IncrVacuum"       OpHelp(""),
-     /* 144 */ "Expire"           OpHelp(""),
-     /* 145 */ "TableLock"        OpHelp("iDb=P1 root=P2 write=P3"),
-     /* 146 */ "VBegin"           OpHelp(""),
-     /* 147 */ "VCreate"          OpHelp(""),
-     /* 148 */ "VDestroy"         OpHelp(""),
-     /* 149 */ "VOpen"            OpHelp(""),
-     /* 150 */ "VColumn"          OpHelp("r[P3]=vcolumn(P2)"),
-     /* 151 */ "VNext"            OpHelp(""),
-     /* 152 */ "VRename"          OpHelp(""),
-     /* 153 */ "Pagecount"        OpHelp(""),
-     /* 154 */ "MaxPgcnt"         OpHelp(""),
-     /* 155 */ "Init"             OpHelp("Start at P2"),
-     /* 156 */ "Noop"             OpHelp(""),
-     /* 157 */ "Explain"          OpHelp(""),
+     /* 134 */ "Param"            OpHelp(""),
+     /* 135 */ "FkCounter"        OpHelp("fkctr[P1]+=P2"),
+     /* 136 */ "FkIfZero"         OpHelp("if fkctr[P1]==0 goto P2"),
+     /* 137 */ "MemMax"           OpHelp("r[P1]=max(r[P1],r[P2])"),
+     /* 138 */ "IfPos"            OpHelp("if r[P1]>0 goto P2"),
+     /* 139 */ "IfNeg"            OpHelp("r[P1]+=P3, if r[P1]<0 goto P2"),
+     /* 140 */ "IfNotZero"        OpHelp("if r[P1]!=0 then r[P1]+=P3, goto P2"),
+     /* 141 */ "DecrJumpZero"     OpHelp("if (--r[P1])==0 goto P2"),
+     /* 142 */ "JumpZeroIncr"     OpHelp("if (r[P1]++)==0 ) goto P2"),
+     /* 143 */ "AggStep0"         OpHelp("accum=r[P3] step(r[P2@P5])"),
+     /* 144 */ "AggStep"          OpHelp("accum=r[P3] step(r[P2@P5])"),
+     /* 145 */ "AggFinal"         OpHelp("accum=r[P1] N=P2"),
+     /* 146 */ "IncrVacuum"       OpHelp(""),
+     /* 147 */ "Expire"           OpHelp(""),
+     /* 148 */ "TableLock"        OpHelp("iDb=P1 root=P2 write=P3"),
+     /* 149 */ "VBegin"           OpHelp(""),
+     /* 150 */ "VCreate"          OpHelp(""),
+     /* 151 */ "VDestroy"         OpHelp(""),
+     /* 152 */ "VOpen"            OpHelp(""),
+     /* 153 */ "VColumn"          OpHelp("r[P3]=vcolumn(P2)"),
+     /* 154 */ "VNext"            OpHelp(""),
+     /* 155 */ "VRename"          OpHelp(""),
+     /* 156 */ "Pagecount"        OpHelp(""),
+     /* 157 */ "MaxPgcnt"         OpHelp(""),
+     /* 158 */ "Init"             OpHelp("Start at P2"),
+     /* 159 */ "Noop"             OpHelp(""),
+     /* 160 */ "Explain"          OpHelp(""),
   };
   return azName[i];
 }
@@ -25290,6 +25804,7 @@ SQLITE_PRIVATE const char *sqlite3OpcodeName(int i){
 **   *  Definitions of sqlite3_vfs objects for all locking methods
 **      plus implementations of sqlite3_os_init() and sqlite3_os_end().
 */
+/* #include "sqliteInt.h" */
 #if SQLITE_OS_UNIX              /* This file is used on unix only */
 
 /*
@@ -26073,14 +26588,14 @@ static int robust_open(const char *z, int f, mode_t m){
 **   unixEnterLeave()
 */
 static void unixEnterMutex(void){
-  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
 }
 static void unixLeaveMutex(void){
-  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
 }
 #ifdef SQLITE_DEBUG
 static int unixMutexHeld(void) {
-  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
 }
 #endif
 
@@ -33024,6 +33539,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_os_end(void){
 **
 ** This file contains code that is specific to Windows.
 */
+/* #include "sqliteInt.h" */
 #if SQLITE_OS_WIN               /* This file is used for Windows only */
 
 /*
@@ -33232,6 +33748,7 @@ SQLITE_API int sqlite3_open_file_count = 0;
 /*
 ** Include the header file for the Windows VFS.
 */
+/* #include "os_win.h" */
 
 /*
 ** Compiling and using WAL mode requires several APIs that are only
@@ -36223,6 +36740,12 @@ static int winLock(sqlite3_file *id, int locktype){
     return SQLITE_OK;
   }
 
+  /* Do not allow any kind of write-lock on a read-only database
+  */
+  if( (pFile->ctrlFlags & WINFILE_RDONLY)!=0 && locktype>=RESERVED_LOCK ){
+    return SQLITE_IOERR_LOCK;
+  }
+
   /* Make sure the locking sequence is correct
   */
   assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
@@ -36592,14 +37115,14 @@ static SYSTEM_INFO winSysInfo;
 **   winShmLeaveMutex()
 */
 static void winShmEnterMutex(void){
-  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
 }
 static void winShmLeaveMutex(void){
-  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
 }
 #ifndef NDEBUG
 static int winShmMutexHeld(void) {
-  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
+  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
 }
 #endif
 
@@ -38619,14 +39142,14 @@ static int winRandomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
     UUID id;
     memset(&id, 0, sizeof(UUID));
     osUuidCreate(&id);
-    memcpy(zBuf, &id, sizeof(UUID));
+    memcpy(&zBuf[n], &id, sizeof(UUID));
     n += sizeof(UUID);
   }
   if( sizeof(UUID)<=nBuf-n ){
     UUID id;
     memset(&id, 0, sizeof(UUID));
     osUuidCreateSequential(&id);
-    memcpy(zBuf, &id, sizeof(UUID));
+    memcpy(&zBuf[n], &id, sizeof(UUID));
     n += sizeof(UUID);
   }
 #endif
@@ -38879,6 +39402,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_os_end(void){
 ** start of a transaction, and is thus usually less than a few thousand,
 ** but can be as large as 2 billion for a really big database.
 */
+/* #include "sqliteInt.h" */
 
 /* Size of the Bitvec structure in bytes. */
 #define BITVEC_SZ        512
@@ -38970,10 +39494,10 @@ SQLITE_PRIVATE Bitvec *sqlite3BitvecCreate(u32 iSize){
 ** If p is NULL (if the bitmap has not been created) or if
 ** i is out of range, then return false.
 */
-SQLITE_PRIVATE int sqlite3BitvecTest(Bitvec *p, u32 i){
-  if( p==0 ) return 0;
-  if( i>p->iSize || i==0 ) return 0;
+SQLITE_PRIVATE int sqlite3BitvecTestNotNull(Bitvec *p, u32 i){
+  assert( p!=0 );
   i--;
+  if( i>=p->iSize ) return 0;
   while( p->iDivisor ){
     u32 bin = i/p->iDivisor;
     i = i%p->iDivisor;
@@ -38993,6 +39517,9 @@ SQLITE_PRIVATE int sqlite3BitvecTest(Bitvec *p, u32 i){
     return 0;
   }
 }
+SQLITE_PRIVATE int sqlite3BitvecTest(Bitvec *p, u32 i){
+  return p!=0 && sqlite3BitvecTestNotNull(p,i);
+}
 
 /*
 ** Set the i-th bit.  Return 0 on success and an error code if
@@ -39265,6 +39792,7 @@ bitvec_end:
 *************************************************************************
 ** This file implements that page cache.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** A complete page cache is an instance of this structure.
@@ -39281,7 +39809,6 @@ struct PCache {
   int (*xStress)(void*,PgHdr*);       /* Call to try make a page clean */
   void *pStress;                      /* Argument to xStress */
   sqlite3_pcache *pCache;             /* Pluggable cache module */
-  PgHdr *pPage1;                      /* Reference to page 1 */
 };
 
 /********************************** Linked List Management ********************/
@@ -39359,9 +39886,6 @@ static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){
 */
 static void pcacheUnpin(PgHdr *p){
   if( p->pCache->bPurgeable ){
-    if( p->pgno==1 ){
-      p->pCache->pPage1 = 0;
-    }
     sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
   }
 }
@@ -39454,7 +39978,6 @@ SQLITE_PRIVATE int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
       sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
     }
     pCache->pCache = pNew;
-    pCache->pPage1 = 0;
     pCache->szPage = szPage;
   }
   return SQLITE_OK;
@@ -39579,13 +40102,14 @@ static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit(
   assert( pPage!=0 );
   pPgHdr = (PgHdr*)pPage->pExtra;
   assert( pPgHdr->pPage==0 );
- memset(pPgHdr, 0, sizeof(PgHdr));
+  memset(pPgHdr, 0, sizeof(PgHdr));
   pPgHdr->pPage = pPage;
   pPgHdr->pData = pPage->pBuf;
   pPgHdr->pExtra = (void *)&pPgHdr[1];
   memset(pPgHdr->pExtra, 0, pCache->szExtra);
   pPgHdr->pCache = pCache;
   pPgHdr->pgno = pgno;
+  pPgHdr->flags = PGHDR_CLEAN;
   return sqlite3PcacheFetchFinish(pCache,pgno,pPage);
 }
 
@@ -39602,7 +40126,7 @@ SQLITE_PRIVATE PgHdr *sqlite3PcacheFetchFinish(
 ){
   PgHdr *pPgHdr;
 
-  if( pPage==0 ) return 0;
+  assert( pPage!=0 );
   pPgHdr = (PgHdr *)pPage->pExtra;
 
   if( !pPgHdr->pPage ){
@@ -39612,9 +40136,6 @@ SQLITE_PRIVATE PgHdr *sqlite3PcacheFetchFinish(
     pCache->nRef++;
   }
   pPgHdr->nRef++;
-  if( pgno==1 ){
-    pCache->pPage1 = pPgHdr;
-  }
   return pPgHdr;
 }
 
@@ -39627,7 +40148,7 @@ SQLITE_PRIVATE void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
   p->nRef--;
   if( p->nRef==0 ){
     p->pCache->nRef--;
-    if( (p->flags&PGHDR_DIRTY)==0 ){
+    if( p->flags&PGHDR_CLEAN ){
       pcacheUnpin(p);
     }else if( p->pDirtyPrev!=0 ){
       /* Move the page to the head of the dirty list. */
@@ -39655,9 +40176,6 @@ SQLITE_PRIVATE void sqlite3PcacheDrop(PgHdr *p){
     pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
   }
   p->pCache->nRef--;
-  if( p->pgno==1 ){
-    p->pCache->pPage1 = 0;
-  }
   sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1);
 }
 
@@ -39666,11 +40184,14 @@ SQLITE_PRIVATE void sqlite3PcacheDrop(PgHdr *p){
 ** make it so.
 */
 SQLITE_PRIVATE void sqlite3PcacheMakeDirty(PgHdr *p){
-  p->flags &= ~PGHDR_DONT_WRITE;
   assert( p->nRef>0 );
-  if( 0==(p->flags & PGHDR_DIRTY) ){
-    p->flags |= PGHDR_DIRTY;
-    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
+  if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){
+    p->flags &= ~PGHDR_DONT_WRITE;
+    if( p->flags & PGHDR_CLEAN ){
+      p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN);
+      assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY );
+      pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
+    }
   }
 }
 
@@ -39680,8 +40201,10 @@ SQLITE_PRIVATE void sqlite3PcacheMakeDirty(PgHdr *p){
 */
 SQLITE_PRIVATE void sqlite3PcacheMakeClean(PgHdr *p){
   if( (p->flags & PGHDR_DIRTY) ){
+    assert( (p->flags & PGHDR_CLEAN)==0 );
     pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
-    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC);
+    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
+    p->flags |= PGHDR_CLEAN;
     if( p->nRef==0 ){
       pcacheUnpin(p);
     }
@@ -39748,9 +40271,14 @@ SQLITE_PRIVATE void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
         sqlite3PcacheMakeClean(p);
       }
     }
-    if( pgno==0 && pCache->pPage1 ){
-      memset(pCache->pPage1->pData, 0, pCache->szPage);
-      pgno = 1;
+    if( pgno==0 && pCache->nRef ){
+      sqlite3_pcache_page *pPage1;
+      pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0);
+      if( ALWAYS(pPage1) ){  /* Page 1 is always available in cache, because
+                             ** pCache->nRef>0 */
+        memset(pPage1->pBuf, 0, pCache->szPage);
+        pgno = 1;
+      }
     }
     sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
   }
@@ -39941,8 +40469,72 @@ SQLITE_PRIVATE void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHd
 ** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features.
 ** If the default page cache implementation is overridden, then neither of
 ** these two features are available.
+**
+** A Page cache line looks like this:
+**
+**  -------------------------------------------------------------
+**  |  database page content   |  PgHdr1  |  MemPage  |  PgHdr  |
+**  -------------------------------------------------------------
+**
+** The database page content is up front (so that buffer overreads tend to
+** flow harmlessly into the PgHdr1, MemPage, and PgHdr extensions).   MemPage
+** is the extension added by the btree.c module containing information such
+** as the database page number and how that database page is used.  PgHdr
+** is added by the pcache.c layer and contains information used to keep track
+** of which pages are "dirty".  PgHdr1 is an extension added by this
+** module (pcache1.c).  The PgHdr1 header is a subclass of sqlite3_pcache_page.
+** PgHdr1 contains information needed to look up a page by its page number.
+** The superclass sqlite3_pcache_page.pBuf points to the start of the
+** database page content and sqlite3_pcache_page.pExtra points to PgHdr.
+**
+** The size of the extension (MemPage+PgHdr+PgHdr1) can be determined at
+** runtime using sqlite3_config(SQLITE_CONFIG_PCACHE_HDRSZ, &size).  The
+** sizes of the extensions sum to 272 bytes on x64 for 3.8.10, but this
+** size can vary according to architecture, compile-time options, and
+** SQLite library version number.
+**
+** If SQLITE_PCACHE_SEPARATE_HEADER is defined, then the extension is obtained
+** using a separate memory allocation from the database page content.  This
+** seeks to overcome the "clownshoe" problem (also called "internal
+** fragmentation" in academic literature) of allocating a few bytes more
+** than a power of two with the memory allocator rounding up to the next
+** power of two, and leaving the rounded-up space unused.
+**
+** This module tracks pointers to PgHdr1 objects.  Only pcache.c communicates
+** with this module.  Information is passed back and forth as PgHdr1 pointers.
+**
+** The pcache.c and pager.c modules deal pointers to PgHdr objects.
+** The btree.c module deals with pointers to MemPage objects.
+**
+** SOURCE OF PAGE CACHE MEMORY:
+**
+** Memory for a page might come from any of three sources:
+**
+**    (1)  The general-purpose memory allocator - sqlite3Malloc()
+**    (2)  Global page-cache memory provided using sqlite3_config() with
+**         SQLITE_CONFIG_PAGECACHE.
+**    (3)  PCache-local bulk allocation.
+**
+** The third case is a chunk of heap memory (defaulting to 100 pages worth)
+** that is allocated when the page cache is created.  The size of the local
+** bulk allocation can be adjusted using 
+**
+**     sqlite3_config(SQLITE_CONFIG_PCACHE, 0, 0, N).
+**
+** If N is positive, then N pages worth of memory are allocated using a single
+** sqlite3Malloc() call and that memory is used for the first N pages allocated.
+** Or if N is negative, then -1024*N bytes of memory are allocated and used
+** for as many pages as can be accomodated.
+**
+** Only one of (2) or (3) can be used.  Once the memory available to (2) or
+** (3) is exhausted, subsequent allocations fail over to the general-purpose
+** memory allocator (1).
+**
+** Earlier versions of SQLite used only methods (1) and (2).  But experiments
+** show that method (3) with N==100 provides about a 5% performance boost for
+** common workloads.
 */
-
+/* #include "sqliteInt.h" */
 
 typedef struct PCache1 PCache1;
 typedef struct PgHdr1 PgHdr1;
@@ -39995,8 +40587,9 @@ struct PCache1 {
   ** The PGroup mutex must be held when accessing nMax.
   */
   PGroup *pGroup;                     /* PGroup this cache belongs to */
-  int szPage;                         /* Size of allocated pages in bytes */
-  int szExtra;                        /* Size of extra space in bytes */
+  int szPage;                         /* Size of database content section */
+  int szExtra;                        /* sizeof(MemPage)+sizeof(PgHdr) */
+  int szAlloc;                        /* Total size of one pcache line */
   int bPurgeable;                     /* True if cache is purgeable */
   unsigned int nMin;                  /* Minimum number of pages reserved */
   unsigned int nMax;                  /* Configured "cache_size" value */
@@ -40010,6 +40603,8 @@ struct PCache1 {
   unsigned int nPage;                 /* Total number of pages in apHash */
   unsigned int nHash;                 /* Number of slots in apHash[] */
   PgHdr1 **apHash;                    /* Hash table for fast lookup by key */
+  PgHdr1 *pFree;                      /* List of unused pcache-local pages */
+  void *pBulk;                        /* Bulk memory used by pcache-local */
 };
 
 /*
@@ -40022,6 +40617,7 @@ struct PgHdr1 {
   sqlite3_pcache_page page;
   unsigned int iKey;             /* Key value (page number) */
   u8 isPinned;                   /* Page in use, not on the LRU list */
+  u8 isBulkLocal;                /* This page from bulk local storage */
   PgHdr1 *pNext;                 /* Next in hash table chain */
   PCache1 *pCache;               /* Cache that currently owns this page */
   PgHdr1 *pLruNext;              /* Next in LRU list of unpinned pages */
@@ -40029,8 +40625,8 @@ struct PgHdr1 {
 };
 
 /*
-** Free slots in the allocator used to divide up the buffer provided using
-** the SQLITE_CONFIG_PAGECACHE mechanism.
+** Free slots in the allocator used to divide up the global page cache
+** buffer provided using the SQLITE_CONFIG_PAGECACHE mechanism.
 */
 struct PgFreeslot {
   PgFreeslot *pNext;  /* Next free slot */
@@ -40048,10 +40644,12 @@ static SQLITE_WSD struct PCacheGlobal {
   ** The nFreeSlot and pFree values do require mutex protection.
   */
   int isInit;                    /* True if initialized */
+  int separateCache;             /* Use a new PGroup for each PCache */
+  int nInitPage;                 /* Initial bulk allocation size */   
   int szSlot;                    /* Size of each free slot */
   int nSlot;                     /* The number of pcache slots */
   int nReserve;                  /* Try to keep nFreeSlot above this */
-  void *pStart, *pEnd;           /* Bounds of pagecache malloc range */
+  void *pStart, *pEnd;           /* Bounds of global page cache memory */
   /* Above requires no mutex.  Use mutex below for variable that follow. */
   sqlite3_mutex *mutex;          /* Mutex for accessing the following: */
   PgFreeslot *pFree;             /* Free page blocks */
@@ -40073,8 +40671,15 @@ static SQLITE_WSD struct PCacheGlobal {
 /*
 ** Macros to enter and leave the PCache LRU mutex.
 */
-#define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex)
-#define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->mutex)
+#if !defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0
+# define pcache1EnterMutex(X)  assert((X)->mutex==0)
+# define pcache1LeaveMutex(X)  assert((X)->mutex==0)
+# define PCACHE1_MIGHT_USE_GROUP_MUTEX 0
+#else
+# define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex)
+# define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->mutex)
+# define PCACHE1_MIGHT_USE_GROUP_MUTEX 1
+#endif
 
 /******************************************************************************/
 /******** Page Allocation/SQLITE_CONFIG_PCACHE Related Functions **************/
@@ -40091,6 +40696,7 @@ static SQLITE_WSD struct PCacheGlobal {
 SQLITE_PRIVATE void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
   if( pcache1.isInit ){
     PgFreeslot *p;
+    if( pBuf==0 ) sz = n = 0;
     sz = ROUNDDOWN8(sz);
     pcache1.szSlot = sz;
     pcache1.nSlot = pcache1.nFreeSlot = n;
@@ -40108,6 +40714,43 @@ SQLITE_PRIVATE void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
   }
 }
 
+/*
+** Try to initialize the pCache->pFree and pCache->pBulk fields.  Return
+** true if pCache->pFree ends up containing one or more free pages.
+*/
+static int pcache1InitBulk(PCache1 *pCache){
+  i64 szBulk;
+  char *zBulk;
+  if( pcache1.nInitPage==0 ) return 0;
+  /* Do not bother with a bulk allocation if the cache size very small */
+  if( pCache->nMax<3 ) return 0;
+  sqlite3BeginBenignMalloc();
+  if( pcache1.nInitPage>0 ){
+    szBulk = pCache->szAlloc * (i64)pcache1.nInitPage;
+  }else{
+    szBulk = -1024 * (i64)pcache1.nInitPage;
+  }
+  if( szBulk > pCache->szAlloc*(i64)pCache->nMax ){
+    szBulk = pCache->szAlloc*pCache->nMax;
+  }
+  zBulk = pCache->pBulk = sqlite3Malloc( szBulk );
+  sqlite3EndBenignMalloc();
+  if( zBulk ){
+    int nBulk = sqlite3MallocSize(zBulk)/pCache->szAlloc;
+    int i;
+    for(i=0; i<nBulk; i++){
+      PgHdr1 *pX = (PgHdr1*)&zBulk[pCache->szPage];
+      pX->page.pBuf = zBulk;
+      pX->page.pExtra = &pX[1];
+      pX->isBulkLocal = 1;
+      pX->pNext = pCache->pFree;
+      pCache->pFree = pX;
+      zBulk += pCache->szAlloc;
+    }
+  }
+  return pCache->pFree!=0;
+}
+
 /*
 ** Malloc function used within this file to allocate space from the buffer
 ** configured using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no 
@@ -40155,9 +40798,9 @@ static void *pcache1Alloc(int nByte){
 /*
 ** Free an allocated buffer obtained from pcache1Alloc().
 */
-static int pcache1Free(void *p){
+static void pcache1Free(void *p){
   int nFreed = 0;
-  if( p==0 ) return 0;
+  if( p==0 ) return;
   if( p>=pcache1.pStart && p<pcache1.pEnd ){
     PgFreeslot *pSlot;
     sqlite3_mutex_enter(pcache1.mutex);
@@ -40172,15 +40815,14 @@ static int pcache1Free(void *p){
   }else{
     assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
     sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-    nFreed = sqlite3MallocSize(p);
 #ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
+    nFreed = sqlite3MallocSize(p);
     sqlite3_mutex_enter(pcache1.mutex);
     sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_OVERFLOW, nFreed);
     sqlite3_mutex_leave(pcache1.mutex);
 #endif
     sqlite3_free(p);
   }
-  return nFreed;
 }
 
 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
@@ -40208,54 +40850,65 @@ static PgHdr1 *pcache1AllocPage(PCache1 *pCache){
   PgHdr1 *p = 0;
   void *pPg;
 
-  /* The group mutex must be released before pcache1Alloc() is called. This
-  ** is because it may call sqlite3_release_memory(), which assumes that 
-  ** this mutex is not held. */
   assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  pcache1LeaveMutex(pCache->pGroup);
+  if( pCache->pFree || (pCache->nPage==0 && pcache1InitBulk(pCache)) ){
+    p = pCache->pFree;
+    pCache->pFree = p->pNext;
+    p->pNext = 0;
+  }else{
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+    /* The group mutex must be released before pcache1Alloc() is called. This
+    ** is because it might call sqlite3_release_memory(), which assumes that 
+    ** this mutex is not held. */
+    assert( pcache1.separateCache==0 );
+    assert( pCache->pGroup==&pcache1.grp );
+    pcache1LeaveMutex(pCache->pGroup);
+#endif
 #ifdef SQLITE_PCACHE_SEPARATE_HEADER
-  pPg = pcache1Alloc(pCache->szPage);
-  p = sqlite3Malloc(sizeof(PgHdr1) + pCache->szExtra);
-  if( !pPg || !p ){
-    pcache1Free(pPg);
-    sqlite3_free(p);
-    pPg = 0;
-  }
+    pPg = pcache1Alloc(pCache->szPage);
+    p = sqlite3Malloc(sizeof(PgHdr1) + pCache->szExtra);
+    if( !pPg || !p ){
+      pcache1Free(pPg);
+      sqlite3_free(p);
+      pPg = 0;
+    }
 #else
-  pPg = pcache1Alloc(ROUND8(sizeof(PgHdr1)) + pCache->szPage + pCache->szExtra);
-  p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
+    pPg = pcache1Alloc(pCache->szAlloc);
+    p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
 #endif
-  pcache1EnterMutex(pCache->pGroup);
-
-  if( pPg ){
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+    pcache1EnterMutex(pCache->pGroup);
+#endif
+    if( pPg==0 ) return 0;
     p->page.pBuf = pPg;
     p->page.pExtra = &p[1];
-    if( pCache->bPurgeable ){
-      pCache->pGroup->nCurrentPage++;
-    }
-    return p;
+    p->isBulkLocal = 0;
   }
-  return 0;
+  if( pCache->bPurgeable ){
+    pCache->pGroup->nCurrentPage++;
+  }
+  return p;
 }
 
 /*
 ** Free a page object allocated by pcache1AllocPage().
-**
-** The pointer is allowed to be NULL, which is prudent.  But it turns out
-** that the current implementation happens to never call this routine
-** with a NULL pointer, so we mark the NULL test with ALWAYS().
 */
 static void pcache1FreePage(PgHdr1 *p){
-  if( ALWAYS(p) ){
-    PCache1 *pCache = p->pCache;
-    assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) );
+  PCache1 *pCache;
+  assert( p!=0 );
+  pCache = p->pCache;
+  assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) );
+  if( p->isBulkLocal ){
+    p->pNext = pCache->pFree;
+    pCache->pFree = p;
+  }else{
     pcache1Free(p->page.pBuf);
 #ifdef SQLITE_PCACHE_SEPARATE_HEADER
     sqlite3_free(p);
 #endif
-    if( pCache->bPurgeable ){
-      pCache->pGroup->nCurrentPage--;
-    }
+  }
+  if( pCache->bPurgeable ){
+    pCache->pGroup->nCurrentPage--;
   }
 }
 
@@ -40350,41 +41003,41 @@ static void pcache1ResizeHash(PCache1 *p){
 **
 ** The PGroup mutex must be held when this function is called.
 */
-static void pcache1PinPage(PgHdr1 *pPage){
+static PgHdr1 *pcache1PinPage(PgHdr1 *pPage){
   PCache1 *pCache;
-  PGroup *pGroup;
 
   assert( pPage!=0 );
   assert( pPage->isPinned==0 );
   pCache = pPage->pCache;
-  pGroup = pCache->pGroup;
-  assert( pPage->pLruNext || pPage==pGroup->pLruTail );
-  assert( pPage->pLruPrev || pPage==pGroup->pLruHead );
-  assert( sqlite3_mutex_held(pGroup->mutex) );
+  assert( pPage->pLruNext || pPage==pCache->pGroup->pLruTail );
+  assert( pPage->pLruPrev || pPage==pCache->pGroup->pLruHead );
+  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
   if( pPage->pLruPrev ){
     pPage->pLruPrev->pLruNext = pPage->pLruNext;
   }else{
-    pGroup->pLruHead = pPage->pLruNext;
+    pCache->pGroup->pLruHead = pPage->pLruNext;
   }
   if( pPage->pLruNext ){
     pPage->pLruNext->pLruPrev = pPage->pLruPrev;
   }else{
-    pGroup->pLruTail = pPage->pLruPrev;
+    pCache->pGroup->pLruTail = pPage->pLruPrev;
   }
   pPage->pLruNext = 0;
   pPage->pLruPrev = 0;
   pPage->isPinned = 1;
   pCache->nRecyclable--;
+  return pPage;
 }
 
 
 /*
 ** Remove the page supplied as an argument from the hash table 
 ** (PCache1.apHash structure) that it is currently stored in.
+** Also free the page if freePage is true.
 **
 ** The PGroup mutex must be held when this function is called.
 */
-static void pcache1RemoveFromHash(PgHdr1 *pPage){
+static void pcache1RemoveFromHash(PgHdr1 *pPage, int freeFlag){
   unsigned int h;
   PCache1 *pCache = pPage->pCache;
   PgHdr1 **pp;
@@ -40395,21 +41048,26 @@ static void pcache1RemoveFromHash(PgHdr1 *pPage){
   *pp = (*pp)->pNext;
 
   pCache->nPage--;
+  if( freeFlag ) pcache1FreePage(pPage);
 }
 
 /*
 ** If there are currently more than nMaxPage pages allocated, try
 ** to recycle pages to reduce the number allocated to nMaxPage.
 */
-static void pcache1EnforceMaxPage(PGroup *pGroup){
+static void pcache1EnforceMaxPage(PCache1 *pCache){
+  PGroup *pGroup = pCache->pGroup;
   assert( sqlite3_mutex_held(pGroup->mutex) );
   while( pGroup->nCurrentPage>pGroup->nMaxPage && pGroup->pLruTail ){
     PgHdr1 *p = pGroup->pLruTail;
     assert( p->pCache->pGroup==pGroup );
     assert( p->isPinned==0 );
     pcache1PinPage(p);
-    pcache1RemoveFromHash(p);
-    pcache1FreePage(p);
+    pcache1RemoveFromHash(p, 1);
+  }
+  if( pCache->nPage==0 && pCache->pBulk ){
+    sqlite3_free(pCache->pBulk);
+    pCache->pBulk = pCache->pFree = 0;
   }
 }
 
@@ -40455,10 +41113,45 @@ static int pcache1Init(void *NotUsed){
   UNUSED_PARAMETER(NotUsed);
   assert( pcache1.isInit==0 );
   memset(&pcache1, 0, sizeof(pcache1));
+
+
+  /*
+  ** The pcache1.separateCache variable is true if each PCache has its own
+  ** private PGroup (mode-1).  pcache1.separateCache is false if the single
+  ** PGroup in pcache1.grp is used for all page caches (mode-2).
+  **
+  **   *  Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT
+  **
+  **   *  Use a unified cache in single-threaded applications that have
+  **      configured a start-time buffer for use as page-cache memory using
+  **      sqlite3_config(SQLITE_CONFIG_PAGECACHE, pBuf, sz, N) with non-NULL 
+  **      pBuf argument.
+  **
+  **   *  Otherwise use separate caches (mode-1)
+  */
+#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT)
+  pcache1.separateCache = 0;
+#elif SQLITE_THREADSAFE
+  pcache1.separateCache = sqlite3GlobalConfig.pPage==0
+                          || sqlite3GlobalConfig.bCoreMutex>0;
+#else
+  pcache1.separateCache = sqlite3GlobalConfig.pPage==0;
+#endif
+
+#if SQLITE_THREADSAFE
   if( sqlite3GlobalConfig.bCoreMutex ){
     pcache1.grp.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU);
     pcache1.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PMEM);
   }
+#endif
+  if( pcache1.separateCache
+   && sqlite3GlobalConfig.nPage!=0
+   && sqlite3GlobalConfig.pPage==0
+  ){
+    pcache1.nInitPage = sqlite3GlobalConfig.nPage;
+  }else{
+    pcache1.nInitPage = 0;
+  }
   pcache1.grp.mxPinned = 10;
   pcache1.isInit = 1;
   return SQLITE_OK;
@@ -40488,31 +41181,13 @@ static sqlite3_pcache *pcache1Create(int szPage, int szExtra, int bPurgeable){
   PGroup *pGroup;       /* The group the new page cache will belong to */
   int sz;               /* Bytes of memory required to allocate the new cache */
 
-  /*
-  ** The separateCache variable is true if each PCache has its own private
-  ** PGroup.  In other words, separateCache is true for mode (1) where no
-  ** mutexing is required.
-  **
-  **   *  Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT
-  **
-  **   *  Always use a unified cache in single-threaded applications
-  **
-  **   *  Otherwise (if multi-threaded and ENABLE_MEMORY_MANAGEMENT is off)
-  **      use separate caches (mode-1)
-  */
-#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0
-  const int separateCache = 0;
-#else
-  int separateCache = sqlite3GlobalConfig.bCoreMutex>0;
-#endif
-
   assert( (szPage & (szPage-1))==0 && szPage>=512 && szPage<=65536 );
   assert( szExtra < 300 );
 
-  sz = sizeof(PCache1) + sizeof(PGroup)*separateCache;
+  sz = sizeof(PCache1) + sizeof(PGroup)*pcache1.separateCache;
   pCache = (PCache1 *)sqlite3MallocZero(sz);
   if( pCache ){
-    if( separateCache ){
+    if( pcache1.separateCache ){
       pGroup = (PGroup*)&pCache[1];
       pGroup->mxPinned = 10;
     }else{
@@ -40521,6 +41196,7 @@ static sqlite3_pcache *pcache1Create(int szPage, int szExtra, int bPurgeable){
     pCache->pGroup = pGroup;
     pCache->szPage = szPage;
     pCache->szExtra = szExtra;
+    pCache->szAlloc = szPage + szExtra + ROUND8(sizeof(PgHdr1));
     pCache->bPurgeable = (bPurgeable ? 1 : 0);
     pcache1EnterMutex(pGroup);
     pcache1ResizeHash(pCache);
@@ -40552,7 +41228,7 @@ static void pcache1Cachesize(sqlite3_pcache *p, int nMax){
     pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
     pCache->nMax = nMax;
     pCache->n90pct = pCache->nMax*9/10;
-    pcache1EnforceMaxPage(pGroup);
+    pcache1EnforceMaxPage(pCache);
     pcache1LeaveMutex(pGroup);
   }
 }
@@ -40570,7 +41246,7 @@ static void pcache1Shrink(sqlite3_pcache *p){
     pcache1EnterMutex(pGroup);
     savedMaxPage = pGroup->nMaxPage;
     pGroup->nMaxPage = 0;
-    pcache1EnforceMaxPage(pGroup);
+    pcache1EnforceMaxPage(pCache);
     pGroup->nMaxPage = savedMaxPage;
     pcache1LeaveMutex(pGroup);
   }
@@ -40623,26 +41299,17 @@ static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
   assert( pCache->nHash>0 && pCache->apHash );
 
   /* Step 4. Try to recycle a page. */
-  if( pCache->bPurgeable && pGroup->pLruTail && (
-         (pCache->nPage+1>=pCache->nMax)
-      || pGroup->nCurrentPage>=pGroup->nMaxPage
-      || pcache1UnderMemoryPressure(pCache)
-  )){
+  if( pCache->bPurgeable
+   && pGroup->pLruTail
+   && ((pCache->nPage+1>=pCache->nMax) || pcache1UnderMemoryPressure(pCache))
+  ){
     PCache1 *pOther;
     pPage = pGroup->pLruTail;
     assert( pPage->isPinned==0 );
-    pcache1RemoveFromHash(pPage);
+    pcache1RemoveFromHash(pPage, 0);
     pcache1PinPage(pPage);
     pOther = pPage->pCache;
-
-    /* We want to verify that szPage and szExtra are the same for pOther
-    ** and pCache.  Assert that we can verify this by comparing sums. */
-    assert( (pCache->szPage & (pCache->szPage-1))==0 && pCache->szPage>=512 );
-    assert( pCache->szExtra<512 );
-    assert( (pOther->szPage & (pOther->szPage-1))==0 && pOther->szPage>=512 );
-    assert( pOther->szExtra<512 );
-
-    if( pOther->szPage+pOther->szExtra != pCache->szPage+pCache->szExtra ){
+    if( pOther->szAlloc != pCache->szAlloc ){
       pcache1FreePage(pPage);
       pPage = 0;
     }else{
@@ -40654,9 +41321,9 @@ static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
   ** attempt to allocate a new one. 
   */
   if( !pPage ){
-    if( createFlag==1 ) sqlite3BeginBenignMalloc();
+    if( createFlag==1 ){ sqlite3BeginBenignMalloc(); }
     pPage = pcache1AllocPage(pCache);
-    if( createFlag==1 ) sqlite3EndBenignMalloc();
+    if( createFlag==1 ){ sqlite3EndBenignMalloc(); }
   }
 
   if( pPage ){
@@ -40730,8 +41397,13 @@ static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
 **      proceed to step 5. 
 **
 **   5. Otherwise, allocate and return a new page buffer.
+**
+** There are two versions of this routine.  pcache1FetchWithMutex() is
+** the general case.  pcache1FetchNoMutex() is a faster implementation for
+** the common case where pGroup->mutex is NULL.  The pcache1Fetch() wrapper
+** invokes the appropriate routine.
 */
-static sqlite3_pcache_page *pcache1Fetch(
+static PgHdr1 *pcache1FetchNoMutex(
   sqlite3_pcache *p, 
   unsigned int iKey, 
   int createFlag
@@ -40739,28 +41411,63 @@ static sqlite3_pcache_page *pcache1Fetch(
   PCache1 *pCache = (PCache1 *)p;
   PgHdr1 *pPage = 0;
 
-  assert( offsetof(PgHdr1,page)==0 );
-  assert( pCache->bPurgeable || createFlag!=1 );
-  assert( pCache->bPurgeable || pCache->nMin==0 );
-  assert( pCache->bPurgeable==0 || pCache->nMin==10 );
-  assert( pCache->nMin==0 || pCache->bPurgeable );
-  assert( pCache->nHash>0 );
-  pcache1EnterMutex(pCache->pGroup);
-
   /* Step 1: Search the hash table for an existing entry. */
   pPage = pCache->apHash[iKey % pCache->nHash];
   while( pPage && pPage->iKey!=iKey ){ pPage = pPage->pNext; }
 
   /* Step 2: Abort if no existing page is found and createFlag is 0 */
   if( pPage ){
-    if( !pPage->isPinned ) pcache1PinPage(pPage);
+    if( !pPage->isPinned ){
+      return pcache1PinPage(pPage);
+    }else{
+      return pPage;
+    }
   }else if( createFlag ){
     /* Steps 3, 4, and 5 implemented by this subroutine */
-    pPage = pcache1FetchStage2(pCache, iKey, createFlag);
+    return pcache1FetchStage2(pCache, iKey, createFlag);
+  }else{
+    return 0;
   }
+}
+#if PCACHE1_MIGHT_USE_GROUP_MUTEX
+static PgHdr1 *pcache1FetchWithMutex(
+  sqlite3_pcache *p, 
+  unsigned int iKey, 
+  int createFlag
+){
+  PCache1 *pCache = (PCache1 *)p;
+  PgHdr1 *pPage;
+
+  pcache1EnterMutex(pCache->pGroup);
+  pPage = pcache1FetchNoMutex(p, iKey, createFlag);
   assert( pPage==0 || pCache->iMaxKey>=iKey );
   pcache1LeaveMutex(pCache->pGroup);
-  return (sqlite3_pcache_page*)pPage;
+  return pPage;
+}
+#endif
+static sqlite3_pcache_page *pcache1Fetch(
+  sqlite3_pcache *p, 
+  unsigned int iKey, 
+  int createFlag
+){
+#if PCACHE1_MIGHT_USE_GROUP_MUTEX || defined(SQLITE_DEBUG)
+  PCache1 *pCache = (PCache1 *)p;
+#endif
+
+  assert( offsetof(PgHdr1,page)==0 );
+  assert( pCache->bPurgeable || createFlag!=1 );
+  assert( pCache->bPurgeable || pCache->nMin==0 );
+  assert( pCache->bPurgeable==0 || pCache->nMin==10 );
+  assert( pCache->nMin==0 || pCache->bPurgeable );
+  assert( pCache->nHash>0 );
+#if PCACHE1_MIGHT_USE_GROUP_MUTEX
+  if( pCache->pGroup->mutex ){
+    return (sqlite3_pcache_page*)pcache1FetchWithMutex(p, iKey, createFlag);
+  }else
+#endif
+  {
+    return (sqlite3_pcache_page*)pcache1FetchNoMutex(p, iKey, createFlag);
+  }
 }
 
 
@@ -40789,8 +41496,7 @@ static void pcache1Unpin(
   assert( pPage->isPinned==1 );
 
   if( reuseUnlikely || pGroup->nCurrentPage>pGroup->nMaxPage ){
-    pcache1RemoveFromHash(pPage);
-    pcache1FreePage(pPage);
+    pcache1RemoveFromHash(pPage, 1);
   }else{
     /* Add the page to the PGroup LRU list. */
     if( pGroup->pLruHead ){
@@ -40877,8 +41583,9 @@ static void pcache1Destroy(sqlite3_pcache *p){
   assert( pGroup->nMinPage >= pCache->nMin );
   pGroup->nMinPage -= pCache->nMin;
   pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-  pcache1EnforceMaxPage(pGroup);
+  pcache1EnforceMaxPage(pCache);
   pcache1LeaveMutex(pGroup);
+  sqlite3_free(pCache->pBulk);
   sqlite3_free(pCache->apHash);
   sqlite3_free(pCache);
 }
@@ -40934,7 +41641,7 @@ SQLITE_PRIVATE int sqlite3PcacheReleaseMemory(int nReq){
   int nFree = 0;
   assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
   assert( sqlite3_mutex_notheld(pcache1.mutex) );
-  if( pcache1.pStart==0 ){
+  if( sqlite3GlobalConfig.nPage==0 ){
     PgHdr1 *p;
     pcache1EnterMutex(&pcache1.grp);
     while( (nReq<0 || nFree<nReq) && ((p=pcache1.grp.pLruTail)!=0) ){
@@ -40944,8 +41651,7 @@ SQLITE_PRIVATE int sqlite3PcacheReleaseMemory(int nReq){
 #endif
       assert( p->isPinned==0 );
       pcache1PinPage(p);
-      pcache1RemoveFromHash(p);
-      pcache1FreePage(p);
+      pcache1RemoveFromHash(p, 1);
     }
     pcache1LeaveMutex(&pcache1.grp);
   }
@@ -41041,6 +41747,7 @@ SQLITE_PRIVATE void sqlite3PcacheStats(
 ** There is an added cost of O(N) when switching between TEST and
 ** SMALLEST primitives.
 */
+/* #include "sqliteInt.h" */
 
 
 /*
@@ -41510,6 +42217,7 @@ SQLITE_PRIVATE int sqlite3RowSetTest(RowSet *pRowSet, int iBatch, sqlite3_int64
 ** another is writing.
 */
 #ifndef SQLITE_OMIT_DISKIO
+/* #include "sqliteInt.h" */
 /************** Include wal.h in the middle of pager.c ***********************/
 /************** Begin file wal.h *********************************************/
 /*
@@ -41531,6 +42239,7 @@ SQLITE_PRIVATE int sqlite3RowSetTest(RowSet *pRowSet, int iBatch, sqlite3_int64
 #ifndef _WAL_H_
 #define _WAL_H_
 
+/* #include "sqliteInt.h" */
 
 /* Additional values that can be added to the sync_flags argument of
 ** sqlite3WalFrames():
@@ -42086,9 +42795,9 @@ struct PagerSavepoint {
 /*
 ** Bits of the Pager.doNotSpill flag.  See further description below.
 */
-#define SPILLFLAG_OFF         0x01      /* Never spill cache.  Set via pragma */
-#define SPILLFLAG_ROLLBACK    0x02      /* Current rolling back, so do not spill */
-#define SPILLFLAG_NOSYNC      0x04      /* Spill is ok, but do not sync */
+#define SPILLFLAG_OFF         0x01 /* Never spill cache.  Set via pragma */
+#define SPILLFLAG_ROLLBACK    0x02 /* Current rolling back, so do not spill */
+#define SPILLFLAG_NOSYNC      0x04 /* Spill is ok, but do not sync */
 
 /*
 ** An open page cache is an instance of struct Pager. A description of
@@ -42170,11 +42879,11 @@ struct PagerSavepoint {
 **   while it is being traversed by code in pager_playback().  The SPILLFLAG_OFF
 **   case is a user preference.
 ** 
-**   If the SPILLFLAG_NOSYNC bit is set, writing to the database from pagerStress()
-**   is permitted, but syncing the journal file is not. This flag is set
-**   by sqlite3PagerWrite() when the file-system sector-size is larger than
-**   the database page-size in order to prevent a journal sync from happening 
-**   in between the journalling of two pages on the same sector. 
+**   If the SPILLFLAG_NOSYNC bit is set, writing to the database from
+**   pagerStress() is permitted, but syncing the journal file is not.
+**   This flag is set by sqlite3PagerWrite() when the file-system sector-size
+**   is larger than the database page-size in order to prevent a journal sync
+**   from happening in between the journalling of two pages on the same sector. 
 **
 ** subjInMemory
 **
@@ -42277,7 +42986,7 @@ struct Pager {
   u8 doNotSpill;              /* Do not spill the cache when non-zero */
   u8 subjInMemory;            /* True to use in-memory sub-journals */
   u8 bUseFetch;               /* True to use xFetch() */
-  u8 hasBeenUsed;             /* True if any content previously read from this pager*/
+  u8 hasBeenUsed;             /* True if any content previously read */
   Pgno dbSize;                /* Number of pages in the database */
   Pgno dbOrigSize;            /* dbSize before the current transaction */
   Pgno dbFileSize;            /* Number of pages in the database file */
@@ -42438,7 +43147,7 @@ static const unsigned char aJournalMagic[] = {
 **
 **   if( pPager->jfd->pMethods ){ ...
 */
-#define isOpen(pFd) ((pFd)->pMethods)
+#define isOpen(pFd) ((pFd)->pMethods!=0)
 
 /*
 ** Return true if this pager uses a write-ahead log instead of the usual
@@ -42661,19 +43370,21 @@ static int subjRequiresPage(PgHdr *pPg){
   int i;
   for(i=0; i<pPager->nSavepoint; i++){
     p = &pPager->aSavepoint[i];
-    if( p->nOrig>=pgno && 0==sqlite3BitvecTest(p->pInSavepoint, pgno) ){
+    if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
       return 1;
     }
   }
   return 0;
 }
 
+#ifdef SQLITE_DEBUG
 /*
 ** Return true if the page is already in the journal file.
 */
 static int pageInJournal(Pager *pPager, PgHdr *pPg){
   return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
 }
+#endif
 
 /*
 ** Read a 32-bit integer from the given file descriptor.  Store the integer
@@ -43285,7 +43996,8 @@ static int writeMasterJournal(Pager *pPager, const char *zMaster){
    || (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4)))
    || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster)))
    || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum)))
-   || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nMaster+8)))
+   || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8,
+                                 iHdrOff+4+nMaster+8)))
   ){
     return rc;
   }
@@ -43845,7 +44557,7 @@ static int pager_playback_one_page(
     }
   }
 
-  /* If this page has already been played by before during the current
+  /* If this page has already been played back before during the current
   ** rollback, then don't bother to play it back again.
   */
   if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
@@ -44779,11 +45491,10 @@ static int pagerPagecount(Pager *pPager, Pgno *pnPage){
   assert( pPager->eLock>=SHARED_LOCK );
   nPage = sqlite3WalDbsize(pPager->pWal);
 
-  /* If the database size was not available from the WAL sub-system,
-  ** determine it based on the size of the database file. If the size
-  ** of the database file is not an integer multiple of the page-size,
-  ** round down to the nearest page. Except, any file larger than 0
-  ** bytes in size is considered to contain at least one page.
+  /* If the number of pages in the database is not available from the
+  ** WAL sub-system, determine the page counte based on the size of
+  ** the database file.  If the size of the database file is not an
+  ** integer multiple of the page-size, round up the result.
   */
   if( nPage==0 ){
     i64 n = 0;                    /* Size of db file in bytes */
@@ -45948,8 +46659,6 @@ static int openSubJournal(Pager *pPager){
 
 /*
 ** Append a record of the current state of page pPg to the sub-journal. 
-** It is the callers responsibility to use subjRequiresPage() to check 
-** that it is really required before calling this function.
 **
 ** If successful, set the bit corresponding to pPg->pgno in the bitvecs
 ** for all open savepoints before returning.
@@ -45996,6 +46705,13 @@ static int subjournalPage(PgHdr *pPg){
   }
   return rc;
 }
+static int subjournalPageIfRequired(PgHdr *pPg){
+  if( subjRequiresPage(pPg) ){
+    return subjournalPage(pPg);
+  }else{
+    return SQLITE_OK;
+  }
+}
 
 /*
 ** This function is called by the pcache layer when it has reached some
@@ -46053,9 +46769,7 @@ static int pagerStress(void *p, PgHdr *pPg){
   pPg->pDirty = 0;
   if( pagerUseWal(pPager) ){
     /* Write a single frame for this page to the log. */
-    if( subjRequiresPage(pPg) ){ 
-      rc = subjournalPage(pPg); 
-    }
+    rc = subjournalPageIfRequired(pPg); 
     if( rc==SQLITE_OK ){
       rc = pagerWalFrames(pPager, pPg, 0, 0);
     }
@@ -46068,39 +46782,6 @@ static int pagerStress(void *p, PgHdr *pPg){
       rc = syncJournal(pPager, 1);
     }
   
-    /* If the page number of this page is larger than the current size of
-    ** the database image, it may need to be written to the sub-journal.
-    ** This is because the call to pager_write_pagelist() below will not
-    ** actually write data to the file in this case.
-    **
-    ** Consider the following sequence of events:
-    **
-    **   BEGIN;
-    **     <journal page X>
-    **     <modify page X>
-    **     SAVEPOINT sp;
-    **       <shrink database file to Y pages>
-    **       pagerStress(page X)
-    **     ROLLBACK TO sp;
-    **
-    ** If (X>Y), then when pagerStress is called page X will not be written
-    ** out to the database file, but will be dropped from the cache. Then,
-    ** following the "ROLLBACK TO sp" statement, reading page X will read
-    ** data from the database file. This will be the copy of page X as it
-    ** was when the transaction started, not as it was when "SAVEPOINT sp"
-    ** was executed.
-    **
-    ** The solution is to write the current data for page X into the 
-    ** sub-journal file now (if it is not already there), so that it will
-    ** be restored to its current value when the "ROLLBACK TO sp" is 
-    ** executed.
-    */
-    if( NEVER(
-        rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg)
-    ) ){
-      rc = subjournalPage(pPg);
-    }
-  
     /* Write the contents of the page out to the database file. */
     if( rc==SQLITE_OK ){
       assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
@@ -46356,7 +47037,7 @@ SQLITE_PRIVATE int sqlite3PagerOpen(
 act_like_temp_file:
     tempFile = 1;
     pPager->eState = PAGER_READER;     /* Pretend we already have a lock */
-    pPager->eLock = EXCLUSIVE_LOCK;    /* Pretend we are in EXCLUSIVE locking mode */
+    pPager->eLock = EXCLUSIVE_LOCK;    /* Pretend we are in EXCLUSIVE mode */
     pPager->noLock = 1;                /* Do no locking */
     readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
   }
@@ -46375,7 +47056,7 @@ act_like_temp_file:
     assert( nExtra<1000 );
     nExtra = ROUND8(nExtra);
     rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
-                           !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
+                       !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
   }
 
   /* If an error occurred above, free the  Pager structure and close the file.
@@ -46762,7 +47443,7 @@ SQLITE_PRIVATE int sqlite3PagerSharedLock(Pager *pPager){
       ** occurring on the very first access to a file, in order to save a
       ** single unnecessary sqlite3OsRead() call at the start-up.
       **
-      ** Database changes is detected by looking at 15 bytes beginning
+      ** Database changes are detected by looking at 15 bytes beginning
       ** at offset 24 into the file.  The first 4 of these 16 bytes are
       ** a 32-bit counter that is incremented with each change.  The
       ** other bytes change randomly with each file change when
@@ -46970,9 +47651,14 @@ SQLITE_PRIVATE int sqlite3PagerAcquire(
       if( pBase==0 ){
         rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
         if( rc!=SQLITE_OK ) goto pager_acquire_err;
+        if( pBase==0 ){
+          pPg = *ppPage = 0;
+          rc = SQLITE_NOMEM;
+          goto pager_acquire_err;
+        }
       }
       pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
-      if( pPg==0 ) rc = SQLITE_NOMEM;
+      assert( pPg!=0 );
     }
   }
 
@@ -46983,10 +47669,11 @@ SQLITE_PRIVATE int sqlite3PagerAcquire(
     pPg = 0;
     goto pager_acquire_err;
   }
-  assert( (*ppPage)->pgno==pgno );
-  assert( (*ppPage)->pPager==pPager || (*ppPage)->pPager==0 );
+  assert( pPg==(*ppPage) );
+  assert( pPg->pgno==pgno );
+  assert( pPg->pPager==pPager || pPg->pPager==0 );
 
-  if( (*ppPage)->pPager && !noContent ){
+  if( pPg->pPager && !noContent ){
     /* In this case the pcache already contains an initialized copy of
     ** the page. Return without further ado.  */
     assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
@@ -46997,7 +47684,6 @@ SQLITE_PRIVATE int sqlite3PagerAcquire(
     /* The pager cache has created a new page. Its content needs to 
     ** be initialized.  */
 
-    pPg = *ppPage;
     pPg->pPager = pPager;
 
     /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
@@ -47076,6 +47762,7 @@ SQLITE_PRIVATE DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
   assert( pPager->pPCache!=0 );
   pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
   assert( pPage==0 || pPager->hasBeenUsed );
+  if( pPage==0 ) return 0;
   return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
 }
 
@@ -47279,6 +47966,59 @@ SQLITE_PRIVATE int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory
   return rc;
 }
 
+/*
+** Write page pPg onto the end of the rollback journal.
+*/
+static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  int rc;
+  u32 cksum;
+  char *pData2;
+  i64 iOff = pPager->journalOff;
+
+  /* We should never write to the journal file the page that
+  ** contains the database locks.  The following assert verifies
+  ** that we do not. */
+  assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
+
+  assert( pPager->journalHdr<=pPager->journalOff );
+  CODEC2(pPager, pPg->pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
+  cksum = pager_cksum(pPager, (u8*)pData2);
+
+  /* Even if an IO or diskfull error occurs while journalling the
+  ** page in the block above, set the need-sync flag for the page.
+  ** Otherwise, when the transaction is rolled back, the logic in
+  ** playback_one_page() will think that the page needs to be restored
+  ** in the database file. And if an IO error occurs while doing so,
+  ** then corruption may follow.
+  */
+  pPg->flags |= PGHDR_NEED_SYNC;
+
+  rc = write32bits(pPager->jfd, iOff, pPg->pgno);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
+  if( rc!=SQLITE_OK ) return rc;
+  rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
+  if( rc!=SQLITE_OK ) return rc;
+
+  IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
+           pPager->journalOff, pPager->pageSize));
+  PAGER_INCR(sqlite3_pager_writej_count);
+  PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
+       PAGERID(pPager), pPg->pgno, 
+       ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
+
+  pPager->journalOff += 8 + pPager->pageSize;
+  pPager->nRec++;
+  assert( pPager->pInJournal!=0 );
+  rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
+  testcase( rc==SQLITE_NOMEM );
+  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+  rc |= addToSavepointBitvecs(pPager, pPg->pgno);
+  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
+  return rc;
+}
+
 /*
 ** Mark a single data page as writeable. The page is written into the 
 ** main journal or sub-journal as required. If the page is written into
@@ -47289,7 +48029,6 @@ SQLITE_PRIVATE int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory
 static int pager_write(PgHdr *pPg){
   Pager *pPager = pPg->pPager;
   int rc = SQLITE_OK;
-  int inJournal;
 
   /* This routine is not called unless a write-transaction has already 
   ** been started. The journal file may or may not be open at this point.
@@ -47302,7 +48041,6 @@ static int pager_write(PgHdr *pPg){
   assert( assert_pager_state(pPager) );
   assert( pPager->errCode==0 );
   assert( pPager->readOnly==0 );
-
   CHECK_PAGE(pPg);
 
   /* The journal file needs to be opened. Higher level routines have already
@@ -47321,91 +48059,48 @@ static int pager_write(PgHdr *pPg){
   assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
   assert( assert_pager_state(pPager) );
 
-  /* Mark the page as dirty.  If the page has already been written
-  ** to the journal then we can return right away.
-  */
+  /* Mark the page that is about to be modified as dirty. */
   sqlite3PcacheMakeDirty(pPg);
-  inJournal = pageInJournal(pPager, pPg);
-  if( inJournal && (pPager->nSavepoint==0 || !subjRequiresPage(pPg)) ){
-    assert( !pagerUseWal(pPager) );
-  }else{
-  
-    /* The transaction journal now exists and we have a RESERVED or an
-    ** EXCLUSIVE lock on the main database file.  Write the current page to
-    ** the transaction journal if it is not there already.
-    */
-    if( !inJournal && !pagerUseWal(pPager) ){
-      assert( pagerUseWal(pPager)==0 );
-      if( pPg->pgno<=pPager->dbOrigSize && isOpen(pPager->jfd) ){
-        u32 cksum;
-        char *pData2;
-        i64 iOff = pPager->journalOff;
-
-        /* We should never write to the journal file the page that
-        ** contains the database locks.  The following assert verifies
-        ** that we do not. */
-        assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
-
-        assert( pPager->journalHdr<=pPager->journalOff );
-        CODEC2(pPager, pPg->pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-        cksum = pager_cksum(pPager, (u8*)pData2);
-
-        /* Even if an IO or diskfull error occurs while journalling the
-        ** page in the block above, set the need-sync flag for the page.
-        ** Otherwise, when the transaction is rolled back, the logic in
-        ** playback_one_page() will think that the page needs to be restored
-        ** in the database file. And if an IO error occurs while doing so,
-        ** then corruption may follow.
-        */
-        pPg->flags |= PGHDR_NEED_SYNC;
 
-        rc = write32bits(pPager->jfd, iOff, pPg->pgno);
-        if( rc!=SQLITE_OK ) return rc;
-        rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
-        if( rc!=SQLITE_OK ) return rc;
-        rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
-        if( rc!=SQLITE_OK ) return rc;
-
-        IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
-                 pPager->journalOff, pPager->pageSize));
-        PAGER_INCR(sqlite3_pager_writej_count);
-        PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
-             PAGERID(pPager), pPg->pgno, 
-             ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
-
-        pPager->journalOff += 8 + pPager->pageSize;
-        pPager->nRec++;
-        assert( pPager->pInJournal!=0 );
-        rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
-        testcase( rc==SQLITE_NOMEM );
-        assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-        rc |= addToSavepointBitvecs(pPager, pPg->pgno);
-        if( rc!=SQLITE_OK ){
-          assert( rc==SQLITE_NOMEM );
-          return rc;
-        }
-      }else{
-        if( pPager->eState!=PAGER_WRITER_DBMOD ){
-          pPg->flags |= PGHDR_NEED_SYNC;
-        }
-        PAGERTRACE(("APPEND %d page %d needSync=%d\n",
-                PAGERID(pPager), pPg->pgno,
-               ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
+  /* If a rollback journal is in use, them make sure the page that is about
+  ** to change is in the rollback journal, or if the page is a new page off
+  ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
+  */
+  assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
+  if( pPager->pInJournal!=0
+   && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0
+  ){
+    assert( pagerUseWal(pPager)==0 );
+    if( pPg->pgno<=pPager->dbOrigSize ){
+      rc = pagerAddPageToRollbackJournal(pPg);
+      if( rc!=SQLITE_OK ){
+        return rc;
       }
-    }
-  
-    /* If the statement journal is open and the page is not in it,
-    ** then write the current page to the statement journal.  Note that
-    ** the statement journal format differs from the standard journal format
-    ** in that it omits the checksums and the header.
-    */
-    if( pPager->nSavepoint>0 && subjRequiresPage(pPg) ){
-      rc = subjournalPage(pPg);
+    }else{
+      if( pPager->eState!=PAGER_WRITER_DBMOD ){
+        pPg->flags |= PGHDR_NEED_SYNC;
+      }
+      PAGERTRACE(("APPEND %d page %d needSync=%d\n",
+              PAGERID(pPager), pPg->pgno,
+             ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
     }
   }
 
-  /* Update the database size and return.
+  /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list
+  ** and before writing the page into the rollback journal.  Wait until now,
+  ** after the page has been successfully journalled, before setting the
+  ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified.
+  */
+  pPg->flags |= PGHDR_WRITEABLE;
+  
+  /* If the statement journal is open and the page is not in it,
+  ** then write the page into the statement journal.
   */
+  if( pPager->nSavepoint>0 ){
+    rc = subjournalPageIfRequired(pPg);
+  }
+
+  /* Update the database size and return. */
   if( pPager->dbSize<pPg->pgno ){
     pPager->dbSize = pPg->pgno;
   }
@@ -47420,17 +48115,17 @@ static int pager_write(PgHdr *pPg){
 ** a write.
 **
 ** Usually, the sector size is less than or equal to the page size, in which
-** case pages can be individually written.  This routine only runs in the exceptional
-** case where the page size is smaller than the sector size.
+** case pages can be individually written.  This routine only runs in the
+** exceptional case where the page size is smaller than the sector size.
 */
 static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
-  int rc = SQLITE_OK;            /* Return code */
-  Pgno nPageCount;               /* Total number of pages in database file */
-  Pgno pg1;                      /* First page of the sector pPg is located on. */
-  int nPage = 0;                 /* Number of pages starting at pg1 to journal */
-  int ii;                        /* Loop counter */
-  int needSync = 0;              /* True if any page has PGHDR_NEED_SYNC */
-  Pager *pPager = pPg->pPager;   /* The pager that owns pPg */
+  int rc = SQLITE_OK;          /* Return code */
+  Pgno nPageCount;             /* Total number of pages in database file */
+  Pgno pg1;                    /* First page of the sector pPg is located on. */
+  int nPage = 0;               /* Number of pages starting at pg1 to journal */
+  int ii;                      /* Loop counter */
+  int needSync = 0;            /* True if any page has PGHDR_NEED_SYNC */
+  Pager *pPager = pPg->pPager; /* The pager that owns pPg */
   Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
 
   /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow
@@ -47518,11 +48213,15 @@ static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
 ** as appropriate. Otherwise, SQLITE_OK.
 */
 SQLITE_PRIVATE int sqlite3PagerWrite(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
   assert( (pPg->flags & PGHDR_MMAP)==0 );
-  assert( pPg->pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( pPg->pPager->eState!=PAGER_ERROR );
-  assert( assert_pager_state(pPg->pPager) );
-  if( pPg->pPager->sectorSize > (u32)pPg->pPager->pageSize ){
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( pPager->eState!=PAGER_ERROR );
+  assert( assert_pager_state(pPager) );
+  if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){
+    if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg);
+    return SQLITE_OK;
+  }else if( pPager->sectorSize > (u32)pPager->pageSize ){
     return pagerWriteLargeSector(pPg);
   }else{
     return pager_write(pPg);
@@ -47536,7 +48235,7 @@ SQLITE_PRIVATE int sqlite3PagerWrite(PgHdr *pPg){
 */
 #ifndef NDEBUG
 SQLITE_PRIVATE int sqlite3PagerIswriteable(DbPage *pPg){
-  return pPg->flags&PGHDR_DIRTY;
+  return pPg->flags & PGHDR_WRITEABLE;
 }
 #endif
 
@@ -47560,6 +48259,7 @@ SQLITE_PRIVATE void sqlite3PagerDontWrite(PgHdr *pPg){
     PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
     IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
     pPg->flags |= PGHDR_DONT_WRITE;
+    pPg->flags &= ~PGHDR_WRITEABLE;
     pager_set_pagehash(pPg);
   }
 }
@@ -48026,12 +48726,14 @@ SQLITE_PRIVATE u8 sqlite3PagerIsreadonly(Pager *pPager){
   return pPager->readOnly;
 }
 
+#ifdef SQLITE_DEBUG
 /*
 ** Return the number of references to the pager.
 */
 SQLITE_PRIVATE int sqlite3PagerRefcount(Pager *pPager){
   return sqlite3PcacheRefCount(pPager->pPCache);
 }
+#endif
 
 /*
 ** Return the approximate number of bytes of memory currently
@@ -48114,54 +48816,62 @@ SQLITE_PRIVATE int sqlite3PagerIsMemdb(Pager *pPager){
 ** occurs while opening the sub-journal file, then an IO error code is
 ** returned. Otherwise, SQLITE_OK.
 */
-SQLITE_PRIVATE int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
+static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
   int rc = SQLITE_OK;                       /* Return code */
   int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */
+  int ii;                                   /* Iterator variable */
+  PagerSavepoint *aNew;                     /* New Pager.aSavepoint array */
 
   assert( pPager->eState>=PAGER_WRITER_LOCKED );
   assert( assert_pager_state(pPager) );
+  assert( nSavepoint>nCurrent && pPager->useJournal );
 
-  if( nSavepoint>nCurrent && pPager->useJournal ){
-    int ii;                                 /* Iterator variable */
-    PagerSavepoint *aNew;                   /* New Pager.aSavepoint array */
+  /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
+  ** if the allocation fails. Otherwise, zero the new portion in case a 
+  ** malloc failure occurs while populating it in the for(...) loop below.
+  */
+  aNew = (PagerSavepoint *)sqlite3Realloc(
+      pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
+  );
+  if( !aNew ){
+    return SQLITE_NOMEM;
+  }
+  memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
+  pPager->aSavepoint = aNew;
 
-    /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
-    ** if the allocation fails. Otherwise, zero the new portion in case a 
-    ** malloc failure occurs while populating it in the for(...) loop below.
-    */
-    aNew = (PagerSavepoint *)sqlite3Realloc(
-        pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
-    );
-    if( !aNew ){
+  /* Populate the PagerSavepoint structures just allocated. */
+  for(ii=nCurrent; ii<nSavepoint; ii++){
+    aNew[ii].nOrig = pPager->dbSize;
+    if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
+      aNew[ii].iOffset = pPager->journalOff;
+    }else{
+      aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
+    }
+    aNew[ii].iSubRec = pPager->nSubRec;
+    aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
+    if( !aNew[ii].pInSavepoint ){
       return SQLITE_NOMEM;
     }
-    memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
-    pPager->aSavepoint = aNew;
-
-    /* Populate the PagerSavepoint structures just allocated. */
-    for(ii=nCurrent; ii<nSavepoint; ii++){
-      aNew[ii].nOrig = pPager->dbSize;
-      if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
-        aNew[ii].iOffset = pPager->journalOff;
-      }else{
-        aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
-      }
-      aNew[ii].iSubRec = pPager->nSubRec;
-      aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
-      if( !aNew[ii].pInSavepoint ){
-        return SQLITE_NOMEM;
-      }
-      if( pagerUseWal(pPager) ){
-        sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
-      }
-      pPager->nSavepoint = ii+1;
+    if( pagerUseWal(pPager) ){
+      sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
     }
-    assert( pPager->nSavepoint==nSavepoint );
-    assertTruncateConstraint(pPager);
+    pPager->nSavepoint = ii+1;
   }
-
+  assert( pPager->nSavepoint==nSavepoint );
+  assertTruncateConstraint(pPager);
   return rc;
 }
+SQLITE_PRIVATE int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
+  assert( pPager->eState>=PAGER_WRITER_LOCKED );
+  assert( assert_pager_state(pPager) );
+
+  if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
+    return pagerOpenSavepoint(pPager, nSavepoint);
+  }else{
+    return SQLITE_OK;
+  }
+}
+
 
 /*
 ** This function is called to rollback or release (commit) a savepoint.
@@ -48392,9 +49102,8 @@ SQLITE_PRIVATE int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, i
   ** one or more savepoint bitvecs. This is the reason this function
   ** may return SQLITE_NOMEM.
   */
-  if( pPg->flags&PGHDR_DIRTY
-   && subjRequiresPage(pPg)
-   && SQLITE_OK!=(rc = subjournalPage(pPg))
+  if( (pPg->flags & PGHDR_DIRTY)!=0
+   && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg))
   ){
     return rc;
   }
@@ -49145,6 +49854,7 @@ SQLITE_PRIVATE int sqlite3PagerWalFramesize(Pager *pPager){
 */
 #ifndef SQLITE_OMIT_WAL
 
+/* #include "wal.h" */
 
 /*
 ** Trace output macros
@@ -49550,9 +50260,9 @@ static void walIndexWriteHdr(Wal *pWal){
   pWal->hdr.isInit = 1;
   pWal->hdr.iVersion = WALINDEX_MAX_VERSION;
   walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
-  memcpy((void *)&aHdr[1], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+  memcpy((void*)&aHdr[1], (const void*)&pWal->hdr, sizeof(WalIndexHdr));
   walShmBarrier(pWal);
-  memcpy((void *)&aHdr[0], (void *)&pWal->hdr, sizeof(WalIndexHdr));
+  memcpy((void*)&aHdr[0], (const void*)&pWal->hdr, sizeof(WalIndexHdr));
 }
 
 /*
@@ -49854,13 +50564,13 @@ static void walCleanupHash(Wal *pWal){
   ** via the hash table even after the cleanup.
   */
   if( iLimit ){
-    int i;           /* Loop counter */
+    int j;           /* Loop counter */
     int iKey;        /* Hash key */
-    for(i=1; i<=iLimit; i++){
-      for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
-        if( aHash[iKey]==i ) break;
+    for(j=1; j<=iLimit; j++){
+      for(iKey=walHash(aPgno[j]); aHash[iKey]; iKey=walNextHash(iKey)){
+        if( aHash[iKey]==j ) break;
       }
-      assert( aHash[iKey]==i );
+      assert( aHash[iKey]==j );
     }
   }
 #endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
@@ -50362,7 +51072,7 @@ static void walMergesort(
   int nMerge = 0;                 /* Number of elements in list aMerge */
   ht_slot *aMerge = 0;            /* List to be merged */
   int iList;                      /* Index into input list */
-  int iSub = 0;                   /* Index into aSub array */
+  u32 iSub = 0;                   /* Index into aSub array */
   struct Sublist aSub[13];        /* Array of sub-lists */
 
   memset(aSub, 0, sizeof(aSub));
@@ -50373,7 +51083,9 @@ static void walMergesort(
     nMerge = 1;
     aMerge = &aList[iList];
     for(iSub=0; iList & (1<<iSub); iSub++){
-      struct Sublist *p = &aSub[iSub];
+      struct Sublist *p;
+      assert( iSub<ArraySize(aSub) );
+      p = &aSub[iSub];
       assert( p->aList && p->nList<=(1<<iSub) );
       assert( p->aList==&aList[iList&~((2<<iSub)-1)] );
       walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
@@ -50384,7 +51096,9 @@ static void walMergesort(
 
   for(iSub++; iSub<ArraySize(aSub); iSub++){
     if( nList & (1<<iSub) ){
-      struct Sublist *p = &aSub[iSub];
+      struct Sublist *p;
+      assert( iSub<ArraySize(aSub) );
+      p = &aSub[iSub];
       assert( p->nList<=(1<<iSub) );
       assert( p->aList==&aList[nList&~((2<<iSub)-1)] );
       walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
@@ -52295,6 +53009,7 @@ SQLITE_PRIVATE int sqlite3WalFramesize(Wal *pWal){
 **      4     Number of leaf pointers on this page
 **      *     zero or more pages numbers of leaves
 */
+/* #include "sqliteInt.h" */
 
 
 /* The following value is the maximum cell size assuming a maximum page
@@ -52312,6 +53027,7 @@ SQLITE_PRIVATE int sqlite3WalFramesize(Wal *pWal){
 /* Forward declarations */
 typedef struct MemPage MemPage;
 typedef struct BtLock BtLock;
+typedef struct CellInfo CellInfo;
 
 /*
 ** This is a magic string that appears at the beginning of every
@@ -52375,7 +53091,10 @@ struct MemPage {
   u8 *aData;           /* Pointer to disk image of the page data */
   u8 *aDataEnd;        /* One byte past the end of usable data */
   u8 *aCellIdx;        /* The cell index area */
+  u8 *aDataOfst;       /* Same as aData for leaves.  aData+4 for interior */
   DbPage *pDbPage;     /* Pager page handle */
+  u16 (*xCellSize)(MemPage*,u8*);             /* cellSizePtr method */
+  void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */
   Pgno pgno;           /* Page number for this page */
 };
 
@@ -52431,6 +53150,7 @@ struct Btree {
   u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
   u8 sharable;       /* True if we can share pBt with another db */
   u8 locked;         /* True if db currently has pBt locked */
+  u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
   int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
   int nBackup;       /* Number of backup operations reading this btree */
   u32 iDataVersion;  /* Combines with pBt->pPager->iDataVersion */
@@ -52541,7 +53261,6 @@ struct BtShared {
 ** about a cell.  The parseCellPtr() function fills in this structure
 ** based on information extract from the raw disk page.
 */
-typedef struct CellInfo CellInfo;
 struct CellInfo {
   i64 nKey;      /* The key for INTKEY tables, or nPayload otherwise */
   u8 *pPayload;  /* Pointer to the start of payload */
@@ -52584,8 +53303,7 @@ struct CellInfo {
 struct BtCursor {
   Btree *pBtree;            /* The Btree to which this cursor belongs */
   BtShared *pBt;            /* The BtShared this cursor points to */
-  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */
-  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
+  BtCursor *pNext;          /* Forms a linked list of all cursors */
   Pgno *aOverflow;          /* Cache of overflow page locations */
   CellInfo info;            /* A parse of the cell we are pointing at */
   i64 nKey;                 /* Size of pKey, or last integer key */
@@ -52595,9 +53313,16 @@ struct BtCursor {
   int skipNext;    /* Prev() is noop if negative. Next() is noop if positive.
                    ** Error code if eState==CURSOR_FAULT */
   u8 curFlags;              /* zero or more BTCF_* flags defined below */
+  u8 curPagerFlags;         /* Flags to send to sqlite3PagerAcquire() */
   u8 eState;                /* One of the CURSOR_XXX constants (see below) */
-  u8 hints;                             /* As configured by CursorSetHints() */
-  i16 iPage;                            /* Index of current page in apPage */
+  u8 hints;                 /* As configured by CursorSetHints() */
+  /* All fields above are zeroed when the cursor is allocated.  See
+  ** sqlite3BtreeCursorZero().  Fields that follow must be manually
+  ** initialized. */
+  i8 iPage;                 /* Index of current page in apPage */
+  u8 curIntKey;             /* Value of apPage[0]->intKey */
+  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
+  void *padding1;           /* Make object size a multiple of 16 */
   u16 aiIdx[BTCURSOR_MAX_DEPTH];        /* Current index in apPage[i] */
   MemPage *apPage[BTCURSOR_MAX_DEPTH];  /* Pages from root to current page */
 };
@@ -52610,6 +53335,7 @@ struct BtCursor {
 #define BTCF_ValidOvfl    0x04   /* True if aOverflow is valid */
 #define BTCF_AtLast       0x08   /* Cursor is pointing ot the last entry */
 #define BTCF_Incrblob     0x10   /* True if an incremental I/O handle */
+#define BTCF_Multiple     0x20   /* Maybe another cursor on the same btree */
 
 /*
 ** Potential values for BtCursor.eState.
@@ -52752,6 +53478,7 @@ struct IntegrityCk {
   const char *zPfx; /* Error message prefix */
   int v1, v2;       /* Values for up to two %d fields in zPfx */
   StrAccum errMsg;  /* Accumulate the error message text here */
+  u32 *heap;        /* Min-heap used for analyzing cell coverage */
 };
 
 /*
@@ -52762,6 +53489,21 @@ struct IntegrityCk {
 #define get4byte sqlite3Get4byte
 #define put4byte sqlite3Put4byte
 
+/*
+** get2byteAligned(), unlike get2byte(), requires that its argument point to a
+** two-byte aligned address.  get2bytea() is only used for accessing the
+** cell addresses in a btree header.
+*/
+#if SQLITE_BYTEORDER==4321
+# define get2byteAligned(x)  (*(u16*)(x))
+#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4008000
+# define get2byteAligned(x)  __builtin_bswap16(*(u16*)(x))
+#elif SQLITE_BYTEORDER==1234 && defined(_MSC_VER) && _MSC_VER>=1300
+# define get2byteAligned(x)  _byteswap_ushort(*(u16*)(x))
+#else
+# define get2byteAligned(x)  ((x)[0]<<8 | (x)[1])
+#endif
+
 /************** End of btreeInt.h ********************************************/
 /************** Continuing where we left off in btmutex.c ********************/
 #ifndef SQLITE_OMIT_SHARED_CACHE
@@ -53065,6 +53807,7 @@ SQLITE_PRIVATE void sqlite3BtreeEnterAll(sqlite3 *db){
 ** See the header comment on "btreeInt.h" for additional information.
 ** Including a description of file format and an overview of operation.
 */
+/* #include "btreeInt.h" */
 
 /*
 ** The header string that appears at the beginning of every
@@ -53541,13 +54284,15 @@ static void invalidateIncrblobCursors(
   int isClearTable        /* True if all rows are being deleted */
 ){
   BtCursor *p;
-  BtShared *pBt = pBtree->pBt;
+  if( pBtree->hasIncrblobCur==0 ) return;
   assert( sqlite3BtreeHoldsMutex(pBtree) );
-  for(p=pBt->pCursor; p; p=p->pNext){
-    if( (p->curFlags & BTCF_Incrblob)!=0
-     && (isClearTable || p->info.nKey==iRow)
-    ){
-      p->eState = CURSOR_INVALID;
+  pBtree->hasIncrblobCur = 0;
+  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
+    if( (p->curFlags & BTCF_Incrblob)!=0 ){
+      pBtree->hasIncrblobCur = 1;
+      if( isClearTable || p->info.nKey==iRow ){
+        p->eState = CURSOR_INVALID;
+      }
     }
   }
 }
@@ -53669,7 +54414,7 @@ static int saveCursorPosition(BtCursor *pCur){
   ** table, then malloc space for and store the pCur->nKey bytes of key 
   ** data.
   */
-  if( 0==pCur->apPage[0]->intKey ){
+  if( 0==pCur->curIntKey ){
     void *pKey = sqlite3Malloc( pCur->nKey );
     if( pKey ){
       rc = sqlite3BtreeKey(pCur, 0, (int)pCur->nKey, pKey);
@@ -53682,7 +54427,7 @@ static int saveCursorPosition(BtCursor *pCur){
       rc = SQLITE_NOMEM;
     }
   }
-  assert( !pCur->apPage[0]->intKey || !pCur->pKey );
+  assert( !pCur->curIntKey || !pCur->pKey );
 
   if( rc==SQLITE_OK ){
     btreeReleaseAllCursorPages(pCur);
@@ -53704,6 +54449,15 @@ static int SQLITE_NOINLINE saveCursorsOnList(BtCursor*,Pgno,BtCursor*);
 ** routine is called just before cursor pExcept is used to modify the
 ** table, for example in BtreeDelete() or BtreeInsert().
 **
+** If there are two or more cursors on the same btree, then all such 
+** cursors should have their BTCF_Multiple flag set.  The btreeCursor()
+** routine enforces that rule.  This routine only needs to be called in
+** the uncommon case when pExpect has the BTCF_Multiple flag set.
+**
+** If pExpect!=NULL and if no other cursors are found on the same root-page,
+** then the BTCF_Multiple flag on pExpect is cleared, to avoid another
+** pointless call to this routine.
+**
 ** Implementation note:  This routine merely checks to see if any cursors
 ** need to be saved.  It calls out to saveCursorsOnList() in the (unusual)
 ** event that cursors are in need to being saved.
@@ -53715,7 +54469,9 @@ static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
   for(p=pBt->pCursor; p; p=p->pNext){
     if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break;
   }
-  return p ? saveCursorsOnList(p, iRoot, pExcept) : SQLITE_OK;
+  if( p ) return saveCursorsOnList(p, iRoot, pExcept);
+  if( pExcept ) pExcept->curFlags &= ~BTCF_Multiple;
+  return SQLITE_OK;
 }
 
 /* This helper routine to saveAllCursors does the actual work of saving
@@ -54003,39 +54759,88 @@ static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
 ** the page, 1 means the second cell, and so forth) return a pointer
 ** to the cell content.
 **
+** findCellPastPtr() does the same except it skips past the initial
+** 4-byte child pointer found on interior pages, if there is one.
+**
 ** This routine works only for pages that do not contain overflow cells.
 */
 #define findCell(P,I) \
-  ((P)->aData + ((P)->maskPage & get2byte(&(P)->aCellIdx[2*(I)])))
-#define findCellv2(D,M,O,I) (D+(M&get2byte(D+(O+2*(I)))))
+  ((P)->aData + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
+#define findCellPastPtr(P,I) \
+  ((P)->aDataOfst + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
 
 
 /*
-** This a more complex version of findCell() that works for
-** pages that do contain overflow cells.
+** This is common tail processing for btreeParseCellPtr() and
+** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
+** on a single B-tree page.  Make necessary adjustments to the CellInfo
+** structure.
 */
-static u8 *findOverflowCell(MemPage *pPage, int iCell){
-  int i;
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  for(i=pPage->nOverflow-1; i>=0; i--){
-    int k;
-    k = pPage->aiOvfl[i];
-    if( k<=iCell ){
-      if( k==iCell ){
-        return pPage->apOvfl[i];
-      }
-      iCell--;
-    }
+static SQLITE_NOINLINE void btreeParseCellAdjustSizeForOverflow(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  /* If the payload will not fit completely on the local page, we have
+  ** to decide how much to store locally and how much to spill onto
+  ** overflow pages.  The strategy is to minimize the amount of unused
+  ** space on overflow pages while keeping the amount of local storage
+  ** in between minLocal and maxLocal.
+  **
+  ** Warning:  changing the way overflow payload is distributed in any
+  ** way will result in an incompatible file format.
+  */
+  int minLocal;  /* Minimum amount of payload held locally */
+  int maxLocal;  /* Maximum amount of payload held locally */
+  int surplus;   /* Overflow payload available for local storage */
+
+  minLocal = pPage->minLocal;
+  maxLocal = pPage->maxLocal;
+  surplus = minLocal + (pInfo->nPayload - minLocal)%(pPage->pBt->usableSize-4);
+  testcase( surplus==maxLocal );
+  testcase( surplus==maxLocal+1 );
+  if( surplus <= maxLocal ){
+    pInfo->nLocal = (u16)surplus;
+  }else{
+    pInfo->nLocal = (u16)minLocal;
   }
-  return findCell(pPage, iCell);
+  pInfo->iOverflow = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell);
+  pInfo->nSize = pInfo->iOverflow + 4;
 }
 
 /*
-** Parse a cell content block and fill in the CellInfo structure.  There
-** are two versions of this function.  btreeParseCell() takes a 
-** cell index as the second argument and btreeParseCellPtr() 
-** takes a pointer to the body of the cell as its second argument.
+** The following routines are implementations of the MemPage.xParseCell()
+** method.
+**
+** Parse a cell content block and fill in the CellInfo structure.
+**
+** btreeParseCellPtr()        =>   table btree leaf nodes
+** btreeParseCellNoPayload()  =>   table btree internal nodes
+** btreeParseCellPtrIndex()   =>   index btree nodes
+**
+** There is also a wrapper function btreeParseCell() that works for
+** all MemPage types and that references the cell by index rather than
+** by pointer.
 */
+static void btreeParseCellPtrNoPayload(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->leaf==0 );
+  assert( pPage->noPayload );
+  assert( pPage->childPtrSize==4 );
+#ifndef SQLITE_DEBUG
+  UNUSED_PARAMETER(pPage);
+#endif
+  pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
+  pInfo->nPayload = 0;
+  pInfo->nLocal = 0;
+  pInfo->iOverflow = 0;
+  pInfo->pPayload = 0;
+  return;
+}
 static void btreeParseCellPtr(
   MemPage *pPage,         /* Page containing the cell */
   u8 *pCell,              /* Pointer to the cell text. */
@@ -54043,26 +54848,93 @@ static void btreeParseCellPtr(
 ){
   u8 *pIter;              /* For scanning through pCell */
   u32 nPayload;           /* Number of bytes of cell payload */
+  u64 iKey;               /* Extracted Key value */
 
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   assert( pPage->leaf==0 || pPage->leaf==1 );
-  if( pPage->intKeyLeaf ){
-    assert( pPage->childPtrSize==0 );
-    pIter = pCell + getVarint32(pCell, nPayload);
-    pIter += getVarint(pIter, (u64*)&pInfo->nKey);
-  }else if( pPage->noPayload ){
-    assert( pPage->childPtrSize==4 );
-    pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
-    pInfo->nPayload = 0;
-    pInfo->nLocal = 0;
+  assert( pPage->intKeyLeaf || pPage->noPayload );
+  assert( pPage->noPayload==0 );
+  assert( pPage->intKeyLeaf );
+  assert( pPage->childPtrSize==0 );
+  pIter = pCell;
+
+  /* The next block of code is equivalent to:
+  **
+  **     pIter += getVarint32(pIter, nPayload);
+  **
+  ** The code is inlined to avoid a function call.
+  */
+  nPayload = *pIter;
+  if( nPayload>=0x80 ){
+    u8 *pEnd = &pIter[8];
+    nPayload &= 0x7f;
+    do{
+      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
+    }while( (*pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+
+  /* The next block of code is equivalent to:
+  **
+  **     pIter += getVarint(pIter, (u64*)&pInfo->nKey);
+  **
+  ** The code is inlined to avoid a function call.
+  */
+  iKey = *pIter;
+  if( iKey>=0x80 ){
+    u8 *pEnd = &pIter[7];
+    iKey &= 0x7f;
+    while(1){
+      iKey = (iKey<<7) | (*++pIter & 0x7f);
+      if( (*pIter)<0x80 ) break;
+      if( pIter>=pEnd ){
+        iKey = (iKey<<8) | *++pIter;
+        break;
+      }
+    }
+  }
+  pIter++;
+
+  pInfo->nKey = *(i64*)&iKey;
+  pInfo->nPayload = nPayload;
+  pInfo->pPayload = pIter;
+  testcase( nPayload==pPage->maxLocal );
+  testcase( nPayload==pPage->maxLocal+1 );
+  if( nPayload<=pPage->maxLocal ){
+    /* This is the (easy) common case where the entire payload fits
+    ** on the local page.  No overflow is required.
+    */
+    pInfo->nSize = nPayload + (u16)(pIter - pCell);
+    if( pInfo->nSize<4 ) pInfo->nSize = 4;
+    pInfo->nLocal = (u16)nPayload;
     pInfo->iOverflow = 0;
-    pInfo->pPayload = 0;
-    return;
   }else{
-    pIter = pCell + pPage->childPtrSize;
-    pIter += getVarint32(pIter, nPayload);
-    pInfo->nKey = nPayload;
+    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
   }
+}
+static void btreeParseCellPtrIndex(
+  MemPage *pPage,         /* Page containing the cell */
+  u8 *pCell,              /* Pointer to the cell text. */
+  CellInfo *pInfo         /* Fill in this structure */
+){
+  u8 *pIter;              /* For scanning through pCell */
+  u32 nPayload;           /* Number of bytes of cell payload */
+
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  assert( pPage->leaf==0 || pPage->leaf==1 );
+  assert( pPage->intKeyLeaf==0 );
+  assert( pPage->noPayload==0 );
+  pIter = pCell + pPage->childPtrSize;
+  nPayload = *pIter;
+  if( nPayload>=0x80 ){
+    u8 *pEnd = &pIter[8];
+    nPayload &= 0x7f;
+    do{
+      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
+    }while( *(pIter)>=0x80 && pIter<pEnd );
+  }
+  pIter++;
+  pInfo->nKey = nPayload;
   pInfo->nPayload = nPayload;
   pInfo->pPayload = pIter;
   testcase( nPayload==pPage->maxLocal );
@@ -54076,31 +54948,7 @@ static void btreeParseCellPtr(
     pInfo->nLocal = (u16)nPayload;
     pInfo->iOverflow = 0;
   }else{
-    /* If the payload will not fit completely on the local page, we have
-    ** to decide how much to store locally and how much to spill onto
-    ** overflow pages.  The strategy is to minimize the amount of unused
-    ** space on overflow pages while keeping the amount of local storage
-    ** in between minLocal and maxLocal.
-    **
-    ** Warning:  changing the way overflow payload is distributed in any
-    ** way will result in an incompatible file format.
-    */
-    int minLocal;  /* Minimum amount of payload held locally */
-    int maxLocal;  /* Maximum amount of payload held locally */
-    int surplus;   /* Overflow payload available for local storage */
-
-    minLocal = pPage->minLocal;
-    maxLocal = pPage->maxLocal;
-    surplus = minLocal + (nPayload - minLocal)%(pPage->pBt->usableSize - 4);
-    testcase( surplus==maxLocal );
-    testcase( surplus==maxLocal+1 );
-    if( surplus <= maxLocal ){
-      pInfo->nLocal = (u16)surplus;
-    }else{
-      pInfo->nLocal = (u16)minLocal;
-    }
-    pInfo->iOverflow = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell);
-    pInfo->nSize = pInfo->iOverflow + 4;
+    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
   }
 }
 static void btreeParseCell(
@@ -54108,14 +54956,20 @@ static void btreeParseCell(
   int iCell,              /* The cell index.  First cell is 0 */
   CellInfo *pInfo         /* Fill in this structure */
 ){
-  btreeParseCellPtr(pPage, findCell(pPage, iCell), pInfo);
+  pPage->xParseCell(pPage, findCell(pPage, iCell), pInfo);
 }
 
 /*
+** The following routines are implementations of the MemPage.xCellSize
+** method.
+**
 ** Compute the total number of bytes that a Cell needs in the cell
 ** data area of the btree-page.  The return number includes the cell
 ** data header and the local payload, but not any overflow page or
 ** the space used by the cell pointer.
+**
+** cellSizePtrNoPayload()    =>   table internal nodes
+** cellSizePtr()             =>   all index nodes & table leaf nodes
 */
 static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
   u8 *pIter = pCell + pPage->childPtrSize; /* For looping over bytes of pCell */
@@ -54128,18 +54982,13 @@ static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
   ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
   ** this function verifies that this invariant is not violated. */
   CellInfo debuginfo;
-  btreeParseCellPtr(pPage, pCell, &debuginfo);
+  pPage->xParseCell(pPage, pCell, &debuginfo);
 #endif
 
-  if( pPage->noPayload ){
-    pEnd = &pIter[9];
-    while( (*pIter++)&0x80 && pIter<pEnd );
-    assert( pPage->childPtrSize==4 );
-    return (u16)(pIter - pCell);
-  }
+  assert( pPage->noPayload==0 );
   nSize = *pIter;
   if( nSize>=0x80 ){
-    pEnd = &pIter[9];
+    pEnd = &pIter[8];
     nSize &= 0x7f;
     do{
       nSize = (nSize<<7) | (*++pIter & 0x7f);
@@ -54171,12 +55020,34 @@ static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
   assert( nSize==debuginfo.nSize || CORRUPT_DB );
   return (u16)nSize;
 }
+static u16 cellSizePtrNoPayload(MemPage *pPage, u8 *pCell){
+  u8 *pIter = pCell + 4; /* For looping over bytes of pCell */
+  u8 *pEnd;              /* End mark for a varint */
+
+#ifdef SQLITE_DEBUG
+  /* The value returned by this function should always be the same as
+  ** the (CellInfo.nSize) value found by doing a full parse of the
+  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
+  ** this function verifies that this invariant is not violated. */
+  CellInfo debuginfo;
+  pPage->xParseCell(pPage, pCell, &debuginfo);
+#else
+  UNUSED_PARAMETER(pPage);
+#endif
+
+  assert( pPage->childPtrSize==4 );
+  pEnd = pIter + 9;
+  while( (*pIter++)&0x80 && pIter<pEnd );
+  assert( debuginfo.nSize==(u16)(pIter - pCell) || CORRUPT_DB );
+  return (u16)(pIter - pCell);
+}
+
 
 #ifdef SQLITE_DEBUG
 /* This variation on cellSizePtr() is used inside of assert() statements
 ** only. */
 static u16 cellSize(MemPage *pPage, int iCell){
-  return cellSizePtr(pPage, findCell(pPage, iCell));
+  return pPage->xCellSize(pPage, findCell(pPage, iCell));
 }
 #endif
 
@@ -54190,7 +55061,7 @@ static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
   CellInfo info;
   if( *pRC ) return;
   assert( pCell!=0 );
-  btreeParseCellPtr(pPage, pCell, &info);
+  pPage->xParseCell(pPage, pCell, &info);
   if( info.iOverflow ){
     Pgno ovfl = get4byte(&pCell[info.iOverflow]);
     ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
@@ -54247,26 +55118,18 @@ static int defragmentPage(MemPage *pPage){
     pc = get2byte(pAddr);
     testcase( pc==iCellFirst );
     testcase( pc==iCellLast );
-#if !defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
     /* These conditions have already been verified in btreeInitPage()
-    ** if SQLITE_ENABLE_OVERSIZE_CELL_CHECK is defined 
+    ** if PRAGMA cell_size_check=ON.
     */
     if( pc<iCellFirst || pc>iCellLast ){
       return SQLITE_CORRUPT_BKPT;
     }
-#endif
     assert( pc>=iCellFirst && pc<=iCellLast );
-    size = cellSizePtr(pPage, &src[pc]);
+    size = pPage->xCellSize(pPage, &src[pc]);
     cbrk -= size;
-#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
-    if( cbrk<iCellFirst ){
-      return SQLITE_CORRUPT_BKPT;
-    }
-#else
     if( cbrk<iCellFirst || pc+size>usableSize ){
       return SQLITE_CORRUPT_BKPT;
     }
-#endif
     assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
     testcase( cbrk+size==usableSize );
     testcase( pc+size==usableSize );
@@ -54304,18 +55167,20 @@ static int defragmentPage(MemPage *pPage){
 ** This function may detect corruption within pPg.  If corruption is
 ** detected then *pRc is set to SQLITE_CORRUPT and NULL is returned.
 **
-** If a slot of at least nByte bytes is found but cannot be used because 
-** there are already at least 60 fragmented bytes on the page, return NULL.
-** In this case, if pbDefrag parameter is not NULL, set *pbDefrag to true.
+** Slots on the free list that are between 1 and 3 bytes larger than nByte
+** will be ignored if adding the extra space to the fragmentation count
+** causes the fragmentation count to exceed 60.
 */
-static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
+static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
   const int hdr = pPg->hdrOffset;
   u8 * const aData = pPg->aData;
-  int iAddr;
-  int pc;
+  int iAddr = hdr + 1;
+  int pc = get2byte(&aData[iAddr]);
+  int x;
   int usableSize = pPg->pBt->usableSize;
 
-  for(iAddr=hdr+1; (pc = get2byte(&aData[iAddr]))>0; iAddr=pc){
+  assert( pc>0 );
+  do{
     int size;            /* Size of the free slot */
     /* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
     ** increasing offset. */
@@ -54327,24 +55192,21 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
     ** freeblock form a big-endian integer which is the size of the freeblock
     ** in bytes, including the 4-byte header. */
     size = get2byte(&aData[pc+2]);
-    if( size>=nByte ){
-      int x = size - nByte;
+    if( (x = size - nByte)>=0 ){
       testcase( x==4 );
       testcase( x==3 );
-      if( x<4 ){
+      if( pc < pPg->cellOffset+2*pPg->nCell || size+pc > usableSize ){
+        *pRc = SQLITE_CORRUPT_BKPT;
+        return 0;
+      }else if( x<4 ){
         /* EVIDENCE-OF: R-11498-58022 In a well-formed b-tree page, the total
         ** number of bytes in fragments may not exceed 60. */
-        if( aData[hdr+7]>=60 ){
-          if( pbDefrag ) *pbDefrag = 1;
-          return 0;
-        }
+        if( aData[hdr+7]>57 ) return 0;
+
         /* Remove the slot from the free-list. Update the number of
         ** fragmented bytes within the page. */
         memcpy(&aData[iAddr], &aData[pc], 2);
         aData[hdr+7] += (u8)x;
-      }else if( size+pc > usableSize ){
-        *pRc = SQLITE_CORRUPT_BKPT;
-        return 0;
       }else{
         /* The slot remains on the free-list. Reduce its size to account
          ** for the portion used by the new allocation. */
@@ -54352,7 +55214,9 @@ static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc, int *pbDefrag){
       }
       return &aData[pc + x];
     }
-  }
+    iAddr = pc;
+    pc = get2byte(&aData[pc]);
+  }while( pc );
 
   return 0;
 }
@@ -54393,8 +55257,15 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
   ** then the cell content offset of an empty page wants to be 65536.
   ** However, that integer is too large to be stored in a 2-byte unsigned
   ** integer, so a value of 0 is used in its place. */
-  top = get2byteNotZero(&data[hdr+5]);
-  if( gap>top ) return SQLITE_CORRUPT_BKPT;
+  top = get2byte(&data[hdr+5]);
+  assert( top<=(int)pPage->pBt->usableSize ); /* Prevent by getAndInitPage() */
+  if( gap>top ){
+    if( top==0 && pPage->pBt->usableSize==65536 ){
+      top = 65536;
+    }else{
+      return SQLITE_CORRUPT_BKPT;
+    }
+  }
 
   /* If there is enough space between gap and top for one more cell pointer
   ** array entry offset, and if the freelist is not empty, then search the
@@ -54403,15 +55274,14 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
   testcase( gap+2==top );
   testcase( gap+1==top );
   testcase( gap==top );
-  if( gap+2<=top && (data[hdr+1] || data[hdr+2]) ){
-    int bDefrag = 0;
-    u8 *pSpace = pageFindSlot(pPage, nByte, &rc, &bDefrag);
-    if( rc ) return rc;
-    if( bDefrag ) goto defragment_page;
+  if( (data[hdr+2] || data[hdr+1]) && gap+2<=top ){
+    u8 *pSpace = pageFindSlot(pPage, nByte, &rc);
     if( pSpace ){
       assert( pSpace>=data && (pSpace - data)<65536 );
       *pIdx = (int)(pSpace - data);
       return SQLITE_OK;
+    }else if( rc ){
+      return rc;
     }
   }
 
@@ -54420,7 +55290,6 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
   */
   testcase( gap+2+nByte==top );
   if( gap+2+nByte>top ){
- defragment_page:
     assert( pPage->nCell>0 || CORRUPT_DB );
     rc = defragmentPage(pPage);
     if( rc ) return rc;
@@ -54467,7 +55336,7 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
 
   assert( pPage->pBt!=0 );
   assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  assert( iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
+  assert( CORRUPT_DB || iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
   assert( CORRUPT_DB || iEnd <= pPage->pBt->usableSize );
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   assert( iSize>=4 );   /* Minimum cell size is 4 */
@@ -54496,7 +55365,7 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
   
     /* At this point:
     **    iFreeBlk:   First freeblock after iStart, or zero if none
-    **    iPtr:       The address of a pointer iFreeBlk
+    **    iPtr:       The address of a pointer to iFreeBlk
     **
     ** Check to see if iFreeBlk should be coalesced onto the end of iStart.
     */
@@ -54504,6 +55373,7 @@ static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
       nFrag = iFreeBlk - iEnd;
       if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_BKPT;
       iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
+      if( iEnd > pPage->pBt->usableSize ) return SQLITE_CORRUPT_BKPT;
       iSize = iEnd - iStart;
       iFreeBlk = get2byte(&data[iFreeBlk]);
     }
@@ -54561,6 +55431,7 @@ static int decodeFlags(MemPage *pPage, int flagByte){
   pPage->leaf = (u8)(flagByte>>3);  assert( PTF_LEAF == 1<<3 );
   flagByte &= ~PTF_LEAF;
   pPage->childPtrSize = 4-4*pPage->leaf;
+  pPage->xCellSize = cellSizePtr;
   pBt = pPage->pBt;
   if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
     /* EVIDENCE-OF: R-03640-13415 A value of 5 means the page is an interior
@@ -54570,8 +55441,16 @@ static int decodeFlags(MemPage *pPage, int flagByte){
     ** table b-tree page. */
     assert( (PTF_LEAFDATA|PTF_INTKEY|PTF_LEAF)==13 );
     pPage->intKey = 1;
-    pPage->intKeyLeaf = pPage->leaf;
-    pPage->noPayload = !pPage->leaf;
+    if( pPage->leaf ){
+      pPage->intKeyLeaf = 1;
+      pPage->noPayload = 0;
+      pPage->xParseCell = btreeParseCellPtr;
+    }else{
+      pPage->intKeyLeaf = 0;
+      pPage->noPayload = 1;
+      pPage->xCellSize = cellSizePtrNoPayload;
+      pPage->xParseCell = btreeParseCellPtrNoPayload;
+    }
     pPage->maxLocal = pBt->maxLeaf;
     pPage->minLocal = pBt->minLeaf;
   }else if( flagByte==PTF_ZERODATA ){
@@ -54584,6 +55463,7 @@ static int decodeFlags(MemPage *pPage, int flagByte){
     pPage->intKey = 0;
     pPage->intKeyLeaf = 0;
     pPage->noPayload = 0;
+    pPage->xParseCell = btreeParseCellPtrIndex;
     pPage->maxLocal = pBt->maxLocal;
     pPage->minLocal = pBt->minLocal;
   }else{
@@ -54607,6 +55487,7 @@ static int decodeFlags(MemPage *pPage, int flagByte){
 static int btreeInitPage(MemPage *pPage){
 
   assert( pPage->pBt!=0 );
+  assert( pPage->pBt->db!=0 );
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
   assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
@@ -54638,6 +55519,7 @@ static int btreeInitPage(MemPage *pPage){
     pPage->cellOffset = cellOffset = hdr + 8 + pPage->childPtrSize;
     pPage->aDataEnd = &data[usableSize];
     pPage->aCellIdx = &data[cellOffset];
+    pPage->aDataOfst = &data[pPage->childPtrSize];
     /* EVIDENCE-OF: R-58015-48175 The two-byte integer at offset 5 designates
     ** the start of the cell content area. A zero value for this integer is
     ** interpreted as 65536. */
@@ -54665,20 +55547,19 @@ static int btreeInitPage(MemPage *pPage){
     */
     iCellFirst = cellOffset + 2*pPage->nCell;
     iCellLast = usableSize - 4;
-#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
-    {
+    if( pBt->db->flags & SQLITE_CellSizeCk ){
       int i;            /* Index into the cell pointer array */
       int sz;           /* Size of a cell */
 
       if( !pPage->leaf ) iCellLast--;
       for(i=0; i<pPage->nCell; i++){
-        pc = get2byte(&data[cellOffset+i*2]);
+        pc = get2byteAligned(&data[cellOffset+i*2]);
         testcase( pc==iCellFirst );
         testcase( pc==iCellLast );
         if( pc<iCellFirst || pc>iCellLast ){
           return SQLITE_CORRUPT_BKPT;
         }
-        sz = cellSizePtr(pPage, &data[pc]);
+        sz = pPage->xCellSize(pPage, &data[pc]);
         testcase( pc+sz==usableSize );
         if( pc+sz>usableSize ){
           return SQLITE_CORRUPT_BKPT;
@@ -54686,7 +55567,6 @@ static int btreeInitPage(MemPage *pPage){
       }
       if( !pPage->leaf ) iCellLast++;
     }  
-#endif
 
     /* Compute the total free space on the page
     ** EVIDENCE-OF: R-23588-34450 The two-byte integer at offset 1 gives the
@@ -54759,6 +55639,7 @@ static void zeroPage(MemPage *pPage, int flags){
   pPage->cellOffset = first;
   pPage->aDataEnd = &data[pBt->usableSize];
   pPage->aCellIdx = &data[first];
+  pPage->aDataOfst = &data[pPage->childPtrSize];
   pPage->nOverflow = 0;
   assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
   pPage->maskPage = (u16)(pBt->pageSize - 1);
@@ -54777,16 +55658,16 @@ static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
   pPage->pDbPage = pDbPage;
   pPage->pBt = pBt;
   pPage->pgno = pgno;
-  pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
+  pPage->hdrOffset = pgno==1 ? 100 : 0;
   return pPage; 
 }
 
 /*
 ** Get a page from the pager.  Initialize the MemPage.pBt and
-** MemPage.aData elements if needed.
+** MemPage.aData elements if needed.  See also: btreeGetUnusedPage().
 **
-** If the noContent flag is set, it means that we do not care about
-** the content of the page at this time.  So do not go to the disk
+** If the PAGER_GET_NOCONTENT flag is set, it means that we do not care
+** about the content of the page at this time.  So do not go to the disk
 ** to fetch the content.  Just fill in the content with zeros for now.
 ** If in the future we call sqlite3PagerWrite() on this page, that
 ** means we have started to be concerned about content and the disk
@@ -54838,35 +55719,62 @@ SQLITE_PRIVATE u32 sqlite3BtreeLastPage(Btree *p){
 }
 
 /*
-** Get a page from the pager and initialize it.  This routine is just a
-** convenience wrapper around separate calls to btreeGetPage() and 
-** btreeInitPage().
+** Get a page from the pager and initialize it.
+**
+** If pCur!=0 then the page is being fetched as part of a moveToChild()
+** call.  Do additional sanity checking on the page in this case.
+** And if the fetch fails, this routine must decrement pCur->iPage.
 **
-** If an error occurs, then the value *ppPage is set to is undefined. It
+** The page is fetched as read-write unless pCur is not NULL and is
+** a read-only cursor.
+**
+** If an error occurs, then *ppPage is undefined. It
 ** may remain unchanged, or it may be set to an invalid value.
 */
 static int getAndInitPage(
   BtShared *pBt,                  /* The database file */
   Pgno pgno,                      /* Number of the page to get */
   MemPage **ppPage,               /* Write the page pointer here */
-  int bReadonly                   /* PAGER_GET_READONLY or 0 */
+  BtCursor *pCur,                 /* Cursor to receive the page, or NULL */
+  int bReadOnly                   /* True for a read-only page */
 ){
   int rc;
+  DbPage *pDbPage;
   assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( bReadonly==PAGER_GET_READONLY || bReadonly==0 );
+  assert( pCur==0 || ppPage==&pCur->apPage[pCur->iPage] );
+  assert( pCur==0 || bReadOnly==pCur->curPagerFlags );
+  assert( pCur==0 || pCur->iPage>0 );
 
   if( pgno>btreePagecount(pBt) ){
     rc = SQLITE_CORRUPT_BKPT;
-  }else{
-    rc = btreeGetPage(pBt, pgno, ppPage, bReadonly);
-    if( rc==SQLITE_OK && (*ppPage)->isInit==0 ){
-      rc = btreeInitPage(*ppPage);
-      if( rc!=SQLITE_OK ){
-        releasePage(*ppPage);
-      }
+    goto getAndInitPage_error;
+  }
+  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadOnly);
+  if( rc ){
+    goto getAndInitPage_error;
+  }
+  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
+  if( (*ppPage)->isInit==0 ){
+    rc = btreeInitPage(*ppPage);
+    if( rc!=SQLITE_OK ){
+      releasePage(*ppPage);
+      goto getAndInitPage_error;
     }
   }
 
+  /* If obtaining a child page for a cursor, we must verify that the page is
+  ** compatible with the root page. */
+  if( pCur
+   && ((*ppPage)->nCell<1 || (*ppPage)->intKey!=pCur->curIntKey)
+  ){
+    rc = SQLITE_CORRUPT_BKPT;
+    releasePage(*ppPage);
+    goto getAndInitPage_error;
+  }
+  return SQLITE_OK;
+
+getAndInitPage_error:
+  if( pCur ) pCur->iPage--;
   testcase( pgno==0 );
   assert( pgno!=0 || rc==SQLITE_CORRUPT );
   return rc;
@@ -54876,18 +55784,49 @@ static int getAndInitPage(
 ** Release a MemPage.  This should be called once for each prior
 ** call to btreeGetPage.
 */
+static void releasePageNotNull(MemPage *pPage){
+  assert( pPage->aData );
+  assert( pPage->pBt );
+  assert( pPage->pDbPage!=0 );
+  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
+  assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
+  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+  sqlite3PagerUnrefNotNull(pPage->pDbPage);
+}
 static void releasePage(MemPage *pPage){
-  if( pPage ){
-    assert( pPage->aData );
-    assert( pPage->pBt );
-    assert( pPage->pDbPage!=0 );
-    assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
-    assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
-    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-    sqlite3PagerUnrefNotNull(pPage->pDbPage);
+  if( pPage ) releasePageNotNull(pPage);
+}
+
+/*
+** Get an unused page.
+**
+** This works just like btreeGetPage() with the addition:
+**
+**   *  If the page is already in use for some other purpose, immediately
+**      release it and return an SQLITE_CURRUPT error.
+**   *  Make sure the isInit flag is clear
+*/
+static int btreeGetUnusedPage(
+  BtShared *pBt,       /* The btree */
+  Pgno pgno,           /* Number of the page to fetch */
+  MemPage **ppPage,    /* Return the page in this parameter */
+  int flags            /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
+){
+  int rc = btreeGetPage(pBt, pgno, ppPage, flags);
+  if( rc==SQLITE_OK ){
+    if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
+      releasePage(*ppPage);
+      *ppPage = 0;
+      return SQLITE_CORRUPT_BKPT;
+    }
+    (*ppPage)->isInit = 0;
+  }else{
+    *ppPage = 0;
   }
+  return rc;
 }
 
+
 /*
 ** During a rollback, when the pager reloads information into the cache
 ** so that the cache is restored to its original state at the start of
@@ -55830,7 +56769,7 @@ static void unlockBtreeIfUnused(BtShared *pBt){
     assert( pPage1->aData );
     assert( sqlite3PagerRefcount(pBt->pPager)==1 );
     pBt->pPage1 = 0;
-    releasePage(pPage1);
+    releasePageNotNull(pPage1);
   }
 }
 
@@ -56135,15 +57074,17 @@ static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
     u8 isInitOrig = pPage->isInit;
     int i;
     int nCell;
+    int rc;
 
-    btreeInitPage(pPage);
+    rc = btreeInitPage(pPage);
+    if( rc ) return rc;
     nCell = pPage->nCell;
 
     for(i=0; i<nCell; i++){
       u8 *pCell = findCell(pPage, i);
       if( eType==PTRMAP_OVERFLOW1 ){
         CellInfo info;
-        btreeParseCellPtr(pPage, pCell, &info);
+        pPage->xParseCell(pPage, pCell, &info);
         if( info.iOverflow
          && pCell+info.iOverflow+3<=pPage->aData+pPage->maskPage
          && iFrom==get4byte(&pCell[info.iOverflow])
@@ -56442,7 +57383,7 @@ SQLITE_PRIVATE int sqlite3BtreeIncrVacuum(Btree *p){
 static int autoVacuumCommit(BtShared *pBt){
   int rc = SQLITE_OK;
   Pager *pPager = pBt->pPager;
-  VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager) );
+  VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager); )
 
   assert( sqlite3_mutex_held(pBt->mutex) );
   invalidateAllOverflowCache(pBt);
@@ -56884,6 +57825,7 @@ static int btreeCursor(
   BtCursor *pCur                         /* Space for new cursor */
 ){
   BtShared *pBt = p->pBt;                /* Shared b-tree handle */
+  BtCursor *pX;                          /* Looping over other all cursors */
 
   assert( sqlite3BtreeHoldsMutex(p) );
   assert( wrFlag==0 || wrFlag==1 );
@@ -56899,10 +57841,8 @@ static int btreeCursor(
   assert( p->inTrans>TRANS_NONE );
   assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
   assert( pBt->pPage1 && pBt->pPage1->aData );
+  assert( wrFlag==0 || (pBt->btsFlags & BTS_READ_ONLY)==0 );
 
-  if( NEVER(wrFlag && (pBt->btsFlags & BTS_READ_ONLY)!=0) ){
-    return SQLITE_READONLY;
-  }
   if( wrFlag ){
     allocateTempSpace(pBt);
     if( pBt->pTmpSpace==0 ) return SQLITE_NOMEM;
@@ -56921,10 +57861,16 @@ static int btreeCursor(
   pCur->pBt = pBt;
   assert( wrFlag==0 || wrFlag==BTCF_WriteFlag );
   pCur->curFlags = wrFlag;
-  pCur->pNext = pBt->pCursor;
-  if( pCur->pNext ){
-    pCur->pNext->pPrev = pCur;
+  pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY;
+  /* If there are two or more cursors on the same btree, then all such
+  ** cursors *must* have the BTCF_Multiple flag set. */
+  for(pX=pBt->pCursor; pX; pX=pX->pNext){
+    if( pX->pgnoRoot==(Pgno)iTable ){
+      pX->curFlags |= BTCF_Multiple;
+      pCur->curFlags |= BTCF_Multiple;
+    }
   }
+  pCur->pNext = pBt->pCursor;
   pBt->pCursor = pCur;
   pCur->eState = CURSOR_INVALID;
   return SQLITE_OK;
@@ -56937,9 +57883,13 @@ SQLITE_PRIVATE int sqlite3BtreeCursor(
   BtCursor *pCur                              /* Write new cursor here */
 ){
   int rc;
-  sqlite3BtreeEnter(p);
-  rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
-  sqlite3BtreeLeave(p);
+  if( iTable<1 ){
+    rc = SQLITE_CORRUPT_BKPT;
+  }else{
+    sqlite3BtreeEnter(p);
+    rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
+    sqlite3BtreeLeave(p);
+  }
   return rc;
 }
 
@@ -56978,13 +57928,18 @@ SQLITE_PRIVATE int sqlite3BtreeCloseCursor(BtCursor *pCur){
     BtShared *pBt = pCur->pBt;
     sqlite3BtreeEnter(pBtree);
     sqlite3BtreeClearCursor(pCur);
-    if( pCur->pPrev ){
-      pCur->pPrev->pNext = pCur->pNext;
-    }else{
+    assert( pBt->pCursor!=0 );
+    if( pBt->pCursor==pCur ){
       pBt->pCursor = pCur->pNext;
-    }
-    if( pCur->pNext ){
-      pCur->pNext->pPrev = pCur->pPrev;
+    }else{
+      BtCursor *pPrev = pBt->pCursor;
+      do{
+        if( pPrev->pNext==pCur ){
+          pPrev->pNext = pCur->pNext;
+          break;
+        }
+        pPrev = pPrev->pNext;
+      }while( ALWAYS(pPrev) );
     }
     for(i=0; i<=pCur->iPage; i++){
       releasePage(pCur->apPage[i]);
@@ -57004,13 +57959,6 @@ SQLITE_PRIVATE int sqlite3BtreeCloseCursor(BtCursor *pCur){
 **
 ** BtCursor.info is a cache of the information in the current cell.
 ** Using this cache reduces the number of calls to btreeParseCell().
-**
-** 2007-06-25:  There is a bug in some versions of MSVC that cause the
-** compiler to crash when getCellInfo() is implemented as a macro.
-** But there is a measureable speed advantage to using the macro on gcc
-** (when less compiler optimizations like -Os or -O0 are used and the
-** compiler is not doing aggressive inlining.)  So we use a real function
-** for MSVC and a macro for everything else.  Ticket #2457.
 */
 #ifndef NDEBUG
   static void assertCellInfo(BtCursor *pCur){
@@ -57023,28 +57971,15 @@ SQLITE_PRIVATE int sqlite3BtreeCloseCursor(BtCursor *pCur){
 #else
   #define assertCellInfo(x)
 #endif
-#ifdef _MSC_VER
-  /* Use a real function in MSVC to work around bugs in that compiler. */
-  static void getCellInfo(BtCursor *pCur){
-    if( pCur->info.nSize==0 ){
-      int iPage = pCur->iPage;
-      btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
-      pCur->curFlags |= BTCF_ValidNKey;
-    }else{
-      assertCellInfo(pCur);
-    }
-  }
-#else /* if not _MSC_VER */
-  /* Use a macro in all other compilers so that the function is inlined */
-#define getCellInfo(pCur)                                                      \
-  if( pCur->info.nSize==0 ){                                                   \
-    int iPage = pCur->iPage;                                                   \
-    btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);        \
-    pCur->curFlags |= BTCF_ValidNKey;                                          \
-  }else{                                                                       \
-    assertCellInfo(pCur);                                                      \
+static SQLITE_NOINLINE void getCellInfo(BtCursor *pCur){
+  if( pCur->info.nSize==0 ){
+    int iPage = pCur->iPage;
+    pCur->curFlags |= BTCF_ValidNKey;
+    btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
+  }else{
+    assertCellInfo(pCur);
   }
-#endif /* _MSC_VER */
+}
 
 #ifndef NDEBUG  /* The next routine used only within assert() statements */
 /*
@@ -57550,9 +58485,6 @@ SQLITE_PRIVATE const void *sqlite3BtreeDataFetch(BtCursor *pCur, u32 *pAmt){
 ** vice-versa).
 */
 static int moveToChild(BtCursor *pCur, u32 newPgno){
-  int rc;
-  int i = pCur->iPage;
-  MemPage *pNewPage;
   BtShared *pBt = pCur->pBt;
 
   assert( cursorHoldsMutex(pCur) );
@@ -57562,19 +58494,12 @@ static int moveToChild(BtCursor *pCur, u32 newPgno){
   if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
     return SQLITE_CORRUPT_BKPT;
   }
-  rc = getAndInitPage(pBt, newPgno, &pNewPage,
-               (pCur->curFlags & BTCF_WriteFlag)==0 ? PAGER_GET_READONLY : 0);
-  if( rc ) return rc;
-  pCur->apPage[i+1] = pNewPage;
-  pCur->aiIdx[i+1] = 0;
-  pCur->iPage++;
-
   pCur->info.nSize = 0;
   pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
-  if( pNewPage->nCell<1 || pNewPage->intKey!=pCur->apPage[i]->intKey ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  return SQLITE_OK;
+  pCur->iPage++;
+  pCur->aiIdx[pCur->iPage] = 0;
+  return getAndInitPage(pBt, newPgno, &pCur->apPage[pCur->iPage],
+                        pCur, pCur->curPagerFlags);
 }
 
 #if SQLITE_DEBUG
@@ -57618,11 +58543,9 @@ static void moveToParent(BtCursor *pCur){
     pCur->apPage[pCur->iPage]->pgno
   );
   testcase( pCur->aiIdx[pCur->iPage-1] > pCur->apPage[pCur->iPage-1]->nCell );
-
-  releasePage(pCur->apPage[pCur->iPage]);
-  pCur->iPage--;
   pCur->info.nSize = 0;
   pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
+  releasePageNotNull(pCur->apPage[pCur->iPage--]);
 }
 
 /*
@@ -57663,18 +58586,23 @@ static int moveToRoot(BtCursor *pCur){
   }
 
   if( pCur->iPage>=0 ){
-    while( pCur->iPage ) releasePage(pCur->apPage[pCur->iPage--]);
+    while( pCur->iPage ){
+      assert( pCur->apPage[pCur->iPage]!=0 );
+      releasePageNotNull(pCur->apPage[pCur->iPage--]);
+    }
   }else if( pCur->pgnoRoot==0 ){
     pCur->eState = CURSOR_INVALID;
     return SQLITE_OK;
   }else{
+    assert( pCur->iPage==(-1) );
     rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->apPage[0],
-                 (pCur->curFlags & BTCF_WriteFlag)==0 ? PAGER_GET_READONLY : 0);
+                        0, pCur->curPagerFlags);
     if( rc!=SQLITE_OK ){
       pCur->eState = CURSOR_INVALID;
       return rc;
     }
     pCur->iPage = 0;
+    pCur->curIntKey = pCur->apPage[0]->intKey;
   }
   pRoot = pCur->apPage[0];
   assert( pRoot->pgno==pCur->pgnoRoot );
@@ -57877,7 +58805,7 @@ SQLITE_PRIVATE int sqlite3BtreeMovetoUnpacked(
   /* If the cursor is already positioned at the point we are trying
   ** to move to, then just return without doing any work */
   if( pCur->eState==CURSOR_VALID && (pCur->curFlags & BTCF_ValidNKey)!=0
-   && pCur->apPage[0]->intKey 
+   && pCur->curIntKey 
   ){
     if( pCur->info.nKey==intKey ){
       *pRes = 0;
@@ -57912,7 +58840,8 @@ SQLITE_PRIVATE int sqlite3BtreeMovetoUnpacked(
     assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
     return SQLITE_OK;
   }
-  assert( pCur->apPage[0]->intKey || pIdxKey );
+  assert( pCur->apPage[0]->intKey==pCur->curIntKey );
+  assert( pCur->curIntKey || pIdxKey );
   for(;;){
     int lwr, upr, idx, c;
     Pgno chldPg;
@@ -57935,7 +58864,7 @@ SQLITE_PRIVATE int sqlite3BtreeMovetoUnpacked(
     if( xRecordCompare==0 ){
       for(;;){
         i64 nCellKey;
-        pCell = findCell(pPage, idx) + pPage->childPtrSize;
+        pCell = findCellPastPtr(pPage, idx);
         if( pPage->intKeyLeaf ){
           while( 0x80 <= *(pCell++) ){
             if( pCell>=pPage->aDataEnd ) return SQLITE_CORRUPT_BKPT;
@@ -57967,8 +58896,8 @@ SQLITE_PRIVATE int sqlite3BtreeMovetoUnpacked(
       }
     }else{
       for(;;){
-        int nCell;
-        pCell = findCell(pPage, idx) + pPage->childPtrSize;
+        int nCell;  /* Size of the pCell cell in bytes */
+        pCell = findCellPastPtr(pPage, idx);
 
         /* The maximum supported page-size is 65536 bytes. This means that
         ** the maximum number of record bytes stored on an index B-Tree
@@ -57996,12 +58925,25 @@ SQLITE_PRIVATE int sqlite3BtreeMovetoUnpacked(
           /* The record flows over onto one or more overflow pages. In
           ** this case the whole cell needs to be parsed, a buffer allocated
           ** and accessPayload() used to retrieve the record into the
-          ** buffer before VdbeRecordCompare() can be called. */
+          ** buffer before VdbeRecordCompare() can be called. 
+          **
+          ** If the record is corrupt, the xRecordCompare routine may read
+          ** up to two varints past the end of the buffer. An extra 18 
+          ** bytes of padding is allocated at the end of the buffer in
+          ** case this happens.  */
           void *pCellKey;
           u8 * const pCellBody = pCell - pPage->childPtrSize;
-          btreeParseCellPtr(pPage, pCellBody, &pCur->info);
+          pPage->xParseCell(pPage, pCellBody, &pCur->info);
           nCell = (int)pCur->info.nKey;
-          pCellKey = sqlite3Malloc( nCell );
+          testcase( nCell<0 );   /* True if key size is 2^32 or more */
+          testcase( nCell==0 );  /* Invalid key size:  0x80 0x80 0x00 */
+          testcase( nCell==1 );  /* Invalid key size:  0x80 0x80 0x01 */
+          testcase( nCell==2 );  /* Minimum legal index key size */
+          if( nCell<2 ){
+            rc = SQLITE_CORRUPT_BKPT;
+            goto moveto_finish;
+          }
+          pCellKey = sqlite3Malloc( nCell+18 );
           if( pCellKey==0 ){
             rc = SQLITE_NOMEM;
             goto moveto_finish;
@@ -58294,8 +59236,7 @@ SQLITE_PRIVATE int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
 ** sqlite3PagerUnref() on the new page when it is done.
 **
 ** SQLITE_OK is returned on success.  Any other return value indicates
-** an error.  *ppPage and *pPgno are undefined in the event of an error.
-** Do not invoke sqlite3PagerUnref() on *ppPage if an error is returned.
+** an error.  *ppPage is set to NULL in the event of an error.
 **
 ** If the "nearby" parameter is not 0, then an effort is made to 
 ** locate a page close to the page number "nearby".  This can be used in an
@@ -58338,6 +59279,7 @@ static int allocateBtreePage(
     /* There are pages on the freelist.  Reuse one of those pages. */
     Pgno iTrunk;
     u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
+    u32 nSearch = 0;   /* Count of the number of search attempts */
     
     /* If eMode==BTALLOC_EXACT and a query of the pointer-map
     ** shows that the page 'nearby' is somewhere on the free-list, then
@@ -58386,10 +59328,10 @@ static int allocateBtreePage(
         iTrunk = get4byte(&pPage1->aData[32]);
       }
       testcase( iTrunk==mxPage );
-      if( iTrunk>mxPage ){
+      if( iTrunk>mxPage || nSearch++ > n ){
         rc = SQLITE_CORRUPT_BKPT;
       }else{
-        rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
+        rc = btreeGetUnusedPage(pBt, iTrunk, &pTrunk, 0);
       }
       if( rc ){
         pTrunk = 0;
@@ -58454,7 +59396,7 @@ static int allocateBtreePage(
             goto end_allocate_page;
           }
           testcase( iNewTrunk==mxPage );
-          rc = btreeGetPage(pBt, iNewTrunk, &pNewTrunk, 0);
+          rc = btreeGetUnusedPage(pBt, iNewTrunk, &pNewTrunk, 0);
           if( rc!=SQLITE_OK ){
             goto end_allocate_page;
           }
@@ -58534,11 +59476,12 @@ static int allocateBtreePage(
           }
           put4byte(&aData[4], k-1);
           noContent = !btreeGetHasContent(pBt, *pPgno)? PAGER_GET_NOCONTENT : 0;
-          rc = btreeGetPage(pBt, *pPgno, ppPage, noContent);
+          rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, noContent);
           if( rc==SQLITE_OK ){
             rc = sqlite3PagerWrite((*ppPage)->pDbPage);
             if( rc!=SQLITE_OK ){
               releasePage(*ppPage);
+              *ppPage = 0;
             }
           }
           searchList = 0;
@@ -58582,7 +59525,7 @@ static int allocateBtreePage(
       MemPage *pPg = 0;
       TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
       assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
-      rc = btreeGetPage(pBt, pBt->nPage, &pPg, bNoContent);
+      rc = btreeGetUnusedPage(pBt, pBt->nPage, &pPg, bNoContent);
       if( rc==SQLITE_OK ){
         rc = sqlite3PagerWrite(pPg->pDbPage);
         releasePage(pPg);
@@ -58596,11 +59539,12 @@ static int allocateBtreePage(
     *pPgno = pBt->nPage;
 
     assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-    rc = btreeGetPage(pBt, *pPgno, ppPage, bNoContent);
+    rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, bNoContent);
     if( rc ) return rc;
     rc = sqlite3PagerWrite((*ppPage)->pDbPage);
     if( rc!=SQLITE_OK ){
       releasePage(*ppPage);
+      *ppPage = 0;
     }
     TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
   }
@@ -58610,17 +59554,8 @@ static int allocateBtreePage(
 end_allocate_page:
   releasePage(pTrunk);
   releasePage(pPrevTrunk);
-  if( rc==SQLITE_OK ){
-    if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
-      releasePage(*ppPage);
-      *ppPage = 0;
-      return SQLITE_CORRUPT_BKPT;
-    }
-    (*ppPage)->isInit = 0;
-  }else{
-    *ppPage = 0;
-  }
-  assert( rc!=SQLITE_OK || sqlite3PagerIswriteable((*ppPage)->pDbPage) );
+  assert( rc!=SQLITE_OK || sqlite3PagerPageRefcount((*ppPage)->pDbPage)<=1 );
+  assert( rc!=SQLITE_OK || (*ppPage)->isInit==0 );
   return rc;
 }
 
@@ -58645,9 +59580,10 @@ static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
   int nFree;                          /* Initial number of pages on free-list */
 
   assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( iPage>1 );
+  assert( CORRUPT_DB || iPage>1 );
   assert( !pMemPage || pMemPage->pgno==iPage );
 
+  if( iPage<2 ) return SQLITE_CORRUPT_BKPT;
   if( pMemPage ){
     pPage = pMemPage;
     sqlite3PagerRef(pPage->pDbPage);
@@ -58787,7 +59723,7 @@ static int clearCell(
   u32 ovflPageSize;
 
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  btreeParseCellPtr(pPage, pCell, &info);
+  pPage->xParseCell(pPage, pCell, &info);
   *pnSize = info.nSize;
   if( info.iOverflow==0 ){
     return SQLITE_OK;  /* No overflow pages. Return without doing anything */
@@ -58799,7 +59735,9 @@ static int clearCell(
   assert( pBt->usableSize > 4 );
   ovflPageSize = pBt->usableSize - 4;
   nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
-  assert( ovflPgno==0 || nOvfl>0 );
+  assert( nOvfl>0 || 
+    (CORRUPT_DB && (info.nPayload + ovflPageSize)<ovflPageSize)
+  );
   while( nOvfl-- ){
     Pgno iNext = 0;
     MemPage *pOvfl = 0;
@@ -58897,9 +59835,7 @@ static int fillInCell(
     nSrc = nData;
     nData = 0;
   }else{ 
-    if( NEVER(nKey>0x7fffffff || pKey==0) ){
-      return SQLITE_CORRUPT_BKPT;
-    }
+    assert( nKey<=0x7fffffff && pKey!=0 );
     nPayload = (int)nKey;
     pSrc = pKey;
     nSrc = (int)nKey;
@@ -58939,7 +59875,7 @@ static int fillInCell(
 #if SQLITE_DEBUG
   {
     CellInfo info;
-    btreeParseCellPtr(pPage, pCell, &info);
+    pPage->xParseCell(pPage, pCell, &info);
     assert( nHeader=(int)(info.pPayload - pCell) );
     assert( info.nKey==nKey );
     assert( *pnSize == info.nSize );
@@ -59054,7 +59990,7 @@ static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
   if( *pRC ) return;
 
   assert( idx>=0 && idx<pPage->nCell );
-  assert( sz==cellSize(pPage, idx) );
+  assert( CORRUPT_DB || sz==cellSize(pPage, idx) );
   assert( sqlite3PagerIswriteable(pPage->pDbPage) );
   assert( sqlite3_mutex_held(pPage->pBt->mutex) );
   data = pPage->aData;
@@ -59109,10 +60045,8 @@ static void insertCell(
 ){
   int idx = 0;      /* Where to write new cell content in data[] */
   int j;            /* Loop counter */
-  int end;          /* First byte past the last cell pointer in data[] */
-  int ins;          /* Index in data[] where new cell pointer is inserted */
-  int cellOffset;   /* Address of first cell pointer in data[] */
   u8 *data;         /* The content of the whole page */
+  u8 *pIns;         /* The point in pPage->aCellIdx[] where no cell inserted */
 
   if( *pRC ) return;
 
@@ -59127,7 +60061,7 @@ static void insertCell(
   ** wanted to be less than 4 but got rounded up to 4 on the leaf, then size
   ** might be less than 8 (leaf-size + pointer) on the interior node.  Hence
   ** the term after the || in the following assert(). */
-  assert( sz==cellSizePtr(pPage, pCell) || (sz==8 && iChild>0) );
+  assert( sz==pPage->xCellSize(pPage, pCell) || (sz==8 && iChild>0) );
   if( pPage->nOverflow || sz+2>pPage->nFree ){
     if( pTemp ){
       memcpy(pTemp, pCell, sz);
@@ -59140,6 +60074,14 @@ static void insertCell(
     assert( j<(int)(sizeof(pPage->apOvfl)/sizeof(pPage->apOvfl[0])) );
     pPage->apOvfl[j] = pCell;
     pPage->aiOvfl[j] = (u16)i;
+
+    /* When multiple overflows occur, they are always sequential and in
+    ** sorted order.  This invariants arise because multiple overflows can
+    ** only occur when inserting divider cells into the parent page during
+    ** balancing, and the dividers are adjacent and sorted.
+    */
+    assert( j==0 || pPage->aiOvfl[j-1]<(u16)i ); /* Overflows in sorted order */
+    assert( j==0 || i==pPage->aiOvfl[j-1]+1 );   /* Overflows are sequential */
   }else{
     int rc = sqlite3PagerWrite(pPage->pDbPage);
     if( rc!=SQLITE_OK ){
@@ -59148,24 +60090,26 @@ static void insertCell(
     }
     assert( sqlite3PagerIswriteable(pPage->pDbPage) );
     data = pPage->aData;
-    cellOffset = pPage->cellOffset;
-    end = cellOffset + 2*pPage->nCell;
-    ins = cellOffset + 2*i;
+    assert( &data[pPage->cellOffset]==pPage->aCellIdx );
     rc = allocateSpace(pPage, sz, &idx);
     if( rc ){ *pRC = rc; return; }
-    /* The allocateSpace() routine guarantees the following two properties
-    ** if it returns success */
-    assert( idx >= end+2 );
+    /* The allocateSpace() routine guarantees the following properties
+    ** if it returns successfully */
+    assert( idx >= 0 );
+    assert( idx >= pPage->cellOffset+2*pPage->nCell+2 || CORRUPT_DB );
     assert( idx+sz <= (int)pPage->pBt->usableSize );
-    pPage->nCell++;
     pPage->nFree -= (u16)(2 + sz);
     memcpy(&data[idx], pCell, sz);
     if( iChild ){
       put4byte(&data[idx], iChild);
     }
-    memmove(&data[ins+2], &data[ins], end-ins);
-    put2byte(&data[ins], idx);
-    put2byte(&data[pPage->hdrOffset+3], pPage->nCell);
+    pIns = pPage->aCellIdx + i*2;
+    memmove(pIns+2, pIns, 2*(pPage->nCell - i));
+    put2byte(pIns, idx);
+    pPage->nCell++;
+    /* increment the cell count */
+    if( (++data[pPage->hdrOffset+4])==0 ) data[pPage->hdrOffset+3]++;
+    assert( get2byte(&data[pPage->hdrOffset+3])==pPage->nCell );
 #ifndef SQLITE_OMIT_AUTOVACUUM
     if( pPage->pBt->autoVacuum ){
       /* The cell may contain a pointer to an overflow page. If so, write
@@ -59177,6 +60121,52 @@ static void insertCell(
   }
 }
 
+/*
+** A CellArray object contains a cache of pointers and sizes for a
+** consecutive sequence of cells that might be held multiple pages.
+*/
+typedef struct CellArray CellArray;
+struct CellArray {
+  int nCell;              /* Number of cells in apCell[] */
+  MemPage *pRef;          /* Reference page */
+  u8 **apCell;            /* All cells begin balanced */
+  u16 *szCell;            /* Local size of all cells in apCell[] */
+};
+
+/*
+** Make sure the cell sizes at idx, idx+1, ..., idx+N-1 have been
+** computed.
+*/
+static void populateCellCache(CellArray *p, int idx, int N){
+  assert( idx>=0 && idx+N<=p->nCell );
+  while( N>0 ){
+    assert( p->apCell[idx]!=0 );
+    if( p->szCell[idx]==0 ){
+      p->szCell[idx] = p->pRef->xCellSize(p->pRef, p->apCell[idx]);
+    }else{
+      assert( CORRUPT_DB ||
+              p->szCell[idx]==p->pRef->xCellSize(p->pRef, p->apCell[idx]) );
+    }
+    idx++;
+    N--;
+  }
+}
+
+/*
+** Return the size of the Nth element of the cell array
+*/
+static SQLITE_NOINLINE u16 computeCellSize(CellArray *p, int N){
+  assert( N>=0 && N<p->nCell );
+  assert( p->szCell[N]==0 );
+  p->szCell[N] = p->pRef->xCellSize(p->pRef, p->apCell[N]);
+  return p->szCell[N];
+}
+static u16 cachedCellSize(CellArray *p, int N){
+  assert( N>=0 && N<p->nCell );
+  if( p->szCell[N] ) return p->szCell[N];
+  return computeCellSize(p, N);
+}
+
 /*
 ** Array apCell[] contains pointers to nCell b-tree page cells. The 
 ** szCell[] array contains the size in bytes of each cell. This function
@@ -59190,7 +60180,7 @@ static void insertCell(
 ** The MemPage.nFree field is invalidated by this function. It is the 
 ** responsibility of the caller to set it correctly.
 */
-static void rebuildPage(
+static int rebuildPage(
   MemPage *pPg,                   /* Edit this page */
   int nCell,                      /* Final number of cells on page */
   u8 **apCell,                    /* Array of cells */
@@ -59215,10 +60205,12 @@ static void rebuildPage(
       pCell = &pTmp[pCell - aData];
     }
     pData -= szCell[i];
-    memcpy(pData, pCell, szCell[i]);
     put2byte(pCellptr, (pData - aData));
     pCellptr += 2;
-    assert( szCell[i]==cellSizePtr(pPg, pCell) );
+    if( pData < pCellptr ) return SQLITE_CORRUPT_BKPT;
+    memcpy(pData, pCell, szCell[i]);
+    assert( szCell[i]==pPg->xCellSize(pPg, pCell) || CORRUPT_DB );
+    testcase( szCell[i]!=pPg->xCellSize(pPg,pCell) );
   }
 
   /* The pPg->nFree field is now set incorrectly. The caller will fix it. */
@@ -59229,6 +60221,7 @@ static void rebuildPage(
   put2byte(&aData[hdr+3], pPg->nCell);
   put2byte(&aData[hdr+5], pData - aData);
   aData[hdr+7] = 0x00;
+  return SQLITE_OK;
 }
 
 /*
@@ -59261,25 +60254,25 @@ static int pageInsertArray(
   u8 *pBegin,                     /* End of cell-pointer array */
   u8 **ppData,                    /* IN/OUT: Page content -area pointer */
   u8 *pCellptr,                   /* Pointer to cell-pointer area */
+  int iFirst,                     /* Index of first cell to add */
   int nCell,                      /* Number of cells to add to pPg */
-  u8 **apCell,                    /* Array of cells */
-  u16 *szCell                     /* Array of cell sizes */
+  CellArray *pCArray              /* Array of cells */
 ){
   int i;
   u8 *aData = pPg->aData;
   u8 *pData = *ppData;
-  const int bFreelist = aData[1] || aData[2];
+  int iEnd = iFirst + nCell;
   assert( CORRUPT_DB || pPg->hdrOffset==0 );    /* Never called on page 1 */
-  for(i=0; i<nCell; i++){
-    int sz = szCell[i];
-    int rc;
+  for(i=iFirst; i<iEnd; i++){
+    int sz, rc;
     u8 *pSlot;
-    if( bFreelist==0 || (pSlot = pageFindSlot(pPg, sz, &rc, 0))==0 ){
+    sz = cachedCellSize(pCArray, i);
+    if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
       pData -= sz;
       if( pData<pBegin ) return 1;
       pSlot = pData;
     }
-    memcpy(pSlot, apCell[i], sz);
+    memcpy(pSlot, pCArray->apCell[i], sz);
     put2byte(pCellptr, (pSlot - aData));
     pCellptr += 2;
   }
@@ -59298,22 +60291,27 @@ static int pageInsertArray(
 */
 static int pageFreeArray(
   MemPage *pPg,                   /* Page to edit */
+  int iFirst,                     /* First cell to delete */
   int nCell,                      /* Cells to delete */
-  u8 **apCell,                    /* Array of cells */
-  u16 *szCell                     /* Array of cell sizes */
+  CellArray *pCArray              /* Array of cells */
 ){
   u8 * const aData = pPg->aData;
   u8 * const pEnd = &aData[pPg->pBt->usableSize];
   u8 * const pStart = &aData[pPg->hdrOffset + 8 + pPg->childPtrSize];
   int nRet = 0;
   int i;
+  int iEnd = iFirst + nCell;
   u8 *pFree = 0;
   int szFree = 0;
 
-  for(i=0; i<nCell; i++){
-    u8 *pCell = apCell[i];
+  for(i=iFirst; i<iEnd; i++){
+    u8 *pCell = pCArray->apCell[i];
     if( pCell>=pStart && pCell<pEnd ){
-      int sz = szCell[i];
+      int sz;
+      /* No need to use cachedCellSize() here.  The sizes of all cells that
+      ** are to be freed have already been computing while deciding which
+      ** cells need freeing */
+      sz = pCArray->szCell[i];  assert( sz>0 );
       if( pFree!=(pCell + sz) ){
         if( pFree ){
           assert( pFree>aData && (pFree - aData)<65536 );
@@ -59348,13 +60346,12 @@ static int pageFreeArray(
 ** The pPg->nFree field is invalid when this function returns. It is the
 ** responsibility of the caller to set it correctly.
 */
-static void editPage(
+static int editPage(
   MemPage *pPg,                   /* Edit this page */
   int iOld,                       /* Index of first cell currently on page */
   int iNew,                       /* Index of new first cell on page */
   int nNew,                       /* Final number of cells on page */
-  u8 **apCell,                    /* Array of cells */
-  u16 *szCell                     /* Array of cell sizes */
+  CellArray *pCArray              /* Array of cells and sizes */
 ){
   u8 * const aData = pPg->aData;
   const int hdr = pPg->hdrOffset;
@@ -59373,16 +60370,12 @@ static void editPage(
 
   /* Remove cells from the start and end of the page */
   if( iOld<iNew ){
-    int nShift = pageFreeArray(
-        pPg, iNew-iOld, &apCell[iOld], &szCell[iOld]
-    );
+    int nShift = pageFreeArray(pPg, iOld, iNew-iOld, pCArray);
     memmove(pPg->aCellIdx, &pPg->aCellIdx[nShift*2], nCell*2);
     nCell -= nShift;
   }
   if( iNewEnd < iOldEnd ){
-    nCell -= pageFreeArray(
-        pPg, iOldEnd-iNewEnd, &apCell[iNewEnd], &szCell[iNewEnd]
-    );
+    nCell -= pageFreeArray(pPg, iNewEnd, iOldEnd - iNewEnd, pCArray);
   }
 
   pData = &aData[get2byteNotZero(&aData[hdr+5])];
@@ -59396,7 +60389,7 @@ static void editPage(
     memmove(&pCellptr[nAdd*2], pCellptr, nCell*2);
     if( pageInsertArray(
           pPg, pBegin, &pData, pCellptr,
-          nAdd, &apCell[iNew], &szCell[iNew]
+          iNew, nAdd, pCArray
     ) ) goto editpage_fail;
     nCell += nAdd;
   }
@@ -59410,7 +60403,7 @@ static void editPage(
       nCell++;
       if( pageInsertArray(
             pPg, pBegin, &pData, pCellptr,
-            1, &apCell[iCell + iNew], &szCell[iCell + iNew]
+            iCell+iNew, 1, pCArray
       ) ) goto editpage_fail;
     }
   }
@@ -59419,7 +60412,7 @@ static void editPage(
   pCellptr = &pPg->aCellIdx[nCell*2];
   if( pageInsertArray(
         pPg, pBegin, &pData, pCellptr,
-        nNew-nCell, &apCell[iNew+nCell], &szCell[iNew+nCell]
+        iNew+nCell, nNew-nCell, pCArray
   ) ) goto editpage_fail;
 
   pPg->nCell = nNew;
@@ -59430,19 +60423,21 @@ static void editPage(
 
 #ifdef SQLITE_DEBUG
   for(i=0; i<nNew && !CORRUPT_DB; i++){
-    u8 *pCell = apCell[i+iNew];
-    int iOff = get2byte(&pPg->aCellIdx[i*2]);
+    u8 *pCell = pCArray->apCell[i+iNew];
+    int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
     if( pCell>=aData && pCell<&aData[pPg->pBt->usableSize] ){
       pCell = &pTmp[pCell - aData];
     }
-    assert( 0==memcmp(pCell, &aData[iOff], szCell[i+iNew]) );
+    assert( 0==memcmp(pCell, &aData[iOff],
+            pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
   }
 #endif
 
-  return;
+  return SQLITE_OK;
  editpage_fail:
   /* Unable to edit this page. Rebuild it from scratch instead. */
-  rebuildPage(pPg, nNew, &apCell[iNew], &szCell[iNew]);
+  populateCellCache(pCArray, iNew, nNew);
+  return rebuildPage(pPg, nNew, &pCArray->apCell[iNew], &pCArray->szCell[iNew]);
 }
 
 /*
@@ -59508,13 +60503,14 @@ static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
 
     u8 *pOut = &pSpace[4];
     u8 *pCell = pPage->apOvfl[0];
-    u16 szCell = cellSizePtr(pPage, pCell);
+    u16 szCell = pPage->xCellSize(pPage, pCell);
     u8 *pStop;
 
     assert( sqlite3PagerIswriteable(pNew->pDbPage) );
     assert( pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
     zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
-    rebuildPage(pNew, 1, &pCell, &szCell);
+    rc = rebuildPage(pNew, 1, &pCell, &szCell);
+    if( NEVER(rc) ) return rc;
     pNew->nFree = pBt->usableSize - pNew->cellOffset - 2 - szCell;
 
     /* If this is an auto-vacuum database, update the pointer map
@@ -59587,7 +60583,7 @@ static int ptrmapCheckPages(MemPage **apPage, int nPage){
       u8 *z;
      
       z = findCell(pPage, j);
-      btreeParseCellPtr(pPage, z, &info);
+      pPage->xParseCell(pPage, z, &info);
       if( info.iOverflow ){
         Pgno ovfl = get4byte(&z[info.iOverflow]);
         ptrmapGet(pBt, ovfl, &e, &n);
@@ -59718,7 +60714,6 @@ static int balance_nonroot(
   int bBulk                       /* True if this call is part of a bulk load */
 ){
   BtShared *pBt;               /* The whole database */
-  int nCell = 0;               /* Number of cells in apCell[] */
   int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
   int nNew = 0;                /* Number of pages in apNew[] */
   int nOld;                    /* Number of pages in apOld[] */
@@ -59729,7 +60724,6 @@ static int balance_nonroot(
   int leafData;                /* True if pPage is a leaf of a LEAFDATA tree */
   int usableSpace;             /* Bytes in pPage beyond the header */
   int pageFlags;               /* Value of pPage->aData[0] */
-  int subtotal;                /* Subtotal of bytes in cells on one page */
   int iSpace1 = 0;             /* First unused byte of aSpace1[] */
   int iOvflSpace = 0;          /* First unused byte of aOvflSpace[] */
   int szScratch;               /* Size of scratch memory requested */
@@ -59737,19 +60731,20 @@ static int balance_nonroot(
   MemPage *apNew[NB+2];        /* pPage and up to NB siblings after balancing */
   u8 *pRight;                  /* Location in parent of right-sibling pointer */
   u8 *apDiv[NB-1];             /* Divider cells in pParent */
-  int cntNew[NB+2];            /* Index in aCell[] of cell after i-th page */
-  int cntOld[NB+2];            /* Old index in aCell[] after i-th page */
+  int cntNew[NB+2];            /* Index in b.paCell[] of cell after i-th page */
+  int cntOld[NB+2];            /* Old index in b.apCell[] */
   int szNew[NB+2];             /* Combined size of cells placed on i-th page */
-  u8 **apCell = 0;             /* All cells begin balanced */
-  u16 *szCell;                 /* Local size of all cells in apCell[] */
   u8 *aSpace1;                 /* Space for copies of dividers cells */
   Pgno pgno;                   /* Temp var to store a page number in */
   u8 abDone[NB+2];             /* True after i'th new page is populated */
   Pgno aPgno[NB+2];            /* Page numbers of new pages before shuffling */
   Pgno aPgOrder[NB+2];         /* Copy of aPgno[] used for sorting pages */
   u16 aPgFlags[NB+2];          /* flags field of new pages before shuffling */
+  CellArray b;                  /* Parsed information on cells being balanced */
 
   memset(abDone, 0, sizeof(abDone));
+  b.nCell = 0;
+  b.apCell = 0;
   pBt = pParent->pBt;
   assert( sqlite3_mutex_held(pBt->mutex) );
   assert( sqlite3PagerIswriteable(pParent->pDbPage) );
@@ -59803,7 +60798,7 @@ static int balance_nonroot(
   }
   pgno = get4byte(pRight);
   while( 1 ){
-    rc = getAndInitPage(pBt, pgno, &apOld[i], 0);
+    rc = getAndInitPage(pBt, pgno, &apOld[i], 0, 0);
     if( rc ){
       memset(apOld, 0, (i+1)*sizeof(MemPage*));
       goto balance_cleanup;
@@ -59814,12 +60809,12 @@ static int balance_nonroot(
     if( i+nxDiv==pParent->aiOvfl[0] && pParent->nOverflow ){
       apDiv[i] = pParent->apOvfl[0];
       pgno = get4byte(apDiv[i]);
-      szNew[i] = cellSizePtr(pParent, apDiv[i]);
+      szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
       pParent->nOverflow = 0;
     }else{
       apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
       pgno = get4byte(apDiv[i]);
-      szNew[i] = cellSizePtr(pParent, apDiv[i]);
+      szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
 
       /* Drop the cell from the parent page. apDiv[i] still points to
       ** the cell within the parent, even though it has been dropped.
@@ -59858,130 +60853,201 @@ static int balance_nonroot(
   ** Allocate space for memory structures
   */
   szScratch =
-       nMaxCells*sizeof(u8*)                       /* apCell */
-     + nMaxCells*sizeof(u16)                       /* szCell */
+       nMaxCells*sizeof(u8*)                       /* b.apCell */
+     + nMaxCells*sizeof(u16)                       /* b.szCell */
      + pBt->pageSize;                              /* aSpace1 */
 
   /* EVIDENCE-OF: R-28375-38319 SQLite will never request a scratch buffer
   ** that is more than 6 times the database page size. */
   assert( szScratch<=6*(int)pBt->pageSize );
-  apCell = sqlite3ScratchMalloc( szScratch ); 
-  if( apCell==0 ){
+  b.apCell = sqlite3ScratchMalloc( szScratch ); 
+  if( b.apCell==0 ){
     rc = SQLITE_NOMEM;
     goto balance_cleanup;
   }
-  szCell = (u16*)&apCell[nMaxCells];
-  aSpace1 = (u8*)&szCell[nMaxCells];
+  b.szCell = (u16*)&b.apCell[nMaxCells];
+  aSpace1 = (u8*)&b.szCell[nMaxCells];
   assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );
 
   /*
   ** Load pointers to all cells on sibling pages and the divider cells
-  ** into the local apCell[] array.  Make copies of the divider cells
+  ** into the local b.apCell[] array.  Make copies of the divider cells
   ** into space obtained from aSpace1[]. The divider cells have already
   ** been removed from pParent.
   **
   ** If the siblings are on leaf pages, then the child pointers of the
   ** divider cells are stripped from the cells before they are copied
-  ** into aSpace1[].  In this way, all cells in apCell[] are without
+  ** into aSpace1[].  In this way, all cells in b.apCell[] are without
   ** child pointers.  If siblings are not leaves, then all cell in
-  ** apCell[] include child pointers.  Either way, all cells in apCell[]
+  ** b.apCell[] include child pointers.  Either way, all cells in b.apCell[]
   ** are alike.
   **
   ** leafCorrection:  4 if pPage is a leaf.  0 if pPage is not a leaf.
   **       leafData:  1 if pPage holds key+data and pParent holds only keys.
   */
-  leafCorrection = apOld[0]->leaf*4;
-  leafData = apOld[0]->intKeyLeaf;
+  b.pRef = apOld[0];
+  leafCorrection = b.pRef->leaf*4;
+  leafData = b.pRef->intKeyLeaf;
   for(i=0; i<nOld; i++){
-    int limit;
     MemPage *pOld = apOld[i];
+    int limit = pOld->nCell;
+    u8 *aData = pOld->aData;
+    u16 maskPage = pOld->maskPage;
+    u8 *piCell = aData + pOld->cellOffset;
+    u8 *piEnd;
+
+    /* Verify that all sibling pages are of the same "type" (table-leaf,
+    ** table-interior, index-leaf, or index-interior).
+    */
+    if( pOld->aData[0]!=apOld[0]->aData[0] ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
 
-    limit = pOld->nCell+pOld->nOverflow;
+    /* Load b.apCell[] with pointers to all cells in pOld.  If pOld
+    ** constains overflow cells, include them in the b.apCell[] array
+    ** in the correct spot.
+    **
+    ** Note that when there are multiple overflow cells, it is always the
+    ** case that they are sequential and adjacent.  This invariant arises
+    ** because multiple overflows can only occurs when inserting divider
+    ** cells into a parent on a prior balance, and divider cells are always
+    ** adjacent and are inserted in order.  There is an assert() tagged
+    ** with "NOTE 1" in the overflow cell insertion loop to prove this
+    ** invariant.
+    **
+    ** This must be done in advance.  Once the balance starts, the cell
+    ** offset section of the btree page will be overwritten and we will no
+    ** long be able to find the cells if a pointer to each cell is not saved
+    ** first.
+    */
+    memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*limit);
     if( pOld->nOverflow>0 ){
+      memset(&b.szCell[b.nCell+limit], 0, sizeof(b.szCell[0])*pOld->nOverflow);
+      limit = pOld->aiOvfl[0];
       for(j=0; j<limit; j++){
-        assert( nCell<nMaxCells );
-        apCell[nCell] = findOverflowCell(pOld, j);
-        szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
-        nCell++;
+        b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
+        piCell += 2;
+        b.nCell++;
       }
-    }else{
-      u8 *aData = pOld->aData;
-      u16 maskPage = pOld->maskPage;
-      u16 cellOffset = pOld->cellOffset;
-      for(j=0; j<limit; j++){
-        assert( nCell<nMaxCells );
-        apCell[nCell] = findCellv2(aData, maskPage, cellOffset, j);
-        szCell[nCell] = cellSizePtr(pOld, apCell[nCell]);
-        nCell++;
+      for(k=0; k<pOld->nOverflow; k++){
+        assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
+        b.apCell[b.nCell] = pOld->apOvfl[k];
+        b.nCell++;
       }
-    }       
-    cntOld[i] = nCell;
+    }
+    piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
+    while( piCell<piEnd ){
+      assert( b.nCell<nMaxCells );
+      b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
+      piCell += 2;
+      b.nCell++;
+    }
+
+    cntOld[i] = b.nCell;
     if( i<nOld-1 && !leafData){
       u16 sz = (u16)szNew[i];
       u8 *pTemp;
-      assert( nCell<nMaxCells );
-      szCell[nCell] = sz;
+      assert( b.nCell<nMaxCells );
+      b.szCell[b.nCell] = sz;
       pTemp = &aSpace1[iSpace1];
       iSpace1 += sz;
       assert( sz<=pBt->maxLocal+23 );
       assert( iSpace1 <= (int)pBt->pageSize );
       memcpy(pTemp, apDiv[i], sz);
-      apCell[nCell] = pTemp+leafCorrection;
+      b.apCell[b.nCell] = pTemp+leafCorrection;
       assert( leafCorrection==0 || leafCorrection==4 );
-      szCell[nCell] = szCell[nCell] - leafCorrection;
+      b.szCell[b.nCell] = b.szCell[b.nCell] - leafCorrection;
       if( !pOld->leaf ){
         assert( leafCorrection==0 );
         assert( pOld->hdrOffset==0 );
         /* The right pointer of the child page pOld becomes the left
         ** pointer of the divider cell */
-        memcpy(apCell[nCell], &pOld->aData[8], 4);
+        memcpy(b.apCell[b.nCell], &pOld->aData[8], 4);
       }else{
         assert( leafCorrection==4 );
-        if( szCell[nCell]<4 ){
+        while( b.szCell[b.nCell]<4 ){
           /* Do not allow any cells smaller than 4 bytes. If a smaller cell
           ** does exist, pad it with 0x00 bytes. */
-          assert( szCell[nCell]==3 );
-          assert( apCell[nCell]==&aSpace1[iSpace1-3] );
+          assert( b.szCell[b.nCell]==3 || CORRUPT_DB );
+          assert( b.apCell[b.nCell]==&aSpace1[iSpace1-3] || CORRUPT_DB );
           aSpace1[iSpace1++] = 0x00;
-          szCell[nCell] = 4;
+          b.szCell[b.nCell]++;
         }
       }
-      nCell++;
+      b.nCell++;
     }
   }
 
   /*
-  ** Figure out the number of pages needed to hold all nCell cells.
+  ** Figure out the number of pages needed to hold all b.nCell cells.
   ** Store this number in "k".  Also compute szNew[] which is the total
   ** size of all cells on the i-th page and cntNew[] which is the index
-  ** in apCell[] of the cell that divides page i from page i+1.  
-  ** cntNew[k] should equal nCell.
+  ** in b.apCell[] of the cell that divides page i from page i+1.  
+  ** cntNew[k] should equal b.nCell.
   **
   ** Values computed by this block:
   **
   **           k: The total number of sibling pages
   **    szNew[i]: Spaced used on the i-th sibling page.
-  **   cntNew[i]: Index in apCell[] and szCell[] for the first cell to
+  **   cntNew[i]: Index in b.apCell[] and b.szCell[] for the first cell to
   **              the right of the i-th sibling page.
   ** usableSpace: Number of bytes of space available on each sibling.
   ** 
   */
   usableSpace = pBt->usableSize - 12 + leafCorrection;
-  for(subtotal=k=i=0; i<nCell; i++){
-    assert( i<nMaxCells );
-    subtotal += szCell[i] + 2;
-    if( subtotal > usableSpace ){
-      szNew[k] = subtotal - szCell[i] - 2;
-      cntNew[k] = i;
-      if( leafData ){ i--; }
-      subtotal = 0;
-      k++;
-      if( k>NB+1 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
-    }
-  }
-  szNew[k] = subtotal;
-  cntNew[k] = nCell;
-  k++;
+  for(i=0; i<nOld; i++){
+    MemPage *p = apOld[i];
+    szNew[i] = usableSpace - p->nFree;
+    if( szNew[i]<0 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
+    for(j=0; j<p->nOverflow; j++){
+      szNew[i] += 2 + p->xCellSize(p, p->apOvfl[j]);
+    }
+    cntNew[i] = cntOld[i];
+  }
+  k = nOld;
+  for(i=0; i<k; i++){
+    int sz;
+    while( szNew[i]>usableSpace ){
+      if( i+1>=k ){
+        k = i+2;
+        if( k>NB+2 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
+        szNew[k-1] = 0;
+        cntNew[k-1] = b.nCell;
+      }
+      sz = 2 + cachedCellSize(&b, cntNew[i]-1);
+      szNew[i] -= sz;
+      if( !leafData ){
+        if( cntNew[i]<b.nCell ){
+          sz = 2 + cachedCellSize(&b, cntNew[i]);
+        }else{
+          sz = 0;
+        }
+      }
+      szNew[i+1] += sz;
+      cntNew[i]--;
+    }
+    while( cntNew[i]<b.nCell ){
+      sz = 2 + cachedCellSize(&b, cntNew[i]);
+      if( szNew[i]+sz>usableSpace ) break;
+      szNew[i] += sz;
+      cntNew[i]++;
+      if( !leafData ){
+        if( cntNew[i]<b.nCell ){
+          sz = 2 + cachedCellSize(&b, cntNew[i]);
+        }else{
+          sz = 0;
+        }
+      }
+      szNew[i+1] -= sz;
+    }
+    if( cntNew[i]>=b.nCell ){
+      k = i+1;
+    }else if( cntNew[i] <= (i>0 ? cntNew[i-1] : 0) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
+  }
 
   /*
   ** The packing computed by the previous block is biased toward the siblings
@@ -60002,19 +61068,27 @@ static int balance_nonroot(
 
     r = cntNew[i-1] - 1;
     d = r + 1 - leafData;
-    assert( d<nMaxCells );
-    assert( r<nMaxCells );
-    while( szRight==0 
-       || (!bBulk && szRight+szCell[d]+2<=szLeft-(szCell[r]+2)) 
-    ){
-      szRight += szCell[d] + 2;
-      szLeft -= szCell[r] + 2;
-      cntNew[i-1]--;
-      r = cntNew[i-1] - 1;
-      d = r + 1 - leafData;
-    }
+    (void)cachedCellSize(&b, d);
+    do{
+      assert( d<nMaxCells );
+      assert( r<nMaxCells );
+      (void)cachedCellSize(&b, r);
+      if( szRight!=0
+       && (bBulk || szRight+b.szCell[d]+2 > szLeft-(b.szCell[r]+2)) ){
+        break;
+      }
+      szRight += b.szCell[d] + 2;
+      szLeft -= b.szCell[r] + 2;
+      cntNew[i-1] = r;
+      r--;
+      d--;
+    }while( r>=0 );
     szNew[i] = szRight;
     szNew[i-1] = szLeft;
+    if( cntNew[i-1] <= (i>1 ? cntNew[i-2] : 0) ){
+      rc = SQLITE_CORRUPT_BKPT;
+      goto balance_cleanup;
+    }
   }
 
   /* Sanity check:  For a non-corrupt database file one of the follwing
@@ -60034,10 +61108,6 @@ static int balance_nonroot(
   /*
   ** Allocate k new pages.  Reuse old pages where possible.
   */
-  if( apOld[0]->pgno<=1 ){
-    rc = SQLITE_CORRUPT_BKPT;
-    goto balance_cleanup;
-  }
   pageFlags = apOld[0]->aData[0];
   for(i=0; i<k; i++){
     MemPage *pNew;
@@ -60054,7 +61124,7 @@ static int balance_nonroot(
       zeroPage(pNew, pageFlags);
       apNew[i] = pNew;
       nNew++;
-      cntOld[i] = nCell;
+      cntOld[i] = b.nCell;
 
       /* Set the pointer-map entry for the new sibling page. */
       if( ISAUTOVACUUM ){
@@ -60159,8 +61229,8 @@ static int balance_nonroot(
     int iNew = 0;
     int iOld = 0;
 
-    for(i=0; i<nCell; i++){
-      u8 *pCell = apCell[i];
+    for(i=0; i<b.nCell; i++){
+      u8 *pCell = b.apCell[i];
       if( i==cntOldNext ){
         MemPage *pOld = (++iOld)<nNew ? apNew[iOld] : apOld[iOld];
         cntOldNext += pOld->nCell + pOld->nOverflow + !leafData;
@@ -60185,9 +61255,10 @@ static int balance_nonroot(
         if( !leafCorrection ){
           ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno, &rc);
         }
-        if( szCell[i]>pNew->minLocal ){
+        if( cachedCellSize(&b,i)>pNew->minLocal ){
           ptrmapPutOvflPtr(pNew, pCell, &rc);
         }
+        if( rc ) goto balance_cleanup;
       }
     }
   }
@@ -60201,20 +61272,21 @@ static int balance_nonroot(
     j = cntNew[i];
 
     assert( j<nMaxCells );
-    pCell = apCell[j];
-    sz = szCell[j] + leafCorrection;
+    assert( b.apCell[j]!=0 );
+    pCell = b.apCell[j];
+    sz = b.szCell[j] + leafCorrection;
     pTemp = &aOvflSpace[iOvflSpace];
     if( !pNew->leaf ){
       memcpy(&pNew->aData[8], pCell, 4);
     }else if( leafData ){
       /* If the tree is a leaf-data tree, and the siblings are leaves, 
-      ** then there is no divider cell in apCell[]. Instead, the divider 
+      ** then there is no divider cell in b.apCell[]. Instead, the divider 
       ** cell consists of the integer key for the right-most cell of 
       ** the sibling-page assembled above only.
       */
       CellInfo info;
       j--;
-      btreeParseCellPtr(pNew, apCell[j], &info);
+      pNew->xParseCell(pNew, b.apCell[j], &info);
       pCell = pTemp;
       sz = 4 + putVarint(&pCell[4], info.nKey);
       pTemp = 0;
@@ -60231,9 +61303,9 @@ static int balance_nonroot(
       ** cells are at least 4 bytes. It only happens in b-trees used
       ** to evaluate "IN (SELECT ...)" and similar clauses.
       */
-      if( szCell[j]==4 ){
+      if( b.szCell[j]==4 ){
         assert(leafCorrection==4);
-        sz = cellSizePtr(pParent, pCell);
+        sz = pParent->xCellSize(pParent, pCell);
       }
     }
     iOvflSpace += sz;
@@ -60289,12 +61361,13 @@ static int balance_nonroot(
         iNew = iOld = 0;
         nNewCell = cntNew[0];
       }else{
-        iOld = iPg<nOld ? (cntOld[iPg-1] + !leafData) : nCell;
+        iOld = iPg<nOld ? (cntOld[iPg-1] + !leafData) : b.nCell;
         iNew = cntNew[iPg-1] + !leafData;
         nNewCell = cntNew[iPg] - iNew;
       }
 
-      editPage(apNew[iPg], iOld, iNew, nNewCell, apCell, szCell);
+      rc = editPage(apNew[iPg], iOld, iNew, nNewCell, &b);
+      if( rc ) goto balance_cleanup;
       abDone[iPg]++;
       apNew[iPg]->nFree = usableSpace-szNew[iPg];
       assert( apNew[iPg]->nOverflow==0 );
@@ -60345,7 +61418,7 @@ static int balance_nonroot(
 
   assert( pParent->isInit );
   TRACE(("BALANCE: finished: old=%d new=%d cells=%d\n",
-          nOld, nNew, nCell));
+          nOld, nNew, b.nCell));
 
   /* Free any old pages that were not reused as new pages.
   */
@@ -60368,7 +61441,7 @@ static int balance_nonroot(
   ** Cleanup before returning.
   */
 balance_cleanup:
-  sqlite3ScratchFree(apCell);
+  sqlite3ScratchFree(b.apCell);
   for(i=0; i<nOld; i++){
     releasePage(apOld[i]);
   }
@@ -60643,24 +61716,28 @@ SQLITE_PRIVATE int sqlite3BtreeInsert(
   ** doing any work. To avoid thwarting these optimizations, it is important
   ** not to clear the cursor here.
   */
-  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
-  if( rc ) return rc;
+  if( pCur->curFlags & BTCF_Multiple ){
+    rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
+    if( rc ) return rc;
+  }
 
   if( pCur->pKeyInfo==0 ){
+    assert( pKey==0 );
     /* If this is an insert into a table b-tree, invalidate any incrblob 
     ** cursors open on the row being replaced */
     invalidateIncrblobCursors(p, nKey, 0);
 
     /* If the cursor is currently on the last row and we are appending a
-    ** new row onto the end, set the "loc" to avoid an unnecessary btreeMoveto()
-    ** call */
+    ** new row onto the end, set the "loc" to avoid an unnecessary
+    ** btreeMoveto() call */
     if( (pCur->curFlags&BTCF_ValidNKey)!=0 && nKey>0
       && pCur->info.nKey==nKey-1 ){
-      loc = -1;
+       loc = -1;
+    }else if( loc==0 ){
+      rc = sqlite3BtreeMovetoUnpacked(pCur, 0, nKey, appendBias, &loc);
+      if( rc ) return rc;
     }
-  }
-
-  if( !loc ){
+  }else if( loc==0 ){
     rc = btreeMoveto(pCur, pKey, nKey, appendBias, &loc);
     if( rc ) return rc;
   }
@@ -60678,7 +61755,7 @@ SQLITE_PRIVATE int sqlite3BtreeInsert(
   assert( newCell!=0 );
   rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, nZero, &szNew);
   if( rc ) goto end_insert;
-  assert( szNew==cellSizePtr(pPage, newCell) );
+  assert( szNew==pPage->xCellSize(pPage, newCell) );
   assert( szNew <= MX_CELL_SIZE(pBt) );
   idx = pCur->aiIdx[pCur->iPage];
   if( loc==0 ){
@@ -60762,12 +61839,8 @@ SQLITE_PRIVATE int sqlite3BtreeDelete(BtCursor *pCur){
   assert( pCur->curFlags & BTCF_WriteFlag );
   assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
   assert( !hasReadConflicts(p, pCur->pgnoRoot) );
-
-  if( NEVER(pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell) 
-   || NEVER(pCur->eState!=CURSOR_VALID)
-  ){
-    return SQLITE_ERROR;  /* Something has gone awry. */
-  }
+  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
+  assert( pCur->eState==CURSOR_VALID );
 
   iCellDepth = pCur->iPage;
   iCellIdx = pCur->aiIdx[iCellDepth];
@@ -60792,8 +61865,10 @@ SQLITE_PRIVATE int sqlite3BtreeDelete(BtCursor *pCur){
   ** deleted writable. Then free any overflow pages associated with the 
   ** entry and finally remove the cell itself from within the page.  
   */
-  rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
-  if( rc ) return rc;
+  if( pCur->curFlags & BTCF_Multiple ){
+    rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
+    if( rc ) return rc;
+  }
 
   /* If this is a delete operation to remove a row from a table b-tree,
   ** invalidate any incrblob cursors open on the row being deleted.  */
@@ -60819,7 +61894,8 @@ SQLITE_PRIVATE int sqlite3BtreeDelete(BtCursor *pCur){
     unsigned char *pTmp;
 
     pCell = findCell(pLeaf, pLeaf->nCell-1);
-    nCell = cellSizePtr(pLeaf, pCell);
+    if( pCell<&pLeaf->aData[4] ) return SQLITE_CORRUPT_BKPT;
+    nCell = pLeaf->xCellSize(pLeaf, pCell);
     assert( MX_CELL_SIZE(pBt) >= nCell );
     pTmp = pBt->pTmpSpace;
     assert( pTmp!=0 );
@@ -60911,7 +61987,8 @@ static int btreeCreateTable(Btree *p, int *piTable, int createTabFlags){
         pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
       pgnoRoot++;
     }
-    assert( pgnoRoot>=3 );
+    assert( pgnoRoot>=3 || CORRUPT_DB );
+    testcase( pgnoRoot<3 );
 
     /* Allocate a page. The page that currently resides at pgnoRoot will
     ** be moved to the allocated page (unless the allocated page happens
@@ -61040,7 +62117,7 @@ static int clearDatabasePage(
   if( pgno>btreePagecount(pBt) ){
     return SQLITE_CORRUPT_BKPT;
   }
-  rc = getAndInitPage(pBt, pgno, &pPage, 0);
+  rc = getAndInitPage(pBt, pgno, &pPage, 0, 0);
   if( rc ) return rc;
   if( pPage->bBusy ){
     rc = SQLITE_CORRUPT_BKPT;
@@ -61061,7 +62138,8 @@ static int clearDatabasePage(
     rc = clearDatabasePage(pBt, get4byte(&pPage->aData[hdr+8]), 1, pnChange);
     if( rc ) goto cleardatabasepage_out;
   }else if( pnChange ){
-    assert( pPage->intKey );
+    assert( pPage->intKey || CORRUPT_DB );
+    testcase( !pPage->intKey );
     *pnChange += pPage->nCell;
   }
   if( freePageFlag ){
@@ -61640,35 +62718,42 @@ static int btreeHeapPull(u32 *aHeap, u32 *pOut){
 **
 **      1.  Make sure that cells and freeblocks do not overlap
 **          but combine to completely cover the page.
-**  NO  2.  Make sure cell keys are in order.
-**  NO  3.  Make sure no key is less than or equal to zLowerBound.
-**  NO  4.  Make sure no key is greater than or equal to zUpperBound.
-**      5.  Check the integrity of overflow pages.
-**      6.  Recursively call checkTreePage on all children.
-**      7.  Verify that the depth of all children is the same.
-**      8.  Make sure this page is at least 33% full or else it is
-**          the root of the tree.
+**      2.  Make sure integer cell keys are in order.
+**      3.  Check the integrity of overflow pages.
+**      4.  Recursively call checkTreePage on all children.
+**      5.  Verify that the depth of all children is the same.
 */
 static int checkTreePage(
   IntegrityCk *pCheck,  /* Context for the sanity check */
   int iPage,            /* Page number of the page to check */
-  i64 *pnParentMinKey, 
-  i64 *pnParentMaxKey
+  i64 *piMinKey,        /* Write minimum integer primary key here */
+  i64 maxKey            /* Error if integer primary key greater than this */
 ){
-  MemPage *pPage;
-  int i, rc, depth, d2, pgno, cnt;
-  int hdr, cellStart;
-  int nCell;
-  u8 *data;
-  BtShared *pBt;
-  int usableSize;
-  u32 *heap = 0;
-  u32 x, prev = 0;
-  i64 nMinKey = 0;
-  i64 nMaxKey = 0;
+  MemPage *pPage = 0;      /* The page being analyzed */
+  int i;                   /* Loop counter */
+  int rc;                  /* Result code from subroutine call */
+  int depth = -1, d2;      /* Depth of a subtree */
+  int pgno;                /* Page number */
+  int nFrag;               /* Number of fragmented bytes on the page */
+  int hdr;                 /* Offset to the page header */
+  int cellStart;           /* Offset to the start of the cell pointer array */
+  int nCell;               /* Number of cells */
+  int doCoverageCheck = 1; /* True if cell coverage checking should be done */
+  int keyCanBeEqual = 1;   /* True if IPK can be equal to maxKey
+                           ** False if IPK must be strictly less than maxKey */
+  u8 *data;                /* Page content */
+  u8 *pCell;               /* Cell content */
+  u8 *pCellIdx;            /* Next element of the cell pointer array */
+  BtShared *pBt;           /* The BtShared object that owns pPage */
+  u32 pc;                  /* Address of a cell */
+  u32 usableSize;          /* Usable size of the page */
+  u32 contentOffset;       /* Offset to the start of the cell content area */
+  u32 *heap = 0;           /* Min-heap used for checking cell coverage */
+  u32 x, prev = 0;         /* Next and previous entry on the min-heap */
   const char *saved_zPfx = pCheck->zPfx;
   int saved_v1 = pCheck->v1;
   int saved_v2 = pCheck->v2;
+  u8 savedIsInit = 0;
 
   /* Check that the page exists
   */
@@ -61681,54 +62766,95 @@ static int checkTreePage(
   if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
     checkAppendMsg(pCheck,
        "unable to get the page. error code=%d", rc);
-    depth = -1;
     goto end_of_check;
   }
 
   /* Clear MemPage.isInit to make sure the corruption detection code in
   ** btreeInitPage() is executed.  */
+  savedIsInit = pPage->isInit;
   pPage->isInit = 0;
   if( (rc = btreeInitPage(pPage))!=0 ){
     assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
     checkAppendMsg(pCheck,
                    "btreeInitPage() returns error code %d", rc);
-    releasePage(pPage);
-    depth = -1;
     goto end_of_check;
   }
+  data = pPage->aData;
+  hdr = pPage->hdrOffset;
+
+  /* Set up for cell analysis */
+  pCheck->zPfx = "On tree page %d cell %d: ";
+  contentOffset = get2byteNotZero(&data[hdr+5]);
+  assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
+
+  /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
+  ** number of cells on the page. */
+  nCell = get2byte(&data[hdr+3]);
+  assert( pPage->nCell==nCell );
+
+  /* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
+  ** immediately follows the b-tree page header. */
+  cellStart = hdr + 12 - 4*pPage->leaf;
+  assert( pPage->aCellIdx==&data[cellStart] );
+  pCellIdx = &data[cellStart + 2*(nCell-1)];
+
+  if( !pPage->leaf ){
+    /* Analyze the right-child page of internal pages */
+    pgno = get4byte(&data[hdr+8]);
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    if( pBt->autoVacuum ){
+      pCheck->zPfx = "On page %d at right child: ";
+      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
+    }
+#endif
+    depth = checkTreePage(pCheck, pgno, &maxKey, maxKey);
+    keyCanBeEqual = 0;
+  }else{
+    /* For leaf pages, the coverage check will occur in the same loop
+    ** as the other cell checks, so initialize the heap.  */
+    heap = pCheck->heap;
+    heap[0] = 0;
+  }
 
-  /* Check out all the cells.
-  */
-  depth = 0;
-  for(i=0; i<pPage->nCell && pCheck->mxErr; i++){
-    u8 *pCell;
-    u32 sz;
+  /* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
+  ** integer offsets to the cell contents. */
+  for(i=nCell-1; i>=0 && pCheck->mxErr; i--){
     CellInfo info;
 
-    /* Check payload overflow pages
-    */
-    pCheck->zPfx = "On tree page %d cell %d: ";
-    pCheck->v1 = iPage;
+    /* Check cell size */
     pCheck->v2 = i;
-    pCell = findCell(pPage,i);
-    btreeParseCellPtr(pPage, pCell, &info);
-    sz = info.nPayload;
-    /* For intKey pages, check that the keys are in order.
-    */
+    assert( pCellIdx==&data[cellStart + i*2] );
+    pc = get2byteAligned(pCellIdx);
+    pCellIdx -= 2;
+    if( pc<contentOffset || pc>usableSize-4 ){
+      checkAppendMsg(pCheck, "Offset %d out of range %d..%d",
+                             pc, contentOffset, usableSize-4);
+      doCoverageCheck = 0;
+      continue;
+    }
+    pCell = &data[pc];
+    pPage->xParseCell(pPage, pCell, &info);
+    if( pc+info.nSize>usableSize ){
+      checkAppendMsg(pCheck, "Extends off end of page");
+      doCoverageCheck = 0;
+      continue;
+    }
+
+    /* Check for integer primary key out of range */
     if( pPage->intKey ){
-      if( i==0 ){
-        nMinKey = nMaxKey = info.nKey;
-      }else if( info.nKey <= nMaxKey ){
-        checkAppendMsg(pCheck,
-           "Rowid %lld out of order (previous was %lld)", info.nKey, nMaxKey);
+      if( keyCanBeEqual ? (info.nKey > maxKey) : (info.nKey >= maxKey) ){
+        checkAppendMsg(pCheck, "Rowid %lld out of order", info.nKey);
       }
-      nMaxKey = info.nKey;
+      maxKey = info.nKey;
     }
-    if( (sz>info.nLocal) 
-     && (&pCell[info.iOverflow]<=&pPage->aData[pBt->usableSize])
-    ){
-      int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
-      Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
+
+    /* Check the content overflow list */
+    if( info.nPayload>info.nLocal ){
+      int nPage;       /* Number of pages on the overflow chain */
+      Pgno pgnoOvfl;   /* First page of the overflow chain */
+      assert( pc + info.iOverflow <= usableSize );
+      nPage = (info.nPayload - info.nLocal + usableSize - 5)/(usableSize - 4);
+      pgnoOvfl = get4byte(&pCell[info.iOverflow]);
 #ifndef SQLITE_OMIT_AUTOVACUUM
       if( pBt->autoVacuum ){
         checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
@@ -61737,118 +62863,57 @@ static int checkTreePage(
       checkList(pCheck, 0, pgnoOvfl, nPage);
     }
 
-    /* Check sanity of left child page.
-    */
     if( !pPage->leaf ){
+      /* Check sanity of left child page for internal pages */
       pgno = get4byte(pCell);
 #ifndef SQLITE_OMIT_AUTOVACUUM
       if( pBt->autoVacuum ){
         checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
       }
 #endif
-      d2 = checkTreePage(pCheck, pgno, &nMinKey, i==0?NULL:&nMaxKey);
-      if( i>0 && d2!=depth ){
+      d2 = checkTreePage(pCheck, pgno, &maxKey, maxKey);
+      keyCanBeEqual = 0;
+      if( d2!=depth ){
         checkAppendMsg(pCheck, "Child page depth differs");
+        depth = d2;
       }
-      depth = d2;
-    }
-  }
-
-  if( !pPage->leaf ){
-    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
-    pCheck->zPfx = "On page %d at right child: ";
-    pCheck->v1 = iPage;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum ){
-      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
-    }
-#endif
-    checkTreePage(pCheck, pgno, NULL, !pPage->nCell?NULL:&nMaxKey);
-  }
- 
-  /* For intKey leaf pages, check that the min/max keys are in order
-  ** with any left/parent/right pages.
-  */
-  pCheck->zPfx = "Page %d: ";
-  pCheck->v1 = iPage;
-  if( pPage->leaf && pPage->intKey ){
-    /* if we are a left child page */
-    if( pnParentMinKey ){
-      /* if we are the left most child page */
-      if( !pnParentMaxKey ){
-        if( nMaxKey > *pnParentMinKey ){
-          checkAppendMsg(pCheck,
-              "Rowid %lld out of order (max larger than parent min of %lld)",
-              nMaxKey, *pnParentMinKey);
-        }
-      }else{
-        if( nMinKey <= *pnParentMinKey ){
-          checkAppendMsg(pCheck,
-              "Rowid %lld out of order (min less than parent min of %lld)",
-              nMinKey, *pnParentMinKey);
-        }
-        if( nMaxKey > *pnParentMaxKey ){
-          checkAppendMsg(pCheck,
-              "Rowid %lld out of order (max larger than parent max of %lld)",
-              nMaxKey, *pnParentMaxKey);
-        }
-        *pnParentMinKey = nMaxKey;
-      }
-    /* else if we're a right child page */
-    } else if( pnParentMaxKey ){
-      if( nMinKey <= *pnParentMaxKey ){
-        checkAppendMsg(pCheck,
-            "Rowid %lld out of order (min less than parent max of %lld)",
-            nMinKey, *pnParentMaxKey);
-      }
+    }else{
+      /* Populate the coverage-checking heap for leaf pages */
+      btreeHeapInsert(heap, (pc<<16)|(pc+info.nSize-1));
     }
   }
+  *piMinKey = maxKey;
 
   /* Check for complete coverage of the page
   */
-  data = pPage->aData;
-  hdr = pPage->hdrOffset;
-  heap = (u32*)sqlite3PageMalloc( pBt->pageSize );
   pCheck->zPfx = 0;
-  if( heap==0 ){
-    pCheck->mallocFailed = 1;
-  }else{
-    int contentOffset = get2byteNotZero(&data[hdr+5]);
-    assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
-    heap[0] = 0;
-    btreeHeapInsert(heap, contentOffset-1);
-    /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
-    ** number of cells on the page. */
-    nCell = get2byte(&data[hdr+3]);
-    /* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
-    ** immediately follows the b-tree page header. */
-    cellStart = hdr + 12 - 4*pPage->leaf;
-    /* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
-    ** integer offsets to the cell contents. */
-    for(i=0; i<nCell; i++){
-      int pc = get2byte(&data[cellStart+i*2]);
-      u32 size = 65536;
-      if( pc<=usableSize-4 ){
-        size = cellSizePtr(pPage, &data[pc]);
-      }
-      if( (int)(pc+size-1)>=usableSize ){
-        pCheck->zPfx = 0;
-        checkAppendMsg(pCheck,
-            "Corruption detected in cell %d on page %d",i,iPage);
-      }else{
+  if( doCoverageCheck && pCheck->mxErr>0 ){
+    /* For leaf pages, the min-heap has already been initialized and the
+    ** cells have already been inserted.  But for internal pages, that has
+    ** not yet been done, so do it now */
+    if( !pPage->leaf ){
+      heap = pCheck->heap;
+      heap[0] = 0;
+      for(i=nCell-1; i>=0; i--){
+        u32 size;
+        pc = get2byteAligned(&data[cellStart+i*2]);
+        size = pPage->xCellSize(pPage, &data[pc]);
         btreeHeapInsert(heap, (pc<<16)|(pc+size-1));
       }
     }
-    /* EVIDENCE-OF: R-20690-50594 The second field of the b-tree page header
+    /* Add the freeblocks to the min-heap
+    **
+    ** EVIDENCE-OF: R-20690-50594 The second field of the b-tree page header
     ** is the offset of the first freeblock, or zero if there are no
-    ** freeblocks on the page. */
+    ** freeblocks on the page. 
+    */
     i = get2byte(&data[hdr+1]);
     while( i>0 ){
       int size, j;
-      assert( i<=usableSize-4 );     /* Enforced by btreeInitPage() */
+      assert( (u32)i<=usableSize-4 );     /* Enforced by btreeInitPage() */
       size = get2byte(&data[i+2]);
-      assert( i+size<=usableSize );  /* Enforced by btreeInitPage() */
-      btreeHeapInsert(heap, (i<<16)|(i+size-1));
+      assert( (u32)(i+size)<=usableSize );  /* Enforced by btreeInitPage() */
+      btreeHeapInsert(heap, (((u32)i)<<16)|(i+size-1));
       /* EVIDENCE-OF: R-58208-19414 The first 2 bytes of a freeblock are a
       ** big-endian integer which is the offset in the b-tree page of the next
       ** freeblock in the chain, or zero if the freeblock is the last on the
@@ -61857,39 +62922,50 @@ static int checkTreePage(
       /* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
       ** increasing offset. */
       assert( j==0 || j>i+size );  /* Enforced by btreeInitPage() */
-      assert( j<=usableSize-4 );   /* Enforced by btreeInitPage() */
+      assert( (u32)j<=usableSize-4 );   /* Enforced by btreeInitPage() */
       i = j;
     }
-    cnt = 0;
-    assert( heap[0]>0 );
-    assert( (heap[1]>>16)==0 );
-    btreeHeapPull(heap,&prev);
+    /* Analyze the min-heap looking for overlap between cells and/or 
+    ** freeblocks, and counting the number of untracked bytes in nFrag.
+    ** 
+    ** Each min-heap entry is of the form:    (start_address<<16)|end_address.
+    ** There is an implied first entry the covers the page header, the cell
+    ** pointer index, and the gap between the cell pointer index and the start
+    ** of cell content.  
+    **
+    ** The loop below pulls entries from the min-heap in order and compares
+    ** the start_address against the previous end_address.  If there is an
+    ** overlap, that means bytes are used multiple times.  If there is a gap,
+    ** that gap is added to the fragmentation count.
+    */
+    nFrag = 0;
+    prev = contentOffset - 1;   /* Implied first min-heap entry */
     while( btreeHeapPull(heap,&x) ){
-      if( (prev&0xffff)+1>(x>>16) ){
+      if( (prev&0xffff)>=(x>>16) ){
         checkAppendMsg(pCheck,
           "Multiple uses for byte %u of page %d", x>>16, iPage);
         break;
       }else{
-        cnt += (x>>16) - (prev&0xffff) - 1;
+        nFrag += (x>>16) - (prev&0xffff) - 1;
         prev = x;
       }
     }
-    cnt += usableSize - (prev&0xffff) - 1;
+    nFrag += usableSize - (prev&0xffff) - 1;
     /* EVIDENCE-OF: R-43263-13491 The total number of bytes in all fragments
     ** is stored in the fifth field of the b-tree page header.
     ** EVIDENCE-OF: R-07161-27322 The one-byte integer at offset 7 gives the
     ** number of fragmented free bytes within the cell content area.
     */
-    if( heap[0]==0 && cnt!=data[hdr+7] ){
+    if( heap[0]==0 && nFrag!=data[hdr+7] ){
       checkAppendMsg(pCheck,
           "Fragmentation of %d bytes reported as %d on page %d",
-          cnt, data[hdr+7], iPage);
+          nFrag, data[hdr+7], iPage);
     }
   }
-  sqlite3PageFree(heap);
-  releasePage(pPage);
 
 end_of_check:
+  if( !doCoverageCheck ) pPage->isInit = savedIsInit;
+  releasePage(pPage);
   pCheck->zPfx = saved_zPfx;
   pCheck->v1 = saved_v1;
   pCheck->v2 = saved_v2;
@@ -61919,14 +62995,15 @@ SQLITE_PRIVATE char *sqlite3BtreeIntegrityCheck(
   int *pnErr    /* Write number of errors seen to this variable */
 ){
   Pgno i;
-  int nRef;
   IntegrityCk sCheck;
   BtShared *pBt = p->pBt;
+  int savedDbFlags = pBt->db->flags;
   char zErr[100];
+  VVA_ONLY( int nRef );
 
   sqlite3BtreeEnter(p);
   assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
-  nRef = sqlite3PagerRefcount(pBt->pPager);
+  assert( (nRef = sqlite3PagerRefcount(pBt->pPager))>=0 );
   sCheck.pBt = pBt;
   sCheck.pPager = pBt->pPager;
   sCheck.nPage = btreePagecount(sCheck.pBt);
@@ -61936,21 +63013,26 @@ SQLITE_PRIVATE char *sqlite3BtreeIntegrityCheck(
   sCheck.zPfx = 0;
   sCheck.v1 = 0;
   sCheck.v2 = 0;
-  *pnErr = 0;
+  sCheck.aPgRef = 0;
+  sCheck.heap = 0;
+  sqlite3StrAccumInit(&sCheck.errMsg, 0, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
   if( sCheck.nPage==0 ){
-    sqlite3BtreeLeave(p);
-    return 0;
+    goto integrity_ck_cleanup;
   }
 
   sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
   if( !sCheck.aPgRef ){
-    *pnErr = 1;
-    sqlite3BtreeLeave(p);
-    return 0;
+    sCheck.mallocFailed = 1;
+    goto integrity_ck_cleanup;
   }
+  sCheck.heap = (u32*)sqlite3PageMalloc( pBt->pageSize );
+  if( sCheck.heap==0 ){
+    sCheck.mallocFailed = 1;
+    goto integrity_ck_cleanup;
+  }
+
   i = PENDING_BYTE_PAGE(pBt);
   if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
-  sqlite3StrAccumInit(&sCheck.errMsg, 0, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
 
   /* Check the integrity of the freelist
   */
@@ -61961,17 +63043,19 @@ SQLITE_PRIVATE char *sqlite3BtreeIntegrityCheck(
 
   /* Check all the tables.
   */
+  testcase( pBt->db->flags & SQLITE_CellSizeCk );
+  pBt->db->flags &= ~SQLITE_CellSizeCk;
   for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
+    i64 notUsed;
     if( aRoot[i]==0 ) continue;
 #ifndef SQLITE_OMIT_AUTOVACUUM
     if( pBt->autoVacuum && aRoot[i]>1 ){
       checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0);
     }
 #endif
-    sCheck.zPfx = "List of tree roots: ";
-    checkTreePage(&sCheck, aRoot[i], NULL, NULL);
-    sCheck.zPfx = 0;
+    checkTreePage(&sCheck, aRoot[i], &notUsed, LARGEST_INT64);
   }
+  pBt->db->flags = savedDbFlags;
 
   /* Make sure every page in the file is referenced
   */
@@ -61995,28 +63079,20 @@ SQLITE_PRIVATE char *sqlite3BtreeIntegrityCheck(
 #endif
   }
 
-  /* Make sure this analysis did not leave any unref() pages.
-  ** This is an internal consistency check; an integrity check
-  ** of the integrity check.
-  */
-  if( NEVER(nRef != sqlite3PagerRefcount(pBt->pPager)) ){
-    checkAppendMsg(&sCheck,
-      "Outstanding page count goes from %d to %d during this analysis",
-      nRef, sqlite3PagerRefcount(pBt->pPager)
-    );
-  }
-
   /* Clean  up and report errors.
   */
-  sqlite3BtreeLeave(p);
+integrity_ck_cleanup:
+  sqlite3PageFree(sCheck.heap);
   sqlite3_free(sCheck.aPgRef);
   if( sCheck.mallocFailed ){
     sqlite3StrAccumReset(&sCheck.errMsg);
-    *pnErr = sCheck.nErr+1;
-    return 0;
+    sCheck.nErr++;
   }
   *pnErr = sCheck.nErr;
   if( sCheck.nErr==0 ) sqlite3StrAccumReset(&sCheck.errMsg);
+  /* Make sure this analysis did not leave any unref() pages. */
+  assert( nRef==sqlite3PagerRefcount(pBt->pPager) );
+  sqlite3BtreeLeave(p);
   return sqlite3StrAccumFinish(&sCheck.errMsg);
 }
 #endif /* SQLITE_OMIT_INTEGRITY_CHECK */
@@ -62227,6 +63303,7 @@ SQLITE_PRIVATE int sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void
 */
 SQLITE_PRIVATE void sqlite3BtreeIncrblobCursor(BtCursor *pCur){
   pCur->curFlags |= BTCF_Incrblob;
+  pCur->pBtree->hasIncrblobCur = 1;
 }
 #endif
 
@@ -62312,6 +63389,8 @@ SQLITE_PRIVATE int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage));
 ** This file contains the implementation of the sqlite3_backup_XXX() 
 ** API functions and the related features.
 */
+/* #include "sqliteInt.h" */
+/* #include "btreeInt.h" */
 
 /*
 ** Structure allocated for each backup operation.
@@ -62983,9 +64062,13 @@ SQLITE_API int SQLITE_STDCALL sqlite3_backup_pagecount(sqlite3_backup *p){
 ** corresponding to the source database is held when this function is
 ** called.
 */
-SQLITE_PRIVATE void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
-  sqlite3_backup *p;                   /* Iterator variable */
-  for(p=pBackup; p; p=p->pNext){
+static SQLITE_NOINLINE void backupUpdate(
+  sqlite3_backup *p,
+  Pgno iPage,
+  const u8 *aData
+){
+  assert( p!=0 );
+  do{
     assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
     if( !isFatalError(p->rc) && iPage<p->iNext ){
       /* The backup process p has already copied page iPage. But now it
@@ -63002,7 +64085,10 @@ SQLITE_PRIVATE void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, con
         p->rc = rc;
       }
     }
-  }
+  }while( (p = p->pNext)!=0 );
+}
+SQLITE_PRIVATE void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
+  if( pBackup ) backupUpdate(pBackup, iPage, aData);
 }
 
 /*
@@ -63103,6 +64189,8 @@ copy_finished:
 ** only within the VDBE.  Interface routines refer to a Mem using the
 ** name sqlite_value
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 #ifdef SQLITE_DEBUG
 /*
@@ -63674,7 +64762,7 @@ SQLITE_PRIVATE int sqlite3VdbeMemNumerify(Mem *pMem){
 SQLITE_PRIVATE void sqlite3VdbeMemCast(Mem *pMem, u8 aff, u8 encoding){
   if( pMem->flags & MEM_Null ) return;
   switch( aff ){
-    case SQLITE_AFF_NONE: {   /* Really a cast to BLOB */
+    case SQLITE_AFF_BLOB: {   /* Really a cast to BLOB */
       if( (pMem->flags & MEM_Blob)==0 ){
         sqlite3ValueApplyAffinity(pMem, SQLITE_AFF_TEXT, encoding);
         assert( pMem->flags & MEM_Str || pMem->db->mallocFailed );
@@ -63856,10 +64944,6 @@ SQLITE_PRIVATE void sqlite3VdbeMemAboutToChange(Vdbe *pVdbe, Mem *pMem){
 }
 #endif /* SQLITE_DEBUG */
 
-/*
-** Size of struct Mem not including the Mem.zMalloc member.
-*/
-#define MEMCELLSIZE offsetof(Mem,zMalloc)
 
 /*
 ** Make an shallow copy of pFrom into pTo.  Prior contents of
@@ -63867,10 +64951,15 @@ SQLITE_PRIVATE void sqlite3VdbeMemAboutToChange(Vdbe *pVdbe, Mem *pMem){
 ** pFrom->z is used, then pTo->z points to the same thing as pFrom->z
 ** and flags gets srcType (either MEM_Ephem or MEM_Static).
 */
+static SQLITE_NOINLINE void vdbeClrCopy(Mem *pTo, const Mem *pFrom, int eType){
+  vdbeMemClearExternAndSetNull(pTo);
+  assert( !VdbeMemDynamic(pTo) );
+  sqlite3VdbeMemShallowCopy(pTo, pFrom, eType);
+}
 SQLITE_PRIVATE void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType){
   assert( (pFrom->flags & MEM_RowSet)==0 );
   assert( pTo->db==pFrom->db );
-  if( VdbeMemDynamic(pTo) ) vdbeMemClearExternAndSetNull(pTo);
+  if( VdbeMemDynamic(pTo) ){ vdbeClrCopy(pTo,pFrom,srcType); return; }
   memcpy(pTo, pFrom, MEMCELLSIZE);
   if( (pFrom->flags&MEM_Static)==0 ){
     pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
@@ -63886,7 +64975,10 @@ SQLITE_PRIVATE void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int sr
 SQLITE_PRIVATE int sqlite3VdbeMemCopy(Mem *pTo, const Mem *pFrom){
   int rc = SQLITE_OK;
 
-  assert( pTo->db==pFrom->db );
+  /* The pFrom==0 case in the following assert() is when an sqlite3_value
+  ** from sqlite3_value_dup() is used as the argument
+  ** to sqlite3_result_value(). */
+  assert( pTo->db==pFrom->db || pFrom->db==0 );
   assert( (pFrom->flags & MEM_RowSet)==0 );
   if( VdbeMemDynamic(pTo) ) vdbeMemClearExternAndSetNull(pTo);
   memcpy(pTo, pFrom, MEMCELLSIZE);
@@ -64033,6 +65125,32 @@ SQLITE_PRIVATE int sqlite3VdbeMemSetStr(
 ** If this routine fails for any reason (malloc returns NULL or unable
 ** to read from the disk) then the pMem is left in an inconsistent state.
 */
+static SQLITE_NOINLINE int vdbeMemFromBtreeResize(
+  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
+  u32 offset,       /* Offset from the start of data to return bytes from. */
+  u32 amt,          /* Number of bytes to return. */
+  int key,          /* If true, retrieve from the btree key, not data. */
+  Mem *pMem         /* OUT: Return data in this Mem structure. */
+){
+  int rc;
+  pMem->flags = MEM_Null;
+  if( SQLITE_OK==(rc = sqlite3VdbeMemClearAndResize(pMem, amt+2)) ){
+    if( key ){
+      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
+    }else{
+      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
+    }
+    if( rc==SQLITE_OK ){
+      pMem->z[amt] = 0;
+      pMem->z[amt+1] = 0;
+      pMem->flags = MEM_Blob|MEM_Term;
+      pMem->n = (int)amt;
+    }else{
+      sqlite3VdbeMemRelease(pMem);
+    }
+  }
+  return rc;
+}
 SQLITE_PRIVATE int sqlite3VdbeMemFromBtree(
   BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
   u32 offset,       /* Offset from the start of data to return bytes from. */
@@ -64062,22 +65180,7 @@ SQLITE_PRIVATE int sqlite3VdbeMemFromBtree(
     pMem->flags = MEM_Blob|MEM_Ephem;
     pMem->n = (int)amt;
   }else{
-    pMem->flags = MEM_Null;
-    if( SQLITE_OK==(rc = sqlite3VdbeMemClearAndResize(pMem, amt+2)) ){
-      if( key ){
-        rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
-      }else{
-        rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
-      }
-      if( rc==SQLITE_OK ){
-        pMem->z[amt] = 0;
-        pMem->z[amt+1] = 0;
-        pMem->flags = MEM_Blob|MEM_Term;
-        pMem->n = (int)amt;
-      }else{
-        sqlite3VdbeMemRelease(pMem);
-      }
-    }
+    rc = vdbeMemFromBtreeResize(pCur, offset, amt, key, pMem);
   }
 
   return rc;
@@ -64398,7 +65501,7 @@ static int valueFromExpr(
       if( zVal==0 ) goto no_mem;
       sqlite3ValueSetStr(pVal, -1, zVal, SQLITE_UTF8, SQLITE_DYNAMIC);
     }
-    if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_NONE ){
+    if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_BLOB ){
       sqlite3ValueApplyAffinity(pVal, SQLITE_AFF_NUMERIC, SQLITE_UTF8);
     }else{
       sqlite3ValueApplyAffinity(pVal, affinity, SQLITE_UTF8);
@@ -64765,19 +65868,28 @@ SQLITE_PRIVATE void sqlite3ValueFree(sqlite3_value *v){
 }
 
 /*
-** Return the number of bytes in the sqlite3_value object assuming
-** that it uses the encoding "enc"
+** The sqlite3ValueBytes() routine returns the number of bytes in the
+** sqlite3_value object assuming that it uses the encoding "enc".
+** The valueBytes() routine is a helper function.
 */
+static SQLITE_NOINLINE int valueBytes(sqlite3_value *pVal, u8 enc){
+  return valueToText(pVal, enc)!=0 ? pVal->n : 0;
+}
 SQLITE_PRIVATE int sqlite3ValueBytes(sqlite3_value *pVal, u8 enc){
   Mem *p = (Mem*)pVal;
-  if( (p->flags & MEM_Blob)!=0 || sqlite3ValueText(pVal, enc) ){
+  assert( (p->flags & MEM_Null)==0 || (p->flags & (MEM_Str|MEM_Blob))==0 );
+  if( (p->flags & MEM_Str)!=0 && pVal->enc==enc ){
+    return p->n;
+  }
+  if( (p->flags & MEM_Blob)!=0 ){
     if( p->flags & MEM_Zero ){
       return p->n + p->u.nZero;
     }else{
       return p->n;
     }
   }
-  return 0;
+  if( p->flags & MEM_Null ) return 0;
+  return valueBytes(pVal, enc);
 }
 
 /************** End of vdbemem.c *********************************************/
@@ -64796,6 +65908,8 @@ SQLITE_PRIVATE int sqlite3ValueBytes(sqlite3_value *pVal, u8 enc){
 ** This file contains code used for creating, destroying, and populating
 ** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.) 
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 /*
 ** Create a new virtual database engine.
@@ -64820,6 +65934,17 @@ SQLITE_PRIVATE Vdbe *sqlite3VdbeCreate(Parse *pParse){
   return p;
 }
 
+/*
+** Change the error string stored in Vdbe.zErrMsg
+*/
+SQLITE_PRIVATE void sqlite3VdbeError(Vdbe *p, const char *zFormat, ...){
+  va_list ap;
+  sqlite3DbFree(p->db, p->zErrMsg);
+  va_start(ap, zFormat);
+  p->zErrMsg = sqlite3VMPrintf(p->db, zFormat, ap);
+  va_end(ap);
+}
+
 /*
 ** Remember the SQL string for a prepared statement.
 */
@@ -65004,6 +66129,23 @@ SQLITE_PRIVATE int sqlite3VdbeAddOp4(
   return addr;
 }
 
+/*
+** Add an opcode that includes the p4 value with a P4_INT64 type.
+*/
+SQLITE_PRIVATE int sqlite3VdbeAddOp4Dup8(
+  Vdbe *p,            /* Add the opcode to this VM */
+  int op,             /* The new opcode */
+  int p1,             /* The P1 operand */
+  int p2,             /* The P2 operand */
+  int p3,             /* The P3 operand */
+  const u8 *zP4,      /* The P4 operand */
+  int p4type          /* P4 operand type */
+){
+  char *p4copy = sqlite3DbMallocRaw(sqlite3VdbeDb(p), 8);
+  if( p4copy ) memcpy(p4copy, zP4, 8);
+  return sqlite3VdbeAddOp4(p, op, p1, p2, p3, p4copy, p4type);
+}
+
 /*
 ** Add an OP_ParseSchema opcode.  This routine is broken out from
 ** sqlite3VdbeAddOp4() since it needs to also needs to mark all btrees
@@ -65168,6 +66310,7 @@ static Op *opIterNext(VdbeOpIter *p){
 **   *  OP_VUpdate
 **   *  OP_VRename
 **   *  OP_FkCounter with P2==0 (immediate foreign key constraint)
+**   *  OP_CreateTable and OP_InitCoroutine (for CREATE TABLE AS SELECT ...)
 **
 ** Then check that the value of Parse.mayAbort is true if an
 ** ABORT may be thrown, or false otherwise. Return true if it does
@@ -65179,6 +66322,8 @@ static Op *opIterNext(VdbeOpIter *p){
 SQLITE_PRIVATE int sqlite3VdbeAssertMayAbort(Vdbe *v, int mayAbort){
   int hasAbort = 0;
   int hasFkCounter = 0;
+  int hasCreateTable = 0;
+  int hasInitCoroutine = 0;
   Op *pOp;
   VdbeOpIter sIter;
   memset(&sIter, 0, sizeof(sIter));
@@ -65193,6 +66338,8 @@ SQLITE_PRIVATE int sqlite3VdbeAssertMayAbort(Vdbe *v, int mayAbort){
       hasAbort = 1;
       break;
     }
+    if( opcode==OP_CreateTable ) hasCreateTable = 1;
+    if( opcode==OP_InitCoroutine ) hasInitCoroutine = 1;
 #ifndef SQLITE_OMIT_FOREIGN_KEY
     if( opcode==OP_FkCounter && pOp->p1==0 && pOp->p2==1 ){
       hasFkCounter = 1;
@@ -65206,7 +66353,8 @@ SQLITE_PRIVATE int sqlite3VdbeAssertMayAbort(Vdbe *v, int mayAbort){
   ** through all opcodes and hasAbort may be set incorrectly. Return
   ** true for this case to prevent the assert() in the callers frame
   ** from failing.  */
-  return ( v->db->mallocFailed || hasAbort==mayAbort || hasFkCounter );
+  return ( v->db->mallocFailed || hasAbort==mayAbort || hasFkCounter
+              || (hasCreateTable && hasInitCoroutine) );
 }
 #endif /* SQLITE_DEBUG - the sqlite3AssertMayAbort() function */
 
@@ -65237,11 +66385,6 @@ static void resolveP2Values(Vdbe *p, int *pMaxFuncArgs){
     /* NOTE: Be sure to update mkopcodeh.awk when adding or removing
     ** cases from this switch! */
     switch( opcode ){
-      case OP_Function:
-      case OP_AggStep: {
-        if( pOp->p5>nMaxArgs ) nMaxArgs = pOp->p5;
-        break;
-      }
       case OP_Transaction: {
         if( pOp->p2!=0 ) p->readOnly = 0;
         /* fall thru */
@@ -65485,6 +66628,10 @@ static void freeP4(sqlite3 *db, int p4type, void *p4){
   if( p4 ){
     assert( db );
     switch( p4type ){
+      case P4_FUNCCTX: {
+        freeEphemeralFunction(db, ((sqlite3_context*)p4)->pFunc);
+        /* Fall through into the next case */
+      }
       case P4_REAL:
       case P4_INT64:
       case P4_DYNAMIC:
@@ -65869,6 +67016,13 @@ static char *displayP4(Op *pOp, char *zTemp, int nTemp){
       sqlite3_snprintf(nTemp, zTemp, "%s(%d)", pDef->zName, pDef->nArg);
       break;
     }
+#ifdef SQLITE_DEBUG
+    case P4_FUNCCTX: {
+      FuncDef *pDef = pOp->p4.pCtx->pFunc;
+      sqlite3_snprintf(nTemp, zTemp, "%s(%d)", pDef->zName, pDef->nArg);
+      break;
+    }
+#endif
     case P4_INT64: {
       sqlite3_snprintf(nTemp, zTemp, "%lld", *pOp->p4.pI64);
       break;
@@ -65989,12 +67143,11 @@ SQLITE_PRIVATE void sqlite3VdbeEnter(Vdbe *p){
 /*
 ** Unlock all of the btrees previously locked by a call to sqlite3VdbeEnter().
 */
-SQLITE_PRIVATE void sqlite3VdbeLeave(Vdbe *p){
+static SQLITE_NOINLINE void vdbeLeave(Vdbe *p){
   int i;
   sqlite3 *db;
   Db *aDb;
   int nDb;
-  if( DbMaskAllZero(p->lockMask) ) return;  /* The common case */
   db = p->db;
   aDb = db->aDb;
   nDb = db->nDb;
@@ -66004,6 +67157,10 @@ SQLITE_PRIVATE void sqlite3VdbeLeave(Vdbe *p){
     }
   }
 }
+SQLITE_PRIVATE void sqlite3VdbeLeave(Vdbe *p){
+  if( DbMaskAllZero(p->lockMask) ) return;  /* The common case */
+  vdbeLeave(p);
+}
 #endif
 
 #if defined(VDBE_PROFILE) || defined(SQLITE_DEBUG)
@@ -66176,7 +67333,7 @@ SQLITE_PRIVATE int sqlite3VdbeList(
   }else if( db->u1.isInterrupted ){
     p->rc = SQLITE_INTERRUPT;
     rc = SQLITE_ERROR;
-    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3ErrStr(p->rc));
+    sqlite3VdbeError(p, sqlite3ErrStr(p->rc));
   }else{
     char *zP4;
     Op *pOp;
@@ -67079,7 +68236,7 @@ SQLITE_PRIVATE int sqlite3VdbeCheckFk(Vdbe *p, int deferred){
   ){
     p->rc = SQLITE_CONSTRAINT_FOREIGNKEY;
     p->errorAction = OE_Abort;
-    sqlite3SetString(&p->zErrMsg, db, "FOREIGN KEY constraint failed");
+    sqlite3VdbeError(p, "FOREIGN KEY constraint failed");
     return SQLITE_ERROR;
   }
   return SQLITE_OK;
@@ -67700,6 +68857,13 @@ SQLITE_PRIVATE u32 sqlite3VdbeSerialType(Mem *pMem, int file_format){
   return ((n*2) + 12 + ((flags&MEM_Str)!=0));
 }
 
+/*
+** The sizes for serial types less than 12
+*/
+static const u8 sqlite3SmallTypeSizes[] = {
+  0, 1, 2, 3, 4, 6, 8, 8, 0, 0, 0, 0
+};
+
 /*
 ** Return the length of the data corresponding to the supplied serial-type.
 */
@@ -67707,8 +68871,7 @@ SQLITE_PRIVATE u32 sqlite3VdbeSerialTypeLen(u32 serial_type){
   if( serial_type>=12 ){
     return (serial_type-12)/2;
   }else{
-    static const u8 aSize[] = { 0, 1, 2, 3, 4, 6, 8, 8, 0, 0, 0, 0 };
-    return aSize[serial_type];
+    return sqlite3SmallTypeSizes[serial_type];
   }
 }
 
@@ -67792,7 +68955,7 @@ SQLITE_PRIVATE u32 sqlite3VdbeSerialPut(u8 *buf, Mem *pMem, u32 serial_type){
     }else{
       v = pMem->u.i;
     }
-    len = i = sqlite3VdbeSerialTypeLen(serial_type);
+    len = i = sqlite3SmallTypeSizes[serial_type];
     assert( i>0 );
     do{
       buf[--i] = (u8)(v&0xFF);
@@ -68077,6 +69240,7 @@ static int vdbeRecordCompareDebug(
   /*  mem1.u.i = 0;  // not needed, here to silence compiler warning */
   
   idx1 = getVarint32(aKey1, szHdr1);
+  if( szHdr1>98307 ) return SQLITE_CORRUPT;
   d1 = szHdr1;
   assert( pKeyInfo->nField+pKeyInfo->nXField>=pPKey2->nField || CORRUPT_DB );
   assert( pKeyInfo->aSortOrder!=0 );
@@ -68422,7 +69586,7 @@ SQLITE_PRIVATE int sqlite3VdbeRecordCompareWithSkip(
     if( pRhs->flags & MEM_Int ){
       serial_type = aKey1[idx1];
       testcase( serial_type==12 );
-      if( serial_type>=12 ){
+      if( serial_type>=10 ){
         rc = +1;
       }else if( serial_type==0 ){
         rc = -1;
@@ -68448,7 +69612,11 @@ SQLITE_PRIVATE int sqlite3VdbeRecordCompareWithSkip(
     /* RHS is real */
     else if( pRhs->flags & MEM_Real ){
       serial_type = aKey1[idx1];
-      if( serial_type>=12 ){
+      if( serial_type>=10 ){
+        /* Serial types 12 or greater are strings and blobs (greater than
+        ** numbers). Types 10 and 11 are currently "reserved for future 
+        ** use", so it doesn't really matter what the results of comparing
+        ** them to numberic values are.  */
         rc = +1;
       }else if( serial_type==0 ){
         rc = -1;
@@ -68817,7 +69985,7 @@ SQLITE_PRIVATE int sqlite3VdbeIdxRowid(sqlite3 *db, BtCursor *pCur, i64 *rowid){
   if( unlikely(typeRowid<1 || typeRowid>9 || typeRowid==7) ){
     goto idx_rowid_corruption;
   }
-  lenRowid = sqlite3VdbeSerialTypeLen(typeRowid);
+  lenRowid = sqlite3SmallTypeSizes[typeRowid];
   testcase( (u32)m.n==szHdr+lenRowid );
   if( unlikely((u32)m.n<szHdr+lenRowid) ){
     goto idx_rowid_corruption;
@@ -68990,6 +70158,8 @@ SQLITE_PRIVATE void sqlite3VtabImportErrmsg(Vdbe *p, sqlite3_vtab *pVtab){
 ** This file contains code use to implement APIs that are part of the
 ** VDBE.
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 #ifndef SQLITE_OMIT_DEPRECATED
 /*
@@ -69028,6 +70198,31 @@ static int vdbeSafetyNotNull(Vdbe *p){
   }
 }
 
+#ifndef SQLITE_OMIT_TRACE
+/*
+** Invoke the profile callback.  This routine is only called if we already
+** know that the profile callback is defined and needs to be invoked.
+*/
+static SQLITE_NOINLINE void invokeProfileCallback(sqlite3 *db, Vdbe *p){
+  sqlite3_int64 iNow;
+  assert( p->startTime>0 );
+  assert( db->xProfile!=0 );
+  assert( db->init.busy==0 );
+  assert( p->zSql!=0 );
+  sqlite3OsCurrentTimeInt64(db->pVfs, &iNow);
+  db->xProfile(db->pProfileArg, p->zSql, (iNow - p->startTime)*1000000);
+  p->startTime = 0;
+}
+/*
+** The checkProfileCallback(DB,P) macro checks to see if a profile callback
+** is needed, and it invokes the callback if it is needed.
+*/
+# define checkProfileCallback(DB,P) \
+   if( ((P)->startTime)>0 ){ invokeProfileCallback(DB,P); }
+#else
+# define checkProfileCallback(DB,P)  /*no-op*/
+#endif
+
 /*
 ** The following routine destroys a virtual machine that is created by
 ** the sqlite3_compile() routine. The integer returned is an SQLITE_
@@ -69048,6 +70243,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_finalize(sqlite3_stmt *pStmt){
     sqlite3 *db = v->db;
     if( vdbeSafety(v) ) return SQLITE_MISUSE_BKPT;
     sqlite3_mutex_enter(db->mutex);
+    checkProfileCallback(db, v);
     rc = sqlite3VdbeFinalize(v);
     rc = sqlite3ApiExit(db, rc);
     sqlite3LeaveMutexAndCloseZombie(db);
@@ -69069,12 +70265,14 @@ SQLITE_API int SQLITE_STDCALL sqlite3_reset(sqlite3_stmt *pStmt){
     rc = SQLITE_OK;
   }else{
     Vdbe *v = (Vdbe*)pStmt;
-    sqlite3_mutex_enter(v->db->mutex);
+    sqlite3 *db = v->db;
+    sqlite3_mutex_enter(db->mutex);
+    checkProfileCallback(db, v);
     rc = sqlite3VdbeReset(v);
     sqlite3VdbeRewind(v);
-    assert( (rc & (v->db->errMask))==rc );
-    rc = sqlite3ApiExit(v->db, rc);
-    sqlite3_mutex_leave(v->db->mutex);
+    assert( (rc & (db->errMask))==rc );
+    rc = sqlite3ApiExit(db, rc);
+    sqlite3_mutex_leave(db->mutex);
   }
   return rc;
 }
@@ -69109,7 +70307,10 @@ SQLITE_API int SQLITE_STDCALL sqlite3_clear_bindings(sqlite3_stmt *pStmt){
 SQLITE_API const void *SQLITE_STDCALL sqlite3_value_blob(sqlite3_value *pVal){
   Mem *p = (Mem*)pVal;
   if( p->flags & (MEM_Blob|MEM_Str) ){
-    sqlite3VdbeMemExpandBlob(p);
+    if( sqlite3VdbeMemExpandBlob(p)!=SQLITE_OK ){
+      assert( p->flags==MEM_Null && p->z==0 );
+      return 0;
+    }
     p->flags |= MEM_Blob;
     return p->n ? p->z : 0;
   }else{
@@ -69187,6 +70388,36 @@ SQLITE_API int SQLITE_STDCALL sqlite3_value_type(sqlite3_value* pVal){
   return aType[pVal->flags&MEM_AffMask];
 }
 
+/* Make a copy of an sqlite3_value object
+*/
+SQLITE_API sqlite3_value *SQLITE_STDCALL sqlite3_value_dup(const sqlite3_value *pOrig){
+  sqlite3_value *pNew;
+  if( pOrig==0 ) return 0;
+  pNew = sqlite3_malloc( sizeof(*pNew) );
+  if( pNew==0 ) return 0;
+  memset(pNew, 0, sizeof(*pNew));
+  memcpy(pNew, pOrig, MEMCELLSIZE);
+  pNew->flags &= ~MEM_Dyn;
+  pNew->db = 0;
+  if( pNew->flags&(MEM_Str|MEM_Blob) ){
+    pNew->flags &= ~(MEM_Static|MEM_Dyn);
+    pNew->flags |= MEM_Ephem;
+    if( sqlite3VdbeMemMakeWriteable(pNew)!=SQLITE_OK ){
+      sqlite3ValueFree(pNew);
+      pNew = 0;
+    }
+  }
+  return pNew;
+}
+
+/* Destroy an sqlite3_value object previously obtained from
+** sqlite3_value_dup().
+*/
+SQLITE_API void SQLITE_STDCALL sqlite3_value_free(sqlite3_value *pOld){
+  sqlite3ValueFree(pOld);
+}
+  
+
 /**************************** sqlite3_result_  *******************************
 ** The following routines are used by user-defined functions to specify
 ** the function result.
@@ -69341,6 +70572,15 @@ SQLITE_API void SQLITE_STDCALL sqlite3_result_zeroblob(sqlite3_context *pCtx, in
   assert( sqlite3_mutex_held(pCtx->pOut->db->mutex) );
   sqlite3VdbeMemSetZeroBlob(pCtx->pOut, n);
 }
+SQLITE_API int SQLITE_STDCALL sqlite3_result_zeroblob64(sqlite3_context *pCtx, u64 n){
+  Mem *pOut = pCtx->pOut;
+  assert( sqlite3_mutex_held(pOut->db->mutex) );
+  if( n>(u64)pOut->db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    return SQLITE_TOOBIG;
+  }
+  sqlite3VdbeMemSetZeroBlob(pCtx->pOut, (int)n);
+  return SQLITE_OK;
+}
 SQLITE_API void SQLITE_STDCALL sqlite3_result_error_code(sqlite3_context *pCtx, int errCode){
   pCtx->isError = errCode;
   pCtx->fErrorOrAux = 1;
@@ -69395,6 +70635,7 @@ static int doWalCallbacks(sqlite3 *db){
   return rc;
 }
 
+
 /*
 ** Execute the statement pStmt, either until a row of data is ready, the
 ** statement is completely executed or an error occurs.
@@ -69463,8 +70704,10 @@ static int sqlite3Step(Vdbe *p){
     );
 
 #ifndef SQLITE_OMIT_TRACE
-    if( db->xProfile && !db->init.busy ){
+    if( db->xProfile && !db->init.busy && p->zSql ){
       sqlite3OsCurrentTimeInt64(db->pVfs, &p->startTime);
+    }else{
+      assert( p->startTime==0 );
     }
 #endif
 
@@ -69488,13 +70731,8 @@ static int sqlite3Step(Vdbe *p){
   }
 
 #ifndef SQLITE_OMIT_TRACE
-  /* Invoke the profile callback if there is one
-  */
-  if( rc!=SQLITE_ROW && db->xProfile && !db->init.busy && p->zSql ){
-    sqlite3_int64 iNow;
-    sqlite3OsCurrentTimeInt64(db->pVfs, &iNow);
-    db->xProfile(db->pProfileArg, p->zSql, (iNow - p->startTime)*1000000);
-  }
+  /* If the statement completed successfully, invoke the profile callback */
+  if( rc!=SQLITE_ROW ) checkProfileCallback(db, p);
 #endif
 
   if( rc==SQLITE_DONE ){
@@ -70322,6 +71560,20 @@ SQLITE_API int SQLITE_STDCALL sqlite3_bind_zeroblob(sqlite3_stmt *pStmt, int i,
   }
   return rc;
 }
+SQLITE_API int SQLITE_STDCALL sqlite3_bind_zeroblob64(sqlite3_stmt *pStmt, int i, sqlite3_uint64 n){
+  int rc;
+  Vdbe *p = (Vdbe *)pStmt;
+  sqlite3_mutex_enter(p->db->mutex);
+  if( n>(u64)p->db->aLimit[SQLITE_LIMIT_LENGTH] ){
+    rc = SQLITE_TOOBIG;
+  }else{
+    assert( (n & 0x7FFFFFFF)==n );
+    rc = sqlite3_bind_zeroblob(pStmt, i, n);
+  }
+  rc = sqlite3ApiExit(p->db, rc);
+  sqlite3_mutex_leave(p->db->mutex);
+  return rc;
+}
 
 /*
 ** Return the number of wildcards that can be potentially bound to.
@@ -70571,6 +71823,8 @@ SQLITE_API void SQLITE_STDCALL sqlite3_stmt_scanstatus_reset(sqlite3_stmt *pStmt
 **
 ** The Vdbe parse-tree explainer is also found here.
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 #ifndef SQLITE_OMIT_TRACE
 
@@ -70763,6 +72017,8 @@ SQLITE_PRIVATE char *sqlite3VdbeExpandSql(
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 /*
 ** Invoke this macro on memory cells just prior to changing the
@@ -71013,7 +72269,7 @@ static void applyNumericAffinity(Mem *pRec, int bTryForInt){
 ** SQLITE_AFF_TEXT:
 **    Convert pRec to a text representation.
 **
-** SQLITE_AFF_NONE:
+** SQLITE_AFF_BLOB:
 **    No-op.  pRec is unchanged.
 */
 static void applyAffinity(
@@ -71039,6 +72295,7 @@ static void applyAffinity(
     if( 0==(pRec->flags&MEM_Str) && (pRec->flags&(MEM_Real|MEM_Int)) ){
       sqlite3VdbeMemStringify(pRec, enc, 1);
     }
+    pRec->flags &= ~(MEM_Real|MEM_Int);
   }
 }
 
@@ -71413,13 +72670,9 @@ SQLITE_PRIVATE int sqlite3VdbeExec(
   sqlite3VdbeIOTraceSql(p);
 #ifndef SQLITE_OMIT_PROGRESS_CALLBACK
   if( db->xProgress ){
+    u32 iPrior = p->aCounter[SQLITE_STMTSTATUS_VM_STEP];
     assert( 0 < db->nProgressOps );
-    nProgressLimit = (unsigned)p->aCounter[SQLITE_STMTSTATUS_VM_STEP];
-    if( nProgressLimit==0 ){
-      nProgressLimit = db->nProgressOps;
-    }else{
-      nProgressLimit %= (unsigned)db->nProgressOps;
-    }
+    nProgressLimit = db->nProgressOps - (iPrior % db->nProgressOps);
   }
 #endif
 #ifdef SQLITE_DEBUG
@@ -71799,12 +73052,11 @@ case OP_Halt: {
     assert( zType!=0 || pOp->p4.z!=0 );
     zLogFmt = "abort at %d in [%s]: %s";
     if( zType && pOp->p4.z ){
-      sqlite3SetString(&p->zErrMsg, db, "%s constraint failed: %s", 
-                       zType, pOp->p4.z);
+      sqlite3VdbeError(p, "%s constraint failed: %s", zType, pOp->p4.z);
     }else if( pOp->p4.z ){
-      sqlite3SetString(&p->zErrMsg, db, "%s", pOp->p4.z);
+      sqlite3VdbeError(p, "%s", pOp->p4.z);
     }else{
-      sqlite3SetString(&p->zErrMsg, db, "%s constraint failed", zType);
+      sqlite3VdbeError(p, "%s constraint failed", zType);
     }
     sqlite3_log(pOp->p1, zLogFmt, pcx, p->zSql, p->zErrMsg);
   }
@@ -72382,10 +73634,10 @@ case OP_CollSeq: {
   break;
 }
 
-/* Opcode: Function P1 P2 P3 P4 P5
+/* Opcode: Function0 P1 P2 P3 P4 P5
 ** Synopsis: r[P3]=func(r[P2@P5])
 **
-** Invoke a user function (P4 is a pointer to a Function structure that
+** Invoke a user function (P4 is a pointer to a FuncDef object that
 ** defines the function) with P5 arguments taken from register P2 and
 ** successors.  The result of the function is stored in register P3.
 ** Register P3 must not be one of the function inputs.
@@ -72397,59 +73649,100 @@ case OP_CollSeq: {
 ** sqlite3_set_auxdata() API may be safely retained until the next
 ** invocation of this opcode.
 **
-** See also: AggStep and AggFinal
+** See also: Function, AggStep, AggFinal
 */
-case OP_Function: {
-  int i;
-  Mem *pArg;
-  sqlite3_context ctx;
-  sqlite3_value **apVal;
+/* Opcode: Function P1 P2 P3 P4 P5
+** Synopsis: r[P3]=func(r[P2@P5])
+**
+** Invoke a user function (P4 is a pointer to an sqlite3_context object that
+** contains a pointer to the function to be run) with P5 arguments taken
+** from register P2 and successors.  The result of the function is stored
+** in register P3.  Register P3 must not be one of the function inputs.
+**
+** P1 is a 32-bit bitmask indicating whether or not each argument to the 
+** function was determined to be constant at compile time. If the first
+** argument was constant then bit 0 of P1 is set. This is used to determine
+** whether meta data associated with a user function argument using the
+** sqlite3_set_auxdata() API may be safely retained until the next
+** invocation of this opcode.
+**
+** SQL functions are initially coded as OP_Function0 with P4 pointing
+** to a FuncDef object.  But on first evaluation, the P4 operand is
+** automatically converted into an sqlite3_context object and the operation
+** changed to this OP_Function opcode.  In this way, the initialization of
+** the sqlite3_context object occurs only once, rather than once for each
+** evaluation of the function.
+**
+** See also: Function0, AggStep, AggFinal
+*/
+case OP_Function0: {
   int n;
+  sqlite3_context *pCtx;
 
+  assert( pOp->p4type==P4_FUNCDEF );
   n = pOp->p5;
-  apVal = p->apArg;
-  assert( apVal || n==0 );
   assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
-  ctx.pOut = &aMem[pOp->p3];
-  memAboutToChange(p, ctx.pOut);
-
   assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem-p->nCursor)+1) );
   assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
-  pArg = &aMem[pOp->p2];
-  for(i=0; i<n; i++, pArg++){
-    assert( memIsValid(pArg) );
-    apVal[i] = pArg;
-    Deephemeralize(pArg);
-    REGISTER_TRACE(pOp->p2+i, pArg);
+  pCtx = sqlite3DbMallocRaw(db, sizeof(*pCtx) + (n-1)*sizeof(sqlite3_value*));
+  if( pCtx==0 ) goto no_mem;
+  pCtx->pOut = 0;
+  pCtx->pFunc = pOp->p4.pFunc;
+  pCtx->iOp = (int)(pOp - aOp);
+  pCtx->pVdbe = p;
+  pCtx->argc = n;
+  pOp->p4type = P4_FUNCCTX;
+  pOp->p4.pCtx = pCtx;
+  pOp->opcode = OP_Function;
+  /* Fall through into OP_Function */
+}
+case OP_Function: {
+  int i;
+  sqlite3_context *pCtx;
+
+  assert( pOp->p4type==P4_FUNCCTX );
+  pCtx = pOp->p4.pCtx;
+
+  /* If this function is inside of a trigger, the register array in aMem[]
+  ** might change from one evaluation to the next.  The next block of code
+  ** checks to see if the register array has changed, and if so it
+  ** reinitializes the relavant parts of the sqlite3_context object */
+  pOut = &aMem[pOp->p3];
+  if( pCtx->pOut != pOut ){
+    pCtx->pOut = pOut;
+    for(i=pCtx->argc-1; i>=0; i--) pCtx->argv[i] = &aMem[pOp->p2+i];
   }
 
-  assert( pOp->p4type==P4_FUNCDEF );
-  ctx.pFunc = pOp->p4.pFunc;
-  ctx.iOp = (int)(pOp - aOp);
-  ctx.pVdbe = p;
-  MemSetTypeFlag(ctx.pOut, MEM_Null);
-  ctx.fErrorOrAux = 0;
+  memAboutToChange(p, pCtx->pOut);
+#ifdef SQLITE_DEBUG
+  for(i=0; i<pCtx->argc; i++){
+    assert( memIsValid(pCtx->argv[i]) );
+    REGISTER_TRACE(pOp->p2+i, pCtx->argv[i]);
+  }
+#endif
+  MemSetTypeFlag(pCtx->pOut, MEM_Null);
+  pCtx->fErrorOrAux = 0;
   db->lastRowid = lastRowid;
-  (*ctx.pFunc->xFunc)(&ctx, n, apVal); /* IMP: R-24505-23230 */
+  (*pCtx->pFunc->xFunc)(pCtx, pCtx->argc, pCtx->argv); /* IMP: R-24505-23230 */
   lastRowid = db->lastRowid;  /* Remember rowid changes made by xFunc */
 
   /* If the function returned an error, throw an exception */
-  if( ctx.fErrorOrAux ){
-    if( ctx.isError ){
-      sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(ctx.pOut));
-      rc = ctx.isError;
+  if( pCtx->fErrorOrAux ){
+    if( pCtx->isError ){
+      sqlite3VdbeError(p, "%s", sqlite3_value_text(pCtx->pOut));
+      rc = pCtx->isError;
     }
-    sqlite3VdbeDeleteAuxData(p, (int)(pOp - aOp), pOp->p1);
+    sqlite3VdbeDeleteAuxData(p, pCtx->iOp, pOp->p1);
   }
 
   /* Copy the result of the function into register P3 */
-  sqlite3VdbeChangeEncoding(ctx.pOut, encoding);
-  if( sqlite3VdbeMemTooBig(ctx.pOut) ){
-    goto too_big;
+  if( pOut->flags & (MEM_Str|MEM_Blob) ){
+    sqlite3VdbeChangeEncoding(pCtx->pOut, encoding);
+    if( sqlite3VdbeMemTooBig(pCtx->pOut) ) goto too_big;
   }
 
-  REGISTER_TRACE(pOp->p3, ctx.pOut);
-  UPDATE_MAX_BLOBSIZE(ctx.pOut);
+  REGISTER_TRACE(pOp->p3, pCtx->pOut);
+  UPDATE_MAX_BLOBSIZE(pCtx->pOut);
   break;
 }
 
@@ -72612,9 +73905,9 @@ case OP_RealAffinity: {                  /* in1 */
 ** A NULL value is not changed by this routine.  It remains NULL.
 */
 case OP_Cast: {                  /* in1 */
-  assert( pOp->p2>=SQLITE_AFF_NONE && pOp->p2<=SQLITE_AFF_REAL );
+  assert( pOp->p2>=SQLITE_AFF_BLOB && pOp->p2<=SQLITE_AFF_REAL );
   testcase( pOp->p2==SQLITE_AFF_TEXT );
-  testcase( pOp->p2==SQLITE_AFF_NONE );
+  testcase( pOp->p2==SQLITE_AFF_BLOB );
   testcase( pOp->p2==SQLITE_AFF_NUMERIC );
   testcase( pOp->p2==SQLITE_AFF_INTEGER );
   testcase( pOp->p2==SQLITE_AFF_REAL );
@@ -73425,7 +74718,7 @@ case OP_Affinity: {
 ** The mapping from character to affinity is given by the SQLITE_AFF_
 ** macros defined in sqliteInt.h.
 **
-** If P4 is NULL then all index fields have the affinity NONE.
+** If P4 is NULL then all index fields have the affinity BLOB.
 */
 case OP_MakeRecord: {
   u8 *zNewRecord;        /* A buffer to hold the data for the new record */
@@ -73497,7 +74790,7 @@ case OP_MakeRecord: {
     len = sqlite3VdbeSerialTypeLen(serial_type);
     if( pRec->flags & MEM_Zero ){
       if( nData ){
-        sqlite3VdbeMemExpandBlob(pRec);
+        if( sqlite3VdbeMemExpandBlob(pRec) ) goto no_mem;
       }else{
         nZero += pRec->u.nZero;
         len -= pRec->u.nZero;
@@ -73623,8 +74916,7 @@ case OP_Savepoint: {
       /* A new savepoint cannot be created if there are active write 
       ** statements (i.e. open read/write incremental blob handles).
       */
-      sqlite3SetString(&p->zErrMsg, db, "cannot open savepoint - "
-        "SQL statements in progress");
+      sqlite3VdbeError(p, "cannot open savepoint - SQL statements in progress");
       rc = SQLITE_BUSY;
     }else{
       nName = sqlite3Strlen30(zName);
@@ -73675,15 +74967,14 @@ case OP_Savepoint: {
       iSavepoint++;
     }
     if( !pSavepoint ){
-      sqlite3SetString(&p->zErrMsg, db, "no such savepoint: %s", zName);
+      sqlite3VdbeError(p, "no such savepoint: %s", zName);
       rc = SQLITE_ERROR;
     }else if( db->nVdbeWrite>0 && p1==SAVEPOINT_RELEASE ){
       /* It is not possible to release (commit) a savepoint if there are 
       ** active write statements.
       */
-      sqlite3SetString(&p->zErrMsg, db, 
-        "cannot release savepoint - SQL statements in progress"
-      );
+      sqlite3VdbeError(p, "cannot release savepoint - "
+                          "SQL statements in progress");
       rc = SQLITE_BUSY;
     }else{
 
@@ -73789,23 +75080,12 @@ case OP_AutoCommit: {
   assert( db->nVdbeActive>0 );  /* At least this one VM is active */
   assert( p->bIsReader );
 
-#if 0
-  if( turnOnAC && iRollback && db->nVdbeActive>1 ){
-    /* If this instruction implements a ROLLBACK and other VMs are
-    ** still running, and a transaction is active, return an error indicating
-    ** that the other VMs must complete first. 
-    */
-    sqlite3SetString(&p->zErrMsg, db, "cannot rollback transaction - "
-        "SQL statements in progress");
-    rc = SQLITE_BUSY;
-  }else
-#endif
   if( turnOnAC && !iRollback && db->nVdbeWrite>0 ){
     /* If this instruction implements a COMMIT and other VMs are writing
     ** return an error indicating that the other VMs must complete first. 
     */
-    sqlite3SetString(&p->zErrMsg, db, "cannot commit transaction - "
-        "SQL statements in progress");
+    sqlite3VdbeError(p, "cannot commit transaction - "
+                        "SQL statements in progress");
     rc = SQLITE_BUSY;
   }else if( desiredAutoCommit!=db->autoCommit ){
     if( iRollback ){
@@ -73832,7 +75112,7 @@ case OP_AutoCommit: {
     }
     goto vdbe_return;
   }else{
-    sqlite3SetString(&p->zErrMsg, db,
+    sqlite3VdbeError(p,
         (!desiredAutoCommit)?"cannot start a transaction within a transaction":(
         (iRollback)?"cannot rollback - no transaction is active":
                    "cannot commit - no transaction is active"));
@@ -74356,6 +75636,26 @@ case OP_Close: {
   break;
 }
 
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+/* Opcode: ColumnsUsed P1 * * P4 *
+**
+** This opcode (which only exists if SQLite was compiled with
+** SQLITE_ENABLE_COLUMN_USED_MASK) identifies which columns of the
+** table or index for cursor P1 are used.  P4 is a 64-bit integer
+** (P4_INT64) in which the first 63 bits are one for each of the
+** first 63 columns of the table or index that are actually used
+** by the cursor.  The high-order bit is set if any column after
+** the 64th is used.
+*/
+case OP_ColumnsUsed: {
+  VdbeCursor *pC;
+  pC = p->apCsr[pOp->p1];
+  assert( pC->pCursor );
+  pC->maskUsed = *(u64*)pOp->p4.pI64;
+  break;
+}
+#endif
+
 /* Opcode: SeekGE P1 P2 P3 P4 *
 ** Synopsis: key=r[P3@P4]
 **
@@ -74844,9 +76144,8 @@ case OP_NewRowid: {           /* out2 */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  if( NEVER(pC->pCursor==0) ){
-    /* The zero initialization above is all that is needed */
-  }else{
+  assert( pC->pCursor!=0 );
+  {
     /* The next rowid or record number (different terms for the same
     ** thing) is obtained in a two-step algorithm.
     **
@@ -75585,7 +76884,6 @@ next_tail:
 case OP_SorterInsert:       /* in2 */
 case OP_IdxInsert: {        /* in2 */
   VdbeCursor *pC;
-  BtCursor *pCrsr;
   int nKey;
   const char *zKey;
 
@@ -75595,18 +76893,17 @@ case OP_IdxInsert: {        /* in2 */
   assert( isSorter(pC)==(pOp->opcode==OP_SorterInsert) );
   pIn2 = &aMem[pOp->p2];
   assert( pIn2->flags & MEM_Blob );
-  pCrsr = pC->pCursor;
   if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
-  assert( pCrsr!=0 );
+  assert( pC->pCursor!=0 );
   assert( pC->isTable==0 );
   rc = ExpandBlob(pIn2);
   if( rc==SQLITE_OK ){
-    if( isSorter(pC) ){
+    if( pOp->opcode==OP_SorterInsert ){
       rc = sqlite3VdbeSorterWrite(pC, pIn2);
     }else{
       nKey = pIn2->n;
       zKey = pIn2->z;
-      rc = sqlite3BtreeInsert(pCrsr, zKey, nKey, "", 0, 0, pOp->p3, 
+      rc = sqlite3BtreeInsert(pC->pCursor, zKey, nKey, "", 0, 0, pOp->p3, 
           ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0)
           );
       assert( pC->deferredMoveto==0 );
@@ -76265,7 +77562,7 @@ case OP_Program: {        /* jump */
 
   if( p->nFrame>=db->aLimit[SQLITE_LIMIT_TRIGGER_DEPTH] ){
     rc = SQLITE_ERROR;
-    sqlite3SetString(&p->zErrMsg, db, "too many levels of trigger recursion");
+    sqlite3VdbeError(p, "too many levels of trigger recursion");
     break;
   }
 
@@ -76526,57 +77823,101 @@ case OP_JumpZeroIncr: {        /* jump, in1 */
   break;
 }
 
-/* Opcode: AggStep * P2 P3 P4 P5
+/* Opcode: AggStep0 * P2 P3 P4 P5
 ** Synopsis: accum=r[P3] step(r[P2@P5])
 **
 ** Execute the step function for an aggregate.  The
 ** function has P5 arguments.   P4 is a pointer to the FuncDef
-** structure that specifies the function.  Use register
-** P3 as the accumulator.
+** structure that specifies the function.  Register P3 is the
+** accumulator.
 **
 ** The P5 arguments are taken from register P2 and its
 ** successors.
 */
-case OP_AggStep: {
+/* Opcode: AggStep * P2 P3 P4 P5
+** Synopsis: accum=r[P3] step(r[P2@P5])
+**
+** Execute the step function for an aggregate.  The
+** function has P5 arguments.   P4 is a pointer to an sqlite3_context
+** object that is used to run the function.  Register P3 is
+** as the accumulator.
+**
+** The P5 arguments are taken from register P2 and its
+** successors.
+**
+** This opcode is initially coded as OP_AggStep0.  On first evaluation,
+** the FuncDef stored in P4 is converted into an sqlite3_context and
+** the opcode is changed.  In this way, the initialization of the
+** sqlite3_context only happens once, instead of on each call to the
+** step function.
+*/
+case OP_AggStep0: {
   int n;
+  sqlite3_context *pCtx;
+
+  assert( pOp->p4type==P4_FUNCDEF );
+  n = pOp->p5;
+  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
+  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem-p->nCursor)+1) );
+  assert( pOp->p3<pOp->p2 || pOp->p3>=pOp->p2+n );
+  pCtx = sqlite3DbMallocRaw(db, sizeof(*pCtx) + (n-1)*sizeof(sqlite3_value*));
+  if( pCtx==0 ) goto no_mem;
+  pCtx->pMem = 0;
+  pCtx->pFunc = pOp->p4.pFunc;
+  pCtx->iOp = (int)(pOp - aOp);
+  pCtx->pVdbe = p;
+  pCtx->argc = n;
+  pOp->p4type = P4_FUNCCTX;
+  pOp->p4.pCtx = pCtx;
+  pOp->opcode = OP_AggStep;
+  /* Fall through into OP_AggStep */
+}
+case OP_AggStep: {
   int i;
+  sqlite3_context *pCtx;
   Mem *pMem;
-  Mem *pRec;
   Mem t;
-  sqlite3_context ctx;
-  sqlite3_value **apVal;
 
-  n = pOp->p5;
-  assert( n>=0 );
-  pRec = &aMem[pOp->p2];
-  apVal = p->apArg;
-  assert( apVal || n==0 );
-  for(i=0; i<n; i++, pRec++){
-    assert( memIsValid(pRec) );
-    apVal[i] = pRec;
-    memAboutToChange(p, pRec);
+  assert( pOp->p4type==P4_FUNCCTX );
+  pCtx = pOp->p4.pCtx;
+  pMem = &aMem[pOp->p3];
+
+  /* If this function is inside of a trigger, the register array in aMem[]
+  ** might change from one evaluation to the next.  The next block of code
+  ** checks to see if the register array has changed, and if so it
+  ** reinitializes the relavant parts of the sqlite3_context object */
+  if( pCtx->pMem != pMem ){
+    pCtx->pMem = pMem;
+    for(i=pCtx->argc-1; i>=0; i--) pCtx->argv[i] = &aMem[pOp->p2+i];
   }
-  ctx.pFunc = pOp->p4.pFunc;
-  assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
-  ctx.pMem = pMem = &aMem[pOp->p3];
+
+#ifdef SQLITE_DEBUG
+  for(i=0; i<pCtx->argc; i++){
+    assert( memIsValid(pCtx->argv[i]) );
+    REGISTER_TRACE(pOp->p2+i, pCtx->argv[i]);
+  }
+#endif
+
   pMem->n++;
   sqlite3VdbeMemInit(&t, db, MEM_Null);
-  ctx.pOut = &t;
-  ctx.isError = 0;
-  ctx.pVdbe = p;
-  ctx.iOp = (int)(pOp - aOp);
-  ctx.skipFlag = 0;
-  (ctx.pFunc->xStep)(&ctx, n, apVal); /* IMP: R-24505-23230 */
-  if( ctx.isError ){
-    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(&t));
-    rc = ctx.isError;
+  pCtx->pOut = &t;
+  pCtx->fErrorOrAux = 0;
+  pCtx->skipFlag = 0;
+  (pCtx->pFunc->xStep)(pCtx,pCtx->argc,pCtx->argv); /* IMP: R-24505-23230 */
+  if( pCtx->fErrorOrAux ){
+    if( pCtx->isError ){
+      sqlite3VdbeError(p, "%s", sqlite3_value_text(&t));
+      rc = pCtx->isError;
+    }
+    sqlite3VdbeMemRelease(&t);
+  }else{
+    assert( t.flags==MEM_Null );
   }
-  if( ctx.skipFlag ){
+  if( pCtx->skipFlag ){
     assert( pOp[-1].opcode==OP_CollSeq );
     i = pOp[-1].p1;
     if( i ) sqlite3VdbeMemSetInt64(&aMem[i], 1);
   }
-  sqlite3VdbeMemRelease(&t);
   break;
 }
 
@@ -76600,7 +77941,7 @@ case OP_AggFinal: {
   assert( (pMem->flags & ~(MEM_Null|MEM_Agg))==0 );
   rc = sqlite3VdbeMemFinalize(pMem, pOp->p4.pFunc);
   if( rc ){
-    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3_value_text(pMem));
+    sqlite3VdbeError(p, "%s", sqlite3_value_text(pMem));
   }
   sqlite3VdbeChangeEncoding(pMem, encoding);
   UPDATE_MAX_BLOBSIZE(pMem);
@@ -76705,7 +78046,7 @@ case OP_JournalMode: {    /* out2 */
   ){
     if( !db->autoCommit || db->nVdbeRead>1 ){
       rc = SQLITE_ERROR;
-      sqlite3SetString(&p->zErrMsg, db, 
+      sqlite3VdbeError(p,
           "cannot change %s wal mode from within a transaction",
           (eNew==PAGER_JOURNALMODE_WAL ? "into" : "out of")
       );
@@ -76836,7 +78177,7 @@ case OP_TableLock: {
     rc = sqlite3BtreeLockTable(db->aDb[p1].pBt, pOp->p2, isWriteLock);
     if( (rc&0xFF)==SQLITE_LOCKED ){
       const char *z = pOp->p4.z;
-      sqlite3SetString(&p->zErrMsg, db, "database table is locked: %s", z);
+      sqlite3VdbeError(p, "database table is locked: %s", z);
     }
   }
   break;
@@ -77384,7 +78725,7 @@ vdbe_return:
   ** is encountered.
   */
 too_big:
-  sqlite3SetString(&p->zErrMsg, db, "string or blob too big");
+  sqlite3VdbeError(p, "string or blob too big");
   rc = SQLITE_TOOBIG;
   goto vdbe_error_halt;
 
@@ -77392,7 +78733,7 @@ too_big:
   */
 no_mem:
   db->mallocFailed = 1;
-  sqlite3SetString(&p->zErrMsg, db, "out of memory");
+  sqlite3VdbeError(p, "out of memory");
   rc = SQLITE_NOMEM;
   goto vdbe_error_halt;
 
@@ -77403,7 +78744,7 @@ abort_due_to_error:
   assert( p->zErrMsg==0 );
   if( db->mallocFailed ) rc = SQLITE_NOMEM;
   if( rc!=SQLITE_IOERR_NOMEM ){
-    sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3ErrStr(rc));
+    sqlite3VdbeError(p, "%s", sqlite3ErrStr(rc));
   }
   goto vdbe_error_halt;
 
@@ -77414,7 +78755,7 @@ abort_due_to_interrupt:
   assert( db->u1.isInterrupted );
   rc = SQLITE_INTERRUPT;
   p->rc = rc;
-  sqlite3SetString(&p->zErrMsg, db, "%s", sqlite3ErrStr(rc));
+  sqlite3VdbeError(p, "%s", sqlite3ErrStr(rc));
   goto vdbe_error_halt;
 }
 
@@ -77436,6 +78777,8 @@ abort_due_to_interrupt:
 ** This file contains code used to implement incremental BLOB I/O.
 */
 
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 #ifndef SQLITE_OMIT_INCRBLOB
 
@@ -78034,6 +79377,8 @@ SQLITE_API int SQLITE_STDCALL sqlite3_blob_reopen(sqlite3_blob *pBlob, sqlite3_i
 ** thread to merge the output of each of the others to a single PMA for
 ** the main thread to read from.
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 /* 
 ** If SQLITE_DEBUG_SORTER_THREADS is defined, this module outputs various
@@ -80650,6 +81995,7 @@ SQLITE_PRIVATE int sqlite3VdbeSorterCompare(
 **   2) The sqlite3JournalCreate() function is called.
 */
 #ifdef SQLITE_ENABLE_ATOMIC_WRITE
+/* #include "sqliteInt.h" */
 
 
 /*
@@ -80897,6 +82243,7 @@ SQLITE_PRIVATE int sqlite3JournalSize(sqlite3_vfs *pVfs){
 ** The in-memory rollback journal is used to journal transactions for
 ** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
 */
+/* #include "sqliteInt.h" */
 
 /* Forward references to internal structures */
 typedef struct MemJournal MemJournal;
@@ -81152,6 +82499,7 @@ SQLITE_PRIVATE int sqlite3MemJournalSize(void){
 ** This file contains routines used for walking the parser tree for
 ** an SQL statement.
 */
+/* #include "sqliteInt.h" */
 /* #include <stdlib.h> */
 /* #include <string.h> */
 
@@ -81310,6 +82658,7 @@ SQLITE_PRIVATE int sqlite3WalkSelect(Walker *pWalker, Select *p){
 ** resolve all identifiers by associating them with a particular
 ** table and column.
 */
+/* #include "sqliteInt.h" */
 /* #include <stdlib.h> */
 /* #include <string.h> */
 
@@ -81653,7 +83002,7 @@ static int lookupName(
             break;
           }
         }
-        if( iCol>=pTab->nCol && sqlite3IsRowid(zCol) && HasRowid(pTab) ){
+        if( iCol>=pTab->nCol && sqlite3IsRowid(zCol) && VisibleRowid(pTab) ){
           /* IMP: R-51414-32910 */
           /* IMP: R-44911-55124 */
           iCol = -1;
@@ -81683,7 +83032,7 @@ static int lookupName(
     ** Perhaps the name is a reference to the ROWID
     */
     if( cnt==0 && cntTab==1 && pMatch && sqlite3IsRowid(zCol)
-     && HasRowid(pMatch->pTab) ){
+     && VisibleRowid(pMatch->pTab) ){
       cnt = 1;
       pExpr->iColumn = -1;     /* IMP: R-44911-55124 */
       pExpr->affinity = SQLITE_AFF_INTEGER;
@@ -82626,6 +83975,13 @@ static int resolveSelectStep(Walker *pWalker, Select *p){
       }
     }
 
+    /* If this is part of a compound SELECT, check that it has the right
+    ** number of expressions in the select list. */
+    if( p->pNext && p->pEList->nExpr!=p->pNext->pEList->nExpr ){
+      sqlite3SelectWrongNumTermsError(pParse, p->pNext);
+      return WRC_Abort;
+    }
+
     /* Advance to the next term of the compound
     */
     p = p->pPrior;
@@ -82815,6 +84171,7 @@ SQLITE_PRIVATE void sqlite3ResolveSelfReference(
 ** This file contains routines used for analyzing expressions and
 ** for generating VDBE code that evaluates expressions in SQLite.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** Return the 'affinity' of the expression pExpr if any.
@@ -82993,13 +84350,13 @@ SQLITE_PRIVATE char sqlite3CompareAffinity(Expr *pExpr, char aff2){
     if( sqlite3IsNumericAffinity(aff1) || sqlite3IsNumericAffinity(aff2) ){
       return SQLITE_AFF_NUMERIC;
     }else{
-      return SQLITE_AFF_NONE;
+      return SQLITE_AFF_BLOB;
     }
   }else if( !aff1 && !aff2 ){
     /* Neither side of the comparison is a column.  Compare the
     ** results directly.
     */
-    return SQLITE_AFF_NONE;
+    return SQLITE_AFF_BLOB;
   }else{
     /* One side is a column, the other is not. Use the columns affinity. */
     assert( aff1==0 || aff2==0 );
@@ -83023,7 +84380,7 @@ static char comparisonAffinity(Expr *pExpr){
   }else if( ExprHasProperty(pExpr, EP_xIsSelect) ){
     aff = sqlite3CompareAffinity(pExpr->x.pSelect->pEList->a[0].pExpr, aff);
   }else if( !aff ){
-    aff = SQLITE_AFF_NONE;
+    aff = SQLITE_AFF_BLOB;
   }
   return aff;
 }
@@ -83037,7 +84394,7 @@ static char comparisonAffinity(Expr *pExpr){
 SQLITE_PRIVATE int sqlite3IndexAffinityOk(Expr *pExpr, char idx_affinity){
   char aff = comparisonAffinity(pExpr);
   switch( aff ){
-    case SQLITE_AFF_NONE:
+    case SQLITE_AFF_BLOB:
       return 1;
     case SQLITE_AFF_TEXT:
       return idx_affinity==SQLITE_AFF_TEXT;
@@ -83843,7 +85200,7 @@ SQLITE_PRIVATE SrcList *sqlite3SrcListDup(sqlite3 *db, SrcList *p, int flags){
     pNewItem->isCorrelated = pOldItem->isCorrelated;
     pNewItem->viaCoroutine = pOldItem->viaCoroutine;
     pNewItem->isRecursive = pOldItem->isRecursive;
-    pNewItem->zIndex = sqlite3DbStrDup(db, pOldItem->zIndex);
+    pNewItem->zIndexedBy = sqlite3DbStrDup(db, pOldItem->zIndexedBy);
     pNewItem->notIndexed = pOldItem->notIndexed;
     pNewItem->pIndex = pOldItem->pIndex;
     pTab = pNewItem->pTab = pOldItem->pTab;
@@ -84070,7 +85427,7 @@ SQLITE_PRIVATE u32 sqlite3ExprListFlags(const ExprList *pList){
 **
 **     sqlite3ExprIsConstant()                  pWalker->eCode==1
 **     sqlite3ExprIsConstantNotJoin()           pWalker->eCode==2
-**     sqlite3ExprRefOneTableOnly()             pWalker->eCode==3
+**     sqlite3ExprIsTableConstant()             pWalker->eCode==3
 **     sqlite3ExprIsConstantOrFunction()        pWalker->eCode==4 or 5
 **
 ** In all cases, the callbacks set Walker.eCode=0 and abort if the expression
@@ -84178,7 +85535,7 @@ SQLITE_PRIVATE int sqlite3ExprIsConstantNotJoin(Expr *p){
 }
 
 /*
-** Walk an expression tree.  Return non-zero if the expression constant
+** Walk an expression tree.  Return non-zero if the expression is constant
 ** for any single row of the table with cursor iCur.  In other words, the
 ** expression must not refer to any non-deterministic function nor any
 ** table other than iCur.
@@ -84284,7 +85641,7 @@ SQLITE_PRIVATE int sqlite3ExprCanBeNull(const Expr *p){
 */
 SQLITE_PRIVATE int sqlite3ExprNeedsNoAffinityChange(const Expr *p, char aff){
   u8 op;
-  if( aff==SQLITE_AFF_NONE ) return 1;
+  if( aff==SQLITE_AFF_BLOB ) return 1;
   while( p->op==TK_UPLUS || p->op==TK_UMINUS ){ p = p->pLeft; }
   op = p->op;
   if( op==TK_REGISTER ) op = p->op2;
@@ -84735,7 +86092,7 @@ SQLITE_PRIVATE int sqlite3CodeSubselect(
         int r1, r2, r3;
 
         if( !affinity ){
-          affinity = SQLITE_AFF_NONE;
+          affinity = SQLITE_AFF_BLOB;
         }
         if( pKeyInfo ){
           assert( sqlite3KeyInfoIsWriteable(pKeyInfo) );
@@ -85010,17 +86367,6 @@ static void sqlite3ExprCodeIN(
 }
 #endif /* SQLITE_OMIT_SUBQUERY */
 
-/*
-** Duplicate an 8-byte value
-*/
-static char *dup8bytes(Vdbe *v, const char *in){
-  char *out = sqlite3DbMallocRaw(sqlite3VdbeDb(v), 8);
-  if( out ){
-    memcpy(out, in, 8);
-  }
-  return out;
-}
-
 #ifndef SQLITE_OMIT_FLOATING_POINT
 /*
 ** Generate an instruction that will put the floating point
@@ -85033,12 +86379,10 @@ static char *dup8bytes(Vdbe *v, const char *in){
 static void codeReal(Vdbe *v, const char *z, int negateFlag, int iMem){
   if( ALWAYS(z!=0) ){
     double value;
-    char *zV;
     sqlite3AtoF(z, &value, sqlite3Strlen30(z), SQLITE_UTF8);
     assert( !sqlite3IsNaN(value) ); /* The new AtoF never returns NaN */
     if( negateFlag ) value = -value;
-    zV = dup8bytes(v, (char*)&value);
-    sqlite3VdbeAddOp4(v, OP_Real, 0, iMem, 0, zV, P4_REAL);
+    sqlite3VdbeAddOp4Dup8(v, OP_Real, 0, iMem, 0, (u8*)&value, P4_REAL);
   }
 }
 #endif
@@ -85064,10 +86408,8 @@ static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
     assert( z!=0 );
     c = sqlite3DecOrHexToI64(z, &value);
     if( c==0 || (c==2 && negFlag) ){
-      char *zV;
       if( negFlag ){ value = c==2 ? SMALLEST_INT64 : -value; }
-      zV = dup8bytes(v, (char*)&value);
-      sqlite3VdbeAddOp4(v, OP_Int64, 0, iMem, 0, zV, P4_INT64);
+      sqlite3VdbeAddOp4Dup8(v, OP_Int64, 0, iMem, 0, (u8*)&value, P4_INT64);
     }else{
 #ifdef SQLITE_OMIT_FLOATING_POINT
       sqlite3ErrorMsg(pParse, "oversized integer: %s%s", negFlag ? "-" : "", z);
@@ -85672,7 +87014,7 @@ SQLITE_PRIVATE int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target)
       */
       if( pDef->funcFlags & SQLITE_FUNC_UNLIKELY ){
         assert( nFarg>=1 );
-        sqlite3ExprCode(pParse, pFarg->a[0].pExpr, target);
+        inReg = sqlite3ExprCodeTarget(pParse, pFarg->a[0].pExpr, target);
         break;
       }
 
@@ -85742,7 +87084,7 @@ SQLITE_PRIVATE int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target)
         if( !pColl ) pColl = db->pDfltColl; 
         sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
       }
-      sqlite3VdbeAddOp4(v, OP_Function, constMask, r1, target,
+      sqlite3VdbeAddOp4(v, OP_Function0, constMask, r1, target,
                         (char*)pDef, P4_FUNCDEF);
       sqlite3VdbeChangeP5(v, (u8)nFarg);
       if( nFarg && constMask==0 ){
@@ -86113,268 +87455,6 @@ SQLITE_PRIVATE void sqlite3ExprCodeAndCache(Parse *pParse, Expr *pExpr, int targ
   exprToRegister(pExpr, iMem);
 }
 
-#ifdef SQLITE_DEBUG
-/*
-** Generate a human-readable explanation of an expression tree.
-*/
-SQLITE_PRIVATE void sqlite3TreeViewExpr(TreeView *pView, const Expr *pExpr, u8 moreToFollow){
-  const char *zBinOp = 0;   /* Binary operator */
-  const char *zUniOp = 0;   /* Unary operator */
-  pView = sqlite3TreeViewPush(pView, moreToFollow);
-  if( pExpr==0 ){
-    sqlite3TreeViewLine(pView, "nil");
-    sqlite3TreeViewPop(pView);
-    return;
-  }
-  switch( pExpr->op ){
-    case TK_AGG_COLUMN: {
-      sqlite3TreeViewLine(pView, "AGG{%d:%d}",
-            pExpr->iTable, pExpr->iColumn);
-      break;
-    }
-    case TK_COLUMN: {
-      if( pExpr->iTable<0 ){
-        /* This only happens when coding check constraints */
-        sqlite3TreeViewLine(pView, "COLUMN(%d)", pExpr->iColumn);
-      }else{
-        sqlite3TreeViewLine(pView, "{%d:%d}",
-                             pExpr->iTable, pExpr->iColumn);
-      }
-      break;
-    }
-    case TK_INTEGER: {
-      if( pExpr->flags & EP_IntValue ){
-        sqlite3TreeViewLine(pView, "%d", pExpr->u.iValue);
-      }else{
-        sqlite3TreeViewLine(pView, "%s", pExpr->u.zToken);
-      }
-      break;
-    }
-#ifndef SQLITE_OMIT_FLOATING_POINT
-    case TK_FLOAT: {
-      sqlite3TreeViewLine(pView,"%s", pExpr->u.zToken);
-      break;
-    }
-#endif
-    case TK_STRING: {
-      sqlite3TreeViewLine(pView,"%Q", pExpr->u.zToken);
-      break;
-    }
-    case TK_NULL: {
-      sqlite3TreeViewLine(pView,"NULL");
-      break;
-    }
-#ifndef SQLITE_OMIT_BLOB_LITERAL
-    case TK_BLOB: {
-      sqlite3TreeViewLine(pView,"%s", pExpr->u.zToken);
-      break;
-    }
-#endif
-    case TK_VARIABLE: {
-      sqlite3TreeViewLine(pView,"VARIABLE(%s,%d)",
-                          pExpr->u.zToken, pExpr->iColumn);
-      break;
-    }
-    case TK_REGISTER: {
-      sqlite3TreeViewLine(pView,"REGISTER(%d)", pExpr->iTable);
-      break;
-    }
-    case TK_AS: {
-      sqlite3TreeViewLine(pView,"AS %Q", pExpr->u.zToken);
-      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
-      break;
-    }
-    case TK_ID: {
-      sqlite3TreeViewLine(pView,"ID \"%w\"", pExpr->u.zToken);
-      break;
-    }
-#ifndef SQLITE_OMIT_CAST
-    case TK_CAST: {
-      /* Expressions of the form:   CAST(pLeft AS token) */
-      sqlite3TreeViewLine(pView,"CAST %Q", pExpr->u.zToken);
-      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
-      break;
-    }
-#endif /* SQLITE_OMIT_CAST */
-    case TK_LT:      zBinOp = "LT";     break;
-    case TK_LE:      zBinOp = "LE";     break;
-    case TK_GT:      zBinOp = "GT";     break;
-    case TK_GE:      zBinOp = "GE";     break;
-    case TK_NE:      zBinOp = "NE";     break;
-    case TK_EQ:      zBinOp = "EQ";     break;
-    case TK_IS:      zBinOp = "IS";     break;
-    case TK_ISNOT:   zBinOp = "ISNOT";  break;
-    case TK_AND:     zBinOp = "AND";    break;
-    case TK_OR:      zBinOp = "OR";     break;
-    case TK_PLUS:    zBinOp = "ADD";    break;
-    case TK_STAR:    zBinOp = "MUL";    break;
-    case TK_MINUS:   zBinOp = "SUB";    break;
-    case TK_REM:     zBinOp = "REM";    break;
-    case TK_BITAND:  zBinOp = "BITAND"; break;
-    case TK_BITOR:   zBinOp = "BITOR";  break;
-    case TK_SLASH:   zBinOp = "DIV";    break;
-    case TK_LSHIFT:  zBinOp = "LSHIFT"; break;
-    case TK_RSHIFT:  zBinOp = "RSHIFT"; break;
-    case TK_CONCAT:  zBinOp = "CONCAT"; break;
-    case TK_DOT:     zBinOp = "DOT";    break;
-
-    case TK_UMINUS:  zUniOp = "UMINUS"; break;
-    case TK_UPLUS:   zUniOp = "UPLUS";  break;
-    case TK_BITNOT:  zUniOp = "BITNOT"; break;
-    case TK_NOT:     zUniOp = "NOT";    break;
-    case TK_ISNULL:  zUniOp = "ISNULL"; break;
-    case TK_NOTNULL: zUniOp = "NOTNULL"; break;
-
-    case TK_COLLATE: {
-      sqlite3TreeViewLine(pView, "COLLATE %Q", pExpr->u.zToken);
-      sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
-      break;
-    }
-
-    case TK_AGG_FUNCTION:
-    case TK_FUNCTION: {
-      ExprList *pFarg;       /* List of function arguments */
-      if( ExprHasProperty(pExpr, EP_TokenOnly) ){
-        pFarg = 0;
-      }else{
-        pFarg = pExpr->x.pList;
-      }
-      if( pExpr->op==TK_AGG_FUNCTION ){
-        sqlite3TreeViewLine(pView, "AGG_FUNCTION%d %Q",
-                             pExpr->op2, pExpr->u.zToken);
-      }else{
-        sqlite3TreeViewLine(pView, "FUNCTION %Q", pExpr->u.zToken);
-      }
-      if( pFarg ){
-        sqlite3TreeViewExprList(pView, pFarg, 0, 0);
-      }
-      break;
-    }
-#ifndef SQLITE_OMIT_SUBQUERY
-    case TK_EXISTS: {
-      sqlite3TreeViewLine(pView, "EXISTS-expr");
-      sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
-      break;
-    }
-    case TK_SELECT: {
-      sqlite3TreeViewLine(pView, "SELECT-expr");
-      sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
-      break;
-    }
-    case TK_IN: {
-      sqlite3TreeViewLine(pView, "IN");
-      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
-      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
-        sqlite3TreeViewSelect(pView, pExpr->x.pSelect, 0);
-      }else{
-        sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
-      }
-      break;
-    }
-#endif /* SQLITE_OMIT_SUBQUERY */
-
-    /*
-    **    x BETWEEN y AND z
-    **
-    ** This is equivalent to
-    **
-    **    x>=y AND x<=z
-    **
-    ** X is stored in pExpr->pLeft.
-    ** Y is stored in pExpr->pList->a[0].pExpr.
-    ** Z is stored in pExpr->pList->a[1].pExpr.
-    */
-    case TK_BETWEEN: {
-      Expr *pX = pExpr->pLeft;
-      Expr *pY = pExpr->x.pList->a[0].pExpr;
-      Expr *pZ = pExpr->x.pList->a[1].pExpr;
-      sqlite3TreeViewLine(pView, "BETWEEN");
-      sqlite3TreeViewExpr(pView, pX, 1);
-      sqlite3TreeViewExpr(pView, pY, 1);
-      sqlite3TreeViewExpr(pView, pZ, 0);
-      break;
-    }
-    case TK_TRIGGER: {
-      /* If the opcode is TK_TRIGGER, then the expression is a reference
-      ** to a column in the new.* or old.* pseudo-tables available to
-      ** trigger programs. In this case Expr.iTable is set to 1 for the
-      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
-      ** is set to the column of the pseudo-table to read, or to -1 to
-      ** read the rowid field.
-      */
-      sqlite3TreeViewLine(pView, "%s(%d)", 
-          pExpr->iTable ? "NEW" : "OLD", pExpr->iColumn);
-      break;
-    }
-    case TK_CASE: {
-      sqlite3TreeViewLine(pView, "CASE");
-      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
-      sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
-      break;
-    }
-#ifndef SQLITE_OMIT_TRIGGER
-    case TK_RAISE: {
-      const char *zType = "unk";
-      switch( pExpr->affinity ){
-        case OE_Rollback:   zType = "rollback";  break;
-        case OE_Abort:      zType = "abort";     break;
-        case OE_Fail:       zType = "fail";      break;
-        case OE_Ignore:     zType = "ignore";    break;
-      }
-      sqlite3TreeViewLine(pView, "RAISE %s(%Q)", zType, pExpr->u.zToken);
-      break;
-    }
-#endif
-    default: {
-      sqlite3TreeViewLine(pView, "op=%d", pExpr->op);
-      break;
-    }
-  }
-  if( zBinOp ){
-    sqlite3TreeViewLine(pView, "%s", zBinOp);
-    sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
-    sqlite3TreeViewExpr(pView, pExpr->pRight, 0);
-  }else if( zUniOp ){
-    sqlite3TreeViewLine(pView, "%s", zUniOp);
-    sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
-  }
-  sqlite3TreeViewPop(pView);
-}
-#endif /* SQLITE_DEBUG */
-
-#ifdef SQLITE_DEBUG
-/*
-** Generate a human-readable explanation of an expression list.
-*/
-SQLITE_PRIVATE void sqlite3TreeViewExprList(
-  TreeView *pView,
-  const ExprList *pList,
-  u8 moreToFollow,
-  const char *zLabel
-){
-  int i;
-  pView = sqlite3TreeViewPush(pView, moreToFollow);
-  if( zLabel==0 || zLabel[0]==0 ) zLabel = "LIST";
-  if( pList==0 ){
-    sqlite3TreeViewLine(pView, "%s (empty)", zLabel);
-  }else{
-    sqlite3TreeViewLine(pView, "%s", zLabel);
-    for(i=0; i<pList->nExpr; i++){
-      sqlite3TreeViewExpr(pView, pList->a[i].pExpr, i<pList->nExpr-1);
-#if 0
-     if( pList->a[i].zName ){
-        sqlite3ExplainPrintf(pOut, " AS %s", pList->a[i].zName);
-      }
-      if( pList->a[i].bSpanIsTab ){
-        sqlite3ExplainPrintf(pOut, " (%s)", pList->a[i].zSpan);
-      }
-#endif
-    }
-  }
-  sqlite3TreeViewPop(pView);
-}
-#endif /* SQLITE_DEBUG */
-
 /*
 ** Generate code that pushes the value of every element of the given
 ** expression list into a sequence of registers beginning at target.
@@ -86766,6 +87846,21 @@ SQLITE_PRIVATE void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int
   sqlite3ReleaseTempReg(pParse, regFree2);
 }
 
+/*
+** Like sqlite3ExprIfFalse() except that a copy is made of pExpr before
+** code generation, and that copy is deleted after code generation. This
+** ensures that the original pExpr is unchanged.
+*/
+SQLITE_PRIVATE void sqlite3ExprIfFalseDup(Parse *pParse, Expr *pExpr, int dest,int jumpIfNull){
+  sqlite3 *db = pParse->db;
+  Expr *pCopy = sqlite3ExprDup(db, pExpr, 0);
+  if( db->mallocFailed==0 ){
+    sqlite3ExprIfFalse(pParse, pCopy, dest, jumpIfNull);
+  }
+  sqlite3ExprDelete(db, pCopy);
+}
+
+
 /*
 ** Do a deep comparison of two expression trees.  Return 0 if the two
 ** expressions are completely identical.  Return 1 if they differ only
@@ -87239,6 +88334,7 @@ SQLITE_PRIVATE void sqlite3ClearTempRegCache(Parse *pParse){
 ** This file contains C code routines that used to generate VDBE code
 ** that implements the ALTER TABLE command.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** The code in this file only exists if we are not omitting the
@@ -87918,7 +89014,7 @@ SQLITE_PRIVATE void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
   if( pDflt ){
     sqlite3_value *pVal = 0;
     int rc;
-    rc = sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_NONE, &pVal);
+    rc = sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_BLOB, &pVal);
     assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
     if( rc!=SQLITE_OK ){
       db->mallocFailed = 1;
@@ -88201,6 +89297,7 @@ exit_begin_add_column:
 ** integer in the equivalent columns in sqlite_stat4.
 */
 #ifndef SQLITE_OMIT_ANALYZE
+/* #include "sqliteInt.h" */
 
 #if defined(SQLITE_ENABLE_STAT4)
 # define IsStat4     1
@@ -89003,7 +90100,7 @@ static void callStatGet(Vdbe *v, int regStat4, int iParam, int regOut){
 #else
   UNUSED_PARAMETER( iParam );
 #endif
-  sqlite3VdbeAddOp3(v, OP_Function, 0, regStat4, regOut);
+  sqlite3VdbeAddOp3(v, OP_Function0, 0, regStat4, regOut);
   sqlite3VdbeChangeP4(v, -1, (char*)&statGetFuncdef, P4_FUNCDEF);
   sqlite3VdbeChangeP5(v, 1 + IsStat34);
 }
@@ -89158,7 +90255,7 @@ static void analyzeOneTable(
 #endif
     sqlite3VdbeAddOp2(v, OP_Integer, nCol, regStat4+1);
     sqlite3VdbeAddOp2(v, OP_Integer, pIdx->nKeyCol, regStat4+2);
-    sqlite3VdbeAddOp3(v, OP_Function, 0, regStat4+1, regStat4);
+    sqlite3VdbeAddOp3(v, OP_Function0, 0, regStat4+1, regStat4);
     sqlite3VdbeChangeP4(v, -1, (char*)&statInitFuncdef, P4_FUNCDEF);
     sqlite3VdbeChangeP5(v, 2+IsStat34);
 
@@ -89254,7 +90351,7 @@ static void analyzeOneTable(
     }
 #endif
     assert( regChng==(regStat4+1) );
-    sqlite3VdbeAddOp3(v, OP_Function, 1, regStat4, regTemp);
+    sqlite3VdbeAddOp3(v, OP_Function0, 1, regStat4, regTemp);
     sqlite3VdbeChangeP4(v, -1, (char*)&statPushFuncdef, P4_FUNCDEF);
     sqlite3VdbeChangeP5(v, 2+IsStat34);
     sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
@@ -89966,6 +91063,7 @@ SQLITE_PRIVATE int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
 *************************************************************************
 ** This file contains code used to implement the ATTACH and DETACH commands.
 */
+/* #include "sqliteInt.h" */
 
 #ifndef SQLITE_OMIT_ATTACH
 /*
@@ -90313,7 +91411,7 @@ static void codeAttach(
 
   assert( v || db->mallocFailed );
   if( v ){
-    sqlite3VdbeAddOp3(v, OP_Function, 0, regArgs+3-pFunc->nArg, regArgs+3);
+    sqlite3VdbeAddOp3(v, OP_Function0, 0, regArgs+3-pFunc->nArg, regArgs+3);
     assert( pFunc->nArg==-1 || (pFunc->nArg&0xff)==pFunc->nArg );
     sqlite3VdbeChangeP5(v, (u8)(pFunc->nArg));
     sqlite3VdbeChangeP4(v, -1, (char *)pFunc, P4_FUNCDEF);
@@ -90555,6 +91653,7 @@ SQLITE_PRIVATE int sqlite3FixTriggerStep(
 ** systems that do not need this facility may omit it by recompiling
 ** the library with -DSQLITE_OMIT_AUTHORIZATION=1
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** All of the code in this file may be omitted by defining a single
@@ -90825,6 +91924,7 @@ SQLITE_PRIVATE void sqlite3AuthContextPop(AuthContext *pContext){
 **     COMMIT
 **     ROLLBACK
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** This routine is called when a new SQL statement is beginning to
@@ -91778,7 +92878,7 @@ SQLITE_PRIVATE void sqlite3StartTable(
     int j1;
     int fileFormat;
     int reg1, reg2, reg3;
-    sqlite3BeginWriteOperation(pParse, 0, iDb);
+    sqlite3BeginWriteOperation(pParse, 1, iDb);
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( isVirtual ){
@@ -91894,10 +92994,10 @@ SQLITE_PRIVATE void sqlite3AddColumn(Parse *pParse, Token *pName){
   pCol->zName = z;
  
   /* If there is no type specified, columns have the default affinity
-  ** 'NONE'. If there is a type specified, then sqlite3AddColumnType() will
+  ** 'BLOB'. If there is a type specified, then sqlite3AddColumnType() will
   ** be called next to set pCol->affinity correctly.
   */
-  pCol->affinity = SQLITE_AFF_NONE;
+  pCol->affinity = SQLITE_AFF_BLOB;
   pCol->szEst = 1;
   p->nCol++;
 }
@@ -91932,7 +93032,7 @@ SQLITE_PRIVATE void sqlite3AddNotNull(Parse *pParse, int onError){
 ** 'CHAR'        | SQLITE_AFF_TEXT
 ** 'CLOB'        | SQLITE_AFF_TEXT
 ** 'TEXT'        | SQLITE_AFF_TEXT
-** 'BLOB'        | SQLITE_AFF_NONE
+** 'BLOB'        | SQLITE_AFF_BLOB
 ** 'REAL'        | SQLITE_AFF_REAL
 ** 'FLOA'        | SQLITE_AFF_REAL
 ** 'DOUB'        | SQLITE_AFF_REAL
@@ -91958,7 +93058,7 @@ SQLITE_PRIVATE char sqlite3AffinityType(const char *zIn, u8 *pszEst){
       aff = SQLITE_AFF_TEXT;
     }else if( h==(('b'<<24)+('l'<<16)+('o'<<8)+'b')          /* BLOB */
         && (aff==SQLITE_AFF_NUMERIC || aff==SQLITE_AFF_REAL) ){
-      aff = SQLITE_AFF_NONE;
+      aff = SQLITE_AFF_BLOB;
       if( zIn[0]=='(' ) zChar = zIn;
 #ifndef SQLITE_OMIT_FLOATING_POINT
     }else if( h==(('r'<<24)+('e'<<16)+('a'<<8)+'l')          /* REAL */
@@ -92127,14 +93227,11 @@ SQLITE_PRIVATE void sqlite3AddPrimaryKey(
        "INTEGER PRIMARY KEY");
 #endif
   }else{
-    Vdbe *v = pParse->pVdbe;
     Index *p;
-    if( v ) pParse->addrSkipPK = sqlite3VdbeAddOp0(v, OP_Noop);
     p = sqlite3CreateIndex(pParse, 0, 0, 0, pList, onError, 0,
                            0, sortOrder, 0);
     if( p ){
       p->idxType = SQLITE_IDXTYPE_PRIMARYKEY;
-      if( v ) sqlite3VdbeJumpHere(v, pParse->addrSkipPK);
     }
     pList = 0;
   }
@@ -92353,7 +93450,7 @@ static char *createTableStmt(sqlite3 *db, Table *p){
   zStmt[k++] = '(';
   for(pCol=p->aCol, i=0; i<p->nCol; i++, pCol++){
     static const char * const azType[] = {
-        /* SQLITE_AFF_NONE    */ "",
+        /* SQLITE_AFF_BLOB    */ "",
         /* SQLITE_AFF_TEXT    */ " TEXT",
         /* SQLITE_AFF_NUMERIC */ " NUM",
         /* SQLITE_AFF_INTEGER */ " INT",
@@ -92366,17 +93463,17 @@ static char *createTableStmt(sqlite3 *db, Table *p){
     k += sqlite3Strlen30(&zStmt[k]);
     zSep = zSep2;
     identPut(zStmt, &k, pCol->zName);
-    assert( pCol->affinity-SQLITE_AFF_NONE >= 0 );
-    assert( pCol->affinity-SQLITE_AFF_NONE < ArraySize(azType) );
-    testcase( pCol->affinity==SQLITE_AFF_NONE );
+    assert( pCol->affinity-SQLITE_AFF_BLOB >= 0 );
+    assert( pCol->affinity-SQLITE_AFF_BLOB < ArraySize(azType) );
+    testcase( pCol->affinity==SQLITE_AFF_BLOB );
     testcase( pCol->affinity==SQLITE_AFF_TEXT );
     testcase( pCol->affinity==SQLITE_AFF_NUMERIC );
     testcase( pCol->affinity==SQLITE_AFF_INTEGER );
     testcase( pCol->affinity==SQLITE_AFF_REAL );
     
-    zType = azType[pCol->affinity - SQLITE_AFF_NONE];
+    zType = azType[pCol->affinity - SQLITE_AFF_BLOB];
     len = sqlite3Strlen30(zType);
-    assert( pCol->affinity==SQLITE_AFF_NONE 
+    assert( pCol->affinity==SQLITE_AFF_BLOB 
             || pCol->affinity==sqlite3AffinityType(zType, 0) );
     memcpy(&zStmt[k], zType, len);
     k += len;
@@ -92487,14 +93584,6 @@ static void convertToWithoutRowidTable(Parse *pParse, Table *pTab){
     sqlite3VdbeGetOp(v, pParse->addrCrTab)->opcode = OP_CreateIndex;
   }
 
-  /* Bypass the creation of the PRIMARY KEY btree and the sqlite_master
-  ** table entry.
-  */
-  if( pParse->addrSkipPK ){
-    assert( v );
-    sqlite3VdbeGetOp(v, pParse->addrSkipPK)->opcode = OP_Goto;
-  }
-
   /* Locate the PRIMARY KEY index.  Or, if this table was originally
   ** an INTEGER PRIMARY KEY table, create a new PRIMARY KEY index. 
   */
@@ -92512,6 +93601,16 @@ static void convertToWithoutRowidTable(Parse *pParse, Table *pTab){
     pTab->iPKey = -1;
   }else{
     pPk = sqlite3PrimaryKeyIndex(pTab);
+
+    /* Bypass the creation of the PRIMARY KEY btree and the sqlite_master
+    ** table entry. This is only required if currently generating VDBE
+    ** code for a CREATE TABLE (not when parsing one as part of reading
+    ** a database schema).  */
+    if( v ){
+      assert( db->init.busy==0 );
+      sqlite3VdbeGetOp(v, pPk->tnum)->opcode = OP_Goto;
+    }
+
     /*
     ** Remove all redundant columns from the PRIMARY KEY.  For example, change
     ** "PRIMARY KEY(a,b,a,b,c,b,c,d)" into just "PRIMARY KEY(a,b,c,d)".  Later
@@ -92647,7 +93746,7 @@ SQLITE_PRIVATE void sqlite3EndTable(
     if( (p->tabFlags & TF_HasPrimaryKey)==0 ){
       sqlite3ErrorMsg(pParse, "PRIMARY KEY missing on table %s", p->zName);
     }else{
-      p->tabFlags |= TF_WithoutRowid;
+      p->tabFlags |= TF_WithoutRowid | TF_NoVisibleRowid;
       convertToWithoutRowidTable(pParse, p);
     }
   }
@@ -92715,26 +93814,46 @@ SQLITE_PRIVATE void sqlite3EndTable(
     ** be redundant.
     */
     if( pSelect ){
-      SelectDest dest;
-      Table *pSelTab;
-
+      SelectDest dest;    /* Where the SELECT should store results */
+      int regYield;       /* Register holding co-routine entry-point */
+      int addrTop;        /* Top of the co-routine */
+      int regRec;         /* A record to be insert into the new table */
+      int regRowid;       /* Rowid of the next row to insert */
+      int addrInsLoop;    /* Top of the loop for inserting rows */
+      Table *pSelTab;     /* A table that describes the SELECT results */
+
+      regYield = ++pParse->nMem;
+      regRec = ++pParse->nMem;
+      regRowid = ++pParse->nMem;
       assert(pParse->nTab==1);
+      sqlite3MayAbort(pParse);
       sqlite3VdbeAddOp3(v, OP_OpenWrite, 1, pParse->regRoot, iDb);
       sqlite3VdbeChangeP5(v, OPFLAG_P2ISREG);
       pParse->nTab = 2;
-      sqlite3SelectDestInit(&dest, SRT_Table, 1);
+      addrTop = sqlite3VdbeCurrentAddr(v) + 1;
+      sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, addrTop);
+      sqlite3SelectDestInit(&dest, SRT_Coroutine, regYield);
       sqlite3Select(pParse, pSelect, &dest);
+      sqlite3VdbeAddOp1(v, OP_EndCoroutine, regYield);
+      sqlite3VdbeJumpHere(v, addrTop - 1);
+      if( pParse->nErr ) return;
+      pSelTab = sqlite3ResultSetOfSelect(pParse, pSelect);
+      if( pSelTab==0 ) return;
+      assert( p->aCol==0 );
+      p->nCol = pSelTab->nCol;
+      p->aCol = pSelTab->aCol;
+      pSelTab->nCol = 0;
+      pSelTab->aCol = 0;
+      sqlite3DeleteTable(db, pSelTab);
+      addrInsLoop = sqlite3VdbeAddOp1(v, OP_Yield, dest.iSDParm);
+      VdbeCoverage(v);
+      sqlite3VdbeAddOp3(v, OP_MakeRecord, dest.iSdst, dest.nSdst, regRec);
+      sqlite3TableAffinity(v, p, 0);
+      sqlite3VdbeAddOp2(v, OP_NewRowid, 1, regRowid);
+      sqlite3VdbeAddOp3(v, OP_Insert, 1, regRec, regRowid);
+      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrInsLoop);
+      sqlite3VdbeJumpHere(v, addrInsLoop);
       sqlite3VdbeAddOp1(v, OP_Close, 1);
-      if( pParse->nErr==0 ){
-        pSelTab = sqlite3ResultSetOfSelect(pParse, pSelect);
-        if( pSelTab==0 ) return;
-        assert( p->aCol==0 );
-        p->nCol = pSelTab->nCol;
-        p->aCol = pSelTab->aCol;
-        pSelTab->nCol = 0;
-        pSelTab->aCol = 0;
-        sqlite3DeleteTable(db, pSelTab);
-      }
     }
 
     /* Compute the complete text of the CREATE statement */
@@ -94033,10 +95152,15 @@ SQLITE_PRIVATE Index *sqlite3CreateIndex(
     v = sqlite3GetVdbe(pParse);
     if( v==0 ) goto exit_create_index;
 
-
-    /* Create the rootpage for the index
-    */
     sqlite3BeginWriteOperation(pParse, 1, iDb);
+
+    /* Create the rootpage for the index using CreateIndex. But before
+    ** doing so, code a Noop instruction and store its address in 
+    ** Index.tnum. This is required in case this index is actually a 
+    ** PRIMARY KEY and the table is actually a WITHOUT ROWID table. In 
+    ** that case the convertToWithoutRowidTable() routine will replace
+    ** the Noop with a Goto to jump over the VDBE code generated below. */
+    pIndex->tnum = sqlite3VdbeAddOp0(v, OP_Noop);
     sqlite3VdbeAddOp2(v, OP_CreateIndex, iDb, iMem);
 
     /* Gather the complete text of the CREATE INDEX statement into
@@ -94076,6 +95200,8 @@ SQLITE_PRIVATE Index *sqlite3CreateIndex(
          sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName));
       sqlite3VdbeAddOp1(v, OP_Expire, 0);
     }
+
+    sqlite3VdbeJumpHere(v, pIndex->tnum);
   }
 
   /* When adding an index to the list of indices for a table, make
@@ -94478,7 +95604,7 @@ SQLITE_PRIVATE void sqlite3SrcListDelete(sqlite3 *db, SrcList *pList){
     sqlite3DbFree(db, pItem->zDatabase);
     sqlite3DbFree(db, pItem->zName);
     sqlite3DbFree(db, pItem->zAlias);
-    sqlite3DbFree(db, pItem->zIndex);
+    sqlite3DbFree(db, pItem->zIndexedBy);
     sqlite3DeleteTable(db, pItem->pTab);
     sqlite3SelectDelete(db, pItem->pSelect);
     sqlite3ExprDelete(db, pItem->pOn);
@@ -94551,13 +95677,13 @@ SQLITE_PRIVATE void sqlite3SrcListIndexedBy(Parse *pParse, SrcList *p, Token *pI
   assert( pIndexedBy!=0 );
   if( p && ALWAYS(p->nSrc>0) ){
     struct SrcList_item *pItem = &p->a[p->nSrc-1];
-    assert( pItem->notIndexed==0 && pItem->zIndex==0 );
+    assert( pItem->notIndexed==0 && pItem->zIndexedBy==0 );
     if( pIndexedBy->n==1 && !pIndexedBy->z ){
       /* A "NOT INDEXED" clause was supplied. See parse.y 
       ** construct "indexed_opt" for details. */
       pItem->notIndexed = 1;
     }else{
-      pItem->zIndex = sqlite3NameFromToken(pParse->db, pIndexedBy);
+      pItem->zIndexedBy = sqlite3NameFromToken(pParse->db, pIndexedBy);
     }
   }
 }
@@ -95119,6 +96245,7 @@ SQLITE_PRIVATE void sqlite3WithDelete(sqlite3 *db, With *pWith){
 ** of user defined functions and collation sequences.
 */
 
+/* #include "sqliteInt.h" */
 
 /*
 ** Invoke the 'collation needed' callback to request a collation sequence
@@ -95596,6 +96723,7 @@ SQLITE_PRIVATE Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
 ** This file contains C code routines that are called by the parser
 ** in order to generate code for DELETE FROM statements.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** While a SrcList can in general represent multiple tables and subqueries
@@ -96381,8 +97509,8 @@ SQLITE_PRIVATE int sqlite3GenerateIndexKey(
       *piPartIdxLabel = sqlite3VdbeMakeLabel(v);
       pParse->iPartIdxTab = iDataCur;
       sqlite3ExprCachePush(pParse);
-      sqlite3ExprIfFalse(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel, 
-                         SQLITE_JUMPIFNULL);
+      sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel, 
+                            SQLITE_JUMPIFNULL);
     }else{
       *piPartIdxLabel = 0;
     }
@@ -96438,8 +97566,10 @@ SQLITE_PRIVATE void sqlite3ResolvePartIdxLabel(Parse *pParse, int iLabel){
 ** functions of SQLite.  (Some function, and in particular the date and
 ** time functions, are implemented separately.)
 */
+/* #include "sqliteInt.h" */
 /* #include <stdlib.h> */
 /* #include <assert.h> */
+/* #include "vdbeInt.h" */
 
 /*
 ** Return the collating function associated with a function.
@@ -96998,17 +98128,15 @@ struct compareInfo {
 
 /*
 ** For LIKE and GLOB matching on EBCDIC machines, assume that every
-** character is exactly one byte in size.  Also, all characters are
-** able to participate in upper-case-to-lower-case mappings in EBCDIC
-** whereas only characters less than 0x80 do in ASCII.
+** character is exactly one byte in size.  Also, provde the Utf8Read()
+** macro for fast reading of the next character in the common case where
+** the next character is ASCII.
 */
 #if defined(SQLITE_EBCDIC)
 # define sqlite3Utf8Read(A)        (*((*A)++))
-# define GlobUpperToLower(A)       A = sqlite3UpperToLower[A]
-# define GlobUpperToLowerAscii(A)  A = sqlite3UpperToLower[A]
+# define Utf8Read(A)               (*(A++))
 #else
-# define GlobUpperToLower(A)       if( A<=0x7f ){ A = sqlite3UpperToLower[A]; }
-# define GlobUpperToLowerAscii(A)  A = sqlite3UpperToLower[A]
+# define Utf8Read(A)               (A[0]<0x80?*(A++):sqlite3Utf8Read(&A))
 #endif
 
 static const struct compareInfo globInfo = { '*', '?', '[', 0 };
@@ -97050,7 +98178,7 @@ static const struct compareInfo likeInfoAlt = { '%', '_',   0, 0 };
 **      Ec        Where E is the "esc" character and c is any other
 **                character, including '%', '_', and esc, match exactly c.
 **
-** The comments through this routine usually assume glob matching.
+** The comments within this routine usually assume glob matching.
 **
 ** This routine is usually quick, but can be N**2 in the worst case.
 */
@@ -97074,13 +98202,12 @@ static int patternCompare(
   */
   matchOther = esc ? esc : pInfo->matchSet;
 
-  while( (c = sqlite3Utf8Read(&zPattern))!=0 ){
+  while( (c = Utf8Read(zPattern))!=0 ){
     if( c==matchAll ){  /* Match "*" */
       /* Skip over multiple "*" characters in the pattern.  If there
       ** are also "?" characters, skip those as well, but consume a
       ** single character of the input string for each "?" skipped */
-      while( (c=sqlite3Utf8Read(&zPattern)) == matchAll
-               || c == matchOne ){
+      while( (c=Utf8Read(zPattern)) == matchAll || c == matchOne ){
         if( c==matchOne && sqlite3Utf8Read(&zString)==0 ){
           return 0;
         }
@@ -97125,7 +98252,7 @@ static int patternCompare(
           if( patternCompare(zPattern,zString,pInfo,esc) ) return 1;
         }
       }else{
-        while( (c2 = sqlite3Utf8Read(&zString))!=0 ){
+        while( (c2 = Utf8Read(zString))!=0 ){
           if( c2!=c ) continue;
           if( patternCompare(zPattern,zString,pInfo,esc) ) return 1;
         }
@@ -97171,7 +98298,7 @@ static int patternCompare(
         continue;
       }
     }
-    c2 = sqlite3Utf8Read(&zString);
+    c2 = Utf8Read(zString);
     if( c==c2 ) continue;
     if( noCase && c<0x80 && c2<0x80 && sqlite3Tolower(c)==sqlite3Tolower(c2) ){
       continue;
@@ -97548,16 +98675,14 @@ static void zeroblobFunc(
   sqlite3_value **argv
 ){
   i64 n;
-  sqlite3 *db = sqlite3_context_db_handle(context);
+  int rc;
   assert( argc==1 );
   UNUSED_PARAMETER(argc);
   n = sqlite3_value_int64(argv[0]);
-  testcase( n==db->aLimit[SQLITE_LIMIT_LENGTH] );
-  testcase( n==db->aLimit[SQLITE_LIMIT_LENGTH]+1 );
-  if( n>db->aLimit[SQLITE_LIMIT_LENGTH] ){
-    sqlite3_result_error_toobig(context);
-  }else{
-    sqlite3_result_zeroblob(context, (int)n); /* IMP: R-00293-64994 */
+  if( n<0 ) n = 0;
+  rc = sqlite3_result_zeroblob64(context, n); /* IMP: R-00293-64994 */
+  if( rc ){
+    sqlite3_result_error_code(context, rc);
   }
 }
 
@@ -98238,6 +99363,7 @@ SQLITE_PRIVATE void sqlite3RegisterGlobalFunctions(void){
 ** This file contains code used by the compiler to add foreign key
 ** support to compiled SQL statements.
 */
+/* #include "sqliteInt.h" */
 
 #ifndef SQLITE_OMIT_FOREIGN_KEY
 #ifndef SQLITE_OMIT_TRIGGER
@@ -99642,6 +100768,7 @@ SQLITE_PRIVATE void sqlite3FkDelete(sqlite3 *db, Table *pTab){
 ** This file contains C code routines that are called by the parser
 ** to handle INSERT statements in SQLite.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** Generate code that will 
@@ -99671,7 +100798,7 @@ SQLITE_PRIVATE void sqlite3OpenTable(
   }else{
     Index *pPk = sqlite3PrimaryKeyIndex(pTab);
     assert( pPk!=0 );
-    assert( pPk->tnum=pTab->tnum );
+    assert( pPk->tnum==pTab->tnum );
     sqlite3VdbeAddOp3(v, opcode, iCur, pPk->tnum, iDb);
     sqlite3VdbeSetP4KeyInfo(pParse, pPk);
     VdbeComment((v, "%s", pTab->zName));
@@ -99685,7 +100812,7 @@ SQLITE_PRIVATE void sqlite3OpenTable(
 **
 **  Character      Column affinity
 **  ------------------------------
-**  'A'            NONE
+**  'A'            BLOB
 **  'B'            TEXT
 **  'C'            NUMERIC
 **  'D'            INTEGER
@@ -99728,9 +100855,9 @@ SQLITE_PRIVATE const char *sqlite3IndexAffinityStr(Vdbe *v, Index *pIdx){
 
 /*
 ** Compute the affinity string for table pTab, if it has not already been
-** computed.  As an optimization, omit trailing SQLITE_AFF_NONE affinities.
+** computed.  As an optimization, omit trailing SQLITE_AFF_BLOB affinities.
 **
-** If the affinity exists (if it is no entirely SQLITE_AFF_NONE values) and
+** If the affinity exists (if it is no entirely SQLITE_AFF_BLOB values) and
 ** if iReg>0 then code an OP_Affinity opcode that will set the affinities
 ** for register iReg and following.  Or if affinities exists and iReg==0,
 ** then just set the P4 operand of the previous opcode (which should  be
@@ -99740,7 +100867,7 @@ SQLITE_PRIVATE const char *sqlite3IndexAffinityStr(Vdbe *v, Index *pIdx){
 **
 **  Character      Column affinity
 **  ------------------------------
-**  'A'            NONE
+**  'A'            BLOB
 **  'B'            TEXT
 **  'C'            NUMERIC
 **  'D'            INTEGER
@@ -99762,7 +100889,7 @@ SQLITE_PRIVATE void sqlite3TableAffinity(Vdbe *v, Table *pTab, int iReg){
     }
     do{
       zColAff[i--] = 0;
-    }while( i>=0 && zColAff[i]==SQLITE_AFF_NONE );
+    }while( i>=0 && zColAff[i]==SQLITE_AFF_BLOB );
     pTab->zColAff = zColAff;
   }
   i = sqlite3Strlen30(zColAff);
@@ -101010,8 +102137,8 @@ SQLITE_PRIVATE void sqlite3GenerateConstraintChecks(
     if( pIdx->pPartIdxWhere ){
       sqlite3VdbeAddOp2(v, OP_Null, 0, aRegIdx[ix]);
       pParse->ckBase = regNewData+1;
-      sqlite3ExprIfFalse(pParse, pIdx->pPartIdxWhere, addrUniqueOk,
-                         SQLITE_JUMPIFNULL);
+      sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, addrUniqueOk,
+                            SQLITE_JUMPIFNULL);
       pParse->ckBase = 0;
     }
 
@@ -101625,7 +102752,7 @@ static int xferOptimization(
     sqlite3TableLock(pParse, iDbSrc, pSrc->tnum, 0, pSrc->zName);
   }
   for(pDestIdx=pDest->pIndex; pDestIdx; pDestIdx=pDestIdx->pNext){
-    u8 useSeekResult = 0;
+    u8 idxInsFlags = 0;
     for(pSrcIdx=pSrc->pIndex; ALWAYS(pSrcIdx); pSrcIdx=pSrcIdx->pNext){
       if( xferCompatibleIndex(pDestIdx, pSrcIdx) ) break;
     }
@@ -101660,12 +102787,15 @@ static int xferOptimization(
         if( sqlite3_stricmp("BINARY", zColl) ) break;
       }
       if( i==pSrcIdx->nColumn ){
-        useSeekResult = OPFLAG_USESEEKRESULT;
+        idxInsFlags = OPFLAG_USESEEKRESULT;
         sqlite3VdbeAddOp3(v, OP_Last, iDest, 0, -1);
       }
     }
+    if( !HasRowid(pSrc) && pDestIdx->idxType==2 ){
+      idxInsFlags |= OPFLAG_NCHANGE;
+    }
     sqlite3VdbeAddOp3(v, OP_IdxInsert, iDest, regData, 1);
-    sqlite3VdbeChangeP5(v, useSeekResult);
+    sqlite3VdbeChangeP5(v, idxInsFlags);
     sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1+1); VdbeCoverage(v);
     sqlite3VdbeJumpHere(v, addr1);
     sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
@@ -101704,6 +102834,7 @@ static int xferOptimization(
 ** accessed by users of the library.
 */
 
+/* #include "sqliteInt.h" */
 
 /*
 ** Execute SQL code.  Return one of the SQLITE_ success/failure
@@ -101872,6 +103003,7 @@ exec_out:
 */
 #ifndef _SQLITE3EXT_H_
 #define _SQLITE3EXT_H_
+/* #include "sqlite3.h" */
 
 typedef struct sqlite3_api_routines sqlite3_api_routines;
 
@@ -102121,6 +103253,11 @@ struct sqlite3_api_routines {
   void (*result_text64)(sqlite3_context*,const char*,sqlite3_uint64,
                          void(*)(void*), unsigned char);
   int (*strglob)(const char*,const char*);
+  /* Version 3.8.11 and later */
+  sqlite3_value *(*value_dup)(const sqlite3_value*);
+  void (*value_free)(sqlite3_value*);
+  int (*result_zeroblob64)(sqlite3_context*,sqlite3_uint64);
+  int (*bind_zeroblob64)(sqlite3_stmt*, int, sqlite3_uint64);
 };
 
 /*
@@ -102351,6 +103488,11 @@ struct sqlite3_api_routines {
 #define sqlite3_result_blob64          sqlite3_api->result_blob64
 #define sqlite3_result_text64          sqlite3_api->result_text64
 #define sqlite3_strglob                sqlite3_api->strglob
+/* Version 3.8.11 and later */
+#define sqlite3_value_dup              sqlite3_api->value_dup
+#define sqlite3_value_free             sqlite3_api->value_free
+#define sqlite3_result_zeroblob64      sqlite3_api->result_zeroblob64
+#define sqlite3_bind_zeroblob64        sqlite3_api->bind_zeroblob64
 #endif /* SQLITE_CORE */
 
 #ifndef SQLITE_CORE
@@ -102372,6 +103514,7 @@ struct sqlite3_api_routines {
 
 /************** End of sqlite3ext.h ******************************************/
 /************** Continuing where we left off in loadext.c ********************/
+/* #include "sqliteInt.h" */
 /* #include <string.h> */
 
 #ifndef SQLITE_OMIT_LOAD_EXTENSION
@@ -102756,7 +103899,12 @@ static const sqlite3_api_routines sqlite3Apis = {
   sqlite3_reset_auto_extension,
   sqlite3_result_blob64,
   sqlite3_result_text64,
-  sqlite3_strglob
+  sqlite3_strglob,
+  /* Version 3.8.11 and later */
+  (sqlite3_value*(*)(const sqlite3_value*))sqlite3_value_dup,
+  sqlite3_value_free,
+  sqlite3_result_zeroblob64,
+  sqlite3_bind_zeroblob64
 };
 
 /*
@@ -103138,6 +104286,7 @@ SQLITE_PRIVATE void sqlite3AutoLoadExtensions(sqlite3 *db){
 *************************************************************************
 ** This file contains code used to implement the PRAGMA command.
 */
+/* #include "sqliteInt.h" */
 
 #if !defined(SQLITE_ENABLE_LOCKING_STYLE)
 #  if defined(__APPLE__)
@@ -103244,7 +104393,7 @@ static const struct sPragmaNames {
 #if !defined(SQLITE_OMIT_PAGER_PRAGMAS)
   { /* zName:     */ "cache_size",
     /* ePragTyp:  */ PragTyp_CACHE_SIZE,
-    /* ePragFlag: */ PragFlag_NeedSchema,
+    /* ePragFlag: */ 0,
     /* iArg:      */ 0 },
 #endif
 #if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
@@ -103257,6 +104406,10 @@ static const struct sPragmaNames {
     /* ePragTyp:  */ PragTyp_CASE_SENSITIVE_LIKE,
     /* ePragFlag: */ 0,
     /* iArg:      */ 0 },
+  { /* zName:     */ "cell_size_check",
+    /* ePragTyp:  */ PragTyp_FLAG,
+    /* ePragFlag: */ 0,
+    /* iArg:      */ SQLITE_CellSizeCk },
 #if !defined(SQLITE_OMIT_FLAG_PRAGMAS)
   { /* zName:     */ "checkpoint_fullfsync",
     /* ePragTyp:  */ PragTyp_FLAG,
@@ -103614,7 +104767,7 @@ static const struct sPragmaNames {
     /* iArg:      */ SQLITE_WriteSchema|SQLITE_RecoveryMode },
 #endif
 };
-/* Number of pragmas: 59 on by default, 72 total. */
+/* Number of pragmas: 60 on by default, 73 total. */
 
 /************** End of pragma.h **********************************************/
 /************** Continuing where we left off in pragma.c *********************/
@@ -104310,11 +105463,13 @@ SQLITE_PRIVATE void sqlite3Pragma(
   case PragTyp_CACHE_SIZE: {
     assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
     if( !zRight ){
+      if( sqlite3ReadSchema(pParse) ) goto pragma_out;
       returnSingleInt(pParse, "cache_size", pDb->pSchema->cache_size);
     }else{
       int size = sqlite3Atoi(zRight);
       pDb->pSchema->cache_size = size;
       sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
+      if( sqlite3ReadSchema(pParse) ) goto pragma_out;
     }
     break;
   }
@@ -105585,6 +106740,7 @@ pragma_out:
 ** interface, and routines that contribute to loading the database schema
 ** from disk.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** Fill the InitData structure with an error message that indicates
@@ -105597,13 +106753,13 @@ static void corruptSchema(
 ){
   sqlite3 *db = pData->db;
   if( !db->mallocFailed && (db->flags & SQLITE_RecoveryMode)==0 ){
+    char *z;
     if( zObj==0 ) zObj = "?";
-    sqlite3SetString(pData->pzErrMsg, db,
-      "malformed database schema (%s)", zObj);
-    if( zExtra ){
-      *pData->pzErrMsg = sqlite3MAppendf(db, *pData->pzErrMsg, 
-                                 "%s - %s", *pData->pzErrMsg, zExtra);
-    }
+    z = sqlite3_mprintf("malformed database schema (%s)", zObj);
+    if( z && zExtra ) z = sqlite3_mprintf("%z - %s", z, zExtra);
+    sqlite3DbFree(db, *pData->pzErrMsg);
+    *pData->pzErrMsg = z;
+    if( z==0 ) db->mallocFailed = 1;
   }
   pData->rc = db->mallocFailed ? SQLITE_NOMEM : SQLITE_CORRUPT_BKPT;
 }
@@ -105795,7 +106951,7 @@ static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
   if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
     rc = sqlite3BtreeBeginTrans(pDb->pBt, 0);
     if( rc!=SQLITE_OK ){
-      sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));
+      sqlite3SetString(pzErrMsg, db, sqlite3ErrStr(rc));
       goto initone_error_out;
     }
     openedTransaction = 1;
@@ -106479,6 +107635,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_prepare16_v2(
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 */
+/* #include "sqliteInt.h" */
 
 /*
 ** Trace output macros
@@ -106487,7 +107644,8 @@ SQLITE_API int SQLITE_STDCALL sqlite3_prepare16_v2(
 /***/ int sqlite3SelectTrace = 0;
 # define SELECTTRACE(K,P,S,X)  \
   if(sqlite3SelectTrace&(K))   \
-    sqlite3DebugPrintf("%*s%s.%p: ",(P)->nSelectIndent*2-2,"",(S)->zSelName,(S)),\
+    sqlite3DebugPrintf("%*s%s.%p: ",(P)->nSelectIndent*2-2,"",\
+        (S)->zSelName,(S)),\
     sqlite3DebugPrintf X
 #else
 # define SELECTTRACE(K,P,S,X)
@@ -106831,6 +107989,12 @@ static void setJoinExpr(Expr *p, int iTable){
     assert( !ExprHasProperty(p, EP_TokenOnly|EP_Reduced) );
     ExprSetVVAProperty(p, EP_NoReduce);
     p->iRightJoinTable = (i16)iTable;
+    if( p->op==TK_FUNCTION && p->x.pList ){
+      int i;
+      for(i=0; i<p->x.pList->nExpr; i++){
+        setJoinExpr(p->x.pList->a[i].pExpr, iTable);
+      }
+    }
     setJoinExpr(p->pLeft, iTable);
     p = p->pRight;
   } 
@@ -107179,8 +108343,13 @@ static void selectInnerLoop(
     /* If the destination is an EXISTS(...) expression, the actual
     ** values returned by the SELECT are not required.
     */
-    sqlite3ExprCodeExprList(pParse, pEList, regResult,
-                  (eDest==SRT_Output||eDest==SRT_Coroutine)?SQLITE_ECEL_DUP:0);
+    u8 ecelFlags;
+    if( eDest==SRT_Mem || eDest==SRT_Output || eDest==SRT_Coroutine ){
+      ecelFlags = SQLITE_ECEL_DUP;
+    }else{
+      ecelFlags = 0;
+    }
+    sqlite3ExprCodeExprList(pParse, pEList, regResult, ecelFlags);
   }
 
   /* If the DISTINCT keyword was present on the SELECT statement
@@ -107235,7 +108404,8 @@ static void selectInnerLoop(
 
       default: {
         assert( pDistinct->eTnctType==WHERE_DISTINCT_UNORDERED );
-        codeDistinct(pParse, pDistinct->tabTnct, iContinue, nResultCol, regResult);
+        codeDistinct(pParse, pDistinct->tabTnct, iContinue, nResultCol,
+                     regResult);
         break;
       }
     }
@@ -107277,6 +108447,8 @@ static void selectInnerLoop(
       int r1 = sqlite3GetTempRange(pParse, nPrefixReg+1);
       testcase( eDest==SRT_Table );
       testcase( eDest==SRT_EphemTab );
+      testcase( eDest==SRT_Fifo );
+      testcase( eDest==SRT_DistFifo );
       sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1+nPrefixReg);
 #ifndef SQLITE_OMIT_CTE
       if( eDest==SRT_DistFifo ){
@@ -107286,7 +108458,8 @@ static void selectInnerLoop(
         ** current row to the index and proceed with writing it to the
         ** output table as well.  */
         int addr = sqlite3VdbeCurrentAddr(v) + 4;
-        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0); VdbeCoverage(v);
+        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0);
+        VdbeCoverage(v);
         sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r1);
         assert( pSort==0 );
       }
@@ -107532,7 +108705,6 @@ static KeyInfo *keyInfoFromExprList(
   return pInfo;
 }
 
-#ifndef SQLITE_OMIT_COMPOUND_SELECT
 /*
 ** Name of the connection operator, used for error messages.
 */
@@ -107546,7 +108718,6 @@ static const char *selectOpName(int id){
   }
   return z;
 }
-#endif /* SQLITE_OMIT_COMPOUND_SELECT */
 
 #ifndef SQLITE_OMIT_EXPLAIN
 /*
@@ -107692,10 +108863,7 @@ static void generateSortTail(
     VdbeComment((v, "%s", aOutEx[i].zName ? aOutEx[i].zName : aOutEx[i].zSpan));
   }
   switch( eDest ){
-    case SRT_Table:
     case SRT_EphemTab: {
-      testcase( eDest==SRT_Table );
-      testcase( eDest==SRT_EphemTab );
       sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);
       sqlite3VdbeAddOp3(v, OP_Insert, iParm, regRow, regRowid);
       sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
@@ -107772,28 +108940,27 @@ static void generateSortTail(
 */
 #ifdef SQLITE_ENABLE_COLUMN_METADATA
 # define columnType(A,B,C,D,E,F) columnTypeImpl(A,B,C,D,E,F)
+#else /* if !defined(SQLITE_ENABLE_COLUMN_METADATA) */
+# define columnType(A,B,C,D,E,F) columnTypeImpl(A,B,F)
+#endif
 static const char *columnTypeImpl(
   NameContext *pNC, 
   Expr *pExpr,
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
   const char **pzOrigDb,
   const char **pzOrigTab,
   const char **pzOrigCol,
+#endif
   u8 *pEstWidth
 ){
-  char const *zOrigDb = 0;
-  char const *zOrigTab = 0;
-  char const *zOrigCol = 0;
-#else /* if !defined(SQLITE_ENABLE_COLUMN_METADATA) */
-# define columnType(A,B,C,D,E,F) columnTypeImpl(A,B,F)
-static const char *columnTypeImpl(
-  NameContext *pNC, 
-  Expr *pExpr,
-  u8 *pEstWidth
-){
-#endif /* !defined(SQLITE_ENABLE_COLUMN_METADATA) */
   char const *zType = 0;
   int j;
   u8 estWidth = 1;
+#ifdef SQLITE_ENABLE_COLUMN_METADATA
+  char const *zOrigDb = 0;
+  char const *zOrigTab = 0;
+  char const *zOrigCol = 0;
+#endif
 
   if( NEVER(pExpr==0) || pNC->pSrcList==0 ) return 0;
   switch( pExpr->op ){
@@ -107846,10 +109013,13 @@ static const char *columnTypeImpl(
         ** of the SELECT statement. Return the declaration type and origin
         ** data for the result-set column of the sub-select.
         */
-        if( iCol>=0 && iCol<pS->pEList->nExpr ){
+        if( iCol>=0 && ALWAYS(iCol<pS->pEList->nExpr) ){
           /* If iCol is less than zero, then the expression requests the
           ** rowid of the sub-select or view. This expression is legal (see 
           ** test case misc2.2.2) - it always evaluates to NULL.
+          **
+          ** The ALWAYS() is because iCol>=pS->pEList->nExpr will have been
+          ** caught already by name resolution.
           */
           NameContext sNC;
           Expr *p = pS->pEList->a[iCol].pExpr;
@@ -108167,11 +109337,12 @@ static void selectAddColumnTypeAndCollation(
   for(i=0, pCol=pTab->aCol; i<pTab->nCol; i++, pCol++){
     p = a[i].pExpr;
     if( pCol->zType==0 ){
-      pCol->zType = sqlite3DbStrDup(db, columnType(&sNC, p,0,0,0, &pCol->szEst));
+      pCol->zType = sqlite3DbStrDup(db, 
+                        columnType(&sNC, p,0,0,0, &pCol->szEst));
     }
     szAll += pCol->szEst;
     pCol->affinity = sqlite3ExprAffinity(p);
-    if( pCol->affinity==0 ) pCol->affinity = SQLITE_AFF_NONE;
+    if( pCol->affinity==0 ) pCol->affinity = SQLITE_AFF_BLOB;
     pColl = sqlite3ExprCollSeq(pParse, p);
     if( pColl && pCol->zColl==0 ){
       pCol->zColl = sqlite3DbStrDup(db, pColl->zName);
@@ -108327,7 +109498,10 @@ static CollSeq *multiSelectCollSeq(Parse *pParse, Select *p, int iCol){
     pRet = 0;
   }
   assert( iCol>=0 );
-  if( pRet==0 && iCol<p->pEList->nExpr ){
+  /* iCol must be less than p->pEList->nExpr.  Otherwise an error would
+  ** have been thrown during name resolution and we would not have gotten
+  ** this far */
+  if( pRet==0 && ALWAYS(iCol<p->pEList->nExpr) ){
     pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
   }
   return pRet;
@@ -108517,10 +109691,14 @@ static void generateWithRecursiveQuery(
   /* Execute the recursive SELECT taking the single row in Current as
   ** the value for the recursive-table. Store the results in the Queue.
   */
-  p->pPrior = 0;
-  sqlite3Select(pParse, p, &destQueue);
-  assert( p->pPrior==0 );
-  p->pPrior = pSetup;
+  if( p->selFlags & SF_Aggregate ){
+    sqlite3ErrorMsg(pParse, "recursive aggregate queries not supported");
+  }else{
+    p->pPrior = 0;
+    sqlite3Select(pParse, p, &destQueue);
+    assert( p->pPrior==0 );
+    p->pPrior = pSetup;
+  }
 
   /* Keep running the loop until the Queue is empty */
   sqlite3VdbeAddOp2(v, OP_Goto, 0, addrTop);
@@ -108542,19 +109720,6 @@ static int multiSelectOrderBy(
   SelectDest *pDest     /* What to do with query results */
 );
 
-/*
-** Error message for when two or more terms of a compound select have different
-** size result sets.
-*/
-static void selectWrongNumTermsError(Parse *pParse, Select *p){
-  if( p->selFlags & SF_Values ){
-    sqlite3ErrorMsg(pParse, "all VALUES must have the same number of terms");
-  }else{
-    sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
-      " do not have the same number of result columns", selectOpName(p->op));
-  }
-}
-
 /*
 ** Handle the special case of a compound-select that originates from a
 ** VALUES clause.  By handling this as a special case, we avoid deep
@@ -108572,7 +109737,6 @@ static int multiSelectValues(
   SelectDest *pDest     /* What to do with query results */
 ){
   Select *pPrior;
-  int nExpr = p->pEList->nExpr;
   int nRow = 1;
   int rc = 0;
   assert( p->selFlags & SF_MultiValue );
@@ -108581,10 +109745,7 @@ static int multiSelectValues(
     assert( p->op==TK_ALL || (p->op==TK_SELECT && p->pPrior==0) );
     assert( p->pLimit==0 );
     assert( p->pOffset==0 );
-    if( p->pEList->nExpr!=nExpr ){
-      selectWrongNumTermsError(pParse, p);
-      return 1;
-    }
+    assert( p->pNext==0 || p->pEList->nExpr==p->pNext->pEList->nExpr );
     if( p->pPrior==0 ) break;
     assert( p->pPrior->pNext==p );
     p = p->pPrior;
@@ -108693,11 +109854,7 @@ static int multiSelect(
   ** in their result sets.
   */
   assert( p->pEList && pPrior->pEList );
-  if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
-    selectWrongNumTermsError(pParse, p);
-    rc = 1;
-    goto multi_select_end;
-  }
+  assert( p->pEList->nExpr==pPrior->pEList->nExpr );
 
 #ifndef SQLITE_OMIT_CTE
   if( p->selFlags & SF_Recursive ){
@@ -108989,6 +110146,19 @@ multi_select_end:
 }
 #endif /* SQLITE_OMIT_COMPOUND_SELECT */
 
+/*
+** Error message for when two or more terms of a compound select have different
+** size result sets.
+*/
+SQLITE_PRIVATE void sqlite3SelectWrongNumTermsError(Parse *pParse, Select *p){
+  if( p->selFlags & SF_Values ){
+    sqlite3ErrorMsg(pParse, "all VALUES must have the same number of terms");
+  }else{
+    sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
+      " do not have the same number of result columns", selectOpName(p->op));
+  }
+}
+
 /*
 ** Code an output subroutine for a coroutine implementation of a
 ** SELECT statment.
@@ -109044,15 +110214,14 @@ static int generateOutputSubroutine(
   */
   codeOffset(v, p->iOffset, iContinue);
 
+  assert( pDest->eDest!=SRT_Exists );
+  assert( pDest->eDest!=SRT_Table );
   switch( pDest->eDest ){
     /* Store the result as data using a unique key.
     */
-    case SRT_Table:
     case SRT_EphemTab: {
       int r1 = sqlite3GetTempReg(pParse);
       int r2 = sqlite3GetTempReg(pParse);
-      testcase( pDest->eDest==SRT_Table );
-      testcase( pDest->eDest==SRT_EphemTab );
       sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iSdst, pIn->nSdst, r1);
       sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iSDParm, r2);
       sqlite3VdbeAddOp3(v, OP_Insert, pDest->iSDParm, r1, r2);
@@ -109080,16 +110249,6 @@ static int generateOutputSubroutine(
       break;
     }
 
-#if 0  /* Never occurs on an ORDER BY query */
-    /* If any row exist in the result set, record that fact and abort.
-    */
-    case SRT_Exists: {
-      sqlite3VdbeAddOp2(v, OP_Integer, 1, pDest->iSDParm);
-      /* The LIMIT clause will terminate the loop for us */
-      break;
-    }
-#endif
-
     /* If this is a scalar select that is part of an expression, then
     ** store the results in the appropriate memory cell and break out
     ** of the scan loop.
@@ -109327,9 +110486,7 @@ static int multiSelectOrderBy(
     struct ExprList_item *pItem;
     for(i=0, pItem=pOrderBy->a; i<nOrderBy; i++, pItem++){
       assert( pItem->u.x.iOrderByCol>0 );
-      /* assert( pItem->u.x.iOrderByCol<=p->pEList->nExpr ) is also true
-      ** but only for well-formed SELECT statements. */
-      testcase( pItem->u.x.iOrderByCol > p->pEList->nExpr );
+      assert( pItem->u.x.iOrderByCol<=p->pEList->nExpr );
       aPermute[i] = pItem->u.x.iOrderByCol - 1;
     }
     pKeyMerge = multiSelectOrderByKeyInfo(pParse, p, 1);
@@ -109688,8 +110845,8 @@ static void substSelect(
 **
 **  (**)  Restriction (10) was removed from the code on 2005-02-05 but we
 **        accidently carried the comment forward until 2014-09-15.  Original
-**        text: "The subquery does not use aggregates or the outer query does not
-**        use LIMIT."
+**        text: "The subquery does not use aggregates or the outer query 
+**        does not use LIMIT."
 **
 **  (11)  The subquery and the outer query do not both have ORDER BY clauses.
 **
@@ -109899,10 +111056,10 @@ static int flattenSubquery(
       testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
       testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
       assert( pSub->pSrc!=0 );
+      assert( pSub->pEList->nExpr==pSub1->pEList->nExpr );
       if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
        || (pSub1->pPrior && pSub1->op!=TK_ALL) 
        || pSub1->pSrc->nSrc<1
-       || pSub->pEList->nExpr!=pSub1->pEList->nExpr
       ){
         return 0;
       }
@@ -110182,7 +111339,7 @@ static int flattenSubquery(
 
 #if SELECTTRACE_ENABLED
   if( sqlite3SelectTrace & 0x100 ){
-    sqlite3DebugPrintf("After flattening:\n");
+    SELECTTRACE(0x100,pParse,p,("After flattening:\n"));
     sqlite3TreeViewSelect(0, p, 0);
   }
 #endif
@@ -110191,6 +111348,73 @@ static int flattenSubquery(
 }
 #endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
 
+
+
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+/*
+** Make copies of relevant WHERE clause terms of the outer query into
+** the WHERE clause of subquery.  Example:
+**
+**    SELECT * FROM (SELECT a AS x, c-d AS y FROM t1) WHERE x=5 AND y=10;
+**
+** Transformed into:
+**
+**    SELECT * FROM (SELECT a AS x, c-d AS y FROM t1 WHERE a=5 AND c-d=10)
+**     WHERE x=5 AND y=10;
+**
+** The hope is that the terms added to the inner query will make it more
+** efficient.
+**
+** Do not attempt this optimization if:
+**
+**   (1) The inner query is an aggregate.  (In that case, we'd really want
+**       to copy the outer WHERE-clause terms onto the HAVING clause of the
+**       inner query.  But they probably won't help there so do not bother.)
+**
+**   (2) The inner query is the recursive part of a common table expression.
+**
+**   (3) The inner query has a LIMIT clause (since the changes to the WHERE
+**       close would change the meaning of the LIMIT).
+**
+**   (4) The inner query is the right operand of a LEFT JOIN.  (The caller
+**       enforces this restriction since this routine does not have enough
+**       information to know.)
+**
+** Return 0 if no changes are made and non-zero if one or more WHERE clause
+** terms are duplicated into the subquery.
+*/
+static int pushDownWhereTerms(
+  sqlite3 *db,          /* The database connection (for malloc()) */
+  Select *pSubq,        /* The subquery whose WHERE clause is to be augmented */
+  Expr *pWhere,         /* The WHERE clause of the outer query */
+  int iCursor           /* Cursor number of the subquery */
+){
+  Expr *pNew;
+  int nChng = 0;
+  if( pWhere==0 ) return 0;
+  if( (pSubq->selFlags & (SF_Aggregate|SF_Recursive))!=0 ){
+     return 0; /* restrictions (1) and (2) */
+  }
+  if( pSubq->pLimit!=0 ){
+     return 0; /* restriction (3) */
+  }
+  while( pWhere->op==TK_AND ){
+    nChng += pushDownWhereTerms(db, pSubq, pWhere->pRight, iCursor);
+    pWhere = pWhere->pLeft;
+  }
+  if( sqlite3ExprIsTableConstant(pWhere, iCursor) ){
+    nChng++;
+    while( pSubq ){
+      pNew = sqlite3ExprDup(db, pWhere, 0);
+      pNew = substExpr(db, pNew, iCursor, pSubq->pEList);
+      pSubq->pWhere = sqlite3ExprAnd(db, pSubq->pWhere, pNew);
+      pSubq = pSubq->pPrior;
+    }
+  }
+  return nChng;
+}
+#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
+
 /*
 ** Based on the contents of the AggInfo structure indicated by the first
 ** argument, this function checks if the following are true:
@@ -110274,16 +111498,16 @@ static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
 ** pFrom->pIndex and return SQLITE_OK.
 */
 SQLITE_PRIVATE int sqlite3IndexedByLookup(Parse *pParse, struct SrcList_item *pFrom){
-  if( pFrom->pTab && pFrom->zIndex ){
+  if( pFrom->pTab && pFrom->zIndexedBy ){
     Table *pTab = pFrom->pTab;
-    char *zIndex = pFrom->zIndex;
+    char *zIndexedBy = pFrom->zIndexedBy;
     Index *pIdx;
     for(pIdx=pTab->pIndex; 
-        pIdx && sqlite3StrICmp(pIdx->zName, zIndex); 
+        pIdx && sqlite3StrICmp(pIdx->zName, zIndexedBy); 
         pIdx=pIdx->pNext
     );
     if( !pIdx ){
-      sqlite3ErrorMsg(pParse, "no such index: %s", zIndex, 0);
+      sqlite3ErrorMsg(pParse, "no such index: %s", zIndexedBy, 0);
       pParse->checkSchema = 1;
       return SQLITE_ERROR;
     }
@@ -110464,7 +111688,7 @@ static int withExpand(
     pTab->zName = sqlite3DbStrDup(db, pCte->zName);
     pTab->iPKey = -1;
     pTab->nRowLogEst = 200; assert( 200==sqlite3LogEst(1048576) );
-    pTab->tabFlags |= TF_Ephemeral;
+    pTab->tabFlags |= TF_Ephemeral | TF_NoVisibleRowid;
     pFrom->pSelect = sqlite3SelectDup(db, pCte->pSelect, 0);
     if( db->mallocFailed ) return SQLITE_NOMEM;
     assert( pFrom->pSelect );
@@ -110709,13 +111933,6 @@ static int selectExpander(Walker *pWalker, Select *p){
     int longNames = (flags & SQLITE_FullColNames)!=0
                       && (flags & SQLITE_ShortColNames)==0;
 
-    /* When processing FROM-clause subqueries, it is always the case
-    ** that full_column_names=OFF and short_column_names=ON.  The
-    ** sqlite3ResultSetOfSelect() routine makes it so. */
-    assert( (p->selFlags & SF_NestedFrom)==0
-          || ((flags & SQLITE_FullColNames)==0 &&
-              (flags & SQLITE_ShortColNames)!=0) );
-
     for(k=0; k<pEList->nExpr; k++){
       pE = a[k].pExpr;
       pRight = pE->pRight;
@@ -111094,7 +112311,7 @@ static void updateAccumulator(Parse *pParse, AggInfo *pAggInfo){
       if( regHit==0 && pAggInfo->nAccumulator ) regHit = ++pParse->nMem;
       sqlite3VdbeAddOp4(v, OP_CollSeq, regHit, 0, 0, (char *)pColl, P4_COLLSEQ);
     }
-    sqlite3VdbeAddOp4(v, OP_AggStep, 0, regAgg, pF->iMem,
+    sqlite3VdbeAddOp4(v, OP_AggStep0, 0, regAgg, pF->iMem,
                       (void*)pF->pFunc, P4_FUNCDEF);
     sqlite3VdbeChangeP5(v, (u8)nArg);
     sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
@@ -111177,7 +112394,7 @@ SQLITE_PRIVATE int sqlite3Select(
   WhereInfo *pWInfo;     /* Return from sqlite3WhereBegin() */
   Vdbe *v;               /* The virtual machine under construction */
   int isAgg;             /* True for select lists like "count(*)" */
-  ExprList *pEList;      /* List of columns to extract. */
+  ExprList *pEList = 0;  /* List of columns to extract. */
   SrcList *pTabList;     /* List of tables to select from */
   Expr *pWhere;          /* The WHERE clause.  May be NULL */
   ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
@@ -111227,12 +112444,11 @@ SQLITE_PRIVATE int sqlite3Select(
   memset(&sSort, 0, sizeof(sSort));
   sSort.pOrderBy = p->pOrderBy;
   pTabList = p->pSrc;
-  pEList = p->pEList;
   if( pParse->nErr || db->mallocFailed ){
     goto select_end;
   }
+  assert( p->pEList!=0 );
   isAgg = (p->selFlags & SF_Aggregate)!=0;
-  assert( pEList!=0 );
 #if SELECTTRACE_ENABLED
   if( sqlite3SelectTrace & 0x100 ){
     SELECTTRACE(0x100,pParse,p, ("after name resolution:\n"));
@@ -111241,29 +112457,67 @@ SQLITE_PRIVATE int sqlite3Select(
 #endif
 
 
-  /* Begin generating code.
-  */
-  v = sqlite3GetVdbe(pParse);
-  if( v==0 ) goto select_end;
-
   /* If writing to memory or generating a set
   ** only a single column may be output.
   */
 #ifndef SQLITE_OMIT_SUBQUERY
-  if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
+  if( checkForMultiColumnSelectError(pParse, pDest, p->pEList->nExpr) ){
     goto select_end;
   }
 #endif
 
-  /* Generate code for all sub-queries in the FROM clause
+  /* Try to flatten subqueries in the FROM clause up into the main query
   */
 #if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
   for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
     struct SrcList_item *pItem = &pTabList->a[i];
-    SelectDest dest;
     Select *pSub = pItem->pSelect;
     int isAggSub;
+    if( pSub==0 ) continue;
+    isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
+    if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
+      /* This subquery can be absorbed into its parent. */
+      if( isAggSub ){
+        isAgg = 1;
+        p->selFlags |= SF_Aggregate;
+      }
+      i = -1;
+    }
+    pTabList = p->pSrc;
+    if( db->mallocFailed ) goto select_end;
+    if( !IgnorableOrderby(pDest) ){
+      sSort.pOrderBy = p->pOrderBy;
+    }
+  }
+#endif
+
+  /* Get a pointer the VDBE under construction, allocating a new VDBE if one
+  ** does not already exist */
+  v = sqlite3GetVdbe(pParse);
+  if( v==0 ) goto select_end;
 
+#ifndef SQLITE_OMIT_COMPOUND_SELECT
+  /* Handle compound SELECT statements using the separate multiSelect()
+  ** procedure.
+  */
+  if( p->pPrior ){
+    rc = multiSelect(pParse, p, pDest);
+    explainSetInteger(pParse->iSelectId, iRestoreSelectId);
+#if SELECTTRACE_ENABLED
+    SELECTTRACE(1,pParse,p,("end compound-select processing\n"));
+    pParse->nSelectIndent--;
+#endif
+    return rc;
+  }
+#endif
+
+  /* Generate code for all sub-queries in the FROM clause
+  */
+#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
+  for(i=0; i<pTabList->nSrc; i++){
+    struct SrcList_item *pItem = &pTabList->a[i];
+    SelectDest dest;
+    Select *pSub = pItem->pSelect;
     if( pSub==0 ) continue;
 
     /* Sometimes the code for a subquery will be generated more than
@@ -111288,16 +112542,25 @@ SQLITE_PRIVATE int sqlite3Select(
     */
     pParse->nHeight += sqlite3SelectExprHeight(p);
 
-    isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
-    if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
-      /* This subquery can be absorbed into its parent. */
-      if( isAggSub ){
-        isAgg = 1;
-        p->selFlags |= SF_Aggregate;
+    /* Make copies of constant WHERE-clause terms in the outer query down
+    ** inside the subquery.  This can help the subquery to run more efficiently.
+    */
+    if( (pItem->jointype & JT_OUTER)==0
+     && pushDownWhereTerms(db, pSub, p->pWhere, pItem->iCursor)
+    ){
+#if SELECTTRACE_ENABLED
+      if( sqlite3SelectTrace & 0x100 ){
+        SELECTTRACE(0x100,pParse,p,("After WHERE-clause push-down:\n"));
+        sqlite3TreeViewSelect(0, p, 0);
       }
-      i = -1;
-    }else if( pTabList->nSrc==1
-           && OptimizationEnabled(db, SQLITE_SubqCoroutine)
+#endif
+    }
+
+    /* Generate code to implement the subquery
+    */
+    if( pTabList->nSrc==1
+     && (p->selFlags & SF_All)==0
+     && OptimizationEnabled(db, SQLITE_SubqCoroutine)
     ){
       /* Implement a co-routine that will return a single row of the result
       ** set on each invocation.
@@ -111348,33 +112611,23 @@ SQLITE_PRIVATE int sqlite3Select(
       sqlite3VdbeChangeP1(v, topAddr, retAddr);
       sqlite3ClearTempRegCache(pParse);
     }
-    if( /*pParse->nErr ||*/ db->mallocFailed ){
-      goto select_end;
-    }
+    if( db->mallocFailed ) goto select_end;
     pParse->nHeight -= sqlite3SelectExprHeight(p);
-    pTabList = p->pSrc;
-    if( !IgnorableOrderby(pDest) ){
-      sSort.pOrderBy = p->pOrderBy;
-    }
   }
-  pEList = p->pEList;
 #endif
+
+  /* Various elements of the SELECT copied into local variables for
+  ** convenience */
+  pEList = p->pEList;
   pWhere = p->pWhere;
   pGroupBy = p->pGroupBy;
   pHaving = p->pHaving;
   sDistinct.isTnct = (p->selFlags & SF_Distinct)!=0;
 
-#ifndef SQLITE_OMIT_COMPOUND_SELECT
-  /* If there is are a sequence of queries, do the earlier ones first.
-  */
-  if( p->pPrior ){
-    rc = multiSelect(pParse, p, pDest);
-    explainSetInteger(pParse->iSelectId, iRestoreSelectId);
 #if SELECTTRACE_ENABLED
-    SELECTTRACE(1,pParse,p,("end compound-select processing\n"));
-    pParse->nSelectIndent--;
-#endif
-    return rc;
+  if( sqlite3SelectTrace & 0x400 ){
+    SELECTTRACE(0x400,pParse,p,("After all FROM-clause analysis:\n"));
+    sqlite3TreeViewSelect(0, p, 0);
   }
 #endif
 
@@ -111394,23 +112647,23 @@ SQLITE_PRIVATE int sqlite3Select(
   ** BY and DISTINCT, and an index or separate temp-table for the other.
   */
   if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct 
-   && sqlite3ExprListCompare(sSort.pOrderBy, p->pEList, -1)==0
+   && sqlite3ExprListCompare(sSort.pOrderBy, pEList, -1)==0
   ){
     p->selFlags &= ~SF_Distinct;
-    p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
-    pGroupBy = p->pGroupBy;
+    pGroupBy = p->pGroupBy = sqlite3ExprListDup(db, pEList, 0);
     /* Notice that even thought SF_Distinct has been cleared from p->selFlags,
     ** the sDistinct.isTnct is still set.  Hence, isTnct represents the
     ** original setting of the SF_Distinct flag, not the current setting */
     assert( sDistinct.isTnct );
   }
 
-  /* If there is an ORDER BY clause, then this sorting
-  ** index might end up being unused if the data can be 
-  ** extracted in pre-sorted order.  If that is the case, then the
-  ** OP_OpenEphemeral instruction will be changed to an OP_Noop once
-  ** we figure out that the sorting index is not needed.  The addrSortIndex
-  ** variable is used to facilitate that change.
+  /* If there is an ORDER BY clause, then create an ephemeral index to
+  ** do the sorting.  But this sorting ephemeral index might end up
+  ** being unused if the data can be extracted in pre-sorted order.
+  ** If that is the case, then the OP_OpenEphemeral instruction will be
+  ** changed to an OP_Noop once we figure out that the sorting index is
+  ** not needed.  The sSort.addrSortIndex variable is used to facilitate
+  ** that change.
   */
   if( sSort.pOrderBy ){
     KeyInfo *pKeyInfo;
@@ -111441,14 +112694,14 @@ SQLITE_PRIVATE int sqlite3Select(
     sSort.sortFlags |= SORTFLAG_UseSorter;
   }
 
-  /* Open a virtual index to use for the distinct set.
+  /* Open an ephemeral index to use for the distinct set.
   */
   if( p->selFlags & SF_Distinct ){
     sDistinct.tabTnct = pParse->nTab++;
     sDistinct.addrTnct = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
-                                sDistinct.tabTnct, 0, 0,
-                                (char*)keyInfoFromExprList(pParse, p->pEList,0,0),
-                                P4_KEYINFO);
+                             sDistinct.tabTnct, 0, 0,
+                             (char*)keyInfoFromExprList(pParse, p->pEList,0,0),
+                             P4_KEYINFO);
     sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
     sDistinct.eTnctType = WHERE_DISTINCT_UNORDERED;
   }else{
@@ -111526,11 +112779,10 @@ SQLITE_PRIVATE int sqlite3Select(
       p->nSelectRow = 1;
     }
 
-
     /* If there is both a GROUP BY and an ORDER BY clause and they are
     ** identical, then it may be possible to disable the ORDER BY clause 
     ** on the grounds that the GROUP BY will cause elements to come out 
-    ** in the correct order. It also may not - the GROUP BY may use a
+    ** in the correct order. It also may not - the GROUP BY might use a
     ** database index that causes rows to be grouped together as required
     ** but not actually sorted. Either way, record the fact that the
     ** ORDER BY and GROUP BY clauses are the same by setting the orderByGrp
@@ -111708,7 +112960,8 @@ SQLITE_PRIVATE int sqlite3Select(
       addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
       sqlite3ExprCacheClear(pParse);
       if( groupBySort ){
-        sqlite3VdbeAddOp3(v, OP_SorterData, sAggInfo.sortingIdx, sortOut,sortPTab);
+        sqlite3VdbeAddOp3(v, OP_SorterData, sAggInfo.sortingIdx,
+                          sortOut, sortPTab);
       }
       for(j=0; j<pGroupBy->nExpr; j++){
         if( groupBySort ){
@@ -111780,7 +113033,8 @@ SQLITE_PRIVATE int sqlite3Select(
       sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
       sqlite3VdbeResolveLabel(v, addrOutputRow);
       addrOutputRow = sqlite3VdbeCurrentAddr(v);
-      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2); VdbeCoverage(v);
+      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
+      VdbeCoverage(v);
       VdbeComment((v, "Groupby result generator entry point"));
       sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
       finalizeAggFunctions(pParse, &sAggInfo);
@@ -111944,7 +113198,8 @@ SQLITE_PRIVATE int sqlite3Select(
   ** and send them to the callback one by one.
   */
   if( sSort.pOrderBy ){
-    explainTempTable(pParse, sSort.nOBSat>0 ? "RIGHT PART OF ORDER BY":"ORDER BY");
+    explainTempTable(pParse,
+                     sSort.nOBSat>0 ? "RIGHT PART OF ORDER BY":"ORDER BY");
     generateSortTail(pParse, p, &sSort, pEList->nExpr, pDest);
   }
 
@@ -111977,100 +113232,6 @@ select_end:
   return rc;
 }
 
-#ifdef SQLITE_DEBUG
-/*
-** Generate a human-readable description of a the Select object.
-*/
-SQLITE_PRIVATE void sqlite3TreeViewSelect(TreeView *pView, const Select *p, u8 moreToFollow){
-  int n = 0;
-  pView = sqlite3TreeViewPush(pView, moreToFollow);
-  sqlite3TreeViewLine(pView, "SELECT%s%s (0x%p)",
-    ((p->selFlags & SF_Distinct) ? " DISTINCT" : ""),
-    ((p->selFlags & SF_Aggregate) ? " agg_flag" : ""), p
-  );
-  if( p->pSrc && p->pSrc->nSrc ) n++;
-  if( p->pWhere ) n++;
-  if( p->pGroupBy ) n++;
-  if( p->pHaving ) n++;
-  if( p->pOrderBy ) n++;
-  if( p->pLimit ) n++;
-  if( p->pOffset ) n++;
-  if( p->pPrior ) n++;
-  sqlite3TreeViewExprList(pView, p->pEList, (n--)>0, "result-set");
-  if( p->pSrc && p->pSrc->nSrc ){
-    int i;
-    pView = sqlite3TreeViewPush(pView, (n--)>0);
-    sqlite3TreeViewLine(pView, "FROM");
-    for(i=0; i<p->pSrc->nSrc; i++){
-      struct SrcList_item *pItem = &p->pSrc->a[i];
-      StrAccum x;
-      char zLine[100];
-      sqlite3StrAccumInit(&x, 0, zLine, sizeof(zLine), 0);
-      sqlite3XPrintf(&x, 0, "{%d,*}", pItem->iCursor);
-      if( pItem->zDatabase ){
-        sqlite3XPrintf(&x, 0, " %s.%s", pItem->zDatabase, pItem->zName);
-      }else if( pItem->zName ){
-        sqlite3XPrintf(&x, 0, " %s", pItem->zName);
-      }
-      if( pItem->pTab ){
-        sqlite3XPrintf(&x, 0, " tabname=%Q", pItem->pTab->zName);
-      }
-      if( pItem->zAlias ){
-        sqlite3XPrintf(&x, 0, " (AS %s)", pItem->zAlias);
-      }
-      if( pItem->jointype & JT_LEFT ){
-        sqlite3XPrintf(&x, 0, " LEFT-JOIN");
-      }
-      sqlite3StrAccumFinish(&x);
-      sqlite3TreeViewItem(pView, zLine, i<p->pSrc->nSrc-1); 
-      if( pItem->pSelect ){
-        sqlite3TreeViewSelect(pView, pItem->pSelect, 0);
-      }
-      sqlite3TreeViewPop(pView);
-    }
-    sqlite3TreeViewPop(pView);
-  }
-  if( p->pWhere ){
-    sqlite3TreeViewItem(pView, "WHERE", (n--)>0);
-    sqlite3TreeViewExpr(pView, p->pWhere, 0);
-    sqlite3TreeViewPop(pView);
-  }
-  if( p->pGroupBy ){
-    sqlite3TreeViewExprList(pView, p->pGroupBy, (n--)>0, "GROUPBY");
-  }
-  if( p->pHaving ){
-    sqlite3TreeViewItem(pView, "HAVING", (n--)>0);
-    sqlite3TreeViewExpr(pView, p->pHaving, 0);
-    sqlite3TreeViewPop(pView);
-  }
-  if( p->pOrderBy ){
-    sqlite3TreeViewExprList(pView, p->pOrderBy, (n--)>0, "ORDERBY");
-  }
-  if( p->pLimit ){
-    sqlite3TreeViewItem(pView, "LIMIT", (n--)>0);
-    sqlite3TreeViewExpr(pView, p->pLimit, 0);
-    sqlite3TreeViewPop(pView);
-  }
-  if( p->pOffset ){
-    sqlite3TreeViewItem(pView, "OFFSET", (n--)>0);
-    sqlite3TreeViewExpr(pView, p->pOffset, 0);
-    sqlite3TreeViewPop(pView);
-  }
-  if( p->pPrior ){
-    const char *zOp = "UNION";
-    switch( p->op ){
-      case TK_ALL:         zOp = "UNION ALL";  break;
-      case TK_INTERSECT:   zOp = "INTERSECT";  break;
-      case TK_EXCEPT:      zOp = "EXCEPT";     break;
-    }
-    sqlite3TreeViewItem(pView, zOp, (n--)>0);
-    sqlite3TreeViewSelect(pView, p->pPrior, 0);
-    sqlite3TreeViewPop(pView);
-  }
-  sqlite3TreeViewPop(pView);
-}
-#endif /* SQLITE_DEBUG */
-
 /************** End of select.c **********************************************/
 /************** Begin file table.c *******************************************/
 /*
@@ -112091,6 +113252,7 @@ SQLITE_PRIVATE void sqlite3TreeViewSelect(TreeView *pView, const Select *p, u8 m
 ** These routines are in a separate files so that they will not be linked
 ** if they are not used.
 */
+/* #include "sqliteInt.h" */
 /* #include <stdlib.h> */
 /* #include <string.h> */
 
@@ -112287,6 +113449,7 @@ SQLITE_API void SQLITE_STDCALL sqlite3_free_table(
 *************************************************************************
 ** This file contains the implementation for TRIGGERs
 */
+/* #include "sqliteInt.h" */
 
 #ifndef SQLITE_OMIT_TRIGGER
 /*
@@ -113410,6 +114573,7 @@ SQLITE_PRIVATE u32 sqlite3TriggerColmask(
 ** This file contains C code routines that are called by the parser
 ** to handle UPDATE statements.
 */
+/* #include "sqliteInt.h" */
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
 /* Forward declaration */
@@ -114140,12 +115304,10 @@ static void updateVirtualTable(
   */
   assert( v );
   ephemTab = pParse->nTab++;
-  sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
-  sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
 
   /* fill the ephemeral table 
   */
-  sqlite3SelectDestInit(&dest, SRT_Table, ephemTab);
+  sqlite3SelectDestInit(&dest, SRT_EphemTab, ephemTab);
   sqlite3Select(pParse, pSelect, &dest);
 
   /* Generate code to scan the ephemeral table and call VUpdate. */
@@ -114188,6 +115350,8 @@ static void updateVirtualTable(
 ** Most of the code in this file may be omitted by defining the
 ** SQLITE_OMIT_VACUUM macro.
 */
+/* #include "sqliteInt.h" */
+/* #include "vdbeInt.h" */
 
 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
 /*
@@ -114560,6 +115724,7 @@ end_of_vacuum:
 ** This file contains code used to help implement virtual tables.
 */
 #ifndef SQLITE_OMIT_VIRTUALTABLE
+/* #include "sqliteInt.h" */
 
 /*
 ** Before a virtual table xCreate() or xConnect() method is invoked, the
@@ -115384,8 +116549,10 @@ SQLITE_PRIVATE int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab
 static void callFinaliser(sqlite3 *db, int offset){
   int i;
   if( db->aVTrans ){
+    VTable **aVTrans = db->aVTrans;
+    db->aVTrans = 0;
     for(i=0; i<db->nVTrans; i++){
-      VTable *pVTab = db->aVTrans[i];
+      VTable *pVTab = aVTrans[i];
       sqlite3_vtab *p = pVTab->pVtab;
       if( p ){
         int (*x)(sqlite3_vtab *);
@@ -115395,9 +116562,8 @@ static void callFinaliser(sqlite3 *db, int offset){
       pVTab->iSavepoint = 0;
       sqlite3VtabUnlock(pVTab);
     }
-    sqlite3DbFree(db, db->aVTrans);
+    sqlite3DbFree(db, aVTrans);
     db->nVTrans = 0;
-    db->aVTrans = 0;
   }
 }
 
@@ -115697,9 +116863,9 @@ SQLITE_API int SQLITE_CDECL sqlite3_vtab_config(sqlite3 *db, int op, ...){
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 
 /************** End of vtab.c ************************************************/
-/************** Begin file where.c *******************************************/
+/************** Begin file wherecode.c ***************************************/
 /*
-** 2001 September 15
+** 2015-06-06
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
@@ -115710,13 +116876,15 @@ SQLITE_API int SQLITE_CDECL sqlite3_vtab_config(sqlite3 *db, int op, ...){
 **
 *************************************************************************
 ** This module contains C code that generates VDBE code used to process
-** the WHERE clause of SQL statements.  This module is responsible for
-** generating the code that loops through a table looking for applicable
-** rows.  Indices are selected and used to speed the search when doing
-** so is applicable.  Because this module is responsible for selecting
-** indices, you might also think of this module as the "query optimizer".
+** the WHERE clause of SQL statements.
+**
+** This file was split off from where.c on 2015-06-06 in order to reduce the
+** size of where.c and make it easier to edit.  This file contains the routines
+** that actually generate the bulk of the WHERE loop code.  The original where.c
+** file retains the code that does query planning and analysis.
 */
-/************** Include whereInt.h in the middle of where.c ******************/
+/* #include "sqliteInt.h" */
+/************** Include whereInt.h in the middle of wherecode.c **************/
 /************** Begin file whereInt.h ****************************************/
 /*
 ** 2013-11-12
@@ -115739,7 +116907,7 @@ SQLITE_API int SQLITE_CDECL sqlite3_vtab_config(sqlite3 *db, int op, ...){
 ** Trace output macros
 */
 #if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
-/***/ int sqlite3WhereTrace = 0;
+/***/ int sqlite3WhereTrace;
 #endif
 #if defined(SQLITE_DEBUG) \
     && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE))
@@ -115881,10 +117049,6 @@ struct WhereOrSet {
   WhereOrCost a[N_OR_COST];   /* Set of best costs */
 };
 
-
-/* Forward declaration of methods */
-static int whereLoopResize(sqlite3*, WhereLoop*, int);
-
 /*
 ** Each instance of this object holds a sequence of WhereLoop objects
 ** that implement some or all of a query plan.
@@ -116000,6 +117164,7 @@ struct WhereTerm {
 #define TERM_LIKEOPT    0x100  /* Virtual terms from the LIKE optimization */
 #define TERM_LIKECOND   0x200  /* Conditionally this LIKE operator term */
 #define TERM_LIKE       0x400  /* The original LIKE operator */
+#define TERM_IS         0x800  /* Term.pExpr is an IS operator */
 
 /*
 ** An instance of the WhereScan object is used as an iterator for locating
@@ -116091,6 +117256,11 @@ struct WhereMaskSet {
   int ix[BMS];                  /* Cursor assigned to each bit */
 };
 
+/*
+** Initialize a WhereMaskSet object
+*/
+#define initMaskSet(P)  (P)->n=0
+
 /*
 ** This object is a convenience wrapper holding all information needed
 ** to construct WhereLoop objects for a particular query.
@@ -116142,27 +117312,84 @@ struct WhereInfo {
   WhereLevel a[1];          /* Information about each nest loop in WHERE */
 };
 
+/*
+** Private interfaces - callable only by other where.c routines.
+**
+** where.c:
+*/
+SQLITE_PRIVATE Bitmask sqlite3WhereGetMask(WhereMaskSet*,int);
+SQLITE_PRIVATE WhereTerm *sqlite3WhereFindTerm(
+  WhereClause *pWC,     /* The WHERE clause to be searched */
+  int iCur,             /* Cursor number of LHS */
+  int iColumn,          /* Column number of LHS */
+  Bitmask notReady,     /* RHS must not overlap with this mask */
+  u32 op,               /* Mask of WO_xx values describing operator */
+  Index *pIdx           /* Must be compatible with this index, if not NULL */
+);
+
+/* wherecode.c: */
+#ifndef SQLITE_OMIT_EXPLAIN
+SQLITE_PRIVATE int sqlite3WhereExplainOneScan(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pTabList,              /* Table list this loop refers to */
+  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
+  int iLevel,                     /* Value for "level" column of output */
+  int iFrom,                      /* Value for "from" column of output */
+  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
+);
+#else
+# define sqlite3WhereExplainOneScan(u,v,w,x,y,z) 0
+#endif /* SQLITE_OMIT_EXPLAIN */
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+SQLITE_PRIVATE void sqlite3WhereAddScanStatus(
+  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
+  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
+  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
+  int addrExplain                 /* Address of OP_Explain (or 0) */
+);
+#else
+# define sqlite3WhereAddScanStatus(a, b, c, d) ((void)d)
+#endif
+SQLITE_PRIVATE Bitmask sqlite3WhereCodeOneLoopStart(
+  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
+  int iLevel,          /* Which level of pWInfo->a[] should be coded */
+  Bitmask notReady     /* Which tables are currently available */
+);
+
+/* whereexpr.c: */
+SQLITE_PRIVATE void sqlite3WhereClauseInit(WhereClause*,WhereInfo*);
+SQLITE_PRIVATE void sqlite3WhereClauseClear(WhereClause*);
+SQLITE_PRIVATE void sqlite3WhereSplit(WhereClause*,Expr*,u8);
+SQLITE_PRIVATE Bitmask sqlite3WhereExprUsage(WhereMaskSet*, Expr*);
+SQLITE_PRIVATE Bitmask sqlite3WhereExprListUsage(WhereMaskSet*, ExprList*);
+SQLITE_PRIVATE void sqlite3WhereExprAnalyze(SrcList*, WhereClause*);
+
+
+
+
+
 /*
 ** Bitmasks for the operators on WhereTerm objects.  These are all
 ** operators that are of interest to the query planner.  An
 ** OR-ed combination of these values can be used when searching for
 ** particular WhereTerms within a WhereClause.
 */
-#define WO_IN     0x001
-#define WO_EQ     0x002
+#define WO_IN     0x0001
+#define WO_EQ     0x0002
 #define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
 #define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
 #define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
 #define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
-#define WO_MATCH  0x040
-#define WO_ISNULL 0x080
-#define WO_OR     0x100       /* Two or more OR-connected terms */
-#define WO_AND    0x200       /* Two or more AND-connected terms */
-#define WO_EQUIV  0x400       /* Of the form A==B, both columns */
-#define WO_NOOP   0x800       /* This term does not restrict search space */
+#define WO_MATCH  0x0040
+#define WO_IS     0x0080
+#define WO_ISNULL 0x0100
+#define WO_OR     0x0200       /* Two or more OR-connected terms */
+#define WO_AND    0x0400       /* Two or more AND-connected terms */
+#define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
+#define WO_NOOP   0x1000       /* This term does not restrict search space */
 
-#define WO_ALL    0xfff       /* Mask of all possible WO_* values */
-#define WO_SINGLE 0x0ff       /* Mask of all non-compound WO_* values */
+#define WO_ALL    0x1fff       /* Mask of all possible WO_* values */
+#define WO_SINGLE 0x01ff       /* Mask of all non-compound WO_* values */
 
 /*
 ** These are definitions of bits in the WhereLoop.wsFlags field.
@@ -116190,624 +117417,1683 @@ struct WhereInfo {
 #define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
 
 /************** End of whereInt.h ********************************************/
-/************** Continuing where we left off in where.c **********************/
-
-/*
-** Return the estimated number of output rows from a WHERE clause
-*/
-SQLITE_PRIVATE u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
-  return sqlite3LogEstToInt(pWInfo->nRowOut);
-}
-
-/*
-** Return one of the WHERE_DISTINCT_xxxxx values to indicate how this
-** WHERE clause returns outputs for DISTINCT processing.
-*/
-SQLITE_PRIVATE int sqlite3WhereIsDistinct(WhereInfo *pWInfo){
-  return pWInfo->eDistinct;
-}
-
-/*
-** Return TRUE if the WHERE clause returns rows in ORDER BY order.
-** Return FALSE if the output needs to be sorted.
-*/
-SQLITE_PRIVATE int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
-  return pWInfo->nOBSat;
-}
-
-/*
-** Return the VDBE address or label to jump to in order to continue
-** immediately with the next row of a WHERE clause.
-*/
-SQLITE_PRIVATE int sqlite3WhereContinueLabel(WhereInfo *pWInfo){
-  assert( pWInfo->iContinue!=0 );
-  return pWInfo->iContinue;
-}
+/************** Continuing where we left off in wherecode.c ******************/
 
+#ifndef SQLITE_OMIT_EXPLAIN
 /*
-** Return the VDBE address or label to jump to in order to break
-** out of a WHERE loop.
+** This routine is a helper for explainIndexRange() below
+**
+** pStr holds the text of an expression that we are building up one term
+** at a time.  This routine adds a new term to the end of the expression.
+** Terms are separated by AND so add the "AND" text for second and subsequent
+** terms only.
 */
-SQLITE_PRIVATE int sqlite3WhereBreakLabel(WhereInfo *pWInfo){
-  return pWInfo->iBreak;
+static void explainAppendTerm(
+  StrAccum *pStr,             /* The text expression being built */
+  int iTerm,                  /* Index of this term.  First is zero */
+  const char *zColumn,        /* Name of the column */
+  const char *zOp             /* Name of the operator */
+){
+  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
+  sqlite3StrAccumAppendAll(pStr, zColumn);
+  sqlite3StrAccumAppend(pStr, zOp, 1);
+  sqlite3StrAccumAppend(pStr, "?", 1);
 }
 
 /*
-** Return TRUE if an UPDATE or DELETE statement can operate directly on
-** the rowids returned by a WHERE clause.  Return FALSE if doing an
-** UPDATE or DELETE might change subsequent WHERE clause results.
+** Argument pLevel describes a strategy for scanning table pTab. This 
+** function appends text to pStr that describes the subset of table
+** rows scanned by the strategy in the form of an SQL expression.
 **
-** If the ONEPASS optimization is used (if this routine returns true)
-** then also write the indices of open cursors used by ONEPASS
-** into aiCur[0] and aiCur[1].  iaCur[0] gets the cursor of the data
-** table and iaCur[1] gets the cursor used by an auxiliary index.
-** Either value may be -1, indicating that cursor is not used.
-** Any cursors returned will have been opened for writing.
+** For example, if the query:
 **
-** aiCur[0] and aiCur[1] both get -1 if the where-clause logic is
-** unable to use the ONEPASS optimization.
-*/
-SQLITE_PRIVATE int sqlite3WhereOkOnePass(WhereInfo *pWInfo, int *aiCur){
-  memcpy(aiCur, pWInfo->aiCurOnePass, sizeof(int)*2);
-  return pWInfo->okOnePass;
-}
-
-/*
-** Move the content of pSrc into pDest
-*/
-static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
-  pDest->n = pSrc->n;
-  memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
-}
-
-/*
-** Try to insert a new prerequisite/cost entry into the WhereOrSet pSet.
+**   SELECT * FROM t1 WHERE a=1 AND b>2;
 **
-** The new entry might overwrite an existing entry, or it might be
-** appended, or it might be discarded.  Do whatever is the right thing
-** so that pSet keeps the N_OR_COST best entries seen so far.
+** is run and there is an index on (a, b), then this function returns a
+** string similar to:
+**
+**   "a=? AND b>?"
 */
-static int whereOrInsert(
-  WhereOrSet *pSet,      /* The WhereOrSet to be updated */
-  Bitmask prereq,        /* Prerequisites of the new entry */
-  LogEst rRun,           /* Run-cost of the new entry */
-  LogEst nOut            /* Number of outputs for the new entry */
-){
-  u16 i;
-  WhereOrCost *p;
-  for(i=pSet->n, p=pSet->a; i>0; i--, p++){
-    if( rRun<=p->rRun && (prereq & p->prereq)==prereq ){
-      goto whereOrInsert_done;
-    }
-    if( p->rRun<=rRun && (p->prereq & prereq)==p->prereq ){
-      return 0;
+static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop, Table *pTab){
+  Index *pIndex = pLoop->u.btree.pIndex;
+  u16 nEq = pLoop->u.btree.nEq;
+  u16 nSkip = pLoop->nSkip;
+  int i, j;
+  Column *aCol = pTab->aCol;
+  i16 *aiColumn = pIndex->aiColumn;
+
+  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
+  sqlite3StrAccumAppend(pStr, " (", 2);
+  for(i=0; i<nEq; i++){
+    char *z = aiColumn[i] < 0 ? "rowid" : aCol[aiColumn[i]].zName;
+    if( i>=nSkip ){
+      explainAppendTerm(pStr, i, z, "=");
+    }else{
+      if( i ) sqlite3StrAccumAppend(pStr, " AND ", 5);
+      sqlite3XPrintf(pStr, 0, "ANY(%s)", z);
     }
   }
-  if( pSet->n<N_OR_COST ){
-    p = &pSet->a[pSet->n++];
-    p->nOut = nOut;
-  }else{
-    p = pSet->a;
-    for(i=1; i<pSet->n; i++){
-      if( p->rRun>pSet->a[i].rRun ) p = pSet->a + i;
-    }
-    if( p->rRun<=rRun ) return 0;
+
+  j = i;
+  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
+    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
+    explainAppendTerm(pStr, i++, z, ">");
   }
-whereOrInsert_done:
-  p->prereq = prereq;
-  p->rRun = rRun;
-  if( p->nOut>nOut ) p->nOut = nOut;
-  return 1;
+  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
+    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
+    explainAppendTerm(pStr, i, z, "<");
+  }
+  sqlite3StrAccumAppend(pStr, ")", 1);
 }
 
 /*
-** Initialize a preallocated WhereClause structure.
+** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
+** command, or if either SQLITE_DEBUG or SQLITE_ENABLE_STMT_SCANSTATUS was
+** defined at compile-time. If it is not a no-op, a single OP_Explain opcode 
+** is added to the output to describe the table scan strategy in pLevel.
+**
+** If an OP_Explain opcode is added to the VM, its address is returned.
+** Otherwise, if no OP_Explain is coded, zero is returned.
 */
-static void whereClauseInit(
-  WhereClause *pWC,        /* The WhereClause to be initialized */
-  WhereInfo *pWInfo        /* The WHERE processing context */
+SQLITE_PRIVATE int sqlite3WhereExplainOneScan(
+  Parse *pParse,                  /* Parse context */
+  SrcList *pTabList,              /* Table list this loop refers to */
+  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
+  int iLevel,                     /* Value for "level" column of output */
+  int iFrom,                      /* Value for "from" column of output */
+  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
 ){
-  pWC->pWInfo = pWInfo;
-  pWC->pOuter = 0;
-  pWC->nTerm = 0;
-  pWC->nSlot = ArraySize(pWC->aStatic);
-  pWC->a = pWC->aStatic;
-}
-
-/* Forward reference */
-static void whereClauseClear(WhereClause*);
+  int ret = 0;
+#if !defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_STMT_SCANSTATUS)
+  if( pParse->explain==2 )
+#endif
+  {
+    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
+    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
+    sqlite3 *db = pParse->db;     /* Database handle */
+    int iId = pParse->iSelectId;  /* Select id (left-most output column) */
+    int isSearch;                 /* True for a SEARCH. False for SCAN. */
+    WhereLoop *pLoop;             /* The controlling WhereLoop object */
+    u32 flags;                    /* Flags that describe this loop */
+    char *zMsg;                   /* Text to add to EQP output */
+    StrAccum str;                 /* EQP output string */
+    char zBuf[100];               /* Initial space for EQP output string */
 
-/*
-** Deallocate all memory associated with a WhereOrInfo object.
-*/
-static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
-  whereClauseClear(&p->wc);
-  sqlite3DbFree(db, p);
-}
+    pLoop = pLevel->pWLoop;
+    flags = pLoop->wsFlags;
+    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return 0;
 
-/*
-** Deallocate all memory associated with a WhereAndInfo object.
-*/
-static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
-  whereClauseClear(&p->wc);
-  sqlite3DbFree(db, p);
-}
+    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
+            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
+            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
 
-/*
-** Deallocate a WhereClause structure.  The WhereClause structure
-** itself is not freed.  This routine is the inverse of whereClauseInit().
-*/
-static void whereClauseClear(WhereClause *pWC){
-  int i;
-  WhereTerm *a;
-  sqlite3 *db = pWC->pWInfo->pParse->db;
-  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
-    if( a->wtFlags & TERM_DYNAMIC ){
-      sqlite3ExprDelete(db, a->pExpr);
+    sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
+    sqlite3StrAccumAppendAll(&str, isSearch ? "SEARCH" : "SCAN");
+    if( pItem->pSelect ){
+      sqlite3XPrintf(&str, 0, " SUBQUERY %d", pItem->iSelectId);
+    }else{
+      sqlite3XPrintf(&str, 0, " TABLE %s", pItem->zName);
     }
-    if( a->wtFlags & TERM_ORINFO ){
-      whereOrInfoDelete(db, a->u.pOrInfo);
-    }else if( a->wtFlags & TERM_ANDINFO ){
-      whereAndInfoDelete(db, a->u.pAndInfo);
+
+    if( pItem->zAlias ){
+      sqlite3XPrintf(&str, 0, " AS %s", pItem->zAlias);
     }
-  }
-  if( pWC->a!=pWC->aStatic ){
-    sqlite3DbFree(db, pWC->a);
-  }
-}
+    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
+      const char *zFmt = 0;
+      Index *pIdx;
 
-/*
-** Add a single new WhereTerm entry to the WhereClause object pWC.
-** The new WhereTerm object is constructed from Expr p and with wtFlags.
-** The index in pWC->a[] of the new WhereTerm is returned on success.
-** 0 is returned if the new WhereTerm could not be added due to a memory
-** allocation error.  The memory allocation failure will be recorded in
-** the db->mallocFailed flag so that higher-level functions can detect it.
-**
-** This routine will increase the size of the pWC->a[] array as necessary.
-**
-** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
-** for freeing the expression p is assumed by the WhereClause object pWC.
-** This is true even if this routine fails to allocate a new WhereTerm.
-**
-** WARNING:  This routine might reallocate the space used to store
-** WhereTerms.  All pointers to WhereTerms should be invalidated after
-** calling this routine.  Such pointers may be reinitialized by referencing
-** the pWC->a[] array.
-*/
-static int whereClauseInsert(WhereClause *pWC, Expr *p, u16 wtFlags){
-  WhereTerm *pTerm;
-  int idx;
-  testcase( wtFlags & TERM_VIRTUAL );
-  if( pWC->nTerm>=pWC->nSlot ){
-    WhereTerm *pOld = pWC->a;
-    sqlite3 *db = pWC->pWInfo->pParse->db;
-    pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
-    if( pWC->a==0 ){
-      if( wtFlags & TERM_DYNAMIC ){
-        sqlite3ExprDelete(db, p);
+      assert( pLoop->u.btree.pIndex!=0 );
+      pIdx = pLoop->u.btree.pIndex;
+      assert( !(flags&WHERE_AUTO_INDEX) || (flags&WHERE_IDX_ONLY) );
+      if( !HasRowid(pItem->pTab) && IsPrimaryKeyIndex(pIdx) ){
+        if( isSearch ){
+          zFmt = "PRIMARY KEY";
+        }
+      }else if( flags & WHERE_PARTIALIDX ){
+        zFmt = "AUTOMATIC PARTIAL COVERING INDEX";
+      }else if( flags & WHERE_AUTO_INDEX ){
+        zFmt = "AUTOMATIC COVERING INDEX";
+      }else if( flags & WHERE_IDX_ONLY ){
+        zFmt = "COVERING INDEX %s";
+      }else{
+        zFmt = "INDEX %s";
       }
-      pWC->a = pOld;
-      return 0;
+      if( zFmt ){
+        sqlite3StrAccumAppend(&str, " USING ", 7);
+        sqlite3XPrintf(&str, 0, zFmt, pIdx->zName);
+        explainIndexRange(&str, pLoop, pItem->pTab);
+      }
+    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
+      const char *zRange;
+      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
+        zRange = "(rowid=?)";
+      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
+        zRange = "(rowid>? AND rowid<?)";
+      }else if( flags&WHERE_BTM_LIMIT ){
+        zRange = "(rowid>?)";
+      }else{
+        assert( flags&WHERE_TOP_LIMIT);
+        zRange = "(rowid<?)";
+      }
+      sqlite3StrAccumAppendAll(&str, " USING INTEGER PRIMARY KEY ");
+      sqlite3StrAccumAppendAll(&str, zRange);
     }
-    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
-    if( pOld!=pWC->aStatic ){
-      sqlite3DbFree(db, pOld);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
+      sqlite3XPrintf(&str, 0, " VIRTUAL TABLE INDEX %d:%s",
+                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
     }
-    pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
-    memset(&pWC->a[pWC->nTerm], 0, sizeof(pWC->a[0])*(pWC->nSlot-pWC->nTerm));
-  }
-  pTerm = &pWC->a[idx = pWC->nTerm++];
-  if( p && ExprHasProperty(p, EP_Unlikely) ){
-    pTerm->truthProb = sqlite3LogEst(p->iTable) - 270;
-  }else{
-    pTerm->truthProb = 1;
+#endif
+#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
+    if( pLoop->nOut>=10 ){
+      sqlite3XPrintf(&str, 0, " (~%llu rows)", sqlite3LogEstToInt(pLoop->nOut));
+    }else{
+      sqlite3StrAccumAppend(&str, " (~1 row)", 9);
+    }
+#endif
+    zMsg = sqlite3StrAccumFinish(&str);
+    ret = sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg,P4_DYNAMIC);
   }
-  pTerm->pExpr = sqlite3ExprSkipCollate(p);
-  pTerm->wtFlags = wtFlags;
-  pTerm->pWC = pWC;
-  pTerm->iParent = -1;
-  return idx;
+  return ret;
 }
+#endif /* SQLITE_OMIT_EXPLAIN */
 
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
 /*
-** This routine identifies subexpressions in the WHERE clause where
-** each subexpression is separated by the AND operator or some other
-** operator specified in the op parameter.  The WhereClause structure
-** is filled with pointers to subexpressions.  For example:
-**
-**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
-**           \________/     \_______________/     \________________/
-**            slot[0]            slot[1]               slot[2]
-**
-** The original WHERE clause in pExpr is unaltered.  All this routine
-** does is make slot[] entries point to substructure within pExpr.
+** Configure the VM passed as the first argument with an
+** sqlite3_stmt_scanstatus() entry corresponding to the scan used to 
+** implement level pLvl. Argument pSrclist is a pointer to the FROM 
+** clause that the scan reads data from.
 **
-** In the previous sentence and in the diagram, "slot[]" refers to
-** the WhereClause.a[] array.  The slot[] array grows as needed to contain
-** all terms of the WHERE clause.
+** If argument addrExplain is not 0, it must be the address of an 
+** OP_Explain instruction that describes the same loop.
 */
-static void whereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
-  Expr *pE2 = sqlite3ExprSkipCollate(pExpr);
-  pWC->op = op;
-  if( pE2==0 ) return;
-  if( pE2->op!=op ){
-    whereClauseInsert(pWC, pExpr, 0);
+SQLITE_PRIVATE void sqlite3WhereAddScanStatus(
+  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
+  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
+  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
+  int addrExplain                 /* Address of OP_Explain (or 0) */
+){
+  const char *zObj = 0;
+  WhereLoop *pLoop = pLvl->pWLoop;
+  if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0  &&  pLoop->u.btree.pIndex!=0 ){
+    zObj = pLoop->u.btree.pIndex->zName;
   }else{
-    whereSplit(pWC, pE2->pLeft, op);
-    whereSplit(pWC, pE2->pRight, op);
+    zObj = pSrclist->a[pLvl->iFrom].zName;
   }
+  sqlite3VdbeScanStatus(
+      v, addrExplain, pLvl->addrBody, pLvl->addrVisit, pLoop->nOut, zObj
+  );
 }
+#endif
 
-/*
-** Initialize a WhereMaskSet object
-*/
-#define initMaskSet(P)  (P)->n=0
 
 /*
-** Return the bitmask for the given cursor number.  Return 0 if
-** iCursor is not in the set.
+** Disable a term in the WHERE clause.  Except, do not disable the term
+** if it controls a LEFT OUTER JOIN and it did not originate in the ON
+** or USING clause of that join.
+**
+** Consider the term t2.z='ok' in the following queries:
+**
+**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
+**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
+**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
+**
+** The t2.z='ok' is disabled in the in (2) because it originates
+** in the ON clause.  The term is disabled in (3) because it is not part
+** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
+**
+** Disabling a term causes that term to not be tested in the inner loop
+** of the join.  Disabling is an optimization.  When terms are satisfied
+** by indices, we disable them to prevent redundant tests in the inner
+** loop.  We would get the correct results if nothing were ever disabled,
+** but joins might run a little slower.  The trick is to disable as much
+** as we can without disabling too much.  If we disabled in (1), we'd get
+** the wrong answer.  See ticket #813.
+**
+** If all the children of a term are disabled, then that term is also
+** automatically disabled.  In this way, terms get disabled if derived
+** virtual terms are tested first.  For example:
+**
+**      x GLOB 'abc*' AND x>='abc' AND x<'acd'
+**      \___________/     \______/     \_____/
+**         parent          child1       child2
+**
+** Only the parent term was in the original WHERE clause.  The child1
+** and child2 terms were added by the LIKE optimization.  If both of
+** the virtual child terms are valid, then testing of the parent can be 
+** skipped.
+**
+** Usually the parent term is marked as TERM_CODED.  But if the parent
+** term was originally TERM_LIKE, then the parent gets TERM_LIKECOND instead.
+** The TERM_LIKECOND marking indicates that the term should be coded inside
+** a conditional such that is only evaluated on the second pass of a
+** LIKE-optimization loop, when scanning BLOBs instead of strings.
 */
-static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
-  int i;
-  assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
-  for(i=0; i<pMaskSet->n; i++){
-    if( pMaskSet->ix[i]==iCursor ){
-      return MASKBIT(i);
+static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
+  int nLoop = 0;
+  while( pTerm
+      && (pTerm->wtFlags & TERM_CODED)==0
+      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
+      && (pLevel->notReady & pTerm->prereqAll)==0
+  ){
+    if( nLoop && (pTerm->wtFlags & TERM_LIKE)!=0 ){
+      pTerm->wtFlags |= TERM_LIKECOND;
+    }else{
+      pTerm->wtFlags |= TERM_CODED;
     }
+    if( pTerm->iParent<0 ) break;
+    pTerm = &pTerm->pWC->a[pTerm->iParent];
+    pTerm->nChild--;
+    if( pTerm->nChild!=0 ) break;
+    nLoop++;
   }
-  return 0;
 }
 
 /*
-** Create a new mask for cursor iCursor.
+** Code an OP_Affinity opcode to apply the column affinity string zAff
+** to the n registers starting at base. 
 **
-** There is one cursor per table in the FROM clause.  The number of
-** tables in the FROM clause is limited by a test early in the
-** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
-** array will never overflow.
-*/
-static void createMask(WhereMaskSet *pMaskSet, int iCursor){
-  assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
-  pMaskSet->ix[pMaskSet->n++] = iCursor;
-}
-
-/*
-** These routines walk (recursively) an expression tree and generate
-** a bitmask indicating which tables are used in that expression
-** tree.
+** As an optimization, SQLITE_AFF_BLOB entries (which are no-ops) at the
+** beginning and end of zAff are ignored.  If all entries in zAff are
+** SQLITE_AFF_BLOB, then no code gets generated.
+**
+** This routine makes its own copy of zAff so that the caller is free
+** to modify zAff after this routine returns.
 */
-static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
-static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
-static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
-  Bitmask mask = 0;
-  if( p==0 ) return 0;
-  if( p->op==TK_COLUMN ){
-    mask = getMask(pMaskSet, p->iTable);
-    return mask;
+static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
+  Vdbe *v = pParse->pVdbe;
+  if( zAff==0 ){
+    assert( pParse->db->mallocFailed );
+    return;
   }
-  mask = exprTableUsage(pMaskSet, p->pRight);
-  mask |= exprTableUsage(pMaskSet, p->pLeft);
-  if( ExprHasProperty(p, EP_xIsSelect) ){
-    mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
-  }else{
-    mask |= exprListTableUsage(pMaskSet, p->x.pList);
+  assert( v!=0 );
+
+  /* Adjust base and n to skip over SQLITE_AFF_BLOB entries at the beginning
+  ** and end of the affinity string.
+  */
+  while( n>0 && zAff[0]==SQLITE_AFF_BLOB ){
+    n--;
+    base++;
+    zAff++;
   }
-  return mask;
-}
-static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
-  int i;
-  Bitmask mask = 0;
-  if( pList ){
-    for(i=0; i<pList->nExpr; i++){
-      mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
-    }
+  while( n>1 && zAff[n-1]==SQLITE_AFF_BLOB ){
+    n--;
   }
-  return mask;
-}
-static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
-  Bitmask mask = 0;
-  while( pS ){
-    SrcList *pSrc = pS->pSrc;
-    mask |= exprListTableUsage(pMaskSet, pS->pEList);
-    mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
-    mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
-    mask |= exprTableUsage(pMaskSet, pS->pWhere);
-    mask |= exprTableUsage(pMaskSet, pS->pHaving);
-    if( ALWAYS(pSrc!=0) ){
-      int i;
-      for(i=0; i<pSrc->nSrc; i++){
-        mask |= exprSelectTableUsage(pMaskSet, pSrc->a[i].pSelect);
-        mask |= exprTableUsage(pMaskSet, pSrc->a[i].pOn);
-      }
-    }
-    pS = pS->pPrior;
+
+  /* Code the OP_Affinity opcode if there is anything left to do. */
+  if( n>0 ){
+    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
+    sqlite3VdbeChangeP4(v, -1, zAff, n);
+    sqlite3ExprCacheAffinityChange(pParse, base, n);
   }
-  return mask;
 }
 
-/*
-** Return TRUE if the given operator is one of the operators that is
-** allowed for an indexable WHERE clause term.  The allowed operators are
-** "=", "<", ">", "<=", ">=", "IN", and "IS NULL"
-*/
-static int allowedOp(int op){
-  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
-  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
-  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
-  assert( TK_GE==TK_EQ+4 );
-  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
-}
 
 /*
-** Commute a comparison operator.  Expressions of the form "X op Y"
-** are converted into "Y op X".
+** Generate code for a single equality term of the WHERE clause.  An equality
+** term can be either X=expr or X IN (...).   pTerm is the term to be 
+** coded.
 **
-** If left/right precedence rules come into play when determining the
-** collating sequence, then COLLATE operators are adjusted to ensure
-** that the collating sequence does not change.  For example:
-** "Y collate NOCASE op X" becomes "X op Y" because any collation sequence on
-** the left hand side of a comparison overrides any collation sequence 
-** attached to the right. For the same reason the EP_Collate flag
-** is not commuted.
+** The current value for the constraint is left in register iReg.
+**
+** For a constraint of the form X=expr, the expression is evaluated and its
+** result is left on the stack.  For constraints of the form X IN (...)
+** this routine sets up a loop that will iterate over all values of X.
 */
-static void exprCommute(Parse *pParse, Expr *pExpr){
-  u16 expRight = (pExpr->pRight->flags & EP_Collate);
-  u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
-  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
-  if( expRight==expLeft ){
-    /* Either X and Y both have COLLATE operator or neither do */
-    if( expRight ){
-      /* Both X and Y have COLLATE operators.  Make sure X is always
-      ** used by clearing the EP_Collate flag from Y. */
-      pExpr->pRight->flags &= ~EP_Collate;
-    }else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
-      /* Neither X nor Y have COLLATE operators, but X has a non-default
-      ** collating sequence.  So add the EP_Collate marker on X to cause
-      ** it to be searched first. */
-      pExpr->pLeft->flags |= EP_Collate;
-    }
-  }
-  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
-  if( pExpr->op>=TK_GT ){
-    assert( TK_LT==TK_GT+2 );
-    assert( TK_GE==TK_LE+2 );
-    assert( TK_GT>TK_EQ );
-    assert( TK_GT<TK_LE );
-    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
-    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
-  }
-}
+static int codeEqualityTerm(
+  Parse *pParse,      /* The parsing context */
+  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
+  WhereLevel *pLevel, /* The level of the FROM clause we are working on */
+  int iEq,            /* Index of the equality term within this level */
+  int bRev,           /* True for reverse-order IN operations */
+  int iTarget         /* Attempt to leave results in this register */
+){
+  Expr *pX = pTerm->pExpr;
+  Vdbe *v = pParse->pVdbe;
+  int iReg;                  /* Register holding results */
 
-/*
-** Translate from TK_xx operator to WO_xx bitmask.
-*/
-static u16 operatorMask(int op){
-  u16 c;
-  assert( allowedOp(op) );
-  if( op==TK_IN ){
-    c = WO_IN;
-  }else if( op==TK_ISNULL ){
-    c = WO_ISNULL;
+  assert( iTarget>0 );
+  if( pX->op==TK_EQ || pX->op==TK_IS ){
+    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
+  }else if( pX->op==TK_ISNULL ){
+    iReg = iTarget;
+    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
+#ifndef SQLITE_OMIT_SUBQUERY
   }else{
-    assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
-    c = (u16)(WO_EQ<<(op-TK_EQ));
-  }
-  assert( op!=TK_ISNULL || c==WO_ISNULL );
-  assert( op!=TK_IN || c==WO_IN );
-  assert( op!=TK_EQ || c==WO_EQ );
-  assert( op!=TK_LT || c==WO_LT );
-  assert( op!=TK_LE || c==WO_LE );
-  assert( op!=TK_GT || c==WO_GT );
-  assert( op!=TK_GE || c==WO_GE );
-  return c;
-}
-
-/*
-** Advance to the next WhereTerm that matches according to the criteria
-** established when the pScan object was initialized by whereScanInit().
-** Return NULL if there are no more matching WhereTerms.
-*/
-static WhereTerm *whereScanNext(WhereScan *pScan){
-  int iCur;            /* The cursor on the LHS of the term */
-  int iColumn;         /* The column on the LHS of the term.  -1 for IPK */
-  Expr *pX;            /* An expression being tested */
-  WhereClause *pWC;    /* Shorthand for pScan->pWC */
-  WhereTerm *pTerm;    /* The term being tested */
-  int k = pScan->k;    /* Where to start scanning */
+    int eType;
+    int iTab;
+    struct InLoop *pIn;
+    WhereLoop *pLoop = pLevel->pWLoop;
 
-  while( pScan->iEquiv<=pScan->nEquiv ){
-    iCur = pScan->aEquiv[pScan->iEquiv-2];
-    iColumn = pScan->aEquiv[pScan->iEquiv-1];
-    while( (pWC = pScan->pWC)!=0 ){
-      for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
-        if( pTerm->leftCursor==iCur
-         && pTerm->u.leftColumn==iColumn
-         && (pScan->iEquiv<=2 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
-        ){
-          if( (pTerm->eOperator & WO_EQUIV)!=0
-           && pScan->nEquiv<ArraySize(pScan->aEquiv)
-          ){
-            int j;
-            pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight);
-            assert( pX->op==TK_COLUMN );
-            for(j=0; j<pScan->nEquiv; j+=2){
-              if( pScan->aEquiv[j]==pX->iTable
-               && pScan->aEquiv[j+1]==pX->iColumn ){
-                  break;
-              }
-            }
-            if( j==pScan->nEquiv ){
-              pScan->aEquiv[j] = pX->iTable;
-              pScan->aEquiv[j+1] = pX->iColumn;
-              pScan->nEquiv += 2;
-            }
-          }
-          if( (pTerm->eOperator & pScan->opMask)!=0 ){
-            /* Verify the affinity and collating sequence match */
-            if( pScan->zCollName && (pTerm->eOperator & WO_ISNULL)==0 ){
-              CollSeq *pColl;
-              Parse *pParse = pWC->pWInfo->pParse;
-              pX = pTerm->pExpr;
-              if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
-                continue;
-              }
-              assert(pX->pLeft);
-              pColl = sqlite3BinaryCompareCollSeq(pParse,
-                                                  pX->pLeft, pX->pRight);
-              if( pColl==0 ) pColl = pParse->db->pDfltColl;
-              if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
-                continue;
-              }
-            }
-            if( (pTerm->eOperator & WO_EQ)!=0
-             && (pX = pTerm->pExpr->pRight)->op==TK_COLUMN
-             && pX->iTable==pScan->aEquiv[0]
-             && pX->iColumn==pScan->aEquiv[1]
-            ){
-              continue;
-            }
-            pScan->k = k+1;
-            return pTerm;
-          }
-        }
+    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
+      && pLoop->u.btree.pIndex!=0
+      && pLoop->u.btree.pIndex->aSortOrder[iEq]
+    ){
+      testcase( iEq==0 );
+      testcase( bRev );
+      bRev = !bRev;
+    }
+    assert( pX->op==TK_IN );
+    iReg = iTarget;
+    eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0);
+    if( eType==IN_INDEX_INDEX_DESC ){
+      testcase( bRev );
+      bRev = !bRev;
+    }
+    iTab = pX->iTable;
+    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
+    VdbeCoverageIf(v, bRev);
+    VdbeCoverageIf(v, !bRev);
+    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
+    pLoop->wsFlags |= WHERE_IN_ABLE;
+    if( pLevel->u.in.nIn==0 ){
+      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
+    }
+    pLevel->u.in.nIn++;
+    pLevel->u.in.aInLoop =
+       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
+                              sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
+    pIn = pLevel->u.in.aInLoop;
+    if( pIn ){
+      pIn += pLevel->u.in.nIn - 1;
+      pIn->iCur = iTab;
+      if( eType==IN_INDEX_ROWID ){
+        pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
+      }else{
+        pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
       }
-      pScan->pWC = pScan->pWC->pOuter;
-      k = 0;
+      pIn->eEndLoopOp = bRev ? OP_PrevIfOpen : OP_NextIfOpen;
+      sqlite3VdbeAddOp1(v, OP_IsNull, iReg); VdbeCoverage(v);
+    }else{
+      pLevel->u.in.nIn = 0;
     }
-    pScan->pWC = pScan->pOrigWC;
-    k = 0;
-    pScan->iEquiv += 2;
+#endif
   }
-  return 0;
+  disableTerm(pLevel, pTerm);
+  return iReg;
 }
 
 /*
-** Initialize a WHERE clause scanner object.  Return a pointer to the
-** first match.  Return NULL if there are no matches.
+** Generate code that will evaluate all == and IN constraints for an
+** index scan.
 **
-** The scanner will be searching the WHERE clause pWC.  It will look
-** for terms of the form "X <op> <expr>" where X is column iColumn of table
-** iCur.  The <op> must be one of the operators described by opMask.
+** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
+** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
+** The index has as many as three equality constraints, but in this
+** example, the third "c" value is an inequality.  So only two 
+** constraints are coded.  This routine will generate code to evaluate
+** a==5 and b IN (1,2,3).  The current values for a and b will be stored
+** in consecutive registers and the index of the first register is returned.
 **
-** If the search is for X and the WHERE clause contains terms of the
-** form X=Y then this routine might also return terms of the form
-** "Y <op> <expr>".  The number of levels of transitivity is limited,
-** but is enough to handle most commonly occurring SQL statements.
+** In the example above nEq==2.  But this subroutine works for any value
+** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
+** The only thing it does is allocate the pLevel->iMem memory cell and
+** compute the affinity string.
 **
-** If X is not the INTEGER PRIMARY KEY then X must be compatible with
-** index pIdx.
+** The nExtraReg parameter is 0 or 1.  It is 0 if all WHERE clause constraints
+** are == or IN and are covered by the nEq.  nExtraReg is 1 if there is
+** an inequality constraint (such as the "c>=5 AND c<10" in the example) that
+** occurs after the nEq quality constraints.
+**
+** This routine allocates a range of nEq+nExtraReg memory cells and returns
+** the index of the first memory cell in that range. The code that
+** calls this routine will use that memory range to store keys for
+** start and termination conditions of the loop.
+** key value of the loop.  If one or more IN operators appear, then
+** this routine allocates an additional nEq memory cells for internal
+** use.
+**
+** Before returning, *pzAff is set to point to a buffer containing a
+** copy of the column affinity string of the index allocated using
+** sqlite3DbMalloc(). Except, entries in the copy of the string associated
+** with equality constraints that use BLOB or NONE affinity are set to
+** SQLITE_AFF_BLOB. This is to deal with SQL such as the following:
+**
+**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
+**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
+**
+** In the example above, the index on t1(a) has TEXT affinity. But since
+** the right hand side of the equality constraint (t2.b) has BLOB/NONE affinity,
+** no conversion should be attempted before using a t2.b value as part of
+** a key to search the index. Hence the first byte in the returned affinity
+** string in this example would be set to SQLITE_AFF_BLOB.
 */
-static WhereTerm *whereScanInit(
-  WhereScan *pScan,       /* The WhereScan object being initialized */
-  WhereClause *pWC,       /* The WHERE clause to be scanned */
-  int iCur,               /* Cursor to scan for */
-  int iColumn,            /* Column to scan for */
-  u32 opMask,             /* Operator(s) to scan for */
-  Index *pIdx             /* Must be compatible with this index */
+static int codeAllEqualityTerms(
+  Parse *pParse,        /* Parsing context */
+  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
+  int bRev,             /* Reverse the order of IN operators */
+  int nExtraReg,        /* Number of extra registers to allocate */
+  char **pzAff          /* OUT: Set to point to affinity string */
 ){
-  int j;
+  u16 nEq;                      /* The number of == or IN constraints to code */
+  u16 nSkip;                    /* Number of left-most columns to skip */
+  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
+  Index *pIdx;                  /* The index being used for this loop */
+  WhereTerm *pTerm;             /* A single constraint term */
+  WhereLoop *pLoop;             /* The WhereLoop object */
+  int j;                        /* Loop counter */
+  int regBase;                  /* Base register */
+  int nReg;                     /* Number of registers to allocate */
+  char *zAff;                   /* Affinity string to return */
 
-  /* memset(pScan, 0, sizeof(*pScan)); */
-  pScan->pOrigWC = pWC;
-  pScan->pWC = pWC;
-  if( pIdx && iColumn>=0 ){
-    pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
-    for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
-      if( NEVER(j>pIdx->nColumn) ) return 0;
-    }
-    pScan->zCollName = pIdx->azColl[j];
-  }else{
-    pScan->idxaff = 0;
-    pScan->zCollName = 0;
+  /* This module is only called on query plans that use an index. */
+  pLoop = pLevel->pWLoop;
+  assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
+  nEq = pLoop->u.btree.nEq;
+  nSkip = pLoop->nSkip;
+  pIdx = pLoop->u.btree.pIndex;
+  assert( pIdx!=0 );
+
+  /* Figure out how many memory cells we will need then allocate them.
+  */
+  regBase = pParse->nMem + 1;
+  nReg = pLoop->u.btree.nEq + nExtraReg;
+  pParse->nMem += nReg;
+
+  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
+  if( !zAff ){
+    pParse->db->mallocFailed = 1;
   }
-  pScan->opMask = opMask;
-  pScan->k = 0;
-  pScan->aEquiv[0] = iCur;
-  pScan->aEquiv[1] = iColumn;
-  pScan->nEquiv = 2;
-  pScan->iEquiv = 2;
-  return whereScanNext(pScan);
-}
 
-/*
-** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
-** where X is a reference to the iColumn of table iCur and <op> is one of
-** the WO_xx operator codes specified by the op parameter.
-** Return a pointer to the term.  Return 0 if not found.
-**
-** The term returned might by Y=<expr> if there is another constraint in
-** the WHERE clause that specifies that X=Y.  Any such constraints will be
-** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
-** aEquiv[] array holds X and all its equivalents, with each SQL variable
-** taking up two slots in aEquiv[].  The first slot is for the cursor number
-** and the second is for the column number.  There are 22 slots in aEquiv[]
-** so that means we can look for X plus up to 10 other equivalent values.
-** Hence a search for X will return <expr> if X=A1 and A1=A2 and A2=A3
-** and ... and A9=A10 and A10=<expr>.
-**
-** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
-** then try for the one with no dependencies on <expr> - in other words where
-** <expr> is a constant expression of some kind.  Only return entries of
-** the form "X <op> Y" where Y is a column in another table if no terms of
-** the form "X <op> <const-expr>" exist.   If no terms with a constant RHS
-** exist, try to return a term that does not use WO_EQUIV.
-*/
-static WhereTerm *findTerm(
-  WhereClause *pWC,     /* The WHERE clause to be searched */
-  int iCur,             /* Cursor number of LHS */
-  int iColumn,          /* Column number of LHS */
-  Bitmask notReady,     /* RHS must not overlap with this mask */
-  u32 op,               /* Mask of WO_xx values describing operator */
-  Index *pIdx           /* Must be compatible with this index, if not NULL */
-){
-  WhereTerm *pResult = 0;
-  WhereTerm *p;
-  WhereScan scan;
+  if( nSkip ){
+    int iIdxCur = pLevel->iIdxCur;
+    sqlite3VdbeAddOp1(v, (bRev?OP_Last:OP_Rewind), iIdxCur);
+    VdbeCoverageIf(v, bRev==0);
+    VdbeCoverageIf(v, bRev!=0);
+    VdbeComment((v, "begin skip-scan on %s", pIdx->zName));
+    j = sqlite3VdbeAddOp0(v, OP_Goto);
+    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
+                            iIdxCur, 0, regBase, nSkip);
+    VdbeCoverageIf(v, bRev==0);
+    VdbeCoverageIf(v, bRev!=0);
+    sqlite3VdbeJumpHere(v, j);
+    for(j=0; j<nSkip; j++){
+      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
+      assert( pIdx->aiColumn[j]>=0 );
+      VdbeComment((v, "%s", pIdx->pTable->aCol[pIdx->aiColumn[j]].zName));
+    }
+  }    
 
-  p = whereScanInit(&scan, pWC, iCur, iColumn, op, pIdx);
-  while( p ){
-    if( (p->prereqRight & notReady)==0 ){
-      if( p->prereqRight==0 && (p->eOperator&WO_EQ)!=0 ){
-        return p;
+  /* Evaluate the equality constraints
+  */
+  assert( zAff==0 || (int)strlen(zAff)>=nEq );
+  for(j=nSkip; j<nEq; j++){
+    int r1;
+    pTerm = pLoop->aLTerm[j];
+    assert( pTerm!=0 );
+    /* The following testcase is true for indices with redundant columns. 
+    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
+    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
+    testcase( pTerm->wtFlags & TERM_VIRTUAL );
+    r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
+    if( r1!=regBase+j ){
+      if( nReg==1 ){
+        sqlite3ReleaseTempReg(pParse, regBase);
+        regBase = r1;
+      }else{
+        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
+      }
+    }
+    testcase( pTerm->eOperator & WO_ISNULL );
+    testcase( pTerm->eOperator & WO_IN );
+    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
+      Expr *pRight = pTerm->pExpr->pRight;
+      if( (pTerm->wtFlags & TERM_IS)==0 && sqlite3ExprCanBeNull(pRight) ){
+        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
+        VdbeCoverage(v);
+      }
+      if( zAff ){
+        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_BLOB ){
+          zAff[j] = SQLITE_AFF_BLOB;
+        }
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
+          zAff[j] = SQLITE_AFF_BLOB;
+        }
       }
-      if( pResult==0 ) pResult = p;
     }
-    p = whereScanNext(&scan);
   }
-  return pResult;
+  *pzAff = zAff;
+  return regBase;
 }
 
-/* Forward reference */
-static void exprAnalyze(SrcList*, WhereClause*, int);
-
 /*
-** Call exprAnalyze on all terms in a WHERE clause.  
+** If the most recently coded instruction is a constant range contraint
+** that originated from the LIKE optimization, then change the P3 to be
+** pLoop->iLikeRepCntr and set P5.
+**
+** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
+** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
+** scan loop run twice, once for strings and a second time for BLOBs.
+** The OP_String opcodes on the second pass convert the upper and lower
+** bound string contants to blobs.  This routine makes the necessary changes
+** to the OP_String opcodes for that to happen.
 */
-static void exprAnalyzeAll(
-  SrcList *pTabList,       /* the FROM clause */
-  WhereClause *pWC         /* the WHERE clause to be analyzed */
+static void whereLikeOptimizationStringFixup(
+  Vdbe *v,                /* prepared statement under construction */
+  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
+  WhereTerm *pTerm        /* The upper or lower bound just coded */
 ){
-  int i;
-  for(i=pWC->nTerm-1; i>=0; i--){
-    exprAnalyze(pTabList, pWC, i);
+  if( pTerm->wtFlags & TERM_LIKEOPT ){
+    VdbeOp *pOp;
+    assert( pLevel->iLikeRepCntr>0 );
+    pOp = sqlite3VdbeGetOp(v, -1);
+    assert( pOp!=0 );
+    assert( pOp->opcode==OP_String8 
+            || pTerm->pWC->pWInfo->pParse->db->mallocFailed );
+    pOp->p3 = pLevel->iLikeRepCntr;
+    pOp->p5 = 1;
   }
 }
 
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+
 /*
-** Check to see if the given expression is a LIKE or GLOB operator that
-** can be optimized using inequality constraints.  Return TRUE if it is
-** so and false if not.
-**
-** In order for the operator to be optimizible, the RHS must be a string
-** literal that does not begin with a wildcard.  The LHS must be a column
-** that may only be NULL, a string, or a BLOB, never a number. (This means
-** that virtual tables cannot participate in the LIKE optimization.)  If the
-** collating sequence for the column on the LHS must be appropriate for
-** the operator.
+** Generate code for the start of the iLevel-th loop in the WHERE clause
+** implementation described by pWInfo.
 */
-static int isLikeOrGlob(
+SQLITE_PRIVATE Bitmask sqlite3WhereCodeOneLoopStart(
+  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
+  int iLevel,          /* Which level of pWInfo->a[] should be coded */
+  Bitmask notReady     /* Which tables are currently available */
+){
+  int j, k;            /* Loop counters */
+  int iCur;            /* The VDBE cursor for the table */
+  int addrNxt;         /* Where to jump to continue with the next IN case */
+  int omitTable;       /* True if we use the index only */
+  int bRev;            /* True if we need to scan in reverse order */
+  WhereLevel *pLevel;  /* The where level to be coded */
+  WhereLoop *pLoop;    /* The WhereLoop object being coded */
+  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
+  WhereTerm *pTerm;               /* A WHERE clause term */
+  Parse *pParse;                  /* Parsing context */
+  sqlite3 *db;                    /* Database connection */
+  Vdbe *v;                        /* The prepared stmt under constructions */
+  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
+  int addrBrk;                    /* Jump here to break out of the loop */
+  int addrCont;                   /* Jump here to continue with next cycle */
+  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
+  int iReleaseReg = 0;      /* Temp register to free before returning */
+
+  pParse = pWInfo->pParse;
+  v = pParse->pVdbe;
+  pWC = &pWInfo->sWC;
+  db = pParse->db;
+  pLevel = &pWInfo->a[iLevel];
+  pLoop = pLevel->pWLoop;
+  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
+  iCur = pTabItem->iCursor;
+  pLevel->notReady = notReady & ~sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur);
+  bRev = (pWInfo->revMask>>iLevel)&1;
+  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
+           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
+  VdbeModuleComment((v, "Begin WHERE-loop%d: %s",iLevel,pTabItem->pTab->zName));
+
+  /* Create labels for the "break" and "continue" instructions
+  ** for the current loop.  Jump to addrBrk to break out of a loop.
+  ** Jump to cont to go immediately to the next iteration of the
+  ** loop.
+  **
+  ** When there is an IN operator, we also have a "addrNxt" label that
+  ** means to continue with the next IN value combination.  When
+  ** there are no IN operators in the constraints, the "addrNxt" label
+  ** is the same as "addrBrk".
+  */
+  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
+  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
+
+  /* If this is the right table of a LEFT OUTER JOIN, allocate and
+  ** initialize a memory cell that records if this table matches any
+  ** row of the left table of the join.
+  */
+  if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
+    pLevel->iLeftJoin = ++pParse->nMem;
+    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
+    VdbeComment((v, "init LEFT JOIN no-match flag"));
+  }
+
+  /* Special case of a FROM clause subquery implemented as a co-routine */
+  if( pTabItem->viaCoroutine ){
+    int regYield = pTabItem->regReturn;
+    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
+    pLevel->p2 =  sqlite3VdbeAddOp2(v, OP_Yield, regYield, addrBrk);
+    VdbeCoverage(v);
+    VdbeComment((v, "next row of \"%s\"", pTabItem->pTab->zName));
+    pLevel->op = OP_Goto;
+  }else
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  if(  (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
+    /* Case 1:  The table is a virtual-table.  Use the VFilter and VNext
+    **          to access the data.
+    */
+    int iReg;   /* P3 Value for OP_VFilter */
+    int addrNotFound;
+    int nConstraint = pLoop->nLTerm;
+
+    sqlite3ExprCachePush(pParse);
+    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
+    addrNotFound = pLevel->addrBrk;
+    for(j=0; j<nConstraint; j++){
+      int iTarget = iReg+j+2;
+      pTerm = pLoop->aLTerm[j];
+      if( pTerm==0 ) continue;
+      if( pTerm->eOperator & WO_IN ){
+        codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
+        addrNotFound = pLevel->addrNxt;
+      }else{
+        sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
+      }
+    }
+    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
+    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
+    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
+                      pLoop->u.vtab.idxStr,
+                      pLoop->u.vtab.needFree ? P4_MPRINTF : P4_STATIC);
+    VdbeCoverage(v);
+    pLoop->u.vtab.needFree = 0;
+    for(j=0; j<nConstraint && j<16; j++){
+      if( (pLoop->u.vtab.omitMask>>j)&1 ){
+        disableTerm(pLevel, pLoop->aLTerm[j]);
+      }
+    }
+    pLevel->op = OP_VNext;
+    pLevel->p1 = iCur;
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
+    sqlite3ExprCachePop(pParse);
+  }else
+#endif /* SQLITE_OMIT_VIRTUALTABLE */
+
+  if( (pLoop->wsFlags & WHERE_IPK)!=0
+   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
+  ){
+    /* Case 2:  We can directly reference a single row using an
+    **          equality comparison against the ROWID field.  Or
+    **          we reference multiple rows using a "rowid IN (...)"
+    **          construct.
+    */
+    assert( pLoop->u.btree.nEq==1 );
+    pTerm = pLoop->aLTerm[0];
+    assert( pTerm!=0 );
+    assert( pTerm->pExpr!=0 );
+    assert( omitTable==0 );
+    testcase( pTerm->wtFlags & TERM_VIRTUAL );
+    iReleaseReg = ++pParse->nMem;
+    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
+    if( iRowidReg!=iReleaseReg ) sqlite3ReleaseTempReg(pParse, iReleaseReg);
+    addrNxt = pLevel->addrNxt;
+    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt); VdbeCoverage(v);
+    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
+    VdbeCoverage(v);
+    sqlite3ExprCacheAffinityChange(pParse, iRowidReg, 1);
+    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
+    VdbeComment((v, "pk"));
+    pLevel->op = OP_Noop;
+  }else if( (pLoop->wsFlags & WHERE_IPK)!=0
+         && (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
+  ){
+    /* Case 3:  We have an inequality comparison against the ROWID field.
+    */
+    int testOp = OP_Noop;
+    int start;
+    int memEndValue = 0;
+    WhereTerm *pStart, *pEnd;
+
+    assert( omitTable==0 );
+    j = 0;
+    pStart = pEnd = 0;
+    if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
+    if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
+    assert( pStart!=0 || pEnd!=0 );
+    if( bRev ){
+      pTerm = pStart;
+      pStart = pEnd;
+      pEnd = pTerm;
+    }
+    if( pStart ){
+      Expr *pX;             /* The expression that defines the start bound */
+      int r1, rTemp;        /* Registers for holding the start boundary */
+
+      /* The following constant maps TK_xx codes into corresponding 
+      ** seek opcodes.  It depends on a particular ordering of TK_xx
+      */
+      const u8 aMoveOp[] = {
+           /* TK_GT */  OP_SeekGT,
+           /* TK_LE */  OP_SeekLE,
+           /* TK_LT */  OP_SeekLT,
+           /* TK_GE */  OP_SeekGE
+      };
+      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
+      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
+      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */
+
+      assert( (pStart->wtFlags & TERM_VNULL)==0 );
+      testcase( pStart->wtFlags & TERM_VIRTUAL );
+      pX = pStart->pExpr;
+      assert( pX!=0 );
+      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
+      r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
+      sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
+      VdbeComment((v, "pk"));
+      VdbeCoverageIf(v, pX->op==TK_GT);
+      VdbeCoverageIf(v, pX->op==TK_LE);
+      VdbeCoverageIf(v, pX->op==TK_LT);
+      VdbeCoverageIf(v, pX->op==TK_GE);
+      sqlite3ExprCacheAffinityChange(pParse, r1, 1);
+      sqlite3ReleaseTempReg(pParse, rTemp);
+      disableTerm(pLevel, pStart);
+    }else{
+      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
+      VdbeCoverageIf(v, bRev==0);
+      VdbeCoverageIf(v, bRev!=0);
+    }
+    if( pEnd ){
+      Expr *pX;
+      pX = pEnd->pExpr;
+      assert( pX!=0 );
+      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
+      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
+      testcase( pEnd->wtFlags & TERM_VIRTUAL );
+      memEndValue = ++pParse->nMem;
+      sqlite3ExprCode(pParse, pX->pRight, memEndValue);
+      if( pX->op==TK_LT || pX->op==TK_GT ){
+        testOp = bRev ? OP_Le : OP_Ge;
+      }else{
+        testOp = bRev ? OP_Lt : OP_Gt;
+      }
+      disableTerm(pLevel, pEnd);
+    }
+    start = sqlite3VdbeCurrentAddr(v);
+    pLevel->op = bRev ? OP_Prev : OP_Next;
+    pLevel->p1 = iCur;
+    pLevel->p2 = start;
+    assert( pLevel->p5==0 );
+    if( testOp!=OP_Noop ){
+      iRowidReg = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
+      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
+      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
+      VdbeCoverageIf(v, testOp==OP_Le);
+      VdbeCoverageIf(v, testOp==OP_Lt);
+      VdbeCoverageIf(v, testOp==OP_Ge);
+      VdbeCoverageIf(v, testOp==OP_Gt);
+      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
+    }
+  }else if( pLoop->wsFlags & WHERE_INDEXED ){
+    /* Case 4: A scan using an index.
+    **
+    **         The WHERE clause may contain zero or more equality 
+    **         terms ("==" or "IN" operators) that refer to the N
+    **         left-most columns of the index. It may also contain
+    **         inequality constraints (>, <, >= or <=) on the indexed
+    **         column that immediately follows the N equalities. Only 
+    **         the right-most column can be an inequality - the rest must
+    **         use the "==" and "IN" operators. For example, if the 
+    **         index is on (x,y,z), then the following clauses are all 
+    **         optimized:
+    **
+    **            x=5
+    **            x=5 AND y=10
+    **            x=5 AND y<10
+    **            x=5 AND y>5 AND y<10
+    **            x=5 AND y=5 AND z<=10
+    **
+    **         The z<10 term of the following cannot be used, only
+    **         the x=5 term:
+    **
+    **            x=5 AND z<10
+    **
+    **         N may be zero if there are inequality constraints.
+    **         If there are no inequality constraints, then N is at
+    **         least one.
+    **
+    **         This case is also used when there are no WHERE clause
+    **         constraints but an index is selected anyway, in order
+    **         to force the output order to conform to an ORDER BY.
+    */  
+    static const u8 aStartOp[] = {
+      0,
+      0,
+      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
+      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
+      OP_SeekGT,           /* 4: (start_constraints  && !startEq && !bRev) */
+      OP_SeekLT,           /* 5: (start_constraints  && !startEq &&  bRev) */
+      OP_SeekGE,           /* 6: (start_constraints  &&  startEq && !bRev) */
+      OP_SeekLE            /* 7: (start_constraints  &&  startEq &&  bRev) */
+    };
+    static const u8 aEndOp[] = {
+      OP_IdxGE,            /* 0: (end_constraints && !bRev && !endEq) */
+      OP_IdxGT,            /* 1: (end_constraints && !bRev &&  endEq) */
+      OP_IdxLE,            /* 2: (end_constraints &&  bRev && !endEq) */
+      OP_IdxLT,            /* 3: (end_constraints &&  bRev &&  endEq) */
+    };
+    u16 nEq = pLoop->u.btree.nEq;     /* Number of == or IN terms */
+    int regBase;                 /* Base register holding constraint values */
+    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
+    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
+    int startEq;                 /* True if range start uses ==, >= or <= */
+    int endEq;                   /* True if range end uses ==, >= or <= */
+    int start_constraints;       /* Start of range is constrained */
+    int nConstraint;             /* Number of constraint terms */
+    Index *pIdx;                 /* The index we will be using */
+    int iIdxCur;                 /* The VDBE cursor for the index */
+    int nExtraReg = 0;           /* Number of extra registers needed */
+    int op;                      /* Instruction opcode */
+    char *zStartAff;             /* Affinity for start of range constraint */
+    char cEndAff = 0;            /* Affinity for end of range constraint */
+    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
+    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
+
+    pIdx = pLoop->u.btree.pIndex;
+    iIdxCur = pLevel->iIdxCur;
+    assert( nEq>=pLoop->nSkip );
+
+    /* If this loop satisfies a sort order (pOrderBy) request that 
+    ** was passed to this function to implement a "SELECT min(x) ..." 
+    ** query, then the caller will only allow the loop to run for
+    ** a single iteration. This means that the first row returned
+    ** should not have a NULL value stored in 'x'. If column 'x' is
+    ** the first one after the nEq equality constraints in the index,
+    ** this requires some special handling.
+    */
+    assert( pWInfo->pOrderBy==0
+         || pWInfo->pOrderBy->nExpr==1
+         || (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0 );
+    if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
+     && pWInfo->nOBSat>0
+     && (pIdx->nKeyCol>nEq)
+    ){
+      assert( pLoop->nSkip==0 );
+      bSeekPastNull = 1;
+      nExtraReg = 1;
+    }
+
+    /* Find any inequality constraint terms for the start and end 
+    ** of the range. 
+    */
+    j = nEq;
+    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
+      pRangeStart = pLoop->aLTerm[j++];
+      nExtraReg = 1;
+      /* Like optimization range constraints always occur in pairs */
+      assert( (pRangeStart->wtFlags & TERM_LIKEOPT)==0 || 
+              (pLoop->wsFlags & WHERE_TOP_LIMIT)!=0 );
+    }
+    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
+      pRangeEnd = pLoop->aLTerm[j++];
+      nExtraReg = 1;
+      if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
+        assert( pRangeStart!=0 );                     /* LIKE opt constraints */
+        assert( pRangeStart->wtFlags & TERM_LIKEOPT );   /* occur in pairs */
+        pLevel->iLikeRepCntr = ++pParse->nMem;
+        testcase( bRev );
+        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
+        sqlite3VdbeAddOp2(v, OP_Integer,
+                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
+                          pLevel->iLikeRepCntr);
+        VdbeComment((v, "LIKE loop counter"));
+        pLevel->addrLikeRep = sqlite3VdbeCurrentAddr(v);
+      }
+      if( pRangeStart==0
+       && (j = pIdx->aiColumn[nEq])>=0 
+       && pIdx->pTable->aCol[j].notNull==0
+      ){
+        bSeekPastNull = 1;
+      }
+    }
+    assert( pRangeEnd==0 || (pRangeEnd->wtFlags & TERM_VNULL)==0 );
+
+    /* Generate code to evaluate all constraint terms using == or IN
+    ** and store the values of those terms in an array of registers
+    ** starting at regBase.
+    */
+    regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
+    assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
+    if( zStartAff ) cEndAff = zStartAff[nEq];
+    addrNxt = pLevel->addrNxt;
+
+    /* If we are doing a reverse order scan on an ascending index, or
+    ** a forward order scan on a descending index, interchange the 
+    ** start and end terms (pRangeStart and pRangeEnd).
+    */
+    if( (nEq<pIdx->nKeyCol && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
+     || (bRev && pIdx->nKeyCol==nEq)
+    ){
+      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
+      SWAP(u8, bSeekPastNull, bStopAtNull);
+    }
+
+    testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
+    testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
+    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
+    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
+    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
+    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
+    start_constraints = pRangeStart || nEq>0;
+
+    /* Seek the index cursor to the start of the range. */
+    nConstraint = nEq;
+    if( pRangeStart ){
+      Expr *pRight = pRangeStart->pExpr->pRight;
+      sqlite3ExprCode(pParse, pRight, regBase+nEq);
+      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
+      if( (pRangeStart->wtFlags & TERM_VNULL)==0
+       && sqlite3ExprCanBeNull(pRight)
+      ){
+        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
+        VdbeCoverage(v);
+      }
+      if( zStartAff ){
+        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_BLOB){
+          /* Since the comparison is to be performed with no conversions
+          ** applied to the operands, set the affinity to apply to pRight to 
+          ** SQLITE_AFF_BLOB.  */
+          zStartAff[nEq] = SQLITE_AFF_BLOB;
+        }
+        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
+          zStartAff[nEq] = SQLITE_AFF_BLOB;
+        }
+      }  
+      nConstraint++;
+      testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
+    }else if( bSeekPastNull ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+      nConstraint++;
+      startEq = 0;
+      start_constraints = 1;
+    }
+    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
+    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
+    assert( op!=0 );
+    sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
+    VdbeCoverage(v);
+    VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
+    VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
+    VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
+    VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
+    VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
+    VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
+
+    /* Load the value for the inequality constraint at the end of the
+    ** range (if any).
+    */
+    nConstraint = nEq;
+    if( pRangeEnd ){
+      Expr *pRight = pRangeEnd->pExpr->pRight;
+      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
+      sqlite3ExprCode(pParse, pRight, regBase+nEq);
+      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
+      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
+       && sqlite3ExprCanBeNull(pRight)
+      ){
+        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
+        VdbeCoverage(v);
+      }
+      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_BLOB
+       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)
+      ){
+        codeApplyAffinity(pParse, regBase+nEq, 1, &cEndAff);
+      }
+      nConstraint++;
+      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
+    }else if( bStopAtNull ){
+      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
+      endEq = 0;
+      nConstraint++;
+    }
+    sqlite3DbFree(db, zStartAff);
+
+    /* Top of the loop body */
+    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+
+    /* Check if the index cursor is past the end of the range. */
+    if( nConstraint ){
+      op = aEndOp[bRev*2 + endEq];
+      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
+      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
+      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
+      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
+      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
+    }
+
+    /* Seek the table cursor, if required */
+    disableTerm(pLevel, pRangeStart);
+    disableTerm(pLevel, pRangeEnd);
+    if( omitTable ){
+      /* pIdx is a covering index.  No need to access the main table. */
+    }else if( HasRowid(pIdx->pTable) ){
+      iRowidReg = ++pParse->nMem;
+      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
+      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
+      sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg);  /* Deferred seek */
+    }else if( iCur!=iIdxCur ){
+      Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
+      iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
+      for(j=0; j<pPk->nKeyCol; j++){
+        k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[j]);
+        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
+      }
+      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
+                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
+    }
+
+    /* Record the instruction used to terminate the loop. Disable 
+    ** WHERE clause terms made redundant by the index range scan.
+    */
+    if( pLoop->wsFlags & WHERE_ONEROW ){
+      pLevel->op = OP_Noop;
+    }else if( bRev ){
+      pLevel->op = OP_Prev;
+    }else{
+      pLevel->op = OP_Next;
+    }
+    pLevel->p1 = iIdxCur;
+    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
+    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }else{
+      assert( pLevel->p5==0 );
+    }
+  }else
+
+#ifndef SQLITE_OMIT_OR_OPTIMIZATION
+  if( pLoop->wsFlags & WHERE_MULTI_OR ){
+    /* Case 5:  Two or more separately indexed terms connected by OR
+    **
+    ** Example:
+    **
+    **   CREATE TABLE t1(a,b,c,d);
+    **   CREATE INDEX i1 ON t1(a);
+    **   CREATE INDEX i2 ON t1(b);
+    **   CREATE INDEX i3 ON t1(c);
+    **
+    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
+    **
+    ** In the example, there are three indexed terms connected by OR.
+    ** The top of the loop looks like this:
+    **
+    **          Null       1                # Zero the rowset in reg 1
+    **
+    ** Then, for each indexed term, the following. The arguments to
+    ** RowSetTest are such that the rowid of the current row is inserted
+    ** into the RowSet. If it is already present, control skips the
+    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
+    **
+    **        sqlite3WhereBegin(<term>)
+    **          RowSetTest                  # Insert rowid into rowset
+    **          Gosub      2 A
+    **        sqlite3WhereEnd()
+    **
+    ** Following the above, code to terminate the loop. Label A, the target
+    ** of the Gosub above, jumps to the instruction right after the Goto.
+    **
+    **          Null       1                # Zero the rowset in reg 1
+    **          Goto       B                # The loop is finished.
+    **
+    **       A: <loop body>                 # Return data, whatever.
+    **
+    **          Return     2                # Jump back to the Gosub
+    **
+    **       B: <after the loop>
+    **
+    ** Added 2014-05-26: If the table is a WITHOUT ROWID table, then
+    ** use an ephemeral index instead of a RowSet to record the primary
+    ** keys of the rows we have already seen.
+    **
+    */
+    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
+    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
+    Index *pCov = 0;             /* Potential covering index (or NULL) */
+    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */
+
+    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
+    int regRowset = 0;                        /* Register for RowSet object */
+    int regRowid = 0;                         /* Register holding rowid */
+    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
+    int iRetInit;                             /* Address of regReturn init */
+    int untestedTerms = 0;             /* Some terms not completely tested */
+    int ii;                            /* Loop counter */
+    u16 wctrlFlags;                    /* Flags for sub-WHERE clause */
+    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
+    Table *pTab = pTabItem->pTab;
+   
+    pTerm = pLoop->aLTerm[0];
+    assert( pTerm!=0 );
+    assert( pTerm->eOperator & WO_OR );
+    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
+    pOrWc = &pTerm->u.pOrInfo->wc;
+    pLevel->op = OP_Return;
+    pLevel->p1 = regReturn;
+
+    /* Set up a new SrcList in pOrTab containing the table being scanned
+    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
+    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
+    */
+    if( pWInfo->nLevel>1 ){
+      int nNotReady;                 /* The number of notReady tables */
+      struct SrcList_item *origSrc;     /* Original list of tables */
+      nNotReady = pWInfo->nLevel - iLevel - 1;
+      pOrTab = sqlite3StackAllocRaw(db,
+                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
+      if( pOrTab==0 ) return notReady;
+      pOrTab->nAlloc = (u8)(nNotReady + 1);
+      pOrTab->nSrc = pOrTab->nAlloc;
+      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
+      origSrc = pWInfo->pTabList->a;
+      for(k=1; k<=nNotReady; k++){
+        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
+      }
+    }else{
+      pOrTab = pWInfo->pTabList;
+    }
+
+    /* Initialize the rowset register to contain NULL. An SQL NULL is 
+    ** equivalent to an empty rowset.  Or, create an ephemeral index
+    ** capable of holding primary keys in the case of a WITHOUT ROWID.
+    **
+    ** Also initialize regReturn to contain the address of the instruction 
+    ** immediately following the OP_Return at the bottom of the loop. This
+    ** is required in a few obscure LEFT JOIN cases where control jumps
+    ** over the top of the loop into the body of it. In this case the 
+    ** correct response for the end-of-loop code (the OP_Return) is to 
+    ** fall through to the next instruction, just as an OP_Next does if
+    ** called on an uninitialized cursor.
+    */
+    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
+      if( HasRowid(pTab) ){
+        regRowset = ++pParse->nMem;
+        sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
+      }else{
+        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+        regRowset = pParse->nTab++;
+        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, regRowset, pPk->nKeyCol);
+        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
+      }
+      regRowid = ++pParse->nMem;
+    }
+    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
+
+    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
+    ** Then for every term xN, evaluate as the subexpression: xN AND z
+    ** That way, terms in y that are factored into the disjunction will
+    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
+    **
+    ** Actually, each subexpression is converted to "xN AND w" where w is
+    ** the "interesting" terms of z - terms that did not originate in the
+    ** ON or USING clause of a LEFT JOIN, and terms that are usable as 
+    ** indices.
+    **
+    ** This optimization also only applies if the (x1 OR x2 OR ...) term
+    ** is not contained in the ON clause of a LEFT JOIN.
+    ** See ticket http://www.sqlite.org/src/info/f2369304e4
+    */
+    if( pWC->nTerm>1 ){
+      int iTerm;
+      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
+        Expr *pExpr = pWC->a[iTerm].pExpr;
+        if( &pWC->a[iTerm] == pTerm ) continue;
+        if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
+        if( (pWC->a[iTerm].wtFlags & TERM_VIRTUAL)!=0 ) continue;
+        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
+        testcase( pWC->a[iTerm].wtFlags & TERM_ORINFO );
+        pExpr = sqlite3ExprDup(db, pExpr, 0);
+        pAndExpr = sqlite3ExprAnd(db, pAndExpr, pExpr);
+      }
+      if( pAndExpr ){
+        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
+      }
+    }
+
+    /* Run a separate WHERE clause for each term of the OR clause.  After
+    ** eliminating duplicates from other WHERE clauses, the action for each
+    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
+    */
+    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE
+                | WHERE_FORCE_TABLE
+                | WHERE_ONETABLE_ONLY
+                | WHERE_NO_AUTOINDEX;
+    for(ii=0; ii<pOrWc->nTerm; ii++){
+      WhereTerm *pOrTerm = &pOrWc->a[ii];
+      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
+        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
+        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
+        int j1 = 0;                     /* Address of jump operation */
+        if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
+          pAndExpr->pLeft = pOrExpr;
+          pOrExpr = pAndExpr;
+        }
+        /* Loop through table entries that match term pOrTerm. */
+        WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
+        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
+                                      wctrlFlags, iCovCur);
+        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
+        if( pSubWInfo ){
+          WhereLoop *pSubLoop;
+          int addrExplain = sqlite3WhereExplainOneScan(
+              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
+          );
+          sqlite3WhereAddScanStatus(v, pOrTab, &pSubWInfo->a[0], addrExplain);
+
+          /* This is the sub-WHERE clause body.  First skip over
+          ** duplicate rows from prior sub-WHERE clauses, and record the
+          ** rowid (or PRIMARY KEY) for the current row so that the same
+          ** row will be skipped in subsequent sub-WHERE clauses.
+          */
+          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
+            int r;
+            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
+            if( HasRowid(pTab) ){
+              r = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, regRowid, 0);
+              j1 = sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset, 0, r,iSet);
+              VdbeCoverage(v);
+            }else{
+              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+              int nPk = pPk->nKeyCol;
+              int iPk;
+
+              /* Read the PK into an array of temp registers. */
+              r = sqlite3GetTempRange(pParse, nPk);
+              for(iPk=0; iPk<nPk; iPk++){
+                int iCol = pPk->aiColumn[iPk];
+                int rx;
+                rx = sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur,r+iPk,0);
+                if( rx!=r+iPk ){
+                  sqlite3VdbeAddOp2(v, OP_SCopy, rx, r+iPk);
+                }
+              }
+
+              /* Check if the temp table already contains this key. If so,
+              ** the row has already been included in the result set and
+              ** can be ignored (by jumping past the Gosub below). Otherwise,
+              ** insert the key into the temp table and proceed with processing
+              ** the row.
+              **
+              ** Use some of the same optimizations as OP_RowSetTest: If iSet
+              ** is zero, assume that the key cannot already be present in
+              ** the temp table. And if iSet is -1, assume that there is no 
+              ** need to insert the key into the temp table, as it will never 
+              ** be tested for.  */ 
+              if( iSet ){
+                j1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
+                VdbeCoverage(v);
+              }
+              if( iSet>=0 ){
+                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
+                sqlite3VdbeAddOp3(v, OP_IdxInsert, regRowset, regRowid, 0);
+                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+              }
+
+              /* Release the array of temp registers */
+              sqlite3ReleaseTempRange(pParse, r, nPk);
+            }
+          }
+
+          /* Invoke the main loop body as a subroutine */
+          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
+
+          /* Jump here (skipping the main loop body subroutine) if the
+          ** current sub-WHERE row is a duplicate from prior sub-WHEREs. */
+          if( j1 ) sqlite3VdbeJumpHere(v, j1);
+
+          /* The pSubWInfo->untestedTerms flag means that this OR term
+          ** contained one or more AND term from a notReady table.  The
+          ** terms from the notReady table could not be tested and will
+          ** need to be tested later.
+          */
+          if( pSubWInfo->untestedTerms ) untestedTerms = 1;
+
+          /* If all of the OR-connected terms are optimized using the same
+          ** index, and the index is opened using the same cursor number
+          ** by each call to sqlite3WhereBegin() made by this loop, it may
+          ** be possible to use that index as a covering index.
+          **
+          ** If the call to sqlite3WhereBegin() above resulted in a scan that
+          ** uses an index, and this is either the first OR-connected term
+          ** processed or the index is the same as that used by all previous
+          ** terms, set pCov to the candidate covering index. Otherwise, set 
+          ** pCov to NULL to indicate that no candidate covering index will 
+          ** be available.
+          */
+          pSubLoop = pSubWInfo->a[0].pWLoop;
+          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
+          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
+           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
+           && (HasRowid(pTab) || !IsPrimaryKeyIndex(pSubLoop->u.btree.pIndex))
+          ){
+            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
+            pCov = pSubLoop->u.btree.pIndex;
+            wctrlFlags |= WHERE_REOPEN_IDX;
+          }else{
+            pCov = 0;
+          }
+
+          /* Finish the loop through table entries that match term pOrTerm. */
+          sqlite3WhereEnd(pSubWInfo);
+        }
+      }
+    }
+    pLevel->u.pCovidx = pCov;
+    if( pCov ) pLevel->iIdxCur = iCovCur;
+    if( pAndExpr ){
+      pAndExpr->pLeft = 0;
+      sqlite3ExprDelete(db, pAndExpr);
+    }
+    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
+    sqlite3VdbeResolveLabel(v, iLoopBody);
+
+    if( pWInfo->nLevel>1 ) sqlite3StackFree(db, pOrTab);
+    if( !untestedTerms ) disableTerm(pLevel, pTerm);
+  }else
+#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+
+  {
+    /* Case 6:  There is no usable index.  We must do a complete
+    **          scan of the entire table.
+    */
+    static const u8 aStep[] = { OP_Next, OP_Prev };
+    static const u8 aStart[] = { OP_Rewind, OP_Last };
+    assert( bRev==0 || bRev==1 );
+    if( pTabItem->isRecursive ){
+      /* Tables marked isRecursive have only a single row that is stored in
+      ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
+      pLevel->op = OP_Noop;
+    }else{
+      pLevel->op = aStep[bRev];
+      pLevel->p1 = iCur;
+      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
+      VdbeCoverageIf(v, bRev==0);
+      VdbeCoverageIf(v, bRev!=0);
+      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    }
+  }
+
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
+#endif
+
+  /* Insert code to test every subexpression that can be completely
+  ** computed using the current set of tables.
+  */
+  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
+    Expr *pE;
+    int skipLikeAddr = 0;
+    testcase( pTerm->wtFlags & TERM_VIRTUAL );
+    testcase( pTerm->wtFlags & TERM_CODED );
+    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
+      testcase( pWInfo->untestedTerms==0
+               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
+      pWInfo->untestedTerms = 1;
+      continue;
+    }
+    pE = pTerm->pExpr;
+    assert( pE!=0 );
+    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
+      continue;
+    }
+    if( pTerm->wtFlags & TERM_LIKECOND ){
+      assert( pLevel->iLikeRepCntr>0 );
+      skipLikeAddr = sqlite3VdbeAddOp1(v, OP_IfNot, pLevel->iLikeRepCntr);
+      VdbeCoverage(v);
+    }
+    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
+    if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
+    pTerm->wtFlags |= TERM_CODED;
+  }
+
+  /* Insert code to test for implied constraints based on transitivity
+  ** of the "==" operator.
+  **
+  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
+  ** and we are coding the t1 loop and the t2 loop has not yet coded,
+  ** then we cannot use the "t1.a=t2.b" constraint, but we can code
+  ** the implied "t1.a=123" constraint.
+  */
+  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
+    Expr *pE, *pEAlt;
+    WhereTerm *pAlt;
+    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+    if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) continue;
+    if( (pTerm->eOperator & WO_EQUIV)==0 ) continue;
+    if( pTerm->leftCursor!=iCur ) continue;
+    if( pLevel->iLeftJoin ) continue;
+    pE = pTerm->pExpr;
+    assert( !ExprHasProperty(pE, EP_FromJoin) );
+    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
+    pAlt = sqlite3WhereFindTerm(pWC, iCur, pTerm->u.leftColumn, notReady,
+                    WO_EQ|WO_IN|WO_IS, 0);
+    if( pAlt==0 ) continue;
+    if( pAlt->wtFlags & (TERM_CODED) ) continue;
+    testcase( pAlt->eOperator & WO_EQ );
+    testcase( pAlt->eOperator & WO_IS );
+    testcase( pAlt->eOperator & WO_IN );
+    VdbeModuleComment((v, "begin transitive constraint"));
+    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
+    if( pEAlt ){
+      *pEAlt = *pAlt->pExpr;
+      pEAlt->pLeft = pE->pLeft;
+      sqlite3ExprIfFalse(pParse, pEAlt, addrCont, SQLITE_JUMPIFNULL);
+      sqlite3StackFree(db, pEAlt);
+    }
+  }
+
+  /* For a LEFT OUTER JOIN, generate code that will record the fact that
+  ** at least one row of the right table has matched the left table.  
+  */
+  if( pLevel->iLeftJoin ){
+    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
+    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
+    VdbeComment((v, "record LEFT JOIN hit"));
+    sqlite3ExprCacheClear(pParse);
+    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
+      testcase( pTerm->wtFlags & TERM_VIRTUAL );
+      testcase( pTerm->wtFlags & TERM_CODED );
+      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
+      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
+        assert( pWInfo->untestedTerms );
+        continue;
+      }
+      assert( pTerm->pExpr );
+      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
+      pTerm->wtFlags |= TERM_CODED;
+    }
+  }
+
+  return pLevel->notReady;
+}
+
+/************** End of wherecode.c *******************************************/
+/************** Begin file whereexpr.c ***************************************/
+/*
+** 2015-06-08
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements.
+**
+** This file was originally part of where.c but was split out to improve
+** readability and editabiliity.  This file contains utility routines for
+** analyzing Expr objects in the WHERE clause.
+*/
+/* #include "sqliteInt.h" */
+/* #include "whereInt.h" */
+
+/* Forward declarations */
+static void exprAnalyze(SrcList*, WhereClause*, int);
+
+/*
+** Deallocate all memory associated with a WhereOrInfo object.
+*/
+static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
+  sqlite3WhereClauseClear(&p->wc);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Deallocate all memory associated with a WhereAndInfo object.
+*/
+static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
+  sqlite3WhereClauseClear(&p->wc);
+  sqlite3DbFree(db, p);
+}
+
+/*
+** Add a single new WhereTerm entry to the WhereClause object pWC.
+** The new WhereTerm object is constructed from Expr p and with wtFlags.
+** The index in pWC->a[] of the new WhereTerm is returned on success.
+** 0 is returned if the new WhereTerm could not be added due to a memory
+** allocation error.  The memory allocation failure will be recorded in
+** the db->mallocFailed flag so that higher-level functions can detect it.
+**
+** This routine will increase the size of the pWC->a[] array as necessary.
+**
+** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
+** for freeing the expression p is assumed by the WhereClause object pWC.
+** This is true even if this routine fails to allocate a new WhereTerm.
+**
+** WARNING:  This routine might reallocate the space used to store
+** WhereTerms.  All pointers to WhereTerms should be invalidated after
+** calling this routine.  Such pointers may be reinitialized by referencing
+** the pWC->a[] array.
+*/
+static int whereClauseInsert(WhereClause *pWC, Expr *p, u16 wtFlags){
+  WhereTerm *pTerm;
+  int idx;
+  testcase( wtFlags & TERM_VIRTUAL );
+  if( pWC->nTerm>=pWC->nSlot ){
+    WhereTerm *pOld = pWC->a;
+    sqlite3 *db = pWC->pWInfo->pParse->db;
+    pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
+    if( pWC->a==0 ){
+      if( wtFlags & TERM_DYNAMIC ){
+        sqlite3ExprDelete(db, p);
+      }
+      pWC->a = pOld;
+      return 0;
+    }
+    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
+    if( pOld!=pWC->aStatic ){
+      sqlite3DbFree(db, pOld);
+    }
+    pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
+    memset(&pWC->a[pWC->nTerm], 0, sizeof(pWC->a[0])*(pWC->nSlot-pWC->nTerm));
+  }
+  pTerm = &pWC->a[idx = pWC->nTerm++];
+  if( p && ExprHasProperty(p, EP_Unlikely) ){
+    pTerm->truthProb = sqlite3LogEst(p->iTable) - 270;
+  }else{
+    pTerm->truthProb = 1;
+  }
+  pTerm->pExpr = sqlite3ExprSkipCollate(p);
+  pTerm->wtFlags = wtFlags;
+  pTerm->pWC = pWC;
+  pTerm->iParent = -1;
+  return idx;
+}
+
+/*
+** Return TRUE if the given operator is one of the operators that is
+** allowed for an indexable WHERE clause term.  The allowed operators are
+** "=", "<", ">", "<=", ">=", "IN", and "IS NULL"
+*/
+static int allowedOp(int op){
+  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
+  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
+  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
+  assert( TK_GE==TK_EQ+4 );
+  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL || op==TK_IS;
+}
+
+/*
+** Commute a comparison operator.  Expressions of the form "X op Y"
+** are converted into "Y op X".
+**
+** If left/right precedence rules come into play when determining the
+** collating sequence, then COLLATE operators are adjusted to ensure
+** that the collating sequence does not change.  For example:
+** "Y collate NOCASE op X" becomes "X op Y" because any collation sequence on
+** the left hand side of a comparison overrides any collation sequence 
+** attached to the right. For the same reason the EP_Collate flag
+** is not commuted.
+*/
+static void exprCommute(Parse *pParse, Expr *pExpr){
+  u16 expRight = (pExpr->pRight->flags & EP_Collate);
+  u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
+  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
+  if( expRight==expLeft ){
+    /* Either X and Y both have COLLATE operator or neither do */
+    if( expRight ){
+      /* Both X and Y have COLLATE operators.  Make sure X is always
+      ** used by clearing the EP_Collate flag from Y. */
+      pExpr->pRight->flags &= ~EP_Collate;
+    }else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
+      /* Neither X nor Y have COLLATE operators, but X has a non-default
+      ** collating sequence.  So add the EP_Collate marker on X to cause
+      ** it to be searched first. */
+      pExpr->pLeft->flags |= EP_Collate;
+    }
+  }
+  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
+  if( pExpr->op>=TK_GT ){
+    assert( TK_LT==TK_GT+2 );
+    assert( TK_GE==TK_LE+2 );
+    assert( TK_GT>TK_EQ );
+    assert( TK_GT<TK_LE );
+    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
+    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
+  }
+}
+
+/*
+** Translate from TK_xx operator to WO_xx bitmask.
+*/
+static u16 operatorMask(int op){
+  u16 c;
+  assert( allowedOp(op) );
+  if( op==TK_IN ){
+    c = WO_IN;
+  }else if( op==TK_ISNULL ){
+    c = WO_ISNULL;
+  }else if( op==TK_IS ){
+    c = WO_IS;
+  }else{
+    assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
+    c = (u16)(WO_EQ<<(op-TK_EQ));
+  }
+  assert( op!=TK_ISNULL || c==WO_ISNULL );
+  assert( op!=TK_IN || c==WO_IN );
+  assert( op!=TK_EQ || c==WO_EQ );
+  assert( op!=TK_LT || c==WO_LT );
+  assert( op!=TK_LE || c==WO_LE );
+  assert( op!=TK_GT || c==WO_GT );
+  assert( op!=TK_GE || c==WO_GE );
+  assert( op!=TK_IS || c==WO_IS );
+  return c;
+}
+
+
+#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
+/*
+** Check to see if the given expression is a LIKE or GLOB operator that
+** can be optimized using inequality constraints.  Return TRUE if it is
+** so and false if not.
+**
+** In order for the operator to be optimizible, the RHS must be a string
+** literal that does not begin with a wildcard.  The LHS must be a column
+** that may only be NULL, a string, or a BLOB, never a number. (This means
+** that virtual tables cannot participate in the LIKE optimization.)  The
+** collating sequence for the column on the LHS must be appropriate for
+** the operator.
+*/
+static int isLikeOrGlob(
   Parse *pParse,    /* Parsing and code generating context */
   Expr *pExpr,      /* Test this expression */
   Expr **ppPrefix,  /* Pointer to TK_STRING expression with pattern prefix */
@@ -116847,7 +119133,7 @@ static int isLikeOrGlob(
   if( op==TK_VARIABLE ){
     Vdbe *pReprepare = pParse->pReprepare;
     int iCol = pRight->iColumn;
-    pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_NONE);
+    pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_BLOB);
     if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
       z = (char *)sqlite3_value_text(pVal);
     }
@@ -117058,7 +119344,7 @@ static void whereCombineDisjuncts(
 **
 ** CASE 2:
 **
-** If there are exactly two disjuncts one side has x>A and the other side
+** If there are exactly two disjuncts and one side has x>A and the other side
 ** has x=A (for the same x and A) then add a new virtual conjunct term to the
 ** WHERE clause of the form "x>=A".  Example:
 **
@@ -117087,22 +119373,22 @@ static void whereCombineDisjuncts(
 ** is decided elsewhere.  This analysis only looks at whether subterms
 ** appropriate for indexing exist.
 **
-** All examples A through E above satisfy case 2.  But if a term
+** All examples A through E above satisfy case 3.  But if a term
 ** also satisfies case 1 (such as B) we know that the optimizer will
-** always prefer case 1, so in that case we pretend that case 2 is not
+** always prefer case 1, so in that case we pretend that case 3 is not
 ** satisfied.
 **
 ** It might be the case that multiple tables are indexable.  For example,
 ** (E) above is indexable on tables P, Q, and R.
 **
-** Terms that satisfy case 2 are candidates for lookup by using
+** Terms that satisfy case 3 are candidates for lookup by using
 ** separate indices to find rowids for each subterm and composing
 ** the union of all rowids using a RowSet object.  This is similar
 ** to "bitmap indices" in other database engines.
 **
 ** OTHERWISE:
 **
-** If neither case 1 nor case 2 apply, then leave the eOperator set to
+** If none of cases 1, 2, or 3 apply, then leave the eOperator set to
 ** zero.  This term is not useful for search.
 */
 static void exprAnalyzeOrTerm(
@@ -117133,14 +119419,14 @@ static void exprAnalyzeOrTerm(
   if( pOrInfo==0 ) return;
   pTerm->wtFlags |= TERM_ORINFO;
   pOrWc = &pOrInfo->wc;
-  whereClauseInit(pOrWc, pWInfo);
-  whereSplit(pOrWc, pExpr, TK_OR);
-  exprAnalyzeAll(pSrc, pOrWc);
+  sqlite3WhereClauseInit(pOrWc, pWInfo);
+  sqlite3WhereSplit(pOrWc, pExpr, TK_OR);
+  sqlite3WhereExprAnalyze(pSrc, pOrWc);
   if( db->mallocFailed ) return;
   assert( pOrWc->nTerm>=2 );
 
   /*
-  ** Compute the set of tables that might satisfy cases 1 or 2.
+  ** Compute the set of tables that might satisfy cases 1 or 3.
   */
   indexable = ~(Bitmask)0;
   chngToIN = ~(Bitmask)0;
@@ -117159,16 +119445,16 @@ static void exprAnalyzeOrTerm(
         pOrTerm->wtFlags |= TERM_ANDINFO;
         pOrTerm->eOperator = WO_AND;
         pAndWC = &pAndInfo->wc;
-        whereClauseInit(pAndWC, pWC->pWInfo);
-        whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
-        exprAnalyzeAll(pSrc, pAndWC);
+        sqlite3WhereClauseInit(pAndWC, pWC->pWInfo);
+        sqlite3WhereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
+        sqlite3WhereExprAnalyze(pSrc, pAndWC);
         pAndWC->pOuter = pWC;
         testcase( db->mallocFailed );
         if( !db->mallocFailed ){
           for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
             assert( pAndTerm->pExpr );
             if( allowedOp(pAndTerm->pExpr->op) ){
-              b |= getMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
+              b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
             }
           }
         }
@@ -117179,10 +119465,10 @@ static void exprAnalyzeOrTerm(
       ** corresponding TERM_VIRTUAL term */
     }else{
       Bitmask b;
-      b = getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
+      b = sqlite3WhereGetMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
       if( pOrTerm->wtFlags & TERM_VIRTUAL ){
         WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
-        b |= getMask(&pWInfo->sMaskSet, pOther->leftCursor);
+        b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pOther->leftCursor);
       }
       indexable &= b;
       if( (pOrTerm->eOperator & WO_EQ)==0 ){
@@ -117258,7 +119544,8 @@ static void exprAnalyzeOrTerm(
           assert( j==1 );
           continue;
         }
-        if( (chngToIN & getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor))==0 ){
+        if( (chngToIN & sqlite3WhereGetMask(&pWInfo->sMaskSet,
+                                            pOrTerm->leftCursor))==0 ){
           /* This term must be of the form t1.a==t2.b where t2 is in the
           ** chngToIN set but t1 is not.  This term will be either preceded
           ** or follwed by an inverted copy (t2.b==t1.a).  Skip this term 
@@ -117277,7 +119564,7 @@ static void exprAnalyzeOrTerm(
         ** on the second iteration */
         assert( j==1 );
         assert( IsPowerOfTwo(chngToIN) );
-        assert( chngToIN==getMask(&pWInfo->sMaskSet, iCursor) );
+        assert( chngToIN==sqlite3WhereGetMask(&pWInfo->sMaskSet, iCursor) );
         break;
       }
       testcase( j==1 );
@@ -117349,6 +119636,72 @@ static void exprAnalyzeOrTerm(
 }
 #endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
 
+/*
+** We already know that pExpr is a binary operator where both operands are
+** column references.  This routine checks to see if pExpr is an equivalence
+** relation:
+**   1.  The SQLITE_Transitive optimization must be enabled
+**   2.  Must be either an == or an IS operator
+**   3.  Not originating in the ON clause of an OUTER JOIN
+**   4.  The affinities of A and B must be compatible
+**   5a. Both operands use the same collating sequence OR
+**   5b. The overall collating sequence is BINARY
+** If this routine returns TRUE, that means that the RHS can be substituted
+** for the LHS anyplace else in the WHERE clause where the LHS column occurs.
+** This is an optimization.  No harm comes from returning 0.  But if 1 is
+** returned when it should not be, then incorrect answers might result.
+*/
+static int termIsEquivalence(Parse *pParse, Expr *pExpr){
+  char aff1, aff2;
+  CollSeq *pColl;
+  const char *zColl1, *zColl2;
+  if( !OptimizationEnabled(pParse->db, SQLITE_Transitive) ) return 0;
+  if( pExpr->op!=TK_EQ && pExpr->op!=TK_IS ) return 0;
+  if( ExprHasProperty(pExpr, EP_FromJoin) ) return 0;
+  aff1 = sqlite3ExprAffinity(pExpr->pLeft);
+  aff2 = sqlite3ExprAffinity(pExpr->pRight);
+  if( aff1!=aff2
+   && (!sqlite3IsNumericAffinity(aff1) || !sqlite3IsNumericAffinity(aff2))
+  ){
+    return 0;
+  }
+  pColl = sqlite3BinaryCompareCollSeq(pParse, pExpr->pLeft, pExpr->pRight);
+  if( pColl==0 || sqlite3StrICmp(pColl->zName, "BINARY")==0 ) return 1;
+  pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
+  /* Since pLeft and pRight are both a column references, their collating
+  ** sequence should always be defined. */
+  zColl1 = ALWAYS(pColl) ? pColl->zName : 0;
+  pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
+  zColl2 = ALWAYS(pColl) ? pColl->zName : 0;
+  return sqlite3StrICmp(zColl1, zColl2)==0;
+}
+
+/*
+** Recursively walk the expressions of a SELECT statement and generate
+** a bitmask indicating which tables are used in that expression
+** tree.
+*/
+static Bitmask exprSelectUsage(WhereMaskSet *pMaskSet, Select *pS){
+  Bitmask mask = 0;
+  while( pS ){
+    SrcList *pSrc = pS->pSrc;
+    mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pEList);
+    mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pGroupBy);
+    mask |= sqlite3WhereExprListUsage(pMaskSet, pS->pOrderBy);
+    mask |= sqlite3WhereExprUsage(pMaskSet, pS->pWhere);
+    mask |= sqlite3WhereExprUsage(pMaskSet, pS->pHaving);
+    if( ALWAYS(pSrc!=0) ){
+      int i;
+      for(i=0; i<pSrc->nSrc; i++){
+        mask |= exprSelectUsage(pMaskSet, pSrc->a[i].pSelect);
+        mask |= sqlite3WhereExprUsage(pMaskSet, pSrc->a[i].pOn);
+      }
+    }
+    pS = pS->pPrior;
+  }
+  return mask;
+}
+
 /*
 ** The input to this routine is an WhereTerm structure with only the
 ** "pExpr" field filled in.  The job of this routine is to analyze the
@@ -117393,23 +119746,23 @@ static void exprAnalyze(
   pMaskSet = &pWInfo->sMaskSet;
   pExpr = pTerm->pExpr;
   assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
-  prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
+  prereqLeft = sqlite3WhereExprUsage(pMaskSet, pExpr->pLeft);
   op = pExpr->op;
   if( op==TK_IN ){
     assert( pExpr->pRight==0 );
     if( ExprHasProperty(pExpr, EP_xIsSelect) ){
-      pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
+      pTerm->prereqRight = exprSelectUsage(pMaskSet, pExpr->x.pSelect);
     }else{
-      pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
+      pTerm->prereqRight = sqlite3WhereExprListUsage(pMaskSet, pExpr->x.pList);
     }
   }else if( op==TK_ISNULL ){
     pTerm->prereqRight = 0;
   }else{
-    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
+    pTerm->prereqRight = sqlite3WhereExprUsage(pMaskSet, pExpr->pRight);
   }
-  prereqAll = exprTableUsage(pMaskSet, pExpr);
+  prereqAll = sqlite3WhereExprUsage(pMaskSet, pExpr);
   if( ExprHasProperty(pExpr, EP_FromJoin) ){
-    Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
+    Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->iRightJoinTable);
     prereqAll |= x;
     extraRight = x-1;  /* ON clause terms may not be used with an index
                        ** on left table of a LEFT JOIN.  Ticket #3015 */
@@ -117427,6 +119780,7 @@ static void exprAnalyze(
       pTerm->u.leftColumn = pLeft->iColumn;
       pTerm->eOperator = operatorMask(op) & opMask;
     }
+    if( op==TK_IS ) pTerm->wtFlags |= TERM_IS;
     if( pRight && pRight->op==TK_COLUMN ){
       WhereTerm *pNew;
       Expr *pDup;
@@ -117442,12 +119796,11 @@ static void exprAnalyze(
         if( idxNew==0 ) return;
         pNew = &pWC->a[idxNew];
         markTermAsChild(pWC, idxNew, idxTerm);
+        if( op==TK_IS ) pNew->wtFlags |= TERM_IS;
         pTerm = &pWC->a[idxTerm];
         pTerm->wtFlags |= TERM_COPIED;
-        if( pExpr->op==TK_EQ
-         && !ExprHasProperty(pExpr, EP_FromJoin)
-         && OptimizationEnabled(db, SQLITE_Transitive)
-        ){
+
+        if( termIsEquivalence(pParse, pDup) ){
           pTerm->eOperator |= WO_EQUIV;
           eExtraOp = WO_EQUIV;
         }
@@ -117614,8 +119967,8 @@ static void exprAnalyze(
 
     pRight = pExpr->x.pList->a[0].pExpr;
     pLeft = pExpr->x.pList->a[1].pExpr;
-    prereqExpr = exprTableUsage(pMaskSet, pRight);
-    prereqColumn = exprTableUsage(pMaskSet, pLeft);
+    prereqExpr = sqlite3WhereExprUsage(pMaskSet, pRight);
+    prereqColumn = sqlite3WhereExprUsage(pMaskSet, pLeft);
     if( (prereqExpr & prereqColumn)==0 ){
       Expr *pNewExpr;
       pNewExpr = sqlite3PExpr(pParse, TK_MATCH, 
@@ -117641,2682 +119994,1722 @@ static void exprAnalyze(
   ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
   ** virtual term of that form.
   **
-  ** Note that the virtual term must be tagged with TERM_VNULL.  This
-  ** TERM_VNULL tag will suppress the not-null check at the beginning
-  ** of the loop.  Without the TERM_VNULL flag, the not-null check at
-  ** the start of the loop will prevent any results from being returned.
+  ** Note that the virtual term must be tagged with TERM_VNULL.
   */
   if( pExpr->op==TK_NOTNULL
    && pExpr->pLeft->op==TK_COLUMN
-   && pExpr->pLeft->iColumn>=0
-   && OptimizationEnabled(db, SQLITE_Stat34)
-  ){
-    Expr *pNewExpr;
-    Expr *pLeft = pExpr->pLeft;
-    int idxNew;
-    WhereTerm *pNewTerm;
-
-    pNewExpr = sqlite3PExpr(pParse, TK_GT,
-                            sqlite3ExprDup(db, pLeft, 0),
-                            sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
-
-    idxNew = whereClauseInsert(pWC, pNewExpr,
-                              TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
-    if( idxNew ){
-      pNewTerm = &pWC->a[idxNew];
-      pNewTerm->prereqRight = 0;
-      pNewTerm->leftCursor = pLeft->iTable;
-      pNewTerm->u.leftColumn = pLeft->iColumn;
-      pNewTerm->eOperator = WO_GT;
-      markTermAsChild(pWC, idxNew, idxTerm);
-      pTerm = &pWC->a[idxTerm];
-      pTerm->wtFlags |= TERM_COPIED;
-      pNewTerm->prereqAll = pTerm->prereqAll;
-    }
-  }
-#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
-
-  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
-  ** an index for tables to the left of the join.
-  */
-  pTerm->prereqRight |= extraRight;
-}
-
-/*
-** This function searches pList for an entry that matches the iCol-th column
-** of index pIdx.
-**
-** If such an expression is found, its index in pList->a[] is returned. If
-** no expression is found, -1 is returned.
-*/
-static int findIndexCol(
-  Parse *pParse,                  /* Parse context */
-  ExprList *pList,                /* Expression list to search */
-  int iBase,                      /* Cursor for table associated with pIdx */
-  Index *pIdx,                    /* Index to match column of */
-  int iCol                        /* Column of index to match */
-){
-  int i;
-  const char *zColl = pIdx->azColl[iCol];
-
-  for(i=0; i<pList->nExpr; i++){
-    Expr *p = sqlite3ExprSkipCollate(pList->a[i].pExpr);
-    if( p->op==TK_COLUMN
-     && p->iColumn==pIdx->aiColumn[iCol]
-     && p->iTable==iBase
-    ){
-      CollSeq *pColl = sqlite3ExprCollSeq(pParse, pList->a[i].pExpr);
-      if( pColl && 0==sqlite3StrICmp(pColl->zName, zColl) ){
-        return i;
-      }
-    }
-  }
-
-  return -1;
-}
-
-/*
-** Return true if the DISTINCT expression-list passed as the third argument
-** is redundant.
-**
-** A DISTINCT list is redundant if the database contains some subset of
-** columns that are unique and non-null.
-*/
-static int isDistinctRedundant(
-  Parse *pParse,            /* Parsing context */
-  SrcList *pTabList,        /* The FROM clause */
-  WhereClause *pWC,         /* The WHERE clause */
-  ExprList *pDistinct       /* The result set that needs to be DISTINCT */
-){
-  Table *pTab;
-  Index *pIdx;
-  int i;                          
-  int iBase;
-
-  /* If there is more than one table or sub-select in the FROM clause of
-  ** this query, then it will not be possible to show that the DISTINCT 
-  ** clause is redundant. */
-  if( pTabList->nSrc!=1 ) return 0;
-  iBase = pTabList->a[0].iCursor;
-  pTab = pTabList->a[0].pTab;
-
-  /* If any of the expressions is an IPK column on table iBase, then return 
-  ** true. Note: The (p->iTable==iBase) part of this test may be false if the
-  ** current SELECT is a correlated sub-query.
-  */
-  for(i=0; i<pDistinct->nExpr; i++){
-    Expr *p = sqlite3ExprSkipCollate(pDistinct->a[i].pExpr);
-    if( p->op==TK_COLUMN && p->iTable==iBase && p->iColumn<0 ) return 1;
-  }
-
-  /* Loop through all indices on the table, checking each to see if it makes
-  ** the DISTINCT qualifier redundant. It does so if:
-  **
-  **   1. The index is itself UNIQUE, and
-  **
-  **   2. All of the columns in the index are either part of the pDistinct
-  **      list, or else the WHERE clause contains a term of the form "col=X",
-  **      where X is a constant value. The collation sequences of the
-  **      comparison and select-list expressions must match those of the index.
-  **
-  **   3. All of those index columns for which the WHERE clause does not
-  **      contain a "col=X" term are subject to a NOT NULL constraint.
-  */
-  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
-    if( !IsUniqueIndex(pIdx) ) continue;
-    for(i=0; i<pIdx->nKeyCol; i++){
-      i16 iCol = pIdx->aiColumn[i];
-      if( 0==findTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) ){
-        int iIdxCol = findIndexCol(pParse, pDistinct, iBase, pIdx, i);
-        if( iIdxCol<0 || pTab->aCol[iCol].notNull==0 ){
-          break;
-        }
-      }
-    }
-    if( i==pIdx->nKeyCol ){
-      /* This index implies that the DISTINCT qualifier is redundant. */
-      return 1;
-    }
-  }
-
-  return 0;
-}
-
-
-/*
-** Estimate the logarithm of the input value to base 2.
-*/
-static LogEst estLog(LogEst N){
-  return N<=10 ? 0 : sqlite3LogEst(N) - 33;
-}
-
-/*
-** Two routines for printing the content of an sqlite3_index_info
-** structure.  Used for testing and debugging only.  If neither
-** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
-** are no-ops.
-*/
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(WHERETRACE_ENABLED)
-static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
-  int i;
-  if( !sqlite3WhereTrace ) return;
-  for(i=0; i<p->nConstraint; i++){
-    sqlite3DebugPrintf("  constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
-       i,
-       p->aConstraint[i].iColumn,
-       p->aConstraint[i].iTermOffset,
-       p->aConstraint[i].op,
-       p->aConstraint[i].usable);
-  }
-  for(i=0; i<p->nOrderBy; i++){
-    sqlite3DebugPrintf("  orderby[%d]: col=%d desc=%d\n",
-       i,
-       p->aOrderBy[i].iColumn,
-       p->aOrderBy[i].desc);
-  }
-}
-static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
-  int i;
-  if( !sqlite3WhereTrace ) return;
-  for(i=0; i<p->nConstraint; i++){
-    sqlite3DebugPrintf("  usage[%d]: argvIdx=%d omit=%d\n",
-       i,
-       p->aConstraintUsage[i].argvIndex,
-       p->aConstraintUsage[i].omit);
-  }
-  sqlite3DebugPrintf("  idxNum=%d\n", p->idxNum);
-  sqlite3DebugPrintf("  idxStr=%s\n", p->idxStr);
-  sqlite3DebugPrintf("  orderByConsumed=%d\n", p->orderByConsumed);
-  sqlite3DebugPrintf("  estimatedCost=%g\n", p->estimatedCost);
-  sqlite3DebugPrintf("  estimatedRows=%lld\n", p->estimatedRows);
-}
-#else
-#define TRACE_IDX_INPUTS(A)
-#define TRACE_IDX_OUTPUTS(A)
-#endif
-
-#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
-/*
-** Return TRUE if the WHERE clause term pTerm is of a form where it
-** could be used with an index to access pSrc, assuming an appropriate
-** index existed.
-*/
-static int termCanDriveIndex(
-  WhereTerm *pTerm,              /* WHERE clause term to check */
-  struct SrcList_item *pSrc,     /* Table we are trying to access */
-  Bitmask notReady               /* Tables in outer loops of the join */
-){
-  char aff;
-  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
-  if( (pTerm->eOperator & WO_EQ)==0 ) return 0;
-  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
-  if( pTerm->u.leftColumn<0 ) return 0;
-  aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
-  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
-  return 1;
-}
-#endif
-
-
-#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
-/*
-** Generate code to construct the Index object for an automatic index
-** and to set up the WhereLevel object pLevel so that the code generator
-** makes use of the automatic index.
-*/
-static void constructAutomaticIndex(
-  Parse *pParse,              /* The parsing context */
-  WhereClause *pWC,           /* The WHERE clause */
-  struct SrcList_item *pSrc,  /* The FROM clause term to get the next index */
-  Bitmask notReady,           /* Mask of cursors that are not available */
-  WhereLevel *pLevel          /* Write new index here */
-){
-  int nKeyCol;                /* Number of columns in the constructed index */
-  WhereTerm *pTerm;           /* A single term of the WHERE clause */
-  WhereTerm *pWCEnd;          /* End of pWC->a[] */
-  Index *pIdx;                /* Object describing the transient index */
-  Vdbe *v;                    /* Prepared statement under construction */
-  int addrInit;               /* Address of the initialization bypass jump */
-  Table *pTable;              /* The table being indexed */
-  int addrTop;                /* Top of the index fill loop */
-  int regRecord;              /* Register holding an index record */
-  int n;                      /* Column counter */
-  int i;                      /* Loop counter */
-  int mxBitCol;               /* Maximum column in pSrc->colUsed */
-  CollSeq *pColl;             /* Collating sequence to on a column */
-  WhereLoop *pLoop;           /* The Loop object */
-  char *zNotUsed;             /* Extra space on the end of pIdx */
-  Bitmask idxCols;            /* Bitmap of columns used for indexing */
-  Bitmask extraCols;          /* Bitmap of additional columns */
-  u8 sentWarning = 0;         /* True if a warnning has been issued */
-  Expr *pPartial = 0;         /* Partial Index Expression */
-  int iContinue = 0;          /* Jump here to skip excluded rows */
-
-  /* Generate code to skip over the creation and initialization of the
-  ** transient index on 2nd and subsequent iterations of the loop. */
-  v = pParse->pVdbe;
-  assert( v!=0 );
-  addrInit = sqlite3CodeOnce(pParse); VdbeCoverage(v);
-
-  /* Count the number of columns that will be added to the index
-  ** and used to match WHERE clause constraints */
-  nKeyCol = 0;
-  pTable = pSrc->pTab;
-  pWCEnd = &pWC->a[pWC->nTerm];
-  pLoop = pLevel->pWLoop;
-  idxCols = 0;
-  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
-    Expr *pExpr = pTerm->pExpr;
-    assert( !ExprHasProperty(pExpr, EP_FromJoin)    /* prereq always non-zero */
-         || pExpr->iRightJoinTable!=pSrc->iCursor   /*   for the right-hand   */
-         || pLoop->prereq!=0 );                     /*   table of a LEFT JOIN */
-    if( pLoop->prereq==0
-     && (pTerm->wtFlags & TERM_VIRTUAL)==0
-     && !ExprHasProperty(pExpr, EP_FromJoin)
-     && sqlite3ExprIsTableConstant(pExpr, pSrc->iCursor) ){
-      pPartial = sqlite3ExprAnd(pParse->db, pPartial,
-                                sqlite3ExprDup(pParse->db, pExpr, 0));
-    }
-    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
-      int iCol = pTerm->u.leftColumn;
-      Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
-      testcase( iCol==BMS );
-      testcase( iCol==BMS-1 );
-      if( !sentWarning ){
-        sqlite3_log(SQLITE_WARNING_AUTOINDEX,
-            "automatic index on %s(%s)", pTable->zName,
-            pTable->aCol[iCol].zName);
-        sentWarning = 1;
-      }
-      if( (idxCols & cMask)==0 ){
-        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ){
-          goto end_auto_index_create;
-        }
-        pLoop->aLTerm[nKeyCol++] = pTerm;
-        idxCols |= cMask;
-      }
-    }
-  }
-  assert( nKeyCol>0 );
-  pLoop->u.btree.nEq = pLoop->nLTerm = nKeyCol;
-  pLoop->wsFlags = WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WHERE_INDEXED
-                     | WHERE_AUTO_INDEX;
-
-  /* Count the number of additional columns needed to create a
-  ** covering index.  A "covering index" is an index that contains all
-  ** columns that are needed by the query.  With a covering index, the
-  ** original table never needs to be accessed.  Automatic indices must
-  ** be a covering index because the index will not be updated if the
-  ** original table changes and the index and table cannot both be used
-  ** if they go out of sync.
-  */
-  extraCols = pSrc->colUsed & (~idxCols | MASKBIT(BMS-1));
-  mxBitCol = MIN(BMS-1,pTable->nCol);
-  testcase( pTable->nCol==BMS-1 );
-  testcase( pTable->nCol==BMS-2 );
-  for(i=0; i<mxBitCol; i++){
-    if( extraCols & MASKBIT(i) ) nKeyCol++;
-  }
-  if( pSrc->colUsed & MASKBIT(BMS-1) ){
-    nKeyCol += pTable->nCol - BMS + 1;
-  }
-
-  /* Construct the Index object to describe this index */
-  pIdx = sqlite3AllocateIndexObject(pParse->db, nKeyCol+1, 0, &zNotUsed);
-  if( pIdx==0 ) goto end_auto_index_create;
-  pLoop->u.btree.pIndex = pIdx;
-  pIdx->zName = "auto-index";
-  pIdx->pTable = pTable;
-  n = 0;
-  idxCols = 0;
-  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
-    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
-      int iCol = pTerm->u.leftColumn;
-      Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
-      testcase( iCol==BMS-1 );
-      testcase( iCol==BMS );
-      if( (idxCols & cMask)==0 ){
-        Expr *pX = pTerm->pExpr;
-        idxCols |= cMask;
-        pIdx->aiColumn[n] = pTerm->u.leftColumn;
-        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
-        pIdx->azColl[n] = pColl ? pColl->zName : "BINARY";
-        n++;
-      }
-    }
-  }
-  assert( (u32)n==pLoop->u.btree.nEq );
-
-  /* Add additional columns needed to make the automatic index into
-  ** a covering index */
-  for(i=0; i<mxBitCol; i++){
-    if( extraCols & MASKBIT(i) ){
-      pIdx->aiColumn[n] = i;
-      pIdx->azColl[n] = "BINARY";
-      n++;
-    }
-  }
-  if( pSrc->colUsed & MASKBIT(BMS-1) ){
-    for(i=BMS-1; i<pTable->nCol; i++){
-      pIdx->aiColumn[n] = i;
-      pIdx->azColl[n] = "BINARY";
-      n++;
-    }
-  }
-  assert( n==nKeyCol );
-  pIdx->aiColumn[n] = -1;
-  pIdx->azColl[n] = "BINARY";
-
-  /* Create the automatic index */
-  assert( pLevel->iIdxCur>=0 );
-  pLevel->iIdxCur = pParse->nTab++;
-  sqlite3VdbeAddOp2(v, OP_OpenAutoindex, pLevel->iIdxCur, nKeyCol+1);
-  sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
-  VdbeComment((v, "for %s", pTable->zName));
-
-  /* Fill the automatic index with content */
-  sqlite3ExprCachePush(pParse);
-  addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur); VdbeCoverage(v);
-  if( pPartial ){
-    iContinue = sqlite3VdbeMakeLabel(v);
-    sqlite3ExprIfFalse(pParse, pPartial, iContinue, SQLITE_JUMPIFNULL);
-    pLoop->wsFlags |= WHERE_PARTIALIDX;
-  }
-  regRecord = sqlite3GetTempReg(pParse);
-  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 0, 0, 0, 0);
-  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
-  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
-  if( pPartial ) sqlite3VdbeResolveLabel(v, iContinue);
-  sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1); VdbeCoverage(v);
-  sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
-  sqlite3VdbeJumpHere(v, addrTop);
-  sqlite3ReleaseTempReg(pParse, regRecord);
-  sqlite3ExprCachePop(pParse);
-  
-  /* Jump here when skipping the initialization */
-  sqlite3VdbeJumpHere(v, addrInit);
-
-end_auto_index_create:
-  sqlite3ExprDelete(pParse->db, pPartial);
-}
-#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-/*
-** Allocate and populate an sqlite3_index_info structure. It is the 
-** responsibility of the caller to eventually release the structure
-** by passing the pointer returned by this function to sqlite3_free().
-*/
-static sqlite3_index_info *allocateIndexInfo(
-  Parse *pParse,
-  WhereClause *pWC,
-  struct SrcList_item *pSrc,
-  ExprList *pOrderBy
-){
-  int i, j;
-  int nTerm;
-  struct sqlite3_index_constraint *pIdxCons;
-  struct sqlite3_index_orderby *pIdxOrderBy;
-  struct sqlite3_index_constraint_usage *pUsage;
-  WhereTerm *pTerm;
-  int nOrderBy;
-  sqlite3_index_info *pIdxInfo;
-
-  /* Count the number of possible WHERE clause constraints referring
-  ** to this virtual table */
-  for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
-    if( pTerm->leftCursor != pSrc->iCursor ) continue;
-    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
-    testcase( pTerm->eOperator & WO_IN );
-    testcase( pTerm->eOperator & WO_ISNULL );
-    testcase( pTerm->eOperator & WO_ALL );
-    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV))==0 ) continue;
-    if( pTerm->wtFlags & TERM_VNULL ) continue;
-    nTerm++;
-  }
-
-  /* If the ORDER BY clause contains only columns in the current 
-  ** virtual table then allocate space for the aOrderBy part of
-  ** the sqlite3_index_info structure.
-  */
-  nOrderBy = 0;
-  if( pOrderBy ){
-    int n = pOrderBy->nExpr;
-    for(i=0; i<n; i++){
-      Expr *pExpr = pOrderBy->a[i].pExpr;
-      if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
-    }
-    if( i==n){
-      nOrderBy = n;
-    }
-  }
-
-  /* Allocate the sqlite3_index_info structure
-  */
-  pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
-                           + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
-                           + sizeof(*pIdxOrderBy)*nOrderBy );
-  if( pIdxInfo==0 ){
-    sqlite3ErrorMsg(pParse, "out of memory");
-    return 0;
-  }
-
-  /* Initialize the structure.  The sqlite3_index_info structure contains
-  ** many fields that are declared "const" to prevent xBestIndex from
-  ** changing them.  We have to do some funky casting in order to
-  ** initialize those fields.
-  */
-  pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
-  pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
-  pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
-  *(int*)&pIdxInfo->nConstraint = nTerm;
-  *(int*)&pIdxInfo->nOrderBy = nOrderBy;
-  *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
-  *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
-  *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
-                                                                   pUsage;
-
-  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
-    u8 op;
-    if( pTerm->leftCursor != pSrc->iCursor ) continue;
-    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
-    testcase( pTerm->eOperator & WO_IN );
-    testcase( pTerm->eOperator & WO_ISNULL );
-    testcase( pTerm->eOperator & WO_ALL );
-    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV))==0 ) continue;
-    if( pTerm->wtFlags & TERM_VNULL ) continue;
-    pIdxCons[j].iColumn = pTerm->u.leftColumn;
-    pIdxCons[j].iTermOffset = i;
-    op = (u8)pTerm->eOperator & WO_ALL;
-    if( op==WO_IN ) op = WO_EQ;
-    pIdxCons[j].op = op;
-    /* The direct assignment in the previous line is possible only because
-    ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
-    ** following asserts verify this fact. */
-    assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
-    assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
-    assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
-    assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
-    assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
-    assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
-    assert( pTerm->eOperator & (WO_IN|WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
-    j++;
-  }
-  for(i=0; i<nOrderBy; i++){
-    Expr *pExpr = pOrderBy->a[i].pExpr;
-    pIdxOrderBy[i].iColumn = pExpr->iColumn;
-    pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
-  }
-
-  return pIdxInfo;
-}
-
-/*
-** The table object reference passed as the second argument to this function
-** must represent a virtual table. This function invokes the xBestIndex()
-** method of the virtual table with the sqlite3_index_info object that
-** comes in as the 3rd argument to this function.
-**
-** If an error occurs, pParse is populated with an error message and a
-** non-zero value is returned. Otherwise, 0 is returned and the output
-** part of the sqlite3_index_info structure is left populated.
-**
-** Whether or not an error is returned, it is the responsibility of the
-** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
-** that this is required.
-*/
-static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
-  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
-  int i;
-  int rc;
-
-  TRACE_IDX_INPUTS(p);
-  rc = pVtab->pModule->xBestIndex(pVtab, p);
-  TRACE_IDX_OUTPUTS(p);
-
-  if( rc!=SQLITE_OK ){
-    if( rc==SQLITE_NOMEM ){
-      pParse->db->mallocFailed = 1;
-    }else if( !pVtab->zErrMsg ){
-      sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
-    }else{
-      sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
-    }
-  }
-  sqlite3_free(pVtab->zErrMsg);
-  pVtab->zErrMsg = 0;
-
-  for(i=0; i<p->nConstraint; i++){
-    if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
-      sqlite3ErrorMsg(pParse, 
-          "table %s: xBestIndex returned an invalid plan", pTab->zName);
-    }
-  }
-
-  return pParse->nErr;
-}
-#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
-
-#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
-/*
-** Estimate the location of a particular key among all keys in an
-** index.  Store the results in aStat as follows:
-**
-**    aStat[0]      Est. number of rows less than pRec
-**    aStat[1]      Est. number of rows equal to pRec
-**
-** Return the index of the sample that is the smallest sample that
-** is greater than or equal to pRec. Note that this index is not an index
-** into the aSample[] array - it is an index into a virtual set of samples
-** based on the contents of aSample[] and the number of fields in record 
-** pRec. 
-*/
-static int whereKeyStats(
-  Parse *pParse,              /* Database connection */
-  Index *pIdx,                /* Index to consider domain of */
-  UnpackedRecord *pRec,       /* Vector of values to consider */
-  int roundUp,                /* Round up if true.  Round down if false */
-  tRowcnt *aStat              /* OUT: stats written here */
-){
-  IndexSample *aSample = pIdx->aSample;
-  int iCol;                   /* Index of required stats in anEq[] etc. */
-  int i;                      /* Index of first sample >= pRec */
-  int iSample;                /* Smallest sample larger than or equal to pRec */
-  int iMin = 0;               /* Smallest sample not yet tested */
-  int iTest;                  /* Next sample to test */
-  int res;                    /* Result of comparison operation */
-  int nField;                 /* Number of fields in pRec */
-  tRowcnt iLower = 0;         /* anLt[] + anEq[] of largest sample pRec is > */
-
-#ifndef SQLITE_DEBUG
-  UNUSED_PARAMETER( pParse );
-#endif
-  assert( pRec!=0 );
-  assert( pIdx->nSample>0 );
-  assert( pRec->nField>0 && pRec->nField<=pIdx->nSampleCol );
-
-  /* Do a binary search to find the first sample greater than or equal
-  ** to pRec. If pRec contains a single field, the set of samples to search
-  ** is simply the aSample[] array. If the samples in aSample[] contain more
-  ** than one fields, all fields following the first are ignored.
-  **
-  ** If pRec contains N fields, where N is more than one, then as well as the
-  ** samples in aSample[] (truncated to N fields), the search also has to
-  ** consider prefixes of those samples. For example, if the set of samples
-  ** in aSample is:
-  **
-  **     aSample[0] = (a, 5) 
-  **     aSample[1] = (a, 10) 
-  **     aSample[2] = (b, 5) 
-  **     aSample[3] = (c, 100) 
-  **     aSample[4] = (c, 105)
-  **
-  ** Then the search space should ideally be the samples above and the 
-  ** unique prefixes [a], [b] and [c]. But since that is hard to organize, 
-  ** the code actually searches this set:
-  **
-  **     0: (a) 
-  **     1: (a, 5) 
-  **     2: (a, 10) 
-  **     3: (a, 10) 
-  **     4: (b) 
-  **     5: (b, 5) 
-  **     6: (c) 
-  **     7: (c, 100) 
-  **     8: (c, 105)
-  **     9: (c, 105)
-  **
-  ** For each sample in the aSample[] array, N samples are present in the
-  ** effective sample array. In the above, samples 0 and 1 are based on 
-  ** sample aSample[0]. Samples 2 and 3 on aSample[1] etc.
-  **
-  ** Often, sample i of each block of N effective samples has (i+1) fields.
-  ** Except, each sample may be extended to ensure that it is greater than or
-  ** equal to the previous sample in the array. For example, in the above, 
-  ** sample 2 is the first sample of a block of N samples, so at first it 
-  ** appears that it should be 1 field in size. However, that would make it 
-  ** smaller than sample 1, so the binary search would not work. As a result, 
-  ** it is extended to two fields. The duplicates that this creates do not 
-  ** cause any problems.
-  */
-  nField = pRec->nField;
-  iCol = 0;
-  iSample = pIdx->nSample * nField;
-  do{
-    int iSamp;                    /* Index in aSample[] of test sample */
-    int n;                        /* Number of fields in test sample */
-
-    iTest = (iMin+iSample)/2;
-    iSamp = iTest / nField;
-    if( iSamp>0 ){
-      /* The proposed effective sample is a prefix of sample aSample[iSamp].
-      ** Specifically, the shortest prefix of at least (1 + iTest%nField) 
-      ** fields that is greater than the previous effective sample.  */
-      for(n=(iTest % nField) + 1; n<nField; n++){
-        if( aSample[iSamp-1].anLt[n-1]!=aSample[iSamp].anLt[n-1] ) break;
-      }
-    }else{
-      n = iTest + 1;
-    }
-
-    pRec->nField = n;
-    res = sqlite3VdbeRecordCompare(aSample[iSamp].n, aSample[iSamp].p, pRec);
-    if( res<0 ){
-      iLower = aSample[iSamp].anLt[n-1] + aSample[iSamp].anEq[n-1];
-      iMin = iTest+1;
-    }else if( res==0 && n<nField ){
-      iLower = aSample[iSamp].anLt[n-1];
-      iMin = iTest+1;
-      res = -1;
-    }else{
-      iSample = iTest;
-      iCol = n-1;
-    }
-  }while( res && iMin<iSample );
-  i = iSample / nField;
-
-#ifdef SQLITE_DEBUG
-  /* The following assert statements check that the binary search code
-  ** above found the right answer. This block serves no purpose other
-  ** than to invoke the asserts.  */
-  if( pParse->db->mallocFailed==0 ){
-    if( res==0 ){
-      /* If (res==0) is true, then pRec must be equal to sample i. */
-      assert( i<pIdx->nSample );
-      assert( iCol==nField-1 );
-      pRec->nField = nField;
-      assert( 0==sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec) 
-           || pParse->db->mallocFailed 
-      );
-    }else{
-      /* Unless i==pIdx->nSample, indicating that pRec is larger than
-      ** all samples in the aSample[] array, pRec must be smaller than the
-      ** (iCol+1) field prefix of sample i.  */
-      assert( i<=pIdx->nSample && i>=0 );
-      pRec->nField = iCol+1;
-      assert( i==pIdx->nSample 
-           || sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)>0
-           || pParse->db->mallocFailed );
-
-      /* if i==0 and iCol==0, then record pRec is smaller than all samples
-      ** in the aSample[] array. Otherwise, if (iCol>0) then pRec must
-      ** be greater than or equal to the (iCol) field prefix of sample i.
-      ** If (i>0), then pRec must also be greater than sample (i-1).  */
-      if( iCol>0 ){
-        pRec->nField = iCol;
-        assert( sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)<=0
-             || pParse->db->mallocFailed );
-      }
-      if( i>0 ){
-        pRec->nField = nField;
-        assert( sqlite3VdbeRecordCompare(aSample[i-1].n, aSample[i-1].p, pRec)<0
-             || pParse->db->mallocFailed );
-      }
-    }
-  }
-#endif /* ifdef SQLITE_DEBUG */
-
-  if( res==0 ){
-    /* Record pRec is equal to sample i */
-    assert( iCol==nField-1 );
-    aStat[0] = aSample[i].anLt[iCol];
-    aStat[1] = aSample[i].anEq[iCol];
-  }else{
-    /* At this point, the (iCol+1) field prefix of aSample[i] is the first 
-    ** sample that is greater than pRec. Or, if i==pIdx->nSample then pRec
-    ** is larger than all samples in the array. */
-    tRowcnt iUpper, iGap;
-    if( i>=pIdx->nSample ){
-      iUpper = sqlite3LogEstToInt(pIdx->aiRowLogEst[0]);
-    }else{
-      iUpper = aSample[i].anLt[iCol];
-    }
-
-    if( iLower>=iUpper ){
-      iGap = 0;
-    }else{
-      iGap = iUpper - iLower;
-    }
-    if( roundUp ){
-      iGap = (iGap*2)/3;
-    }else{
-      iGap = iGap/3;
-    }
-    aStat[0] = iLower + iGap;
-    aStat[1] = pIdx->aAvgEq[iCol];
-  }
-
-  /* Restore the pRec->nField value before returning.  */
-  pRec->nField = nField;
-  return i;
-}
-#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
-
-/*
-** If it is not NULL, pTerm is a term that provides an upper or lower
-** bound on a range scan. Without considering pTerm, it is estimated 
-** that the scan will visit nNew rows. This function returns the number
-** estimated to be visited after taking pTerm into account.
-**
-** If the user explicitly specified a likelihood() value for this term,
-** then the return value is the likelihood multiplied by the number of
-** input rows. Otherwise, this function assumes that an "IS NOT NULL" term
-** has a likelihood of 0.50, and any other term a likelihood of 0.25.
-*/
-static LogEst whereRangeAdjust(WhereTerm *pTerm, LogEst nNew){
-  LogEst nRet = nNew;
-  if( pTerm ){
-    if( pTerm->truthProb<=0 ){
-      nRet += pTerm->truthProb;
-    }else if( (pTerm->wtFlags & TERM_VNULL)==0 ){
-      nRet -= 20;        assert( 20==sqlite3LogEst(4) );
-    }
-  }
-  return nRet;
-}
-
-#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
-/* 
-** This function is called to estimate the number of rows visited by a
-** range-scan on a skip-scan index. For example:
-**
-**   CREATE INDEX i1 ON t1(a, b, c);
-**   SELECT * FROM t1 WHERE a=? AND c BETWEEN ? AND ?;
-**
-** Value pLoop->nOut is currently set to the estimated number of rows 
-** visited for scanning (a=? AND b=?). This function reduces that estimate 
-** by some factor to account for the (c BETWEEN ? AND ?) expression based
-** on the stat4 data for the index. this scan will be peformed multiple 
-** times (once for each (a,b) combination that matches a=?) is dealt with 
-** by the caller.
-**
-** It does this by scanning through all stat4 samples, comparing values
-** extracted from pLower and pUpper with the corresponding column in each
-** sample. If L and U are the number of samples found to be less than or
-** equal to the values extracted from pLower and pUpper respectively, and
-** N is the total number of samples, the pLoop->nOut value is adjusted
-** as follows:
-**
-**   nOut = nOut * ( min(U - L, 1) / N )
-**
-** If pLower is NULL, or a value cannot be extracted from the term, L is
-** set to zero. If pUpper is NULL, or a value cannot be extracted from it,
-** U is set to N.
-**
-** Normally, this function sets *pbDone to 1 before returning. However,
-** if no value can be extracted from either pLower or pUpper (and so the
-** estimate of the number of rows delivered remains unchanged), *pbDone
-** is left as is.
-**
-** If an error occurs, an SQLite error code is returned. Otherwise, 
-** SQLITE_OK.
-*/
-static int whereRangeSkipScanEst(
-  Parse *pParse,       /* Parsing & code generating context */
-  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
-  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
-  WhereLoop *pLoop,    /* Update the .nOut value of this loop */
-  int *pbDone          /* Set to true if at least one expr. value extracted */
-){
-  Index *p = pLoop->u.btree.pIndex;
-  int nEq = pLoop->u.btree.nEq;
-  sqlite3 *db = pParse->db;
-  int nLower = -1;
-  int nUpper = p->nSample+1;
-  int rc = SQLITE_OK;
-  int iCol = p->aiColumn[nEq];
-  u8 aff = iCol>=0 ? p->pTable->aCol[iCol].affinity : SQLITE_AFF_INTEGER;
-  CollSeq *pColl;
-  
-  sqlite3_value *p1 = 0;          /* Value extracted from pLower */
-  sqlite3_value *p2 = 0;          /* Value extracted from pUpper */
-  sqlite3_value *pVal = 0;        /* Value extracted from record */
-
-  pColl = sqlite3LocateCollSeq(pParse, p->azColl[nEq]);
-  if( pLower ){
-    rc = sqlite3Stat4ValueFromExpr(pParse, pLower->pExpr->pRight, aff, &p1);
-    nLower = 0;
-  }
-  if( pUpper && rc==SQLITE_OK ){
-    rc = sqlite3Stat4ValueFromExpr(pParse, pUpper->pExpr->pRight, aff, &p2);
-    nUpper = p2 ? 0 : p->nSample;
-  }
-
-  if( p1 || p2 ){
-    int i;
-    int nDiff;
-    for(i=0; rc==SQLITE_OK && i<p->nSample; i++){
-      rc = sqlite3Stat4Column(db, p->aSample[i].p, p->aSample[i].n, nEq, &pVal);
-      if( rc==SQLITE_OK && p1 ){
-        int res = sqlite3MemCompare(p1, pVal, pColl);
-        if( res>=0 ) nLower++;
-      }
-      if( rc==SQLITE_OK && p2 ){
-        int res = sqlite3MemCompare(p2, pVal, pColl);
-        if( res>=0 ) nUpper++;
-      }
-    }
-    nDiff = (nUpper - nLower);
-    if( nDiff<=0 ) nDiff = 1;
+   && pExpr->pLeft->iColumn>=0
+   && OptimizationEnabled(db, SQLITE_Stat34)
+  ){
+    Expr *pNewExpr;
+    Expr *pLeft = pExpr->pLeft;
+    int idxNew;
+    WhereTerm *pNewTerm;
 
-    /* If there is both an upper and lower bound specified, and the 
-    ** comparisons indicate that they are close together, use the fallback
-    ** method (assume that the scan visits 1/64 of the rows) for estimating
-    ** the number of rows visited. Otherwise, estimate the number of rows
-    ** using the method described in the header comment for this function. */
-    if( nDiff!=1 || pUpper==0 || pLower==0 ){
-      int nAdjust = (sqlite3LogEst(p->nSample) - sqlite3LogEst(nDiff));
-      pLoop->nOut -= nAdjust;
-      *pbDone = 1;
-      WHERETRACE(0x10, ("range skip-scan regions: %u..%u  adjust=%d est=%d\n",
-                           nLower, nUpper, nAdjust*-1, pLoop->nOut));
-    }
+    pNewExpr = sqlite3PExpr(pParse, TK_GT,
+                            sqlite3ExprDup(db, pLeft, 0),
+                            sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
 
-  }else{
-    assert( *pbDone==0 );
+    idxNew = whereClauseInsert(pWC, pNewExpr,
+                              TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
+    if( idxNew ){
+      pNewTerm = &pWC->a[idxNew];
+      pNewTerm->prereqRight = 0;
+      pNewTerm->leftCursor = pLeft->iTable;
+      pNewTerm->u.leftColumn = pLeft->iColumn;
+      pNewTerm->eOperator = WO_GT;
+      markTermAsChild(pWC, idxNew, idxTerm);
+      pTerm = &pWC->a[idxTerm];
+      pTerm->wtFlags |= TERM_COPIED;
+      pNewTerm->prereqAll = pTerm->prereqAll;
+    }
   }
+#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
-  sqlite3ValueFree(p1);
-  sqlite3ValueFree(p2);
-  sqlite3ValueFree(pVal);
-
-  return rc;
+  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
+  ** an index for tables to the left of the join.
+  */
+  pTerm->prereqRight |= extraRight;
 }
-#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
+
+/***************************************************************************
+** Routines with file scope above.  Interface to the rest of the where.c
+** subsystem follows.
+***************************************************************************/
 
 /*
-** This function is used to estimate the number of rows that will be visited
-** by scanning an index for a range of values. The range may have an upper
-** bound, a lower bound, or both. The WHERE clause terms that set the upper
-** and lower bounds are represented by pLower and pUpper respectively. For
-** example, assuming that index p is on t1(a):
-**
-**   ... FROM t1 WHERE a > ? AND a < ? ...
-**                    |_____|   |_____|
-**                       |         |
-**                     pLower    pUpper
-**
-** If either of the upper or lower bound is not present, then NULL is passed in
-** place of the corresponding WhereTerm.
-**
-** The value in (pBuilder->pNew->u.btree.nEq) is the number of the index
-** column subject to the range constraint. Or, equivalently, the number of
-** equality constraints optimized by the proposed index scan. For example,
-** assuming index p is on t1(a, b), and the SQL query is:
-**
-**   ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
-**
-** then nEq is set to 1 (as the range restricted column, b, is the second 
-** left-most column of the index). Or, if the query is:
+** This routine identifies subexpressions in the WHERE clause where
+** each subexpression is separated by the AND operator or some other
+** operator specified in the op parameter.  The WhereClause structure
+** is filled with pointers to subexpressions.  For example:
 **
-**   ... FROM t1 WHERE a > ? AND a < ? ...
+**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
+**           \________/     \_______________/     \________________/
+**            slot[0]            slot[1]               slot[2]
 **
-** then nEq is set to 0.
+** The original WHERE clause in pExpr is unaltered.  All this routine
+** does is make slot[] entries point to substructure within pExpr.
 **
-** When this function is called, *pnOut is set to the sqlite3LogEst() of the
-** number of rows that the index scan is expected to visit without 
-** considering the range constraints. If nEq is 0, then *pnOut is the number of 
-** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced)
-** to account for the range constraints pLower and pUpper.
-** 
-** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be
-** used, a single range inequality reduces the search space by a factor of 4. 
-** and a pair of constraints (x>? AND x<?) reduces the expected number of
-** rows visited by a factor of 64.
+** In the previous sentence and in the diagram, "slot[]" refers to
+** the WhereClause.a[] array.  The slot[] array grows as needed to contain
+** all terms of the WHERE clause.
 */
-static int whereRangeScanEst(
-  Parse *pParse,       /* Parsing & code generating context */
-  WhereLoopBuilder *pBuilder,
-  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
-  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
-  WhereLoop *pLoop     /* Modify the .nOut and maybe .rRun fields */
-){
-  int rc = SQLITE_OK;
-  int nOut = pLoop->nOut;
-  LogEst nNew;
-
-#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
-  Index *p = pLoop->u.btree.pIndex;
-  int nEq = pLoop->u.btree.nEq;
-
-  if( p->nSample>0 && nEq<p->nSampleCol ){
-    if( nEq==pBuilder->nRecValid ){
-      UnpackedRecord *pRec = pBuilder->pRec;
-      tRowcnt a[2];
-      u8 aff;
-
-      /* Variable iLower will be set to the estimate of the number of rows in 
-      ** the index that are less than the lower bound of the range query. The
-      ** lower bound being the concatenation of $P and $L, where $P is the
-      ** key-prefix formed by the nEq values matched against the nEq left-most
-      ** columns of the index, and $L is the value in pLower.
-      **
-      ** Or, if pLower is NULL or $L cannot be extracted from it (because it
-      ** is not a simple variable or literal value), the lower bound of the
-      ** range is $P. Due to a quirk in the way whereKeyStats() works, even
-      ** if $L is available, whereKeyStats() is called for both ($P) and 
-      ** ($P:$L) and the larger of the two returned values is used.
-      **
-      ** Similarly, iUpper is to be set to the estimate of the number of rows
-      ** less than the upper bound of the range query. Where the upper bound
-      ** is either ($P) or ($P:$U). Again, even if $U is available, both values
-      ** of iUpper are requested of whereKeyStats() and the smaller used.
-      **
-      ** The number of rows between the two bounds is then just iUpper-iLower.
-      */
-      tRowcnt iLower;     /* Rows less than the lower bound */
-      tRowcnt iUpper;     /* Rows less than the upper bound */
-      int iLwrIdx = -2;   /* aSample[] for the lower bound */
-      int iUprIdx = -1;   /* aSample[] for the upper bound */
-
-      if( pRec ){
-        testcase( pRec->nField!=pBuilder->nRecValid );
-        pRec->nField = pBuilder->nRecValid;
-      }
-      if( nEq==p->nKeyCol ){
-        aff = SQLITE_AFF_INTEGER;
-      }else{
-        aff = p->pTable->aCol[p->aiColumn[nEq]].affinity;
-      }
-      /* Determine iLower and iUpper using ($P) only. */
-      if( nEq==0 ){
-        iLower = 0;
-        iUpper = p->nRowEst0;
-      }else{
-        /* Note: this call could be optimized away - since the same values must 
-        ** have been requested when testing key $P in whereEqualScanEst().  */
-        whereKeyStats(pParse, p, pRec, 0, a);
-        iLower = a[0];
-        iUpper = a[0] + a[1];
-      }
+SQLITE_PRIVATE void sqlite3WhereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
+  Expr *pE2 = sqlite3ExprSkipCollate(pExpr);
+  pWC->op = op;
+  if( pE2==0 ) return;
+  if( pE2->op!=op ){
+    whereClauseInsert(pWC, pExpr, 0);
+  }else{
+    sqlite3WhereSplit(pWC, pE2->pLeft, op);
+    sqlite3WhereSplit(pWC, pE2->pRight, op);
+  }
+}
 
-      assert( pLower==0 || (pLower->eOperator & (WO_GT|WO_GE))!=0 );
-      assert( pUpper==0 || (pUpper->eOperator & (WO_LT|WO_LE))!=0 );
-      assert( p->aSortOrder!=0 );
-      if( p->aSortOrder[nEq] ){
-        /* The roles of pLower and pUpper are swapped for a DESC index */
-        SWAP(WhereTerm*, pLower, pUpper);
-      }
+/*
+** Initialize a preallocated WhereClause structure.
+*/
+SQLITE_PRIVATE void sqlite3WhereClauseInit(
+  WhereClause *pWC,        /* The WhereClause to be initialized */
+  WhereInfo *pWInfo        /* The WHERE processing context */
+){
+  pWC->pWInfo = pWInfo;
+  pWC->pOuter = 0;
+  pWC->nTerm = 0;
+  pWC->nSlot = ArraySize(pWC->aStatic);
+  pWC->a = pWC->aStatic;
+}
 
-      /* If possible, improve on the iLower estimate using ($P:$L). */
-      if( pLower ){
-        int bOk;                    /* True if value is extracted from pExpr */
-        Expr *pExpr = pLower->pExpr->pRight;
-        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
-        if( rc==SQLITE_OK && bOk ){
-          tRowcnt iNew;
-          iLwrIdx = whereKeyStats(pParse, p, pRec, 0, a);
-          iNew = a[0] + ((pLower->eOperator & (WO_GT|WO_LE)) ? a[1] : 0);
-          if( iNew>iLower ) iLower = iNew;
-          nOut--;
-          pLower = 0;
-        }
-      }
+/*
+** Deallocate a WhereClause structure.  The WhereClause structure
+** itself is not freed.  This routine is the inverse of sqlite3WhereClauseInit().
+*/
+SQLITE_PRIVATE void sqlite3WhereClauseClear(WhereClause *pWC){
+  int i;
+  WhereTerm *a;
+  sqlite3 *db = pWC->pWInfo->pParse->db;
+  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
+    if( a->wtFlags & TERM_DYNAMIC ){
+      sqlite3ExprDelete(db, a->pExpr);
+    }
+    if( a->wtFlags & TERM_ORINFO ){
+      whereOrInfoDelete(db, a->u.pOrInfo);
+    }else if( a->wtFlags & TERM_ANDINFO ){
+      whereAndInfoDelete(db, a->u.pAndInfo);
+    }
+  }
+  if( pWC->a!=pWC->aStatic ){
+    sqlite3DbFree(db, pWC->a);
+  }
+}
 
-      /* If possible, improve on the iUpper estimate using ($P:$U). */
-      if( pUpper ){
-        int bOk;                    /* True if value is extracted from pExpr */
-        Expr *pExpr = pUpper->pExpr->pRight;
-        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
-        if( rc==SQLITE_OK && bOk ){
-          tRowcnt iNew;
-          iUprIdx = whereKeyStats(pParse, p, pRec, 1, a);
-          iNew = a[0] + ((pUpper->eOperator & (WO_GT|WO_LE)) ? a[1] : 0);
-          if( iNew<iUpper ) iUpper = iNew;
-          nOut--;
-          pUpper = 0;
-        }
-      }
 
-      pBuilder->pRec = pRec;
-      if( rc==SQLITE_OK ){
-        if( iUpper>iLower ){
-          nNew = sqlite3LogEst(iUpper - iLower);
-          /* TUNING:  If both iUpper and iLower are derived from the same
-          ** sample, then assume they are 4x more selective.  This brings
-          ** the estimated selectivity more in line with what it would be
-          ** if estimated without the use of STAT3/4 tables. */
-          if( iLwrIdx==iUprIdx ) nNew -= 20;  assert( 20==sqlite3LogEst(4) );
-        }else{
-          nNew = 10;        assert( 10==sqlite3LogEst(2) );
-        }
-        if( nNew<nOut ){
-          nOut = nNew;
-        }
-        WHERETRACE(0x10, ("STAT4 range scan: %u..%u  est=%d\n",
-                           (u32)iLower, (u32)iUpper, nOut));
-      }
-    }else{
-      int bDone = 0;
-      rc = whereRangeSkipScanEst(pParse, pLower, pUpper, pLoop, &bDone);
-      if( bDone ) return rc;
+/*
+** These routines walk (recursively) an expression tree and generate
+** a bitmask indicating which tables are used in that expression
+** tree.
+*/
+SQLITE_PRIVATE Bitmask sqlite3WhereExprUsage(WhereMaskSet *pMaskSet, Expr *p){
+  Bitmask mask = 0;
+  if( p==0 ) return 0;
+  if( p->op==TK_COLUMN ){
+    mask = sqlite3WhereGetMask(pMaskSet, p->iTable);
+    return mask;
+  }
+  mask = sqlite3WhereExprUsage(pMaskSet, p->pRight);
+  mask |= sqlite3WhereExprUsage(pMaskSet, p->pLeft);
+  if( ExprHasProperty(p, EP_xIsSelect) ){
+    mask |= exprSelectUsage(pMaskSet, p->x.pSelect);
+  }else{
+    mask |= sqlite3WhereExprListUsage(pMaskSet, p->x.pList);
+  }
+  return mask;
+}
+SQLITE_PRIVATE Bitmask sqlite3WhereExprListUsage(WhereMaskSet *pMaskSet, ExprList *pList){
+  int i;
+  Bitmask mask = 0;
+  if( pList ){
+    for(i=0; i<pList->nExpr; i++){
+      mask |= sqlite3WhereExprUsage(pMaskSet, pList->a[i].pExpr);
     }
   }
-#else
-  UNUSED_PARAMETER(pParse);
-  UNUSED_PARAMETER(pBuilder);
-  assert( pLower || pUpper );
-#endif
-  assert( pUpper==0 || (pUpper->wtFlags & TERM_VNULL)==0 );
-  nNew = whereRangeAdjust(pLower, nOut);
-  nNew = whereRangeAdjust(pUpper, nNew);
+  return mask;
+}
 
-  /* TUNING: If there is both an upper and lower limit and neither limit
-  ** has an application-defined likelihood(), assume the range is
-  ** reduced by an additional 75%. This means that, by default, an open-ended
-  ** range query (e.g. col > ?) is assumed to match 1/4 of the rows in the
-  ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
-  ** match 1/64 of the index. */ 
-  if( pLower && pLower->truthProb>0 && pUpper && pUpper->truthProb>0 ){
-    nNew -= 20;
-  }
 
-  nOut -= (pLower!=0) + (pUpper!=0);
-  if( nNew<10 ) nNew = 10;
-  if( nNew<nOut ) nOut = nNew;
-#if defined(WHERETRACE_ENABLED)
-  if( pLoop->nOut>nOut ){
-    WHERETRACE(0x10,("Range scan lowers nOut from %d to %d\n",
-                    pLoop->nOut, nOut));
+/*
+** Call exprAnalyze on all terms in a WHERE clause.  
+**
+** Note that exprAnalyze() might add new virtual terms onto the
+** end of the WHERE clause.  We do not want to analyze these new
+** virtual terms, so start analyzing at the end and work forward
+** so that the added virtual terms are never processed.
+*/
+SQLITE_PRIVATE void sqlite3WhereExprAnalyze(
+  SrcList *pTabList,       /* the FROM clause */
+  WhereClause *pWC         /* the WHERE clause to be analyzed */
+){
+  int i;
+  for(i=pWC->nTerm-1; i>=0; i--){
+    exprAnalyze(pTabList, pWC, i);
   }
-#endif
-  pLoop->nOut = (LogEst)nOut;
-  return rc;
 }
 
-#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+/************** End of whereexpr.c *******************************************/
+/************** Begin file where.c *******************************************/
 /*
-** Estimate the number of rows that will be returned based on
-** an equality constraint x=VALUE and where that VALUE occurs in
-** the histogram data.  This only works when x is the left-most
-** column of an index and sqlite_stat3 histogram data is available
-** for that index.  When pExpr==NULL that means the constraint is
-** "x IS NULL" instead of "x=VALUE".
+** 2001 September 15
 **
-** Write the estimated row count into *pnRow and return SQLITE_OK. 
-** If unable to make an estimate, leave *pnRow unchanged and return
-** non-zero.
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
 **
-** This routine can fail if it is unable to load a collating sequence
-** required for string comparison, or if unable to allocate memory
-** for a UTF conversion required for comparison.  The error is stored
-** in the pParse structure.
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This module contains C code that generates VDBE code used to process
+** the WHERE clause of SQL statements.  This module is responsible for
+** generating the code that loops through a table looking for applicable
+** rows.  Indices are selected and used to speed the search when doing
+** so is applicable.  Because this module is responsible for selecting
+** indices, you might also think of this module as the "query optimizer".
 */
-static int whereEqualScanEst(
-  Parse *pParse,       /* Parsing & code generating context */
-  WhereLoopBuilder *pBuilder,
-  Expr *pExpr,         /* Expression for VALUE in the x=VALUE constraint */
-  tRowcnt *pnRow       /* Write the revised row estimate here */
-){
-  Index *p = pBuilder->pNew->u.btree.pIndex;
-  int nEq = pBuilder->pNew->u.btree.nEq;
-  UnpackedRecord *pRec = pBuilder->pRec;
-  u8 aff;                   /* Column affinity */
-  int rc;                   /* Subfunction return code */
-  tRowcnt a[2];             /* Statistics */
-  int bOk;
+/* #include "sqliteInt.h" */
+/* #include "whereInt.h" */
 
-  assert( nEq>=1 );
-  assert( nEq<=p->nColumn );
-  assert( p->aSample!=0 );
-  assert( p->nSample>0 );
-  assert( pBuilder->nRecValid<nEq );
+/* Forward declaration of methods */
+static int whereLoopResize(sqlite3*, WhereLoop*, int);
 
-  /* If values are not available for all fields of the index to the left
-  ** of this one, no estimate can be made. Return SQLITE_NOTFOUND. */
-  if( pBuilder->nRecValid<(nEq-1) ){
-    return SQLITE_NOTFOUND;
-  }
+/* Test variable that can be set to enable WHERE tracing */
+#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
+/***/ int sqlite3WhereTrace = 0;
+#endif
 
-  /* This is an optimization only. The call to sqlite3Stat4ProbeSetValue()
-  ** below would return the same value.  */
-  if( nEq>=p->nColumn ){
-    *pnRow = 1;
-    return SQLITE_OK;
-  }
 
-  aff = p->pTable->aCol[p->aiColumn[nEq-1]].affinity;
-  rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq-1, &bOk);
-  pBuilder->pRec = pRec;
-  if( rc!=SQLITE_OK ) return rc;
-  if( bOk==0 ) return SQLITE_NOTFOUND;
-  pBuilder->nRecValid = nEq;
+/*
+** Return the estimated number of output rows from a WHERE clause
+*/
+SQLITE_PRIVATE u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
+  return sqlite3LogEstToInt(pWInfo->nRowOut);
+}
 
-  whereKeyStats(pParse, p, pRec, 0, a);
-  WHERETRACE(0x10,("equality scan regions: %d\n", (int)a[1]));
-  *pnRow = a[1];
-  
-  return rc;
+/*
+** Return one of the WHERE_DISTINCT_xxxxx values to indicate how this
+** WHERE clause returns outputs for DISTINCT processing.
+*/
+SQLITE_PRIVATE int sqlite3WhereIsDistinct(WhereInfo *pWInfo){
+  return pWInfo->eDistinct;
 }
-#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
-#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
 /*
-** Estimate the number of rows that will be returned based on
-** an IN constraint where the right-hand side of the IN operator
-** is a list of values.  Example:
-**
-**        WHERE x IN (1,2,3,4)
-**
-** Write the estimated row count into *pnRow and return SQLITE_OK. 
-** If unable to make an estimate, leave *pnRow unchanged and return
-** non-zero.
-**
-** This routine can fail if it is unable to load a collating sequence
-** required for string comparison, or if unable to allocate memory
-** for a UTF conversion required for comparison.  The error is stored
-** in the pParse structure.
+** Return TRUE if the WHERE clause returns rows in ORDER BY order.
+** Return FALSE if the output needs to be sorted.
 */
-static int whereInScanEst(
-  Parse *pParse,       /* Parsing & code generating context */
-  WhereLoopBuilder *pBuilder,
-  ExprList *pList,     /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
-  tRowcnt *pnRow       /* Write the revised row estimate here */
-){
-  Index *p = pBuilder->pNew->u.btree.pIndex;
-  i64 nRow0 = sqlite3LogEstToInt(p->aiRowLogEst[0]);
-  int nRecValid = pBuilder->nRecValid;
-  int rc = SQLITE_OK;     /* Subfunction return code */
-  tRowcnt nEst;           /* Number of rows for a single term */
-  tRowcnt nRowEst = 0;    /* New estimate of the number of rows */
-  int i;                  /* Loop counter */
+SQLITE_PRIVATE int sqlite3WhereIsOrdered(WhereInfo *pWInfo){
+  return pWInfo->nOBSat;
+}
 
-  assert( p->aSample!=0 );
-  for(i=0; rc==SQLITE_OK && i<pList->nExpr; i++){
-    nEst = nRow0;
-    rc = whereEqualScanEst(pParse, pBuilder, pList->a[i].pExpr, &nEst);
-    nRowEst += nEst;
-    pBuilder->nRecValid = nRecValid;
-  }
+/*
+** Return the VDBE address or label to jump to in order to continue
+** immediately with the next row of a WHERE clause.
+*/
+SQLITE_PRIVATE int sqlite3WhereContinueLabel(WhereInfo *pWInfo){
+  assert( pWInfo->iContinue!=0 );
+  return pWInfo->iContinue;
+}
 
-  if( rc==SQLITE_OK ){
-    if( nRowEst > nRow0 ) nRowEst = nRow0;
-    *pnRow = nRowEst;
-    WHERETRACE(0x10,("IN row estimate: est=%d\n", nRowEst));
-  }
-  assert( pBuilder->nRecValid==nRecValid );
-  return rc;
+/*
+** Return the VDBE address or label to jump to in order to break
+** out of a WHERE loop.
+*/
+SQLITE_PRIVATE int sqlite3WhereBreakLabel(WhereInfo *pWInfo){
+  return pWInfo->iBreak;
 }
-#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
 /*
-** Disable a term in the WHERE clause.  Except, do not disable the term
-** if it controls a LEFT OUTER JOIN and it did not originate in the ON
-** or USING clause of that join.
-**
-** Consider the term t2.z='ok' in the following queries:
-**
-**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
-**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
-**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
-**
-** The t2.z='ok' is disabled in the in (2) because it originates
-** in the ON clause.  The term is disabled in (3) because it is not part
-** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
-**
-** Disabling a term causes that term to not be tested in the inner loop
-** of the join.  Disabling is an optimization.  When terms are satisfied
-** by indices, we disable them to prevent redundant tests in the inner
-** loop.  We would get the correct results if nothing were ever disabled,
-** but joins might run a little slower.  The trick is to disable as much
-** as we can without disabling too much.  If we disabled in (1), we'd get
-** the wrong answer.  See ticket #813.
-**
-** If all the children of a term are disabled, then that term is also
-** automatically disabled.  In this way, terms get disabled if derived
-** virtual terms are tested first.  For example:
-**
-**      x GLOB 'abc*' AND x>='abc' AND x<'acd'
-**      \___________/     \______/     \_____/
-**         parent          child1       child2
+** Return TRUE if an UPDATE or DELETE statement can operate directly on
+** the rowids returned by a WHERE clause.  Return FALSE if doing an
+** UPDATE or DELETE might change subsequent WHERE clause results.
 **
-** Only the parent term was in the original WHERE clause.  The child1
-** and child2 terms were added by the LIKE optimization.  If both of
-** the virtual child terms are valid, then testing of the parent can be 
-** skipped.
+** If the ONEPASS optimization is used (if this routine returns true)
+** then also write the indices of open cursors used by ONEPASS
+** into aiCur[0] and aiCur[1].  iaCur[0] gets the cursor of the data
+** table and iaCur[1] gets the cursor used by an auxiliary index.
+** Either value may be -1, indicating that cursor is not used.
+** Any cursors returned will have been opened for writing.
 **
-** Usually the parent term is marked as TERM_CODED.  But if the parent
-** term was originally TERM_LIKE, then the parent gets TERM_LIKECOND instead.
-** The TERM_LIKECOND marking indicates that the term should be coded inside
-** a conditional such that is only evaluated on the second pass of a
-** LIKE-optimization loop, when scanning BLOBs instead of strings.
+** aiCur[0] and aiCur[1] both get -1 if the where-clause logic is
+** unable to use the ONEPASS optimization.
 */
-static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
-  int nLoop = 0;
-  while( pTerm
-      && (pTerm->wtFlags & TERM_CODED)==0
-      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
-      && (pLevel->notReady & pTerm->prereqAll)==0
-  ){
-    if( nLoop && (pTerm->wtFlags & TERM_LIKE)!=0 ){
-      pTerm->wtFlags |= TERM_LIKECOND;
-    }else{
-      pTerm->wtFlags |= TERM_CODED;
-    }
-    if( pTerm->iParent<0 ) break;
-    pTerm = &pTerm->pWC->a[pTerm->iParent];
-    pTerm->nChild--;
-    if( pTerm->nChild!=0 ) break;
-    nLoop++;
-  }
+SQLITE_PRIVATE int sqlite3WhereOkOnePass(WhereInfo *pWInfo, int *aiCur){
+  memcpy(aiCur, pWInfo->aiCurOnePass, sizeof(int)*2);
+  return pWInfo->okOnePass;
 }
 
 /*
-** Code an OP_Affinity opcode to apply the column affinity string zAff
-** to the n registers starting at base. 
-**
-** As an optimization, SQLITE_AFF_NONE entries (which are no-ops) at the
-** beginning and end of zAff are ignored.  If all entries in zAff are
-** SQLITE_AFF_NONE, then no code gets generated.
-**
-** This routine makes its own copy of zAff so that the caller is free
-** to modify zAff after this routine returns.
+** Move the content of pSrc into pDest
 */
-static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
-  Vdbe *v = pParse->pVdbe;
-  if( zAff==0 ){
-    assert( pParse->db->mallocFailed );
-    return;
-  }
-  assert( v!=0 );
+static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
+  pDest->n = pSrc->n;
+  memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
+}
 
-  /* Adjust base and n to skip over SQLITE_AFF_NONE entries at the beginning
-  ** and end of the affinity string.
-  */
-  while( n>0 && zAff[0]==SQLITE_AFF_NONE ){
-    n--;
-    base++;
-    zAff++;
+/*
+** Try to insert a new prerequisite/cost entry into the WhereOrSet pSet.
+**
+** The new entry might overwrite an existing entry, or it might be
+** appended, or it might be discarded.  Do whatever is the right thing
+** so that pSet keeps the N_OR_COST best entries seen so far.
+*/
+static int whereOrInsert(
+  WhereOrSet *pSet,      /* The WhereOrSet to be updated */
+  Bitmask prereq,        /* Prerequisites of the new entry */
+  LogEst rRun,           /* Run-cost of the new entry */
+  LogEst nOut            /* Number of outputs for the new entry */
+){
+  u16 i;
+  WhereOrCost *p;
+  for(i=pSet->n, p=pSet->a; i>0; i--, p++){
+    if( rRun<=p->rRun && (prereq & p->prereq)==prereq ){
+      goto whereOrInsert_done;
+    }
+    if( p->rRun<=rRun && (p->prereq & prereq)==p->prereq ){
+      return 0;
+    }
   }
-  while( n>1 && zAff[n-1]==SQLITE_AFF_NONE ){
-    n--;
+  if( pSet->n<N_OR_COST ){
+    p = &pSet->a[pSet->n++];
+    p->nOut = nOut;
+  }else{
+    p = pSet->a;
+    for(i=1; i<pSet->n; i++){
+      if( p->rRun>pSet->a[i].rRun ) p = pSet->a + i;
+    }
+    if( p->rRun<=rRun ) return 0;
   }
+whereOrInsert_done:
+  p->prereq = prereq;
+  p->rRun = rRun;
+  if( p->nOut>nOut ) p->nOut = nOut;
+  return 1;
+}
 
-  /* Code the OP_Affinity opcode if there is anything left to do. */
-  if( n>0 ){
-    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
-    sqlite3VdbeChangeP4(v, -1, zAff, n);
-    sqlite3ExprCacheAffinityChange(pParse, base, n);
+/*
+** Return the bitmask for the given cursor number.  Return 0 if
+** iCursor is not in the set.
+*/
+SQLITE_PRIVATE Bitmask sqlite3WhereGetMask(WhereMaskSet *pMaskSet, int iCursor){
+  int i;
+  assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
+  for(i=0; i<pMaskSet->n; i++){
+    if( pMaskSet->ix[i]==iCursor ){
+      return MASKBIT(i);
+    }
   }
+  return 0;
 }
 
-
 /*
-** Generate code for a single equality term of the WHERE clause.  An equality
-** term can be either X=expr or X IN (...).   pTerm is the term to be 
-** coded.
-**
-** The current value for the constraint is left in register iReg.
+** Create a new mask for cursor iCursor.
 **
-** For a constraint of the form X=expr, the expression is evaluated and its
-** result is left on the stack.  For constraints of the form X IN (...)
-** this routine sets up a loop that will iterate over all values of X.
+** There is one cursor per table in the FROM clause.  The number of
+** tables in the FROM clause is limited by a test early in the
+** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
+** array will never overflow.
 */
-static int codeEqualityTerm(
-  Parse *pParse,      /* The parsing context */
-  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
-  WhereLevel *pLevel, /* The level of the FROM clause we are working on */
-  int iEq,            /* Index of the equality term within this level */
-  int bRev,           /* True for reverse-order IN operations */
-  int iTarget         /* Attempt to leave results in this register */
-){
-  Expr *pX = pTerm->pExpr;
-  Vdbe *v = pParse->pVdbe;
-  int iReg;                  /* Register holding results */
+static void createMask(WhereMaskSet *pMaskSet, int iCursor){
+  assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
+  pMaskSet->ix[pMaskSet->n++] = iCursor;
+}
 
-  assert( iTarget>0 );
-  if( pX->op==TK_EQ ){
-    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
-  }else if( pX->op==TK_ISNULL ){
-    iReg = iTarget;
-    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
-#ifndef SQLITE_OMIT_SUBQUERY
-  }else{
-    int eType;
-    int iTab;
-    struct InLoop *pIn;
-    WhereLoop *pLoop = pLevel->pWLoop;
+/*
+** Advance to the next WhereTerm that matches according to the criteria
+** established when the pScan object was initialized by whereScanInit().
+** Return NULL if there are no more matching WhereTerms.
+*/
+static WhereTerm *whereScanNext(WhereScan *pScan){
+  int iCur;            /* The cursor on the LHS of the term */
+  int iColumn;         /* The column on the LHS of the term.  -1 for IPK */
+  Expr *pX;            /* An expression being tested */
+  WhereClause *pWC;    /* Shorthand for pScan->pWC */
+  WhereTerm *pTerm;    /* The term being tested */
+  int k = pScan->k;    /* Where to start scanning */
 
-    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
-      && pLoop->u.btree.pIndex!=0
-      && pLoop->u.btree.pIndex->aSortOrder[iEq]
-    ){
-      testcase( iEq==0 );
-      testcase( bRev );
-      bRev = !bRev;
-    }
-    assert( pX->op==TK_IN );
-    iReg = iTarget;
-    eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0);
-    if( eType==IN_INDEX_INDEX_DESC ){
-      testcase( bRev );
-      bRev = !bRev;
-    }
-    iTab = pX->iTable;
-    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
-    VdbeCoverageIf(v, bRev);
-    VdbeCoverageIf(v, !bRev);
-    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
-    pLoop->wsFlags |= WHERE_IN_ABLE;
-    if( pLevel->u.in.nIn==0 ){
-      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
-    }
-    pLevel->u.in.nIn++;
-    pLevel->u.in.aInLoop =
-       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
-                              sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
-    pIn = pLevel->u.in.aInLoop;
-    if( pIn ){
-      pIn += pLevel->u.in.nIn - 1;
-      pIn->iCur = iTab;
-      if( eType==IN_INDEX_ROWID ){
-        pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
-      }else{
-        pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
+  while( pScan->iEquiv<=pScan->nEquiv ){
+    iCur = pScan->aEquiv[pScan->iEquiv-2];
+    iColumn = pScan->aEquiv[pScan->iEquiv-1];
+    while( (pWC = pScan->pWC)!=0 ){
+      for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
+        if( pTerm->leftCursor==iCur
+         && pTerm->u.leftColumn==iColumn
+         && (pScan->iEquiv<=2 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
+        ){
+          if( (pTerm->eOperator & WO_EQUIV)!=0
+           && pScan->nEquiv<ArraySize(pScan->aEquiv)
+          ){
+            int j;
+            pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight);
+            assert( pX->op==TK_COLUMN );
+            for(j=0; j<pScan->nEquiv; j+=2){
+              if( pScan->aEquiv[j]==pX->iTable
+               && pScan->aEquiv[j+1]==pX->iColumn ){
+                  break;
+              }
+            }
+            if( j==pScan->nEquiv ){
+              pScan->aEquiv[j] = pX->iTable;
+              pScan->aEquiv[j+1] = pX->iColumn;
+              pScan->nEquiv += 2;
+            }
+          }
+          if( (pTerm->eOperator & pScan->opMask)!=0 ){
+            /* Verify the affinity and collating sequence match */
+            if( pScan->zCollName && (pTerm->eOperator & WO_ISNULL)==0 ){
+              CollSeq *pColl;
+              Parse *pParse = pWC->pWInfo->pParse;
+              pX = pTerm->pExpr;
+              if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
+                continue;
+              }
+              assert(pX->pLeft);
+              pColl = sqlite3BinaryCompareCollSeq(pParse,
+                                                  pX->pLeft, pX->pRight);
+              if( pColl==0 ) pColl = pParse->db->pDfltColl;
+              if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
+                continue;
+              }
+            }
+            if( (pTerm->eOperator & (WO_EQ|WO_IS))!=0
+             && (pX = pTerm->pExpr->pRight)->op==TK_COLUMN
+             && pX->iTable==pScan->aEquiv[0]
+             && pX->iColumn==pScan->aEquiv[1]
+            ){
+              testcase( pTerm->eOperator & WO_IS );
+              continue;
+            }
+            pScan->k = k+1;
+            return pTerm;
+          }
+        }
       }
-      pIn->eEndLoopOp = bRev ? OP_PrevIfOpen : OP_NextIfOpen;
-      sqlite3VdbeAddOp1(v, OP_IsNull, iReg); VdbeCoverage(v);
-    }else{
-      pLevel->u.in.nIn = 0;
+      pScan->pWC = pScan->pWC->pOuter;
+      k = 0;
     }
-#endif
+    pScan->pWC = pScan->pOrigWC;
+    k = 0;
+    pScan->iEquiv += 2;
   }
-  disableTerm(pLevel, pTerm);
-  return iReg;
+  return 0;
 }
 
 /*
-** Generate code that will evaluate all == and IN constraints for an
-** index scan.
-**
-** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
-** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
-** The index has as many as three equality constraints, but in this
-** example, the third "c" value is an inequality.  So only two 
-** constraints are coded.  This routine will generate code to evaluate
-** a==5 and b IN (1,2,3).  The current values for a and b will be stored
-** in consecutive registers and the index of the first register is returned.
-**
-** In the example above nEq==2.  But this subroutine works for any value
-** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
-** The only thing it does is allocate the pLevel->iMem memory cell and
-** compute the affinity string.
-**
-** The nExtraReg parameter is 0 or 1.  It is 0 if all WHERE clause constraints
-** are == or IN and are covered by the nEq.  nExtraReg is 1 if there is
-** an inequality constraint (such as the "c>=5 AND c<10" in the example) that
-** occurs after the nEq quality constraints.
-**
-** This routine allocates a range of nEq+nExtraReg memory cells and returns
-** the index of the first memory cell in that range. The code that
-** calls this routine will use that memory range to store keys for
-** start and termination conditions of the loop.
-** key value of the loop.  If one or more IN operators appear, then
-** this routine allocates an additional nEq memory cells for internal
-** use.
+** Initialize a WHERE clause scanner object.  Return a pointer to the
+** first match.  Return NULL if there are no matches.
 **
-** Before returning, *pzAff is set to point to a buffer containing a
-** copy of the column affinity string of the index allocated using
-** sqlite3DbMalloc(). Except, entries in the copy of the string associated
-** with equality constraints that use NONE affinity are set to
-** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
+** The scanner will be searching the WHERE clause pWC.  It will look
+** for terms of the form "X <op> <expr>" where X is column iColumn of table
+** iCur.  The <op> must be one of the operators described by opMask.
 **
-**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
-**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
+** If the search is for X and the WHERE clause contains terms of the
+** form X=Y then this routine might also return terms of the form
+** "Y <op> <expr>".  The number of levels of transitivity is limited,
+** but is enough to handle most commonly occurring SQL statements.
 **
-** In the example above, the index on t1(a) has TEXT affinity. But since
-** the right hand side of the equality constraint (t2.b) has NONE affinity,
-** no conversion should be attempted before using a t2.b value as part of
-** a key to search the index. Hence the first byte in the returned affinity
-** string in this example would be set to SQLITE_AFF_NONE.
+** If X is not the INTEGER PRIMARY KEY then X must be compatible with
+** index pIdx.
 */
-static int codeAllEqualityTerms(
-  Parse *pParse,        /* Parsing context */
-  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
-  int bRev,             /* Reverse the order of IN operators */
-  int nExtraReg,        /* Number of extra registers to allocate */
-  char **pzAff          /* OUT: Set to point to affinity string */
+static WhereTerm *whereScanInit(
+  WhereScan *pScan,       /* The WhereScan object being initialized */
+  WhereClause *pWC,       /* The WHERE clause to be scanned */
+  int iCur,               /* Cursor to scan for */
+  int iColumn,            /* Column to scan for */
+  u32 opMask,             /* Operator(s) to scan for */
+  Index *pIdx             /* Must be compatible with this index */
 ){
-  u16 nEq;                      /* The number of == or IN constraints to code */
-  u16 nSkip;                    /* Number of left-most columns to skip */
-  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
-  Index *pIdx;                  /* The index being used for this loop */
-  WhereTerm *pTerm;             /* A single constraint term */
-  WhereLoop *pLoop;             /* The WhereLoop object */
-  int j;                        /* Loop counter */
-  int regBase;                  /* Base register */
-  int nReg;                     /* Number of registers to allocate */
-  char *zAff;                   /* Affinity string to return */
-
-  /* This module is only called on query plans that use an index. */
-  pLoop = pLevel->pWLoop;
-  assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
-  nEq = pLoop->u.btree.nEq;
-  nSkip = pLoop->nSkip;
-  pIdx = pLoop->u.btree.pIndex;
-  assert( pIdx!=0 );
-
-  /* Figure out how many memory cells we will need then allocate them.
-  */
-  regBase = pParse->nMem + 1;
-  nReg = pLoop->u.btree.nEq + nExtraReg;
-  pParse->nMem += nReg;
-
-  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
-  if( !zAff ){
-    pParse->db->mallocFailed = 1;
-  }
-
-  if( nSkip ){
-    int iIdxCur = pLevel->iIdxCur;
-    sqlite3VdbeAddOp1(v, (bRev?OP_Last:OP_Rewind), iIdxCur);
-    VdbeCoverageIf(v, bRev==0);
-    VdbeCoverageIf(v, bRev!=0);
-    VdbeComment((v, "begin skip-scan on %s", pIdx->zName));
-    j = sqlite3VdbeAddOp0(v, OP_Goto);
-    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
-                            iIdxCur, 0, regBase, nSkip);
-    VdbeCoverageIf(v, bRev==0);
-    VdbeCoverageIf(v, bRev!=0);
-    sqlite3VdbeJumpHere(v, j);
-    for(j=0; j<nSkip; j++){
-      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
-      assert( pIdx->aiColumn[j]>=0 );
-      VdbeComment((v, "%s", pIdx->pTable->aCol[pIdx->aiColumn[j]].zName));
-    }
-  }    
+  int j;
 
-  /* Evaluate the equality constraints
-  */
-  assert( zAff==0 || (int)strlen(zAff)>=nEq );
-  for(j=nSkip; j<nEq; j++){
-    int r1;
-    pTerm = pLoop->aLTerm[j];
-    assert( pTerm!=0 );
-    /* The following testcase is true for indices with redundant columns. 
-    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
-    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
-    testcase( pTerm->wtFlags & TERM_VIRTUAL );
-    r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
-    if( r1!=regBase+j ){
-      if( nReg==1 ){
-        sqlite3ReleaseTempReg(pParse, regBase);
-        regBase = r1;
-      }else{
-        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
-      }
-    }
-    testcase( pTerm->eOperator & WO_ISNULL );
-    testcase( pTerm->eOperator & WO_IN );
-    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
-      Expr *pRight = pTerm->pExpr->pRight;
-      if( sqlite3ExprCanBeNull(pRight) ){
-        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
-        VdbeCoverage(v);
-      }
-      if( zAff ){
-        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
-          zAff[j] = SQLITE_AFF_NONE;
-        }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
-          zAff[j] = SQLITE_AFF_NONE;
-        }
-      }
+  /* memset(pScan, 0, sizeof(*pScan)); */
+  pScan->pOrigWC = pWC;
+  pScan->pWC = pWC;
+  if( pIdx && iColumn>=0 ){
+    pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
+    for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
+      if( NEVER(j>pIdx->nColumn) ) return 0;
     }
+    pScan->zCollName = pIdx->azColl[j];
+  }else{
+    pScan->idxaff = 0;
+    pScan->zCollName = 0;
   }
-  *pzAff = zAff;
-  return regBase;
+  pScan->opMask = opMask;
+  pScan->k = 0;
+  pScan->aEquiv[0] = iCur;
+  pScan->aEquiv[1] = iColumn;
+  pScan->nEquiv = 2;
+  pScan->iEquiv = 2;
+  return whereScanNext(pScan);
 }
 
-#ifndef SQLITE_OMIT_EXPLAIN
 /*
-** This routine is a helper for explainIndexRange() below
+** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
+** where X is a reference to the iColumn of table iCur and <op> is one of
+** the WO_xx operator codes specified by the op parameter.
+** Return a pointer to the term.  Return 0 if not found.
 **
-** pStr holds the text of an expression that we are building up one term
-** at a time.  This routine adds a new term to the end of the expression.
-** Terms are separated by AND so add the "AND" text for second and subsequent
-** terms only.
+** The term returned might by Y=<expr> if there is another constraint in
+** the WHERE clause that specifies that X=Y.  Any such constraints will be
+** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
+** aEquiv[] array holds X and all its equivalents, with each SQL variable
+** taking up two slots in aEquiv[].  The first slot is for the cursor number
+** and the second is for the column number.  There are 22 slots in aEquiv[]
+** so that means we can look for X plus up to 10 other equivalent values.
+** Hence a search for X will return <expr> if X=A1 and A1=A2 and A2=A3
+** and ... and A9=A10 and A10=<expr>.
+**
+** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
+** then try for the one with no dependencies on <expr> - in other words where
+** <expr> is a constant expression of some kind.  Only return entries of
+** the form "X <op> Y" where Y is a column in another table if no terms of
+** the form "X <op> <const-expr>" exist.   If no terms with a constant RHS
+** exist, try to return a term that does not use WO_EQUIV.
 */
-static void explainAppendTerm(
-  StrAccum *pStr,             /* The text expression being built */
-  int iTerm,                  /* Index of this term.  First is zero */
-  const char *zColumn,        /* Name of the column */
-  const char *zOp             /* Name of the operator */
+SQLITE_PRIVATE WhereTerm *sqlite3WhereFindTerm(
+  WhereClause *pWC,     /* The WHERE clause to be searched */
+  int iCur,             /* Cursor number of LHS */
+  int iColumn,          /* Column number of LHS */
+  Bitmask notReady,     /* RHS must not overlap with this mask */
+  u32 op,               /* Mask of WO_xx values describing operator */
+  Index *pIdx           /* Must be compatible with this index, if not NULL */
 ){
-  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
-  sqlite3StrAccumAppendAll(pStr, zColumn);
-  sqlite3StrAccumAppend(pStr, zOp, 1);
-  sqlite3StrAccumAppend(pStr, "?", 1);
+  WhereTerm *pResult = 0;
+  WhereTerm *p;
+  WhereScan scan;
+
+  p = whereScanInit(&scan, pWC, iCur, iColumn, op, pIdx);
+  op &= WO_EQ|WO_IS;
+  while( p ){
+    if( (p->prereqRight & notReady)==0 ){
+      if( p->prereqRight==0 && (p->eOperator&op)!=0 ){
+        testcase( p->eOperator & WO_IS );
+        return p;
+      }
+      if( pResult==0 ) pResult = p;
+    }
+    p = whereScanNext(&scan);
+  }
+  return pResult;
 }
 
 /*
-** Argument pLevel describes a strategy for scanning table pTab. This 
-** function appends text to pStr that describes the subset of table
-** rows scanned by the strategy in the form of an SQL expression.
-**
-** For example, if the query:
-**
-**   SELECT * FROM t1 WHERE a=1 AND b>2;
-**
-** is run and there is an index on (a, b), then this function returns a
-** string similar to:
+** This function searches pList for an entry that matches the iCol-th column
+** of index pIdx.
 **
-**   "a=? AND b>?"
+** If such an expression is found, its index in pList->a[] is returned. If
+** no expression is found, -1 is returned.
 */
-static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop, Table *pTab){
-  Index *pIndex = pLoop->u.btree.pIndex;
-  u16 nEq = pLoop->u.btree.nEq;
-  u16 nSkip = pLoop->nSkip;
-  int i, j;
-  Column *aCol = pTab->aCol;
-  i16 *aiColumn = pIndex->aiColumn;
-
-  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
-  sqlite3StrAccumAppend(pStr, " (", 2);
-  for(i=0; i<nEq; i++){
-    char *z = aiColumn[i] < 0 ? "rowid" : aCol[aiColumn[i]].zName;
-    if( i>=nSkip ){
-      explainAppendTerm(pStr, i, z, "=");
-    }else{
-      if( i ) sqlite3StrAccumAppend(pStr, " AND ", 5);
-      sqlite3XPrintf(pStr, 0, "ANY(%s)", z);
+static int findIndexCol(
+  Parse *pParse,                  /* Parse context */
+  ExprList *pList,                /* Expression list to search */
+  int iBase,                      /* Cursor for table associated with pIdx */
+  Index *pIdx,                    /* Index to match column of */
+  int iCol                        /* Column of index to match */
+){
+  int i;
+  const char *zColl = pIdx->azColl[iCol];
+
+  for(i=0; i<pList->nExpr; i++){
+    Expr *p = sqlite3ExprSkipCollate(pList->a[i].pExpr);
+    if( p->op==TK_COLUMN
+     && p->iColumn==pIdx->aiColumn[iCol]
+     && p->iTable==iBase
+    ){
+      CollSeq *pColl = sqlite3ExprCollSeq(pParse, pList->a[i].pExpr);
+      if( pColl && 0==sqlite3StrICmp(pColl->zName, zColl) ){
+        return i;
+      }
     }
   }
 
-  j = i;
-  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
-    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
-    explainAppendTerm(pStr, i++, z, ">");
-  }
-  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
-    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
-    explainAppendTerm(pStr, i, z, "<");
-  }
-  sqlite3StrAccumAppend(pStr, ")", 1);
+  return -1;
 }
 
 /*
-** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
-** command, or if either SQLITE_DEBUG or SQLITE_ENABLE_STMT_SCANSTATUS was
-** defined at compile-time. If it is not a no-op, a single OP_Explain opcode 
-** is added to the output to describe the table scan strategy in pLevel.
+** Return true if the DISTINCT expression-list passed as the third argument
+** is redundant.
 **
-** If an OP_Explain opcode is added to the VM, its address is returned.
-** Otherwise, if no OP_Explain is coded, zero is returned.
+** A DISTINCT list is redundant if any subset of the columns in the
+** DISTINCT list are collectively unique and individually non-null.
 */
-static int explainOneScan(
-  Parse *pParse,                  /* Parse context */
-  SrcList *pTabList,              /* Table list this loop refers to */
-  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
-  int iLevel,                     /* Value for "level" column of output */
-  int iFrom,                      /* Value for "from" column of output */
-  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
+static int isDistinctRedundant(
+  Parse *pParse,            /* Parsing context */
+  SrcList *pTabList,        /* The FROM clause */
+  WhereClause *pWC,         /* The WHERE clause */
+  ExprList *pDistinct       /* The result set that needs to be DISTINCT */
 ){
-  int ret = 0;
-#if !defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_STMT_SCANSTATUS)
-  if( pParse->explain==2 )
-#endif
-  {
-    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
-    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
-    sqlite3 *db = pParse->db;     /* Database handle */
-    int iId = pParse->iSelectId;  /* Select id (left-most output column) */
-    int isSearch;                 /* True for a SEARCH. False for SCAN. */
-    WhereLoop *pLoop;             /* The controlling WhereLoop object */
-    u32 flags;                    /* Flags that describe this loop */
-    char *zMsg;                   /* Text to add to EQP output */
-    StrAccum str;                 /* EQP output string */
-    char zBuf[100];               /* Initial space for EQP output string */
-
-    pLoop = pLevel->pWLoop;
-    flags = pLoop->wsFlags;
-    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return 0;
-
-    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
-            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
-            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
+  Table *pTab;
+  Index *pIdx;
+  int i;                          
+  int iBase;
 
-    sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
-    sqlite3StrAccumAppendAll(&str, isSearch ? "SEARCH" : "SCAN");
-    if( pItem->pSelect ){
-      sqlite3XPrintf(&str, 0, " SUBQUERY %d", pItem->iSelectId);
-    }else{
-      sqlite3XPrintf(&str, 0, " TABLE %s", pItem->zName);
-    }
+  /* If there is more than one table or sub-select in the FROM clause of
+  ** this query, then it will not be possible to show that the DISTINCT 
+  ** clause is redundant. */
+  if( pTabList->nSrc!=1 ) return 0;
+  iBase = pTabList->a[0].iCursor;
+  pTab = pTabList->a[0].pTab;
 
-    if( pItem->zAlias ){
-      sqlite3XPrintf(&str, 0, " AS %s", pItem->zAlias);
-    }
-    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
-      const char *zFmt = 0;
-      Index *pIdx;
+  /* If any of the expressions is an IPK column on table iBase, then return 
+  ** true. Note: The (p->iTable==iBase) part of this test may be false if the
+  ** current SELECT is a correlated sub-query.
+  */
+  for(i=0; i<pDistinct->nExpr; i++){
+    Expr *p = sqlite3ExprSkipCollate(pDistinct->a[i].pExpr);
+    if( p->op==TK_COLUMN && p->iTable==iBase && p->iColumn<0 ) return 1;
+  }
 
-      assert( pLoop->u.btree.pIndex!=0 );
-      pIdx = pLoop->u.btree.pIndex;
-      assert( !(flags&WHERE_AUTO_INDEX) || (flags&WHERE_IDX_ONLY) );
-      if( !HasRowid(pItem->pTab) && IsPrimaryKeyIndex(pIdx) ){
-        if( isSearch ){
-          zFmt = "PRIMARY KEY";
+  /* Loop through all indices on the table, checking each to see if it makes
+  ** the DISTINCT qualifier redundant. It does so if:
+  **
+  **   1. The index is itself UNIQUE, and
+  **
+  **   2. All of the columns in the index are either part of the pDistinct
+  **      list, or else the WHERE clause contains a term of the form "col=X",
+  **      where X is a constant value. The collation sequences of the
+  **      comparison and select-list expressions must match those of the index.
+  **
+  **   3. All of those index columns for which the WHERE clause does not
+  **      contain a "col=X" term are subject to a NOT NULL constraint.
+  */
+  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+    if( !IsUniqueIndex(pIdx) ) continue;
+    for(i=0; i<pIdx->nKeyCol; i++){
+      i16 iCol = pIdx->aiColumn[i];
+      if( 0==sqlite3WhereFindTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) ){
+        int iIdxCol = findIndexCol(pParse, pDistinct, iBase, pIdx, i);
+        if( iIdxCol<0 || pTab->aCol[iCol].notNull==0 ){
+          break;
         }
-      }else if( flags & WHERE_PARTIALIDX ){
-        zFmt = "AUTOMATIC PARTIAL COVERING INDEX";
-      }else if( flags & WHERE_AUTO_INDEX ){
-        zFmt = "AUTOMATIC COVERING INDEX";
-      }else if( flags & WHERE_IDX_ONLY ){
-        zFmt = "COVERING INDEX %s";
-      }else{
-        zFmt = "INDEX %s";
-      }
-      if( zFmt ){
-        sqlite3StrAccumAppend(&str, " USING ", 7);
-        sqlite3XPrintf(&str, 0, zFmt, pIdx->zName);
-        explainIndexRange(&str, pLoop, pItem->pTab);
-      }
-    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
-      const char *zRange;
-      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
-        zRange = "(rowid=?)";
-      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
-        zRange = "(rowid>? AND rowid<?)";
-      }else if( flags&WHERE_BTM_LIMIT ){
-        zRange = "(rowid>?)";
-      }else{
-        assert( flags&WHERE_TOP_LIMIT);
-        zRange = "(rowid<?)";
       }
-      sqlite3StrAccumAppendAll(&str, " USING INTEGER PRIMARY KEY ");
-      sqlite3StrAccumAppendAll(&str, zRange);
-    }
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
-      sqlite3XPrintf(&str, 0, " VIRTUAL TABLE INDEX %d:%s",
-                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
     }
-#endif
-#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
-    if( pLoop->nOut>=10 ){
-      sqlite3XPrintf(&str, 0, " (~%llu rows)", sqlite3LogEstToInt(pLoop->nOut));
-    }else{
-      sqlite3StrAccumAppend(&str, " (~1 row)", 9);
+    if( i==pIdx->nKeyCol ){
+      /* This index implies that the DISTINCT qualifier is redundant. */
+      return 1;
     }
-#endif
-    zMsg = sqlite3StrAccumFinish(&str);
-    ret = sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg,P4_DYNAMIC);
   }
-  return ret;
+
+  return 0;
 }
-#else
-# define explainOneScan(u,v,w,x,y,z) 0
-#endif /* SQLITE_OMIT_EXPLAIN */
 
-#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+
 /*
-** Configure the VM passed as the first argument with an
-** sqlite3_stmt_scanstatus() entry corresponding to the scan used to 
-** implement level pLvl. Argument pSrclist is a pointer to the FROM 
-** clause that the scan reads data from.
+** Estimate the logarithm of the input value to base 2.
+*/
+static LogEst estLog(LogEst N){
+  return N<=10 ? 0 : sqlite3LogEst(N) - 33;
+}
+
+/*
+** Convert OP_Column opcodes to OP_Copy in previously generated code.
 **
-** If argument addrExplain is not 0, it must be the address of an 
-** OP_Explain instruction that describes the same loop.
+** This routine runs over generated VDBE code and translates OP_Column
+** opcodes into OP_Copy, and OP_Rowid into OP_Null, when the table is being
+** accessed via co-routine instead of via table lookup.
 */
-static void addScanStatus(
-  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
-  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
-  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
-  int addrExplain                 /* Address of OP_Explain (or 0) */
+static void translateColumnToCopy(
+  Vdbe *v,            /* The VDBE containing code to translate */
+  int iStart,         /* Translate from this opcode to the end */
+  int iTabCur,        /* OP_Column/OP_Rowid references to this table */
+  int iRegister       /* The first column is in this register */
 ){
-  const char *zObj = 0;
-  WhereLoop *pLoop = pLvl->pWLoop;
-  if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0  &&  pLoop->u.btree.pIndex!=0 ){
-    zObj = pLoop->u.btree.pIndex->zName;
-  }else{
-    zObj = pSrclist->a[pLvl->iFrom].zName;
+  VdbeOp *pOp = sqlite3VdbeGetOp(v, iStart);
+  int iEnd = sqlite3VdbeCurrentAddr(v);
+  for(; iStart<iEnd; iStart++, pOp++){
+    if( pOp->p1!=iTabCur ) continue;
+    if( pOp->opcode==OP_Column ){
+      pOp->opcode = OP_Copy;
+      pOp->p1 = pOp->p2 + iRegister;
+      pOp->p2 = pOp->p3;
+      pOp->p3 = 0;
+    }else if( pOp->opcode==OP_Rowid ){
+      pOp->opcode = OP_Null;
+      pOp->p1 = 0;
+      pOp->p3 = 0;
+    }
   }
-  sqlite3VdbeScanStatus(
-      v, addrExplain, pLvl->addrBody, pLvl->addrVisit, pLoop->nOut, zObj
-  );
+}
+
+/*
+** Two routines for printing the content of an sqlite3_index_info
+** structure.  Used for testing and debugging only.  If neither
+** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
+** are no-ops.
+*/
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(WHERETRACE_ENABLED)
+static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
+  int i;
+  if( !sqlite3WhereTrace ) return;
+  for(i=0; i<p->nConstraint; i++){
+    sqlite3DebugPrintf("  constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
+       i,
+       p->aConstraint[i].iColumn,
+       p->aConstraint[i].iTermOffset,
+       p->aConstraint[i].op,
+       p->aConstraint[i].usable);
+  }
+  for(i=0; i<p->nOrderBy; i++){
+    sqlite3DebugPrintf("  orderby[%d]: col=%d desc=%d\n",
+       i,
+       p->aOrderBy[i].iColumn,
+       p->aOrderBy[i].desc);
+  }
+}
+static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
+  int i;
+  if( !sqlite3WhereTrace ) return;
+  for(i=0; i<p->nConstraint; i++){
+    sqlite3DebugPrintf("  usage[%d]: argvIdx=%d omit=%d\n",
+       i,
+       p->aConstraintUsage[i].argvIndex,
+       p->aConstraintUsage[i].omit);
+  }
+  sqlite3DebugPrintf("  idxNum=%d\n", p->idxNum);
+  sqlite3DebugPrintf("  idxStr=%s\n", p->idxStr);
+  sqlite3DebugPrintf("  orderByConsumed=%d\n", p->orderByConsumed);
+  sqlite3DebugPrintf("  estimatedCost=%g\n", p->estimatedCost);
+  sqlite3DebugPrintf("  estimatedRows=%lld\n", p->estimatedRows);
 }
 #else
-# define addScanStatus(a, b, c, d) ((void)d)
+#define TRACE_IDX_INPUTS(A)
+#define TRACE_IDX_OUTPUTS(A)
 #endif
 
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
 /*
-** If the most recently coded instruction is a constant range contraint
-** that originated from the LIKE optimization, then change the P3 to be
-** pLoop->iLikeRepCntr and set P5.
-**
-** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
-** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
-** scan loop run twice, once for strings and a second time for BLOBs.
-** The OP_String opcodes on the second pass convert the upper and lower
-** bound string contants to blobs.  This routine makes the necessary changes
-** to the OP_String opcodes for that to happen.
+** Return TRUE if the WHERE clause term pTerm is of a form where it
+** could be used with an index to access pSrc, assuming an appropriate
+** index existed.
 */
-static void whereLikeOptimizationStringFixup(
-  Vdbe *v,                /* prepared statement under construction */
-  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
-  WhereTerm *pTerm        /* The upper or lower bound just coded */
+static int termCanDriveIndex(
+  WhereTerm *pTerm,              /* WHERE clause term to check */
+  struct SrcList_item *pSrc,     /* Table we are trying to access */
+  Bitmask notReady               /* Tables in outer loops of the join */
 ){
-  if( pTerm->wtFlags & TERM_LIKEOPT ){
-    VdbeOp *pOp;
-    assert( pLevel->iLikeRepCntr>0 );
-    pOp = sqlite3VdbeGetOp(v, -1);
-    assert( pOp!=0 );
-    assert( pOp->opcode==OP_String8 
-            || pTerm->pWC->pWInfo->pParse->db->mallocFailed );
-    pOp->p3 = pLevel->iLikeRepCntr;
-    pOp->p5 = 1;
-  }
+  char aff;
+  if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
+  if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) return 0;
+  if( (pTerm->prereqRight & notReady)!=0 ) return 0;
+  if( pTerm->u.leftColumn<0 ) return 0;
+  aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
+  if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
+  testcase( pTerm->pExpr->op==TK_IS );
+  return 1;
 }
+#endif
+
 
+#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
 /*
-** Generate code for the start of the iLevel-th loop in the WHERE clause
-** implementation described by pWInfo.
+** Generate code to construct the Index object for an automatic index
+** and to set up the WhereLevel object pLevel so that the code generator
+** makes use of the automatic index.
 */
-static Bitmask codeOneLoopStart(
-  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
-  int iLevel,          /* Which level of pWInfo->a[] should be coded */
-  Bitmask notReady     /* Which tables are currently available */
+static void constructAutomaticIndex(
+  Parse *pParse,              /* The parsing context */
+  WhereClause *pWC,           /* The WHERE clause */
+  struct SrcList_item *pSrc,  /* The FROM clause term to get the next index */
+  Bitmask notReady,           /* Mask of cursors that are not available */
+  WhereLevel *pLevel          /* Write new index here */
 ){
-  int j, k;            /* Loop counters */
-  int iCur;            /* The VDBE cursor for the table */
-  int addrNxt;         /* Where to jump to continue with the next IN case */
-  int omitTable;       /* True if we use the index only */
-  int bRev;            /* True if we need to scan in reverse order */
-  WhereLevel *pLevel;  /* The where level to be coded */
-  WhereLoop *pLoop;    /* The WhereLoop object being coded */
-  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
-  WhereTerm *pTerm;               /* A WHERE clause term */
-  Parse *pParse;                  /* Parsing context */
-  sqlite3 *db;                    /* Database connection */
-  Vdbe *v;                        /* The prepared stmt under constructions */
-  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
-  int addrBrk;                    /* Jump here to break out of the loop */
-  int addrCont;                   /* Jump here to continue with next cycle */
-  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
-  int iReleaseReg = 0;      /* Temp register to free before returning */
+  int nKeyCol;                /* Number of columns in the constructed index */
+  WhereTerm *pTerm;           /* A single term of the WHERE clause */
+  WhereTerm *pWCEnd;          /* End of pWC->a[] */
+  Index *pIdx;                /* Object describing the transient index */
+  Vdbe *v;                    /* Prepared statement under construction */
+  int addrInit;               /* Address of the initialization bypass jump */
+  Table *pTable;              /* The table being indexed */
+  int addrTop;                /* Top of the index fill loop */
+  int regRecord;              /* Register holding an index record */
+  int n;                      /* Column counter */
+  int i;                      /* Loop counter */
+  int mxBitCol;               /* Maximum column in pSrc->colUsed */
+  CollSeq *pColl;             /* Collating sequence to on a column */
+  WhereLoop *pLoop;           /* The Loop object */
+  char *zNotUsed;             /* Extra space on the end of pIdx */
+  Bitmask idxCols;            /* Bitmap of columns used for indexing */
+  Bitmask extraCols;          /* Bitmap of additional columns */
+  u8 sentWarning = 0;         /* True if a warnning has been issued */
+  Expr *pPartial = 0;         /* Partial Index Expression */
+  int iContinue = 0;          /* Jump here to skip excluded rows */
+  struct SrcList_item *pTabItem;  /* FROM clause term being indexed */
 
-  pParse = pWInfo->pParse;
+  /* Generate code to skip over the creation and initialization of the
+  ** transient index on 2nd and subsequent iterations of the loop. */
   v = pParse->pVdbe;
-  pWC = &pWInfo->sWC;
-  db = pParse->db;
-  pLevel = &pWInfo->a[iLevel];
+  assert( v!=0 );
+  addrInit = sqlite3CodeOnce(pParse); VdbeCoverage(v);
+
+  /* Count the number of columns that will be added to the index
+  ** and used to match WHERE clause constraints */
+  nKeyCol = 0;
+  pTable = pSrc->pTab;
+  pWCEnd = &pWC->a[pWC->nTerm];
   pLoop = pLevel->pWLoop;
-  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
-  iCur = pTabItem->iCursor;
-  pLevel->notReady = notReady & ~getMask(&pWInfo->sMaskSet, iCur);
-  bRev = (pWInfo->revMask>>iLevel)&1;
-  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
-           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
-  VdbeModuleComment((v, "Begin WHERE-loop%d: %s",iLevel,pTabItem->pTab->zName));
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    Expr *pExpr = pTerm->pExpr;
+    assert( !ExprHasProperty(pExpr, EP_FromJoin)    /* prereq always non-zero */
+         || pExpr->iRightJoinTable!=pSrc->iCursor   /*   for the right-hand   */
+         || pLoop->prereq!=0 );                     /*   table of a LEFT JOIN */
+    if( pLoop->prereq==0
+     && (pTerm->wtFlags & TERM_VIRTUAL)==0
+     && !ExprHasProperty(pExpr, EP_FromJoin)
+     && sqlite3ExprIsTableConstant(pExpr, pSrc->iCursor) ){
+      pPartial = sqlite3ExprAnd(pParse->db, pPartial,
+                                sqlite3ExprDup(pParse->db, pExpr, 0));
+    }
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
+      testcase( iCol==BMS );
+      testcase( iCol==BMS-1 );
+      if( !sentWarning ){
+        sqlite3_log(SQLITE_WARNING_AUTOINDEX,
+            "automatic index on %s(%s)", pTable->zName,
+            pTable->aCol[iCol].zName);
+        sentWarning = 1;
+      }
+      if( (idxCols & cMask)==0 ){
+        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ){
+          goto end_auto_index_create;
+        }
+        pLoop->aLTerm[nKeyCol++] = pTerm;
+        idxCols |= cMask;
+      }
+    }
+  }
+  assert( nKeyCol>0 );
+  pLoop->u.btree.nEq = pLoop->nLTerm = nKeyCol;
+  pLoop->wsFlags = WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WHERE_INDEXED
+                     | WHERE_AUTO_INDEX;
 
-  /* Create labels for the "break" and "continue" instructions
-  ** for the current loop.  Jump to addrBrk to break out of a loop.
-  ** Jump to cont to go immediately to the next iteration of the
-  ** loop.
-  **
-  ** When there is an IN operator, we also have a "addrNxt" label that
-  ** means to continue with the next IN value combination.  When
-  ** there are no IN operators in the constraints, the "addrNxt" label
-  ** is the same as "addrBrk".
+  /* Count the number of additional columns needed to create a
+  ** covering index.  A "covering index" is an index that contains all
+  ** columns that are needed by the query.  With a covering index, the
+  ** original table never needs to be accessed.  Automatic indices must
+  ** be a covering index because the index will not be updated if the
+  ** original table changes and the index and table cannot both be used
+  ** if they go out of sync.
   */
-  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
-  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
+  extraCols = pSrc->colUsed & (~idxCols | MASKBIT(BMS-1));
+  mxBitCol = MIN(BMS-1,pTable->nCol);
+  testcase( pTable->nCol==BMS-1 );
+  testcase( pTable->nCol==BMS-2 );
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & MASKBIT(i) ) nKeyCol++;
+  }
+  if( pSrc->colUsed & MASKBIT(BMS-1) ){
+    nKeyCol += pTable->nCol - BMS + 1;
+  }
 
-  /* If this is the right table of a LEFT OUTER JOIN, allocate and
-  ** initialize a memory cell that records if this table matches any
-  ** row of the left table of the join.
-  */
-  if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
-    pLevel->iLeftJoin = ++pParse->nMem;
-    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
-    VdbeComment((v, "init LEFT JOIN no-match flag"));
+  /* Construct the Index object to describe this index */
+  pIdx = sqlite3AllocateIndexObject(pParse->db, nKeyCol+1, 0, &zNotUsed);
+  if( pIdx==0 ) goto end_auto_index_create;
+  pLoop->u.btree.pIndex = pIdx;
+  pIdx->zName = "auto-index";
+  pIdx->pTable = pTable;
+  n = 0;
+  idxCols = 0;
+  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( termCanDriveIndex(pTerm, pSrc, notReady) ){
+      int iCol = pTerm->u.leftColumn;
+      Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
+      testcase( iCol==BMS-1 );
+      testcase( iCol==BMS );
+      if( (idxCols & cMask)==0 ){
+        Expr *pX = pTerm->pExpr;
+        idxCols |= cMask;
+        pIdx->aiColumn[n] = pTerm->u.leftColumn;
+        pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
+        pIdx->azColl[n] = pColl ? pColl->zName : "BINARY";
+        n++;
+      }
+    }
   }
+  assert( (u32)n==pLoop->u.btree.nEq );
 
-  /* Special case of a FROM clause subquery implemented as a co-routine */
+  /* Add additional columns needed to make the automatic index into
+  ** a covering index */
+  for(i=0; i<mxBitCol; i++){
+    if( extraCols & MASKBIT(i) ){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  if( pSrc->colUsed & MASKBIT(BMS-1) ){
+    for(i=BMS-1; i<pTable->nCol; i++){
+      pIdx->aiColumn[n] = i;
+      pIdx->azColl[n] = "BINARY";
+      n++;
+    }
+  }
+  assert( n==nKeyCol );
+  pIdx->aiColumn[n] = -1;
+  pIdx->azColl[n] = "BINARY";
+
+  /* Create the automatic index */
+  assert( pLevel->iIdxCur>=0 );
+  pLevel->iIdxCur = pParse->nTab++;
+  sqlite3VdbeAddOp2(v, OP_OpenAutoindex, pLevel->iIdxCur, nKeyCol+1);
+  sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
+  VdbeComment((v, "for %s", pTable->zName));
+
+  /* Fill the automatic index with content */
+  sqlite3ExprCachePush(pParse);
+  pTabItem = &pWC->pWInfo->pTabList->a[pLevel->iFrom];
   if( pTabItem->viaCoroutine ){
     int regYield = pTabItem->regReturn;
     sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
-    pLevel->p2 =  sqlite3VdbeAddOp2(v, OP_Yield, regYield, addrBrk);
+    addrTop =  sqlite3VdbeAddOp1(v, OP_Yield, regYield);
     VdbeCoverage(v);
     VdbeComment((v, "next row of \"%s\"", pTabItem->pTab->zName));
-    pLevel->op = OP_Goto;
-  }else
+  }else{
+    addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur); VdbeCoverage(v);
+  }
+  if( pPartial ){
+    iContinue = sqlite3VdbeMakeLabel(v);
+    sqlite3ExprIfFalse(pParse, pPartial, iContinue, SQLITE_JUMPIFNULL);
+    pLoop->wsFlags |= WHERE_PARTIALIDX;
+  }
+  regRecord = sqlite3GetTempReg(pParse);
+  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 0, 0, 0, 0);
+  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
+  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  if( pPartial ) sqlite3VdbeResolveLabel(v, iContinue);
+  if( pTabItem->viaCoroutine ){
+    translateColumnToCopy(v, addrTop, pLevel->iTabCur, pTabItem->regResult);
+    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrTop);
+    pTabItem->viaCoroutine = 0;
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1); VdbeCoverage(v);
+  }
+  sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
+  sqlite3VdbeJumpHere(v, addrTop);
+  sqlite3ReleaseTempReg(pParse, regRecord);
+  sqlite3ExprCachePop(pParse);
+  
+  /* Jump here when skipping the initialization */
+  sqlite3VdbeJumpHere(v, addrInit);
+
+end_auto_index_create:
+  sqlite3ExprDelete(pParse->db, pPartial);
+}
+#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-  if(  (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
-    /* Case 1:  The table is a virtual-table.  Use the VFilter and VNext
-    **          to access the data.
-    */
-    int iReg;   /* P3 Value for OP_VFilter */
-    int addrNotFound;
-    int nConstraint = pLoop->nLTerm;
+/*
+** Allocate and populate an sqlite3_index_info structure. It is the 
+** responsibility of the caller to eventually release the structure
+** by passing the pointer returned by this function to sqlite3_free().
+*/
+static sqlite3_index_info *allocateIndexInfo(
+  Parse *pParse,
+  WhereClause *pWC,
+  Bitmask mUnusable,              /* Ignore terms with these prereqs */
+  struct SrcList_item *pSrc,
+  ExprList *pOrderBy
+){
+  int i, j;
+  int nTerm;
+  struct sqlite3_index_constraint *pIdxCons;
+  struct sqlite3_index_orderby *pIdxOrderBy;
+  struct sqlite3_index_constraint_usage *pUsage;
+  WhereTerm *pTerm;
+  int nOrderBy;
+  sqlite3_index_info *pIdxInfo;
 
-    sqlite3ExprCachePush(pParse);
-    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
-    addrNotFound = pLevel->addrBrk;
-    for(j=0; j<nConstraint; j++){
-      int iTarget = iReg+j+2;
-      pTerm = pLoop->aLTerm[j];
-      if( pTerm==0 ) continue;
-      if( pTerm->eOperator & WO_IN ){
-        codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
-        addrNotFound = pLevel->addrNxt;
-      }else{
-        sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
-      }
+  /* Count the number of possible WHERE clause constraints referring
+  ** to this virtual table */
+  for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    if( pTerm->prereqRight & mUnusable ) continue;
+    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
+    testcase( pTerm->eOperator & WO_IN );
+    testcase( pTerm->eOperator & WO_ISNULL );
+    testcase( pTerm->eOperator & WO_IS );
+    testcase( pTerm->eOperator & WO_ALL );
+    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV|WO_IS))==0 ) continue;
+    if( pTerm->wtFlags & TERM_VNULL ) continue;
+    nTerm++;
+  }
+
+  /* If the ORDER BY clause contains only columns in the current 
+  ** virtual table then allocate space for the aOrderBy part of
+  ** the sqlite3_index_info structure.
+  */
+  nOrderBy = 0;
+  if( pOrderBy ){
+    int n = pOrderBy->nExpr;
+    for(i=0; i<n; i++){
+      Expr *pExpr = pOrderBy->a[i].pExpr;
+      if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
     }
-    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
-    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
-    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
-                      pLoop->u.vtab.idxStr,
-                      pLoop->u.vtab.needFree ? P4_MPRINTF : P4_STATIC);
-    VdbeCoverage(v);
-    pLoop->u.vtab.needFree = 0;
-    for(j=0; j<nConstraint && j<16; j++){
-      if( (pLoop->u.vtab.omitMask>>j)&1 ){
-        disableTerm(pLevel, pLoop->aLTerm[j]);
-      }
+    if( i==n){
+      nOrderBy = n;
     }
-    pLevel->op = OP_VNext;
-    pLevel->p1 = iCur;
-    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
-    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
-    sqlite3ExprCachePop(pParse);
-  }else
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
+  }
 
-  if( (pLoop->wsFlags & WHERE_IPK)!=0
-   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
-  ){
-    /* Case 2:  We can directly reference a single row using an
-    **          equality comparison against the ROWID field.  Or
-    **          we reference multiple rows using a "rowid IN (...)"
-    **          construct.
-    */
-    assert( pLoop->u.btree.nEq==1 );
-    pTerm = pLoop->aLTerm[0];
-    assert( pTerm!=0 );
-    assert( pTerm->pExpr!=0 );
-    assert( omitTable==0 );
-    testcase( pTerm->wtFlags & TERM_VIRTUAL );
-    iReleaseReg = ++pParse->nMem;
-    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
-    if( iRowidReg!=iReleaseReg ) sqlite3ReleaseTempReg(pParse, iReleaseReg);
-    addrNxt = pLevel->addrNxt;
-    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt); VdbeCoverage(v);
-    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
-    VdbeCoverage(v);
-    sqlite3ExprCacheAffinityChange(pParse, iRowidReg, 1);
-    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
-    VdbeComment((v, "pk"));
-    pLevel->op = OP_Noop;
-  }else if( (pLoop->wsFlags & WHERE_IPK)!=0
-         && (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
-  ){
-    /* Case 3:  We have an inequality comparison against the ROWID field.
-    */
-    int testOp = OP_Noop;
-    int start;
-    int memEndValue = 0;
-    WhereTerm *pStart, *pEnd;
+  /* Allocate the sqlite3_index_info structure
+  */
+  pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
+                           + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
+                           + sizeof(*pIdxOrderBy)*nOrderBy );
+  if( pIdxInfo==0 ){
+    sqlite3ErrorMsg(pParse, "out of memory");
+    return 0;
+  }
 
-    assert( omitTable==0 );
-    j = 0;
-    pStart = pEnd = 0;
-    if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
-    if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
-    assert( pStart!=0 || pEnd!=0 );
-    if( bRev ){
-      pTerm = pStart;
-      pStart = pEnd;
-      pEnd = pTerm;
-    }
-    if( pStart ){
-      Expr *pX;             /* The expression that defines the start bound */
-      int r1, rTemp;        /* Registers for holding the start boundary */
+  /* Initialize the structure.  The sqlite3_index_info structure contains
+  ** many fields that are declared "const" to prevent xBestIndex from
+  ** changing them.  We have to do some funky casting in order to
+  ** initialize those fields.
+  */
+  pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
+  pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
+  pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
+  *(int*)&pIdxInfo->nConstraint = nTerm;
+  *(int*)&pIdxInfo->nOrderBy = nOrderBy;
+  *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
+  *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
+  *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
+                                                                   pUsage;
 
-      /* The following constant maps TK_xx codes into corresponding 
-      ** seek opcodes.  It depends on a particular ordering of TK_xx
-      */
-      const u8 aMoveOp[] = {
-           /* TK_GT */  OP_SeekGT,
-           /* TK_LE */  OP_SeekLE,
-           /* TK_LT */  OP_SeekLT,
-           /* TK_GE */  OP_SeekGE
-      };
-      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
-      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
-      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */
+  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    u8 op;
+    if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    if( pTerm->prereqRight & mUnusable ) continue;
+    assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
+    testcase( pTerm->eOperator & WO_IN );
+    testcase( pTerm->eOperator & WO_IS );
+    testcase( pTerm->eOperator & WO_ISNULL );
+    testcase( pTerm->eOperator & WO_ALL );
+    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV|WO_IS))==0 ) continue;
+    if( pTerm->wtFlags & TERM_VNULL ) continue;
+    pIdxCons[j].iColumn = pTerm->u.leftColumn;
+    pIdxCons[j].iTermOffset = i;
+    op = (u8)pTerm->eOperator & WO_ALL;
+    if( op==WO_IN ) op = WO_EQ;
+    pIdxCons[j].op = op;
+    /* The direct assignment in the previous line is possible only because
+    ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
+    ** following asserts verify this fact. */
+    assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
+    assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
+    assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
+    assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
+    assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
+    assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
+    assert( pTerm->eOperator & (WO_IN|WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
+    j++;
+  }
+  for(i=0; i<nOrderBy; i++){
+    Expr *pExpr = pOrderBy->a[i].pExpr;
+    pIdxOrderBy[i].iColumn = pExpr->iColumn;
+    pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
+  }
 
-      assert( (pStart->wtFlags & TERM_VNULL)==0 );
-      testcase( pStart->wtFlags & TERM_VIRTUAL );
-      pX = pStart->pExpr;
-      assert( pX!=0 );
-      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
-      r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
-      sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
-      VdbeComment((v, "pk"));
-      VdbeCoverageIf(v, pX->op==TK_GT);
-      VdbeCoverageIf(v, pX->op==TK_LE);
-      VdbeCoverageIf(v, pX->op==TK_LT);
-      VdbeCoverageIf(v, pX->op==TK_GE);
-      sqlite3ExprCacheAffinityChange(pParse, r1, 1);
-      sqlite3ReleaseTempReg(pParse, rTemp);
-      disableTerm(pLevel, pStart);
-    }else{
-      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
-      VdbeCoverageIf(v, bRev==0);
-      VdbeCoverageIf(v, bRev!=0);
-    }
-    if( pEnd ){
-      Expr *pX;
-      pX = pEnd->pExpr;
-      assert( pX!=0 );
-      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
-      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
-      testcase( pEnd->wtFlags & TERM_VIRTUAL );
-      memEndValue = ++pParse->nMem;
-      sqlite3ExprCode(pParse, pX->pRight, memEndValue);
-      if( pX->op==TK_LT || pX->op==TK_GT ){
-        testOp = bRev ? OP_Le : OP_Ge;
-      }else{
-        testOp = bRev ? OP_Lt : OP_Gt;
-      }
-      disableTerm(pLevel, pEnd);
-    }
-    start = sqlite3VdbeCurrentAddr(v);
-    pLevel->op = bRev ? OP_Prev : OP_Next;
-    pLevel->p1 = iCur;
-    pLevel->p2 = start;
-    assert( pLevel->p5==0 );
-    if( testOp!=OP_Noop ){
-      iRowidReg = ++pParse->nMem;
-      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
-      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
-      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
-      VdbeCoverageIf(v, testOp==OP_Le);
-      VdbeCoverageIf(v, testOp==OP_Lt);
-      VdbeCoverageIf(v, testOp==OP_Ge);
-      VdbeCoverageIf(v, testOp==OP_Gt);
-      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
-    }
-  }else if( pLoop->wsFlags & WHERE_INDEXED ){
-    /* Case 4: A scan using an index.
-    **
-    **         The WHERE clause may contain zero or more equality 
-    **         terms ("==" or "IN" operators) that refer to the N
-    **         left-most columns of the index. It may also contain
-    **         inequality constraints (>, <, >= or <=) on the indexed
-    **         column that immediately follows the N equalities. Only 
-    **         the right-most column can be an inequality - the rest must
-    **         use the "==" and "IN" operators. For example, if the 
-    **         index is on (x,y,z), then the following clauses are all 
-    **         optimized:
-    **
-    **            x=5
-    **            x=5 AND y=10
-    **            x=5 AND y<10
-    **            x=5 AND y>5 AND y<10
-    **            x=5 AND y=5 AND z<=10
-    **
-    **         The z<10 term of the following cannot be used, only
-    **         the x=5 term:
-    **
-    **            x=5 AND z<10
-    **
-    **         N may be zero if there are inequality constraints.
-    **         If there are no inequality constraints, then N is at
-    **         least one.
-    **
-    **         This case is also used when there are no WHERE clause
-    **         constraints but an index is selected anyway, in order
-    **         to force the output order to conform to an ORDER BY.
-    */  
-    static const u8 aStartOp[] = {
-      0,
-      0,
-      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
-      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
-      OP_SeekGT,           /* 4: (start_constraints  && !startEq && !bRev) */
-      OP_SeekLT,           /* 5: (start_constraints  && !startEq &&  bRev) */
-      OP_SeekGE,           /* 6: (start_constraints  &&  startEq && !bRev) */
-      OP_SeekLE            /* 7: (start_constraints  &&  startEq &&  bRev) */
-    };
-    static const u8 aEndOp[] = {
-      OP_IdxGE,            /* 0: (end_constraints && !bRev && !endEq) */
-      OP_IdxGT,            /* 1: (end_constraints && !bRev &&  endEq) */
-      OP_IdxLE,            /* 2: (end_constraints &&  bRev && !endEq) */
-      OP_IdxLT,            /* 3: (end_constraints &&  bRev &&  endEq) */
-    };
-    u16 nEq = pLoop->u.btree.nEq;     /* Number of == or IN terms */
-    int regBase;                 /* Base register holding constraint values */
-    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
-    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
-    int startEq;                 /* True if range start uses ==, >= or <= */
-    int endEq;                   /* True if range end uses ==, >= or <= */
-    int start_constraints;       /* Start of range is constrained */
-    int nConstraint;             /* Number of constraint terms */
-    Index *pIdx;                 /* The index we will be using */
-    int iIdxCur;                 /* The VDBE cursor for the index */
-    int nExtraReg = 0;           /* Number of extra registers needed */
-    int op;                      /* Instruction opcode */
-    char *zStartAff;             /* Affinity for start of range constraint */
-    char cEndAff = 0;            /* Affinity for end of range constraint */
-    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
-    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
+  return pIdxInfo;
+}
 
-    pIdx = pLoop->u.btree.pIndex;
-    iIdxCur = pLevel->iIdxCur;
-    assert( nEq>=pLoop->nSkip );
+/*
+** The table object reference passed as the second argument to this function
+** must represent a virtual table. This function invokes the xBestIndex()
+** method of the virtual table with the sqlite3_index_info object that
+** comes in as the 3rd argument to this function.
+**
+** If an error occurs, pParse is populated with an error message and a
+** non-zero value is returned. Otherwise, 0 is returned and the output
+** part of the sqlite3_index_info structure is left populated.
+**
+** Whether or not an error is returned, it is the responsibility of the
+** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
+** that this is required.
+*/
+static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
+  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
+  int i;
+  int rc;
 
-    /* If this loop satisfies a sort order (pOrderBy) request that 
-    ** was passed to this function to implement a "SELECT min(x) ..." 
-    ** query, then the caller will only allow the loop to run for
-    ** a single iteration. This means that the first row returned
-    ** should not have a NULL value stored in 'x'. If column 'x' is
-    ** the first one after the nEq equality constraints in the index,
-    ** this requires some special handling.
-    */
-    assert( pWInfo->pOrderBy==0
-         || pWInfo->pOrderBy->nExpr==1
-         || (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0 );
-    if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
-     && pWInfo->nOBSat>0
-     && (pIdx->nKeyCol>nEq)
-    ){
-      assert( pLoop->nSkip==0 );
-      bSeekPastNull = 1;
-      nExtraReg = 1;
-    }
+  TRACE_IDX_INPUTS(p);
+  rc = pVtab->pModule->xBestIndex(pVtab, p);
+  TRACE_IDX_OUTPUTS(p);
 
-    /* Find any inequality constraint terms for the start and end 
-    ** of the range. 
-    */
-    j = nEq;
-    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
-      pRangeStart = pLoop->aLTerm[j++];
-      nExtraReg = 1;
-      /* Like optimization range constraints always occur in pairs */
-      assert( (pRangeStart->wtFlags & TERM_LIKEOPT)==0 || 
-              (pLoop->wsFlags & WHERE_TOP_LIMIT)!=0 );
+  if( rc!=SQLITE_OK ){
+    if( rc==SQLITE_NOMEM ){
+      pParse->db->mallocFailed = 1;
+    }else if( !pVtab->zErrMsg ){
+      sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
+    }else{
+      sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
     }
-    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
-      pRangeEnd = pLoop->aLTerm[j++];
-      nExtraReg = 1;
-      if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
-        assert( pRangeStart!=0 );                     /* LIKE opt constraints */
-        assert( pRangeStart->wtFlags & TERM_LIKEOPT );   /* occur in pairs */
-        pLevel->iLikeRepCntr = ++pParse->nMem;
-        testcase( bRev );
-        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
-        sqlite3VdbeAddOp2(v, OP_Integer,
-                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
-                          pLevel->iLikeRepCntr);
-        VdbeComment((v, "LIKE loop counter"));
-        pLevel->addrLikeRep = sqlite3VdbeCurrentAddr(v);
-      }
-      if( pRangeStart==0
-       && (j = pIdx->aiColumn[nEq])>=0 
-       && pIdx->pTable->aCol[j].notNull==0
-      ){
-        bSeekPastNull = 1;
-      }
+  }
+  sqlite3_free(pVtab->zErrMsg);
+  pVtab->zErrMsg = 0;
+
+  for(i=0; i<p->nConstraint; i++){
+    if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
+      sqlite3ErrorMsg(pParse, 
+          "table %s: xBestIndex returned an invalid plan", pTab->zName);
     }
-    assert( pRangeEnd==0 || (pRangeEnd->wtFlags & TERM_VNULL)==0 );
+  }
 
-    /* Generate code to evaluate all constraint terms using == or IN
-    ** and store the values of those terms in an array of registers
-    ** starting at regBase.
-    */
-    regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
-    assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
-    if( zStartAff ) cEndAff = zStartAff[nEq];
-    addrNxt = pLevel->addrNxt;
+  return pParse->nErr;
+}
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
 
-    /* If we are doing a reverse order scan on an ascending index, or
-    ** a forward order scan on a descending index, interchange the 
-    ** start and end terms (pRangeStart and pRangeEnd).
-    */
-    if( (nEq<pIdx->nKeyCol && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
-     || (bRev && pIdx->nKeyCol==nEq)
-    ){
-      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
-      SWAP(u8, bSeekPastNull, bStopAtNull);
-    }
+#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+/*
+** Estimate the location of a particular key among all keys in an
+** index.  Store the results in aStat as follows:
+**
+**    aStat[0]      Est. number of rows less than pRec
+**    aStat[1]      Est. number of rows equal to pRec
+**
+** Return the index of the sample that is the smallest sample that
+** is greater than or equal to pRec. Note that this index is not an index
+** into the aSample[] array - it is an index into a virtual set of samples
+** based on the contents of aSample[] and the number of fields in record 
+** pRec. 
+*/
+static int whereKeyStats(
+  Parse *pParse,              /* Database connection */
+  Index *pIdx,                /* Index to consider domain of */
+  UnpackedRecord *pRec,       /* Vector of values to consider */
+  int roundUp,                /* Round up if true.  Round down if false */
+  tRowcnt *aStat              /* OUT: stats written here */
+){
+  IndexSample *aSample = pIdx->aSample;
+  int iCol;                   /* Index of required stats in anEq[] etc. */
+  int i;                      /* Index of first sample >= pRec */
+  int iSample;                /* Smallest sample larger than or equal to pRec */
+  int iMin = 0;               /* Smallest sample not yet tested */
+  int iTest;                  /* Next sample to test */
+  int res;                    /* Result of comparison operation */
+  int nField;                 /* Number of fields in pRec */
+  tRowcnt iLower = 0;         /* anLt[] + anEq[] of largest sample pRec is > */
 
-    testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
-    testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
-    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
-    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
-    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
-    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
-    start_constraints = pRangeStart || nEq>0;
+#ifndef SQLITE_DEBUG
+  UNUSED_PARAMETER( pParse );
+#endif
+  assert( pRec!=0 );
+  assert( pIdx->nSample>0 );
+  assert( pRec->nField>0 && pRec->nField<=pIdx->nSampleCol );
+
+  /* Do a binary search to find the first sample greater than or equal
+  ** to pRec. If pRec contains a single field, the set of samples to search
+  ** is simply the aSample[] array. If the samples in aSample[] contain more
+  ** than one fields, all fields following the first are ignored.
+  **
+  ** If pRec contains N fields, where N is more than one, then as well as the
+  ** samples in aSample[] (truncated to N fields), the search also has to
+  ** consider prefixes of those samples. For example, if the set of samples
+  ** in aSample is:
+  **
+  **     aSample[0] = (a, 5) 
+  **     aSample[1] = (a, 10) 
+  **     aSample[2] = (b, 5) 
+  **     aSample[3] = (c, 100) 
+  **     aSample[4] = (c, 105)
+  **
+  ** Then the search space should ideally be the samples above and the 
+  ** unique prefixes [a], [b] and [c]. But since that is hard to organize, 
+  ** the code actually searches this set:
+  **
+  **     0: (a) 
+  **     1: (a, 5) 
+  **     2: (a, 10) 
+  **     3: (a, 10) 
+  **     4: (b) 
+  **     5: (b, 5) 
+  **     6: (c) 
+  **     7: (c, 100) 
+  **     8: (c, 105)
+  **     9: (c, 105)
+  **
+  ** For each sample in the aSample[] array, N samples are present in the
+  ** effective sample array. In the above, samples 0 and 1 are based on 
+  ** sample aSample[0]. Samples 2 and 3 on aSample[1] etc.
+  **
+  ** Often, sample i of each block of N effective samples has (i+1) fields.
+  ** Except, each sample may be extended to ensure that it is greater than or
+  ** equal to the previous sample in the array. For example, in the above, 
+  ** sample 2 is the first sample of a block of N samples, so at first it 
+  ** appears that it should be 1 field in size. However, that would make it 
+  ** smaller than sample 1, so the binary search would not work. As a result, 
+  ** it is extended to two fields. The duplicates that this creates do not 
+  ** cause any problems.
+  */
+  nField = pRec->nField;
+  iCol = 0;
+  iSample = pIdx->nSample * nField;
+  do{
+    int iSamp;                    /* Index in aSample[] of test sample */
+    int n;                        /* Number of fields in test sample */
 
-    /* Seek the index cursor to the start of the range. */
-    nConstraint = nEq;
-    if( pRangeStart ){
-      Expr *pRight = pRangeStart->pExpr->pRight;
-      sqlite3ExprCode(pParse, pRight, regBase+nEq);
-      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
-      if( (pRangeStart->wtFlags & TERM_VNULL)==0
-       && sqlite3ExprCanBeNull(pRight)
-      ){
-        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
-        VdbeCoverage(v);
+    iTest = (iMin+iSample)/2;
+    iSamp = iTest / nField;
+    if( iSamp>0 ){
+      /* The proposed effective sample is a prefix of sample aSample[iSamp].
+      ** Specifically, the shortest prefix of at least (1 + iTest%nField) 
+      ** fields that is greater than the previous effective sample.  */
+      for(n=(iTest % nField) + 1; n<nField; n++){
+        if( aSample[iSamp-1].anLt[n-1]!=aSample[iSamp].anLt[n-1] ) break;
       }
-      if( zStartAff ){
-        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
-          /* Since the comparison is to be performed with no conversions
-          ** applied to the operands, set the affinity to apply to pRight to 
-          ** SQLITE_AFF_NONE.  */
-          zStartAff[nEq] = SQLITE_AFF_NONE;
-        }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
-          zStartAff[nEq] = SQLITE_AFF_NONE;
-        }
-      }  
-      nConstraint++;
-      testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
-    }else if( bSeekPastNull ){
-      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
-      nConstraint++;
-      startEq = 0;
-      start_constraints = 1;
+    }else{
+      n = iTest + 1;
     }
-    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
-    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
-    assert( op!=0 );
-    sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
-    VdbeCoverage(v);
-    VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
-    VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
-    VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
-    VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
-    VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
-    VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
 
-    /* Load the value for the inequality constraint at the end of the
-    ** range (if any).
-    */
-    nConstraint = nEq;
-    if( pRangeEnd ){
-      Expr *pRight = pRangeEnd->pExpr->pRight;
-      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
-      sqlite3ExprCode(pParse, pRight, regBase+nEq);
-      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
-      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
-       && sqlite3ExprCanBeNull(pRight)
-      ){
-        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
-        VdbeCoverage(v);
-      }
-      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE
-       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)
-      ){
-        codeApplyAffinity(pParse, regBase+nEq, 1, &cEndAff);
-      }
-      nConstraint++;
-      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
-    }else if( bStopAtNull ){
-      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
-      endEq = 0;
-      nConstraint++;
+    pRec->nField = n;
+    res = sqlite3VdbeRecordCompare(aSample[iSamp].n, aSample[iSamp].p, pRec);
+    if( res<0 ){
+      iLower = aSample[iSamp].anLt[n-1] + aSample[iSamp].anEq[n-1];
+      iMin = iTest+1;
+    }else if( res==0 && n<nField ){
+      iLower = aSample[iSamp].anLt[n-1];
+      iMin = iTest+1;
+      res = -1;
+    }else{
+      iSample = iTest;
+      iCol = n-1;
     }
-    sqlite3DbFree(db, zStartAff);
+  }while( res && iMin<iSample );
+  i = iSample / nField;
 
-    /* Top of the loop body */
-    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
+#ifdef SQLITE_DEBUG
+  /* The following assert statements check that the binary search code
+  ** above found the right answer. This block serves no purpose other
+  ** than to invoke the asserts.  */
+  if( pParse->db->mallocFailed==0 ){
+    if( res==0 ){
+      /* If (res==0) is true, then pRec must be equal to sample i. */
+      assert( i<pIdx->nSample );
+      assert( iCol==nField-1 );
+      pRec->nField = nField;
+      assert( 0==sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec) 
+           || pParse->db->mallocFailed 
+      );
+    }else{
+      /* Unless i==pIdx->nSample, indicating that pRec is larger than
+      ** all samples in the aSample[] array, pRec must be smaller than the
+      ** (iCol+1) field prefix of sample i.  */
+      assert( i<=pIdx->nSample && i>=0 );
+      pRec->nField = iCol+1;
+      assert( i==pIdx->nSample 
+           || sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)>0
+           || pParse->db->mallocFailed );
 
-    /* Check if the index cursor is past the end of the range. */
-    if( nConstraint ){
-      op = aEndOp[bRev*2 + endEq];
-      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
-      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
-      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
-      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
-      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
+      /* if i==0 and iCol==0, then record pRec is smaller than all samples
+      ** in the aSample[] array. Otherwise, if (iCol>0) then pRec must
+      ** be greater than or equal to the (iCol) field prefix of sample i.
+      ** If (i>0), then pRec must also be greater than sample (i-1).  */
+      if( iCol>0 ){
+        pRec->nField = iCol;
+        assert( sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)<=0
+             || pParse->db->mallocFailed );
+      }
+      if( i>0 ){
+        pRec->nField = nField;
+        assert( sqlite3VdbeRecordCompare(aSample[i-1].n, aSample[i-1].p, pRec)<0
+             || pParse->db->mallocFailed );
+      }
     }
+  }
+#endif /* ifdef SQLITE_DEBUG */
 
-    /* Seek the table cursor, if required */
-    disableTerm(pLevel, pRangeStart);
-    disableTerm(pLevel, pRangeEnd);
-    if( omitTable ){
-      /* pIdx is a covering index.  No need to access the main table. */
-    }else if( HasRowid(pIdx->pTable) ){
-      iRowidReg = ++pParse->nMem;
-      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
-      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
-      sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg);  /* Deferred seek */
-    }else if( iCur!=iIdxCur ){
-      Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
-      iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
-      for(j=0; j<pPk->nKeyCol; j++){
-        k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[j]);
-        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
-      }
-      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
-                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
+  if( res==0 ){
+    /* Record pRec is equal to sample i */
+    assert( iCol==nField-1 );
+    aStat[0] = aSample[i].anLt[iCol];
+    aStat[1] = aSample[i].anEq[iCol];
+  }else{
+    /* At this point, the (iCol+1) field prefix of aSample[i] is the first 
+    ** sample that is greater than pRec. Or, if i==pIdx->nSample then pRec
+    ** is larger than all samples in the array. */
+    tRowcnt iUpper, iGap;
+    if( i>=pIdx->nSample ){
+      iUpper = sqlite3LogEstToInt(pIdx->aiRowLogEst[0]);
+    }else{
+      iUpper = aSample[i].anLt[iCol];
     }
 
-    /* Record the instruction used to terminate the loop. Disable 
-    ** WHERE clause terms made redundant by the index range scan.
-    */
-    if( pLoop->wsFlags & WHERE_ONEROW ){
-      pLevel->op = OP_Noop;
-    }else if( bRev ){
-      pLevel->op = OP_Prev;
+    if( iLower>=iUpper ){
+      iGap = 0;
     }else{
-      pLevel->op = OP_Next;
+      iGap = iUpper - iLower;
     }
-    pLevel->p1 = iIdxCur;
-    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
-    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
-      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+    if( roundUp ){
+      iGap = (iGap*2)/3;
     }else{
-      assert( pLevel->p5==0 );
+      iGap = iGap/3;
     }
-  }else
-
-#ifndef SQLITE_OMIT_OR_OPTIMIZATION
-  if( pLoop->wsFlags & WHERE_MULTI_OR ){
-    /* Case 5:  Two or more separately indexed terms connected by OR
-    **
-    ** Example:
-    **
-    **   CREATE TABLE t1(a,b,c,d);
-    **   CREATE INDEX i1 ON t1(a);
-    **   CREATE INDEX i2 ON t1(b);
-    **   CREATE INDEX i3 ON t1(c);
-    **
-    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
-    **
-    ** In the example, there are three indexed terms connected by OR.
-    ** The top of the loop looks like this:
-    **
-    **          Null       1                # Zero the rowset in reg 1
-    **
-    ** Then, for each indexed term, the following. The arguments to
-    ** RowSetTest are such that the rowid of the current row is inserted
-    ** into the RowSet. If it is already present, control skips the
-    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
-    **
-    **        sqlite3WhereBegin(<term>)
-    **          RowSetTest                  # Insert rowid into rowset
-    **          Gosub      2 A
-    **        sqlite3WhereEnd()
-    **
-    ** Following the above, code to terminate the loop. Label A, the target
-    ** of the Gosub above, jumps to the instruction right after the Goto.
-    **
-    **          Null       1                # Zero the rowset in reg 1
-    **          Goto       B                # The loop is finished.
-    **
-    **       A: <loop body>                 # Return data, whatever.
-    **
-    **          Return     2                # Jump back to the Gosub
-    **
-    **       B: <after the loop>
-    **
-    ** Added 2014-05-26: If the table is a WITHOUT ROWID table, then
-    ** use an ephemeral index instead of a RowSet to record the primary
-    ** keys of the rows we have already seen.
-    **
-    */
-    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
-    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
-    Index *pCov = 0;             /* Potential covering index (or NULL) */
-    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */
+    aStat[0] = iLower + iGap;
+    aStat[1] = pIdx->aAvgEq[iCol];
+  }
 
-    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
-    int regRowset = 0;                        /* Register for RowSet object */
-    int regRowid = 0;                         /* Register holding rowid */
-    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
-    int iRetInit;                             /* Address of regReturn init */
-    int untestedTerms = 0;             /* Some terms not completely tested */
-    int ii;                            /* Loop counter */
-    u16 wctrlFlags;                    /* Flags for sub-WHERE clause */
-    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
-    Table *pTab = pTabItem->pTab;
-   
-    pTerm = pLoop->aLTerm[0];
-    assert( pTerm!=0 );
-    assert( pTerm->eOperator & WO_OR );
-    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
-    pOrWc = &pTerm->u.pOrInfo->wc;
-    pLevel->op = OP_Return;
-    pLevel->p1 = regReturn;
+  /* Restore the pRec->nField value before returning.  */
+  pRec->nField = nField;
+  return i;
+}
+#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
-    /* Set up a new SrcList in pOrTab containing the table being scanned
-    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
-    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
-    */
-    if( pWInfo->nLevel>1 ){
-      int nNotReady;                 /* The number of notReady tables */
-      struct SrcList_item *origSrc;     /* Original list of tables */
-      nNotReady = pWInfo->nLevel - iLevel - 1;
-      pOrTab = sqlite3StackAllocRaw(db,
-                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
-      if( pOrTab==0 ) return notReady;
-      pOrTab->nAlloc = (u8)(nNotReady + 1);
-      pOrTab->nSrc = pOrTab->nAlloc;
-      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
-      origSrc = pWInfo->pTabList->a;
-      for(k=1; k<=nNotReady; k++){
-        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
-      }
-    }else{
-      pOrTab = pWInfo->pTabList;
+/*
+** If it is not NULL, pTerm is a term that provides an upper or lower
+** bound on a range scan. Without considering pTerm, it is estimated 
+** that the scan will visit nNew rows. This function returns the number
+** estimated to be visited after taking pTerm into account.
+**
+** If the user explicitly specified a likelihood() value for this term,
+** then the return value is the likelihood multiplied by the number of
+** input rows. Otherwise, this function assumes that an "IS NOT NULL" term
+** has a likelihood of 0.50, and any other term a likelihood of 0.25.
+*/
+static LogEst whereRangeAdjust(WhereTerm *pTerm, LogEst nNew){
+  LogEst nRet = nNew;
+  if( pTerm ){
+    if( pTerm->truthProb<=0 ){
+      nRet += pTerm->truthProb;
+    }else if( (pTerm->wtFlags & TERM_VNULL)==0 ){
+      nRet -= 20;        assert( 20==sqlite3LogEst(4) );
     }
+  }
+  return nRet;
+}
 
-    /* Initialize the rowset register to contain NULL. An SQL NULL is 
-    ** equivalent to an empty rowset.  Or, create an ephemeral index
-    ** capable of holding primary keys in the case of a WITHOUT ROWID.
-    **
-    ** Also initialize regReturn to contain the address of the instruction 
-    ** immediately following the OP_Return at the bottom of the loop. This
-    ** is required in a few obscure LEFT JOIN cases where control jumps
-    ** over the top of the loop into the body of it. In this case the 
-    ** correct response for the end-of-loop code (the OP_Return) is to 
-    ** fall through to the next instruction, just as an OP_Next does if
-    ** called on an uninitialized cursor.
-    */
-    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
-      if( HasRowid(pTab) ){
-        regRowset = ++pParse->nMem;
-        sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
-      }else{
-        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
-        regRowset = pParse->nTab++;
-        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, regRowset, pPk->nKeyCol);
-        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
-      }
-      regRowid = ++pParse->nMem;
-    }
-    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
+#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+/* 
+** This function is called to estimate the number of rows visited by a
+** range-scan on a skip-scan index. For example:
+**
+**   CREATE INDEX i1 ON t1(a, b, c);
+**   SELECT * FROM t1 WHERE a=? AND c BETWEEN ? AND ?;
+**
+** Value pLoop->nOut is currently set to the estimated number of rows 
+** visited for scanning (a=? AND b=?). This function reduces that estimate 
+** by some factor to account for the (c BETWEEN ? AND ?) expression based
+** on the stat4 data for the index. this scan will be peformed multiple 
+** times (once for each (a,b) combination that matches a=?) is dealt with 
+** by the caller.
+**
+** It does this by scanning through all stat4 samples, comparing values
+** extracted from pLower and pUpper with the corresponding column in each
+** sample. If L and U are the number of samples found to be less than or
+** equal to the values extracted from pLower and pUpper respectively, and
+** N is the total number of samples, the pLoop->nOut value is adjusted
+** as follows:
+**
+**   nOut = nOut * ( min(U - L, 1) / N )
+**
+** If pLower is NULL, or a value cannot be extracted from the term, L is
+** set to zero. If pUpper is NULL, or a value cannot be extracted from it,
+** U is set to N.
+**
+** Normally, this function sets *pbDone to 1 before returning. However,
+** if no value can be extracted from either pLower or pUpper (and so the
+** estimate of the number of rows delivered remains unchanged), *pbDone
+** is left as is.
+**
+** If an error occurs, an SQLite error code is returned. Otherwise, 
+** SQLITE_OK.
+*/
+static int whereRangeSkipScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
+  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
+  WhereLoop *pLoop,    /* Update the .nOut value of this loop */
+  int *pbDone          /* Set to true if at least one expr. value extracted */
+){
+  Index *p = pLoop->u.btree.pIndex;
+  int nEq = pLoop->u.btree.nEq;
+  sqlite3 *db = pParse->db;
+  int nLower = -1;
+  int nUpper = p->nSample+1;
+  int rc = SQLITE_OK;
+  int iCol = p->aiColumn[nEq];
+  u8 aff = iCol>=0 ? p->pTable->aCol[iCol].affinity : SQLITE_AFF_INTEGER;
+  CollSeq *pColl;
+  
+  sqlite3_value *p1 = 0;          /* Value extracted from pLower */
+  sqlite3_value *p2 = 0;          /* Value extracted from pUpper */
+  sqlite3_value *pVal = 0;        /* Value extracted from record */
 
-    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
-    ** Then for every term xN, evaluate as the subexpression: xN AND z
-    ** That way, terms in y that are factored into the disjunction will
-    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
-    **
-    ** Actually, each subexpression is converted to "xN AND w" where w is
-    ** the "interesting" terms of z - terms that did not originate in the
-    ** ON or USING clause of a LEFT JOIN, and terms that are usable as 
-    ** indices.
-    **
-    ** This optimization also only applies if the (x1 OR x2 OR ...) term
-    ** is not contained in the ON clause of a LEFT JOIN.
-    ** See ticket http://www.sqlite.org/src/info/f2369304e4
-    */
-    if( pWC->nTerm>1 ){
-      int iTerm;
-      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
-        Expr *pExpr = pWC->a[iTerm].pExpr;
-        if( &pWC->a[iTerm] == pTerm ) continue;
-        if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
-        if( (pWC->a[iTerm].wtFlags & TERM_VIRTUAL)!=0 ) continue;
-        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
-        testcase( pWC->a[iTerm].wtFlags & TERM_ORINFO );
-        pExpr = sqlite3ExprDup(db, pExpr, 0);
-        pAndExpr = sqlite3ExprAnd(db, pAndExpr, pExpr);
+  pColl = sqlite3LocateCollSeq(pParse, p->azColl[nEq]);
+  if( pLower ){
+    rc = sqlite3Stat4ValueFromExpr(pParse, pLower->pExpr->pRight, aff, &p1);
+    nLower = 0;
+  }
+  if( pUpper && rc==SQLITE_OK ){
+    rc = sqlite3Stat4ValueFromExpr(pParse, pUpper->pExpr->pRight, aff, &p2);
+    nUpper = p2 ? 0 : p->nSample;
+  }
+
+  if( p1 || p2 ){
+    int i;
+    int nDiff;
+    for(i=0; rc==SQLITE_OK && i<p->nSample; i++){
+      rc = sqlite3Stat4Column(db, p->aSample[i].p, p->aSample[i].n, nEq, &pVal);
+      if( rc==SQLITE_OK && p1 ){
+        int res = sqlite3MemCompare(p1, pVal, pColl);
+        if( res>=0 ) nLower++;
       }
-      if( pAndExpr ){
-        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
+      if( rc==SQLITE_OK && p2 ){
+        int res = sqlite3MemCompare(p2, pVal, pColl);
+        if( res>=0 ) nUpper++;
       }
     }
+    nDiff = (nUpper - nLower);
+    if( nDiff<=0 ) nDiff = 1;
 
-    /* Run a separate WHERE clause for each term of the OR clause.  After
-    ** eliminating duplicates from other WHERE clauses, the action for each
-    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
-    */
-    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE
-                | WHERE_FORCE_TABLE
-                | WHERE_ONETABLE_ONLY
-                | WHERE_NO_AUTOINDEX;
-    for(ii=0; ii<pOrWc->nTerm; ii++){
-      WhereTerm *pOrTerm = &pOrWc->a[ii];
-      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
-        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
-        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
-        int j1 = 0;                     /* Address of jump operation */
-        if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
-          pAndExpr->pLeft = pOrExpr;
-          pOrExpr = pAndExpr;
-        }
-        /* Loop through table entries that match term pOrTerm. */
-        WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
-        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
-                                      wctrlFlags, iCovCur);
-        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
-        if( pSubWInfo ){
-          WhereLoop *pSubLoop;
-          int addrExplain = explainOneScan(
-              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
-          );
-          addScanStatus(v, pOrTab, &pSubWInfo->a[0], addrExplain);
+    /* If there is both an upper and lower bound specified, and the 
+    ** comparisons indicate that they are close together, use the fallback
+    ** method (assume that the scan visits 1/64 of the rows) for estimating
+    ** the number of rows visited. Otherwise, estimate the number of rows
+    ** using the method described in the header comment for this function. */
+    if( nDiff!=1 || pUpper==0 || pLower==0 ){
+      int nAdjust = (sqlite3LogEst(p->nSample) - sqlite3LogEst(nDiff));
+      pLoop->nOut -= nAdjust;
+      *pbDone = 1;
+      WHERETRACE(0x10, ("range skip-scan regions: %u..%u  adjust=%d est=%d\n",
+                           nLower, nUpper, nAdjust*-1, pLoop->nOut));
+    }
 
-          /* This is the sub-WHERE clause body.  First skip over
-          ** duplicate rows from prior sub-WHERE clauses, and record the
-          ** rowid (or PRIMARY KEY) for the current row so that the same
-          ** row will be skipped in subsequent sub-WHERE clauses.
-          */
-          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
-            int r;
-            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
-            if( HasRowid(pTab) ){
-              r = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, regRowid, 0);
-              j1 = sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset, 0, r,iSet);
-              VdbeCoverage(v);
-            }else{
-              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
-              int nPk = pPk->nKeyCol;
-              int iPk;
+  }else{
+    assert( *pbDone==0 );
+  }
 
-              /* Read the PK into an array of temp registers. */
-              r = sqlite3GetTempRange(pParse, nPk);
-              for(iPk=0; iPk<nPk; iPk++){
-                int iCol = pPk->aiColumn[iPk];
-                sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur, r+iPk, 0);
-              }
+  sqlite3ValueFree(p1);
+  sqlite3ValueFree(p2);
+  sqlite3ValueFree(pVal);
 
-              /* Check if the temp table already contains this key. If so,
-              ** the row has already been included in the result set and
-              ** can be ignored (by jumping past the Gosub below). Otherwise,
-              ** insert the key into the temp table and proceed with processing
-              ** the row.
-              **
-              ** Use some of the same optimizations as OP_RowSetTest: If iSet
-              ** is zero, assume that the key cannot already be present in
-              ** the temp table. And if iSet is -1, assume that there is no 
-              ** need to insert the key into the temp table, as it will never 
-              ** be tested for.  */ 
-              if( iSet ){
-                j1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
-                VdbeCoverage(v);
-              }
-              if( iSet>=0 ){
-                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
-                sqlite3VdbeAddOp3(v, OP_IdxInsert, regRowset, regRowid, 0);
-                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
-              }
+  return rc;
+}
+#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
-              /* Release the array of temp registers */
-              sqlite3ReleaseTempRange(pParse, r, nPk);
-            }
-          }
+/*
+** This function is used to estimate the number of rows that will be visited
+** by scanning an index for a range of values. The range may have an upper
+** bound, a lower bound, or both. The WHERE clause terms that set the upper
+** and lower bounds are represented by pLower and pUpper respectively. For
+** example, assuming that index p is on t1(a):
+**
+**   ... FROM t1 WHERE a > ? AND a < ? ...
+**                    |_____|   |_____|
+**                       |         |
+**                     pLower    pUpper
+**
+** If either of the upper or lower bound is not present, then NULL is passed in
+** place of the corresponding WhereTerm.
+**
+** The value in (pBuilder->pNew->u.btree.nEq) is the number of the index
+** column subject to the range constraint. Or, equivalently, the number of
+** equality constraints optimized by the proposed index scan. For example,
+** assuming index p is on t1(a, b), and the SQL query is:
+**
+**   ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
+**
+** then nEq is set to 1 (as the range restricted column, b, is the second 
+** left-most column of the index). Or, if the query is:
+**
+**   ... FROM t1 WHERE a > ? AND a < ? ...
+**
+** then nEq is set to 0.
+**
+** When this function is called, *pnOut is set to the sqlite3LogEst() of the
+** number of rows that the index scan is expected to visit without 
+** considering the range constraints. If nEq is 0, then *pnOut is the number of 
+** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced)
+** to account for the range constraints pLower and pUpper.
+** 
+** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be
+** used, a single range inequality reduces the search space by a factor of 4. 
+** and a pair of constraints (x>? AND x<?) reduces the expected number of
+** rows visited by a factor of 64.
+*/
+static int whereRangeScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereLoopBuilder *pBuilder,
+  WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
+  WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
+  WhereLoop *pLoop     /* Modify the .nOut and maybe .rRun fields */
+){
+  int rc = SQLITE_OK;
+  int nOut = pLoop->nOut;
+  LogEst nNew;
 
-          /* Invoke the main loop body as a subroutine */
-          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
+#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+  Index *p = pLoop->u.btree.pIndex;
+  int nEq = pLoop->u.btree.nEq;
 
-          /* Jump here (skipping the main loop body subroutine) if the
-          ** current sub-WHERE row is a duplicate from prior sub-WHEREs. */
-          if( j1 ) sqlite3VdbeJumpHere(v, j1);
+  if( p->nSample>0 && nEq<p->nSampleCol ){
+    if( nEq==pBuilder->nRecValid ){
+      UnpackedRecord *pRec = pBuilder->pRec;
+      tRowcnt a[2];
+      u8 aff;
 
-          /* The pSubWInfo->untestedTerms flag means that this OR term
-          ** contained one or more AND term from a notReady table.  The
-          ** terms from the notReady table could not be tested and will
-          ** need to be tested later.
-          */
-          if( pSubWInfo->untestedTerms ) untestedTerms = 1;
+      /* Variable iLower will be set to the estimate of the number of rows in 
+      ** the index that are less than the lower bound of the range query. The
+      ** lower bound being the concatenation of $P and $L, where $P is the
+      ** key-prefix formed by the nEq values matched against the nEq left-most
+      ** columns of the index, and $L is the value in pLower.
+      **
+      ** Or, if pLower is NULL or $L cannot be extracted from it (because it
+      ** is not a simple variable or literal value), the lower bound of the
+      ** range is $P. Due to a quirk in the way whereKeyStats() works, even
+      ** if $L is available, whereKeyStats() is called for both ($P) and 
+      ** ($P:$L) and the larger of the two returned values is used.
+      **
+      ** Similarly, iUpper is to be set to the estimate of the number of rows
+      ** less than the upper bound of the range query. Where the upper bound
+      ** is either ($P) or ($P:$U). Again, even if $U is available, both values
+      ** of iUpper are requested of whereKeyStats() and the smaller used.
+      **
+      ** The number of rows between the two bounds is then just iUpper-iLower.
+      */
+      tRowcnt iLower;     /* Rows less than the lower bound */
+      tRowcnt iUpper;     /* Rows less than the upper bound */
+      int iLwrIdx = -2;   /* aSample[] for the lower bound */
+      int iUprIdx = -1;   /* aSample[] for the upper bound */
 
-          /* If all of the OR-connected terms are optimized using the same
-          ** index, and the index is opened using the same cursor number
-          ** by each call to sqlite3WhereBegin() made by this loop, it may
-          ** be possible to use that index as a covering index.
-          **
-          ** If the call to sqlite3WhereBegin() above resulted in a scan that
-          ** uses an index, and this is either the first OR-connected term
-          ** processed or the index is the same as that used by all previous
-          ** terms, set pCov to the candidate covering index. Otherwise, set 
-          ** pCov to NULL to indicate that no candidate covering index will 
-          ** be available.
-          */
-          pSubLoop = pSubWInfo->a[0].pWLoop;
-          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
-          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
-           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
-           && (HasRowid(pTab) || !IsPrimaryKeyIndex(pSubLoop->u.btree.pIndex))
-          ){
-            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
-            pCov = pSubLoop->u.btree.pIndex;
-            wctrlFlags |= WHERE_REOPEN_IDX;
-          }else{
-            pCov = 0;
-          }
+      if( pRec ){
+        testcase( pRec->nField!=pBuilder->nRecValid );
+        pRec->nField = pBuilder->nRecValid;
+      }
+      if( nEq==p->nKeyCol ){
+        aff = SQLITE_AFF_INTEGER;
+      }else{
+        aff = p->pTable->aCol[p->aiColumn[nEq]].affinity;
+      }
+      /* Determine iLower and iUpper using ($P) only. */
+      if( nEq==0 ){
+        iLower = 0;
+        iUpper = p->nRowEst0;
+      }else{
+        /* Note: this call could be optimized away - since the same values must 
+        ** have been requested when testing key $P in whereEqualScanEst().  */
+        whereKeyStats(pParse, p, pRec, 0, a);
+        iLower = a[0];
+        iUpper = a[0] + a[1];
+      }
 
-          /* Finish the loop through table entries that match term pOrTerm. */
-          sqlite3WhereEnd(pSubWInfo);
+      assert( pLower==0 || (pLower->eOperator & (WO_GT|WO_GE))!=0 );
+      assert( pUpper==0 || (pUpper->eOperator & (WO_LT|WO_LE))!=0 );
+      assert( p->aSortOrder!=0 );
+      if( p->aSortOrder[nEq] ){
+        /* The roles of pLower and pUpper are swapped for a DESC index */
+        SWAP(WhereTerm*, pLower, pUpper);
+      }
+
+      /* If possible, improve on the iLower estimate using ($P:$L). */
+      if( pLower ){
+        int bOk;                    /* True if value is extracted from pExpr */
+        Expr *pExpr = pLower->pExpr->pRight;
+        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
+        if( rc==SQLITE_OK && bOk ){
+          tRowcnt iNew;
+          iLwrIdx = whereKeyStats(pParse, p, pRec, 0, a);
+          iNew = a[0] + ((pLower->eOperator & (WO_GT|WO_LE)) ? a[1] : 0);
+          if( iNew>iLower ) iLower = iNew;
+          nOut--;
+          pLower = 0;
         }
       }
-    }
-    pLevel->u.pCovidx = pCov;
-    if( pCov ) pLevel->iIdxCur = iCovCur;
-    if( pAndExpr ){
-      pAndExpr->pLeft = 0;
-      sqlite3ExprDelete(db, pAndExpr);
-    }
-    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
-    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
-    sqlite3VdbeResolveLabel(v, iLoopBody);
 
-    if( pWInfo->nLevel>1 ) sqlite3StackFree(db, pOrTab);
-    if( !untestedTerms ) disableTerm(pLevel, pTerm);
-  }else
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
+      /* If possible, improve on the iUpper estimate using ($P:$U). */
+      if( pUpper ){
+        int bOk;                    /* True if value is extracted from pExpr */
+        Expr *pExpr = pUpper->pExpr->pRight;
+        rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
+        if( rc==SQLITE_OK && bOk ){
+          tRowcnt iNew;
+          iUprIdx = whereKeyStats(pParse, p, pRec, 1, a);
+          iNew = a[0] + ((pUpper->eOperator & (WO_GT|WO_LE)) ? a[1] : 0);
+          if( iNew<iUpper ) iUpper = iNew;
+          nOut--;
+          pUpper = 0;
+        }
+      }
 
-  {
-    /* Case 6:  There is no usable index.  We must do a complete
-    **          scan of the entire table.
-    */
-    static const u8 aStep[] = { OP_Next, OP_Prev };
-    static const u8 aStart[] = { OP_Rewind, OP_Last };
-    assert( bRev==0 || bRev==1 );
-    if( pTabItem->isRecursive ){
-      /* Tables marked isRecursive have only a single row that is stored in
-      ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
-      pLevel->op = OP_Noop;
+      pBuilder->pRec = pRec;
+      if( rc==SQLITE_OK ){
+        if( iUpper>iLower ){
+          nNew = sqlite3LogEst(iUpper - iLower);
+          /* TUNING:  If both iUpper and iLower are derived from the same
+          ** sample, then assume they are 4x more selective.  This brings
+          ** the estimated selectivity more in line with what it would be
+          ** if estimated without the use of STAT3/4 tables. */
+          if( iLwrIdx==iUprIdx ) nNew -= 20;  assert( 20==sqlite3LogEst(4) );
+        }else{
+          nNew = 10;        assert( 10==sqlite3LogEst(2) );
+        }
+        if( nNew<nOut ){
+          nOut = nNew;
+        }
+        WHERETRACE(0x10, ("STAT4 range scan: %u..%u  est=%d\n",
+                           (u32)iLower, (u32)iUpper, nOut));
+      }
     }else{
-      pLevel->op = aStep[bRev];
-      pLevel->p1 = iCur;
-      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
-      VdbeCoverageIf(v, bRev==0);
-      VdbeCoverageIf(v, bRev!=0);
-      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
+      int bDone = 0;
+      rc = whereRangeSkipScanEst(pParse, pLower, pUpper, pLoop, &bDone);
+      if( bDone ) return rc;
     }
   }
+#else
+  UNUSED_PARAMETER(pParse);
+  UNUSED_PARAMETER(pBuilder);
+  assert( pLower || pUpper );
+#endif
+  assert( pUpper==0 || (pUpper->wtFlags & TERM_VNULL)==0 );
+  nNew = whereRangeAdjust(pLower, nOut);
+  nNew = whereRangeAdjust(pUpper, nNew);
+
+  /* TUNING: If there is both an upper and lower limit and neither limit
+  ** has an application-defined likelihood(), assume the range is
+  ** reduced by an additional 75%. This means that, by default, an open-ended
+  ** range query (e.g. col > ?) is assumed to match 1/4 of the rows in the
+  ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
+  ** match 1/64 of the index. */ 
+  if( pLower && pLower->truthProb>0 && pUpper && pUpper->truthProb>0 ){
+    nNew -= 20;
+  }
 
-#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
-  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
+  nOut -= (pLower!=0) + (pUpper!=0);
+  if( nNew<10 ) nNew = 10;
+  if( nNew<nOut ) nOut = nNew;
+#if defined(WHERETRACE_ENABLED)
+  if( pLoop->nOut>nOut ){
+    WHERETRACE(0x10,("Range scan lowers nOut from %d to %d\n",
+                    pLoop->nOut, nOut));
+  }
 #endif
+  pLoop->nOut = (LogEst)nOut;
+  return rc;
+}
 
-  /* Insert code to test every subexpression that can be completely
-  ** computed using the current set of tables.
-  */
-  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
-    Expr *pE;
-    int skipLikeAddr = 0;
-    testcase( pTerm->wtFlags & TERM_VIRTUAL );
-    testcase( pTerm->wtFlags & TERM_CODED );
-    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
-      testcase( pWInfo->untestedTerms==0
-               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
-      pWInfo->untestedTerms = 1;
-      continue;
-    }
-    pE = pTerm->pExpr;
-    assert( pE!=0 );
-    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
-      continue;
-    }
-    if( pTerm->wtFlags & TERM_LIKECOND ){
-      assert( pLevel->iLikeRepCntr>0 );
-      skipLikeAddr = sqlite3VdbeAddOp1(v, OP_IfNot, pLevel->iLikeRepCntr);
-      VdbeCoverage(v);
-    }
-    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
-    if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
-    pTerm->wtFlags |= TERM_CODED;
+#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+/*
+** Estimate the number of rows that will be returned based on
+** an equality constraint x=VALUE and where that VALUE occurs in
+** the histogram data.  This only works when x is the left-most
+** column of an index and sqlite_stat3 histogram data is available
+** for that index.  When pExpr==NULL that means the constraint is
+** "x IS NULL" instead of "x=VALUE".
+**
+** Write the estimated row count into *pnRow and return SQLITE_OK. 
+** If unable to make an estimate, leave *pnRow unchanged and return
+** non-zero.
+**
+** This routine can fail if it is unable to load a collating sequence
+** required for string comparison, or if unable to allocate memory
+** for a UTF conversion required for comparison.  The error is stored
+** in the pParse structure.
+*/
+static int whereEqualScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereLoopBuilder *pBuilder,
+  Expr *pExpr,         /* Expression for VALUE in the x=VALUE constraint */
+  tRowcnt *pnRow       /* Write the revised row estimate here */
+){
+  Index *p = pBuilder->pNew->u.btree.pIndex;
+  int nEq = pBuilder->pNew->u.btree.nEq;
+  UnpackedRecord *pRec = pBuilder->pRec;
+  u8 aff;                   /* Column affinity */
+  int rc;                   /* Subfunction return code */
+  tRowcnt a[2];             /* Statistics */
+  int bOk;
+
+  assert( nEq>=1 );
+  assert( nEq<=p->nColumn );
+  assert( p->aSample!=0 );
+  assert( p->nSample>0 );
+  assert( pBuilder->nRecValid<nEq );
+
+  /* If values are not available for all fields of the index to the left
+  ** of this one, no estimate can be made. Return SQLITE_NOTFOUND. */
+  if( pBuilder->nRecValid<(nEq-1) ){
+    return SQLITE_NOTFOUND;
   }
 
-  /* Insert code to test for implied constraints based on transitivity
-  ** of the "==" operator.
-  **
-  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
-  ** and we are coding the t1 loop and the t2 loop has not yet coded,
-  ** then we cannot use the "t1.a=t2.b" constraint, but we can code
-  ** the implied "t1.a=123" constraint.
-  */
-  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
-    Expr *pE, *pEAlt;
-    WhereTerm *pAlt;
-    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-    if( pTerm->eOperator!=(WO_EQUIV|WO_EQ) ) continue;
-    if( pTerm->leftCursor!=iCur ) continue;
-    if( pLevel->iLeftJoin ) continue;
-    pE = pTerm->pExpr;
-    assert( !ExprHasProperty(pE, EP_FromJoin) );
-    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
-    pAlt = findTerm(pWC, iCur, pTerm->u.leftColumn, notReady, WO_EQ|WO_IN, 0);
-    if( pAlt==0 ) continue;
-    if( pAlt->wtFlags & (TERM_CODED) ) continue;
-    testcase( pAlt->eOperator & WO_EQ );
-    testcase( pAlt->eOperator & WO_IN );
-    VdbeModuleComment((v, "begin transitive constraint"));
-    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
-    if( pEAlt ){
-      *pEAlt = *pAlt->pExpr;
-      pEAlt->pLeft = pE->pLeft;
-      sqlite3ExprIfFalse(pParse, pEAlt, addrCont, SQLITE_JUMPIFNULL);
-      sqlite3StackFree(db, pEAlt);
-    }
+  /* This is an optimization only. The call to sqlite3Stat4ProbeSetValue()
+  ** below would return the same value.  */
+  if( nEq>=p->nColumn ){
+    *pnRow = 1;
+    return SQLITE_OK;
   }
 
-  /* For a LEFT OUTER JOIN, generate code that will record the fact that
-  ** at least one row of the right table has matched the left table.  
-  */
-  if( pLevel->iLeftJoin ){
-    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
-    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
-    VdbeComment((v, "record LEFT JOIN hit"));
-    sqlite3ExprCacheClear(pParse);
-    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
-      testcase( pTerm->wtFlags & TERM_VIRTUAL );
-      testcase( pTerm->wtFlags & TERM_CODED );
-      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
-        assert( pWInfo->untestedTerms );
-        continue;
-      }
-      assert( pTerm->pExpr );
-      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
-      pTerm->wtFlags |= TERM_CODED;
-    }
+  aff = p->pTable->aCol[p->aiColumn[nEq-1]].affinity;
+  rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq-1, &bOk);
+  pBuilder->pRec = pRec;
+  if( rc!=SQLITE_OK ) return rc;
+  if( bOk==0 ) return SQLITE_NOTFOUND;
+  pBuilder->nRecValid = nEq;
+
+  whereKeyStats(pParse, p, pRec, 0, a);
+  WHERETRACE(0x10,("equality scan regions: %d\n", (int)a[1]));
+  *pnRow = a[1];
+  
+  return rc;
+}
+#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
+
+#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+/*
+** Estimate the number of rows that will be returned based on
+** an IN constraint where the right-hand side of the IN operator
+** is a list of values.  Example:
+**
+**        WHERE x IN (1,2,3,4)
+**
+** Write the estimated row count into *pnRow and return SQLITE_OK. 
+** If unable to make an estimate, leave *pnRow unchanged and return
+** non-zero.
+**
+** This routine can fail if it is unable to load a collating sequence
+** required for string comparison, or if unable to allocate memory
+** for a UTF conversion required for comparison.  The error is stored
+** in the pParse structure.
+*/
+static int whereInScanEst(
+  Parse *pParse,       /* Parsing & code generating context */
+  WhereLoopBuilder *pBuilder,
+  ExprList *pList,     /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
+  tRowcnt *pnRow       /* Write the revised row estimate here */
+){
+  Index *p = pBuilder->pNew->u.btree.pIndex;
+  i64 nRow0 = sqlite3LogEstToInt(p->aiRowLogEst[0]);
+  int nRecValid = pBuilder->nRecValid;
+  int rc = SQLITE_OK;     /* Subfunction return code */
+  tRowcnt nEst;           /* Number of rows for a single term */
+  tRowcnt nRowEst = 0;    /* New estimate of the number of rows */
+  int i;                  /* Loop counter */
+
+  assert( p->aSample!=0 );
+  for(i=0; rc==SQLITE_OK && i<pList->nExpr; i++){
+    nEst = nRow0;
+    rc = whereEqualScanEst(pParse, pBuilder, pList->a[i].pExpr, &nEst);
+    nRowEst += nEst;
+    pBuilder->nRecValid = nRecValid;
   }
 
-  return pLevel->notReady;
+  if( rc==SQLITE_OK ){
+    if( nRowEst > nRow0 ) nRowEst = nRow0;
+    *pnRow = nRowEst;
+    WHERETRACE(0x10,("IN row estimate: est=%d\n", nRowEst));
+  }
+  assert( pBuilder->nRecValid==nRecValid );
+  return rc;
 }
+#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
+
 
 #ifdef WHERETRACE_ENABLED
 /*
@@ -120331,9 +121724,10 @@ static void whereTermPrint(WhereTerm *pTerm, int iTerm){
     if( pTerm->wtFlags & TERM_VIRTUAL ) zType[0] = 'V';
     if( pTerm->eOperator & WO_EQUIV  ) zType[1] = 'E';
     if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) zType[2] = 'L';
-    sqlite3DebugPrintf("TERM-%-3d %p %s cursor=%-3d prob=%-3d op=0x%03x\n",
-                       iTerm, pTerm, zType, pTerm->leftCursor, pTerm->truthProb,
-                       pTerm->eOperator);
+    sqlite3DebugPrintf(
+       "TERM-%-3d %p %s cursor=%-3d prob=%-3d op=0x%03x wtFlags=0x%04x\n",
+       iTerm, pTerm, zType, pTerm->leftCursor, pTerm->truthProb,
+       pTerm->eOperator, pTerm->wtFlags);
     sqlite3TreeViewExpr(0, pTerm->pExpr, 0);
   }
 }
@@ -120482,7 +121876,7 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
         sqlite3DbFree(db, pLevel->u.in.aInLoop);
       }
     }
-    whereClauseClear(&pWInfo->sWC);
+    sqlite3WhereClauseClear(&pWInfo->sWC);
     while( pWInfo->pLoops ){
       WhereLoop *p = pWInfo->pLoops;
       pWInfo->pLoops = p->pNextLoop;
@@ -120823,8 +122217,9 @@ static void whereLoopOutputAdjust(
         /* In the absence of explicit truth probabilities, use heuristics to
         ** guess a reasonable truth probability. */
         pLoop->nOut--;
-        if( pTerm->eOperator&WO_EQ ){
+        if( pTerm->eOperator&(WO_EQ|WO_IS) ){
           Expr *pRight = pTerm->pExpr->pRight;
+          testcase( pTerm->pExpr->op==TK_IS );
           if( sqlite3ExprIsInteger(pRight, &k) && k>=(-1) && k<=1 ){
             k = 10;
           }else{
@@ -120892,10 +122287,10 @@ static int whereLoopAddBtreeIndex(
   assert( (pNew->wsFlags & WHERE_TOP_LIMIT)==0 );
   if( pNew->wsFlags & WHERE_BTM_LIMIT ){
     opMask = WO_LT|WO_LE;
-  }else if( pProbe->tnum<=0 || (pSrc->jointype & JT_LEFT)!=0 ){
+  }else if( /*pProbe->tnum<=0 ||*/ (pSrc->jointype & JT_LEFT)!=0 ){
     opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE;
   }else{
-    opMask = WO_EQ|WO_IN|WO_ISNULL|WO_GT|WO_GE|WO_LT|WO_LE;
+    opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE|WO_ISNULL|WO_IS;
   }
   if( pProbe->bUnordered ) opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);
 
@@ -120958,7 +122353,7 @@ static int whereLoopAddBtreeIndex(
       assert( nIn>0 );  /* RHS always has 2 or more terms...  The parser
                         ** changes "x IN (?)" into "x=?". */
 
-    }else if( eOp & (WO_EQ) ){
+    }else if( eOp & (WO_EQ|WO_IS) ){
       pNew->wsFlags |= WHERE_COLUMN_EQ;
       if( iCol<0 || (nInMul==0 && pNew->u.btree.nEq==pProbe->nKeyCol-1) ){
         if( iCol>=0 && pProbe->uniqNotNull==0 ){
@@ -121008,7 +122403,7 @@ static int whereLoopAddBtreeIndex(
       whereRangeScanEst(pParse, pBuilder, pBtm, pTop, pNew);
     }else{
       int nEq = ++pNew->u.btree.nEq;
-      assert( eOp & (WO_ISNULL|WO_EQ|WO_IN) );
+      assert( eOp & (WO_ISNULL|WO_EQ|WO_IN|WO_IS) );
 
       assert( pNew->nOut==saved_nOut );
       if( pTerm->truthProb<=0 && iCol>=0 ){
@@ -121025,8 +122420,9 @@ static int whereLoopAddBtreeIndex(
          && ((eOp & WO_IN)==0 || !ExprHasProperty(pTerm->pExpr, EP_xIsSelect))
         ){
           Expr *pExpr = pTerm->pExpr;
-          if( (eOp & (WO_EQ|WO_ISNULL))!=0 ){
+          if( (eOp & (WO_EQ|WO_ISNULL|WO_IS))!=0 ){
             testcase( eOp & WO_EQ );
+            testcase( eOp & WO_IS );
             testcase( eOp & WO_ISNULL );
             rc = whereEqualScanEst(pParse, pBuilder, pExpr->pRight, &nOut);
           }else{
@@ -121295,15 +122691,14 @@ static int whereLoopAddBtree(
 
 #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
   /* Automatic indexes */
-  if( !pBuilder->pOrSet
+  if( !pBuilder->pOrSet   /* Not part of an OR optimization */
    && (pWInfo->wctrlFlags & WHERE_NO_AUTOINDEX)==0
    && (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
-   && pSrc->pIndex==0
-   && !pSrc->viaCoroutine
-   && !pSrc->notIndexed
-   && HasRowid(pTab)
-   && !pSrc->isCorrelated
-   && !pSrc->isRecursive
+   && pSrc->pIndex==0     /* Has no INDEXED BY clause */
+   && !pSrc->notIndexed   /* Has no NOT INDEXED clause */
+   && HasRowid(pTab)      /* Is not a WITHOUT ROWID table. (FIXME: Why not?) */
+   && !pSrc->isCorrelated /* Not a correlated subquery */
+   && !pSrc->isRecursive  /* Not a recursive common table expression. */
   ){
     /* Generate auto-index WhereLoops */
     WhereTerm *pTerm;
@@ -121433,10 +122828,32 @@ static int whereLoopAddBtree(
 /*
 ** Add all WhereLoop objects for a table of the join identified by
 ** pBuilder->pNew->iTab.  That table is guaranteed to be a virtual table.
+**
+** If there are no LEFT or CROSS JOIN joins in the query, both mExtra and
+** mUnusable are set to 0. Otherwise, mExtra is a mask of all FROM clause
+** entries that occur before the virtual table in the FROM clause and are
+** separated from it by at least one LEFT or CROSS JOIN. Similarly, the
+** mUnusable mask contains all FROM clause entries that occur after the
+** virtual table and are separated from it by at least one LEFT or 
+** CROSS JOIN. 
+**
+** For example, if the query were:
+**
+**   ... FROM t1, t2 LEFT JOIN t3, t4, vt CROSS JOIN t5, t6;
+**
+** then mExtra corresponds to (t1, t2) and mUnusable to (t5, t6).
+**
+** All the tables in mExtra must be scanned before the current virtual 
+** table. So any terms for which all prerequisites are satisfied by 
+** mExtra may be specified as "usable" in all calls to xBestIndex. 
+** Conversely, all tables in mUnusable must be scanned after the current
+** virtual table, so any terms for which the prerequisites overlap with
+** mUnusable should always be configured as "not-usable" for xBestIndex.
 */
 static int whereLoopAddVirtual(
   WhereLoopBuilder *pBuilder,  /* WHERE clause information */
-  Bitmask mExtra
+  Bitmask mExtra,              /* Tables that must be scanned before this one */
+  Bitmask mUnusable            /* Tables that must be scanned after this one */
 ){
   WhereInfo *pWInfo;           /* WHERE analysis context */
   Parse *pParse;               /* The parsing context */
@@ -121457,6 +122874,7 @@ static int whereLoopAddVirtual(
   WhereLoop *pNew;
   int rc = SQLITE_OK;
 
+  assert( (mExtra & mUnusable)==0 );
   pWInfo = pBuilder->pWInfo;
   pParse = pWInfo->pParse;
   db = pParse->db;
@@ -121465,7 +122883,7 @@ static int whereLoopAddVirtual(
   pSrc = &pWInfo->pTabList->a[pNew->iTab];
   pTab = pSrc->pTab;
   assert( IsVirtual(pTab) );
-  pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pBuilder->pOrderBy);
+  pIdxInfo = allocateIndexInfo(pParse, pWC, mUnusable, pSrc,pBuilder->pOrderBy);
   if( pIdxInfo==0 ) return SQLITE_NOMEM;
   pNew->prereq = 0;
   pNew->rSetup = 0;
@@ -121495,7 +122913,7 @@ static int whereLoopAddVirtual(
           if( (pTerm->eOperator & WO_IN)!=0 ){
             seenIn = 1;
           }
-          if( pTerm->prereqRight!=0 ){
+          if( (pTerm->prereqRight & ~mExtra)!=0 ){
             seenVar = 1;
           }else if( (pTerm->eOperator & WO_IN)==0 ){
             pIdxCons->usable = 1;
@@ -121503,7 +122921,7 @@ static int whereLoopAddVirtual(
           break;
         case 1:    /* Constants with IN operators */
           assert( seenIn );
-          pIdxCons->usable = (pTerm->prereqRight==0);
+          pIdxCons->usable = (pTerm->prereqRight & ~mExtra)==0;
           break;
         case 2:    /* Variables without IN */
           assert( seenVar );
@@ -121602,7 +123020,11 @@ whereLoopAddVtab_exit:
 ** Add WhereLoop entries to handle OR terms.  This works for either
 ** btrees or virtual tables.
 */
-static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
+static int whereLoopAddOr(
+  WhereLoopBuilder *pBuilder, 
+  Bitmask mExtra, 
+  Bitmask mUnusable
+){
   WhereInfo *pWInfo = pBuilder->pWInfo;
   WhereClause *pWC;
   WhereLoop *pNew;
@@ -121661,14 +123083,14 @@ static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
 #endif
 #ifndef SQLITE_OMIT_VIRTUALTABLE
         if( IsVirtual(pItem->pTab) ){
-          rc = whereLoopAddVirtual(&sSubBuild, mExtra);
+          rc = whereLoopAddVirtual(&sSubBuild, mExtra, mUnusable);
         }else
 #endif
         {
           rc = whereLoopAddBtree(&sSubBuild, mExtra);
         }
         if( rc==SQLITE_OK ){
-          rc = whereLoopAddOr(&sSubBuild, mExtra);
+          rc = whereLoopAddOr(&sSubBuild, mExtra, mUnusable);
         }
         assert( rc==SQLITE_OK || sCur.n==0 );
         if( sCur.n==0 ){
@@ -121730,33 +123152,43 @@ static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
   int iTab;
   SrcList *pTabList = pWInfo->pTabList;
   struct SrcList_item *pItem;
+  struct SrcList_item *pEnd = &pTabList->a[pWInfo->nLevel];
   sqlite3 *db = pWInfo->pParse->db;
-  int nTabList = pWInfo->nLevel;
   int rc = SQLITE_OK;
-  u8 priorJoinType = 0;
   WhereLoop *pNew;
+  u8 priorJointype = 0;
 
   /* Loop over the tables in the join, from left to right */
   pNew = pBuilder->pNew;
   whereLoopInit(pNew);
-  for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
+  for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
+    Bitmask mUnusable = 0;
     pNew->iTab = iTab;
-    pNew->maskSelf = getMask(&pWInfo->sMaskSet, pItem->iCursor);
-    if( ((pItem->jointype|priorJoinType) & (JT_LEFT|JT_CROSS))!=0 ){
+    pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
+    if( ((pItem->jointype|priorJointype) & (JT_LEFT|JT_CROSS))!=0 ){
+      /* This condition is true when pItem is the FROM clause term on the
+      ** right-hand-side of a LEFT or CROSS JOIN.  */
       mExtra = mPrior;
     }
-    priorJoinType = pItem->jointype;
+    priorJointype = pItem->jointype;
     if( IsVirtual(pItem->pTab) ){
-      rc = whereLoopAddVirtual(pBuilder, mExtra);
+      struct SrcList_item *p;
+      for(p=&pItem[1]; p<pEnd; p++){
+        if( mUnusable || (p->jointype & (JT_LEFT|JT_CROSS)) ){
+          mUnusable |= sqlite3WhereGetMask(&pWInfo->sMaskSet, p->iCursor);
+        }
+      }
+      rc = whereLoopAddVirtual(pBuilder, mExtra, mUnusable);
     }else{
       rc = whereLoopAddBtree(pBuilder, mExtra);
     }
     if( rc==SQLITE_OK ){
-      rc = whereLoopAddOr(pBuilder, mExtra);
+      rc = whereLoopAddOr(pBuilder, mExtra, mUnusable);
     }
     mPrior |= pNew->maskSelf;
     if( rc || db->mallocFailed ) break;
   }
+
   whereLoopClear(db, pNew);
   return rc;
 }
@@ -121862,10 +123294,10 @@ static i8 wherePathSatisfiesOrderBy(
       pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
       if( pOBExpr->op!=TK_COLUMN ) continue;
       if( pOBExpr->iTable!=iCur ) continue;
-      pTerm = findTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
-                       ~ready, WO_EQ|WO_ISNULL, 0);
+      pTerm = sqlite3WhereFindTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
+                       ~ready, WO_EQ|WO_ISNULL|WO_IS, 0);
       if( pTerm==0 ) continue;
-      if( (pTerm->eOperator&WO_EQ)!=0 && pOBExpr->iColumn>=0 ){
+      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
         const char *z1, *z2;
         pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
         if( !pColl ) pColl = db->pDfltColl;
@@ -121874,6 +123306,7 @@ static i8 wherePathSatisfiesOrderBy(
         if( !pColl ) pColl = db->pDfltColl;
         z2 = pColl->zName;
         if( sqlite3StrICmp(z1, z2)!=0 ) continue;
+        testcase( pTerm->pExpr->op==TK_IS );
       }
       obSat |= MASKBIT(i);
     }
@@ -121904,7 +123337,7 @@ static i8 wherePathSatisfiesOrderBy(
         /* Skip over == and IS NULL terms */
         if( j<pLoop->u.btree.nEq
          && pLoop->nSkip==0
-         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL))!=0
+         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL|WO_IS))!=0
         ){
           if( i & WO_ISNULL ){
             testcase( isOrderDistinct );
@@ -121998,7 +123431,7 @@ static i8 wherePathSatisfiesOrderBy(
         Bitmask mTerm;
         if( MASKBIT(i) & obSat ) continue;
         p = pOrderBy->a[i].pExpr;
-        mTerm = exprTableUsage(&pWInfo->sMaskSet,p);
+        mTerm = sqlite3WhereExprUsage(&pWInfo->sMaskSet,p);
         if( mTerm==0 && !sqlite3ExprIsConstant(p) ) continue;
         if( (mTerm&~orderDistinctMask)==0 ){
           obSat |= MASKBIT(i);
@@ -122471,14 +123904,15 @@ static int whereShortCut(WhereLoopBuilder *pBuilder){
   pItem = pWInfo->pTabList->a;
   pTab = pItem->pTab;
   if( IsVirtual(pTab) ) return 0;
-  if( pItem->zIndex ) return 0;
+  if( pItem->zIndexedBy ) return 0;
   iCur = pItem->iCursor;
   pWC = &pWInfo->sWC;
   pLoop = pBuilder->pNew;
   pLoop->wsFlags = 0;
   pLoop->nSkip = 0;
-  pTerm = findTerm(pWC, iCur, -1, 0, WO_EQ, 0);
+  pTerm = sqlite3WhereFindTerm(pWC, iCur, -1, 0, WO_EQ|WO_IS, 0);
   if( pTerm ){
+    testcase( pTerm->eOperator & WO_IS );
     pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_IPK|WHERE_ONEROW;
     pLoop->aLTerm[0] = pTerm;
     pLoop->nLTerm = 1;
@@ -122487,14 +123921,17 @@ static int whereShortCut(WhereLoopBuilder *pBuilder){
     pLoop->rRun = 33;  /* 33==sqlite3LogEst(10) */
   }else{
     for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int opMask;
       assert( pLoop->aLTermSpace==pLoop->aLTerm );
       if( !IsUniqueIndex(pIdx)
        || pIdx->pPartIdxWhere!=0 
        || pIdx->nKeyCol>ArraySize(pLoop->aLTermSpace) 
       ) continue;
+      opMask = pIdx->uniqNotNull ? (WO_EQ|WO_IS) : WO_EQ;
       for(j=0; j<pIdx->nKeyCol; j++){
-        pTerm = findTerm(pWC, iCur, pIdx->aiColumn[j], 0, WO_EQ, pIdx);
+        pTerm = sqlite3WhereFindTerm(pWC, iCur, pIdx->aiColumn[j], 0, opMask, pIdx);
         if( pTerm==0 ) break;
+        testcase( pTerm->eOperator & WO_IS );
         pLoop->aLTerm[j] = pTerm;
       }
       if( j!=pIdx->nKeyCol ) continue;
@@ -122513,7 +123950,7 @@ static int whereShortCut(WhereLoopBuilder *pBuilder){
   if( pLoop->wsFlags ){
     pLoop->nOut = (LogEst)1;
     pWInfo->a[0].pWLoop = pLoop;
-    pLoop->maskSelf = getMask(&pWInfo->sMaskSet, iCur);
+    pLoop->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur);
     pWInfo->a[0].iTabCur = iCur;
     pWInfo->nRowOut = 1;
     if( pWInfo->pOrderBy ) pWInfo->nOBSat =  pWInfo->pOrderBy->nExpr;
@@ -122707,8 +124144,8 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
   ** subexpression is separated by an AND operator.
   */
   initMaskSet(pMaskSet);
-  whereClauseInit(&pWInfo->sWC, pWInfo);
-  whereSplit(&pWInfo->sWC, pWhere, TK_AND);
+  sqlite3WhereClauseInit(&pWInfo->sWC, pWInfo);
+  sqlite3WhereSplit(&pWInfo->sWC, pWhere, TK_AND);
     
   /* Special case: a WHERE clause that is constant.  Evaluate the
   ** expression and either jump over all of the code or fall thru.
@@ -122753,22 +124190,16 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
   {
     Bitmask toTheLeft = 0;
     for(ii=0; ii<pTabList->nSrc; ii++){
-      Bitmask m = getMask(pMaskSet, pTabList->a[ii].iCursor);
+      Bitmask m = sqlite3WhereGetMask(pMaskSet, pTabList->a[ii].iCursor);
       assert( (m-1)==toTheLeft );
       toTheLeft |= m;
     }
   }
 #endif
 
-  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
-  ** add new virtual terms onto the end of the WHERE clause.  We do not
-  ** want to analyze these virtual terms, so start analyzing at the end
-  ** and work forward so that the added virtual terms are never processed.
-  */
-  exprAnalyzeAll(pTabList, &pWInfo->sWC);
-  if( db->mallocFailed ){
-    goto whereBeginError;
-  }
+  /* Analyze all of the subexpressions. */
+  sqlite3WhereExprAnalyze(pTabList, &pWInfo->sWC);
+  if( db->mallocFailed ) goto whereBeginError;
 
   if( wctrlFlags & WHERE_WANT_DISTINCT ){
     if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
@@ -122784,8 +124215,7 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
   /* Construct the WhereLoop objects */
   WHERETRACE(0xffff,("*** Optimizer Start ***\n"));
 #if defined(WHERETRACE_ENABLED)
-  /* Display all terms of the WHERE clause */
-  if( sqlite3WhereTrace & 0x100 ){
+  if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
     int i;
     for(i=0; i<sWLB.pWC->nTerm; i++){
       whereTermPrint(&sWLB.pWC->a[i], i);
@@ -122797,13 +124227,12 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
     rc = whereLoopAddAll(&sWLB);
     if( rc ) goto whereBeginError;
   
-    /* Display all of the WhereLoop objects if wheretrace is enabled */
-#ifdef WHERETRACE_ENABLED /* !=0 */
-    if( sqlite3WhereTrace ){
+#ifdef WHERETRACE_ENABLED
+    if( sqlite3WhereTrace ){    /* Display all of the WhereLoop objects */
       WhereLoop *p;
       int i;
-      static char zLabel[] = "0123456789abcdefghijklmnopqrstuvwyxz"
-                                       "ABCDEFGHIJKLMNOPQRSTUVWYXZ";
+      static const char zLabel[] = "0123456789abcdefghijklmnopqrstuvwyxz"
+                                             "ABCDEFGHIJKLMNOPQRSTUVWYXZ";
       for(p=pWInfo->pLoops, i=0; p; p=p->pNextLoop, i++){
         p->cId = zLabel[i%sizeof(zLabel)];
         whereLoopPrint(p, sWLB.pWC);
@@ -122824,7 +124253,7 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
   if( pParse->nErr || NEVER(db->mallocFailed) ){
     goto whereBeginError;
   }
-#ifdef WHERETRACE_ENABLED /* !=0 */
+#ifdef WHERETRACE_ENABLED
   if( sqlite3WhereTrace ){
     sqlite3DebugPrintf("---- Solution nRow=%d", pWInfo->nRowOut);
     if( pWInfo->nOBSat>0 ){
@@ -122855,8 +124284,10 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
    && pResultSet!=0
    && OptimizationEnabled(db, SQLITE_OmitNoopJoin)
   ){
-    Bitmask tabUsed = exprListTableUsage(pMaskSet, pResultSet);
-    if( sWLB.pOrderBy ) tabUsed |= exprListTableUsage(pMaskSet, sWLB.pOrderBy);
+    Bitmask tabUsed = sqlite3WhereExprListUsage(pMaskSet, pResultSet);
+    if( sWLB.pOrderBy ){
+      tabUsed |= sqlite3WhereExprListUsage(pMaskSet, sWLB.pOrderBy);
+    }
     while( pWInfo->nLevel>=2 ){
       WhereTerm *pTerm, *pEnd;
       pLoop = pWInfo->a[pWInfo->nLevel-1].pWLoop;
@@ -122887,7 +124318,7 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
   /* If the caller is an UPDATE or DELETE statement that is requesting
   ** to use a one-pass algorithm, determine if this is appropriate.
   ** The one-pass algorithm only works if the WHERE clause constrains
-  ** the statement to update a single row.
+  ** the statement to update or delete a single row.
   */
   assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
   if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 
@@ -122901,7 +124332,6 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
   /* Open all tables in the pTabList and any indices selected for
   ** searching those tables.
   */
-  notReady = ~(Bitmask)0;
   for(ii=0, pLevel=pWInfo->a; ii<nTabList; ii++, pLevel++){
     Table *pTab;     /* Table to open */
     int iDb;         /* Index of database containing table/index */
@@ -122942,6 +124372,10 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
                             SQLITE_INT_TO_PTR(n), P4_INT32);
         assert( n<=pTab->nCol );
       }
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+      sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, pTabItem->iCursor, 0, 0,
+                            (const u8*)&pTabItem->colUsed, P4_INT64);
+#endif
     }else{
       sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
     }
@@ -122987,10 +124421,24 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
           sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ); /* Hint to COMDB2 */
         }
         VdbeComment((v, "%s", pIx->zName));
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+        {
+          u64 colUsed = 0;
+          int ii, jj;
+          for(ii=0; ii<pIx->nColumn; ii++){
+            jj = pIx->aiColumn[ii];
+            if( jj<0 ) continue;
+            if( jj>63 ) jj = 63;
+            if( (pTabItem->colUsed & MASKBIT(jj))==0 ) continue;
+            colUsed |= ((u64)1)<<(ii<63 ? ii : 63);
+          }
+          sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, iIndexCur, 0, 0,
+                                (u8*)&colUsed, P4_INT64);
+        }
+#endif /* SQLITE_ENABLE_COLUMN_USED_MASK */
       }
     }
     if( iDb>=0 ) sqlite3CodeVerifySchema(pParse, iDb);
-    notReady &= ~getMask(&pWInfo->sMaskSet, pTabItem->iCursor);
   }
   pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
   if( db->mallocFailed ) goto whereBeginError;
@@ -123012,14 +124460,14 @@ SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(
       if( db->mallocFailed ) goto whereBeginError;
     }
 #endif
-    addrExplain = explainOneScan(
+    addrExplain = sqlite3WhereExplainOneScan(
         pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags
     );
     pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
-    notReady = codeOneLoopStart(pWInfo, ii, notReady);
+    notReady = sqlite3WhereCodeOneLoopStart(pWInfo, ii, notReady);
     pWInfo->iContinue = pLevel->addrCont;
     if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_ONETABLE_ONLY)==0 ){
-      addScanStatus(v, pTabList, pLevel, addrExplain);
+      sqlite3WhereAddScanStatus(v, pTabList, pLevel, addrExplain);
     }
   }
 
@@ -123133,26 +124581,12 @@ SQLITE_PRIVATE void sqlite3WhereEnd(WhereInfo *pWInfo){
     pLoop = pLevel->pWLoop;
 
     /* For a co-routine, change all OP_Column references to the table of
-    ** the co-routine into OP_SCopy of result contained in a register.
+    ** the co-routine into OP_Copy of result contained in a register.
     ** OP_Rowid becomes OP_Null.
     */
     if( pTabItem->viaCoroutine && !db->mallocFailed ){
-      last = sqlite3VdbeCurrentAddr(v);
-      k = pLevel->addrBody;
-      pOp = sqlite3VdbeGetOp(v, k);
-      for(; k<last; k++, pOp++){
-        if( pOp->p1!=pLevel->iTabCur ) continue;
-        if( pOp->opcode==OP_Column ){
-          pOp->opcode = OP_Copy;
-          pOp->p1 = pOp->p2 + pTabItem->regResult;
-          pOp->p2 = pOp->p3;
-          pOp->p3 = 0;
-        }else if( pOp->opcode==OP_Rowid ){
-          pOp->opcode = OP_Null;
-          pOp->p1 = 0;
-          pOp->p3 = 0;
-        }
-      }
+      translateColumnToCopy(v, pLevel->addrBody, pLevel->iTabCur,
+                            pTabItem->regResult);
       continue;
     }
 
@@ -123242,6 +124676,7 @@ SQLITE_PRIVATE void sqlite3WhereEnd(WhereInfo *pWInfo){
 ** in the input grammar file. */
 /* #include <stdio.h> */
 
+/* #include "sqliteInt.h" */
 
 /*
 ** Disable all error recovery processing in the parser push-down
@@ -124719,7 +126154,7 @@ static int yy_pop_parser_stack(yyParser *pParser){
 
   /* There is no mechanism by which the parser stack can be popped below
   ** empty in SQLite.  */
-  if( NEVER(pParser->yyidx<0) ) return 0;
+  assert( pParser->yyidx>=0 );
 #ifndef NDEBUG
   if( yyTraceFILE && pParser->yyidx>=0 ){
     fprintf(yyTraceFILE,"%sPopping %s\n",
@@ -125420,7 +126855,7 @@ static void yy_reduce(
       case 35: /* table_options ::= WITHOUT nm */
 {
   if( yymsp[0].minor.yy0.n==5 && sqlite3_strnicmp(yymsp[0].minor.yy0.z,"rowid",5)==0 ){
-    yygotominor.yy186 = TF_WithoutRowid;
+    yygotominor.yy186 = TF_WithoutRowid | TF_NoVisibleRowid;
   }else{
     yygotominor.yy186 = 0;
     sqlite3ErrorMsg(pParse, "unknown table option: %.*s", yymsp[0].minor.yy0.n, yymsp[0].minor.yy0.z);
@@ -125644,6 +127079,7 @@ static void yy_reduce(
       case 114: /* selectnowith ::= selectnowith multiselect_op oneselect */
 {
   Select *pRhs = yymsp[0].minor.yy3;
+  Select *pLhs = yymsp[-2].minor.yy3;
   if( pRhs && pRhs->pPrior ){
     SrcList *pFrom;
     Token x;
@@ -125654,11 +127090,12 @@ static void yy_reduce(
   }
   if( pRhs ){
     pRhs->op = (u8)yymsp[-1].minor.yy328;
-    pRhs->pPrior = yymsp[-2].minor.yy3;
+    pRhs->pPrior = pLhs;
+    if( ALWAYS(pLhs) ) pLhs->selFlags &= ~SF_MultiValue;
     pRhs->selFlags &= ~SF_MultiValue;
     if( yymsp[-1].minor.yy328!=TK_ALL ) pParse->hasCompound = 1;
   }else{
-    sqlite3SelectDelete(pParse->db, yymsp[-2].minor.yy3);
+    sqlite3SelectDelete(pParse->db, pLhs);
   }
   yygotominor.yy3 = pRhs;
 }
@@ -125719,7 +127156,9 @@ static void yy_reduce(
 {yygotominor.yy381 = SF_Distinct;}
         break;
       case 123: /* distinct ::= ALL */
-      case 124: /* distinct ::= */ yytestcase(yyruleno==124);
+{yygotominor.yy381 = SF_All;}
+        break;
+      case 124: /* distinct ::= */
 {yygotominor.yy381 = 0;}
         break;
       case 125: /* sclp ::= selcollist COMMA */
@@ -126014,7 +127453,7 @@ static void yy_reduce(
   }
   yygotominor.yy346.pExpr = sqlite3ExprFunction(pParse, yymsp[-1].minor.yy14, &yymsp[-4].minor.yy0);
   spanSet(&yygotominor.yy346,&yymsp[-4].minor.yy0,&yymsp[0].minor.yy0);
-  if( yymsp[-2].minor.yy381 && yygotominor.yy346.pExpr ){
+  if( yymsp[-2].minor.yy381==SF_Distinct && yygotominor.yy346.pExpr ){
     yygotominor.yy346.pExpr->flags |= EP_Distinct;
   }
 }
@@ -126823,6 +128262,7 @@ SQLITE_PRIVATE void sqlite3Parser(
 ** individual tokens and sends those tokens one-by-one over to the
 ** parser for analysis.
 */
+/* #include "sqliteInt.h" */
 /* #include <stdlib.h> */
 
 /*
@@ -127187,7 +128627,11 @@ SQLITE_PRIVATE const char sqlite3IsEbcdicIdChar[] = {
 };
 #define IdChar(C)  (((c=C)>=0x42 && sqlite3IsEbcdicIdChar[c-0x40]))
 #endif
+
+/* Make the IdChar function accessible from ctime.c */
+#ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
 SQLITE_PRIVATE int sqlite3IsIdChar(u8 c){ return IdChar(c); }
+#endif
 
 
 /*
@@ -127535,7 +128979,8 @@ SQLITE_PRIVATE int sqlite3RunParser(Parse *pParse, const char *zSql, char **pzEr
   }
 abort_parse:
   assert( nErr==0 );
-  if( zSql[i]==0 && pParse->rc==SQLITE_OK && db->mallocFailed==0 ){
+  if( pParse->rc==SQLITE_OK && db->mallocFailed==0 ){
+    assert( zSql[i]==0 );
     if( lastTokenParsed!=TK_SEMI ){
       sqlite3Parser(pEngine, TK_SEMI, pParse->sLastToken, pParse);
       pParse->zTail = &zSql[i];
@@ -127557,7 +129002,7 @@ abort_parse:
     pParse->rc = SQLITE_NOMEM;
   }
   if( pParse->rc!=SQLITE_OK && pParse->rc!=SQLITE_DONE && pParse->zErrMsg==0 ){
-    sqlite3SetString(&pParse->zErrMsg, db, "%s", sqlite3ErrStr(pParse->rc));
+    pParse->zErrMsg = sqlite3MPrintf(db, "%s", sqlite3ErrStr(pParse->rc));
   }
   assert( pzErrMsg!=0 );
   if( pParse->zErrMsg ){
@@ -127627,6 +129072,7 @@ abort_parse:
 ** separating it out, the code will be automatically omitted from
 ** static links that do not use it.
 */
+/* #include "sqliteInt.h" */
 #ifndef SQLITE_OMIT_COMPLETE
 
 /*
@@ -127894,7 +129340,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_complete16(const void *zSql){
     rc = SQLITE_NOMEM;
   }
   sqlite3ValueFree(pVal);
-  return sqlite3ApiExit(0, rc);
+  return rc & 0xff;
 }
 #endif /* SQLITE_OMIT_UTF16 */
 #endif /* SQLITE_OMIT_COMPLETE */
@@ -127917,6 +129363,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_complete16(const void *zSql){
 ** other files are for internal use by SQLite and should not be
 ** accessed by users of the library.
 */
+/* #include "sqliteInt.h" */
 
 #ifdef SQLITE_ENABLE_FTS3
 /************** Include fts3.h in the middle of main.c ***********************/
@@ -127936,6 +129383,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_complete16(const void *zSql){
 ** This header file is used by programs that want to link against the
 ** FTS3 library.  All it does is declare the sqlite3Fts3Init() interface.
 */
+/* #include "sqlite3.h" */
 
 #if 0
 extern "C" {
@@ -127968,6 +129416,7 @@ SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db);
 ** This header file is used by programs that want to link against the
 ** RTREE library.  All it does is declare the sqlite3RtreeInit() interface.
 */
+/* #include "sqlite3.h" */
 
 #if 0
 extern "C" {
@@ -128000,6 +129449,7 @@ SQLITE_PRIVATE int sqlite3RtreeInit(sqlite3 *db);
 ** This header file is used by programs that want to link against the
 ** ICU extension.  All it does is declare the sqlite3IcuInit() interface.
 */
+/* #include "sqlite3.h" */
 
 #if 0
 extern "C" {
@@ -128632,6 +130082,7 @@ SQLITE_API int SQLITE_CDECL sqlite3_config(int op, ...){
 ** the lookaside memory.
 */
 static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
+#ifndef SQLITE_OMIT_LOOKASIDE
   void *pStart;
   if( db->lookaside.nOut ){
     return SQLITE_BUSY;
@@ -128682,6 +130133,7 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
     db->lookaside.bEnabled = 0;
     db->lookaside.bMalloced = 0;
   }
+#endif /* SQLITE_OMIT_LOOKASIDE */
   return SQLITE_OK;
 }
 
@@ -130072,9 +131524,11 @@ SQLITE_PRIVATE int sqlite3TempInMemory(const sqlite3 *db){
   return ( db->temp_store!=1 );
 #endif
 #if SQLITE_TEMP_STORE==3
+  UNUSED_PARAMETER(db);
   return 1;
 #endif
 #if SQLITE_TEMP_STORE<1 || SQLITE_TEMP_STORE>3
+  UNUSED_PARAMETER(db);
   return 0;
 #endif
 }
@@ -130748,6 +132202,9 @@ static int openDatabase(
 #endif
 #if defined(SQLITE_REVERSE_UNORDERED_SELECTS)
                  | SQLITE_ReverseOrder
+#endif
+#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
+                 | SQLITE_CellSizeCk
 #endif
       ;
   sqlite3HashInit(&db->aCollSeq);
@@ -130868,8 +132325,7 @@ static int openDatabase(
 
 #ifdef SQLITE_ENABLE_DBSTAT_VTAB
   if( !db->mallocFailed && rc==SQLITE_OK){
-    int sqlite3_dbstat_register(sqlite3*);
-    rc = sqlite3_dbstat_register(db);
+    rc = sqlite3DbstatRegister(db);
   }
 #endif
 
@@ -130914,7 +132370,7 @@ opendb_out:
     sqlite3GlobalConfig.xSqllog(pArg, db, zFilename, 0);
   }
 #endif
-  return sqlite3ApiExit(0, rc);
+  return rc & 0xff;
 }
 
 /*
@@ -130972,7 +132428,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_open16(
   }
   sqlite3ValueFree(pVal);
 
-  return sqlite3ApiExit(0, rc);
+  return rc & 0xff;
 }
 #endif /* SQLITE_OMIT_UTF16 */
 
@@ -131344,7 +132800,9 @@ SQLITE_API int SQLITE_STDCALL sqlite3_file_control(sqlite3 *db, const char *zDbN
 */
 SQLITE_API int SQLITE_CDECL sqlite3_test_control(int op, ...){
   int rc = 0;
-#ifndef SQLITE_OMIT_BUILTIN_TEST
+#ifdef SQLITE_OMIT_BUILTIN_TEST
+  UNUSED_PARAMETER(op);
+#else
   va_list ap;
   va_start(ap, op);
   switch( op ){
@@ -131786,6 +133244,8 @@ SQLITE_API int SQLITE_STDCALL sqlite3_db_readonly(sqlite3 *db, const char *zDbNa
 ** This file contains the implementation of the sqlite3_unlock_notify()
 ** API method and its associated functionality.
 */
+/* #include "sqliteInt.h" */
+/* #include "btreeInt.h" */
 
 /* Omit this entire file if SQLITE_ENABLE_UNLOCK_NOTIFY is not defined. */
 #ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
@@ -132429,9 +133889,11 @@ SQLITE_PRIVATE void sqlite3ConnectionClosed(sqlite3 *db){
 
 /* If not building as part of the core, include sqlite3ext.h. */
 #ifndef SQLITE_CORE
+/* # include "sqlite3ext.h"  */
 SQLITE_EXTENSION_INIT3
 #endif
 
+/* #include "sqlite3.h" */
 /************** Include fts3_tokenizer.h in the middle of fts3Int.h **********/
 /************** Begin file fts3_tokenizer.h **********************************/
 /*
@@ -132460,6 +133922,7 @@ SQLITE_EXTENSION_INIT3
 ** If tokenizers are to be allowed to call sqlite3_*() functions, then
 ** we will need a way to register the API consistently.
 */
+/* #include "sqlite3.h" */
 
 /*
 ** Structures used by the tokenizer interface. When a new tokenizer
@@ -132873,6 +134336,8 @@ typedef struct Fts3DeferredToken Fts3DeferredToken;
 typedef struct Fts3SegReader Fts3SegReader;
 typedef struct Fts3MultiSegReader Fts3MultiSegReader;
 
+typedef struct MatchinfoBuffer MatchinfoBuffer;
+
 /*
 ** A connection to a fulltext index is an instance of the following
 ** structure. The xCreate and xConnect methods create an instance
@@ -132982,9 +134447,7 @@ struct Fts3Cursor {
   i64 iMinDocid;                  /* Minimum docid to return */
   i64 iMaxDocid;                  /* Maximum docid to return */
   int isMatchinfoNeeded;          /* True when aMatchinfo[] needs filling in */
-  u32 *aMatchinfo;                /* Information about most recent match */
-  int nMatchinfo;                 /* Number of elements in aMatchinfo[] */
-  char *zMatchinfo;               /* Matchinfo specification */
+  MatchinfoBuffer *pMIBuffer;     /* Buffer for matchinfo data */
 };
 
 #define FTS3_EVAL_FILTER    0
@@ -133104,7 +134567,9 @@ struct Fts3Expr {
   u8 bStart;                 /* True if iDocid is valid */
   u8 bDeferred;              /* True if this expression is entirely deferred */
 
-  u32 *aMI;
+  /* The following are used by the fts3_snippet.c module. */
+  int iPhrase;               /* Index of this phrase in matchinfo() results */
+  u32 *aMI;                  /* See above */
 };
 
 /*
@@ -133225,6 +134690,7 @@ SQLITE_PRIVATE void sqlite3Fts3DoclistPrev(int,char*,int,char**,sqlite3_int64*,i
 SQLITE_PRIVATE int sqlite3Fts3EvalPhraseStats(Fts3Cursor *, Fts3Expr *, u32 *);
 SQLITE_PRIVATE int sqlite3Fts3FirstFilter(sqlite3_int64, char *, int, char *);
 SQLITE_PRIVATE void sqlite3Fts3CreateStatTable(int*, Fts3Table*);
+SQLITE_PRIVATE int sqlite3Fts3EvalTestDeferred(Fts3Cursor *pCsr, int *pRc);
 
 /* fts3_tokenizer.c */
 SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *, int *);
@@ -133240,6 +134706,7 @@ SQLITE_PRIVATE void sqlite3Fts3Snippet(sqlite3_context *, Fts3Cursor *, const ch
   const char *, const char *, int, int
 );
 SQLITE_PRIVATE void sqlite3Fts3Matchinfo(sqlite3_context *, Fts3Cursor *, const char *);
+SQLITE_PRIVATE void sqlite3Fts3MIBufferFree(MatchinfoBuffer *p);
 
 /* fts3_expr.c */
 SQLITE_PRIVATE int sqlite3Fts3ExprParse(sqlite3_tokenizer *, int,
@@ -133296,7 +134763,9 @@ SQLITE_PRIVATE int sqlite3FtsUnicodeIsdiacritic(int);
 /* #include <string.h> */
 /* #include <stdarg.h> */
 
+/* #include "fts3.h" */
 #ifndef SQLITE_CORE 
+/* # include "sqlite3ext.h" */
   SQLITE_EXTENSION_INIT1
 #endif
 
@@ -134667,7 +136136,7 @@ static int fts3CloseMethod(sqlite3_vtab_cursor *pCursor){
   sqlite3Fts3ExprFree(pCsr->pExpr);
   sqlite3Fts3FreeDeferredTokens(pCsr);
   sqlite3_free(pCsr->aDoclist);
-  sqlite3_free(pCsr->aMatchinfo);
+  sqlite3Fts3MIBufferFree(pCsr->pMIBuffer);
   assert( ((Fts3Table *)pCsr->base.pVtab)->pSegments==0 );
   sqlite3_free(pCsr);
   return SQLITE_OK;
@@ -136168,7 +137637,7 @@ static int fts3FilterMethod(
   /* In case the cursor has been used before, clear it now. */
   sqlite3_finalize(pCsr->pStmt);
   sqlite3_free(pCsr->aDoclist);
-  sqlite3_free(pCsr->aMatchinfo);
+  sqlite3Fts3MIBufferFree(pCsr->pMIBuffer);
   sqlite3Fts3ExprFree(pCsr->pExpr);
   memset(&pCursor[1], 0, sizeof(Fts3Cursor)-sizeof(sqlite3_vtab_cursor));
 
@@ -137223,7 +138692,6 @@ static int fts3EvalPhraseStart(Fts3Cursor *pCsr, int bOptOk, Fts3Phrase *p){
   int bIncrOk = (bOptOk 
    && pCsr->bDesc==pTab->bDescIdx 
    && p->nToken<=MAX_INCR_PHRASE_TOKENS && p->nToken>0
-   && p->nToken<=MAX_INCR_PHRASE_TOKENS && p->nToken>0
 #ifdef SQLITE_TEST
    && pTab->bNoIncrDoclist==0
 #endif
@@ -137343,6 +138811,7 @@ SQLITE_PRIVATE void sqlite3Fts3DoclistNext(
     p += sqlite3Fts3GetVarint(p, piDocid);
   }else{
     fts3PoslistCopy(0, &p);
+    while( p<&aDoclist[nDoclist] && *p==0 ) p++; 
     if( p>=&aDoclist[nDoclist] ){
       *pbEof = 1;
     }else{
@@ -138066,7 +139535,7 @@ static int fts3EvalNearTrim(
 **   2. NEAR is treated as AND. If the expression is "x NEAR y", it is 
 **      advanced to point to the next row that matches "x AND y".
 ** 
-** See fts3EvalTestDeferredAndNear() for details on testing if a row is
+** See sqlite3Fts3EvalTestDeferred() for details on testing if a row is
 ** really a match, taking into account deferred tokens and NEAR operators.
 */
 static void fts3EvalNextRow(
@@ -138286,7 +139755,7 @@ static int fts3EvalNearTest(Fts3Expr *pExpr, int *pRc){
 }
 
 /*
-** This function is a helper function for fts3EvalTestDeferredAndNear().
+** This function is a helper function for sqlite3Fts3EvalTestDeferred().
 ** Assuming no error occurs or has occurred, It returns non-zero if the
 ** expression passed as the second argument matches the row that pCsr 
 ** currently points to, or zero if it does not.
@@ -138407,7 +139876,7 @@ static int fts3EvalTestExpr(
 ** Or, if no error occurs and it seems the current row does match the FTS
 ** query, return 0.
 */
-static int fts3EvalTestDeferredAndNear(Fts3Cursor *pCsr, int *pRc){
+SQLITE_PRIVATE int sqlite3Fts3EvalTestDeferred(Fts3Cursor *pCsr, int *pRc){
   int rc = *pRc;
   int bMiss = 0;
   if( rc==SQLITE_OK ){
@@ -138454,7 +139923,7 @@ static int fts3EvalNext(Fts3Cursor *pCsr){
       pCsr->isRequireSeek = 1;
       pCsr->isMatchinfoNeeded = 1;
       pCsr->iPrevId = pExpr->iDocid;
-    }while( pCsr->isEof==0 && fts3EvalTestDeferredAndNear(pCsr, &rc) );
+    }while( pCsr->isEof==0 && sqlite3Fts3EvalTestDeferred(pCsr, &rc) );
   }
 
   /* Check if the cursor is past the end of the docid range specified
@@ -138615,7 +140084,7 @@ static int fts3EvalGatherStats(
         pCsr->iPrevId = pRoot->iDocid;
       }while( pCsr->isEof==0 
            && pRoot->eType==FTSQUERY_NEAR 
-           && fts3EvalTestDeferredAndNear(pCsr, &rc) 
+           && sqlite3Fts3EvalTestDeferred(pCsr, &rc) 
       );
 
       if( rc==SQLITE_OK && pCsr->isEof==0 ){
@@ -138640,7 +140109,6 @@ static int fts3EvalGatherStats(
         fts3EvalNextRow(pCsr, pRoot, &rc);
         assert( pRoot->bEof==0 );
       }while( pRoot->iDocid!=iDocid && rc==SQLITE_OK );
-      fts3EvalTestDeferredAndNear(pCsr, &rc);
     }
   }
   return rc;
@@ -138750,10 +140218,10 @@ SQLITE_PRIVATE int sqlite3Fts3EvalPhrasePoslist(
     int rc = SQLITE_OK;
     int bDescDoclist = pTab->bDescIdx;      /* For DOCID_CMP macro */
     int bOr = 0;
-    u8 bEof = 0;
     u8 bTreeEof = 0;
     Fts3Expr *p;                  /* Used to iterate from pExpr to root */
     Fts3Expr *pNear;              /* Most senior NEAR ancestor (or pExpr) */
+    int bMatch;
 
     /* Check if this phrase descends from an OR expression node. If not, 
     ** return NULL. Otherwise, the entry that corresponds to docid 
@@ -138787,31 +140255,47 @@ SQLITE_PRIVATE int sqlite3Fts3EvalPhrasePoslist(
     }
     if( rc!=SQLITE_OK ) return rc;
 
-    pIter = pPhrase->pOrPoslist;
-    iDocid = pPhrase->iOrDocid;
-    if( pCsr->bDesc==bDescDoclist ){
-      bEof = !pPhrase->doclist.nAll ||
-                 (pIter >= (pPhrase->doclist.aAll + pPhrase->doclist.nAll));
-      while( (pIter==0 || DOCID_CMP(iDocid, pCsr->iPrevId)<0 ) && bEof==0 ){
-        sqlite3Fts3DoclistNext(
-            bDescDoclist, pPhrase->doclist.aAll, pPhrase->doclist.nAll, 
-            &pIter, &iDocid, &bEof
-        );
-      }
-    }else{
-      bEof = !pPhrase->doclist.nAll || (pIter && pIter<=pPhrase->doclist.aAll);
-      while( (pIter==0 || DOCID_CMP(iDocid, pCsr->iPrevId)>0 ) && bEof==0 ){
-        int dummy;
-        sqlite3Fts3DoclistPrev(
-            bDescDoclist, pPhrase->doclist.aAll, pPhrase->doclist.nAll, 
-            &pIter, &iDocid, &dummy, &bEof
-        );
+    bMatch = 1;
+    for(p=pNear; p; p=p->pLeft){
+      u8 bEof = 0;
+      Fts3Expr *pTest = p;
+      Fts3Phrase *pPh;
+      assert( pTest->eType==FTSQUERY_NEAR || pTest->eType==FTSQUERY_PHRASE );
+      if( pTest->eType==FTSQUERY_NEAR ) pTest = pTest->pRight;
+      assert( pTest->eType==FTSQUERY_PHRASE );
+      pPh = pTest->pPhrase;
+
+      pIter = pPh->pOrPoslist;
+      iDocid = pPh->iOrDocid;
+      if( pCsr->bDesc==bDescDoclist ){
+        bEof = !pPh->doclist.nAll ||
+          (pIter >= (pPh->doclist.aAll + pPh->doclist.nAll));
+        while( (pIter==0 || DOCID_CMP(iDocid, pCsr->iPrevId)<0 ) && bEof==0 ){
+          sqlite3Fts3DoclistNext(
+              bDescDoclist, pPh->doclist.aAll, pPh->doclist.nAll, 
+              &pIter, &iDocid, &bEof
+          );
+        }
+      }else{
+        bEof = !pPh->doclist.nAll || (pIter && pIter<=pPh->doclist.aAll);
+        while( (pIter==0 || DOCID_CMP(iDocid, pCsr->iPrevId)>0 ) && bEof==0 ){
+          int dummy;
+          sqlite3Fts3DoclistPrev(
+              bDescDoclist, pPh->doclist.aAll, pPh->doclist.nAll, 
+              &pIter, &iDocid, &dummy, &bEof
+              );
+        }
       }
+      pPh->pOrPoslist = pIter;
+      pPh->iOrDocid = iDocid;
+      if( bEof || iDocid!=pCsr->iPrevId ) bMatch = 0;
     }
-    pPhrase->pOrPoslist = pIter;
-    pPhrase->iOrDocid = iDocid;
 
-    if( bEof || iDocid!=pCsr->iPrevId ) pIter = 0;
+    if( bMatch ){
+      pIter = pPhrase->pOrPoslist;
+    }else{
+      pIter = 0;
+    }
   }
   if( pIter==0 ) return SQLITE_OK;
 
@@ -138899,6 +140383,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_fts3_init(
 ******************************************************************************
 **
 */
+/* #include "fts3Int.h" */
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 /* #include <string.h> */
@@ -139455,6 +140940,7 @@ SQLITE_PRIVATE int sqlite3Fts3InitAux(sqlite3 *db){
 ** syntax is relatively simple, the whole tokenizer/parser system is
 ** hand-coded. 
 */
+/* #include "fts3Int.h" */
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 /*
@@ -140410,321 +141896,1372 @@ static int fts3ExprParseUnbalanced(
 }
 
 /*
-** Parameters z and n contain a pointer to and length of a buffer containing
-** an fts3 query expression, respectively. This function attempts to parse the
-** query expression and create a tree of Fts3Expr structures representing the
-** parsed expression. If successful, *ppExpr is set to point to the head
-** of the parsed expression tree and SQLITE_OK is returned. If an error
-** occurs, either SQLITE_NOMEM (out-of-memory error) or SQLITE_ERROR (parse
-** error) is returned and *ppExpr is set to 0.
+** Parameters z and n contain a pointer to and length of a buffer containing
+** an fts3 query expression, respectively. This function attempts to parse the
+** query expression and create a tree of Fts3Expr structures representing the
+** parsed expression. If successful, *ppExpr is set to point to the head
+** of the parsed expression tree and SQLITE_OK is returned. If an error
+** occurs, either SQLITE_NOMEM (out-of-memory error) or SQLITE_ERROR (parse
+** error) is returned and *ppExpr is set to 0.
+**
+** If parameter n is a negative number, then z is assumed to point to a
+** nul-terminated string and the length is determined using strlen().
+**
+** The first parameter, pTokenizer, is passed the fts3 tokenizer module to
+** use to normalize query tokens while parsing the expression. The azCol[]
+** array, which is assumed to contain nCol entries, should contain the names
+** of each column in the target fts3 table, in order from left to right. 
+** Column names must be nul-terminated strings.
+**
+** The iDefaultCol parameter should be passed the index of the table column
+** that appears on the left-hand-side of the MATCH operator (the default
+** column to match against for tokens for which a column name is not explicitly
+** specified as part of the query string), or -1 if tokens may by default
+** match any table column.
+*/
+SQLITE_PRIVATE int sqlite3Fts3ExprParse(
+  sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
+  int iLangid,                        /* Language id for tokenizer */
+  char **azCol,                       /* Array of column names for fts3 table */
+  int bFts4,                          /* True to allow FTS4-only syntax */
+  int nCol,                           /* Number of entries in azCol[] */
+  int iDefaultCol,                    /* Default column to query */
+  const char *z, int n,               /* Text of MATCH query */
+  Fts3Expr **ppExpr,                  /* OUT: Parsed query structure */
+  char **pzErr                        /* OUT: Error message (sqlite3_malloc) */
+){
+  int rc = fts3ExprParseUnbalanced(
+      pTokenizer, iLangid, azCol, bFts4, nCol, iDefaultCol, z, n, ppExpr
+  );
+  
+  /* Rebalance the expression. And check that its depth does not exceed
+  ** SQLITE_FTS3_MAX_EXPR_DEPTH.  */
+  if( rc==SQLITE_OK && *ppExpr ){
+    rc = fts3ExprBalance(ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
+    if( rc==SQLITE_OK ){
+      rc = fts3ExprCheckDepth(*ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3Fts3ExprFree(*ppExpr);
+    *ppExpr = 0;
+    if( rc==SQLITE_TOOBIG ){
+      sqlite3Fts3ErrMsg(pzErr,
+          "FTS expression tree is too large (maximum depth %d)", 
+          SQLITE_FTS3_MAX_EXPR_DEPTH
+      );
+      rc = SQLITE_ERROR;
+    }else if( rc==SQLITE_ERROR ){
+      sqlite3Fts3ErrMsg(pzErr, "malformed MATCH expression: [%s]", z);
+    }
+  }
+
+  return rc;
+}
+
+/*
+** Free a single node of an expression tree.
+*/
+static void fts3FreeExprNode(Fts3Expr *p){
+  assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
+  sqlite3Fts3EvalPhraseCleanup(p->pPhrase);
+  sqlite3_free(p->aMI);
+  sqlite3_free(p);
+}
+
+/*
+** Free a parsed fts3 query expression allocated by sqlite3Fts3ExprParse().
+**
+** This function would be simpler if it recursively called itself. But
+** that would mean passing a sufficiently large expression to ExprParse()
+** could cause a stack overflow.
+*/
+SQLITE_PRIVATE void sqlite3Fts3ExprFree(Fts3Expr *pDel){
+  Fts3Expr *p;
+  assert( pDel==0 || pDel->pParent==0 );
+  for(p=pDel; p && (p->pLeft||p->pRight); p=(p->pLeft ? p->pLeft : p->pRight)){
+    assert( p->pParent==0 || p==p->pParent->pRight || p==p->pParent->pLeft );
+  }
+  while( p ){
+    Fts3Expr *pParent = p->pParent;
+    fts3FreeExprNode(p);
+    if( pParent && p==pParent->pLeft && pParent->pRight ){
+      p = pParent->pRight;
+      while( p && (p->pLeft || p->pRight) ){
+        assert( p==p->pParent->pRight || p==p->pParent->pLeft );
+        p = (p->pLeft ? p->pLeft : p->pRight);
+      }
+    }else{
+      p = pParent;
+    }
+  }
+}
+
+/****************************************************************************
+*****************************************************************************
+** Everything after this point is just test code.
+*/
+
+#ifdef SQLITE_TEST
+
+/* #include <stdio.h> */
+
+/*
+** Function to query the hash-table of tokenizers (see README.tokenizers).
+*/
+static int queryTestTokenizer(
+  sqlite3 *db, 
+  const char *zName,  
+  const sqlite3_tokenizer_module **pp
+){
+  int rc;
+  sqlite3_stmt *pStmt;
+  const char zSql[] = "SELECT fts3_tokenizer(?)";
+
+  *pp = 0;
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
+      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
+    }
+  }
+
+  return sqlite3_finalize(pStmt);
+}
+
+/*
+** Return a pointer to a buffer containing a text representation of the
+** expression passed as the first argument. The buffer is obtained from
+** sqlite3_malloc(). It is the responsibility of the caller to use 
+** sqlite3_free() to release the memory. If an OOM condition is encountered,
+** NULL is returned.
+**
+** If the second argument is not NULL, then its contents are prepended to 
+** the returned expression text and then freed using sqlite3_free().
+*/
+static char *exprToString(Fts3Expr *pExpr, char *zBuf){
+  if( pExpr==0 ){
+    return sqlite3_mprintf("");
+  }
+  switch( pExpr->eType ){
+    case FTSQUERY_PHRASE: {
+      Fts3Phrase *pPhrase = pExpr->pPhrase;
+      int i;
+      zBuf = sqlite3_mprintf(
+          "%zPHRASE %d 0", zBuf, pPhrase->iColumn);
+      for(i=0; zBuf && i<pPhrase->nToken; i++){
+        zBuf = sqlite3_mprintf("%z %.*s%s", zBuf, 
+            pPhrase->aToken[i].n, pPhrase->aToken[i].z,
+            (pPhrase->aToken[i].isPrefix?"+":"")
+        );
+      }
+      return zBuf;
+    }
+
+    case FTSQUERY_NEAR:
+      zBuf = sqlite3_mprintf("%zNEAR/%d ", zBuf, pExpr->nNear);
+      break;
+    case FTSQUERY_NOT:
+      zBuf = sqlite3_mprintf("%zNOT ", zBuf);
+      break;
+    case FTSQUERY_AND:
+      zBuf = sqlite3_mprintf("%zAND ", zBuf);
+      break;
+    case FTSQUERY_OR:
+      zBuf = sqlite3_mprintf("%zOR ", zBuf);
+      break;
+  }
+
+  if( zBuf ) zBuf = sqlite3_mprintf("%z{", zBuf);
+  if( zBuf ) zBuf = exprToString(pExpr->pLeft, zBuf);
+  if( zBuf ) zBuf = sqlite3_mprintf("%z} {", zBuf);
+
+  if( zBuf ) zBuf = exprToString(pExpr->pRight, zBuf);
+  if( zBuf ) zBuf = sqlite3_mprintf("%z}", zBuf);
+
+  return zBuf;
+}
+
+/*
+** This is the implementation of a scalar SQL function used to test the 
+** expression parser. It should be called as follows:
+**
+**   fts3_exprtest(<tokenizer>, <expr>, <column 1>, ...);
+**
+** The first argument, <tokenizer>, is the name of the fts3 tokenizer used
+** to parse the query expression (see README.tokenizers). The second argument
+** is the query expression to parse. Each subsequent argument is the name
+** of a column of the fts3 table that the query expression may refer to.
+** For example:
+**
+**   SELECT fts3_exprtest('simple', 'Bill col2:Bloggs', 'col1', 'col2');
+*/
+static void fts3ExprTest(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  sqlite3_tokenizer_module const *pModule = 0;
+  sqlite3_tokenizer *pTokenizer = 0;
+  int rc;
+  char **azCol = 0;
+  const char *zExpr;
+  int nExpr;
+  int nCol;
+  int ii;
+  Fts3Expr *pExpr;
+  char *zBuf = 0;
+  sqlite3 *db = sqlite3_context_db_handle(context);
+
+  if( argc<3 ){
+    sqlite3_result_error(context, 
+        "Usage: fts3_exprtest(tokenizer, expr, col1, ...", -1
+    );
+    return;
+  }
+
+  rc = queryTestTokenizer(db,
+                          (const char *)sqlite3_value_text(argv[0]), &pModule);
+  if( rc==SQLITE_NOMEM ){
+    sqlite3_result_error_nomem(context);
+    goto exprtest_out;
+  }else if( !pModule ){
+    sqlite3_result_error(context, "No such tokenizer module", -1);
+    goto exprtest_out;
+  }
+
+  rc = pModule->xCreate(0, 0, &pTokenizer);
+  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
+  if( rc==SQLITE_NOMEM ){
+    sqlite3_result_error_nomem(context);
+    goto exprtest_out;
+  }
+  pTokenizer->pModule = pModule;
+
+  zExpr = (const char *)sqlite3_value_text(argv[1]);
+  nExpr = sqlite3_value_bytes(argv[1]);
+  nCol = argc-2;
+  azCol = (char **)sqlite3_malloc(nCol*sizeof(char *));
+  if( !azCol ){
+    sqlite3_result_error_nomem(context);
+    goto exprtest_out;
+  }
+  for(ii=0; ii<nCol; ii++){
+    azCol[ii] = (char *)sqlite3_value_text(argv[ii+2]);
+  }
+
+  if( sqlite3_user_data(context) ){
+    char *zDummy = 0;
+    rc = sqlite3Fts3ExprParse(
+        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr, &zDummy
+    );
+    assert( rc==SQLITE_OK || pExpr==0 );
+    sqlite3_free(zDummy);
+  }else{
+    rc = fts3ExprParseUnbalanced(
+        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr
+    );
+  }
+
+  if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
+    sqlite3Fts3ExprFree(pExpr);
+    sqlite3_result_error(context, "Error parsing expression", -1);
+  }else if( rc==SQLITE_NOMEM || !(zBuf = exprToString(pExpr, 0)) ){
+    sqlite3_result_error_nomem(context);
+  }else{
+    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+    sqlite3_free(zBuf);
+  }
+
+  sqlite3Fts3ExprFree(pExpr);
+
+exprtest_out:
+  if( pModule && pTokenizer ){
+    rc = pModule->xDestroy(pTokenizer);
+  }
+  sqlite3_free(azCol);
+}
+
+/*
+** Register the query expression parser test function fts3_exprtest() 
+** with database connection db. 
+*/
+SQLITE_PRIVATE int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
+  int rc = sqlite3_create_function(
+      db, "fts3_exprtest", -1, SQLITE_UTF8, 0, fts3ExprTest, 0, 0
+  );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "fts3_exprtest_rebalance", 
+        -1, SQLITE_UTF8, (void *)1, fts3ExprTest, 0, 0
+    );
+  }
+  return rc;
+}
+
+#endif
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_expr.c *******************************************/
+/************** Begin file fts3_hash.c ***************************************/
+/*
+** 2001 September 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This is the implementation of generic hash-tables used in SQLite.
+** We've modified it slightly to serve as a standalone hash table
+** implementation for the full-text indexing module.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <string.h> */
+
+/* #include "fts3_hash.h" */
+
+/*
+** Malloc and Free functions
+*/
+static void *fts3HashMalloc(int n){
+  void *p = sqlite3_malloc(n);
+  if( p ){
+    memset(p, 0, n);
+  }
+  return p;
+}
+static void fts3HashFree(void *p){
+  sqlite3_free(p);
+}
+
+/* Turn bulk memory into a hash table object by initializing the
+** fields of the Hash structure.
+**
+** "pNew" is a pointer to the hash table that is to be initialized.
+** keyClass is one of the constants 
+** FTS3_HASH_BINARY or FTS3_HASH_STRING.  The value of keyClass 
+** determines what kind of key the hash table will use.  "copyKey" is
+** true if the hash table should make its own private copy of keys and
+** false if it should just use the supplied pointer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey){
+  assert( pNew!=0 );
+  assert( keyClass>=FTS3_HASH_STRING && keyClass<=FTS3_HASH_BINARY );
+  pNew->keyClass = keyClass;
+  pNew->copyKey = copyKey;
+  pNew->first = 0;
+  pNew->count = 0;
+  pNew->htsize = 0;
+  pNew->ht = 0;
+}
+
+/* Remove all entries from a hash table.  Reclaim all memory.
+** Call this routine to delete a hash table or to reset a hash table
+** to the empty state.
+*/
+SQLITE_PRIVATE void sqlite3Fts3HashClear(Fts3Hash *pH){
+  Fts3HashElem *elem;         /* For looping over all elements of the table */
+
+  assert( pH!=0 );
+  elem = pH->first;
+  pH->first = 0;
+  fts3HashFree(pH->ht);
+  pH->ht = 0;
+  pH->htsize = 0;
+  while( elem ){
+    Fts3HashElem *next_elem = elem->next;
+    if( pH->copyKey && elem->pKey ){
+      fts3HashFree(elem->pKey);
+    }
+    fts3HashFree(elem);
+    elem = next_elem;
+  }
+  pH->count = 0;
+}
+
+/*
+** Hash and comparison functions when the mode is FTS3_HASH_STRING
+*/
+static int fts3StrHash(const void *pKey, int nKey){
+  const char *z = (const char *)pKey;
+  unsigned h = 0;
+  if( nKey<=0 ) nKey = (int) strlen(z);
+  while( nKey > 0  ){
+    h = (h<<3) ^ h ^ *z++;
+    nKey--;
+  }
+  return (int)(h & 0x7fffffff);
+}
+static int fts3StrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
+  if( n1!=n2 ) return 1;
+  return strncmp((const char*)pKey1,(const char*)pKey2,n1);
+}
+
+/*
+** Hash and comparison functions when the mode is FTS3_HASH_BINARY
+*/
+static int fts3BinHash(const void *pKey, int nKey){
+  int h = 0;
+  const char *z = (const char *)pKey;
+  while( nKey-- > 0 ){
+    h = (h<<3) ^ h ^ *(z++);
+  }
+  return h & 0x7fffffff;
+}
+static int fts3BinCompare(const void *pKey1, int n1, const void *pKey2, int n2){
+  if( n1!=n2 ) return 1;
+  return memcmp(pKey1,pKey2,n1);
+}
+
+/*
+** Return a pointer to the appropriate hash function given the key class.
+**
+** The C syntax in this function definition may be unfamilar to some 
+** programmers, so we provide the following additional explanation:
+**
+** The name of the function is "ftsHashFunction".  The function takes a
+** single parameter "keyClass".  The return value of ftsHashFunction()
+** is a pointer to another function.  Specifically, the return value
+** of ftsHashFunction() is a pointer to a function that takes two parameters
+** with types "const void*" and "int" and returns an "int".
+*/
+static int (*ftsHashFunction(int keyClass))(const void*,int){
+  if( keyClass==FTS3_HASH_STRING ){
+    return &fts3StrHash;
+  }else{
+    assert( keyClass==FTS3_HASH_BINARY );
+    return &fts3BinHash;
+  }
+}
+
+/*
+** Return a pointer to the appropriate hash function given the key class.
+**
+** For help in interpreted the obscure C code in the function definition,
+** see the header comment on the previous function.
+*/
+static int (*ftsCompareFunction(int keyClass))(const void*,int,const void*,int){
+  if( keyClass==FTS3_HASH_STRING ){
+    return &fts3StrCompare;
+  }else{
+    assert( keyClass==FTS3_HASH_BINARY );
+    return &fts3BinCompare;
+  }
+}
+
+/* Link an element into the hash table
+*/
+static void fts3HashInsertElement(
+  Fts3Hash *pH,            /* The complete hash table */
+  struct _fts3ht *pEntry,  /* The entry into which pNew is inserted */
+  Fts3HashElem *pNew       /* The element to be inserted */
+){
+  Fts3HashElem *pHead;     /* First element already in pEntry */
+  pHead = pEntry->chain;
+  if( pHead ){
+    pNew->next = pHead;
+    pNew->prev = pHead->prev;
+    if( pHead->prev ){ pHead->prev->next = pNew; }
+    else             { pH->first = pNew; }
+    pHead->prev = pNew;
+  }else{
+    pNew->next = pH->first;
+    if( pH->first ){ pH->first->prev = pNew; }
+    pNew->prev = 0;
+    pH->first = pNew;
+  }
+  pEntry->count++;
+  pEntry->chain = pNew;
+}
+
+
+/* Resize the hash table so that it cantains "new_size" buckets.
+** "new_size" must be a power of 2.  The hash table might fail 
+** to resize if sqliteMalloc() fails.
+**
+** Return non-zero if a memory allocation error occurs.
+*/
+static int fts3Rehash(Fts3Hash *pH, int new_size){
+  struct _fts3ht *new_ht;          /* The new hash table */
+  Fts3HashElem *elem, *next_elem;  /* For looping over existing elements */
+  int (*xHash)(const void*,int);   /* The hash function */
+
+  assert( (new_size & (new_size-1))==0 );
+  new_ht = (struct _fts3ht *)fts3HashMalloc( new_size*sizeof(struct _fts3ht) );
+  if( new_ht==0 ) return 1;
+  fts3HashFree(pH->ht);
+  pH->ht = new_ht;
+  pH->htsize = new_size;
+  xHash = ftsHashFunction(pH->keyClass);
+  for(elem=pH->first, pH->first=0; elem; elem = next_elem){
+    int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
+    next_elem = elem->next;
+    fts3HashInsertElement(pH, &new_ht[h], elem);
+  }
+  return 0;
+}
+
+/* This function (for internal use only) locates an element in an
+** hash table that matches the given key.  The hash for this key has
+** already been computed and is passed as the 4th parameter.
+*/
+static Fts3HashElem *fts3FindElementByHash(
+  const Fts3Hash *pH, /* The pH to be searched */
+  const void *pKey,   /* The key we are searching for */
+  int nKey,
+  int h               /* The hash for this key. */
+){
+  Fts3HashElem *elem;            /* Used to loop thru the element list */
+  int count;                     /* Number of elements left to test */
+  int (*xCompare)(const void*,int,const void*,int);  /* comparison function */
+
+  if( pH->ht ){
+    struct _fts3ht *pEntry = &pH->ht[h];
+    elem = pEntry->chain;
+    count = pEntry->count;
+    xCompare = ftsCompareFunction(pH->keyClass);
+    while( count-- && elem ){
+      if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){ 
+        return elem;
+      }
+      elem = elem->next;
+    }
+  }
+  return 0;
+}
+
+/* Remove a single entry from the hash table given a pointer to that
+** element and a hash on the element's key.
+*/
+static void fts3RemoveElementByHash(
+  Fts3Hash *pH,         /* The pH containing "elem" */
+  Fts3HashElem* elem,   /* The element to be removed from the pH */
+  int h                 /* Hash value for the element */
+){
+  struct _fts3ht *pEntry;
+  if( elem->prev ){
+    elem->prev->next = elem->next; 
+  }else{
+    pH->first = elem->next;
+  }
+  if( elem->next ){
+    elem->next->prev = elem->prev;
+  }
+  pEntry = &pH->ht[h];
+  if( pEntry->chain==elem ){
+    pEntry->chain = elem->next;
+  }
+  pEntry->count--;
+  if( pEntry->count<=0 ){
+    pEntry->chain = 0;
+  }
+  if( pH->copyKey && elem->pKey ){
+    fts3HashFree(elem->pKey);
+  }
+  fts3HashFree( elem );
+  pH->count--;
+  if( pH->count<=0 ){
+    assert( pH->first==0 );
+    assert( pH->count==0 );
+    fts3HashClear(pH);
+  }
+}
+
+SQLITE_PRIVATE Fts3HashElem *sqlite3Fts3HashFindElem(
+  const Fts3Hash *pH, 
+  const void *pKey, 
+  int nKey
+){
+  int h;                          /* A hash on key */
+  int (*xHash)(const void*,int);  /* The hash function */
+
+  if( pH==0 || pH->ht==0 ) return 0;
+  xHash = ftsHashFunction(pH->keyClass);
+  assert( xHash!=0 );
+  h = (*xHash)(pKey,nKey);
+  assert( (pH->htsize & (pH->htsize-1))==0 );
+  return fts3FindElementByHash(pH,pKey,nKey, h & (pH->htsize-1));
+}
+
+/* 
+** Attempt to locate an element of the hash table pH with a key
+** that matches pKey,nKey.  Return the data for this element if it is
+** found, or NULL if there is no match.
+*/
+SQLITE_PRIVATE void *sqlite3Fts3HashFind(const Fts3Hash *pH, const void *pKey, int nKey){
+  Fts3HashElem *pElem;            /* The element that matches key (if any) */
+
+  pElem = sqlite3Fts3HashFindElem(pH, pKey, nKey);
+  return pElem ? pElem->data : 0;
+}
+
+/* Insert an element into the hash table pH.  The key is pKey,nKey
+** and the data is "data".
+**
+** If no element exists with a matching key, then a new
+** element is created.  A copy of the key is made if the copyKey
+** flag is set.  NULL is returned.
+**
+** If another element already exists with the same key, then the
+** new data replaces the old data and the old data is returned.
+** The key is not copied in this instance.  If a malloc fails, then
+** the new data is returned and the hash table is unchanged.
+**
+** If the "data" parameter to this function is NULL, then the
+** element corresponding to "key" is removed from the hash table.
+*/
+SQLITE_PRIVATE void *sqlite3Fts3HashInsert(
+  Fts3Hash *pH,        /* The hash table to insert into */
+  const void *pKey,    /* The key */
+  int nKey,            /* Number of bytes in the key */
+  void *data           /* The data */
+){
+  int hraw;                 /* Raw hash value of the key */
+  int h;                    /* the hash of the key modulo hash table size */
+  Fts3HashElem *elem;       /* Used to loop thru the element list */
+  Fts3HashElem *new_elem;   /* New element added to the pH */
+  int (*xHash)(const void*,int);  /* The hash function */
+
+  assert( pH!=0 );
+  xHash = ftsHashFunction(pH->keyClass);
+  assert( xHash!=0 );
+  hraw = (*xHash)(pKey, nKey);
+  assert( (pH->htsize & (pH->htsize-1))==0 );
+  h = hraw & (pH->htsize-1);
+  elem = fts3FindElementByHash(pH,pKey,nKey,h);
+  if( elem ){
+    void *old_data = elem->data;
+    if( data==0 ){
+      fts3RemoveElementByHash(pH,elem,h);
+    }else{
+      elem->data = data;
+    }
+    return old_data;
+  }
+  if( data==0 ) return 0;
+  if( (pH->htsize==0 && fts3Rehash(pH,8))
+   || (pH->count>=pH->htsize && fts3Rehash(pH, pH->htsize*2))
+  ){
+    pH->count = 0;
+    return data;
+  }
+  assert( pH->htsize>0 );
+  new_elem = (Fts3HashElem*)fts3HashMalloc( sizeof(Fts3HashElem) );
+  if( new_elem==0 ) return data;
+  if( pH->copyKey && pKey!=0 ){
+    new_elem->pKey = fts3HashMalloc( nKey );
+    if( new_elem->pKey==0 ){
+      fts3HashFree(new_elem);
+      return data;
+    }
+    memcpy((void*)new_elem->pKey, pKey, nKey);
+  }else{
+    new_elem->pKey = (void*)pKey;
+  }
+  new_elem->nKey = nKey;
+  pH->count++;
+  assert( pH->htsize>0 );
+  assert( (pH->htsize & (pH->htsize-1))==0 );
+  h = hraw & (pH->htsize-1);
+  fts3HashInsertElement(pH, &pH->ht[h], new_elem);
+  new_elem->data = data;
+  return 0;
+}
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_hash.c *******************************************/
+/************** Begin file fts3_porter.c *************************************/
+/*
+** 2006 September 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Implementation of the full-text-search tokenizer that implements
+** a Porter stemmer.
+*/
+
+/*
+** The code in this file is only compiled if:
+**
+**     * The FTS3 module is being built as an extension
+**       (in which case SQLITE_CORE is not defined), or
+**
+**     * The FTS3 module is being built into the core of
+**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+*/
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <stdio.h> */
+/* #include <string.h> */
+
+/* #include "fts3_tokenizer.h" */
+
+/*
+** Class derived from sqlite3_tokenizer
+*/
+typedef struct porter_tokenizer {
+  sqlite3_tokenizer base;      /* Base class */
+} porter_tokenizer;
+
+/*
+** Class derived from sqlite3_tokenizer_cursor
+*/
+typedef struct porter_tokenizer_cursor {
+  sqlite3_tokenizer_cursor base;
+  const char *zInput;          /* input we are tokenizing */
+  int nInput;                  /* size of the input */
+  int iOffset;                 /* current position in zInput */
+  int iToken;                  /* index of next token to be returned */
+  char *zToken;                /* storage for current token */
+  int nAllocated;              /* space allocated to zToken buffer */
+} porter_tokenizer_cursor;
+
+
+/*
+** Create a new tokenizer instance.
+*/
+static int porterCreate(
+  int argc, const char * const *argv,
+  sqlite3_tokenizer **ppTokenizer
+){
+  porter_tokenizer *t;
+
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
+
+  t = (porter_tokenizer *) sqlite3_malloc(sizeof(*t));
+  if( t==NULL ) return SQLITE_NOMEM;
+  memset(t, 0, sizeof(*t));
+  *ppTokenizer = &t->base;
+  return SQLITE_OK;
+}
+
+/*
+** Destroy a tokenizer
+*/
+static int porterDestroy(sqlite3_tokenizer *pTokenizer){
+  sqlite3_free(pTokenizer);
+  return SQLITE_OK;
+}
+
+/*
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is zInput[0..nInput-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
+*/
+static int porterOpen(
+  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
+  const char *zInput, int nInput,        /* String to be tokenized */
+  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
+){
+  porter_tokenizer_cursor *c;
+
+  UNUSED_PARAMETER(pTokenizer);
+
+  c = (porter_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
+  if( c==NULL ) return SQLITE_NOMEM;
+
+  c->zInput = zInput;
+  if( zInput==0 ){
+    c->nInput = 0;
+  }else if( nInput<0 ){
+    c->nInput = (int)strlen(zInput);
+  }else{
+    c->nInput = nInput;
+  }
+  c->iOffset = 0;                 /* start tokenizing at the beginning */
+  c->iToken = 0;
+  c->zToken = NULL;               /* no space allocated, yet. */
+  c->nAllocated = 0;
+
+  *ppCursor = &c->base;
+  return SQLITE_OK;
+}
+
+/*
+** Close a tokenization cursor previously opened by a call to
+** porterOpen() above.
+*/
+static int porterClose(sqlite3_tokenizer_cursor *pCursor){
+  porter_tokenizer_cursor *c = (porter_tokenizer_cursor *) pCursor;
+  sqlite3_free(c->zToken);
+  sqlite3_free(c);
+  return SQLITE_OK;
+}
+/*
+** Vowel or consonant
+*/
+static const char cType[] = {
+   0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0,
+   1, 1, 1, 2, 1
+};
+
+/*
+** isConsonant() and isVowel() determine if their first character in
+** the string they point to is a consonant or a vowel, according
+** to Porter ruls.  
+**
+** A consonate is any letter other than 'a', 'e', 'i', 'o', or 'u'.
+** 'Y' is a consonant unless it follows another consonant,
+** in which case it is a vowel.
+**
+** In these routine, the letters are in reverse order.  So the 'y' rule
+** is that 'y' is a consonant unless it is followed by another
+** consonent.
+*/
+static int isVowel(const char*);
+static int isConsonant(const char *z){
+  int j;
+  char x = *z;
+  if( x==0 ) return 0;
+  assert( x>='a' && x<='z' );
+  j = cType[x-'a'];
+  if( j<2 ) return j;
+  return z[1]==0 || isVowel(z + 1);
+}
+static int isVowel(const char *z){
+  int j;
+  char x = *z;
+  if( x==0 ) return 0;
+  assert( x>='a' && x<='z' );
+  j = cType[x-'a'];
+  if( j<2 ) return 1-j;
+  return isConsonant(z + 1);
+}
+
+/*
+** Let any sequence of one or more vowels be represented by V and let
+** C be sequence of one or more consonants.  Then every word can be
+** represented as:
 **
-** If parameter n is a negative number, then z is assumed to point to a
-** nul-terminated string and the length is determined using strlen().
+**           [C] (VC){m} [V]
 **
-** The first parameter, pTokenizer, is passed the fts3 tokenizer module to
-** use to normalize query tokens while parsing the expression. The azCol[]
-** array, which is assumed to contain nCol entries, should contain the names
-** of each column in the target fts3 table, in order from left to right. 
-** Column names must be nul-terminated strings.
+** In prose:  A word is an optional consonant followed by zero or
+** vowel-consonant pairs followed by an optional vowel.  "m" is the
+** number of vowel consonant pairs.  This routine computes the value
+** of m for the first i bytes of a word.
 **
-** The iDefaultCol parameter should be passed the index of the table column
-** that appears on the left-hand-side of the MATCH operator (the default
-** column to match against for tokens for which a column name is not explicitly
-** specified as part of the query string), or -1 if tokens may by default
-** match any table column.
+** Return true if the m-value for z is 1 or more.  In other words,
+** return true if z contains at least one vowel that is followed
+** by a consonant.
+**
+** In this routine z[] is in reverse order.  So we are really looking
+** for an instance of a consonant followed by a vowel.
 */
-SQLITE_PRIVATE int sqlite3Fts3ExprParse(
-  sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
-  int iLangid,                        /* Language id for tokenizer */
-  char **azCol,                       /* Array of column names for fts3 table */
-  int bFts4,                          /* True to allow FTS4-only syntax */
-  int nCol,                           /* Number of entries in azCol[] */
-  int iDefaultCol,                    /* Default column to query */
-  const char *z, int n,               /* Text of MATCH query */
-  Fts3Expr **ppExpr,                  /* OUT: Parsed query structure */
-  char **pzErr                        /* OUT: Error message (sqlite3_malloc) */
-){
-  int rc = fts3ExprParseUnbalanced(
-      pTokenizer, iLangid, azCol, bFts4, nCol, iDefaultCol, z, n, ppExpr
-  );
-  
-  /* Rebalance the expression. And check that its depth does not exceed
-  ** SQLITE_FTS3_MAX_EXPR_DEPTH.  */
-  if( rc==SQLITE_OK && *ppExpr ){
-    rc = fts3ExprBalance(ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
-    if( rc==SQLITE_OK ){
-      rc = fts3ExprCheckDepth(*ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
-    }
-  }
+static int m_gt_0(const char *z){
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  return *z!=0;
+}
 
-  if( rc!=SQLITE_OK ){
-    sqlite3Fts3ExprFree(*ppExpr);
-    *ppExpr = 0;
-    if( rc==SQLITE_TOOBIG ){
-      sqlite3Fts3ErrMsg(pzErr,
-          "FTS expression tree is too large (maximum depth %d)", 
-          SQLITE_FTS3_MAX_EXPR_DEPTH
-      );
-      rc = SQLITE_ERROR;
-    }else if( rc==SQLITE_ERROR ){
-      sqlite3Fts3ErrMsg(pzErr, "malformed MATCH expression: [%s]", z);
-    }
-  }
+/* Like mgt0 above except we are looking for a value of m which is
+** exactly 1
+*/
+static int m_eq_1(const char *z){
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 1;
+  while( isConsonant(z) ){ z++; }
+  return *z==0;
+}
 
-  return rc;
+/* Like mgt0 above except we are looking for a value of m>1 instead
+** or m>0
+*/
+static int m_gt_1(const char *z){
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isVowel(z) ){ z++; }
+  if( *z==0 ) return 0;
+  while( isConsonant(z) ){ z++; }
+  return *z!=0;
 }
 
 /*
-** Free a single node of an expression tree.
+** Return TRUE if there is a vowel anywhere within z[0..n-1]
 */
-static void fts3FreeExprNode(Fts3Expr *p){
-  assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
-  sqlite3Fts3EvalPhraseCleanup(p->pPhrase);
-  sqlite3_free(p->aMI);
-  sqlite3_free(p);
+static int hasVowel(const char *z){
+  while( isConsonant(z) ){ z++; }
+  return *z!=0;
 }
 
 /*
-** Free a parsed fts3 query expression allocated by sqlite3Fts3ExprParse().
+** Return TRUE if the word ends in a double consonant.
 **
-** This function would be simpler if it recursively called itself. But
-** that would mean passing a sufficiently large expression to ExprParse()
-** could cause a stack overflow.
+** The text is reversed here. So we are really looking at
+** the first two characters of z[].
 */
-SQLITE_PRIVATE void sqlite3Fts3ExprFree(Fts3Expr *pDel){
-  Fts3Expr *p;
-  assert( pDel==0 || pDel->pParent==0 );
-  for(p=pDel; p && (p->pLeft||p->pRight); p=(p->pLeft ? p->pLeft : p->pRight)){
-    assert( p->pParent==0 || p==p->pParent->pRight || p==p->pParent->pLeft );
-  }
-  while( p ){
-    Fts3Expr *pParent = p->pParent;
-    fts3FreeExprNode(p);
-    if( pParent && p==pParent->pLeft && pParent->pRight ){
-      p = pParent->pRight;
-      while( p && (p->pLeft || p->pRight) ){
-        assert( p==p->pParent->pRight || p==p->pParent->pLeft );
-        p = (p->pLeft ? p->pLeft : p->pRight);
-      }
-    }else{
-      p = pParent;
-    }
-  }
+static int doubleConsonant(const char *z){
+  return isConsonant(z) && z[0]==z[1];
 }
 
-/****************************************************************************
-*****************************************************************************
-** Everything after this point is just test code.
+/*
+** Return TRUE if the word ends with three letters which
+** are consonant-vowel-consonent and where the final consonant
+** is not 'w', 'x', or 'y'.
+**
+** The word is reversed here.  So we are really checking the
+** first three letters and the first one cannot be in [wxy].
 */
-
-#ifdef SQLITE_TEST
-
-/* #include <stdio.h> */
+static int star_oh(const char *z){
+  return
+    isConsonant(z) &&
+    z[0]!='w' && z[0]!='x' && z[0]!='y' &&
+    isVowel(z+1) &&
+    isConsonant(z+2);
+}
 
 /*
-** Function to query the hash-table of tokenizers (see README.tokenizers).
+** If the word ends with zFrom and xCond() is true for the stem
+** of the word that preceeds the zFrom ending, then change the 
+** ending to zTo.
+**
+** The input word *pz and zFrom are both in reverse order.  zTo
+** is in normal order. 
+**
+** Return TRUE if zFrom matches.  Return FALSE if zFrom does not
+** match.  Not that TRUE is returned even if xCond() fails and
+** no substitution occurs.
 */
-static int queryTestTokenizer(
-  sqlite3 *db, 
-  const char *zName,  
-  const sqlite3_tokenizer_module **pp
+static int stem(
+  char **pz,             /* The word being stemmed (Reversed) */
+  const char *zFrom,     /* If the ending matches this... (Reversed) */
+  const char *zTo,       /* ... change the ending to this (not reversed) */
+  int (*xCond)(const char*)   /* Condition that must be true */
 ){
-  int rc;
-  sqlite3_stmt *pStmt;
-  const char zSql[] = "SELECT fts3_tokenizer(?)";
-
-  *pp = 0;
-  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
-  if( SQLITE_ROW==sqlite3_step(pStmt) ){
-    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
-      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
-    }
+  char *z = *pz;
+  while( *zFrom && *zFrom==*z ){ z++; zFrom++; }
+  if( *zFrom!=0 ) return 0;
+  if( xCond && !xCond(z) ) return 1;
+  while( *zTo ){
+    *(--z) = *(zTo++);
   }
-
-  return sqlite3_finalize(pStmt);
+  *pz = z;
+  return 1;
 }
 
 /*
-** Return a pointer to a buffer containing a text representation of the
-** expression passed as the first argument. The buffer is obtained from
-** sqlite3_malloc(). It is the responsibility of the caller to use 
-** sqlite3_free() to release the memory. If an OOM condition is encountered,
-** NULL is returned.
-**
-** If the second argument is not NULL, then its contents are prepended to 
-** the returned expression text and then freed using sqlite3_free().
+** This is the fallback stemmer used when the porter stemmer is
+** inappropriate.  The input word is copied into the output with
+** US-ASCII case folding.  If the input word is too long (more
+** than 20 bytes if it contains no digits or more than 6 bytes if
+** it contains digits) then word is truncated to 20 or 6 bytes
+** by taking 10 or 3 bytes from the beginning and end.
 */
-static char *exprToString(Fts3Expr *pExpr, char *zBuf){
-  if( pExpr==0 ){
-    return sqlite3_mprintf("");
+static void copy_stemmer(const char *zIn, int nIn, char *zOut, int *pnOut){
+  int i, mx, j;
+  int hasDigit = 0;
+  for(i=0; i<nIn; i++){
+    char c = zIn[i];
+    if( c>='A' && c<='Z' ){
+      zOut[i] = c - 'A' + 'a';
+    }else{
+      if( c>='0' && c<='9' ) hasDigit = 1;
+      zOut[i] = c;
+    }
   }
-  switch( pExpr->eType ){
-    case FTSQUERY_PHRASE: {
-      Fts3Phrase *pPhrase = pExpr->pPhrase;
-      int i;
-      zBuf = sqlite3_mprintf(
-          "%zPHRASE %d 0", zBuf, pPhrase->iColumn);
-      for(i=0; zBuf && i<pPhrase->nToken; i++){
-        zBuf = sqlite3_mprintf("%z %.*s%s", zBuf, 
-            pPhrase->aToken[i].n, pPhrase->aToken[i].z,
-            (pPhrase->aToken[i].isPrefix?"+":"")
-        );
-      }
-      return zBuf;
+  mx = hasDigit ? 3 : 10;
+  if( nIn>mx*2 ){
+    for(j=mx, i=nIn-mx; i<nIn; i++, j++){
+      zOut[j] = zOut[i];
     }
-
-    case FTSQUERY_NEAR:
-      zBuf = sqlite3_mprintf("%zNEAR/%d ", zBuf, pExpr->nNear);
-      break;
-    case FTSQUERY_NOT:
-      zBuf = sqlite3_mprintf("%zNOT ", zBuf);
-      break;
-    case FTSQUERY_AND:
-      zBuf = sqlite3_mprintf("%zAND ", zBuf);
-      break;
-    case FTSQUERY_OR:
-      zBuf = sqlite3_mprintf("%zOR ", zBuf);
-      break;
+    i = j;
   }
-
-  if( zBuf ) zBuf = sqlite3_mprintf("%z{", zBuf);
-  if( zBuf ) zBuf = exprToString(pExpr->pLeft, zBuf);
-  if( zBuf ) zBuf = sqlite3_mprintf("%z} {", zBuf);
-
-  if( zBuf ) zBuf = exprToString(pExpr->pRight, zBuf);
-  if( zBuf ) zBuf = sqlite3_mprintf("%z}", zBuf);
-
-  return zBuf;
+  zOut[i] = 0;
+  *pnOut = i;
 }
 
+
 /*
-** This is the implementation of a scalar SQL function used to test the 
-** expression parser. It should be called as follows:
+** Stem the input word zIn[0..nIn-1].  Store the output in zOut.
+** zOut is at least big enough to hold nIn bytes.  Write the actual
+** size of the output word (exclusive of the '\0' terminator) into *pnOut.
 **
-**   fts3_exprtest(<tokenizer>, <expr>, <column 1>, ...);
+** Any upper-case characters in the US-ASCII character set ([A-Z])
+** are converted to lower case.  Upper-case UTF characters are
+** unchanged.
 **
-** The first argument, <tokenizer>, is the name of the fts3 tokenizer used
-** to parse the query expression (see README.tokenizers). The second argument
-** is the query expression to parse. Each subsequent argument is the name
-** of a column of the fts3 table that the query expression may refer to.
-** For example:
+** Words that are longer than about 20 bytes are stemmed by retaining
+** a few bytes from the beginning and the end of the word.  If the
+** word contains digits, 3 bytes are taken from the beginning and
+** 3 bytes from the end.  For long words without digits, 10 bytes
+** are taken from each end.  US-ASCII case folding still applies.
+** 
+** If the input word contains not digits but does characters not 
+** in [a-zA-Z] then no stemming is attempted and this routine just 
+** copies the input into the input into the output with US-ASCII
+** case folding.
 **
-**   SELECT fts3_exprtest('simple', 'Bill col2:Bloggs', 'col1', 'col2');
+** Stemming never increases the length of the word.  So there is
+** no chance of overflowing the zOut buffer.
 */
-static void fts3ExprTest(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
-){
-  sqlite3_tokenizer_module const *pModule = 0;
-  sqlite3_tokenizer *pTokenizer = 0;
-  int rc;
-  char **azCol = 0;
-  const char *zExpr;
-  int nExpr;
-  int nCol;
-  int ii;
-  Fts3Expr *pExpr;
-  char *zBuf = 0;
-  sqlite3 *db = sqlite3_context_db_handle(context);
-
-  if( argc<3 ){
-    sqlite3_result_error(context, 
-        "Usage: fts3_exprtest(tokenizer, expr, col1, ...", -1
-    );
+static void porter_stemmer(const char *zIn, int nIn, char *zOut, int *pnOut){
+  int i, j;
+  char zReverse[28];
+  char *z, *z2;
+  if( nIn<3 || nIn>=(int)sizeof(zReverse)-7 ){
+    /* The word is too big or too small for the porter stemmer.
+    ** Fallback to the copy stemmer */
+    copy_stemmer(zIn, nIn, zOut, pnOut);
     return;
   }
+  for(i=0, j=sizeof(zReverse)-6; i<nIn; i++, j--){
+    char c = zIn[i];
+    if( c>='A' && c<='Z' ){
+      zReverse[j] = c + 'a' - 'A';
+    }else if( c>='a' && c<='z' ){
+      zReverse[j] = c;
+    }else{
+      /* The use of a character not in [a-zA-Z] means that we fallback
+      ** to the copy stemmer */
+      copy_stemmer(zIn, nIn, zOut, pnOut);
+      return;
+    }
+  }
+  memset(&zReverse[sizeof(zReverse)-5], 0, 5);
+  z = &zReverse[j+1];
 
-  rc = queryTestTokenizer(db,
-                          (const char *)sqlite3_value_text(argv[0]), &pModule);
-  if( rc==SQLITE_NOMEM ){
-    sqlite3_result_error_nomem(context);
-    goto exprtest_out;
-  }else if( !pModule ){
-    sqlite3_result_error(context, "No such tokenizer module", -1);
-    goto exprtest_out;
+
+  /* Step 1a */
+  if( z[0]=='s' ){
+    if(
+     !stem(&z, "sess", "ss", 0) &&
+     !stem(&z, "sei", "i", 0)  &&
+     !stem(&z, "ss", "ss", 0)
+    ){
+      z++;
+    }
   }
 
-  rc = pModule->xCreate(0, 0, &pTokenizer);
-  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
-  if( rc==SQLITE_NOMEM ){
-    sqlite3_result_error_nomem(context);
-    goto exprtest_out;
+  /* Step 1b */  
+  z2 = z;
+  if( stem(&z, "dee", "ee", m_gt_0) ){
+    /* Do nothing.  The work was all in the test */
+  }else if( 
+     (stem(&z, "gni", "", hasVowel) || stem(&z, "de", "", hasVowel))
+      && z!=z2
+  ){
+     if( stem(&z, "ta", "ate", 0) ||
+         stem(&z, "lb", "ble", 0) ||
+         stem(&z, "zi", "ize", 0) ){
+       /* Do nothing.  The work was all in the test */
+     }else if( doubleConsonant(z) && (*z!='l' && *z!='s' && *z!='z') ){
+       z++;
+     }else if( m_eq_1(z) && star_oh(z) ){
+       *(--z) = 'e';
+     }
   }
-  pTokenizer->pModule = pModule;
 
-  zExpr = (const char *)sqlite3_value_text(argv[1]);
-  nExpr = sqlite3_value_bytes(argv[1]);
-  nCol = argc-2;
-  azCol = (char **)sqlite3_malloc(nCol*sizeof(char *));
-  if( !azCol ){
-    sqlite3_result_error_nomem(context);
-    goto exprtest_out;
+  /* Step 1c */
+  if( z[0]=='y' && hasVowel(z+1) ){
+    z[0] = 'i';
   }
-  for(ii=0; ii<nCol; ii++){
-    azCol[ii] = (char *)sqlite3_value_text(argv[ii+2]);
+
+  /* Step 2 */
+  switch( z[1] ){
+   case 'a':
+     if( !stem(&z, "lanoita", "ate", m_gt_0) ){
+       stem(&z, "lanoit", "tion", m_gt_0);
+     }
+     break;
+   case 'c':
+     if( !stem(&z, "icne", "ence", m_gt_0) ){
+       stem(&z, "icna", "ance", m_gt_0);
+     }
+     break;
+   case 'e':
+     stem(&z, "rezi", "ize", m_gt_0);
+     break;
+   case 'g':
+     stem(&z, "igol", "log", m_gt_0);
+     break;
+   case 'l':
+     if( !stem(&z, "ilb", "ble", m_gt_0) 
+      && !stem(&z, "illa", "al", m_gt_0)
+      && !stem(&z, "iltne", "ent", m_gt_0)
+      && !stem(&z, "ile", "e", m_gt_0)
+     ){
+       stem(&z, "ilsuo", "ous", m_gt_0);
+     }
+     break;
+   case 'o':
+     if( !stem(&z, "noitazi", "ize", m_gt_0)
+      && !stem(&z, "noita", "ate", m_gt_0)
+     ){
+       stem(&z, "rota", "ate", m_gt_0);
+     }
+     break;
+   case 's':
+     if( !stem(&z, "msila", "al", m_gt_0)
+      && !stem(&z, "ssenevi", "ive", m_gt_0)
+      && !stem(&z, "ssenluf", "ful", m_gt_0)
+     ){
+       stem(&z, "ssensuo", "ous", m_gt_0);
+     }
+     break;
+   case 't':
+     if( !stem(&z, "itila", "al", m_gt_0)
+      && !stem(&z, "itivi", "ive", m_gt_0)
+     ){
+       stem(&z, "itilib", "ble", m_gt_0);
+     }
+     break;
   }
 
-  if( sqlite3_user_data(context) ){
-    char *zDummy = 0;
-    rc = sqlite3Fts3ExprParse(
-        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr, &zDummy
-    );
-    assert( rc==SQLITE_OK || pExpr==0 );
-    sqlite3_free(zDummy);
-  }else{
-    rc = fts3ExprParseUnbalanced(
-        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr
-    );
+  /* Step 3 */
+  switch( z[0] ){
+   case 'e':
+     if( !stem(&z, "etaci", "ic", m_gt_0)
+      && !stem(&z, "evita", "", m_gt_0)
+     ){
+       stem(&z, "ezila", "al", m_gt_0);
+     }
+     break;
+   case 'i':
+     stem(&z, "itici", "ic", m_gt_0);
+     break;
+   case 'l':
+     if( !stem(&z, "laci", "ic", m_gt_0) ){
+       stem(&z, "luf", "", m_gt_0);
+     }
+     break;
+   case 's':
+     stem(&z, "ssen", "", m_gt_0);
+     break;
   }
 
-  if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
-    sqlite3Fts3ExprFree(pExpr);
-    sqlite3_result_error(context, "Error parsing expression", -1);
-  }else if( rc==SQLITE_NOMEM || !(zBuf = exprToString(pExpr, 0)) ){
-    sqlite3_result_error_nomem(context);
-  }else{
-    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
-    sqlite3_free(zBuf);
+  /* Step 4 */
+  switch( z[1] ){
+   case 'a':
+     if( z[0]=='l' && m_gt_1(z+2) ){
+       z += 2;
+     }
+     break;
+   case 'c':
+     if( z[0]=='e' && z[2]=='n' && (z[3]=='a' || z[3]=='e')  && m_gt_1(z+4)  ){
+       z += 4;
+     }
+     break;
+   case 'e':
+     if( z[0]=='r' && m_gt_1(z+2) ){
+       z += 2;
+     }
+     break;
+   case 'i':
+     if( z[0]=='c' && m_gt_1(z+2) ){
+       z += 2;
+     }
+     break;
+   case 'l':
+     if( z[0]=='e' && z[2]=='b' && (z[3]=='a' || z[3]=='i') && m_gt_1(z+4) ){
+       z += 4;
+     }
+     break;
+   case 'n':
+     if( z[0]=='t' ){
+       if( z[2]=='a' ){
+         if( m_gt_1(z+3) ){
+           z += 3;
+         }
+       }else if( z[2]=='e' ){
+         if( !stem(&z, "tneme", "", m_gt_1)
+          && !stem(&z, "tnem", "", m_gt_1)
+         ){
+           stem(&z, "tne", "", m_gt_1);
+         }
+       }
+     }
+     break;
+   case 'o':
+     if( z[0]=='u' ){
+       if( m_gt_1(z+2) ){
+         z += 2;
+       }
+     }else if( z[3]=='s' || z[3]=='t' ){
+       stem(&z, "noi", "", m_gt_1);
+     }
+     break;
+   case 's':
+     if( z[0]=='m' && z[2]=='i' && m_gt_1(z+3) ){
+       z += 3;
+     }
+     break;
+   case 't':
+     if( !stem(&z, "eta", "", m_gt_1) ){
+       stem(&z, "iti", "", m_gt_1);
+     }
+     break;
+   case 'u':
+     if( z[0]=='s' && z[2]=='o' && m_gt_1(z+3) ){
+       z += 3;
+     }
+     break;
+   case 'v':
+   case 'z':
+     if( z[0]=='e' && z[2]=='i' && m_gt_1(z+3) ){
+       z += 3;
+     }
+     break;
   }
 
-  sqlite3Fts3ExprFree(pExpr);
+  /* Step 5a */
+  if( z[0]=='e' ){
+    if( m_gt_1(z+1) ){
+      z++;
+    }else if( m_eq_1(z+1) && !star_oh(z+1) ){
+      z++;
+    }
+  }
 
-exprtest_out:
-  if( pModule && pTokenizer ){
-    rc = pModule->xDestroy(pTokenizer);
+  /* Step 5b */
+  if( m_gt_1(z) && z[0]=='l' && z[1]=='l' ){
+    z++;
+  }
+
+  /* z[] is now the stemmed word in reverse order.  Flip it back
+  ** around into forward order and return.
+  */
+  *pnOut = i = (int)strlen(z);
+  zOut[i] = 0;
+  while( *z ){
+    zOut[--i] = *(z++);
   }
-  sqlite3_free(azCol);
 }
 
 /*
-** Register the query expression parser test function fts3_exprtest() 
-** with database connection db. 
+** Characters that can be part of a token.  We assume any character
+** whose value is greater than 0x80 (any UTF character) can be
+** part of a token.  In other words, delimiters all must have
+** values of 0x7f or lower.
 */
-SQLITE_PRIVATE int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
-  int rc = sqlite3_create_function(
-      db, "fts3_exprtest", -1, SQLITE_UTF8, 0, fts3ExprTest, 0, 0
-  );
-  if( rc==SQLITE_OK ){
-    rc = sqlite3_create_function(db, "fts3_exprtest_rebalance", 
-        -1, SQLITE_UTF8, (void *)1, fts3ExprTest, 0, 0
-    );
+static const char porterIdChar[] = {
+/* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 3x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 4x */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,  /* 5x */
+    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 6x */
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,  /* 7x */
+};
+#define isDelim(C) (((ch=C)&0x80)==0 && (ch<0x30 || !porterIdChar[ch-0x30]))
+
+/*
+** Extract the next token from a tokenization cursor.  The cursor must
+** have been opened by a prior call to porterOpen().
+*/
+static int porterNext(
+  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by porterOpen */
+  const char **pzToken,               /* OUT: *pzToken is the token text */
+  int *pnBytes,                       /* OUT: Number of bytes in token */
+  int *piStartOffset,                 /* OUT: Starting offset of token */
+  int *piEndOffset,                   /* OUT: Ending offset of token */
+  int *piPosition                     /* OUT: Position integer of token */
+){
+  porter_tokenizer_cursor *c = (porter_tokenizer_cursor *) pCursor;
+  const char *z = c->zInput;
+
+  while( c->iOffset<c->nInput ){
+    int iStartOffset, ch;
+
+    /* Scan past delimiter characters */
+    while( c->iOffset<c->nInput && isDelim(z[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    /* Count non-delimiter characters. */
+    iStartOffset = c->iOffset;
+    while( c->iOffset<c->nInput && !isDelim(z[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    if( c->iOffset>iStartOffset ){
+      int n = c->iOffset-iStartOffset;
+      if( n>c->nAllocated ){
+        char *pNew;
+        c->nAllocated = n+20;
+        pNew = sqlite3_realloc(c->zToken, c->nAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->zToken = pNew;
+      }
+      porter_stemmer(&z[iStartOffset], n, c->zToken, pnBytes);
+      *pzToken = c->zToken;
+      *piStartOffset = iStartOffset;
+      *piEndOffset = c->iOffset;
+      *piPosition = c->iToken++;
+      return SQLITE_OK;
+    }
   }
-  return rc;
+  return SQLITE_DONE;
+}
+
+/*
+** The set of routines that implement the porter-stemmer tokenizer
+*/
+static const sqlite3_tokenizer_module porterTokenizerModule = {
+  0,
+  porterCreate,
+  porterDestroy,
+  porterOpen,
+  porterClose,
+  porterNext,
+  0
+};
+
+/*
+** Allocate a new porter tokenizer.  Return a pointer to the new
+** tokenizer in *ppModule
+*/
+SQLITE_PRIVATE void sqlite3Fts3PorterTokenizerModule(
+  sqlite3_tokenizer_module const**ppModule
+){
+  *ppModule = &porterTokenizerModule;
 }
 
-#endif
 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
 
-/************** End of fts3_expr.c *******************************************/
-/************** Begin file fts3_hash.c ***************************************/
+/************** End of fts3_porter.c *****************************************/
+/************** Begin file fts3_tokenizer.c **********************************/
 /*
-** 2001 September 22
+** 2007 June 22
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
@@ -140733,10 +143270,10 @@ SQLITE_PRIVATE int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
-*************************************************************************
-** This is the implementation of generic hash-tables used in SQLite.
-** We've modified it slightly to serve as a standalone hash table
-** implementation for the full-text indexing module.
+******************************************************************************
+**
+** This is part of an SQLite module implementing full-text search.
+** This particular file implements the generic tokenizer interface.
 */
 
 /*
@@ -140748,367 +143285,480 @@ SQLITE_PRIVATE int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
 **     * The FTS3 module is being built into the core of
 **       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
 */
+/* #include "fts3Int.h" */
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 /* #include <assert.h> */
-/* #include <stdlib.h> */
 /* #include <string.h> */
 
-
 /*
-** Malloc and Free functions
+** Implementation of the SQL scalar function for accessing the underlying 
+** hash table. This function may be called as follows:
+**
+**   SELECT <function-name>(<key-name>);
+**   SELECT <function-name>(<key-name>, <pointer>);
+**
+** where <function-name> is the name passed as the second argument
+** to the sqlite3Fts3InitHashTable() function (e.g. 'fts3_tokenizer').
+**
+** If the <pointer> argument is specified, it must be a blob value
+** containing a pointer to be stored as the hash data corresponding
+** to the string <key-name>. If <pointer> is not specified, then
+** the string <key-name> must already exist in the has table. Otherwise,
+** an error is returned.
+**
+** Whether or not the <pointer> argument is specified, the value returned
+** is a blob containing the pointer stored as the hash data corresponding
+** to string <key-name> (after the hash-table is updated, if applicable).
 */
-static void *fts3HashMalloc(int n){
-  void *p = sqlite3_malloc(n);
-  if( p ){
-    memset(p, 0, n);
+static void scalarFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  Fts3Hash *pHash;
+  void *pPtr = 0;
+  const unsigned char *zName;
+  int nName;
+
+  assert( argc==1 || argc==2 );
+
+  pHash = (Fts3Hash *)sqlite3_user_data(context);
+
+  zName = sqlite3_value_text(argv[0]);
+  nName = sqlite3_value_bytes(argv[0])+1;
+
+  if( argc==2 ){
+    void *pOld;
+    int n = sqlite3_value_bytes(argv[1]);
+    if( zName==0 || n!=sizeof(pPtr) ){
+      sqlite3_result_error(context, "argument type mismatch", -1);
+      return;
+    }
+    pPtr = *(void **)sqlite3_value_blob(argv[1]);
+    pOld = sqlite3Fts3HashInsert(pHash, (void *)zName, nName, pPtr);
+    if( pOld==pPtr ){
+      sqlite3_result_error(context, "out of memory", -1);
+      return;
+    }
+  }else{
+    if( zName ){
+      pPtr = sqlite3Fts3HashFind(pHash, zName, nName);
+    }
+    if( !pPtr ){
+      char *zErr = sqlite3_mprintf("unknown tokenizer: %s", zName);
+      sqlite3_result_error(context, zErr, -1);
+      sqlite3_free(zErr);
+      return;
+    }
   }
-  return p;
+
+  sqlite3_result_blob(context, (void *)&pPtr, sizeof(pPtr), SQLITE_TRANSIENT);
 }
-static void fts3HashFree(void *p){
-  sqlite3_free(p);
+
+SQLITE_PRIVATE int sqlite3Fts3IsIdChar(char c){
+  static const char isFtsIdChar[] = {
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 0x */
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 1x */
+      0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 2x */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 3x */
+      0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 4x */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,  /* 5x */
+      0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 6x */
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,  /* 7x */
+  };
+  return (c&0x80 || isFtsIdChar[(int)(c)]);
 }
 
-/* Turn bulk memory into a hash table object by initializing the
-** fields of the Hash structure.
-**
-** "pNew" is a pointer to the hash table that is to be initialized.
-** keyClass is one of the constants 
-** FTS3_HASH_BINARY or FTS3_HASH_STRING.  The value of keyClass 
-** determines what kind of key the hash table will use.  "copyKey" is
-** true if the hash table should make its own private copy of keys and
-** false if it should just use the supplied pointer.
-*/
-SQLITE_PRIVATE void sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey){
-  assert( pNew!=0 );
-  assert( keyClass>=FTS3_HASH_STRING && keyClass<=FTS3_HASH_BINARY );
-  pNew->keyClass = keyClass;
-  pNew->copyKey = copyKey;
-  pNew->first = 0;
-  pNew->count = 0;
-  pNew->htsize = 0;
-  pNew->ht = 0;
+SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *zStr, int *pn){
+  const char *z1;
+  const char *z2 = 0;
+
+  /* Find the start of the next token. */
+  z1 = zStr;
+  while( z2==0 ){
+    char c = *z1;
+    switch( c ){
+      case '\0': return 0;        /* No more tokens here */
+      case '\'':
+      case '"':
+      case '`': {
+        z2 = z1;
+        while( *++z2 && (*z2!=c || *++z2==c) );
+        break;
+      }
+      case '[':
+        z2 = &z1[1];
+        while( *z2 && z2[0]!=']' ) z2++;
+        if( *z2 ) z2++;
+        break;
+
+      default:
+        if( sqlite3Fts3IsIdChar(*z1) ){
+          z2 = &z1[1];
+          while( sqlite3Fts3IsIdChar(*z2) ) z2++;
+        }else{
+          z1++;
+        }
+    }
+  }
+
+  *pn = (int)(z2-z1);
+  return z1;
 }
 
-/* Remove all entries from a hash table.  Reclaim all memory.
-** Call this routine to delete a hash table or to reset a hash table
-** to the empty state.
-*/
-SQLITE_PRIVATE void sqlite3Fts3HashClear(Fts3Hash *pH){
-  Fts3HashElem *elem;         /* For looping over all elements of the table */
+SQLITE_PRIVATE int sqlite3Fts3InitTokenizer(
+  Fts3Hash *pHash,                /* Tokenizer hash table */
+  const char *zArg,               /* Tokenizer name */
+  sqlite3_tokenizer **ppTok,      /* OUT: Tokenizer (if applicable) */
+  char **pzErr                    /* OUT: Set to malloced error message */
+){
+  int rc;
+  char *z = (char *)zArg;
+  int n = 0;
+  char *zCopy;
+  char *zEnd;                     /* Pointer to nul-term of zCopy */
+  sqlite3_tokenizer_module *m;
 
-  assert( pH!=0 );
-  elem = pH->first;
-  pH->first = 0;
-  fts3HashFree(pH->ht);
-  pH->ht = 0;
-  pH->htsize = 0;
-  while( elem ){
-    Fts3HashElem *next_elem = elem->next;
-    if( pH->copyKey && elem->pKey ){
-      fts3HashFree(elem->pKey);
+  zCopy = sqlite3_mprintf("%s", zArg);
+  if( !zCopy ) return SQLITE_NOMEM;
+  zEnd = &zCopy[strlen(zCopy)];
+
+  z = (char *)sqlite3Fts3NextToken(zCopy, &n);
+  if( z==0 ){
+    assert( n==0 );
+    z = zCopy;
+  }
+  z[n] = '\0';
+  sqlite3Fts3Dequote(z);
+
+  m = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash,z,(int)strlen(z)+1);
+  if( !m ){
+    sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer: %s", z);
+    rc = SQLITE_ERROR;
+  }else{
+    char const **aArg = 0;
+    int iArg = 0;
+    z = &z[n+1];
+    while( z<zEnd && (NULL!=(z = (char *)sqlite3Fts3NextToken(z, &n))) ){
+      int nNew = sizeof(char *)*(iArg+1);
+      char const **aNew = (const char **)sqlite3_realloc((void *)aArg, nNew);
+      if( !aNew ){
+        sqlite3_free(zCopy);
+        sqlite3_free((void *)aArg);
+        return SQLITE_NOMEM;
+      }
+      aArg = aNew;
+      aArg[iArg++] = z;
+      z[n] = '\0';
+      sqlite3Fts3Dequote(z);
+      z = &z[n+1];
     }
-    fts3HashFree(elem);
-    elem = next_elem;
+    rc = m->xCreate(iArg, aArg, ppTok);
+    assert( rc!=SQLITE_OK || *ppTok );
+    if( rc!=SQLITE_OK ){
+      sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer");
+    }else{
+      (*ppTok)->pModule = m; 
+    }
+    sqlite3_free((void *)aArg);
+  }
+
+  sqlite3_free(zCopy);
+  return rc;
+}
+
+
+#ifdef SQLITE_TEST
+
+#include <tcl.h>
+/* #include <string.h> */
+
+/*
+** Implementation of a special SQL scalar function for testing tokenizers 
+** designed to be used in concert with the Tcl testing framework. This
+** function must be called with two or more arguments:
+**
+**   SELECT <function-name>(<key-name>, ..., <input-string>);
+**
+** where <function-name> is the name passed as the second argument
+** to the sqlite3Fts3InitHashTable() function (e.g. 'fts3_tokenizer')
+** concatenated with the string '_test' (e.g. 'fts3_tokenizer_test').
+**
+** The return value is a string that may be interpreted as a Tcl
+** list. For each token in the <input-string>, three elements are
+** added to the returned list. The first is the token position, the 
+** second is the token text (folded, stemmed, etc.) and the third is the
+** substring of <input-string> associated with the token. For example, 
+** using the built-in "simple" tokenizer:
+**
+**   SELECT fts_tokenizer_test('simple', 'I don't see how');
+**
+** will return the string:
+**
+**   "{0 i I 1 dont don't 2 see see 3 how how}"
+**   
+*/
+static void testFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  Fts3Hash *pHash;
+  sqlite3_tokenizer_module *p;
+  sqlite3_tokenizer *pTokenizer = 0;
+  sqlite3_tokenizer_cursor *pCsr = 0;
+
+  const char *zErr = 0;
+
+  const char *zName;
+  int nName;
+  const char *zInput;
+  int nInput;
+
+  const char *azArg[64];
+
+  const char *zToken;
+  int nToken = 0;
+  int iStart = 0;
+  int iEnd = 0;
+  int iPos = 0;
+  int i;
+
+  Tcl_Obj *pRet;
+
+  if( argc<2 ){
+    sqlite3_result_error(context, "insufficient arguments", -1);
+    return;
+  }
+
+  nName = sqlite3_value_bytes(argv[0]);
+  zName = (const char *)sqlite3_value_text(argv[0]);
+  nInput = sqlite3_value_bytes(argv[argc-1]);
+  zInput = (const char *)sqlite3_value_text(argv[argc-1]);
+
+  pHash = (Fts3Hash *)sqlite3_user_data(context);
+  p = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash, zName, nName+1);
+
+  if( !p ){
+    char *zErr2 = sqlite3_mprintf("unknown tokenizer: %s", zName);
+    sqlite3_result_error(context, zErr2, -1);
+    sqlite3_free(zErr2);
+    return;
+  }
+
+  pRet = Tcl_NewObj();
+  Tcl_IncrRefCount(pRet);
+
+  for(i=1; i<argc-1; i++){
+    azArg[i-1] = (const char *)sqlite3_value_text(argv[i]);
+  }
+
+  if( SQLITE_OK!=p->xCreate(argc-2, azArg, &pTokenizer) ){
+    zErr = "error in xCreate()";
+    goto finish;
+  }
+  pTokenizer->pModule = p;
+  if( sqlite3Fts3OpenTokenizer(pTokenizer, 0, zInput, nInput, &pCsr) ){
+    zErr = "error in xOpen()";
+    goto finish;
   }
-  pH->count = 0;
-}
 
-/*
-** Hash and comparison functions when the mode is FTS3_HASH_STRING
-*/
-static int fts3StrHash(const void *pKey, int nKey){
-  const char *z = (const char *)pKey;
-  unsigned h = 0;
-  if( nKey<=0 ) nKey = (int) strlen(z);
-  while( nKey > 0  ){
-    h = (h<<3) ^ h ^ *z++;
-    nKey--;
+  while( SQLITE_OK==p->xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos) ){
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(iPos));
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zToken, nToken));
+    zToken = &zInput[iStart];
+    nToken = iEnd-iStart;
+    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zToken, nToken));
   }
-  return (int)(h & 0x7fffffff);
-}
-static int fts3StrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
-  if( n1!=n2 ) return 1;
-  return strncmp((const char*)pKey1,(const char*)pKey2,n1);
-}
 
-/*
-** Hash and comparison functions when the mode is FTS3_HASH_BINARY
-*/
-static int fts3BinHash(const void *pKey, int nKey){
-  int h = 0;
-  const char *z = (const char *)pKey;
-  while( nKey-- > 0 ){
-    h = (h<<3) ^ h ^ *(z++);
+  if( SQLITE_OK!=p->xClose(pCsr) ){
+    zErr = "error in xClose()";
+    goto finish;
   }
-  return h & 0x7fffffff;
-}
-static int fts3BinCompare(const void *pKey1, int n1, const void *pKey2, int n2){
-  if( n1!=n2 ) return 1;
-  return memcmp(pKey1,pKey2,n1);
-}
-
-/*
-** Return a pointer to the appropriate hash function given the key class.
-**
-** The C syntax in this function definition may be unfamilar to some 
-** programmers, so we provide the following additional explanation:
-**
-** The name of the function is "ftsHashFunction".  The function takes a
-** single parameter "keyClass".  The return value of ftsHashFunction()
-** is a pointer to another function.  Specifically, the return value
-** of ftsHashFunction() is a pointer to a function that takes two parameters
-** with types "const void*" and "int" and returns an "int".
-*/
-static int (*ftsHashFunction(int keyClass))(const void*,int){
-  if( keyClass==FTS3_HASH_STRING ){
-    return &fts3StrHash;
-  }else{
-    assert( keyClass==FTS3_HASH_BINARY );
-    return &fts3BinHash;
+  if( SQLITE_OK!=p->xDestroy(pTokenizer) ){
+    zErr = "error in xDestroy()";
+    goto finish;
   }
-}
 
-/*
-** Return a pointer to the appropriate hash function given the key class.
-**
-** For help in interpreted the obscure C code in the function definition,
-** see the header comment on the previous function.
-*/
-static int (*ftsCompareFunction(int keyClass))(const void*,int,const void*,int){
-  if( keyClass==FTS3_HASH_STRING ){
-    return &fts3StrCompare;
+finish:
+  if( zErr ){
+    sqlite3_result_error(context, zErr, -1);
   }else{
-    assert( keyClass==FTS3_HASH_BINARY );
-    return &fts3BinCompare;
+    sqlite3_result_text(context, Tcl_GetString(pRet), -1, SQLITE_TRANSIENT);
   }
+  Tcl_DecrRefCount(pRet);
 }
 
-/* Link an element into the hash table
-*/
-static void fts3HashInsertElement(
-  Fts3Hash *pH,            /* The complete hash table */
-  struct _fts3ht *pEntry,  /* The entry into which pNew is inserted */
-  Fts3HashElem *pNew       /* The element to be inserted */
+static
+int registerTokenizer(
+  sqlite3 *db, 
+  char *zName, 
+  const sqlite3_tokenizer_module *p
 ){
-  Fts3HashElem *pHead;     /* First element already in pEntry */
-  pHead = pEntry->chain;
-  if( pHead ){
-    pNew->next = pHead;
-    pNew->prev = pHead->prev;
-    if( pHead->prev ){ pHead->prev->next = pNew; }
-    else             { pH->first = pNew; }
-    pHead->prev = pNew;
-  }else{
-    pNew->next = pH->first;
-    if( pH->first ){ pH->first->prev = pNew; }
-    pNew->prev = 0;
-    pH->first = pNew;
-  }
-  pEntry->count++;
-  pEntry->chain = pNew;
-}
+  int rc;
+  sqlite3_stmt *pStmt;
+  const char zSql[] = "SELECT fts3_tokenizer(?, ?)";
 
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
 
-/* Resize the hash table so that it cantains "new_size" buckets.
-** "new_size" must be a power of 2.  The hash table might fail 
-** to resize if sqliteMalloc() fails.
-**
-** Return non-zero if a memory allocation error occurs.
-*/
-static int fts3Rehash(Fts3Hash *pH, int new_size){
-  struct _fts3ht *new_ht;          /* The new hash table */
-  Fts3HashElem *elem, *next_elem;  /* For looping over existing elements */
-  int (*xHash)(const void*,int);   /* The hash function */
+  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
+  sqlite3_bind_blob(pStmt, 2, &p, sizeof(p), SQLITE_STATIC);
+  sqlite3_step(pStmt);
 
-  assert( (new_size & (new_size-1))==0 );
-  new_ht = (struct _fts3ht *)fts3HashMalloc( new_size*sizeof(struct _fts3ht) );
-  if( new_ht==0 ) return 1;
-  fts3HashFree(pH->ht);
-  pH->ht = new_ht;
-  pH->htsize = new_size;
-  xHash = ftsHashFunction(pH->keyClass);
-  for(elem=pH->first, pH->first=0; elem; elem = next_elem){
-    int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
-    next_elem = elem->next;
-    fts3HashInsertElement(pH, &new_ht[h], elem);
-  }
-  return 0;
+  return sqlite3_finalize(pStmt);
 }
 
-/* This function (for internal use only) locates an element in an
-** hash table that matches the given key.  The hash for this key has
-** already been computed and is passed as the 4th parameter.
-*/
-static Fts3HashElem *fts3FindElementByHash(
-  const Fts3Hash *pH, /* The pH to be searched */
-  const void *pKey,   /* The key we are searching for */
-  int nKey,
-  int h               /* The hash for this key. */
+static
+int queryTokenizer(
+  sqlite3 *db, 
+  char *zName,  
+  const sqlite3_tokenizer_module **pp
 ){
-  Fts3HashElem *elem;            /* Used to loop thru the element list */
-  int count;                     /* Number of elements left to test */
-  int (*xCompare)(const void*,int,const void*,int);  /* comparison function */
+  int rc;
+  sqlite3_stmt *pStmt;
+  const char zSql[] = "SELECT fts3_tokenizer(?)";
 
-  if( pH->ht ){
-    struct _fts3ht *pEntry = &pH->ht[h];
-    elem = pEntry->chain;
-    count = pEntry->count;
-    xCompare = ftsCompareFunction(pH->keyClass);
-    while( count-- && elem ){
-      if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){ 
-        return elem;
-      }
-      elem = elem->next;
+  *pp = 0;
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
+      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
     }
   }
-  return 0;
+
+  return sqlite3_finalize(pStmt);
 }
 
-/* Remove a single entry from the hash table given a pointer to that
-** element and a hash on the element's key.
+SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(sqlite3_tokenizer_module const**ppModule);
+
+/*
+** Implementation of the scalar function fts3_tokenizer_internal_test().
+** This function is used for testing only, it is not included in the
+** build unless SQLITE_TEST is defined.
+**
+** The purpose of this is to test that the fts3_tokenizer() function
+** can be used as designed by the C-code in the queryTokenizer and
+** registerTokenizer() functions above. These two functions are repeated
+** in the README.tokenizer file as an example, so it is important to
+** test them.
+**
+** To run the tests, evaluate the fts3_tokenizer_internal_test() scalar
+** function with no arguments. An assert() will fail if a problem is
+** detected. i.e.:
+**
+**     SELECT fts3_tokenizer_internal_test();
+**
 */
-static void fts3RemoveElementByHash(
-  Fts3Hash *pH,         /* The pH containing "elem" */
-  Fts3HashElem* elem,   /* The element to be removed from the pH */
-  int h                 /* Hash value for the element */
+static void intTestFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
 ){
-  struct _fts3ht *pEntry;
-  if( elem->prev ){
-    elem->prev->next = elem->next; 
-  }else{
-    pH->first = elem->next;
-  }
-  if( elem->next ){
-    elem->next->prev = elem->prev;
-  }
-  pEntry = &pH->ht[h];
-  if( pEntry->chain==elem ){
-    pEntry->chain = elem->next;
-  }
-  pEntry->count--;
-  if( pEntry->count<=0 ){
-    pEntry->chain = 0;
-  }
-  if( pH->copyKey && elem->pKey ){
-    fts3HashFree(elem->pKey);
-  }
-  fts3HashFree( elem );
-  pH->count--;
-  if( pH->count<=0 ){
-    assert( pH->first==0 );
-    assert( pH->count==0 );
-    fts3HashClear(pH);
-  }
-}
+  int rc;
+  const sqlite3_tokenizer_module *p1;
+  const sqlite3_tokenizer_module *p2;
+  sqlite3 *db = (sqlite3 *)sqlite3_user_data(context);
 
-SQLITE_PRIVATE Fts3HashElem *sqlite3Fts3HashFindElem(
-  const Fts3Hash *pH, 
-  const void *pKey, 
-  int nKey
-){
-  int h;                          /* A hash on key */
-  int (*xHash)(const void*,int);  /* The hash function */
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(argv);
 
-  if( pH==0 || pH->ht==0 ) return 0;
-  xHash = ftsHashFunction(pH->keyClass);
-  assert( xHash!=0 );
-  h = (*xHash)(pKey,nKey);
-  assert( (pH->htsize & (pH->htsize-1))==0 );
-  return fts3FindElementByHash(pH,pKey,nKey, h & (pH->htsize-1));
-}
+  /* Test the query function */
+  sqlite3Fts3SimpleTokenizerModule(&p1);
+  rc = queryTokenizer(db, "simple", &p2);
+  assert( rc==SQLITE_OK );
+  assert( p1==p2 );
+  rc = queryTokenizer(db, "nosuchtokenizer", &p2);
+  assert( rc==SQLITE_ERROR );
+  assert( p2==0 );
+  assert( 0==strcmp(sqlite3_errmsg(db), "unknown tokenizer: nosuchtokenizer") );
 
-/* 
-** Attempt to locate an element of the hash table pH with a key
-** that matches pKey,nKey.  Return the data for this element if it is
-** found, or NULL if there is no match.
-*/
-SQLITE_PRIVATE void *sqlite3Fts3HashFind(const Fts3Hash *pH, const void *pKey, int nKey){
-  Fts3HashElem *pElem;            /* The element that matches key (if any) */
+  /* Test the storage function */
+  rc = registerTokenizer(db, "nosuchtokenizer", p1);
+  assert( rc==SQLITE_OK );
+  rc = queryTokenizer(db, "nosuchtokenizer", &p2);
+  assert( rc==SQLITE_OK );
+  assert( p2==p1 );
 
-  pElem = sqlite3Fts3HashFindElem(pH, pKey, nKey);
-  return pElem ? pElem->data : 0;
+  sqlite3_result_text(context, "ok", -1, SQLITE_STATIC);
 }
 
-/* Insert an element into the hash table pH.  The key is pKey,nKey
-** and the data is "data".
+#endif
+
+/*
+** Set up SQL objects in database db used to access the contents of
+** the hash table pointed to by argument pHash. The hash table must
+** been initialized to use string keys, and to take a private copy 
+** of the key when a value is inserted. i.e. by a call similar to:
 **
-** If no element exists with a matching key, then a new
-** element is created.  A copy of the key is made if the copyKey
-** flag is set.  NULL is returned.
+**    sqlite3Fts3HashInit(pHash, FTS3_HASH_STRING, 1);
 **
-** If another element already exists with the same key, then the
-** new data replaces the old data and the old data is returned.
-** The key is not copied in this instance.  If a malloc fails, then
-** the new data is returned and the hash table is unchanged.
+** This function adds a scalar function (see header comment above
+** scalarFunc() in this file for details) and, if ENABLE_TABLE is
+** defined at compilation time, a temporary virtual table (see header 
+** comment above struct HashTableVtab) to the database schema. Both 
+** provide read/write access to the contents of *pHash.
 **
-** If the "data" parameter to this function is NULL, then the
-** element corresponding to "key" is removed from the hash table.
+** The third argument to this function, zName, is used as the name
+** of both the scalar and, if created, the virtual table.
 */
-SQLITE_PRIVATE void *sqlite3Fts3HashInsert(
-  Fts3Hash *pH,        /* The hash table to insert into */
-  const void *pKey,    /* The key */
-  int nKey,            /* Number of bytes in the key */
-  void *data           /* The data */
+SQLITE_PRIVATE int sqlite3Fts3InitHashTable(
+  sqlite3 *db, 
+  Fts3Hash *pHash, 
+  const char *zName
 ){
-  int hraw;                 /* Raw hash value of the key */
-  int h;                    /* the hash of the key modulo hash table size */
-  Fts3HashElem *elem;       /* Used to loop thru the element list */
-  Fts3HashElem *new_elem;   /* New element added to the pH */
-  int (*xHash)(const void*,int);  /* The hash function */
+  int rc = SQLITE_OK;
+  void *p = (void *)pHash;
+  const int any = SQLITE_ANY;
 
-  assert( pH!=0 );
-  xHash = ftsHashFunction(pH->keyClass);
-  assert( xHash!=0 );
-  hraw = (*xHash)(pKey, nKey);
-  assert( (pH->htsize & (pH->htsize-1))==0 );
-  h = hraw & (pH->htsize-1);
-  elem = fts3FindElementByHash(pH,pKey,nKey,h);
-  if( elem ){
-    void *old_data = elem->data;
-    if( data==0 ){
-      fts3RemoveElementByHash(pH,elem,h);
-    }else{
-      elem->data = data;
-    }
-    return old_data;
+#ifdef SQLITE_TEST
+  char *zTest = 0;
+  char *zTest2 = 0;
+  void *pdb = (void *)db;
+  zTest = sqlite3_mprintf("%s_test", zName);
+  zTest2 = sqlite3_mprintf("%s_internal_test", zName);
+  if( !zTest || !zTest2 ){
+    rc = SQLITE_NOMEM;
   }
-  if( data==0 ) return 0;
-  if( (pH->htsize==0 && fts3Rehash(pH,8))
-   || (pH->count>=pH->htsize && fts3Rehash(pH, pH->htsize*2))
-  ){
-    pH->count = 0;
-    return data;
+#endif
+
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zName, 1, any, p, scalarFunc, 0, 0);
   }
-  assert( pH->htsize>0 );
-  new_elem = (Fts3HashElem*)fts3HashMalloc( sizeof(Fts3HashElem) );
-  if( new_elem==0 ) return data;
-  if( pH->copyKey && pKey!=0 ){
-    new_elem->pKey = fts3HashMalloc( nKey );
-    if( new_elem->pKey==0 ){
-      fts3HashFree(new_elem);
-      return data;
-    }
-    memcpy((void*)new_elem->pKey, pKey, nKey);
-  }else{
-    new_elem->pKey = (void*)pKey;
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zName, 2, any, p, scalarFunc, 0, 0);
   }
-  new_elem->nKey = nKey;
-  pH->count++;
-  assert( pH->htsize>0 );
-  assert( (pH->htsize & (pH->htsize-1))==0 );
-  h = hraw & (pH->htsize-1);
-  fts3HashInsertElement(pH, &pH->ht[h], new_elem);
-  new_elem->data = data;
-  return 0;
+#ifdef SQLITE_TEST
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zTest, -1, any, p, testFunc, 0, 0);
+  }
+  if( SQLITE_OK==rc ){
+    rc = sqlite3_create_function(db, zTest2, 0, any, pdb, intTestFunc, 0, 0);
+  }
+#endif
+
+#ifdef SQLITE_TEST
+  sqlite3_free(zTest);
+  sqlite3_free(zTest2);
+#endif
+
+  return rc;
 }
 
 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
 
-/************** End of fts3_hash.c *******************************************/
-/************** Begin file fts3_porter.c *************************************/
+/************** End of fts3_tokenizer.c **************************************/
+/************** Begin file fts3_tokenizer1.c *********************************/
 /*
-** 2006 September 30
+** 2006 Oct 10
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
@@ -141117,9 +143767,9 @@ SQLITE_PRIVATE void *sqlite3Fts3HashInsert(
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
-*************************************************************************
-** Implementation of the full-text-search tokenizer that implements
-** a Porter stemmer.
+******************************************************************************
+**
+** Implementation of the "simple" full-text-search tokenizer.
 */
 
 /*
@@ -141131,6 +143781,7 @@ SQLITE_PRIVATE void *sqlite3Fts3HashInsert(
 **     * The FTS3 module is being built into the core of
 **       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
 */
+/* #include "fts3Int.h" */
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 /* #include <assert.h> */
@@ -141138,43 +143789,68 @@ SQLITE_PRIVATE void *sqlite3Fts3HashInsert(
 /* #include <stdio.h> */
 /* #include <string.h> */
 
+/* #include "fts3_tokenizer.h" */
 
-/*
-** Class derived from sqlite3_tokenizer
-*/
-typedef struct porter_tokenizer {
-  sqlite3_tokenizer base;      /* Base class */
-} porter_tokenizer;
+typedef struct simple_tokenizer {
+  sqlite3_tokenizer base;
+  char delim[128];             /* flag ASCII delimiters */
+} simple_tokenizer;
 
-/*
-** Class derived from sqlite3_tokenizer_cursor
-*/
-typedef struct porter_tokenizer_cursor {
+typedef struct simple_tokenizer_cursor {
   sqlite3_tokenizer_cursor base;
-  const char *zInput;          /* input we are tokenizing */
-  int nInput;                  /* size of the input */
-  int iOffset;                 /* current position in zInput */
+  const char *pInput;          /* input we are tokenizing */
+  int nBytes;                  /* size of the input */
+  int iOffset;                 /* current position in pInput */
   int iToken;                  /* index of next token to be returned */
-  char *zToken;                /* storage for current token */
-  int nAllocated;              /* space allocated to zToken buffer */
-} porter_tokenizer_cursor;
+  char *pToken;                /* storage for current token */
+  int nTokenAllocated;         /* space allocated to zToken buffer */
+} simple_tokenizer_cursor;
+
 
+static int simpleDelim(simple_tokenizer *t, unsigned char c){
+  return c<0x80 && t->delim[c];
+}
+static int fts3_isalnum(int x){
+  return (x>='0' && x<='9') || (x>='A' && x<='Z') || (x>='a' && x<='z');
+}
 
 /*
 ** Create a new tokenizer instance.
 */
-static int porterCreate(
+static int simpleCreate(
   int argc, const char * const *argv,
   sqlite3_tokenizer **ppTokenizer
 ){
-  porter_tokenizer *t;
-
-  UNUSED_PARAMETER(argc);
-  UNUSED_PARAMETER(argv);
+  simple_tokenizer *t;
 
-  t = (porter_tokenizer *) sqlite3_malloc(sizeof(*t));
+  t = (simple_tokenizer *) sqlite3_malloc(sizeof(*t));
   if( t==NULL ) return SQLITE_NOMEM;
   memset(t, 0, sizeof(*t));
+
+  /* TODO(shess) Delimiters need to remain the same from run to run,
+  ** else we need to reindex.  One solution would be a meta-table to
+  ** track such information in the database, then we'd only want this
+  ** information on the initial create.
+  */
+  if( argc>1 ){
+    int i, n = (int)strlen(argv[1]);
+    for(i=0; i<n; i++){
+      unsigned char ch = argv[1][i];
+      /* We explicitly don't support UTF-8 delimiters for now. */
+      if( ch>=0x80 ){
+        sqlite3_free(t);
+        return SQLITE_ERROR;
+      }
+      t->delim[ch] = 1;
+    }
+  } else {
+    /* Mark non-alphanumeric ASCII characters as delimiters */
+    int i;
+    for(i=1; i<0x80; i++){
+      t->delim[i] = !fts3_isalnum(i) ? -1 : 0;
+    }
+  }
+
   *ppTokenizer = &t->base;
   return SQLITE_OK;
 }
@@ -141182,41 +143858,41 @@ static int porterCreate(
 /*
 ** Destroy a tokenizer
 */
-static int porterDestroy(sqlite3_tokenizer *pTokenizer){
+static int simpleDestroy(sqlite3_tokenizer *pTokenizer){
   sqlite3_free(pTokenizer);
   return SQLITE_OK;
 }
 
 /*
 ** Prepare to begin tokenizing a particular string.  The input
-** string to be tokenized is zInput[0..nInput-1].  A cursor
+** string to be tokenized is pInput[0..nBytes-1].  A cursor
 ** used to incrementally tokenize this string is returned in 
 ** *ppCursor.
 */
-static int porterOpen(
+static int simpleOpen(
   sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
-  const char *zInput, int nInput,        /* String to be tokenized */
+  const char *pInput, int nBytes,        /* String to be tokenized */
   sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
 ){
-  porter_tokenizer_cursor *c;
+  simple_tokenizer_cursor *c;
 
   UNUSED_PARAMETER(pTokenizer);
 
-  c = (porter_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
+  c = (simple_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
   if( c==NULL ) return SQLITE_NOMEM;
 
-  c->zInput = zInput;
-  if( zInput==0 ){
-    c->nInput = 0;
-  }else if( nInput<0 ){
-    c->nInput = (int)strlen(zInput);
+  c->pInput = pInput;
+  if( pInput==0 ){
+    c->nBytes = 0;
+  }else if( nBytes<0 ){
+    c->nBytes = (int)strlen(pInput);
   }else{
-    c->nInput = nInput;
+    c->nBytes = nBytes;
   }
   c->iOffset = 0;                 /* start tokenizing at the beginning */
   c->iToken = 0;
-  c->zToken = NULL;               /* no space allocated, yet. */
-  c->nAllocated = 0;
+  c->pToken = NULL;               /* no space allocated, yet. */
+  c->nTokenAllocated = 0;
 
   *ppCursor = &c->base;
   return SQLITE_OK;
@@ -141224,554 +143900,559 @@ static int porterOpen(
 
 /*
 ** Close a tokenization cursor previously opened by a call to
-** porterOpen() above.
+** simpleOpen() above.
 */
-static int porterClose(sqlite3_tokenizer_cursor *pCursor){
-  porter_tokenizer_cursor *c = (porter_tokenizer_cursor *) pCursor;
-  sqlite3_free(c->zToken);
+static int simpleClose(sqlite3_tokenizer_cursor *pCursor){
+  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
+  sqlite3_free(c->pToken);
   sqlite3_free(c);
   return SQLITE_OK;
 }
+
 /*
-** Vowel or consonant
+** Extract the next token from a tokenization cursor.  The cursor must
+** have been opened by a prior call to simpleOpen().
 */
-static const char cType[] = {
-   0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0,
-   1, 1, 1, 2, 1
+static int simpleNext(
+  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
+  const char **ppToken,               /* OUT: *ppToken is the token text */
+  int *pnBytes,                       /* OUT: Number of bytes in token */
+  int *piStartOffset,                 /* OUT: Starting offset of token */
+  int *piEndOffset,                   /* OUT: Ending offset of token */
+  int *piPosition                     /* OUT: Position integer of token */
+){
+  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
+  simple_tokenizer *t = (simple_tokenizer *) pCursor->pTokenizer;
+  unsigned char *p = (unsigned char *)c->pInput;
+
+  while( c->iOffset<c->nBytes ){
+    int iStartOffset;
+
+    /* Scan past delimiter characters */
+    while( c->iOffset<c->nBytes && simpleDelim(t, p[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    /* Count non-delimiter characters. */
+    iStartOffset = c->iOffset;
+    while( c->iOffset<c->nBytes && !simpleDelim(t, p[c->iOffset]) ){
+      c->iOffset++;
+    }
+
+    if( c->iOffset>iStartOffset ){
+      int i, n = c->iOffset-iStartOffset;
+      if( n>c->nTokenAllocated ){
+        char *pNew;
+        c->nTokenAllocated = n+20;
+        pNew = sqlite3_realloc(c->pToken, c->nTokenAllocated);
+        if( !pNew ) return SQLITE_NOMEM;
+        c->pToken = pNew;
+      }
+      for(i=0; i<n; i++){
+        /* TODO(shess) This needs expansion to handle UTF-8
+        ** case-insensitivity.
+        */
+        unsigned char ch = p[iStartOffset+i];
+        c->pToken[i] = (char)((ch>='A' && ch<='Z') ? ch-'A'+'a' : ch);
+      }
+      *ppToken = c->pToken;
+      *pnBytes = n;
+      *piStartOffset = iStartOffset;
+      *piEndOffset = c->iOffset;
+      *piPosition = c->iToken++;
+
+      return SQLITE_OK;
+    }
+  }
+  return SQLITE_DONE;
+}
+
+/*
+** The set of routines that implement the simple tokenizer
+*/
+static const sqlite3_tokenizer_module simpleTokenizerModule = {
+  0,
+  simpleCreate,
+  simpleDestroy,
+  simpleOpen,
+  simpleClose,
+  simpleNext,
+  0,
 };
 
 /*
-** isConsonant() and isVowel() determine if their first character in
-** the string they point to is a consonant or a vowel, according
-** to Porter ruls.  
-**
-** A consonate is any letter other than 'a', 'e', 'i', 'o', or 'u'.
-** 'Y' is a consonant unless it follows another consonant,
-** in which case it is a vowel.
-**
-** In these routine, the letters are in reverse order.  So the 'y' rule
-** is that 'y' is a consonant unless it is followed by another
-** consonent.
+** Allocate a new simple tokenizer.  Return a pointer to the new
+** tokenizer in *ppModule
 */
-static int isVowel(const char*);
-static int isConsonant(const char *z){
-  int j;
-  char x = *z;
-  if( x==0 ) return 0;
-  assert( x>='a' && x<='z' );
-  j = cType[x-'a'];
-  if( j<2 ) return j;
-  return z[1]==0 || isVowel(z + 1);
-}
-static int isVowel(const char *z){
-  int j;
-  char x = *z;
-  if( x==0 ) return 0;
-  assert( x>='a' && x<='z' );
-  j = cType[x-'a'];
-  if( j<2 ) return 1-j;
-  return isConsonant(z + 1);
+SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(
+  sqlite3_tokenizer_module const**ppModule
+){
+  *ppModule = &simpleTokenizerModule;
 }
 
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+
+/************** End of fts3_tokenizer1.c *************************************/
+/************** Begin file fts3_tokenize_vtab.c ******************************/
 /*
-** Let any sequence of one or more vowels be represented by V and let
-** C be sequence of one or more consonants.  Then every word can be
-** represented as:
+** 2013 Apr 22
 **
-**           [C] (VC){m} [V]
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
 **
-** In prose:  A word is an optional consonant followed by zero or
-** vowel-consonant pairs followed by an optional vowel.  "m" is the
-** number of vowel consonant pairs.  This routine computes the value
-** of m for the first i bytes of a word.
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
 **
-** Return true if the m-value for z is 1 or more.  In other words,
-** return true if z contains at least one vowel that is followed
-** by a consonant.
+******************************************************************************
+**
+** This file contains code for the "fts3tokenize" virtual table module.
+** An fts3tokenize virtual table is created as follows:
+**
+**   CREATE VIRTUAL TABLE <tbl> USING fts3tokenize(
+**       <tokenizer-name>, <arg-1>, ...
+**   );
+**
+** The table created has the following schema:
+**
+**   CREATE TABLE <tbl>(input, token, start, end, position)
+**
+** When queried, the query must include a WHERE clause of type:
+**
+**   input = <string>
+**
+** The virtual table module tokenizes this <string>, using the FTS3 
+** tokenizer specified by the arguments to the CREATE VIRTUAL TABLE 
+** statement and returns one row for each token in the result. With
+** fields set as follows:
+**
+**   input:   Always set to a copy of <string>
+**   token:   A token from the input.
+**   start:   Byte offset of the token within the input <string>.
+**   end:     Byte offset of the byte immediately following the end of the
+**            token within the input string.
+**   pos:     Token offset of token within input.
 **
-** In this routine z[] is in reverse order.  So we are really looking
-** for an instance of a consonant followed by a vowel.
 */
-static int m_gt_0(const char *z){
-  while( isVowel(z) ){ z++; }
-  if( *z==0 ) return 0;
-  while( isConsonant(z) ){ z++; }
-  return *z!=0;
-}
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
-/* Like mgt0 above except we are looking for a value of m which is
-** exactly 1
-*/
-static int m_eq_1(const char *z){
-  while( isVowel(z) ){ z++; }
-  if( *z==0 ) return 0;
-  while( isConsonant(z) ){ z++; }
-  if( *z==0 ) return 0;
-  while( isVowel(z) ){ z++; }
-  if( *z==0 ) return 1;
-  while( isConsonant(z) ){ z++; }
-  return *z==0;
-}
+/* #include <string.h> */
+/* #include <assert.h> */
 
-/* Like mgt0 above except we are looking for a value of m>1 instead
-** or m>0
-*/
-static int m_gt_1(const char *z){
-  while( isVowel(z) ){ z++; }
-  if( *z==0 ) return 0;
-  while( isConsonant(z) ){ z++; }
-  if( *z==0 ) return 0;
-  while( isVowel(z) ){ z++; }
-  if( *z==0 ) return 0;
-  while( isConsonant(z) ){ z++; }
-  return *z!=0;
-}
+typedef struct Fts3tokTable Fts3tokTable;
+typedef struct Fts3tokCursor Fts3tokCursor;
 
 /*
-** Return TRUE if there is a vowel anywhere within z[0..n-1]
+** Virtual table structure.
 */
-static int hasVowel(const char *z){
-  while( isConsonant(z) ){ z++; }
-  return *z!=0;
-}
+struct Fts3tokTable {
+  sqlite3_vtab base;              /* Base class used by SQLite core */
+  const sqlite3_tokenizer_module *pMod;
+  sqlite3_tokenizer *pTok;
+};
 
 /*
-** Return TRUE if the word ends in a double consonant.
-**
-** The text is reversed here. So we are really looking at
-** the first two characters of z[].
+** Virtual table cursor structure.
 */
-static int doubleConsonant(const char *z){
-  return isConsonant(z) && z[0]==z[1];
-}
+struct Fts3tokCursor {
+  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
+  char *zInput;                   /* Input string */
+  sqlite3_tokenizer_cursor *pCsr; /* Cursor to iterate through zInput */
+  int iRowid;                     /* Current 'rowid' value */
+  const char *zToken;             /* Current 'token' value */
+  int nToken;                     /* Size of zToken in bytes */
+  int iStart;                     /* Current 'start' value */
+  int iEnd;                       /* Current 'end' value */
+  int iPos;                       /* Current 'pos' value */
+};
 
 /*
-** Return TRUE if the word ends with three letters which
-** are consonant-vowel-consonent and where the final consonant
-** is not 'w', 'x', or 'y'.
-**
-** The word is reversed here.  So we are really checking the
-** first three letters and the first one cannot be in [wxy].
+** Query FTS for the tokenizer implementation named zName.
 */
-static int star_oh(const char *z){
-  return
-    isConsonant(z) &&
-    z[0]!='w' && z[0]!='x' && z[0]!='y' &&
-    isVowel(z+1) &&
-    isConsonant(z+2);
+static int fts3tokQueryTokenizer(
+  Fts3Hash *pHash,
+  const char *zName,
+  const sqlite3_tokenizer_module **pp,
+  char **pzErr
+){
+  sqlite3_tokenizer_module *p;
+  int nName = (int)strlen(zName);
+
+  p = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash, zName, nName+1);
+  if( !p ){
+    sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer: %s", zName);
+    return SQLITE_ERROR;
+  }
+
+  *pp = p;
+  return SQLITE_OK;
 }
 
 /*
-** If the word ends with zFrom and xCond() is true for the stem
-** of the word that preceeds the zFrom ending, then change the 
-** ending to zTo.
-**
-** The input word *pz and zFrom are both in reverse order.  zTo
-** is in normal order. 
+** The second argument, argv[], is an array of pointers to nul-terminated
+** strings. This function makes a copy of the array and strings into a 
+** single block of memory. It then dequotes any of the strings that appear
+** to be quoted.
 **
-** Return TRUE if zFrom matches.  Return FALSE if zFrom does not
-** match.  Not that TRUE is returned even if xCond() fails and
-** no substitution occurs.
+** If successful, output parameter *pazDequote is set to point at the
+** array of dequoted strings and SQLITE_OK is returned. The caller is
+** responsible for eventually calling sqlite3_free() to free the array
+** in this case. Or, if an error occurs, an SQLite error code is returned.
+** The final value of *pazDequote is undefined in this case.
 */
-static int stem(
-  char **pz,             /* The word being stemmed (Reversed) */
-  const char *zFrom,     /* If the ending matches this... (Reversed) */
-  const char *zTo,       /* ... change the ending to this (not reversed) */
-  int (*xCond)(const char*)   /* Condition that must be true */
+static int fts3tokDequoteArray(
+  int argc,                       /* Number of elements in argv[] */
+  const char * const *argv,       /* Input array */
+  char ***pazDequote              /* Output array */
 ){
-  char *z = *pz;
-  while( *zFrom && *zFrom==*z ){ z++; zFrom++; }
-  if( *zFrom!=0 ) return 0;
-  if( xCond && !xCond(z) ) return 1;
-  while( *zTo ){
-    *(--z) = *(zTo++);
-  }
-  *pz = z;
-  return 1;
-}
+  int rc = SQLITE_OK;             /* Return code */
+  if( argc==0 ){
+    *pazDequote = 0;
+  }else{
+    int i;
+    int nByte = 0;
+    char **azDequote;
 
-/*
-** This is the fallback stemmer used when the porter stemmer is
-** inappropriate.  The input word is copied into the output with
-** US-ASCII case folding.  If the input word is too long (more
-** than 20 bytes if it contains no digits or more than 6 bytes if
-** it contains digits) then word is truncated to 20 or 6 bytes
-** by taking 10 or 3 bytes from the beginning and end.
-*/
-static void copy_stemmer(const char *zIn, int nIn, char *zOut, int *pnOut){
-  int i, mx, j;
-  int hasDigit = 0;
-  for(i=0; i<nIn; i++){
-    char c = zIn[i];
-    if( c>='A' && c<='Z' ){
-      zOut[i] = c - 'A' + 'a';
-    }else{
-      if( c>='0' && c<='9' ) hasDigit = 1;
-      zOut[i] = c;
+    for(i=0; i<argc; i++){
+      nByte += (int)(strlen(argv[i]) + 1);
     }
-  }
-  mx = hasDigit ? 3 : 10;
-  if( nIn>mx*2 ){
-    for(j=mx, i=nIn-mx; i<nIn; i++, j++){
-      zOut[j] = zOut[i];
+
+    *pazDequote = azDequote = sqlite3_malloc(sizeof(char *)*argc + nByte);
+    if( azDequote==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      char *pSpace = (char *)&azDequote[argc];
+      for(i=0; i<argc; i++){
+        int n = (int)strlen(argv[i]);
+        azDequote[i] = pSpace;
+        memcpy(pSpace, argv[i], n+1);
+        sqlite3Fts3Dequote(pSpace);
+        pSpace += (n+1);
+      }
     }
-    i = j;
   }
-  zOut[i] = 0;
-  *pnOut = i;
+
+  return rc;
 }
 
+/*
+** Schema of the tokenizer table.
+*/
+#define FTS3_TOK_SCHEMA "CREATE TABLE x(input, token, start, end, position)"
 
 /*
-** Stem the input word zIn[0..nIn-1].  Store the output in zOut.
-** zOut is at least big enough to hold nIn bytes.  Write the actual
-** size of the output word (exclusive of the '\0' terminator) into *pnOut.
-**
-** Any upper-case characters in the US-ASCII character set ([A-Z])
-** are converted to lower case.  Upper-case UTF characters are
-** unchanged.
-**
-** Words that are longer than about 20 bytes are stemmed by retaining
-** a few bytes from the beginning and the end of the word.  If the
-** word contains digits, 3 bytes are taken from the beginning and
-** 3 bytes from the end.  For long words without digits, 10 bytes
-** are taken from each end.  US-ASCII case folding still applies.
-** 
-** If the input word contains not digits but does characters not 
-** in [a-zA-Z] then no stemming is attempted and this routine just 
-** copies the input into the input into the output with US-ASCII
-** case folding.
+** This function does all the work for both the xConnect and xCreate methods.
+** These tables have no persistent representation of their own, so xConnect
+** and xCreate are identical operations.
 **
-** Stemming never increases the length of the word.  So there is
-** no chance of overflowing the zOut buffer.
+**   argv[0]: module name
+**   argv[1]: database name 
+**   argv[2]: table name
+**   argv[3]: first argument (tokenizer name)
 */
-static void porter_stemmer(const char *zIn, int nIn, char *zOut, int *pnOut){
-  int i, j;
-  char zReverse[28];
-  char *z, *z2;
-  if( nIn<3 || nIn>=(int)sizeof(zReverse)-7 ){
-    /* The word is too big or too small for the porter stemmer.
-    ** Fallback to the copy stemmer */
-    copy_stemmer(zIn, nIn, zOut, pnOut);
-    return;
-  }
-  for(i=0, j=sizeof(zReverse)-6; i<nIn; i++, j--){
-    char c = zIn[i];
-    if( c>='A' && c<='Z' ){
-      zReverse[j] = c + 'a' - 'A';
-    }else if( c>='a' && c<='z' ){
-      zReverse[j] = c;
-    }else{
-      /* The use of a character not in [a-zA-Z] means that we fallback
-      ** to the copy stemmer */
-      copy_stemmer(zIn, nIn, zOut, pnOut);
-      return;
-    }
-  }
-  memset(&zReverse[sizeof(zReverse)-5], 0, 5);
-  z = &zReverse[j+1];
-
+static int fts3tokConnectMethod(
+  sqlite3 *db,                    /* Database connection */
+  void *pHash,                    /* Hash table of tokenizers */
+  int argc,                       /* Number of elements in argv array */
+  const char * const *argv,       /* xCreate/xConnect argument array */
+  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
+  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
+){
+  Fts3tokTable *pTab = 0;
+  const sqlite3_tokenizer_module *pMod = 0;
+  sqlite3_tokenizer *pTok = 0;
+  int rc;
+  char **azDequote = 0;
+  int nDequote;
 
-  /* Step 1a */
-  if( z[0]=='s' ){
-    if(
-     !stem(&z, "sess", "ss", 0) &&
-     !stem(&z, "sei", "i", 0)  &&
-     !stem(&z, "ss", "ss", 0)
-    ){
-      z++;
-    }
-  }
+  rc = sqlite3_declare_vtab(db, FTS3_TOK_SCHEMA);
+  if( rc!=SQLITE_OK ) return rc;
 
-  /* Step 1b */  
-  z2 = z;
-  if( stem(&z, "dee", "ee", m_gt_0) ){
-    /* Do nothing.  The work was all in the test */
-  }else if( 
-     (stem(&z, "gni", "", hasVowel) || stem(&z, "de", "", hasVowel))
-      && z!=z2
-  ){
-     if( stem(&z, "ta", "ate", 0) ||
-         stem(&z, "lb", "ble", 0) ||
-         stem(&z, "zi", "ize", 0) ){
-       /* Do nothing.  The work was all in the test */
-     }else if( doubleConsonant(z) && (*z!='l' && *z!='s' && *z!='z') ){
-       z++;
-     }else if( m_eq_1(z) && star_oh(z) ){
-       *(--z) = 'e';
-     }
-  }
+  nDequote = argc-3;
+  rc = fts3tokDequoteArray(nDequote, &argv[3], &azDequote);
 
-  /* Step 1c */
-  if( z[0]=='y' && hasVowel(z+1) ){
-    z[0] = 'i';
+  if( rc==SQLITE_OK ){
+    const char *zModule;
+    if( nDequote<1 ){
+      zModule = "simple";
+    }else{
+      zModule = azDequote[0];
+    }
+    rc = fts3tokQueryTokenizer((Fts3Hash*)pHash, zModule, &pMod, pzErr);
   }
 
-  /* Step 2 */
-  switch( z[1] ){
-   case 'a':
-     if( !stem(&z, "lanoita", "ate", m_gt_0) ){
-       stem(&z, "lanoit", "tion", m_gt_0);
-     }
-     break;
-   case 'c':
-     if( !stem(&z, "icne", "ence", m_gt_0) ){
-       stem(&z, "icna", "ance", m_gt_0);
-     }
-     break;
-   case 'e':
-     stem(&z, "rezi", "ize", m_gt_0);
-     break;
-   case 'g':
-     stem(&z, "igol", "log", m_gt_0);
-     break;
-   case 'l':
-     if( !stem(&z, "ilb", "ble", m_gt_0) 
-      && !stem(&z, "illa", "al", m_gt_0)
-      && !stem(&z, "iltne", "ent", m_gt_0)
-      && !stem(&z, "ile", "e", m_gt_0)
-     ){
-       stem(&z, "ilsuo", "ous", m_gt_0);
-     }
-     break;
-   case 'o':
-     if( !stem(&z, "noitazi", "ize", m_gt_0)
-      && !stem(&z, "noita", "ate", m_gt_0)
-     ){
-       stem(&z, "rota", "ate", m_gt_0);
-     }
-     break;
-   case 's':
-     if( !stem(&z, "msila", "al", m_gt_0)
-      && !stem(&z, "ssenevi", "ive", m_gt_0)
-      && !stem(&z, "ssenluf", "ful", m_gt_0)
-     ){
-       stem(&z, "ssensuo", "ous", m_gt_0);
-     }
-     break;
-   case 't':
-     if( !stem(&z, "itila", "al", m_gt_0)
-      && !stem(&z, "itivi", "ive", m_gt_0)
-     ){
-       stem(&z, "itilib", "ble", m_gt_0);
-     }
-     break;
+  assert( (rc==SQLITE_OK)==(pMod!=0) );
+  if( rc==SQLITE_OK ){
+    const char * const *azArg = (const char * const *)&azDequote[1];
+    rc = pMod->xCreate((nDequote>1 ? nDequote-1 : 0), azArg, &pTok);
   }
 
-  /* Step 3 */
-  switch( z[0] ){
-   case 'e':
-     if( !stem(&z, "etaci", "ic", m_gt_0)
-      && !stem(&z, "evita", "", m_gt_0)
-     ){
-       stem(&z, "ezila", "al", m_gt_0);
-     }
-     break;
-   case 'i':
-     stem(&z, "itici", "ic", m_gt_0);
-     break;
-   case 'l':
-     if( !stem(&z, "laci", "ic", m_gt_0) ){
-       stem(&z, "luf", "", m_gt_0);
-     }
-     break;
-   case 's':
-     stem(&z, "ssen", "", m_gt_0);
-     break;
+  if( rc==SQLITE_OK ){
+    pTab = (Fts3tokTable *)sqlite3_malloc(sizeof(Fts3tokTable));
+    if( pTab==0 ){
+      rc = SQLITE_NOMEM;
+    }
   }
 
-  /* Step 4 */
-  switch( z[1] ){
-   case 'a':
-     if( z[0]=='l' && m_gt_1(z+2) ){
-       z += 2;
-     }
-     break;
-   case 'c':
-     if( z[0]=='e' && z[2]=='n' && (z[3]=='a' || z[3]=='e')  && m_gt_1(z+4)  ){
-       z += 4;
-     }
-     break;
-   case 'e':
-     if( z[0]=='r' && m_gt_1(z+2) ){
-       z += 2;
-     }
-     break;
-   case 'i':
-     if( z[0]=='c' && m_gt_1(z+2) ){
-       z += 2;
-     }
-     break;
-   case 'l':
-     if( z[0]=='e' && z[2]=='b' && (z[3]=='a' || z[3]=='i') && m_gt_1(z+4) ){
-       z += 4;
-     }
-     break;
-   case 'n':
-     if( z[0]=='t' ){
-       if( z[2]=='a' ){
-         if( m_gt_1(z+3) ){
-           z += 3;
-         }
-       }else if( z[2]=='e' ){
-         if( !stem(&z, "tneme", "", m_gt_1)
-          && !stem(&z, "tnem", "", m_gt_1)
-         ){
-           stem(&z, "tne", "", m_gt_1);
-         }
-       }
-     }
-     break;
-   case 'o':
-     if( z[0]=='u' ){
-       if( m_gt_1(z+2) ){
-         z += 2;
-       }
-     }else if( z[3]=='s' || z[3]=='t' ){
-       stem(&z, "noi", "", m_gt_1);
-     }
-     break;
-   case 's':
-     if( z[0]=='m' && z[2]=='i' && m_gt_1(z+3) ){
-       z += 3;
-     }
-     break;
-   case 't':
-     if( !stem(&z, "eta", "", m_gt_1) ){
-       stem(&z, "iti", "", m_gt_1);
-     }
-     break;
-   case 'u':
-     if( z[0]=='s' && z[2]=='o' && m_gt_1(z+3) ){
-       z += 3;
-     }
-     break;
-   case 'v':
-   case 'z':
-     if( z[0]=='e' && z[2]=='i' && m_gt_1(z+3) ){
-       z += 3;
-     }
-     break;
+  if( rc==SQLITE_OK ){
+    memset(pTab, 0, sizeof(Fts3tokTable));
+    pTab->pMod = pMod;
+    pTab->pTok = pTok;
+    *ppVtab = &pTab->base;
+  }else{
+    if( pTok ){
+      pMod->xDestroy(pTok);
+    }
   }
 
-  /* Step 5a */
-  if( z[0]=='e' ){
-    if( m_gt_1(z+1) ){
-      z++;
-    }else if( m_eq_1(z+1) && !star_oh(z+1) ){
-      z++;
+  sqlite3_free(azDequote);
+  return rc;
+}
+
+/*
+** This function does the work for both the xDisconnect and xDestroy methods.
+** These tables have no persistent representation of their own, so xDisconnect
+** and xDestroy are identical operations.
+*/
+static int fts3tokDisconnectMethod(sqlite3_vtab *pVtab){
+  Fts3tokTable *pTab = (Fts3tokTable *)pVtab;
+
+  pTab->pMod->xDestroy(pTab->pTok);
+  sqlite3_free(pTab);
+  return SQLITE_OK;
+}
+
+/*
+** xBestIndex - Analyze a WHERE and ORDER BY clause.
+*/
+static int fts3tokBestIndexMethod(
+  sqlite3_vtab *pVTab, 
+  sqlite3_index_info *pInfo
+){
+  int i;
+  UNUSED_PARAMETER(pVTab);
+
+  for(i=0; i<pInfo->nConstraint; i++){
+    if( pInfo->aConstraint[i].usable 
+     && pInfo->aConstraint[i].iColumn==0 
+     && pInfo->aConstraint[i].op==SQLITE_INDEX_CONSTRAINT_EQ 
+    ){
+      pInfo->idxNum = 1;
+      pInfo->aConstraintUsage[i].argvIndex = 1;
+      pInfo->aConstraintUsage[i].omit = 1;
+      pInfo->estimatedCost = 1;
+      return SQLITE_OK;
     }
   }
 
-  /* Step 5b */
-  if( m_gt_1(z) && z[0]=='l' && z[1]=='l' ){
-    z++;
+  pInfo->idxNum = 0;
+  assert( pInfo->estimatedCost>1000000.0 );
+
+  return SQLITE_OK;
+}
+
+/*
+** xOpen - Open a cursor.
+*/
+static int fts3tokOpenMethod(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCsr){
+  Fts3tokCursor *pCsr;
+  UNUSED_PARAMETER(pVTab);
+
+  pCsr = (Fts3tokCursor *)sqlite3_malloc(sizeof(Fts3tokCursor));
+  if( pCsr==0 ){
+    return SQLITE_NOMEM;
   }
+  memset(pCsr, 0, sizeof(Fts3tokCursor));
 
-  /* z[] is now the stemmed word in reverse order.  Flip it back
-  ** around into forward order and return.
-  */
-  *pnOut = i = (int)strlen(z);
-  zOut[i] = 0;
-  while( *z ){
-    zOut[--i] = *(z++);
+  *ppCsr = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+/*
+** Reset the tokenizer cursor passed as the only argument. As if it had
+** just been returned by fts3tokOpenMethod().
+*/
+static void fts3tokResetCursor(Fts3tokCursor *pCsr){
+  if( pCsr->pCsr ){
+    Fts3tokTable *pTab = (Fts3tokTable *)(pCsr->base.pVtab);
+    pTab->pMod->xClose(pCsr->pCsr);
+    pCsr->pCsr = 0;
   }
+  sqlite3_free(pCsr->zInput);
+  pCsr->zInput = 0;
+  pCsr->zToken = 0;
+  pCsr->nToken = 0;
+  pCsr->iStart = 0;
+  pCsr->iEnd = 0;
+  pCsr->iPos = 0;
+  pCsr->iRowid = 0;
 }
 
 /*
-** Characters that can be part of a token.  We assume any character
-** whose value is greater than 0x80 (any UTF character) can be
-** part of a token.  In other words, delimiters all must have
-** values of 0x7f or lower.
+** xClose - Close a cursor.
 */
-static const char porterIdChar[] = {
-/* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
-    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 3x */
-    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 4x */
-    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,  /* 5x */
-    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 6x */
-    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,  /* 7x */
-};
-#define isDelim(C) (((ch=C)&0x80)==0 && (ch<0x30 || !porterIdChar[ch-0x30]))
+static int fts3tokCloseMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+
+  fts3tokResetCursor(pCsr);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
 
 /*
-** Extract the next token from a tokenization cursor.  The cursor must
-** have been opened by a prior call to porterOpen().
+** xNext - Advance the cursor to the next row, if any.
 */
-static int porterNext(
-  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by porterOpen */
-  const char **pzToken,               /* OUT: *pzToken is the token text */
-  int *pnBytes,                       /* OUT: Number of bytes in token */
-  int *piStartOffset,                 /* OUT: Starting offset of token */
-  int *piEndOffset,                   /* OUT: Ending offset of token */
-  int *piPosition                     /* OUT: Position integer of token */
-){
-  porter_tokenizer_cursor *c = (porter_tokenizer_cursor *) pCursor;
-  const char *z = c->zInput;
+static int fts3tokNextMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  Fts3tokTable *pTab = (Fts3tokTable *)(pCursor->pVtab);
+  int rc;                         /* Return code */
 
-  while( c->iOffset<c->nInput ){
-    int iStartOffset, ch;
+  pCsr->iRowid++;
+  rc = pTab->pMod->xNext(pCsr->pCsr,
+      &pCsr->zToken, &pCsr->nToken,
+      &pCsr->iStart, &pCsr->iEnd, &pCsr->iPos
+  );
 
-    /* Scan past delimiter characters */
-    while( c->iOffset<c->nInput && isDelim(z[c->iOffset]) ){
-      c->iOffset++;
-    }
+  if( rc!=SQLITE_OK ){
+    fts3tokResetCursor(pCsr);
+    if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+  }
 
-    /* Count non-delimiter characters. */
-    iStartOffset = c->iOffset;
-    while( c->iOffset<c->nInput && !isDelim(z[c->iOffset]) ){
-      c->iOffset++;
-    }
+  return rc;
+}
 
-    if( c->iOffset>iStartOffset ){
-      int n = c->iOffset-iStartOffset;
-      if( n>c->nAllocated ){
-        char *pNew;
-        c->nAllocated = n+20;
-        pNew = sqlite3_realloc(c->zToken, c->nAllocated);
-        if( !pNew ) return SQLITE_NOMEM;
-        c->zToken = pNew;
+/*
+** xFilter - Initialize a cursor to point at the start of its data.
+*/
+static int fts3tokFilterMethod(
+  sqlite3_vtab_cursor *pCursor,   /* The cursor used for this query */
+  int idxNum,                     /* Strategy index */
+  const char *idxStr,             /* Unused */
+  int nVal,                       /* Number of elements in apVal */
+  sqlite3_value **apVal           /* Arguments for the indexing scheme */
+){
+  int rc = SQLITE_ERROR;
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  Fts3tokTable *pTab = (Fts3tokTable *)(pCursor->pVtab);
+  UNUSED_PARAMETER(idxStr);
+  UNUSED_PARAMETER(nVal);
+
+  fts3tokResetCursor(pCsr);
+  if( idxNum==1 ){
+    const char *zByte = (const char *)sqlite3_value_text(apVal[0]);
+    int nByte = sqlite3_value_bytes(apVal[0]);
+    pCsr->zInput = sqlite3_malloc(nByte+1);
+    if( pCsr->zInput==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memcpy(pCsr->zInput, zByte, nByte);
+      pCsr->zInput[nByte] = 0;
+      rc = pTab->pMod->xOpen(pTab->pTok, pCsr->zInput, nByte, &pCsr->pCsr);
+      if( rc==SQLITE_OK ){
+        pCsr->pCsr->pTokenizer = pTab->pTok;
       }
-      porter_stemmer(&z[iStartOffset], n, c->zToken, pnBytes);
-      *pzToken = c->zToken;
-      *piStartOffset = iStartOffset;
-      *piEndOffset = c->iOffset;
-      *piPosition = c->iToken++;
-      return SQLITE_OK;
     }
   }
-  return SQLITE_DONE;
+
+  if( rc!=SQLITE_OK ) return rc;
+  return fts3tokNextMethod(pCursor);
 }
 
 /*
-** The set of routines that implement the porter-stemmer tokenizer
+** xEof - Return true if the cursor is at EOF, or false otherwise.
 */
-static const sqlite3_tokenizer_module porterTokenizerModule = {
-  0,
-  porterCreate,
-  porterDestroy,
-  porterOpen,
-  porterClose,
-  porterNext,
-  0
-};
+static int fts3tokEofMethod(sqlite3_vtab_cursor *pCursor){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  return (pCsr->zToken==0);
+}
 
 /*
-** Allocate a new porter tokenizer.  Return a pointer to the new
-** tokenizer in *ppModule
+** xColumn - Return a column value.
 */
-SQLITE_PRIVATE void sqlite3Fts3PorterTokenizerModule(
-  sqlite3_tokenizer_module const**ppModule
+static int fts3tokColumnMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite3_context *pCtx,          /* Context for sqlite3_result_xxx() calls */
+  int iCol                        /* Index of column to read value from */
 ){
-  *ppModule = &porterTokenizerModule;
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+
+  /* CREATE TABLE x(input, token, start, end, position) */
+  switch( iCol ){
+    case 0:
+      sqlite3_result_text(pCtx, pCsr->zInput, -1, SQLITE_TRANSIENT);
+      break;
+    case 1:
+      sqlite3_result_text(pCtx, pCsr->zToken, pCsr->nToken, SQLITE_TRANSIENT);
+      break;
+    case 2:
+      sqlite3_result_int(pCtx, pCsr->iStart);
+      break;
+    case 3:
+      sqlite3_result_int(pCtx, pCsr->iEnd);
+      break;
+    default:
+      assert( iCol==4 );
+      sqlite3_result_int(pCtx, pCsr->iPos);
+      break;
+  }
+  return SQLITE_OK;
+}
+
+/*
+** xRowid - Return the current rowid for the cursor.
+*/
+static int fts3tokRowidMethod(
+  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
+  sqlite_int64 *pRowid            /* OUT: Rowid value */
+){
+  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  *pRowid = (sqlite3_int64)pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+/*
+** Register the fts3tok module with database connection db. Return SQLITE_OK
+** if successful or an error code if sqlite3_create_module() fails.
+*/
+SQLITE_PRIVATE int sqlite3Fts3InitTok(sqlite3 *db, Fts3Hash *pHash){
+  static const sqlite3_module fts3tok_module = {
+     0,                           /* iVersion      */
+     fts3tokConnectMethod,        /* xCreate       */
+     fts3tokConnectMethod,        /* xConnect      */
+     fts3tokBestIndexMethod,      /* xBestIndex    */
+     fts3tokDisconnectMethod,     /* xDisconnect   */
+     fts3tokDisconnectMethod,     /* xDestroy      */
+     fts3tokOpenMethod,           /* xOpen         */
+     fts3tokCloseMethod,          /* xClose        */
+     fts3tokFilterMethod,         /* xFilter       */
+     fts3tokNextMethod,           /* xNext         */
+     fts3tokEofMethod,            /* xEof          */
+     fts3tokColumnMethod,         /* xColumn       */
+     fts3tokRowidMethod,          /* xRowid        */
+     0,                           /* xUpdate       */
+     0,                           /* xBegin        */
+     0,                           /* xSync         */
+     0,                           /* xCommit       */
+     0,                           /* xRollback     */
+     0,                           /* xFindFunction */
+     0,                           /* xRename       */
+     0,                           /* xSavepoint    */
+     0,                           /* xRelease      */
+     0                            /* xRollbackTo   */
+  };
+  int rc;                         /* Return code */
+
+  rc = sqlite3_create_module(db, "fts3tokenize", &fts3tok_module, (void*)pHash);
+  return rc;
 }
 
 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
 
-/************** End of fts3_porter.c *****************************************/
-/************** Begin file fts3_tokenizer.c **********************************/
+/************** End of fts3_tokenize_vtab.c **********************************/
+/************** Begin file fts3_write.c **************************************/
 /*
-** 2007 June 22
+** 2009 Oct 23
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
@@ -141782,860 +144463,1147 @@ SQLITE_PRIVATE void sqlite3Fts3PorterTokenizerModule(
 **
 ******************************************************************************
 **
-** This is part of an SQLite module implementing full-text search.
-** This particular file implements the generic tokenizer interface.
+** This file is part of the SQLite FTS3 extension module. Specifically,
+** this file contains code to insert, update and delete rows from FTS3
+** tables. It also contains code to merge FTS3 b-tree segments. Some
+** of the sub-routines used to merge segments are also used by the query 
+** code in fts3.c.
 */
 
-/*
-** The code in this file is only compiled if:
-**
-**     * The FTS3 module is being built as an extension
-**       (in which case SQLITE_CORE is not defined), or
-**
-**     * The FTS3 module is being built into the core of
-**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
-*/
+/* #include "fts3Int.h" */
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
-/* #include <assert.h> */
 /* #include <string.h> */
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+
+
+#define FTS_MAX_APPENDABLE_HEIGHT 16
 
 /*
-** Implementation of the SQL scalar function for accessing the underlying 
-** hash table. This function may be called as follows:
-**
-**   SELECT <function-name>(<key-name>);
-**   SELECT <function-name>(<key-name>, <pointer>);
+** When full-text index nodes are loaded from disk, the buffer that they
+** are loaded into has the following number of bytes of padding at the end 
+** of it. i.e. if a full-text index node is 900 bytes in size, then a buffer
+** of 920 bytes is allocated for it.
 **
-** where <function-name> is the name passed as the second argument
-** to the sqlite3Fts3InitHashTable() function (e.g. 'fts3_tokenizer').
+** This means that if we have a pointer into a buffer containing node data,
+** it is always safe to read up to two varints from it without risking an
+** overread, even if the node data is corrupted.
+*/
+#define FTS3_NODE_PADDING (FTS3_VARINT_MAX*2)
+
+/*
+** Under certain circumstances, b-tree nodes (doclists) can be loaded into
+** memory incrementally instead of all at once. This can be a big performance
+** win (reduced IO and CPU) if SQLite stops calling the virtual table xNext()
+** method before retrieving all query results (as may happen, for example,
+** if a query has a LIMIT clause).
 **
-** If the <pointer> argument is specified, it must be a blob value
-** containing a pointer to be stored as the hash data corresponding
-** to the string <key-name>. If <pointer> is not specified, then
-** the string <key-name> must already exist in the has table. Otherwise,
-** an error is returned.
+** Incremental loading is used for b-tree nodes FTS3_NODE_CHUNK_THRESHOLD 
+** bytes and larger. Nodes are loaded in chunks of FTS3_NODE_CHUNKSIZE bytes.
+** The code is written so that the hard lower-limit for each of these values 
+** is 1. Clearly such small values would be inefficient, but can be useful 
+** for testing purposes.
 **
-** Whether or not the <pointer> argument is specified, the value returned
-** is a blob containing the pointer stored as the hash data corresponding
-** to string <key-name> (after the hash-table is updated, if applicable).
+** If this module is built with SQLITE_TEST defined, these constants may
+** be overridden at runtime for testing purposes. File fts3_test.c contains
+** a Tcl interface to read and write the values.
 */
-static void scalarFunc(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
-){
-  Fts3Hash *pHash;
-  void *pPtr = 0;
-  const unsigned char *zName;
-  int nName;
-
-  assert( argc==1 || argc==2 );
-
-  pHash = (Fts3Hash *)sqlite3_user_data(context);
-
-  zName = sqlite3_value_text(argv[0]);
-  nName = sqlite3_value_bytes(argv[0])+1;
-
-  if( argc==2 ){
-    void *pOld;
-    int n = sqlite3_value_bytes(argv[1]);
-    if( zName==0 || n!=sizeof(pPtr) ){
-      sqlite3_result_error(context, "argument type mismatch", -1);
-      return;
-    }
-    pPtr = *(void **)sqlite3_value_blob(argv[1]);
-    pOld = sqlite3Fts3HashInsert(pHash, (void *)zName, nName, pPtr);
-    if( pOld==pPtr ){
-      sqlite3_result_error(context, "out of memory", -1);
-      return;
-    }
-  }else{
-    if( zName ){
-      pPtr = sqlite3Fts3HashFind(pHash, zName, nName);
-    }
-    if( !pPtr ){
-      char *zErr = sqlite3_mprintf("unknown tokenizer: %s", zName);
-      sqlite3_result_error(context, zErr, -1);
-      sqlite3_free(zErr);
-      return;
-    }
-  }
+#ifdef SQLITE_TEST
+int test_fts3_node_chunksize = (4*1024);
+int test_fts3_node_chunk_threshold = (4*1024)*4;
+# define FTS3_NODE_CHUNKSIZE       test_fts3_node_chunksize
+# define FTS3_NODE_CHUNK_THRESHOLD test_fts3_node_chunk_threshold
+#else
+# define FTS3_NODE_CHUNKSIZE (4*1024) 
+# define FTS3_NODE_CHUNK_THRESHOLD (FTS3_NODE_CHUNKSIZE*4)
+#endif
 
-  sqlite3_result_blob(context, (void *)&pPtr, sizeof(pPtr), SQLITE_TRANSIENT);
-}
+/*
+** The two values that may be meaningfully bound to the :1 parameter in
+** statements SQL_REPLACE_STAT and SQL_SELECT_STAT.
+*/
+#define FTS_STAT_DOCTOTAL      0
+#define FTS_STAT_INCRMERGEHINT 1
+#define FTS_STAT_AUTOINCRMERGE 2
 
-SQLITE_PRIVATE int sqlite3Fts3IsIdChar(char c){
-  static const char isFtsIdChar[] = {
-      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 0x */
-      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 1x */
-      0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /* 2x */
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,  /* 3x */
-      0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 4x */
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1,  /* 5x */
-      0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 6x */
-      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0,  /* 7x */
-  };
-  return (c&0x80 || isFtsIdChar[(int)(c)]);
+/*
+** If FTS_LOG_MERGES is defined, call sqlite3_log() to report each automatic
+** and incremental merge operation that takes place. This is used for 
+** debugging FTS only, it should not usually be turned on in production
+** systems.
+*/
+#ifdef FTS3_LOG_MERGES
+static void fts3LogMerge(int nMerge, sqlite3_int64 iAbsLevel){
+  sqlite3_log(SQLITE_OK, "%d-way merge from level %d", nMerge, (int)iAbsLevel);
 }
+#else
+#define fts3LogMerge(x, y)
+#endif
 
-SQLITE_PRIVATE const char *sqlite3Fts3NextToken(const char *zStr, int *pn){
-  const char *z1;
-  const char *z2 = 0;
 
-  /* Find the start of the next token. */
-  z1 = zStr;
-  while( z2==0 ){
-    char c = *z1;
-    switch( c ){
-      case '\0': return 0;        /* No more tokens here */
-      case '\'':
-      case '"':
-      case '`': {
-        z2 = z1;
-        while( *++z2 && (*z2!=c || *++z2==c) );
-        break;
-      }
-      case '[':
-        z2 = &z1[1];
-        while( *z2 && z2[0]!=']' ) z2++;
-        if( *z2 ) z2++;
-        break;
+typedef struct PendingList PendingList;
+typedef struct SegmentNode SegmentNode;
+typedef struct SegmentWriter SegmentWriter;
 
-      default:
-        if( sqlite3Fts3IsIdChar(*z1) ){
-          z2 = &z1[1];
-          while( sqlite3Fts3IsIdChar(*z2) ) z2++;
-        }else{
-          z1++;
-        }
-    }
-  }
+/*
+** An instance of the following data structure is used to build doclists
+** incrementally. See function fts3PendingListAppend() for details.
+*/
+struct PendingList {
+  int nData;
+  char *aData;
+  int nSpace;
+  sqlite3_int64 iLastDocid;
+  sqlite3_int64 iLastCol;
+  sqlite3_int64 iLastPos;
+};
 
-  *pn = (int)(z2-z1);
-  return z1;
-}
 
-SQLITE_PRIVATE int sqlite3Fts3InitTokenizer(
-  Fts3Hash *pHash,                /* Tokenizer hash table */
-  const char *zArg,               /* Tokenizer name */
-  sqlite3_tokenizer **ppTok,      /* OUT: Tokenizer (if applicable) */
-  char **pzErr                    /* OUT: Set to malloced error message */
-){
-  int rc;
-  char *z = (char *)zArg;
-  int n = 0;
-  char *zCopy;
-  char *zEnd;                     /* Pointer to nul-term of zCopy */
-  sqlite3_tokenizer_module *m;
+/*
+** Each cursor has a (possibly empty) linked list of the following objects.
+*/
+struct Fts3DeferredToken {
+  Fts3PhraseToken *pToken;        /* Pointer to corresponding expr token */
+  int iCol;                       /* Column token must occur in */
+  Fts3DeferredToken *pNext;       /* Next in list of deferred tokens */
+  PendingList *pList;             /* Doclist is assembled here */
+};
 
-  zCopy = sqlite3_mprintf("%s", zArg);
-  if( !zCopy ) return SQLITE_NOMEM;
-  zEnd = &zCopy[strlen(zCopy)];
+/*
+** An instance of this structure is used to iterate through the terms on
+** a contiguous set of segment b-tree leaf nodes. Although the details of
+** this structure are only manipulated by code in this file, opaque handles
+** of type Fts3SegReader* are also used by code in fts3.c to iterate through
+** terms when querying the full-text index. See functions:
+**
+**   sqlite3Fts3SegReaderNew()
+**   sqlite3Fts3SegReaderFree()
+**   sqlite3Fts3SegReaderIterate()
+**
+** Methods used to manipulate Fts3SegReader structures:
+**
+**   fts3SegReaderNext()
+**   fts3SegReaderFirstDocid()
+**   fts3SegReaderNextDocid()
+*/
+struct Fts3SegReader {
+  int iIdx;                       /* Index within level, or 0x7FFFFFFF for PT */
+  u8 bLookup;                     /* True for a lookup only */
+  u8 rootOnly;                    /* True for a root-only reader */
 
-  z = (char *)sqlite3Fts3NextToken(zCopy, &n);
-  if( z==0 ){
-    assert( n==0 );
-    z = zCopy;
-  }
-  z[n] = '\0';
-  sqlite3Fts3Dequote(z);
+  sqlite3_int64 iStartBlock;      /* Rowid of first leaf block to traverse */
+  sqlite3_int64 iLeafEndBlock;    /* Rowid of final leaf block to traverse */
+  sqlite3_int64 iEndBlock;        /* Rowid of final block in segment (or 0) */
+  sqlite3_int64 iCurrentBlock;    /* Current leaf block (or 0) */
 
-  m = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash,z,(int)strlen(z)+1);
-  if( !m ){
-    sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer: %s", z);
-    rc = SQLITE_ERROR;
-  }else{
-    char const **aArg = 0;
-    int iArg = 0;
-    z = &z[n+1];
-    while( z<zEnd && (NULL!=(z = (char *)sqlite3Fts3NextToken(z, &n))) ){
-      int nNew = sizeof(char *)*(iArg+1);
-      char const **aNew = (const char **)sqlite3_realloc((void *)aArg, nNew);
-      if( !aNew ){
-        sqlite3_free(zCopy);
-        sqlite3_free((void *)aArg);
-        return SQLITE_NOMEM;
-      }
-      aArg = aNew;
-      aArg[iArg++] = z;
-      z[n] = '\0';
-      sqlite3Fts3Dequote(z);
-      z = &z[n+1];
-    }
-    rc = m->xCreate(iArg, aArg, ppTok);
-    assert( rc!=SQLITE_OK || *ppTok );
-    if( rc!=SQLITE_OK ){
-      sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer");
-    }else{
-      (*ppTok)->pModule = m; 
-    }
-    sqlite3_free((void *)aArg);
-  }
+  char *aNode;                    /* Pointer to node data (or NULL) */
+  int nNode;                      /* Size of buffer at aNode (or 0) */
+  int nPopulate;                  /* If >0, bytes of buffer aNode[] loaded */
+  sqlite3_blob *pBlob;            /* If not NULL, blob handle to read node */
 
-  sqlite3_free(zCopy);
-  return rc;
-}
+  Fts3HashElem **ppNextElem;
 
+  /* Variables set by fts3SegReaderNext(). These may be read directly
+  ** by the caller. They are valid from the time SegmentReaderNew() returns
+  ** until SegmentReaderNext() returns something other than SQLITE_OK
+  ** (i.e. SQLITE_DONE).
+  */
+  int nTerm;                      /* Number of bytes in current term */
+  char *zTerm;                    /* Pointer to current term */
+  int nTermAlloc;                 /* Allocated size of zTerm buffer */
+  char *aDoclist;                 /* Pointer to doclist of current entry */
+  int nDoclist;                   /* Size of doclist in current entry */
 
-#ifdef SQLITE_TEST
+  /* The following variables are used by fts3SegReaderNextDocid() to iterate 
+  ** through the current doclist (aDoclist/nDoclist).
+  */
+  char *pOffsetList;
+  int nOffsetList;                /* For descending pending seg-readers only */
+  sqlite3_int64 iDocid;
+};
 
-#include <tcl.h>
-/* #include <string.h> */
+#define fts3SegReaderIsPending(p) ((p)->ppNextElem!=0)
+#define fts3SegReaderIsRootOnly(p) ((p)->rootOnly!=0)
 
 /*
-** Implementation of a special SQL scalar function for testing tokenizers 
-** designed to be used in concert with the Tcl testing framework. This
-** function must be called with two or more arguments:
-**
-**   SELECT <function-name>(<key-name>, ..., <input-string>);
-**
-** where <function-name> is the name passed as the second argument
-** to the sqlite3Fts3InitHashTable() function (e.g. 'fts3_tokenizer')
-** concatenated with the string '_test' (e.g. 'fts3_tokenizer_test').
+** An instance of this structure is used to create a segment b-tree in the
+** database. The internal details of this type are only accessed by the
+** following functions:
 **
-** The return value is a string that may be interpreted as a Tcl
-** list. For each token in the <input-string>, three elements are
-** added to the returned list. The first is the token position, the 
-** second is the token text (folded, stemmed, etc.) and the third is the
-** substring of <input-string> associated with the token. For example, 
-** using the built-in "simple" tokenizer:
+**   fts3SegWriterAdd()
+**   fts3SegWriterFlush()
+**   fts3SegWriterFree()
+*/
+struct SegmentWriter {
+  SegmentNode *pTree;             /* Pointer to interior tree structure */
+  sqlite3_int64 iFirst;           /* First slot in %_segments written */
+  sqlite3_int64 iFree;            /* Next free slot in %_segments */
+  char *zTerm;                    /* Pointer to previous term buffer */
+  int nTerm;                      /* Number of bytes in zTerm */
+  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
+  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
+  int nSize;                      /* Size of allocation at aData */
+  int nData;                      /* Bytes of data in aData */
+  char *aData;                    /* Pointer to block from malloc() */
+  i64 nLeafData;                  /* Number of bytes of leaf data written */
+};
+
+/*
+** Type SegmentNode is used by the following three functions to create
+** the interior part of the segment b+-tree structures (everything except
+** the leaf nodes). These functions and type are only ever used by code
+** within the fts3SegWriterXXX() family of functions described above.
 **
-**   SELECT fts_tokenizer_test('simple', 'I don't see how');
+**   fts3NodeAddTerm()
+**   fts3NodeWrite()
+**   fts3NodeFree()
 **
-** will return the string:
+** When a b+tree is written to the database (either as a result of a merge
+** or the pending-terms table being flushed), leaves are written into the 
+** database file as soon as they are completely populated. The interior of
+** the tree is assembled in memory and written out only once all leaves have
+** been populated and stored. This is Ok, as the b+-tree fanout is usually
+** very large, meaning that the interior of the tree consumes relatively 
+** little memory.
+*/
+struct SegmentNode {
+  SegmentNode *pParent;           /* Parent node (or NULL for root node) */
+  SegmentNode *pRight;            /* Pointer to right-sibling */
+  SegmentNode *pLeftmost;         /* Pointer to left-most node of this depth */
+  int nEntry;                     /* Number of terms written to node so far */
+  char *zTerm;                    /* Pointer to previous term buffer */
+  int nTerm;                      /* Number of bytes in zTerm */
+  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
+  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
+  int nData;                      /* Bytes of valid data so far */
+  char *aData;                    /* Node data */
+};
+
+/*
+** Valid values for the second argument to fts3SqlStmt().
+*/
+#define SQL_DELETE_CONTENT             0
+#define SQL_IS_EMPTY                   1
+#define SQL_DELETE_ALL_CONTENT         2 
+#define SQL_DELETE_ALL_SEGMENTS        3
+#define SQL_DELETE_ALL_SEGDIR          4
+#define SQL_DELETE_ALL_DOCSIZE         5
+#define SQL_DELETE_ALL_STAT            6
+#define SQL_SELECT_CONTENT_BY_ROWID    7
+#define SQL_NEXT_SEGMENT_INDEX         8
+#define SQL_INSERT_SEGMENTS            9
+#define SQL_NEXT_SEGMENTS_ID          10
+#define SQL_INSERT_SEGDIR             11
+#define SQL_SELECT_LEVEL              12
+#define SQL_SELECT_LEVEL_RANGE        13
+#define SQL_SELECT_LEVEL_COUNT        14
+#define SQL_SELECT_SEGDIR_MAX_LEVEL   15
+#define SQL_DELETE_SEGDIR_LEVEL       16
+#define SQL_DELETE_SEGMENTS_RANGE     17
+#define SQL_CONTENT_INSERT            18
+#define SQL_DELETE_DOCSIZE            19
+#define SQL_REPLACE_DOCSIZE           20
+#define SQL_SELECT_DOCSIZE            21
+#define SQL_SELECT_STAT               22
+#define SQL_REPLACE_STAT              23
+
+#define SQL_SELECT_ALL_PREFIX_LEVEL   24
+#define SQL_DELETE_ALL_TERMS_SEGDIR   25
+#define SQL_DELETE_SEGDIR_RANGE       26
+#define SQL_SELECT_ALL_LANGID         27
+#define SQL_FIND_MERGE_LEVEL          28
+#define SQL_MAX_LEAF_NODE_ESTIMATE    29
+#define SQL_DELETE_SEGDIR_ENTRY       30
+#define SQL_SHIFT_SEGDIR_ENTRY        31
+#define SQL_SELECT_SEGDIR             32
+#define SQL_CHOMP_SEGDIR              33
+#define SQL_SEGMENT_IS_APPENDABLE     34
+#define SQL_SELECT_INDEXES            35
+#define SQL_SELECT_MXLEVEL            36
+
+#define SQL_SELECT_LEVEL_RANGE2       37
+#define SQL_UPDATE_LEVEL_IDX          38
+#define SQL_UPDATE_LEVEL              39
+
+/*
+** This function is used to obtain an SQLite prepared statement handle
+** for the statement identified by the second argument. If successful,
+** *pp is set to the requested statement handle and SQLITE_OK returned.
+** Otherwise, an SQLite error code is returned and *pp is set to 0.
 **
-**   "{0 i I 1 dont don't 2 see see 3 how how}"
-**   
+** If argument apVal is not NULL, then it must point to an array with
+** at least as many entries as the requested statement has bound 
+** parameters. The values are bound to the statements parameters before
+** returning.
 */
-static void testFunc(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
+static int fts3SqlStmt(
+  Fts3Table *p,                   /* Virtual table handle */
+  int eStmt,                      /* One of the SQL_XXX constants above */
+  sqlite3_stmt **pp,              /* OUT: Statement handle */
+  sqlite3_value **apVal           /* Values to bind to statement */
 ){
-  Fts3Hash *pHash;
-  sqlite3_tokenizer_module *p;
-  sqlite3_tokenizer *pTokenizer = 0;
-  sqlite3_tokenizer_cursor *pCsr = 0;
+  const char *azSql[] = {
+/* 0  */  "DELETE FROM %Q.'%q_content' WHERE rowid = ?",
+/* 1  */  "SELECT NOT EXISTS(SELECT docid FROM %Q.'%q_content' WHERE rowid!=?)",
+/* 2  */  "DELETE FROM %Q.'%q_content'",
+/* 3  */  "DELETE FROM %Q.'%q_segments'",
+/* 4  */  "DELETE FROM %Q.'%q_segdir'",
+/* 5  */  "DELETE FROM %Q.'%q_docsize'",
+/* 6  */  "DELETE FROM %Q.'%q_stat'",
+/* 7  */  "SELECT %s WHERE rowid=?",
+/* 8  */  "SELECT (SELECT max(idx) FROM %Q.'%q_segdir' WHERE level = ?) + 1",
+/* 9  */  "REPLACE INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
+/* 10 */  "SELECT coalesce((SELECT max(blockid) FROM %Q.'%q_segments') + 1, 1)",
+/* 11 */  "REPLACE INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
 
-  const char *zErr = 0;
+          /* Return segments in order from oldest to newest.*/ 
+/* 12 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+            "FROM %Q.'%q_segdir' WHERE level = ? ORDER BY idx ASC",
+/* 13 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?"
+            "ORDER BY level DESC, idx ASC",
 
-  const char *zName;
-  int nName;
-  const char *zInput;
-  int nInput;
+/* 14 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
+/* 15 */  "SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?",
 
-  const char *azArg[64];
+/* 16 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
+/* 17 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
+/* 18 */  "INSERT INTO %Q.'%q_content' VALUES(%s)",
+/* 19 */  "DELETE FROM %Q.'%q_docsize' WHERE docid = ?",
+/* 20 */  "REPLACE INTO %Q.'%q_docsize' VALUES(?,?)",
+/* 21 */  "SELECT size FROM %Q.'%q_docsize' WHERE docid=?",
+/* 22 */  "SELECT value FROM %Q.'%q_stat' WHERE id=?",
+/* 23 */  "REPLACE INTO %Q.'%q_stat' VALUES(?,?)",
+/* 24 */  "",
+/* 25 */  "",
 
-  const char *zToken;
-  int nToken = 0;
-  int iStart = 0;
-  int iEnd = 0;
-  int iPos = 0;
-  int i;
+/* 26 */ "DELETE FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?",
+/* 27 */ "SELECT ? UNION SELECT level / (1024 * ?) FROM %Q.'%q_segdir'",
 
-  Tcl_Obj *pRet;
+/* This statement is used to determine which level to read the input from
+** when performing an incremental merge. It returns the absolute level number
+** of the oldest level in the db that contains at least ? segments. Or,
+** if no level in the FTS index contains more than ? segments, the statement
+** returns zero rows.  */
+/* 28 */ "SELECT level FROM %Q.'%q_segdir' GROUP BY level HAVING count(*)>=?"
+         "  ORDER BY (level %% 1024) ASC LIMIT 1",
 
-  if( argc<2 ){
-    sqlite3_result_error(context, "insufficient arguments", -1);
-    return;
-  }
+/* Estimate the upper limit on the number of leaf nodes in a new segment
+** created by merging the oldest :2 segments from absolute level :1. See 
+** function sqlite3Fts3Incrmerge() for details.  */
+/* 29 */ "SELECT 2 * total(1 + leaves_end_block - start_block) "
+         "  FROM %Q.'%q_segdir' WHERE level = ? AND idx < ?",
 
-  nName = sqlite3_value_bytes(argv[0]);
-  zName = (const char *)sqlite3_value_text(argv[0]);
-  nInput = sqlite3_value_bytes(argv[argc-1]);
-  zInput = (const char *)sqlite3_value_text(argv[argc-1]);
+/* SQL_DELETE_SEGDIR_ENTRY
+**   Delete the %_segdir entry on absolute level :1 with index :2.  */
+/* 30 */ "DELETE FROM %Q.'%q_segdir' WHERE level = ? AND idx = ?",
 
-  pHash = (Fts3Hash *)sqlite3_user_data(context);
-  p = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash, zName, nName+1);
+/* SQL_SHIFT_SEGDIR_ENTRY
+**   Modify the idx value for the segment with idx=:3 on absolute level :2
+**   to :1.  */
+/* 31 */ "UPDATE %Q.'%q_segdir' SET idx = ? WHERE level=? AND idx=?",
 
-  if( !p ){
-    char *zErr2 = sqlite3_mprintf("unknown tokenizer: %s", zName);
-    sqlite3_result_error(context, zErr2, -1);
-    sqlite3_free(zErr2);
-    return;
-  }
+/* SQL_SELECT_SEGDIR
+**   Read a single entry from the %_segdir table. The entry from absolute 
+**   level :1 with index value :2.  */
+/* 32 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
+            "FROM %Q.'%q_segdir' WHERE level = ? AND idx = ?",
 
-  pRet = Tcl_NewObj();
-  Tcl_IncrRefCount(pRet);
+/* SQL_CHOMP_SEGDIR
+**   Update the start_block (:1) and root (:2) fields of the %_segdir
+**   entry located on absolute level :3 with index :4.  */
+/* 33 */  "UPDATE %Q.'%q_segdir' SET start_block = ?, root = ?"
+            "WHERE level = ? AND idx = ?",
 
-  for(i=1; i<argc-1; i++){
-    azArg[i-1] = (const char *)sqlite3_value_text(argv[i]);
-  }
+/* SQL_SEGMENT_IS_APPENDABLE
+**   Return a single row if the segment with end_block=? is appendable. Or
+**   no rows otherwise.  */
+/* 34 */  "SELECT 1 FROM %Q.'%q_segments' WHERE blockid=? AND block IS NULL",
 
-  if( SQLITE_OK!=p->xCreate(argc-2, azArg, &pTokenizer) ){
-    zErr = "error in xCreate()";
-    goto finish;
-  }
-  pTokenizer->pModule = p;
-  if( sqlite3Fts3OpenTokenizer(pTokenizer, 0, zInput, nInput, &pCsr) ){
-    zErr = "error in xOpen()";
-    goto finish;
-  }
+/* SQL_SELECT_INDEXES
+**   Return the list of valid segment indexes for absolute level ?  */
+/* 35 */  "SELECT idx FROM %Q.'%q_segdir' WHERE level=? ORDER BY 1 ASC",
 
-  while( SQLITE_OK==p->xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos) ){
-    Tcl_ListObjAppendElement(0, pRet, Tcl_NewIntObj(iPos));
-    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zToken, nToken));
-    zToken = &zInput[iStart];
-    nToken = iEnd-iStart;
-    Tcl_ListObjAppendElement(0, pRet, Tcl_NewStringObj(zToken, nToken));
-  }
+/* SQL_SELECT_MXLEVEL
+**   Return the largest relative level in the FTS index or indexes.  */
+/* 36 */  "SELECT max( level %% 1024 ) FROM %Q.'%q_segdir'",
 
-  if( SQLITE_OK!=p->xClose(pCsr) ){
-    zErr = "error in xClose()";
-    goto finish;
-  }
-  if( SQLITE_OK!=p->xDestroy(pTokenizer) ){
-    zErr = "error in xDestroy()";
-    goto finish;
-  }
+          /* Return segments in order from oldest to newest.*/ 
+/* 37 */  "SELECT level, idx, end_block "
+            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ? "
+            "ORDER BY level DESC, idx ASC",
 
-finish:
-  if( zErr ){
-    sqlite3_result_error(context, zErr, -1);
-  }else{
-    sqlite3_result_text(context, Tcl_GetString(pRet), -1, SQLITE_TRANSIENT);
+          /* Update statements used while promoting segments */
+/* 38 */  "UPDATE OR FAIL %Q.'%q_segdir' SET level=-1,idx=? "
+            "WHERE level=? AND idx=?",
+/* 39 */  "UPDATE OR FAIL %Q.'%q_segdir' SET level=? WHERE level=-1"
+
+  };
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pStmt;
+
+  assert( SizeofArray(azSql)==SizeofArray(p->aStmt) );
+  assert( eStmt<SizeofArray(azSql) && eStmt>=0 );
+  
+  pStmt = p->aStmt[eStmt];
+  if( !pStmt ){
+    char *zSql;
+    if( eStmt==SQL_CONTENT_INSERT ){
+      zSql = sqlite3_mprintf(azSql[eStmt], p->zDb, p->zName, p->zWriteExprlist);
+    }else if( eStmt==SQL_SELECT_CONTENT_BY_ROWID ){
+      zSql = sqlite3_mprintf(azSql[eStmt], p->zReadExprlist);
+    }else{
+      zSql = sqlite3_mprintf(azSql[eStmt], p->zDb, p->zName);
+    }
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, NULL);
+      sqlite3_free(zSql);
+      assert( rc==SQLITE_OK || pStmt==0 );
+      p->aStmt[eStmt] = pStmt;
+    }
+  }
+  if( apVal ){
+    int i;
+    int nParam = sqlite3_bind_parameter_count(pStmt);
+    for(i=0; rc==SQLITE_OK && i<nParam; i++){
+      rc = sqlite3_bind_value(pStmt, i+1, apVal[i]);
+    }
   }
-  Tcl_DecrRefCount(pRet);
+  *pp = pStmt;
+  return rc;
 }
 
-static
-int registerTokenizer(
-  sqlite3 *db, 
-  char *zName, 
-  const sqlite3_tokenizer_module *p
+
+static int fts3SelectDocsize(
+  Fts3Table *pTab,                /* FTS3 table handle */
+  sqlite3_int64 iDocid,           /* Docid to bind for SQL_SELECT_DOCSIZE */
+  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
 ){
-  int rc;
-  sqlite3_stmt *pStmt;
-  const char zSql[] = "SELECT fts3_tokenizer(?, ?)";
+  sqlite3_stmt *pStmt = 0;        /* Statement requested from fts3SqlStmt() */
+  int rc;                         /* Return code */
 
-  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
-  if( rc!=SQLITE_OK ){
-    return rc;
+  rc = fts3SqlStmt(pTab, SQL_SELECT_DOCSIZE, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pStmt, 1, iDocid);
+    rc = sqlite3_step(pStmt);
+    if( rc!=SQLITE_ROW || sqlite3_column_type(pStmt, 0)!=SQLITE_BLOB ){
+      rc = sqlite3_reset(pStmt);
+      if( rc==SQLITE_OK ) rc = FTS_CORRUPT_VTAB;
+      pStmt = 0;
+    }else{
+      rc = SQLITE_OK;
+    }
   }
 
-  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
-  sqlite3_bind_blob(pStmt, 2, &p, sizeof(p), SQLITE_STATIC);
-  sqlite3_step(pStmt);
-
-  return sqlite3_finalize(pStmt);
+  *ppStmt = pStmt;
+  return rc;
 }
 
-static
-int queryTokenizer(
-  sqlite3 *db, 
-  char *zName,  
-  const sqlite3_tokenizer_module **pp
+SQLITE_PRIVATE int sqlite3Fts3SelectDoctotal(
+  Fts3Table *pTab,                /* Fts3 table handle */
+  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
 ){
+  sqlite3_stmt *pStmt = 0;
   int rc;
-  sqlite3_stmt *pStmt;
-  const char zSql[] = "SELECT fts3_tokenizer(?)";
-
-  *pp = 0;
-  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
-  if( SQLITE_ROW==sqlite3_step(pStmt) ){
-    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
-      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
+  rc = fts3SqlStmt(pTab, SQL_SELECT_STAT, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
+    if( sqlite3_step(pStmt)!=SQLITE_ROW
+     || sqlite3_column_type(pStmt, 0)!=SQLITE_BLOB
+    ){
+      rc = sqlite3_reset(pStmt);
+      if( rc==SQLITE_OK ) rc = FTS_CORRUPT_VTAB;
+      pStmt = 0;
     }
   }
-
-  return sqlite3_finalize(pStmt);
+  *ppStmt = pStmt;
+  return rc;
 }
 
-SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(sqlite3_tokenizer_module const**ppModule);
+SQLITE_PRIVATE int sqlite3Fts3SelectDocsize(
+  Fts3Table *pTab,                /* Fts3 table handle */
+  sqlite3_int64 iDocid,           /* Docid to read size data for */
+  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
+){
+  return fts3SelectDocsize(pTab, iDocid, ppStmt);
+}
 
 /*
-** Implementation of the scalar function fts3_tokenizer_internal_test().
-** This function is used for testing only, it is not included in the
-** build unless SQLITE_TEST is defined.
-**
-** The purpose of this is to test that the fts3_tokenizer() function
-** can be used as designed by the C-code in the queryTokenizer and
-** registerTokenizer() functions above. These two functions are repeated
-** in the README.tokenizer file as an example, so it is important to
-** test them.
-**
-** To run the tests, evaluate the fts3_tokenizer_internal_test() scalar
-** function with no arguments. An assert() will fail if a problem is
-** detected. i.e.:
-**
-**     SELECT fts3_tokenizer_internal_test();
+** Similar to fts3SqlStmt(). Except, after binding the parameters in
+** array apVal[] to the SQL statement identified by eStmt, the statement
+** is executed.
 **
+** Returns SQLITE_OK if the statement is successfully executed, or an
+** SQLite error code otherwise.
 */
-static void intTestFunc(
-  sqlite3_context *context,
-  int argc,
-  sqlite3_value **argv
+static void fts3SqlExec(
+  int *pRC,                /* Result code */
+  Fts3Table *p,            /* The FTS3 table */
+  int eStmt,               /* Index of statement to evaluate */
+  sqlite3_value **apVal    /* Parameters to bind */
 ){
+  sqlite3_stmt *pStmt;
   int rc;
-  const sqlite3_tokenizer_module *p1;
-  const sqlite3_tokenizer_module *p2;
-  sqlite3 *db = (sqlite3 *)sqlite3_user_data(context);
-
-  UNUSED_PARAMETER(argc);
-  UNUSED_PARAMETER(argv);
-
-  /* Test the query function */
-  sqlite3Fts3SimpleTokenizerModule(&p1);
-  rc = queryTokenizer(db, "simple", &p2);
-  assert( rc==SQLITE_OK );
-  assert( p1==p2 );
-  rc = queryTokenizer(db, "nosuchtokenizer", &p2);
-  assert( rc==SQLITE_ERROR );
-  assert( p2==0 );
-  assert( 0==strcmp(sqlite3_errmsg(db), "unknown tokenizer: nosuchtokenizer") );
-
-  /* Test the storage function */
-  rc = registerTokenizer(db, "nosuchtokenizer", p1);
-  assert( rc==SQLITE_OK );
-  rc = queryTokenizer(db, "nosuchtokenizer", &p2);
-  assert( rc==SQLITE_OK );
-  assert( p2==p1 );
-
-  sqlite3_result_text(context, "ok", -1, SQLITE_STATIC);
+  if( *pRC ) return;
+  rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
+  if( rc==SQLITE_OK ){
+    sqlite3_step(pStmt);
+    rc = sqlite3_reset(pStmt);
+  }
+  *pRC = rc;
 }
 
-#endif
 
 /*
-** Set up SQL objects in database db used to access the contents of
-** the hash table pointed to by argument pHash. The hash table must
-** been initialized to use string keys, and to take a private copy 
-** of the key when a value is inserted. i.e. by a call similar to:
-**
-**    sqlite3Fts3HashInit(pHash, FTS3_HASH_STRING, 1);
-**
-** This function adds a scalar function (see header comment above
-** scalarFunc() in this file for details) and, if ENABLE_TABLE is
-** defined at compilation time, a temporary virtual table (see header 
-** comment above struct HashTableVtab) to the database schema. Both 
-** provide read/write access to the contents of *pHash.
+** This function ensures that the caller has obtained an exclusive 
+** shared-cache table-lock on the %_segdir table. This is required before 
+** writing data to the fts3 table. If this lock is not acquired first, then
+** the caller may end up attempting to take this lock as part of committing
+** a transaction, causing SQLite to return SQLITE_LOCKED or 
+** LOCKED_SHAREDCACHEto a COMMIT command.
 **
-** The third argument to this function, zName, is used as the name
-** of both the scalar and, if created, the virtual table.
+** It is best to avoid this because if FTS3 returns any error when 
+** committing a transaction, the whole transaction will be rolled back. 
+** And this is not what users expect when they get SQLITE_LOCKED_SHAREDCACHE. 
+** It can still happen if the user locks the underlying tables directly 
+** instead of accessing them via FTS.
 */
-SQLITE_PRIVATE int sqlite3Fts3InitHashTable(
-  sqlite3 *db, 
-  Fts3Hash *pHash, 
-  const char *zName
-){
+static int fts3Writelock(Fts3Table *p){
   int rc = SQLITE_OK;
-  void *p = (void *)pHash;
-  const int any = SQLITE_ANY;
-
-#ifdef SQLITE_TEST
-  char *zTest = 0;
-  char *zTest2 = 0;
-  void *pdb = (void *)db;
-  zTest = sqlite3_mprintf("%s_test", zName);
-  zTest2 = sqlite3_mprintf("%s_internal_test", zName);
-  if( !zTest || !zTest2 ){
-    rc = SQLITE_NOMEM;
-  }
-#endif
-
-  if( SQLITE_OK==rc ){
-    rc = sqlite3_create_function(db, zName, 1, any, p, scalarFunc, 0, 0);
-  }
-  if( SQLITE_OK==rc ){
-    rc = sqlite3_create_function(db, zName, 2, any, p, scalarFunc, 0, 0);
-  }
-#ifdef SQLITE_TEST
-  if( SQLITE_OK==rc ){
-    rc = sqlite3_create_function(db, zTest, -1, any, p, testFunc, 0, 0);
-  }
-  if( SQLITE_OK==rc ){
-    rc = sqlite3_create_function(db, zTest2, 0, any, pdb, intTestFunc, 0, 0);
+  
+  if( p->nPendingData==0 ){
+    sqlite3_stmt *pStmt;
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_LEVEL, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_null(pStmt, 1);
+      sqlite3_step(pStmt);
+      rc = sqlite3_reset(pStmt);
+    }
   }
-#endif
-
-#ifdef SQLITE_TEST
-  sqlite3_free(zTest);
-  sqlite3_free(zTest2);
-#endif
 
   return rc;
 }
 
-#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
-
-/************** End of fts3_tokenizer.c **************************************/
-/************** Begin file fts3_tokenizer1.c *********************************/
 /*
-** 2006 Oct 10
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
+** FTS maintains a separate indexes for each language-id (a 32-bit integer).
+** Within each language id, a separate index is maintained to store the
+** document terms, and each configured prefix size (configured the FTS 
+** "prefix=" option). And each index consists of multiple levels ("relative
+** levels").
 **
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
+** All three of these values (the language id, the specific index and the
+** level within the index) are encoded in 64-bit integer values stored
+** in the %_segdir table on disk. This function is used to convert three
+** separate component values into the single 64-bit integer value that
+** can be used to query the %_segdir table.
 **
-******************************************************************************
+** Specifically, each language-id/index combination is allocated 1024 
+** 64-bit integer level values ("absolute levels"). The main terms index
+** for language-id 0 is allocate values 0-1023. The first prefix index
+** (if any) for language-id 0 is allocated values 1024-2047. And so on.
+** Language 1 indexes are allocated immediately following language 0.
 **
-** Implementation of the "simple" full-text-search tokenizer.
+** So, for a system with nPrefix prefix indexes configured, the block of
+** absolute levels that corresponds to language-id iLangid and index 
+** iIndex starts at absolute level ((iLangid * (nPrefix+1) + iIndex) * 1024).
 */
+static sqlite3_int64 getAbsoluteLevel(
+  Fts3Table *p,                   /* FTS3 table handle */
+  int iLangid,                    /* Language id */
+  int iIndex,                     /* Index in p->aIndex[] */
+  int iLevel                      /* Level of segments */
+){
+  sqlite3_int64 iBase;            /* First absolute level for iLangid/iIndex */
+  assert( iLangid>=0 );
+  assert( p->nIndex>0 );
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  iBase = ((sqlite3_int64)iLangid * p->nIndex + iIndex) * FTS3_SEGDIR_MAXLEVEL;
+  return iBase + iLevel;
+}
 
 /*
-** The code in this file is only compiled if:
+** Set *ppStmt to a statement handle that may be used to iterate through
+** all rows in the %_segdir table, from oldest to newest. If successful,
+** return SQLITE_OK. If an error occurs while preparing the statement, 
+** return an SQLite error code.
 **
-**     * The FTS3 module is being built as an extension
-**       (in which case SQLITE_CORE is not defined), or
+** There is only ever one instance of this SQL statement compiled for
+** each FTS3 table.
 **
-**     * The FTS3 module is being built into the core of
-**       SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
+** The statement returns the following columns from the %_segdir table:
+**
+**   0: idx
+**   1: start_block
+**   2: leaves_end_block
+**   3: end_block
+**   4: root
 */
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+SQLITE_PRIVATE int sqlite3Fts3AllSegdirs(
+  Fts3Table *p,                   /* FTS3 table */
+  int iLangid,                    /* Language being queried */
+  int iIndex,                     /* Index for p->aIndex[] */
+  int iLevel,                     /* Level to select (relative level) */
+  sqlite3_stmt **ppStmt           /* OUT: Compiled statement */
+){
+  int rc;
+  sqlite3_stmt *pStmt = 0;
 
-/* #include <assert.h> */
-/* #include <stdlib.h> */
-/* #include <stdio.h> */
-/* #include <string.h> */
+  assert( iLevel==FTS3_SEGCURSOR_ALL || iLevel>=0 );
+  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
+  assert( iIndex>=0 && iIndex<p->nIndex );
 
+  if( iLevel<0 ){
+    /* "SELECT * FROM %_segdir WHERE level BETWEEN ? AND ? ORDER BY ..." */
+    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE, &pStmt, 0);
+    if( rc==SQLITE_OK ){ 
+      sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
+      sqlite3_bind_int64(pStmt, 2, 
+          getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
+      );
+    }
+  }else{
+    /* "SELECT * FROM %_segdir WHERE level = ? ORDER BY ..." */
+    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL, &pStmt, 0);
+    if( rc==SQLITE_OK ){ 
+      sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex,iLevel));
+    }
+  }
+  *ppStmt = pStmt;
+  return rc;
+}
 
-typedef struct simple_tokenizer {
-  sqlite3_tokenizer base;
-  char delim[128];             /* flag ASCII delimiters */
-} simple_tokenizer;
 
-typedef struct simple_tokenizer_cursor {
-  sqlite3_tokenizer_cursor base;
-  const char *pInput;          /* input we are tokenizing */
-  int nBytes;                  /* size of the input */
-  int iOffset;                 /* current position in pInput */
-  int iToken;                  /* index of next token to be returned */
-  char *pToken;                /* storage for current token */
-  int nTokenAllocated;         /* space allocated to zToken buffer */
-} simple_tokenizer_cursor;
+/*
+** Append a single varint to a PendingList buffer. SQLITE_OK is returned
+** if successful, or an SQLite error code otherwise.
+**
+** This function also serves to allocate the PendingList structure itself.
+** For example, to create a new PendingList structure containing two
+** varints:
+**
+**   PendingList *p = 0;
+**   fts3PendingListAppendVarint(&p, 1);
+**   fts3PendingListAppendVarint(&p, 2);
+*/
+static int fts3PendingListAppendVarint(
+  PendingList **pp,               /* IN/OUT: Pointer to PendingList struct */
+  sqlite3_int64 i                 /* Value to append to data */
+){
+  PendingList *p = *pp;
 
+  /* Allocate or grow the PendingList as required. */
+  if( !p ){
+    p = sqlite3_malloc(sizeof(*p) + 100);
+    if( !p ){
+      return SQLITE_NOMEM;
+    }
+    p->nSpace = 100;
+    p->aData = (char *)&p[1];
+    p->nData = 0;
+  }
+  else if( p->nData+FTS3_VARINT_MAX+1>p->nSpace ){
+    int nNew = p->nSpace * 2;
+    p = sqlite3_realloc(p, sizeof(*p) + nNew);
+    if( !p ){
+      sqlite3_free(*pp);
+      *pp = 0;
+      return SQLITE_NOMEM;
+    }
+    p->nSpace = nNew;
+    p->aData = (char *)&p[1];
+  }
 
-static int simpleDelim(simple_tokenizer *t, unsigned char c){
-  return c<0x80 && t->delim[c];
-}
-static int fts3_isalnum(int x){
-  return (x>='0' && x<='9') || (x>='A' && x<='Z') || (x>='a' && x<='z');
+  /* Append the new serialized varint to the end of the list. */
+  p->nData += sqlite3Fts3PutVarint(&p->aData[p->nData], i);
+  p->aData[p->nData] = '\0';
+  *pp = p;
+  return SQLITE_OK;
 }
 
 /*
-** Create a new tokenizer instance.
+** Add a docid/column/position entry to a PendingList structure. Non-zero
+** is returned if the structure is sqlite3_realloced as part of adding
+** the entry. Otherwise, zero.
+**
+** If an OOM error occurs, *pRc is set to SQLITE_NOMEM before returning.
+** Zero is always returned in this case. Otherwise, if no OOM error occurs,
+** it is set to SQLITE_OK.
 */
-static int simpleCreate(
-  int argc, const char * const *argv,
-  sqlite3_tokenizer **ppTokenizer
+static int fts3PendingListAppend(
+  PendingList **pp,               /* IN/OUT: PendingList structure */
+  sqlite3_int64 iDocid,           /* Docid for entry to add */
+  sqlite3_int64 iCol,             /* Column for entry to add */
+  sqlite3_int64 iPos,             /* Position of term for entry to add */
+  int *pRc                        /* OUT: Return code */
 ){
-  simple_tokenizer *t;
+  PendingList *p = *pp;
+  int rc = SQLITE_OK;
 
-  t = (simple_tokenizer *) sqlite3_malloc(sizeof(*t));
-  if( t==NULL ) return SQLITE_NOMEM;
-  memset(t, 0, sizeof(*t));
+  assert( !p || p->iLastDocid<=iDocid );
 
-  /* TODO(shess) Delimiters need to remain the same from run to run,
-  ** else we need to reindex.  One solution would be a meta-table to
-  ** track such information in the database, then we'd only want this
-  ** information on the initial create.
-  */
-  if( argc>1 ){
-    int i, n = (int)strlen(argv[1]);
-    for(i=0; i<n; i++){
-      unsigned char ch = argv[1][i];
-      /* We explicitly don't support UTF-8 delimiters for now. */
-      if( ch>=0x80 ){
-        sqlite3_free(t);
-        return SQLITE_ERROR;
-      }
-      t->delim[ch] = 1;
+  if( !p || p->iLastDocid!=iDocid ){
+    sqlite3_int64 iDelta = iDocid - (p ? p->iLastDocid : 0);
+    if( p ){
+      assert( p->nData<p->nSpace );
+      assert( p->aData[p->nData]==0 );
+      p->nData++;
     }
-  } else {
-    /* Mark non-alphanumeric ASCII characters as delimiters */
-    int i;
-    for(i=1; i<0x80; i++){
-      t->delim[i] = !fts3_isalnum(i) ? -1 : 0;
+    if( SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, iDelta)) ){
+      goto pendinglistappend_out;
+    }
+    p->iLastCol = -1;
+    p->iLastPos = 0;
+    p->iLastDocid = iDocid;
+  }
+  if( iCol>0 && p->iLastCol!=iCol ){
+    if( SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, 1))
+     || SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, iCol))
+    ){
+      goto pendinglistappend_out;
+    }
+    p->iLastCol = iCol;
+    p->iLastPos = 0;
+  }
+  if( iCol>=0 ){
+    assert( iPos>p->iLastPos || (iPos==0 && p->iLastPos==0) );
+    rc = fts3PendingListAppendVarint(&p, 2+iPos-p->iLastPos);
+    if( rc==SQLITE_OK ){
+      p->iLastPos = iPos;
     }
   }
 
-  *ppTokenizer = &t->base;
-  return SQLITE_OK;
+ pendinglistappend_out:
+  *pRc = rc;
+  if( p!=*pp ){
+    *pp = p;
+    return 1;
+  }
+  return 0;
 }
 
 /*
-** Destroy a tokenizer
+** Free a PendingList object allocated by fts3PendingListAppend().
 */
-static int simpleDestroy(sqlite3_tokenizer *pTokenizer){
-  sqlite3_free(pTokenizer);
-  return SQLITE_OK;
+static void fts3PendingListDelete(PendingList *pList){
+  sqlite3_free(pList);
 }
 
 /*
-** Prepare to begin tokenizing a particular string.  The input
-** string to be tokenized is pInput[0..nBytes-1].  A cursor
-** used to incrementally tokenize this string is returned in 
-** *ppCursor.
+** Add an entry to one of the pending-terms hash tables.
 */
-static int simpleOpen(
-  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
-  const char *pInput, int nBytes,        /* String to be tokenized */
-  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
+static int fts3PendingTermsAddOne(
+  Fts3Table *p,
+  int iCol,
+  int iPos,
+  Fts3Hash *pHash,                /* Pending terms hash table to add entry to */
+  const char *zToken,
+  int nToken
 ){
-  simple_tokenizer_cursor *c;
-
-  UNUSED_PARAMETER(pTokenizer);
-
-  c = (simple_tokenizer_cursor *) sqlite3_malloc(sizeof(*c));
-  if( c==NULL ) return SQLITE_NOMEM;
+  PendingList *pList;
+  int rc = SQLITE_OK;
 
-  c->pInput = pInput;
-  if( pInput==0 ){
-    c->nBytes = 0;
-  }else if( nBytes<0 ){
-    c->nBytes = (int)strlen(pInput);
-  }else{
-    c->nBytes = nBytes;
+  pList = (PendingList *)fts3HashFind(pHash, zToken, nToken);
+  if( pList ){
+    p->nPendingData -= (pList->nData + nToken + sizeof(Fts3HashElem));
   }
-  c->iOffset = 0;                 /* start tokenizing at the beginning */
-  c->iToken = 0;
-  c->pToken = NULL;               /* no space allocated, yet. */
-  c->nTokenAllocated = 0;
-
-  *ppCursor = &c->base;
-  return SQLITE_OK;
-}
-
-/*
-** Close a tokenization cursor previously opened by a call to
-** simpleOpen() above.
-*/
-static int simpleClose(sqlite3_tokenizer_cursor *pCursor){
-  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
-  sqlite3_free(c->pToken);
-  sqlite3_free(c);
-  return SQLITE_OK;
+  if( fts3PendingListAppend(&pList, p->iPrevDocid, iCol, iPos, &rc) ){
+    if( pList==fts3HashInsert(pHash, zToken, nToken, pList) ){
+      /* Malloc failed while inserting the new entry. This can only 
+      ** happen if there was no previous entry for this token.
+      */
+      assert( 0==fts3HashFind(pHash, zToken, nToken) );
+      sqlite3_free(pList);
+      rc = SQLITE_NOMEM;
+    }
+  }
+  if( rc==SQLITE_OK ){
+    p->nPendingData += (pList->nData + nToken + sizeof(Fts3HashElem));
+  }
+  return rc;
 }
 
 /*
-** Extract the next token from a tokenization cursor.  The cursor must
-** have been opened by a prior call to simpleOpen().
+** Tokenize the nul-terminated string zText and add all tokens to the
+** pending-terms hash-table. The docid used is that currently stored in
+** p->iPrevDocid, and the column is specified by argument iCol.
+**
+** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
 */
-static int simpleNext(
-  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
-  const char **ppToken,               /* OUT: *ppToken is the token text */
-  int *pnBytes,                       /* OUT: Number of bytes in token */
-  int *piStartOffset,                 /* OUT: Starting offset of token */
-  int *piEndOffset,                   /* OUT: Ending offset of token */
-  int *piPosition                     /* OUT: Position integer of token */
+static int fts3PendingTermsAdd(
+  Fts3Table *p,                   /* Table into which text will be inserted */
+  int iLangid,                    /* Language id to use */
+  const char *zText,              /* Text of document to be inserted */
+  int iCol,                       /* Column into which text is being inserted */
+  u32 *pnWord                     /* IN/OUT: Incr. by number tokens inserted */
 ){
-  simple_tokenizer_cursor *c = (simple_tokenizer_cursor *) pCursor;
-  simple_tokenizer *t = (simple_tokenizer *) pCursor->pTokenizer;
-  unsigned char *p = (unsigned char *)c->pInput;
+  int rc;
+  int iStart = 0;
+  int iEnd = 0;
+  int iPos = 0;
+  int nWord = 0;
 
-  while( c->iOffset<c->nBytes ){
-    int iStartOffset;
+  char const *zToken;
+  int nToken = 0;
 
-    /* Scan past delimiter characters */
-    while( c->iOffset<c->nBytes && simpleDelim(t, p[c->iOffset]) ){
-      c->iOffset++;
+  sqlite3_tokenizer *pTokenizer = p->pTokenizer;
+  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
+  sqlite3_tokenizer_cursor *pCsr;
+  int (*xNext)(sqlite3_tokenizer_cursor *pCursor,
+      const char**,int*,int*,int*,int*);
+
+  assert( pTokenizer && pModule );
+
+  /* If the user has inserted a NULL value, this function may be called with
+  ** zText==0. In this case, add zero token entries to the hash table and 
+  ** return early. */
+  if( zText==0 ){
+    *pnWord = 0;
+    return SQLITE_OK;
+  }
+
+  rc = sqlite3Fts3OpenTokenizer(pTokenizer, iLangid, zText, -1, &pCsr);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  xNext = pModule->xNext;
+  while( SQLITE_OK==rc
+      && SQLITE_OK==(rc = xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos))
+  ){
+    int i;
+    if( iPos>=nWord ) nWord = iPos+1;
+
+    /* Positions cannot be negative; we use -1 as a terminator internally.
+    ** Tokens must have a non-zero length.
+    */
+    if( iPos<0 || !zToken || nToken<=0 ){
+      rc = SQLITE_ERROR;
+      break;
     }
 
-    /* Count non-delimiter characters. */
-    iStartOffset = c->iOffset;
-    while( c->iOffset<c->nBytes && !simpleDelim(t, p[c->iOffset]) ){
-      c->iOffset++;
+    /* Add the term to the terms index */
+    rc = fts3PendingTermsAddOne(
+        p, iCol, iPos, &p->aIndex[0].hPending, zToken, nToken
+    );
+    
+    /* Add the term to each of the prefix indexes that it is not too 
+    ** short for. */
+    for(i=1; rc==SQLITE_OK && i<p->nIndex; i++){
+      struct Fts3Index *pIndex = &p->aIndex[i];
+      if( nToken<pIndex->nPrefix ) continue;
+      rc = fts3PendingTermsAddOne(
+          p, iCol, iPos, &pIndex->hPending, zToken, pIndex->nPrefix
+      );
     }
+  }
 
-    if( c->iOffset>iStartOffset ){
-      int i, n = c->iOffset-iStartOffset;
-      if( n>c->nTokenAllocated ){
-        char *pNew;
-        c->nTokenAllocated = n+20;
-        pNew = sqlite3_realloc(c->pToken, c->nTokenAllocated);
-        if( !pNew ) return SQLITE_NOMEM;
-        c->pToken = pNew;
-      }
-      for(i=0; i<n; i++){
-        /* TODO(shess) This needs expansion to handle UTF-8
-        ** case-insensitivity.
-        */
-        unsigned char ch = p[iStartOffset+i];
-        c->pToken[i] = (char)((ch>='A' && ch<='Z') ? ch-'A'+'a' : ch);
-      }
-      *ppToken = c->pToken;
-      *pnBytes = n;
-      *piStartOffset = iStartOffset;
-      *piEndOffset = c->iOffset;
-      *piPosition = c->iToken++;
+  pModule->xClose(pCsr);
+  *pnWord += nWord;
+  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
+}
 
-      return SQLITE_OK;
-    }
+/* 
+** Calling this function indicates that subsequent calls to 
+** fts3PendingTermsAdd() are to add term/position-list pairs for the
+** contents of the document with docid iDocid.
+*/
+static int fts3PendingTermsDocid(
+  Fts3Table *p,                   /* Full-text table handle */
+  int iLangid,                    /* Language id of row being written */
+  sqlite_int64 iDocid             /* Docid of row being written */
+){
+  assert( iLangid>=0 );
+
+  /* TODO(shess) Explore whether partially flushing the buffer on
+  ** forced-flush would provide better performance.  I suspect that if
+  ** we ordered the doclists by size and flushed the largest until the
+  ** buffer was half empty, that would let the less frequent terms
+  ** generate longer doclists.
+  */
+  if( iDocid<=p->iPrevDocid 
+   || p->iPrevLangid!=iLangid
+   || p->nPendingData>p->nMaxPendingData 
+  ){
+    int rc = sqlite3Fts3PendingTermsFlush(p);
+    if( rc!=SQLITE_OK ) return rc;
   }
-  return SQLITE_DONE;
+  p->iPrevDocid = iDocid;
+  p->iPrevLangid = iLangid;
+  return SQLITE_OK;
 }
 
 /*
-** The set of routines that implement the simple tokenizer
+** Discard the contents of the pending-terms hash tables. 
 */
-static const sqlite3_tokenizer_module simpleTokenizerModule = {
-  0,
-  simpleCreate,
-  simpleDestroy,
-  simpleOpen,
-  simpleClose,
-  simpleNext,
-  0,
-};
+SQLITE_PRIVATE void sqlite3Fts3PendingTermsClear(Fts3Table *p){
+  int i;
+  for(i=0; i<p->nIndex; i++){
+    Fts3HashElem *pElem;
+    Fts3Hash *pHash = &p->aIndex[i].hPending;
+    for(pElem=fts3HashFirst(pHash); pElem; pElem=fts3HashNext(pElem)){
+      PendingList *pList = (PendingList *)fts3HashData(pElem);
+      fts3PendingListDelete(pList);
+    }
+    fts3HashClear(pHash);
+  }
+  p->nPendingData = 0;
+}
 
 /*
-** Allocate a new simple tokenizer.  Return a pointer to the new
-** tokenizer in *ppModule
+** This function is called by the xUpdate() method as part of an INSERT
+** operation. It adds entries for each term in the new record to the
+** pendingTerms hash table.
+**
+** Argument apVal is the same as the similarly named argument passed to
+** fts3InsertData(). Parameter iDocid is the docid of the new row.
 */
-SQLITE_PRIVATE void sqlite3Fts3SimpleTokenizerModule(
-  sqlite3_tokenizer_module const**ppModule
+static int fts3InsertTerms(
+  Fts3Table *p, 
+  int iLangid, 
+  sqlite3_value **apVal, 
+  u32 *aSz
 ){
-  *ppModule = &simpleTokenizerModule;
+  int i;                          /* Iterator variable */
+  for(i=2; i<p->nColumn+2; i++){
+    int iCol = i-2;
+    if( p->abNotindexed[iCol]==0 ){
+      const char *zText = (const char *)sqlite3_value_text(apVal[i]);
+      int rc = fts3PendingTermsAdd(p, iLangid, zText, iCol, &aSz[iCol]);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      aSz[p->nColumn] += sqlite3_value_bytes(apVal[i]);
+    }
+  }
+  return SQLITE_OK;
 }
 
-#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
-
-/************** End of fts3_tokenizer1.c *************************************/
-/************** Begin file fts3_tokenize_vtab.c ******************************/
 /*
-** 2013 Apr 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains code for the "fts3tokenize" virtual table module.
-** An fts3tokenize virtual table is created as follows:
-**
-**   CREATE VIRTUAL TABLE <tbl> USING fts3tokenize(
-**       <tokenizer-name>, <arg-1>, ...
-**   );
-**
-** The table created has the following schema:
-**
-**   CREATE TABLE <tbl>(input, token, start, end, position)
-**
-** When queried, the query must include a WHERE clause of type:
-**
-**   input = <string>
-**
-** The virtual table module tokenizes this <string>, using the FTS3 
-** tokenizer specified by the arguments to the CREATE VIRTUAL TABLE 
-** statement and returns one row for each token in the result. With
-** fields set as follows:
-**
-**   input:   Always set to a copy of <string>
-**   token:   A token from the input.
-**   start:   Byte offset of the token within the input <string>.
-**   end:     Byte offset of the byte immediately following the end of the
-**            token within the input string.
-**   pos:     Token offset of token within input.
+** This function is called by the xUpdate() method for an INSERT operation.
+** The apVal parameter is passed a copy of the apVal argument passed by
+** SQLite to the xUpdate() method. i.e:
 **
+**   apVal[0]                Not used for INSERT.
+**   apVal[1]                rowid
+**   apVal[2]                Left-most user-defined column
+**   ...
+**   apVal[p->nColumn+1]     Right-most user-defined column
+**   apVal[p->nColumn+2]     Hidden column with same name as table
+**   apVal[p->nColumn+3]     Hidden "docid" column (alias for rowid)
+**   apVal[p->nColumn+4]     Hidden languageid column
 */
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+static int fts3InsertData(
+  Fts3Table *p,                   /* Full-text table */
+  sqlite3_value **apVal,          /* Array of values to insert */
+  sqlite3_int64 *piDocid          /* OUT: Docid for row just inserted */
+){
+  int rc;                         /* Return code */
+  sqlite3_stmt *pContentInsert;   /* INSERT INTO %_content VALUES(...) */
+
+  if( p->zContentTbl ){
+    sqlite3_value *pRowid = apVal[p->nColumn+3];
+    if( sqlite3_value_type(pRowid)==SQLITE_NULL ){
+      pRowid = apVal[1];
+    }
+    if( sqlite3_value_type(pRowid)!=SQLITE_INTEGER ){
+      return SQLITE_CONSTRAINT;
+    }
+    *piDocid = sqlite3_value_int64(pRowid);
+    return SQLITE_OK;
+  }
+
+  /* Locate the statement handle used to insert data into the %_content
+  ** table. The SQL for this statement is:
+  **
+  **   INSERT INTO %_content VALUES(?, ?, ?, ...)
+  **
+  ** The statement features N '?' variables, where N is the number of user
+  ** defined columns in the FTS3 table, plus one for the docid field.
+  */
+  rc = fts3SqlStmt(p, SQL_CONTENT_INSERT, &pContentInsert, &apVal[1]);
+  if( rc==SQLITE_OK && p->zLanguageid ){
+    rc = sqlite3_bind_int(
+        pContentInsert, p->nColumn+2, 
+        sqlite3_value_int(apVal[p->nColumn+4])
+    );
+  }
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* There is a quirk here. The users INSERT statement may have specified
+  ** a value for the "rowid" field, for the "docid" field, or for both.
+  ** Which is a problem, since "rowid" and "docid" are aliases for the
+  ** same value. For example:
+  **
+  **   INSERT INTO fts3tbl(rowid, docid) VALUES(1, 2);
+  **
+  ** In FTS3, this is an error. It is an error to specify non-NULL values
+  ** for both docid and some other rowid alias.
+  */
+  if( SQLITE_NULL!=sqlite3_value_type(apVal[3+p->nColumn]) ){
+    if( SQLITE_NULL==sqlite3_value_type(apVal[0])
+     && SQLITE_NULL!=sqlite3_value_type(apVal[1])
+    ){
+      /* A rowid/docid conflict. */
+      return SQLITE_ERROR;
+    }
+    rc = sqlite3_bind_value(pContentInsert, 1, apVal[3+p->nColumn]);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+
+  /* Execute the statement to insert the record. Set *piDocid to the 
+  ** new docid value. 
+  */
+  sqlite3_step(pContentInsert);
+  rc = sqlite3_reset(pContentInsert);
+
+  *piDocid = sqlite3_last_insert_rowid(p->db);
+  return rc;
+}
 
-/* #include <string.h> */
-/* #include <assert.h> */
 
-typedef struct Fts3tokTable Fts3tokTable;
-typedef struct Fts3tokCursor Fts3tokCursor;
 
 /*
-** Virtual table structure.
+** Remove all data from the FTS3 table. Clear the hash table containing
+** pending terms.
 */
-struct Fts3tokTable {
-  sqlite3_vtab base;              /* Base class used by SQLite core */
-  const sqlite3_tokenizer_module *pMod;
-  sqlite3_tokenizer *pTok;
-};
+static int fts3DeleteAll(Fts3Table *p, int bContent){
+  int rc = SQLITE_OK;             /* Return code */
+
+  /* Discard the contents of the pending-terms hash table. */
+  sqlite3Fts3PendingTermsClear(p);
+
+  /* Delete everything from the shadow tables. Except, leave %_content as
+  ** is if bContent is false.  */
+  assert( p->zContentTbl==0 || bContent==0 );
+  if( bContent ) fts3SqlExec(&rc, p, SQL_DELETE_ALL_CONTENT, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGMENTS, 0);
+  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
+  if( p->bHasDocsize ){
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_DOCSIZE, 0);
+  }
+  if( p->bHasStat ){
+    fts3SqlExec(&rc, p, SQL_DELETE_ALL_STAT, 0);
+  }
+  return rc;
+}
 
 /*
-** Virtual table cursor structure.
+**
 */
-struct Fts3tokCursor {
-  sqlite3_vtab_cursor base;       /* Base class used by SQLite core */
-  char *zInput;                   /* Input string */
-  sqlite3_tokenizer_cursor *pCsr; /* Cursor to iterate through zInput */
-  int iRowid;                     /* Current 'rowid' value */
-  const char *zToken;             /* Current 'token' value */
-  int nToken;                     /* Size of zToken in bytes */
-  int iStart;                     /* Current 'start' value */
-  int iEnd;                       /* Current 'end' value */
-  int iPos;                       /* Current 'pos' value */
-};
+static int langidFromSelect(Fts3Table *p, sqlite3_stmt *pSelect){
+  int iLangid = 0;
+  if( p->zLanguageid ) iLangid = sqlite3_column_int(pSelect, p->nColumn+1);
+  return iLangid;
+}
 
 /*
-** Query FTS for the tokenizer implementation named zName.
+** The first element in the apVal[] array is assumed to contain the docid
+** (an integer) of a row about to be deleted. Remove all terms from the
+** full-text index.
 */
-static int fts3tokQueryTokenizer(
-  Fts3Hash *pHash,
-  const char *zName,
-  const sqlite3_tokenizer_module **pp,
-  char **pzErr
+static void fts3DeleteTerms( 
+  int *pRC,               /* Result code */
+  Fts3Table *p,           /* The FTS table to delete from */
+  sqlite3_value *pRowid,  /* The docid to be deleted */
+  u32 *aSz,               /* Sizes of deleted document written here */
+  int *pbFound            /* OUT: Set to true if row really does exist */
 ){
-  sqlite3_tokenizer_module *p;
-  int nName = (int)strlen(zName);
+  int rc;
+  sqlite3_stmt *pSelect;
 
-  p = (sqlite3_tokenizer_module *)sqlite3Fts3HashFind(pHash, zName, nName+1);
-  if( !p ){
-    sqlite3Fts3ErrMsg(pzErr, "unknown tokenizer: %s", zName);
-    return SQLITE_ERROR;
+  assert( *pbFound==0 );
+  if( *pRC ) return;
+  rc = fts3SqlStmt(p, SQL_SELECT_CONTENT_BY_ROWID, &pSelect, &pRowid);
+  if( rc==SQLITE_OK ){
+    if( SQLITE_ROW==sqlite3_step(pSelect) ){
+      int i;
+      int iLangid = langidFromSelect(p, pSelect);
+      rc = fts3PendingTermsDocid(p, iLangid, sqlite3_column_int64(pSelect, 0));
+      for(i=1; rc==SQLITE_OK && i<=p->nColumn; i++){
+        int iCol = i-1;
+        if( p->abNotindexed[iCol]==0 ){
+          const char *zText = (const char *)sqlite3_column_text(pSelect, i);
+          rc = fts3PendingTermsAdd(p, iLangid, zText, -1, &aSz[iCol]);
+          aSz[p->nColumn] += sqlite3_column_bytes(pSelect, i);
+        }
+      }
+      if( rc!=SQLITE_OK ){
+        sqlite3_reset(pSelect);
+        *pRC = rc;
+        return;
+      }
+      *pbFound = 1;
+    }
+    rc = sqlite3_reset(pSelect);
+  }else{
+    sqlite3_reset(pSelect);
   }
-
-  *pp = p;
-  return SQLITE_OK;
+  *pRC = rc;
 }
 
 /*
-** The second argument, argv[], is an array of pointers to nul-terminated
-** strings. This function makes a copy of the array and strings into a 
-** single block of memory. It then dequotes any of the strings that appear
-** to be quoted.
+** Forward declaration to account for the circular dependency between
+** functions fts3SegmentMerge() and fts3AllocateSegdirIdx().
+*/
+static int fts3SegmentMerge(Fts3Table *, int, int, int);
+
+/* 
+** This function allocates a new level iLevel index in the segdir table.
+** Usually, indexes are allocated within a level sequentially starting
+** with 0, so the allocated index is one greater than the value returned
+** by:
 **
-** If successful, output parameter *pazDequote is set to point at the
-** array of dequoted strings and SQLITE_OK is returned. The caller is
-** responsible for eventually calling sqlite3_free() to free the array
-** in this case. Or, if an error occurs, an SQLite error code is returned.
-** The final value of *pazDequote is undefined in this case.
+**   SELECT max(idx) FROM %_segdir WHERE level = :iLevel
+**
+** However, if there are already FTS3_MERGE_COUNT indexes at the requested
+** level, they are merged into a single level (iLevel+1) segment and the 
+** allocated index is 0.
+**
+** If successful, *piIdx is set to the allocated index slot and SQLITE_OK
+** returned. Otherwise, an SQLite error code is returned.
 */
-static int fts3tokDequoteArray(
-  int argc,                       /* Number of elements in argv[] */
-  const char * const *argv,       /* Input array */
-  char ***pazDequote              /* Output array */
+static int fts3AllocateSegdirIdx(
+  Fts3Table *p, 
+  int iLangid,                    /* Language id */
+  int iIndex,                     /* Index for p->aIndex */
+  int iLevel, 
+  int *piIdx
 ){
-  int rc = SQLITE_OK;             /* Return code */
-  if( argc==0 ){
-    *pazDequote = 0;
-  }else{
-    int i;
-    int nByte = 0;
-    char **azDequote;
+  int rc;                         /* Return Code */
+  sqlite3_stmt *pNextIdx;         /* Query for next idx at level iLevel */
+  int iNext = 0;                  /* Result of query pNextIdx */
 
-    for(i=0; i<argc; i++){
-      nByte += (int)(strlen(argv[i]) + 1);
+  assert( iLangid>=0 );
+  assert( p->nIndex>=1 );
+
+  /* Set variable iNext to the next available segdir index at level iLevel. */
+  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENT_INDEX, &pNextIdx, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(
+        pNextIdx, 1, getAbsoluteLevel(p, iLangid, iIndex, iLevel)
+    );
+    if( SQLITE_ROW==sqlite3_step(pNextIdx) ){
+      iNext = sqlite3_column_int(pNextIdx, 0);
     }
+    rc = sqlite3_reset(pNextIdx);
+  }
 
-    *pazDequote = azDequote = sqlite3_malloc(sizeof(char *)*argc + nByte);
-    if( azDequote==0 ){
-      rc = SQLITE_NOMEM;
+  if( rc==SQLITE_OK ){
+    /* If iNext is FTS3_MERGE_COUNT, indicating that level iLevel is already
+    ** full, merge all segments in level iLevel into a single iLevel+1
+    ** segment and allocate (newly freed) index 0 at level iLevel. Otherwise,
+    ** if iNext is less than FTS3_MERGE_COUNT, allocate index iNext.
+    */
+    if( iNext>=FTS3_MERGE_COUNT ){
+      fts3LogMerge(16, getAbsoluteLevel(p, iLangid, iIndex, iLevel));
+      rc = fts3SegmentMerge(p, iLangid, iIndex, iLevel);
+      *piIdx = 0;
     }else{
-      char *pSpace = (char *)&azDequote[argc];
-      for(i=0; i<argc; i++){
-        int n = (int)strlen(argv[i]);
-        azDequote[i] = pSpace;
-        memcpy(pSpace, argv[i], n+1);
-        sqlite3Fts3Dequote(pSpace);
-        pSpace += (n+1);
-      }
+      *piIdx = iNext;
     }
   }
 
@@ -142643,5988 +145611,6988 @@ static int fts3tokDequoteArray(
 }
 
 /*
-** Schema of the tokenizer table.
-*/
-#define FTS3_TOK_SCHEMA "CREATE TABLE x(input, token, start, end, position)"
-
-/*
-** This function does all the work for both the xConnect and xCreate methods.
-** These tables have no persistent representation of their own, so xConnect
-** and xCreate are identical operations.
+** The %_segments table is declared as follows:
 **
-**   argv[0]: module name
-**   argv[1]: database name 
-**   argv[2]: table name
-**   argv[3]: first argument (tokenizer name)
+**   CREATE TABLE %_segments(blockid INTEGER PRIMARY KEY, block BLOB)
+**
+** This function reads data from a single row of the %_segments table. The
+** specific row is identified by the iBlockid parameter. If paBlob is not
+** NULL, then a buffer is allocated using sqlite3_malloc() and populated
+** with the contents of the blob stored in the "block" column of the 
+** identified table row is. Whether or not paBlob is NULL, *pnBlob is set
+** to the size of the blob in bytes before returning.
+**
+** If an error occurs, or the table does not contain the specified row,
+** an SQLite error code is returned. Otherwise, SQLITE_OK is returned. If
+** paBlob is non-NULL, then it is the responsibility of the caller to
+** eventually free the returned buffer.
+**
+** This function may leave an open sqlite3_blob* handle in the
+** Fts3Table.pSegments variable. This handle is reused by subsequent calls
+** to this function. The handle may be closed by calling the
+** sqlite3Fts3SegmentsClose() function. Reusing a blob handle is a handy
+** performance improvement, but the blob handle should always be closed
+** before control is returned to the user (to prevent a lock being held
+** on the database file for longer than necessary). Thus, any virtual table
+** method (xFilter etc.) that may directly or indirectly call this function
+** must call sqlite3Fts3SegmentsClose() before returning.
 */
-static int fts3tokConnectMethod(
-  sqlite3 *db,                    /* Database connection */
-  void *pHash,                    /* Hash table of tokenizers */
-  int argc,                       /* Number of elements in argv array */
-  const char * const *argv,       /* xCreate/xConnect argument array */
-  sqlite3_vtab **ppVtab,          /* OUT: New sqlite3_vtab object */
-  char **pzErr                    /* OUT: sqlite3_malloc'd error message */
+SQLITE_PRIVATE int sqlite3Fts3ReadBlock(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iBlockid,         /* Access the row with blockid=$iBlockid */
+  char **paBlob,                  /* OUT: Blob data in malloc'd buffer */
+  int *pnBlob,                    /* OUT: Size of blob data */
+  int *pnLoad                     /* OUT: Bytes actually loaded */
 ){
-  Fts3tokTable *pTab = 0;
-  const sqlite3_tokenizer_module *pMod = 0;
-  sqlite3_tokenizer *pTok = 0;
-  int rc;
-  char **azDequote = 0;
-  int nDequote;
-
-  rc = sqlite3_declare_vtab(db, FTS3_TOK_SCHEMA);
-  if( rc!=SQLITE_OK ) return rc;
+  int rc;                         /* Return code */
 
-  nDequote = argc-3;
-  rc = fts3tokDequoteArray(nDequote, &argv[3], &azDequote);
+  /* pnBlob must be non-NULL. paBlob may be NULL or non-NULL. */
+  assert( pnBlob );
 
-  if( rc==SQLITE_OK ){
-    const char *zModule;
-    if( nDequote<1 ){
-      zModule = "simple";
-    }else{
-      zModule = azDequote[0];
+  if( p->pSegments ){
+    rc = sqlite3_blob_reopen(p->pSegments, iBlockid);
+  }else{
+    if( 0==p->zSegmentsTbl ){
+      p->zSegmentsTbl = sqlite3_mprintf("%s_segments", p->zName);
+      if( 0==p->zSegmentsTbl ) return SQLITE_NOMEM;
     }
-    rc = fts3tokQueryTokenizer((Fts3Hash*)pHash, zModule, &pMod, pzErr);
-  }
-
-  assert( (rc==SQLITE_OK)==(pMod!=0) );
-  if( rc==SQLITE_OK ){
-    const char * const *azArg = (const char * const *)&azDequote[1];
-    rc = pMod->xCreate((nDequote>1 ? nDequote-1 : 0), azArg, &pTok);
+    rc = sqlite3_blob_open(
+       p->db, p->zDb, p->zSegmentsTbl, "block", iBlockid, 0, &p->pSegments
+    );
   }
 
   if( rc==SQLITE_OK ){
-    pTab = (Fts3tokTable *)sqlite3_malloc(sizeof(Fts3tokTable));
-    if( pTab==0 ){
-      rc = SQLITE_NOMEM;
+    int nByte = sqlite3_blob_bytes(p->pSegments);
+    *pnBlob = nByte;
+    if( paBlob ){
+      char *aByte = sqlite3_malloc(nByte + FTS3_NODE_PADDING);
+      if( !aByte ){
+        rc = SQLITE_NOMEM;
+      }else{
+        if( pnLoad && nByte>(FTS3_NODE_CHUNK_THRESHOLD) ){
+          nByte = FTS3_NODE_CHUNKSIZE;
+          *pnLoad = nByte;
+        }
+        rc = sqlite3_blob_read(p->pSegments, aByte, nByte, 0);
+        memset(&aByte[nByte], 0, FTS3_NODE_PADDING);
+        if( rc!=SQLITE_OK ){
+          sqlite3_free(aByte);
+          aByte = 0;
+        }
+      }
+      *paBlob = aByte;
     }
   }
 
+  return rc;
+}
+
+/*
+** Close the blob handle at p->pSegments, if it is open. See comments above
+** the sqlite3Fts3ReadBlock() function for details.
+*/
+SQLITE_PRIVATE void sqlite3Fts3SegmentsClose(Fts3Table *p){
+  sqlite3_blob_close(p->pSegments);
+  p->pSegments = 0;
+}
+    
+static int fts3SegReaderIncrRead(Fts3SegReader *pReader){
+  int nRead;                      /* Number of bytes to read */
+  int rc;                         /* Return code */
+
+  nRead = MIN(pReader->nNode - pReader->nPopulate, FTS3_NODE_CHUNKSIZE);
+  rc = sqlite3_blob_read(
+      pReader->pBlob, 
+      &pReader->aNode[pReader->nPopulate],
+      nRead,
+      pReader->nPopulate
+  );
+
   if( rc==SQLITE_OK ){
-    memset(pTab, 0, sizeof(Fts3tokTable));
-    pTab->pMod = pMod;
-    pTab->pTok = pTok;
-    *ppVtab = &pTab->base;
-  }else{
-    if( pTok ){
-      pMod->xDestroy(pTok);
+    pReader->nPopulate += nRead;
+    memset(&pReader->aNode[pReader->nPopulate], 0, FTS3_NODE_PADDING);
+    if( pReader->nPopulate==pReader->nNode ){
+      sqlite3_blob_close(pReader->pBlob);
+      pReader->pBlob = 0;
+      pReader->nPopulate = 0;
     }
   }
+  return rc;
+}
 
-  sqlite3_free(azDequote);
+static int fts3SegReaderRequire(Fts3SegReader *pReader, char *pFrom, int nByte){
+  int rc = SQLITE_OK;
+  assert( !pReader->pBlob 
+       || (pFrom>=pReader->aNode && pFrom<&pReader->aNode[pReader->nNode])
+  );
+  while( pReader->pBlob && rc==SQLITE_OK 
+     &&  (pFrom - pReader->aNode + nByte)>pReader->nPopulate
+  ){
+    rc = fts3SegReaderIncrRead(pReader);
+  }
   return rc;
 }
 
 /*
-** This function does the work for both the xDisconnect and xDestroy methods.
-** These tables have no persistent representation of their own, so xDisconnect
-** and xDestroy are identical operations.
+** Set an Fts3SegReader cursor to point at EOF.
 */
-static int fts3tokDisconnectMethod(sqlite3_vtab *pVtab){
-  Fts3tokTable *pTab = (Fts3tokTable *)pVtab;
-
-  pTab->pMod->xDestroy(pTab->pTok);
-  sqlite3_free(pTab);
-  return SQLITE_OK;
+static void fts3SegReaderSetEof(Fts3SegReader *pSeg){
+  if( !fts3SegReaderIsRootOnly(pSeg) ){
+    sqlite3_free(pSeg->aNode);
+    sqlite3_blob_close(pSeg->pBlob);
+    pSeg->pBlob = 0;
+  }
+  pSeg->aNode = 0;
 }
 
 /*
-** xBestIndex - Analyze a WHERE and ORDER BY clause.
+** Move the iterator passed as the first argument to the next term in the
+** segment. If successful, SQLITE_OK is returned. If there is no next term,
+** SQLITE_DONE. Otherwise, an SQLite error code.
 */
-static int fts3tokBestIndexMethod(
-  sqlite3_vtab *pVTab, 
-  sqlite3_index_info *pInfo
+static int fts3SegReaderNext(
+  Fts3Table *p, 
+  Fts3SegReader *pReader,
+  int bIncr
 ){
-  int i;
-  UNUSED_PARAMETER(pVTab);
+  int rc;                         /* Return code of various sub-routines */
+  char *pNext;                    /* Cursor variable */
+  int nPrefix;                    /* Number of bytes in term prefix */
+  int nSuffix;                    /* Number of bytes in term suffix */
 
-  for(i=0; i<pInfo->nConstraint; i++){
-    if( pInfo->aConstraint[i].usable 
-     && pInfo->aConstraint[i].iColumn==0 
-     && pInfo->aConstraint[i].op==SQLITE_INDEX_CONSTRAINT_EQ 
-    ){
-      pInfo->idxNum = 1;
-      pInfo->aConstraintUsage[i].argvIndex = 1;
-      pInfo->aConstraintUsage[i].omit = 1;
-      pInfo->estimatedCost = 1;
+  if( !pReader->aDoclist ){
+    pNext = pReader->aNode;
+  }else{
+    pNext = &pReader->aDoclist[pReader->nDoclist];
+  }
+
+  if( !pNext || pNext>=&pReader->aNode[pReader->nNode] ){
+
+    if( fts3SegReaderIsPending(pReader) ){
+      Fts3HashElem *pElem = *(pReader->ppNextElem);
+      if( pElem==0 ){
+        pReader->aNode = 0;
+      }else{
+        PendingList *pList = (PendingList *)fts3HashData(pElem);
+        pReader->zTerm = (char *)fts3HashKey(pElem);
+        pReader->nTerm = fts3HashKeysize(pElem);
+        pReader->nNode = pReader->nDoclist = pList->nData + 1;
+        pReader->aNode = pReader->aDoclist = pList->aData;
+        pReader->ppNextElem++;
+        assert( pReader->aNode );
+      }
       return SQLITE_OK;
     }
-  }
 
-  pInfo->idxNum = 0;
-  assert( pInfo->estimatedCost>1000000.0 );
+    fts3SegReaderSetEof(pReader);
 
-  return SQLITE_OK;
-}
+    /* If iCurrentBlock>=iLeafEndBlock, this is an EOF condition. All leaf 
+    ** blocks have already been traversed.  */
+    assert( pReader->iCurrentBlock<=pReader->iLeafEndBlock );
+    if( pReader->iCurrentBlock>=pReader->iLeafEndBlock ){
+      return SQLITE_OK;
+    }
 
-/*
-** xOpen - Open a cursor.
-*/
-static int fts3tokOpenMethod(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCsr){
-  Fts3tokCursor *pCsr;
-  UNUSED_PARAMETER(pVTab);
+    rc = sqlite3Fts3ReadBlock(
+        p, ++pReader->iCurrentBlock, &pReader->aNode, &pReader->nNode, 
+        (bIncr ? &pReader->nPopulate : 0)
+    );
+    if( rc!=SQLITE_OK ) return rc;
+    assert( pReader->pBlob==0 );
+    if( bIncr && pReader->nPopulate<pReader->nNode ){
+      pReader->pBlob = p->pSegments;
+      p->pSegments = 0;
+    }
+    pNext = pReader->aNode;
+  }
 
-  pCsr = (Fts3tokCursor *)sqlite3_malloc(sizeof(Fts3tokCursor));
-  if( pCsr==0 ){
-    return SQLITE_NOMEM;
+  assert( !fts3SegReaderIsPending(pReader) );
+
+  rc = fts3SegReaderRequire(pReader, pNext, FTS3_VARINT_MAX*2);
+  if( rc!=SQLITE_OK ) return rc;
+  
+  /* Because of the FTS3_NODE_PADDING bytes of padding, the following is 
+  ** safe (no risk of overread) even if the node data is corrupted. */
+  pNext += fts3GetVarint32(pNext, &nPrefix);
+  pNext += fts3GetVarint32(pNext, &nSuffix);
+  if( nPrefix<0 || nSuffix<=0 
+   || &pNext[nSuffix]>&pReader->aNode[pReader->nNode] 
+  ){
+    return FTS_CORRUPT_VTAB;
   }
-  memset(pCsr, 0, sizeof(Fts3tokCursor));
 
-  *ppCsr = (sqlite3_vtab_cursor *)pCsr;
+  if( nPrefix+nSuffix>pReader->nTermAlloc ){
+    int nNew = (nPrefix+nSuffix)*2;
+    char *zNew = sqlite3_realloc(pReader->zTerm, nNew);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    pReader->zTerm = zNew;
+    pReader->nTermAlloc = nNew;
+  }
+
+  rc = fts3SegReaderRequire(pReader, pNext, nSuffix+FTS3_VARINT_MAX);
+  if( rc!=SQLITE_OK ) return rc;
+
+  memcpy(&pReader->zTerm[nPrefix], pNext, nSuffix);
+  pReader->nTerm = nPrefix+nSuffix;
+  pNext += nSuffix;
+  pNext += fts3GetVarint32(pNext, &pReader->nDoclist);
+  pReader->aDoclist = pNext;
+  pReader->pOffsetList = 0;
+
+  /* Check that the doclist does not appear to extend past the end of the
+  ** b-tree node. And that the final byte of the doclist is 0x00. If either 
+  ** of these statements is untrue, then the data structure is corrupt.
+  */
+  if( &pReader->aDoclist[pReader->nDoclist]>&pReader->aNode[pReader->nNode] 
+   || (pReader->nPopulate==0 && pReader->aDoclist[pReader->nDoclist-1])
+  ){
+    return FTS_CORRUPT_VTAB;
+  }
   return SQLITE_OK;
 }
 
 /*
-** Reset the tokenizer cursor passed as the only argument. As if it had
-** just been returned by fts3tokOpenMethod().
+** Set the SegReader to point to the first docid in the doclist associated
+** with the current term.
 */
-static void fts3tokResetCursor(Fts3tokCursor *pCsr){
-  if( pCsr->pCsr ){
-    Fts3tokTable *pTab = (Fts3tokTable *)(pCsr->base.pVtab);
-    pTab->pMod->xClose(pCsr->pCsr);
-    pCsr->pCsr = 0;
+static int fts3SegReaderFirstDocid(Fts3Table *pTab, Fts3SegReader *pReader){
+  int rc = SQLITE_OK;
+  assert( pReader->aDoclist );
+  assert( !pReader->pOffsetList );
+  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
+    u8 bEof = 0;
+    pReader->iDocid = 0;
+    pReader->nOffsetList = 0;
+    sqlite3Fts3DoclistPrev(0,
+        pReader->aDoclist, pReader->nDoclist, &pReader->pOffsetList, 
+        &pReader->iDocid, &pReader->nOffsetList, &bEof
+    );
+  }else{
+    rc = fts3SegReaderRequire(pReader, pReader->aDoclist, FTS3_VARINT_MAX);
+    if( rc==SQLITE_OK ){
+      int n = sqlite3Fts3GetVarint(pReader->aDoclist, &pReader->iDocid);
+      pReader->pOffsetList = &pReader->aDoclist[n];
+    }
   }
-  sqlite3_free(pCsr->zInput);
-  pCsr->zInput = 0;
-  pCsr->zToken = 0;
-  pCsr->nToken = 0;
-  pCsr->iStart = 0;
-  pCsr->iEnd = 0;
-  pCsr->iPos = 0;
-  pCsr->iRowid = 0;
+  return rc;
 }
 
 /*
-** xClose - Close a cursor.
+** Advance the SegReader to point to the next docid in the doclist
+** associated with the current term.
+** 
+** If arguments ppOffsetList and pnOffsetList are not NULL, then 
+** *ppOffsetList is set to point to the first column-offset list
+** in the doclist entry (i.e. immediately past the docid varint).
+** *pnOffsetList is set to the length of the set of column-offset
+** lists, not including the nul-terminator byte. For example:
 */
-static int fts3tokCloseMethod(sqlite3_vtab_cursor *pCursor){
-  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+static int fts3SegReaderNextDocid(
+  Fts3Table *pTab,
+  Fts3SegReader *pReader,         /* Reader to advance to next docid */
+  char **ppOffsetList,            /* OUT: Pointer to current position-list */
+  int *pnOffsetList               /* OUT: Length of *ppOffsetList in bytes */
+){
+  int rc = SQLITE_OK;
+  char *p = pReader->pOffsetList;
+  char c = 0;
 
-  fts3tokResetCursor(pCsr);
-  sqlite3_free(pCsr);
-  return SQLITE_OK;
-}
+  assert( p );
 
-/*
-** xNext - Advance the cursor to the next row, if any.
-*/
-static int fts3tokNextMethod(sqlite3_vtab_cursor *pCursor){
-  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
-  Fts3tokTable *pTab = (Fts3tokTable *)(pCursor->pVtab);
-  int rc;                         /* Return code */
+  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
+    /* A pending-terms seg-reader for an FTS4 table that uses order=desc.
+    ** Pending-terms doclists are always built up in ascending order, so
+    ** we have to iterate through them backwards here. */
+    u8 bEof = 0;
+    if( ppOffsetList ){
+      *ppOffsetList = pReader->pOffsetList;
+      *pnOffsetList = pReader->nOffsetList - 1;
+    }
+    sqlite3Fts3DoclistPrev(0,
+        pReader->aDoclist, pReader->nDoclist, &p, &pReader->iDocid,
+        &pReader->nOffsetList, &bEof
+    );
+    if( bEof ){
+      pReader->pOffsetList = 0;
+    }else{
+      pReader->pOffsetList = p;
+    }
+  }else{
+    char *pEnd = &pReader->aDoclist[pReader->nDoclist];
 
-  pCsr->iRowid++;
-  rc = pTab->pMod->xNext(pCsr->pCsr,
-      &pCsr->zToken, &pCsr->nToken,
-      &pCsr->iStart, &pCsr->iEnd, &pCsr->iPos
-  );
+    /* Pointer p currently points at the first byte of an offset list. The
+    ** following block advances it to point one byte past the end of
+    ** the same offset list. */
+    while( 1 ){
+  
+      /* The following line of code (and the "p++" below the while() loop) is
+      ** normally all that is required to move pointer p to the desired 
+      ** position. The exception is if this node is being loaded from disk
+      ** incrementally and pointer "p" now points to the first byte past
+      ** the populated part of pReader->aNode[].
+      */
+      while( *p | c ) c = *p++ & 0x80;
+      assert( *p==0 );
+  
+      if( pReader->pBlob==0 || p<&pReader->aNode[pReader->nPopulate] ) break;
+      rc = fts3SegReaderIncrRead(pReader);
+      if( rc!=SQLITE_OK ) return rc;
+    }
+    p++;
+  
+    /* If required, populate the output variables with a pointer to and the
+    ** size of the previous offset-list.
+    */
+    if( ppOffsetList ){
+      *ppOffsetList = pReader->pOffsetList;
+      *pnOffsetList = (int)(p - pReader->pOffsetList - 1);
+    }
 
-  if( rc!=SQLITE_OK ){
-    fts3tokResetCursor(pCsr);
-    if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+    /* List may have been edited in place by fts3EvalNearTrim() */
+    while( p<pEnd && *p==0 ) p++;
+  
+    /* If there are no more entries in the doclist, set pOffsetList to
+    ** NULL. Otherwise, set Fts3SegReader.iDocid to the next docid and
+    ** Fts3SegReader.pOffsetList to point to the next offset list before
+    ** returning.
+    */
+    if( p>=pEnd ){
+      pReader->pOffsetList = 0;
+    }else{
+      rc = fts3SegReaderRequire(pReader, p, FTS3_VARINT_MAX);
+      if( rc==SQLITE_OK ){
+        sqlite3_int64 iDelta;
+        pReader->pOffsetList = p + sqlite3Fts3GetVarint(p, &iDelta);
+        if( pTab->bDescIdx ){
+          pReader->iDocid -= iDelta;
+        }else{
+          pReader->iDocid += iDelta;
+        }
+      }
+    }
   }
 
-  return rc;
+  return SQLITE_OK;
 }
 
-/*
-** xFilter - Initialize a cursor to point at the start of its data.
-*/
-static int fts3tokFilterMethod(
-  sqlite3_vtab_cursor *pCursor,   /* The cursor used for this query */
-  int idxNum,                     /* Strategy index */
-  const char *idxStr,             /* Unused */
-  int nVal,                       /* Number of elements in apVal */
-  sqlite3_value **apVal           /* Arguments for the indexing scheme */
+
+SQLITE_PRIVATE int sqlite3Fts3MsrOvfl(
+  Fts3Cursor *pCsr, 
+  Fts3MultiSegReader *pMsr,
+  int *pnOvfl
 ){
-  int rc = SQLITE_ERROR;
-  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
-  Fts3tokTable *pTab = (Fts3tokTable *)(pCursor->pVtab);
-  UNUSED_PARAMETER(idxStr);
-  UNUSED_PARAMETER(nVal);
+  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
+  int nOvfl = 0;
+  int ii;
+  int rc = SQLITE_OK;
+  int pgsz = p->nPgsz;
 
-  fts3tokResetCursor(pCsr);
-  if( idxNum==1 ){
-    const char *zByte = (const char *)sqlite3_value_text(apVal[0]);
-    int nByte = sqlite3_value_bytes(apVal[0]);
-    pCsr->zInput = sqlite3_malloc(nByte+1);
-    if( pCsr->zInput==0 ){
-      rc = SQLITE_NOMEM;
-    }else{
-      memcpy(pCsr->zInput, zByte, nByte);
-      pCsr->zInput[nByte] = 0;
-      rc = pTab->pMod->xOpen(pTab->pTok, pCsr->zInput, nByte, &pCsr->pCsr);
-      if( rc==SQLITE_OK ){
-        pCsr->pCsr->pTokenizer = pTab->pTok;
+  assert( p->bFts4 );
+  assert( pgsz>0 );
+
+  for(ii=0; rc==SQLITE_OK && ii<pMsr->nSegment; ii++){
+    Fts3SegReader *pReader = pMsr->apSegment[ii];
+    if( !fts3SegReaderIsPending(pReader) 
+     && !fts3SegReaderIsRootOnly(pReader) 
+    ){
+      sqlite3_int64 jj;
+      for(jj=pReader->iStartBlock; jj<=pReader->iLeafEndBlock; jj++){
+        int nBlob;
+        rc = sqlite3Fts3ReadBlock(p, jj, 0, &nBlob, 0);
+        if( rc!=SQLITE_OK ) break;
+        if( (nBlob+35)>pgsz ){
+          nOvfl += (nBlob + 34)/pgsz;
+        }
       }
     }
   }
-
-  if( rc!=SQLITE_OK ) return rc;
-  return fts3tokNextMethod(pCursor);
+  *pnOvfl = nOvfl;
+  return rc;
 }
 
 /*
-** xEof - Return true if the cursor is at EOF, or false otherwise.
+** Free all allocations associated with the iterator passed as the 
+** second argument.
 */
-static int fts3tokEofMethod(sqlite3_vtab_cursor *pCursor){
-  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
-  return (pCsr->zToken==0);
+SQLITE_PRIVATE void sqlite3Fts3SegReaderFree(Fts3SegReader *pReader){
+  if( pReader && !fts3SegReaderIsPending(pReader) ){
+    sqlite3_free(pReader->zTerm);
+    if( !fts3SegReaderIsRootOnly(pReader) ){
+      sqlite3_free(pReader->aNode);
+      sqlite3_blob_close(pReader->pBlob);
+    }
+  }
+  sqlite3_free(pReader);
 }
 
 /*
-** xColumn - Return a column value.
+** Allocate a new SegReader object.
 */
-static int fts3tokColumnMethod(
-  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
-  sqlite3_context *pCtx,          /* Context for sqlite3_result_xxx() calls */
-  int iCol                        /* Index of column to read value from */
+SQLITE_PRIVATE int sqlite3Fts3SegReaderNew(
+  int iAge,                       /* Segment "age". */
+  int bLookup,                    /* True for a lookup only */
+  sqlite3_int64 iStartLeaf,       /* First leaf to traverse */
+  sqlite3_int64 iEndLeaf,         /* Final leaf to traverse */
+  sqlite3_int64 iEndBlock,        /* Final block of segment */
+  const char *zRoot,              /* Buffer containing root node */
+  int nRoot,                      /* Size of buffer containing root node */
+  Fts3SegReader **ppReader        /* OUT: Allocated Fts3SegReader */
 ){
-  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
+  Fts3SegReader *pReader;         /* Newly allocated SegReader object */
+  int nExtra = 0;                 /* Bytes to allocate segment root node */
 
-  /* CREATE TABLE x(input, token, start, end, position) */
-  switch( iCol ){
-    case 0:
-      sqlite3_result_text(pCtx, pCsr->zInput, -1, SQLITE_TRANSIENT);
-      break;
-    case 1:
-      sqlite3_result_text(pCtx, pCsr->zToken, pCsr->nToken, SQLITE_TRANSIENT);
-      break;
-    case 2:
-      sqlite3_result_int(pCtx, pCsr->iStart);
-      break;
-    case 3:
-      sqlite3_result_int(pCtx, pCsr->iEnd);
-      break;
-    default:
-      assert( iCol==4 );
-      sqlite3_result_int(pCtx, pCsr->iPos);
-      break;
+  assert( iStartLeaf<=iEndLeaf );
+  if( iStartLeaf==0 ){
+    nExtra = nRoot + FTS3_NODE_PADDING;
   }
-  return SQLITE_OK;
-}
 
-/*
-** xRowid - Return the current rowid for the cursor.
-*/
-static int fts3tokRowidMethod(
-  sqlite3_vtab_cursor *pCursor,   /* Cursor to retrieve value from */
-  sqlite_int64 *pRowid            /* OUT: Rowid value */
-){
-  Fts3tokCursor *pCsr = (Fts3tokCursor *)pCursor;
-  *pRowid = (sqlite3_int64)pCsr->iRowid;
+  pReader = (Fts3SegReader *)sqlite3_malloc(sizeof(Fts3SegReader) + nExtra);
+  if( !pReader ){
+    return SQLITE_NOMEM;
+  }
+  memset(pReader, 0, sizeof(Fts3SegReader));
+  pReader->iIdx = iAge;
+  pReader->bLookup = bLookup!=0;
+  pReader->iStartBlock = iStartLeaf;
+  pReader->iLeafEndBlock = iEndLeaf;
+  pReader->iEndBlock = iEndBlock;
+
+  if( nExtra ){
+    /* The entire segment is stored in the root node. */
+    pReader->aNode = (char *)&pReader[1];
+    pReader->rootOnly = 1;
+    pReader->nNode = nRoot;
+    memcpy(pReader->aNode, zRoot, nRoot);
+    memset(&pReader->aNode[nRoot], 0, FTS3_NODE_PADDING);
+  }else{
+    pReader->iCurrentBlock = iStartLeaf-1;
+  }
+  *ppReader = pReader;
   return SQLITE_OK;
 }
 
 /*
-** Register the fts3tok module with database connection db. Return SQLITE_OK
-** if successful or an error code if sqlite3_create_module() fails.
+** This is a comparison function used as a qsort() callback when sorting
+** an array of pending terms by term. This occurs as part of flushing
+** the contents of the pending-terms hash table to the database.
 */
-SQLITE_PRIVATE int sqlite3Fts3InitTok(sqlite3 *db, Fts3Hash *pHash){
-  static const sqlite3_module fts3tok_module = {
-     0,                           /* iVersion      */
-     fts3tokConnectMethod,        /* xCreate       */
-     fts3tokConnectMethod,        /* xConnect      */
-     fts3tokBestIndexMethod,      /* xBestIndex    */
-     fts3tokDisconnectMethod,     /* xDisconnect   */
-     fts3tokDisconnectMethod,     /* xDestroy      */
-     fts3tokOpenMethod,           /* xOpen         */
-     fts3tokCloseMethod,          /* xClose        */
-     fts3tokFilterMethod,         /* xFilter       */
-     fts3tokNextMethod,           /* xNext         */
-     fts3tokEofMethod,            /* xEof          */
-     fts3tokColumnMethod,         /* xColumn       */
-     fts3tokRowidMethod,          /* xRowid        */
-     0,                           /* xUpdate       */
-     0,                           /* xBegin        */
-     0,                           /* xSync         */
-     0,                           /* xCommit       */
-     0,                           /* xRollback     */
-     0,                           /* xFindFunction */
-     0,                           /* xRename       */
-     0,                           /* xSavepoint    */
-     0,                           /* xRelease      */
-     0                            /* xRollbackTo   */
-  };
-  int rc;                         /* Return code */
+static int SQLITE_CDECL fts3CompareElemByTerm(
+  const void *lhs,
+  const void *rhs
+){
+  char *z1 = fts3HashKey(*(Fts3HashElem **)lhs);
+  char *z2 = fts3HashKey(*(Fts3HashElem **)rhs);
+  int n1 = fts3HashKeysize(*(Fts3HashElem **)lhs);
+  int n2 = fts3HashKeysize(*(Fts3HashElem **)rhs);
 
-  rc = sqlite3_create_module(db, "fts3tokenize", &fts3tok_module, (void*)pHash);
-  return rc;
+  int n = (n1<n2 ? n1 : n2);
+  int c = memcmp(z1, z2, n);
+  if( c==0 ){
+    c = n1 - n2;
+  }
+  return c;
 }
 
-#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
-
-/************** End of fts3_tokenize_vtab.c **********************************/
-/************** Begin file fts3_write.c **************************************/
 /*
-** 2009 Oct 23
+** This function is used to allocate an Fts3SegReader that iterates through
+** a subset of the terms stored in the Fts3Table.pendingTerms array.
 **
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
+** If the isPrefixIter parameter is zero, then the returned SegReader iterates
+** through each term in the pending-terms table. Or, if isPrefixIter is
+** non-zero, it iterates through each term and its prefixes. For example, if
+** the pending terms hash table contains the terms "sqlite", "mysql" and
+** "firebird", then the iterator visits the following 'terms' (in the order
+** shown):
 **
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
+**   f fi fir fire fireb firebi firebir firebird
+**   m my mys mysq mysql
+**   s sq sql sqli sqlit sqlite
 **
-******************************************************************************
+** Whereas if isPrefixIter is zero, the terms visited are:
 **
-** This file is part of the SQLite FTS3 extension module. Specifically,
-** this file contains code to insert, update and delete rows from FTS3
-** tables. It also contains code to merge FTS3 b-tree segments. Some
-** of the sub-routines used to merge segments are also used by the query 
-** code in fts3.c.
+**   firebird mysql sqlite
 */
+SQLITE_PRIVATE int sqlite3Fts3SegReaderPending(
+  Fts3Table *p,                   /* Virtual table handle */
+  int iIndex,                     /* Index for p->aIndex */
+  const char *zTerm,              /* Term to search for */
+  int nTerm,                      /* Size of buffer zTerm */
+  int bPrefix,                    /* True for a prefix iterator */
+  Fts3SegReader **ppReader        /* OUT: SegReader for pending-terms */
+){
+  Fts3SegReader *pReader = 0;     /* Fts3SegReader object to return */
+  Fts3HashElem *pE;               /* Iterator variable */
+  Fts3HashElem **aElem = 0;       /* Array of term hash entries to scan */
+  int nElem = 0;                  /* Size of array at aElem */
+  int rc = SQLITE_OK;             /* Return Code */
+  Fts3Hash *pHash;
 
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+  pHash = &p->aIndex[iIndex].hPending;
+  if( bPrefix ){
+    int nAlloc = 0;               /* Size of allocated array at aElem */
 
-/* #include <string.h> */
-/* #include <assert.h> */
-/* #include <stdlib.h> */
+    for(pE=fts3HashFirst(pHash); pE; pE=fts3HashNext(pE)){
+      char *zKey = (char *)fts3HashKey(pE);
+      int nKey = fts3HashKeysize(pE);
+      if( nTerm==0 || (nKey>=nTerm && 0==memcmp(zKey, zTerm, nTerm)) ){
+        if( nElem==nAlloc ){
+          Fts3HashElem **aElem2;
+          nAlloc += 16;
+          aElem2 = (Fts3HashElem **)sqlite3_realloc(
+              aElem, nAlloc*sizeof(Fts3HashElem *)
+          );
+          if( !aElem2 ){
+            rc = SQLITE_NOMEM;
+            nElem = 0;
+            break;
+          }
+          aElem = aElem2;
+        }
+
+        aElem[nElem++] = pE;
+      }
+    }
 
+    /* If more than one term matches the prefix, sort the Fts3HashElem
+    ** objects in term order using qsort(). This uses the same comparison
+    ** callback as is used when flushing terms to disk.
+    */
+    if( nElem>1 ){
+      qsort(aElem, nElem, sizeof(Fts3HashElem *), fts3CompareElemByTerm);
+    }
 
-#define FTS_MAX_APPENDABLE_HEIGHT 16
+  }else{
+    /* The query is a simple term lookup that matches at most one term in
+    ** the index. All that is required is a straight hash-lookup. 
+    **
+    ** Because the stack address of pE may be accessed via the aElem pointer
+    ** below, the "Fts3HashElem *pE" must be declared so that it is valid
+    ** within this entire function, not just this "else{...}" block.
+    */
+    pE = fts3HashFindElem(pHash, zTerm, nTerm);
+    if( pE ){
+      aElem = &pE;
+      nElem = 1;
+    }
+  }
+
+  if( nElem>0 ){
+    int nByte = sizeof(Fts3SegReader) + (nElem+1)*sizeof(Fts3HashElem *);
+    pReader = (Fts3SegReader *)sqlite3_malloc(nByte);
+    if( !pReader ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memset(pReader, 0, nByte);
+      pReader->iIdx = 0x7FFFFFFF;
+      pReader->ppNextElem = (Fts3HashElem **)&pReader[1];
+      memcpy(pReader->ppNextElem, aElem, nElem*sizeof(Fts3HashElem *));
+    }
+  }
+
+  if( bPrefix ){
+    sqlite3_free(aElem);
+  }
+  *ppReader = pReader;
+  return rc;
+}
 
 /*
-** When full-text index nodes are loaded from disk, the buffer that they
-** are loaded into has the following number of bytes of padding at the end 
-** of it. i.e. if a full-text index node is 900 bytes in size, then a buffer
-** of 920 bytes is allocated for it.
+** Compare the entries pointed to by two Fts3SegReader structures. 
+** Comparison is as follows:
 **
-** This means that if we have a pointer into a buffer containing node data,
-** it is always safe to read up to two varints from it without risking an
-** overread, even if the node data is corrupted.
+**   1) EOF is greater than not EOF.
+**
+**   2) The current terms (if any) are compared using memcmp(). If one
+**      term is a prefix of another, the longer term is considered the
+**      larger.
+**
+**   3) By segment age. An older segment is considered larger.
 */
-#define FTS3_NODE_PADDING (FTS3_VARINT_MAX*2)
+static int fts3SegReaderCmp(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
+  int rc;
+  if( pLhs->aNode && pRhs->aNode ){
+    int rc2 = pLhs->nTerm - pRhs->nTerm;
+    if( rc2<0 ){
+      rc = memcmp(pLhs->zTerm, pRhs->zTerm, pLhs->nTerm);
+    }else{
+      rc = memcmp(pLhs->zTerm, pRhs->zTerm, pRhs->nTerm);
+    }
+    if( rc==0 ){
+      rc = rc2;
+    }
+  }else{
+    rc = (pLhs->aNode==0) - (pRhs->aNode==0);
+  }
+  if( rc==0 ){
+    rc = pRhs->iIdx - pLhs->iIdx;
+  }
+  assert( rc!=0 );
+  return rc;
+}
 
 /*
-** Under certain circumstances, b-tree nodes (doclists) can be loaded into
-** memory incrementally instead of all at once. This can be a big performance
-** win (reduced IO and CPU) if SQLite stops calling the virtual table xNext()
-** method before retrieving all query results (as may happen, for example,
-** if a query has a LIMIT clause).
+** A different comparison function for SegReader structures. In this
+** version, it is assumed that each SegReader points to an entry in
+** a doclist for identical terms. Comparison is made as follows:
 **
-** Incremental loading is used for b-tree nodes FTS3_NODE_CHUNK_THRESHOLD 
-** bytes and larger. Nodes are loaded in chunks of FTS3_NODE_CHUNKSIZE bytes.
-** The code is written so that the hard lower-limit for each of these values 
-** is 1. Clearly such small values would be inefficient, but can be useful 
-** for testing purposes.
+**   1) EOF (end of doclist in this case) is greater than not EOF.
 **
-** If this module is built with SQLITE_TEST defined, these constants may
-** be overridden at runtime for testing purposes. File fts3_test.c contains
-** a Tcl interface to read and write the values.
+**   2) By current docid.
+**
+**   3) By segment age. An older segment is considered larger.
 */
-#ifdef SQLITE_TEST
-int test_fts3_node_chunksize = (4*1024);
-int test_fts3_node_chunk_threshold = (4*1024)*4;
-# define FTS3_NODE_CHUNKSIZE       test_fts3_node_chunksize
-# define FTS3_NODE_CHUNK_THRESHOLD test_fts3_node_chunk_threshold
-#else
-# define FTS3_NODE_CHUNKSIZE (4*1024) 
-# define FTS3_NODE_CHUNK_THRESHOLD (FTS3_NODE_CHUNKSIZE*4)
-#endif
+static int fts3SegReaderDoclistCmp(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
+  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
+  if( rc==0 ){
+    if( pLhs->iDocid==pRhs->iDocid ){
+      rc = pRhs->iIdx - pLhs->iIdx;
+    }else{
+      rc = (pLhs->iDocid > pRhs->iDocid) ? 1 : -1;
+    }
+  }
+  assert( pLhs->aNode && pRhs->aNode );
+  return rc;
+}
+static int fts3SegReaderDoclistCmpRev(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
+  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
+  if( rc==0 ){
+    if( pLhs->iDocid==pRhs->iDocid ){
+      rc = pRhs->iIdx - pLhs->iIdx;
+    }else{
+      rc = (pLhs->iDocid < pRhs->iDocid) ? 1 : -1;
+    }
+  }
+  assert( pLhs->aNode && pRhs->aNode );
+  return rc;
+}
 
 /*
-** The two values that may be meaningfully bound to the :1 parameter in
-** statements SQL_REPLACE_STAT and SQL_SELECT_STAT.
+** Compare the term that the Fts3SegReader object passed as the first argument
+** points to with the term specified by arguments zTerm and nTerm. 
+**
+** If the pSeg iterator is already at EOF, return 0. Otherwise, return
+** -ve if the pSeg term is less than zTerm/nTerm, 0 if the two terms are
+** equal, or +ve if the pSeg term is greater than zTerm/nTerm.
 */
-#define FTS_STAT_DOCTOTAL      0
-#define FTS_STAT_INCRMERGEHINT 1
-#define FTS_STAT_AUTOINCRMERGE 2
+static int fts3SegReaderTermCmp(
+  Fts3SegReader *pSeg,            /* Segment reader object */
+  const char *zTerm,              /* Term to compare to */
+  int nTerm                       /* Size of term zTerm in bytes */
+){
+  int res = 0;
+  if( pSeg->aNode ){
+    if( pSeg->nTerm>nTerm ){
+      res = memcmp(pSeg->zTerm, zTerm, nTerm);
+    }else{
+      res = memcmp(pSeg->zTerm, zTerm, pSeg->nTerm);
+    }
+    if( res==0 ){
+      res = pSeg->nTerm-nTerm;
+    }
+  }
+  return res;
+}
 
 /*
-** If FTS_LOG_MERGES is defined, call sqlite3_log() to report each automatic
-** and incremental merge operation that takes place. This is used for 
-** debugging FTS only, it should not usually be turned on in production
-** systems.
+** Argument apSegment is an array of nSegment elements. It is known that
+** the final (nSegment-nSuspect) members are already in sorted order
+** (according to the comparison function provided). This function shuffles
+** the array around until all entries are in sorted order.
 */
-#ifdef FTS3_LOG_MERGES
-static void fts3LogMerge(int nMerge, sqlite3_int64 iAbsLevel){
-  sqlite3_log(SQLITE_OK, "%d-way merge from level %d", nMerge, (int)iAbsLevel);
-}
-#else
-#define fts3LogMerge(x, y)
-#endif
+static void fts3SegReaderSort(
+  Fts3SegReader **apSegment,                     /* Array to sort entries of */
+  int nSegment,                                  /* Size of apSegment array */
+  int nSuspect,                                  /* Unsorted entry count */
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *)  /* Comparison function */
+){
+  int i;                          /* Iterator variable */
 
+  assert( nSuspect<=nSegment );
 
-typedef struct PendingList PendingList;
-typedef struct SegmentNode SegmentNode;
-typedef struct SegmentWriter SegmentWriter;
+  if( nSuspect==nSegment ) nSuspect--;
+  for(i=nSuspect-1; i>=0; i--){
+    int j;
+    for(j=i; j<(nSegment-1); j++){
+      Fts3SegReader *pTmp;
+      if( xCmp(apSegment[j], apSegment[j+1])<0 ) break;
+      pTmp = apSegment[j+1];
+      apSegment[j+1] = apSegment[j];
+      apSegment[j] = pTmp;
+    }
+  }
+
+#ifndef NDEBUG
+  /* Check that the list really is sorted now. */
+  for(i=0; i<(nSuspect-1); i++){
+    assert( xCmp(apSegment[i], apSegment[i+1])<0 );
+  }
+#endif
+}
+
+/* 
+** Insert a record into the %_segments table.
+*/
+static int fts3WriteSegment(
+  Fts3Table *p,                   /* Virtual table handle */
+  sqlite3_int64 iBlock,           /* Block id for new block */
+  char *z,                        /* Pointer to buffer containing block data */
+  int n                           /* Size of buffer z in bytes */
+){
+  sqlite3_stmt *pStmt;
+  int rc = fts3SqlStmt(p, SQL_INSERT_SEGMENTS, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pStmt, 1, iBlock);
+    sqlite3_bind_blob(pStmt, 2, z, n, SQLITE_STATIC);
+    sqlite3_step(pStmt);
+    rc = sqlite3_reset(pStmt);
+  }
+  return rc;
+}
 
 /*
-** An instance of the following data structure is used to build doclists
-** incrementally. See function fts3PendingListAppend() for details.
+** Find the largest relative level number in the table. If successful, set
+** *pnMax to this value and return SQLITE_OK. Otherwise, if an error occurs,
+** set *pnMax to zero and return an SQLite error code.
 */
-struct PendingList {
-  int nData;
-  char *aData;
-  int nSpace;
-  sqlite3_int64 iLastDocid;
-  sqlite3_int64 iLastCol;
-  sqlite3_int64 iLastPos;
-};
+SQLITE_PRIVATE int sqlite3Fts3MaxLevel(Fts3Table *p, int *pnMax){
+  int rc;
+  int mxLevel = 0;
+  sqlite3_stmt *pStmt = 0;
+
+  rc = fts3SqlStmt(p, SQL_SELECT_MXLEVEL, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    if( SQLITE_ROW==sqlite3_step(pStmt) ){
+      mxLevel = sqlite3_column_int(pStmt, 0);
+    }
+    rc = sqlite3_reset(pStmt);
+  }
+  *pnMax = mxLevel;
+  return rc;
+}
+
+/* 
+** Insert a record into the %_segdir table.
+*/
+static int fts3WriteSegdir(
+  Fts3Table *p,                   /* Virtual table handle */
+  sqlite3_int64 iLevel,           /* Value for "level" field (absolute level) */
+  int iIdx,                       /* Value for "idx" field */
+  sqlite3_int64 iStartBlock,      /* Value for "start_block" field */
+  sqlite3_int64 iLeafEndBlock,    /* Value for "leaves_end_block" field */
+  sqlite3_int64 iEndBlock,        /* Value for "end_block" field */
+  sqlite3_int64 nLeafData,        /* Bytes of leaf data in segment */
+  char *zRoot,                    /* Blob value for "root" field */
+  int nRoot                       /* Number of bytes in buffer zRoot */
+){
+  sqlite3_stmt *pStmt;
+  int rc = fts3SqlStmt(p, SQL_INSERT_SEGDIR, &pStmt, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pStmt, 1, iLevel);
+    sqlite3_bind_int(pStmt, 2, iIdx);
+    sqlite3_bind_int64(pStmt, 3, iStartBlock);
+    sqlite3_bind_int64(pStmt, 4, iLeafEndBlock);
+    if( nLeafData==0 ){
+      sqlite3_bind_int64(pStmt, 5, iEndBlock);
+    }else{
+      char *zEnd = sqlite3_mprintf("%lld %lld", iEndBlock, nLeafData);
+      if( !zEnd ) return SQLITE_NOMEM;
+      sqlite3_bind_text(pStmt, 5, zEnd, -1, sqlite3_free);
+    }
+    sqlite3_bind_blob(pStmt, 6, zRoot, nRoot, SQLITE_STATIC);
+    sqlite3_step(pStmt);
+    rc = sqlite3_reset(pStmt);
+  }
+  return rc;
+}
 
+/*
+** Return the size of the common prefix (if any) shared by zPrev and
+** zNext, in bytes. For example, 
+**
+**   fts3PrefixCompress("abc", 3, "abcdef", 6)   // returns 3
+**   fts3PrefixCompress("abX", 3, "abcdef", 6)   // returns 2
+**   fts3PrefixCompress("abX", 3, "Xbcdef", 6)   // returns 0
+*/
+static int fts3PrefixCompress(
+  const char *zPrev,              /* Buffer containing previous term */
+  int nPrev,                      /* Size of buffer zPrev in bytes */
+  const char *zNext,              /* Buffer containing next term */
+  int nNext                       /* Size of buffer zNext in bytes */
+){
+  int n;
+  UNUSED_PARAMETER(nNext);
+  for(n=0; n<nPrev && zPrev[n]==zNext[n]; n++);
+  return n;
+}
 
 /*
-** Each cursor has a (possibly empty) linked list of the following objects.
+** Add term zTerm to the SegmentNode. It is guaranteed that zTerm is larger
+** (according to memcmp) than the previous term.
 */
-struct Fts3DeferredToken {
-  Fts3PhraseToken *pToken;        /* Pointer to corresponding expr token */
-  int iCol;                       /* Column token must occur in */
-  Fts3DeferredToken *pNext;       /* Next in list of deferred tokens */
-  PendingList *pList;             /* Doclist is assembled here */
-};
+static int fts3NodeAddTerm(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentNode **ppTree,           /* IN/OUT: SegmentNode handle */ 
+  int isCopyTerm,                 /* True if zTerm/nTerm is transient */
+  const char *zTerm,              /* Pointer to buffer containing term */
+  int nTerm                       /* Size of term in bytes */
+){
+  SegmentNode *pTree = *ppTree;
+  int rc;
+  SegmentNode *pNew;
 
-/*
-** An instance of this structure is used to iterate through the terms on
-** a contiguous set of segment b-tree leaf nodes. Although the details of
-** this structure are only manipulated by code in this file, opaque handles
-** of type Fts3SegReader* are also used by code in fts3.c to iterate through
-** terms when querying the full-text index. See functions:
-**
-**   sqlite3Fts3SegReaderNew()
-**   sqlite3Fts3SegReaderFree()
-**   sqlite3Fts3SegReaderIterate()
-**
-** Methods used to manipulate Fts3SegReader structures:
-**
-**   fts3SegReaderNext()
-**   fts3SegReaderFirstDocid()
-**   fts3SegReaderNextDocid()
-*/
-struct Fts3SegReader {
-  int iIdx;                       /* Index within level, or 0x7FFFFFFF for PT */
-  u8 bLookup;                     /* True for a lookup only */
-  u8 rootOnly;                    /* True for a root-only reader */
+  /* First try to append the term to the current node. Return early if 
+  ** this is possible.
+  */
+  if( pTree ){
+    int nData = pTree->nData;     /* Current size of node in bytes */
+    int nReq = nData;             /* Required space after adding zTerm */
+    int nPrefix;                  /* Number of bytes of prefix compression */
+    int nSuffix;                  /* Suffix length */
 
-  sqlite3_int64 iStartBlock;      /* Rowid of first leaf block to traverse */
-  sqlite3_int64 iLeafEndBlock;    /* Rowid of final leaf block to traverse */
-  sqlite3_int64 iEndBlock;        /* Rowid of final block in segment (or 0) */
-  sqlite3_int64 iCurrentBlock;    /* Current leaf block (or 0) */
+    nPrefix = fts3PrefixCompress(pTree->zTerm, pTree->nTerm, zTerm, nTerm);
+    nSuffix = nTerm-nPrefix;
 
-  char *aNode;                    /* Pointer to node data (or NULL) */
-  int nNode;                      /* Size of buffer at aNode (or 0) */
-  int nPopulate;                  /* If >0, bytes of buffer aNode[] loaded */
-  sqlite3_blob *pBlob;            /* If not NULL, blob handle to read node */
+    nReq += sqlite3Fts3VarintLen(nPrefix)+sqlite3Fts3VarintLen(nSuffix)+nSuffix;
+    if( nReq<=p->nNodeSize || !pTree->zTerm ){
 
-  Fts3HashElem **ppNextElem;
+      if( nReq>p->nNodeSize ){
+        /* An unusual case: this is the first term to be added to the node
+        ** and the static node buffer (p->nNodeSize bytes) is not large
+        ** enough. Use a separately malloced buffer instead This wastes
+        ** p->nNodeSize bytes, but since this scenario only comes about when
+        ** the database contain two terms that share a prefix of almost 2KB, 
+        ** this is not expected to be a serious problem. 
+        */
+        assert( pTree->aData==(char *)&pTree[1] );
+        pTree->aData = (char *)sqlite3_malloc(nReq);
+        if( !pTree->aData ){
+          return SQLITE_NOMEM;
+        }
+      }
 
-  /* Variables set by fts3SegReaderNext(). These may be read directly
-  ** by the caller. They are valid from the time SegmentReaderNew() returns
-  ** until SegmentReaderNext() returns something other than SQLITE_OK
-  ** (i.e. SQLITE_DONE).
-  */
-  int nTerm;                      /* Number of bytes in current term */
-  char *zTerm;                    /* Pointer to current term */
-  int nTermAlloc;                 /* Allocated size of zTerm buffer */
-  char *aDoclist;                 /* Pointer to doclist of current entry */
-  int nDoclist;                   /* Size of doclist in current entry */
+      if( pTree->zTerm ){
+        /* There is no prefix-length field for first term in a node */
+        nData += sqlite3Fts3PutVarint(&pTree->aData[nData], nPrefix);
+      }
 
-  /* The following variables are used by fts3SegReaderNextDocid() to iterate 
-  ** through the current doclist (aDoclist/nDoclist).
+      nData += sqlite3Fts3PutVarint(&pTree->aData[nData], nSuffix);
+      memcpy(&pTree->aData[nData], &zTerm[nPrefix], nSuffix);
+      pTree->nData = nData + nSuffix;
+      pTree->nEntry++;
+
+      if( isCopyTerm ){
+        if( pTree->nMalloc<nTerm ){
+          char *zNew = sqlite3_realloc(pTree->zMalloc, nTerm*2);
+          if( !zNew ){
+            return SQLITE_NOMEM;
+          }
+          pTree->nMalloc = nTerm*2;
+          pTree->zMalloc = zNew;
+        }
+        pTree->zTerm = pTree->zMalloc;
+        memcpy(pTree->zTerm, zTerm, nTerm);
+        pTree->nTerm = nTerm;
+      }else{
+        pTree->zTerm = (char *)zTerm;
+        pTree->nTerm = nTerm;
+      }
+      return SQLITE_OK;
+    }
+  }
+
+  /* If control flows to here, it was not possible to append zTerm to the
+  ** current node. Create a new node (a right-sibling of the current node).
+  ** If this is the first node in the tree, the term is added to it.
+  **
+  ** Otherwise, the term is not added to the new node, it is left empty for
+  ** now. Instead, the term is inserted into the parent of pTree. If pTree 
+  ** has no parent, one is created here.
   */
-  char *pOffsetList;
-  int nOffsetList;                /* For descending pending seg-readers only */
-  sqlite3_int64 iDocid;
-};
+  pNew = (SegmentNode *)sqlite3_malloc(sizeof(SegmentNode) + p->nNodeSize);
+  if( !pNew ){
+    return SQLITE_NOMEM;
+  }
+  memset(pNew, 0, sizeof(SegmentNode));
+  pNew->nData = 1 + FTS3_VARINT_MAX;
+  pNew->aData = (char *)&pNew[1];
 
-#define fts3SegReaderIsPending(p) ((p)->ppNextElem!=0)
-#define fts3SegReaderIsRootOnly(p) ((p)->rootOnly!=0)
+  if( pTree ){
+    SegmentNode *pParent = pTree->pParent;
+    rc = fts3NodeAddTerm(p, &pParent, isCopyTerm, zTerm, nTerm);
+    if( pTree->pParent==0 ){
+      pTree->pParent = pParent;
+    }
+    pTree->pRight = pNew;
+    pNew->pLeftmost = pTree->pLeftmost;
+    pNew->pParent = pParent;
+    pNew->zMalloc = pTree->zMalloc;
+    pNew->nMalloc = pTree->nMalloc;
+    pTree->zMalloc = 0;
+  }else{
+    pNew->pLeftmost = pNew;
+    rc = fts3NodeAddTerm(p, &pNew, isCopyTerm, zTerm, nTerm); 
+  }
+
+  *ppTree = pNew;
+  return rc;
+}
 
 /*
-** An instance of this structure is used to create a segment b-tree in the
-** database. The internal details of this type are only accessed by the
-** following functions:
-**
-**   fts3SegWriterAdd()
-**   fts3SegWriterFlush()
-**   fts3SegWriterFree()
+** Helper function for fts3NodeWrite().
 */
-struct SegmentWriter {
-  SegmentNode *pTree;             /* Pointer to interior tree structure */
-  sqlite3_int64 iFirst;           /* First slot in %_segments written */
-  sqlite3_int64 iFree;            /* Next free slot in %_segments */
-  char *zTerm;                    /* Pointer to previous term buffer */
-  int nTerm;                      /* Number of bytes in zTerm */
-  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
-  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
-  int nSize;                      /* Size of allocation at aData */
-  int nData;                      /* Bytes of data in aData */
-  char *aData;                    /* Pointer to block from malloc() */
-  i64 nLeafData;                  /* Number of bytes of leaf data written */
-};
+static int fts3TreeFinishNode(
+  SegmentNode *pTree, 
+  int iHeight, 
+  sqlite3_int64 iLeftChild
+){
+  int nStart;
+  assert( iHeight>=1 && iHeight<128 );
+  nStart = FTS3_VARINT_MAX - sqlite3Fts3VarintLen(iLeftChild);
+  pTree->aData[nStart] = (char)iHeight;
+  sqlite3Fts3PutVarint(&pTree->aData[nStart+1], iLeftChild);
+  return nStart;
+}
 
 /*
-** Type SegmentNode is used by the following three functions to create
-** the interior part of the segment b+-tree structures (everything except
-** the leaf nodes). These functions and type are only ever used by code
-** within the fts3SegWriterXXX() family of functions described above.
+** Write the buffer for the segment node pTree and all of its peers to the
+** database. Then call this function recursively to write the parent of 
+** pTree and its peers to the database. 
 **
-**   fts3NodeAddTerm()
-**   fts3NodeWrite()
-**   fts3NodeFree()
+** Except, if pTree is a root node, do not write it to the database. Instead,
+** set output variables *paRoot and *pnRoot to contain the root node.
 **
-** When a b+tree is written to the database (either as a result of a merge
-** or the pending-terms table being flushed), leaves are written into the 
-** database file as soon as they are completely populated. The interior of
-** the tree is assembled in memory and written out only once all leaves have
-** been populated and stored. This is Ok, as the b+-tree fanout is usually
-** very large, meaning that the interior of the tree consumes relatively 
-** little memory.
+** If successful, SQLITE_OK is returned and output variable *piLast is
+** set to the largest blockid written to the database (or zero if no
+** blocks were written to the db). Otherwise, an SQLite error code is 
+** returned.
 */
-struct SegmentNode {
-  SegmentNode *pParent;           /* Parent node (or NULL for root node) */
-  SegmentNode *pRight;            /* Pointer to right-sibling */
-  SegmentNode *pLeftmost;         /* Pointer to left-most node of this depth */
-  int nEntry;                     /* Number of terms written to node so far */
-  char *zTerm;                    /* Pointer to previous term buffer */
-  int nTerm;                      /* Number of bytes in zTerm */
-  int nMalloc;                    /* Size of malloc'd buffer at zMalloc */
-  char *zMalloc;                  /* Malloc'd space (possibly) used for zTerm */
-  int nData;                      /* Bytes of valid data so far */
-  char *aData;                    /* Node data */
-};
+static int fts3NodeWrite(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentNode *pTree,             /* SegmentNode handle */
+  int iHeight,                    /* Height of this node in tree */
+  sqlite3_int64 iLeaf,            /* Block id of first leaf node */
+  sqlite3_int64 iFree,            /* Block id of next free slot in %_segments */
+  sqlite3_int64 *piLast,          /* OUT: Block id of last entry written */
+  char **paRoot,                  /* OUT: Data for root node */
+  int *pnRoot                     /* OUT: Size of root node in bytes */
+){
+  int rc = SQLITE_OK;
 
-/*
-** Valid values for the second argument to fts3SqlStmt().
-*/
-#define SQL_DELETE_CONTENT             0
-#define SQL_IS_EMPTY                   1
-#define SQL_DELETE_ALL_CONTENT         2 
-#define SQL_DELETE_ALL_SEGMENTS        3
-#define SQL_DELETE_ALL_SEGDIR          4
-#define SQL_DELETE_ALL_DOCSIZE         5
-#define SQL_DELETE_ALL_STAT            6
-#define SQL_SELECT_CONTENT_BY_ROWID    7
-#define SQL_NEXT_SEGMENT_INDEX         8
-#define SQL_INSERT_SEGMENTS            9
-#define SQL_NEXT_SEGMENTS_ID          10
-#define SQL_INSERT_SEGDIR             11
-#define SQL_SELECT_LEVEL              12
-#define SQL_SELECT_LEVEL_RANGE        13
-#define SQL_SELECT_LEVEL_COUNT        14
-#define SQL_SELECT_SEGDIR_MAX_LEVEL   15
-#define SQL_DELETE_SEGDIR_LEVEL       16
-#define SQL_DELETE_SEGMENTS_RANGE     17
-#define SQL_CONTENT_INSERT            18
-#define SQL_DELETE_DOCSIZE            19
-#define SQL_REPLACE_DOCSIZE           20
-#define SQL_SELECT_DOCSIZE            21
-#define SQL_SELECT_STAT               22
-#define SQL_REPLACE_STAT              23
+  if( !pTree->pParent ){
+    /* Root node of the tree. */
+    int nStart = fts3TreeFinishNode(pTree, iHeight, iLeaf);
+    *piLast = iFree-1;
+    *pnRoot = pTree->nData - nStart;
+    *paRoot = &pTree->aData[nStart];
+  }else{
+    SegmentNode *pIter;
+    sqlite3_int64 iNextFree = iFree;
+    sqlite3_int64 iNextLeaf = iLeaf;
+    for(pIter=pTree->pLeftmost; pIter && rc==SQLITE_OK; pIter=pIter->pRight){
+      int nStart = fts3TreeFinishNode(pIter, iHeight, iNextLeaf);
+      int nWrite = pIter->nData - nStart;
+  
+      rc = fts3WriteSegment(p, iNextFree, &pIter->aData[nStart], nWrite);
+      iNextFree++;
+      iNextLeaf += (pIter->nEntry+1);
+    }
+    if( rc==SQLITE_OK ){
+      assert( iNextLeaf==iFree );
+      rc = fts3NodeWrite(
+          p, pTree->pParent, iHeight+1, iFree, iNextFree, piLast, paRoot, pnRoot
+      );
+    }
+  }
 
-#define SQL_SELECT_ALL_PREFIX_LEVEL   24
-#define SQL_DELETE_ALL_TERMS_SEGDIR   25
-#define SQL_DELETE_SEGDIR_RANGE       26
-#define SQL_SELECT_ALL_LANGID         27
-#define SQL_FIND_MERGE_LEVEL          28
-#define SQL_MAX_LEAF_NODE_ESTIMATE    29
-#define SQL_DELETE_SEGDIR_ENTRY       30
-#define SQL_SHIFT_SEGDIR_ENTRY        31
-#define SQL_SELECT_SEGDIR             32
-#define SQL_CHOMP_SEGDIR              33
-#define SQL_SEGMENT_IS_APPENDABLE     34
-#define SQL_SELECT_INDEXES            35
-#define SQL_SELECT_MXLEVEL            36
+  return rc;
+}
 
-#define SQL_SELECT_LEVEL_RANGE2       37
-#define SQL_UPDATE_LEVEL_IDX          38
-#define SQL_UPDATE_LEVEL              39
+/*
+** Free all memory allocations associated with the tree pTree.
+*/
+static void fts3NodeFree(SegmentNode *pTree){
+  if( pTree ){
+    SegmentNode *p = pTree->pLeftmost;
+    fts3NodeFree(p->pParent);
+    while( p ){
+      SegmentNode *pRight = p->pRight;
+      if( p->aData!=(char *)&p[1] ){
+        sqlite3_free(p->aData);
+      }
+      assert( pRight==0 || p->zMalloc==0 );
+      sqlite3_free(p->zMalloc);
+      sqlite3_free(p);
+      p = pRight;
+    }
+  }
+}
 
 /*
-** This function is used to obtain an SQLite prepared statement handle
-** for the statement identified by the second argument. If successful,
-** *pp is set to the requested statement handle and SQLITE_OK returned.
-** Otherwise, an SQLite error code is returned and *pp is set to 0.
+** Add a term to the segment being constructed by the SegmentWriter object
+** *ppWriter. When adding the first term to a segment, *ppWriter should
+** be passed NULL. This function will allocate a new SegmentWriter object
+** and return it via the input/output variable *ppWriter in this case.
 **
-** If argument apVal is not NULL, then it must point to an array with
-** at least as many entries as the requested statement has bound 
-** parameters. The values are bound to the statements parameters before
-** returning.
+** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
 */
-static int fts3SqlStmt(
+static int fts3SegWriterAdd(
   Fts3Table *p,                   /* Virtual table handle */
-  int eStmt,                      /* One of the SQL_XXX constants above */
-  sqlite3_stmt **pp,              /* OUT: Statement handle */
-  sqlite3_value **apVal           /* Values to bind to statement */
+  SegmentWriter **ppWriter,       /* IN/OUT: SegmentWriter handle */ 
+  int isCopyTerm,                 /* True if buffer zTerm must be copied */
+  const char *zTerm,              /* Pointer to buffer containing term */
+  int nTerm,                      /* Size of term in bytes */
+  const char *aDoclist,           /* Pointer to buffer containing doclist */
+  int nDoclist                    /* Size of doclist in bytes */
 ){
-  const char *azSql[] = {
-/* 0  */  "DELETE FROM %Q.'%q_content' WHERE rowid = ?",
-/* 1  */  "SELECT NOT EXISTS(SELECT docid FROM %Q.'%q_content' WHERE rowid!=?)",
-/* 2  */  "DELETE FROM %Q.'%q_content'",
-/* 3  */  "DELETE FROM %Q.'%q_segments'",
-/* 4  */  "DELETE FROM %Q.'%q_segdir'",
-/* 5  */  "DELETE FROM %Q.'%q_docsize'",
-/* 6  */  "DELETE FROM %Q.'%q_stat'",
-/* 7  */  "SELECT %s WHERE rowid=?",
-/* 8  */  "SELECT (SELECT max(idx) FROM %Q.'%q_segdir' WHERE level = ?) + 1",
-/* 9  */  "REPLACE INTO %Q.'%q_segments'(blockid, block) VALUES(?, ?)",
-/* 10 */  "SELECT coalesce((SELECT max(blockid) FROM %Q.'%q_segments') + 1, 1)",
-/* 11 */  "REPLACE INTO %Q.'%q_segdir' VALUES(?,?,?,?,?,?)",
-
-          /* Return segments in order from oldest to newest.*/ 
-/* 12 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
-            "FROM %Q.'%q_segdir' WHERE level = ? ORDER BY idx ASC",
-/* 13 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
-            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?"
-            "ORDER BY level DESC, idx ASC",
-
-/* 14 */  "SELECT count(*) FROM %Q.'%q_segdir' WHERE level = ?",
-/* 15 */  "SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?",
+  int nPrefix;                    /* Size of term prefix in bytes */
+  int nSuffix;                    /* Size of term suffix in bytes */
+  int nReq;                       /* Number of bytes required on leaf page */
+  int nData;
+  SegmentWriter *pWriter = *ppWriter;
 
-/* 16 */  "DELETE FROM %Q.'%q_segdir' WHERE level = ?",
-/* 17 */  "DELETE FROM %Q.'%q_segments' WHERE blockid BETWEEN ? AND ?",
-/* 18 */  "INSERT INTO %Q.'%q_content' VALUES(%s)",
-/* 19 */  "DELETE FROM %Q.'%q_docsize' WHERE docid = ?",
-/* 20 */  "REPLACE INTO %Q.'%q_docsize' VALUES(?,?)",
-/* 21 */  "SELECT size FROM %Q.'%q_docsize' WHERE docid=?",
-/* 22 */  "SELECT value FROM %Q.'%q_stat' WHERE id=?",
-/* 23 */  "REPLACE INTO %Q.'%q_stat' VALUES(?,?)",
-/* 24 */  "",
-/* 25 */  "",
+  if( !pWriter ){
+    int rc;
+    sqlite3_stmt *pStmt;
 
-/* 26 */ "DELETE FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?",
-/* 27 */ "SELECT ? UNION SELECT level / (1024 * ?) FROM %Q.'%q_segdir'",
+    /* Allocate the SegmentWriter structure */
+    pWriter = (SegmentWriter *)sqlite3_malloc(sizeof(SegmentWriter));
+    if( !pWriter ) return SQLITE_NOMEM;
+    memset(pWriter, 0, sizeof(SegmentWriter));
+    *ppWriter = pWriter;
 
-/* This statement is used to determine which level to read the input from
-** when performing an incremental merge. It returns the absolute level number
-** of the oldest level in the db that contains at least ? segments. Or,
-** if no level in the FTS index contains more than ? segments, the statement
-** returns zero rows.  */
-/* 28 */ "SELECT level FROM %Q.'%q_segdir' GROUP BY level HAVING count(*)>=?"
-         "  ORDER BY (level %% 1024) ASC LIMIT 1",
+    /* Allocate a buffer in which to accumulate data */
+    pWriter->aData = (char *)sqlite3_malloc(p->nNodeSize);
+    if( !pWriter->aData ) return SQLITE_NOMEM;
+    pWriter->nSize = p->nNodeSize;
 
-/* Estimate the upper limit on the number of leaf nodes in a new segment
-** created by merging the oldest :2 segments from absolute level :1. See 
-** function sqlite3Fts3Incrmerge() for details.  */
-/* 29 */ "SELECT 2 * total(1 + leaves_end_block - start_block) "
-         "  FROM %Q.'%q_segdir' WHERE level = ? AND idx < ?",
+    /* Find the next free blockid in the %_segments table */
+    rc = fts3SqlStmt(p, SQL_NEXT_SEGMENTS_ID, &pStmt, 0);
+    if( rc!=SQLITE_OK ) return rc;
+    if( SQLITE_ROW==sqlite3_step(pStmt) ){
+      pWriter->iFree = sqlite3_column_int64(pStmt, 0);
+      pWriter->iFirst = pWriter->iFree;
+    }
+    rc = sqlite3_reset(pStmt);
+    if( rc!=SQLITE_OK ) return rc;
+  }
+  nData = pWriter->nData;
 
-/* SQL_DELETE_SEGDIR_ENTRY
-**   Delete the %_segdir entry on absolute level :1 with index :2.  */
-/* 30 */ "DELETE FROM %Q.'%q_segdir' WHERE level = ? AND idx = ?",
+  nPrefix = fts3PrefixCompress(pWriter->zTerm, pWriter->nTerm, zTerm, nTerm);
+  nSuffix = nTerm-nPrefix;
 
-/* SQL_SHIFT_SEGDIR_ENTRY
-**   Modify the idx value for the segment with idx=:3 on absolute level :2
-**   to :1.  */
-/* 31 */ "UPDATE %Q.'%q_segdir' SET idx = ? WHERE level=? AND idx=?",
+  /* Figure out how many bytes are required by this new entry */
+  nReq = sqlite3Fts3VarintLen(nPrefix) +    /* varint containing prefix size */
+    sqlite3Fts3VarintLen(nSuffix) +         /* varint containing suffix size */
+    nSuffix +                               /* Term suffix */
+    sqlite3Fts3VarintLen(nDoclist) +        /* Size of doclist */
+    nDoclist;                               /* Doclist data */
 
-/* SQL_SELECT_SEGDIR
-**   Read a single entry from the %_segdir table. The entry from absolute 
-**   level :1 with index value :2.  */
-/* 32 */  "SELECT idx, start_block, leaves_end_block, end_block, root "
-            "FROM %Q.'%q_segdir' WHERE level = ? AND idx = ?",
+  if( nData>0 && nData+nReq>p->nNodeSize ){
+    int rc;
 
-/* SQL_CHOMP_SEGDIR
-**   Update the start_block (:1) and root (:2) fields of the %_segdir
-**   entry located on absolute level :3 with index :4.  */
-/* 33 */  "UPDATE %Q.'%q_segdir' SET start_block = ?, root = ?"
-            "WHERE level = ? AND idx = ?",
+    /* The current leaf node is full. Write it out to the database. */
+    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, nData);
+    if( rc!=SQLITE_OK ) return rc;
+    p->nLeafAdd++;
 
-/* SQL_SEGMENT_IS_APPENDABLE
-**   Return a single row if the segment with end_block=? is appendable. Or
-**   no rows otherwise.  */
-/* 34 */  "SELECT 1 FROM %Q.'%q_segments' WHERE blockid=? AND block IS NULL",
+    /* Add the current term to the interior node tree. The term added to
+    ** the interior tree must:
+    **
+    **   a) be greater than the largest term on the leaf node just written
+    **      to the database (still available in pWriter->zTerm), and
+    **
+    **   b) be less than or equal to the term about to be added to the new
+    **      leaf node (zTerm/nTerm).
+    **
+    ** In other words, it must be the prefix of zTerm 1 byte longer than
+    ** the common prefix (if any) of zTerm and pWriter->zTerm.
+    */
+    assert( nPrefix<nTerm );
+    rc = fts3NodeAddTerm(p, &pWriter->pTree, isCopyTerm, zTerm, nPrefix+1);
+    if( rc!=SQLITE_OK ) return rc;
 
-/* SQL_SELECT_INDEXES
-**   Return the list of valid segment indexes for absolute level ?  */
-/* 35 */  "SELECT idx FROM %Q.'%q_segdir' WHERE level=? ORDER BY 1 ASC",
+    nData = 0;
+    pWriter->nTerm = 0;
 
-/* SQL_SELECT_MXLEVEL
-**   Return the largest relative level in the FTS index or indexes.  */
-/* 36 */  "SELECT max( level %% 1024 ) FROM %Q.'%q_segdir'",
+    nPrefix = 0;
+    nSuffix = nTerm;
+    nReq = 1 +                              /* varint containing prefix size */
+      sqlite3Fts3VarintLen(nTerm) +         /* varint containing suffix size */
+      nTerm +                               /* Term suffix */
+      sqlite3Fts3VarintLen(nDoclist) +      /* Size of doclist */
+      nDoclist;                             /* Doclist data */
+  }
 
-          /* Return segments in order from oldest to newest.*/ 
-/* 37 */  "SELECT level, idx, end_block "
-            "FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ? "
-            "ORDER BY level DESC, idx ASC",
+  /* Increase the total number of bytes written to account for the new entry. */
+  pWriter->nLeafData += nReq;
 
-          /* Update statements used while promoting segments */
-/* 38 */  "UPDATE OR FAIL %Q.'%q_segdir' SET level=-1,idx=? "
-            "WHERE level=? AND idx=?",
-/* 39 */  "UPDATE OR FAIL %Q.'%q_segdir' SET level=? WHERE level=-1"
+  /* If the buffer currently allocated is too small for this entry, realloc
+  ** the buffer to make it large enough.
+  */
+  if( nReq>pWriter->nSize ){
+    char *aNew = sqlite3_realloc(pWriter->aData, nReq);
+    if( !aNew ) return SQLITE_NOMEM;
+    pWriter->aData = aNew;
+    pWriter->nSize = nReq;
+  }
+  assert( nData+nReq<=pWriter->nSize );
 
-  };
-  int rc = SQLITE_OK;
-  sqlite3_stmt *pStmt;
+  /* Append the prefix-compressed term and doclist to the buffer. */
+  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nPrefix);
+  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nSuffix);
+  memcpy(&pWriter->aData[nData], &zTerm[nPrefix], nSuffix);
+  nData += nSuffix;
+  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nDoclist);
+  memcpy(&pWriter->aData[nData], aDoclist, nDoclist);
+  pWriter->nData = nData + nDoclist;
 
-  assert( SizeofArray(azSql)==SizeofArray(p->aStmt) );
-  assert( eStmt<SizeofArray(azSql) && eStmt>=0 );
-  
-  pStmt = p->aStmt[eStmt];
-  if( !pStmt ){
-    char *zSql;
-    if( eStmt==SQL_CONTENT_INSERT ){
-      zSql = sqlite3_mprintf(azSql[eStmt], p->zDb, p->zName, p->zWriteExprlist);
-    }else if( eStmt==SQL_SELECT_CONTENT_BY_ROWID ){
-      zSql = sqlite3_mprintf(azSql[eStmt], p->zReadExprlist);
-    }else{
-      zSql = sqlite3_mprintf(azSql[eStmt], p->zDb, p->zName);
-    }
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-    }else{
-      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, NULL);
-      sqlite3_free(zSql);
-      assert( rc==SQLITE_OK || pStmt==0 );
-      p->aStmt[eStmt] = pStmt;
-    }
-  }
-  if( apVal ){
-    int i;
-    int nParam = sqlite3_bind_parameter_count(pStmt);
-    for(i=0; rc==SQLITE_OK && i<nParam; i++){
-      rc = sqlite3_bind_value(pStmt, i+1, apVal[i]);
+  /* Save the current term so that it can be used to prefix-compress the next.
+  ** If the isCopyTerm parameter is true, then the buffer pointed to by
+  ** zTerm is transient, so take a copy of the term data. Otherwise, just
+  ** store a copy of the pointer.
+  */
+  if( isCopyTerm ){
+    if( nTerm>pWriter->nMalloc ){
+      char *zNew = sqlite3_realloc(pWriter->zMalloc, nTerm*2);
+      if( !zNew ){
+        return SQLITE_NOMEM;
+      }
+      pWriter->nMalloc = nTerm*2;
+      pWriter->zMalloc = zNew;
+      pWriter->zTerm = zNew;
     }
+    assert( pWriter->zTerm==pWriter->zMalloc );
+    memcpy(pWriter->zTerm, zTerm, nTerm);
+  }else{
+    pWriter->zTerm = (char *)zTerm;
   }
-  *pp = pStmt;
-  return rc;
-}
+  pWriter->nTerm = nTerm;
 
+  return SQLITE_OK;
+}
 
-static int fts3SelectDocsize(
-  Fts3Table *pTab,                /* FTS3 table handle */
-  sqlite3_int64 iDocid,           /* Docid to bind for SQL_SELECT_DOCSIZE */
-  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
+/*
+** Flush all data associated with the SegmentWriter object pWriter to the
+** database. This function must be called after all terms have been added
+** to the segment using fts3SegWriterAdd(). If successful, SQLITE_OK is
+** returned. Otherwise, an SQLite error code.
+*/
+static int fts3SegWriterFlush(
+  Fts3Table *p,                   /* Virtual table handle */
+  SegmentWriter *pWriter,         /* SegmentWriter to flush to the db */
+  sqlite3_int64 iLevel,           /* Value for 'level' column of %_segdir */
+  int iIdx                        /* Value for 'idx' column of %_segdir */
 ){
-  sqlite3_stmt *pStmt = 0;        /* Statement requested from fts3SqlStmt() */
   int rc;                         /* Return code */
+  if( pWriter->pTree ){
+    sqlite3_int64 iLast = 0;      /* Largest block id written to database */
+    sqlite3_int64 iLastLeaf;      /* Largest leaf block id written to db */
+    char *zRoot = NULL;           /* Pointer to buffer containing root node */
+    int nRoot = 0;                /* Size of buffer zRoot */
 
-  rc = fts3SqlStmt(pTab, SQL_SELECT_DOCSIZE, &pStmt, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pStmt, 1, iDocid);
-    rc = sqlite3_step(pStmt);
-    if( rc!=SQLITE_ROW || sqlite3_column_type(pStmt, 0)!=SQLITE_BLOB ){
-      rc = sqlite3_reset(pStmt);
-      if( rc==SQLITE_OK ) rc = FTS_CORRUPT_VTAB;
-      pStmt = 0;
-    }else{
-      rc = SQLITE_OK;
+    iLastLeaf = pWriter->iFree;
+    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, pWriter->nData);
+    if( rc==SQLITE_OK ){
+      rc = fts3NodeWrite(p, pWriter->pTree, 1,
+          pWriter->iFirst, pWriter->iFree, &iLast, &zRoot, &nRoot);
+    }
+    if( rc==SQLITE_OK ){
+      rc = fts3WriteSegdir(p, iLevel, iIdx, 
+          pWriter->iFirst, iLastLeaf, iLast, pWriter->nLeafData, zRoot, nRoot);
     }
+  }else{
+    /* The entire tree fits on the root node. Write it to the segdir table. */
+    rc = fts3WriteSegdir(p, iLevel, iIdx, 
+        0, 0, 0, pWriter->nLeafData, pWriter->aData, pWriter->nData);
   }
-
-  *ppStmt = pStmt;
+  p->nLeafAdd++;
   return rc;
 }
 
-SQLITE_PRIVATE int sqlite3Fts3SelectDoctotal(
-  Fts3Table *pTab,                /* Fts3 table handle */
-  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
-){
-  sqlite3_stmt *pStmt = 0;
+/*
+** Release all memory held by the SegmentWriter object passed as the 
+** first argument.
+*/
+static void fts3SegWriterFree(SegmentWriter *pWriter){
+  if( pWriter ){
+    sqlite3_free(pWriter->aData);
+    sqlite3_free(pWriter->zMalloc);
+    fts3NodeFree(pWriter->pTree);
+    sqlite3_free(pWriter);
+  }
+}
+
+/*
+** The first value in the apVal[] array is assumed to contain an integer.
+** This function tests if there exist any documents with docid values that
+** are different from that integer. i.e. if deleting the document with docid
+** pRowid would mean the FTS3 table were empty.
+**
+** If successful, *pisEmpty is set to true if the table is empty except for
+** document pRowid, or false otherwise, and SQLITE_OK is returned. If an
+** error occurs, an SQLite error code is returned.
+*/
+static int fts3IsEmpty(Fts3Table *p, sqlite3_value *pRowid, int *pisEmpty){
+  sqlite3_stmt *pStmt;
   int rc;
-  rc = fts3SqlStmt(pTab, SQL_SELECT_STAT, &pStmt, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
-    if( sqlite3_step(pStmt)!=SQLITE_ROW
-     || sqlite3_column_type(pStmt, 0)!=SQLITE_BLOB
-    ){
+  if( p->zContentTbl ){
+    /* If using the content=xxx option, assume the table is never empty */
+    *pisEmpty = 0;
+    rc = SQLITE_OK;
+  }else{
+    rc = fts3SqlStmt(p, SQL_IS_EMPTY, &pStmt, &pRowid);
+    if( rc==SQLITE_OK ){
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        *pisEmpty = sqlite3_column_int(pStmt, 0);
+      }
       rc = sqlite3_reset(pStmt);
-      if( rc==SQLITE_OK ) rc = FTS_CORRUPT_VTAB;
-      pStmt = 0;
     }
   }
-  *ppStmt = pStmt;
   return rc;
 }
 
-SQLITE_PRIVATE int sqlite3Fts3SelectDocsize(
-  Fts3Table *pTab,                /* Fts3 table handle */
-  sqlite3_int64 iDocid,           /* Docid to read size data for */
-  sqlite3_stmt **ppStmt           /* OUT: Statement handle */
-){
-  return fts3SelectDocsize(pTab, iDocid, ppStmt);
-}
-
 /*
-** Similar to fts3SqlStmt(). Except, after binding the parameters in
-** array apVal[] to the SQL statement identified by eStmt, the statement
-** is executed.
+** Set *pnMax to the largest segment level in the database for the index
+** iIndex.
 **
-** Returns SQLITE_OK if the statement is successfully executed, or an
-** SQLite error code otherwise.
+** Segment levels are stored in the 'level' column of the %_segdir table.
+**
+** Return SQLITE_OK if successful, or an SQLite error code if not.
 */
-static void fts3SqlExec(
-  int *pRC,                /* Result code */
-  Fts3Table *p,            /* The FTS3 table */
-  int eStmt,               /* Index of statement to evaluate */
-  sqlite3_value **apVal    /* Parameters to bind */
+static int fts3SegmentMaxLevel(
+  Fts3Table *p, 
+  int iLangid,
+  int iIndex, 
+  sqlite3_int64 *pnMax
 ){
   sqlite3_stmt *pStmt;
   int rc;
-  if( *pRC ) return;
-  rc = fts3SqlStmt(p, eStmt, &pStmt, apVal); 
-  if( rc==SQLITE_OK ){
-    sqlite3_step(pStmt);
-    rc = sqlite3_reset(pStmt);
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  /* Set pStmt to the compiled version of:
+  **
+  **   SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?
+  **
+  ** (1024 is actually the value of macro FTS3_SEGDIR_PREFIXLEVEL_STR).
+  */
+  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR_MAX_LEVEL, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+  sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
+  sqlite3_bind_int64(pStmt, 2, 
+      getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
+  );
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    *pnMax = sqlite3_column_int64(pStmt, 0);
   }
-  *pRC = rc;
+  return sqlite3_reset(pStmt);
 }
 
+/*
+** iAbsLevel is an absolute level that may be assumed to exist within
+** the database. This function checks if it is the largest level number
+** within its index. Assuming no error occurs, *pbMax is set to 1 if
+** iAbsLevel is indeed the largest level, or 0 otherwise, and SQLITE_OK
+** is returned. If an error occurs, an error code is returned and the
+** final value of *pbMax is undefined.
+*/
+static int fts3SegmentIsMaxLevel(Fts3Table *p, i64 iAbsLevel, int *pbMax){
+
+  /* Set pStmt to the compiled version of:
+  **
+  **   SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?
+  **
+  ** (1024 is actually the value of macro FTS3_SEGDIR_PREFIXLEVEL_STR).
+  */
+  sqlite3_stmt *pStmt;
+  int rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR_MAX_LEVEL, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+  sqlite3_bind_int64(pStmt, 1, iAbsLevel+1);
+  sqlite3_bind_int64(pStmt, 2, 
+      ((iAbsLevel/FTS3_SEGDIR_MAXLEVEL)+1) * FTS3_SEGDIR_MAXLEVEL
+  );
+
+  *pbMax = 0;
+  if( SQLITE_ROW==sqlite3_step(pStmt) ){
+    *pbMax = sqlite3_column_type(pStmt, 0)==SQLITE_NULL;
+  }
+  return sqlite3_reset(pStmt);
+}
 
 /*
-** This function ensures that the caller has obtained an exclusive 
-** shared-cache table-lock on the %_segdir table. This is required before 
-** writing data to the fts3 table. If this lock is not acquired first, then
-** the caller may end up attempting to take this lock as part of committing
-** a transaction, causing SQLite to return SQLITE_LOCKED or 
-** LOCKED_SHAREDCACHEto a COMMIT command.
-**
-** It is best to avoid this because if FTS3 returns any error when 
-** committing a transaction, the whole transaction will be rolled back. 
-** And this is not what users expect when they get SQLITE_LOCKED_SHAREDCACHE. 
-** It can still happen if the user locks the underlying tables directly 
-** instead of accessing them via FTS.
+** Delete all entries in the %_segments table associated with the segment
+** opened with seg-reader pSeg. This function does not affect the contents
+** of the %_segdir table.
 */
-static int fts3Writelock(Fts3Table *p){
-  int rc = SQLITE_OK;
-  
-  if( p->nPendingData==0 ){
-    sqlite3_stmt *pStmt;
-    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_LEVEL, &pStmt, 0);
+static int fts3DeleteSegment(
+  Fts3Table *p,                   /* FTS table handle */
+  Fts3SegReader *pSeg             /* Segment to delete */
+){
+  int rc = SQLITE_OK;             /* Return code */
+  if( pSeg->iStartBlock ){
+    sqlite3_stmt *pDelete;        /* SQL statement to delete rows */
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGMENTS_RANGE, &pDelete, 0);
     if( rc==SQLITE_OK ){
-      sqlite3_bind_null(pStmt, 1);
-      sqlite3_step(pStmt);
-      rc = sqlite3_reset(pStmt);
+      sqlite3_bind_int64(pDelete, 1, pSeg->iStartBlock);
+      sqlite3_bind_int64(pDelete, 2, pSeg->iEndBlock);
+      sqlite3_step(pDelete);
+      rc = sqlite3_reset(pDelete);
     }
   }
-
   return rc;
 }
 
 /*
-** FTS maintains a separate indexes for each language-id (a 32-bit integer).
-** Within each language id, a separate index is maintained to store the
-** document terms, and each configured prefix size (configured the FTS 
-** "prefix=" option). And each index consists of multiple levels ("relative
-** levels").
-**
-** All three of these values (the language id, the specific index and the
-** level within the index) are encoded in 64-bit integer values stored
-** in the %_segdir table on disk. This function is used to convert three
-** separate component values into the single 64-bit integer value that
-** can be used to query the %_segdir table.
+** This function is used after merging multiple segments into a single large
+** segment to delete the old, now redundant, segment b-trees. Specifically,
+** it:
+** 
+**   1) Deletes all %_segments entries for the segments associated with 
+**      each of the SegReader objects in the array passed as the third 
+**      argument, and
 **
-** Specifically, each language-id/index combination is allocated 1024 
-** 64-bit integer level values ("absolute levels"). The main terms index
-** for language-id 0 is allocate values 0-1023. The first prefix index
-** (if any) for language-id 0 is allocated values 1024-2047. And so on.
-** Language 1 indexes are allocated immediately following language 0.
+**   2) deletes all %_segdir entries with level iLevel, or all %_segdir
+**      entries regardless of level if (iLevel<0).
 **
-** So, for a system with nPrefix prefix indexes configured, the block of
-** absolute levels that corresponds to language-id iLangid and index 
-** iIndex starts at absolute level ((iLangid * (nPrefix+1) + iIndex) * 1024).
+** SQLITE_OK is returned if successful, otherwise an SQLite error code.
 */
-static sqlite3_int64 getAbsoluteLevel(
-  Fts3Table *p,                   /* FTS3 table handle */
+static int fts3DeleteSegdir(
+  Fts3Table *p,                   /* Virtual table handle */
   int iLangid,                    /* Language id */
-  int iIndex,                     /* Index in p->aIndex[] */
-  int iLevel                      /* Level of segments */
+  int iIndex,                     /* Index for p->aIndex */
+  int iLevel,                     /* Level of %_segdir entries to delete */
+  Fts3SegReader **apSegment,      /* Array of SegReader objects */
+  int nReader                     /* Size of array apSegment */
 ){
-  sqlite3_int64 iBase;            /* First absolute level for iLangid/iIndex */
-  assert( iLangid>=0 );
-  assert( p->nIndex>0 );
-  assert( iIndex>=0 && iIndex<p->nIndex );
+  int rc = SQLITE_OK;             /* Return Code */
+  int i;                          /* Iterator variable */
+  sqlite3_stmt *pDelete = 0;      /* SQL statement to delete rows */
 
-  iBase = ((sqlite3_int64)iLangid * p->nIndex + iIndex) * FTS3_SEGDIR_MAXLEVEL;
-  return iBase + iLevel;
+  for(i=0; rc==SQLITE_OK && i<nReader; i++){
+    rc = fts3DeleteSegment(p, apSegment[i]);
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
+
+  assert( iLevel>=0 || iLevel==FTS3_SEGCURSOR_ALL );
+  if( iLevel==FTS3_SEGCURSOR_ALL ){
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_RANGE, &pDelete, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pDelete, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
+      sqlite3_bind_int64(pDelete, 2, 
+          getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
+      );
+    }
+  }else{
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_LEVEL, &pDelete, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(
+          pDelete, 1, getAbsoluteLevel(p, iLangid, iIndex, iLevel)
+      );
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    sqlite3_step(pDelete);
+    rc = sqlite3_reset(pDelete);
+  }
+
+  return rc;
 }
 
 /*
-** Set *ppStmt to a statement handle that may be used to iterate through
-** all rows in the %_segdir table, from oldest to newest. If successful,
-** return SQLITE_OK. If an error occurs while preparing the statement, 
-** return an SQLite error code.
-**
-** There is only ever one instance of this SQL statement compiled for
-** each FTS3 table.
+** When this function is called, buffer *ppList (size *pnList bytes) contains 
+** a position list that may (or may not) feature multiple columns. This
+** function adjusts the pointer *ppList and the length *pnList so that they
+** identify the subset of the position list that corresponds to column iCol.
 **
-** The statement returns the following columns from the %_segdir table:
+** If there are no entries in the input position list for column iCol, then
+** *pnList is set to zero before returning.
 **
-**   0: idx
-**   1: start_block
-**   2: leaves_end_block
-**   3: end_block
-**   4: root
+** If parameter bZero is non-zero, then any part of the input list following
+** the end of the output list is zeroed before returning.
 */
-SQLITE_PRIVATE int sqlite3Fts3AllSegdirs(
-  Fts3Table *p,                   /* FTS3 table */
-  int iLangid,                    /* Language being queried */
-  int iIndex,                     /* Index for p->aIndex[] */
-  int iLevel,                     /* Level to select (relative level) */
-  sqlite3_stmt **ppStmt           /* OUT: Compiled statement */
+static void fts3ColumnFilter(
+  int iCol,                       /* Column to filter on */
+  int bZero,                      /* Zero out anything following *ppList */
+  char **ppList,                  /* IN/OUT: Pointer to position list */
+  int *pnList                     /* IN/OUT: Size of buffer *ppList in bytes */
 ){
-  int rc;
-  sqlite3_stmt *pStmt = 0;
-
-  assert( iLevel==FTS3_SEGCURSOR_ALL || iLevel>=0 );
-  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
-  assert( iIndex>=0 && iIndex<p->nIndex );
+  char *pList = *ppList;
+  int nList = *pnList;
+  char *pEnd = &pList[nList];
+  int iCurrent = 0;
+  char *p = pList;
 
-  if( iLevel<0 ){
-    /* "SELECT * FROM %_segdir WHERE level BETWEEN ? AND ? ORDER BY ..." */
-    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE, &pStmt, 0);
-    if( rc==SQLITE_OK ){ 
-      sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
-      sqlite3_bind_int64(pStmt, 2, 
-          getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
-      );
+  assert( iCol>=0 );
+  while( 1 ){
+    char c = 0;
+    while( p<pEnd && (c | *p)&0xFE ) c = *p++ & 0x80;
+  
+    if( iCol==iCurrent ){
+      nList = (int)(p - pList);
+      break;
     }
-  }else{
-    /* "SELECT * FROM %_segdir WHERE level = ? ORDER BY ..." */
-    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL, &pStmt, 0);
-    if( rc==SQLITE_OK ){ 
-      sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex,iLevel));
+
+    nList -= (int)(p - pList);
+    pList = p;
+    if( nList==0 ){
+      break;
     }
+    p = &pList[1];
+    p += fts3GetVarint32(p, &iCurrent);
   }
-  *ppStmt = pStmt;
-  return rc;
+
+  if( bZero && &pList[nList]!=pEnd ){
+    memset(&pList[nList], 0, pEnd - &pList[nList]);
+  }
+  *ppList = pList;
+  *pnList = nList;
+}
+
+/*
+** Cache data in the Fts3MultiSegReader.aBuffer[] buffer (overwriting any
+** existing data). Grow the buffer if required.
+**
+** If successful, return SQLITE_OK. Otherwise, if an OOM error is encountered
+** trying to resize the buffer, return SQLITE_NOMEM.
+*/
+static int fts3MsrBufferData(
+  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
+  char *pList,
+  int nList
+){
+  if( nList>pMsr->nBuffer ){
+    char *pNew;
+    pMsr->nBuffer = nList*2;
+    pNew = (char *)sqlite3_realloc(pMsr->aBuffer, pMsr->nBuffer);
+    if( !pNew ) return SQLITE_NOMEM;
+    pMsr->aBuffer = pNew;
+  }
+
+  memcpy(pMsr->aBuffer, pList, nList);
+  return SQLITE_OK;
 }
 
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrNext(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
+  sqlite3_int64 *piDocid,         /* OUT: Docid value */
+  char **paPoslist,               /* OUT: Pointer to position list */
+  int *pnPoslist                  /* OUT: Size of position list in bytes */
+){
+  int nMerge = pMsr->nAdvance;
+  Fts3SegReader **apSegment = pMsr->apSegment;
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
+    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
+  );
+
+  if( nMerge==0 ){
+    *paPoslist = 0;
+    return SQLITE_OK;
+  }
+
+  while( 1 ){
+    Fts3SegReader *pSeg;
+    pSeg = pMsr->apSegment[0];
+
+    if( pSeg->pOffsetList==0 ){
+      *paPoslist = 0;
+      break;
+    }else{
+      int rc;
+      char *pList;
+      int nList;
+      int j;
+      sqlite3_int64 iDocid = apSegment[0]->iDocid;
+
+      rc = fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
+      j = 1;
+      while( rc==SQLITE_OK 
+        && j<nMerge
+        && apSegment[j]->pOffsetList
+        && apSegment[j]->iDocid==iDocid
+      ){
+        rc = fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
+        j++;
+      }
+      if( rc!=SQLITE_OK ) return rc;
+      fts3SegReaderSort(pMsr->apSegment, nMerge, j, xCmp);
+
+      if( nList>0 && fts3SegReaderIsPending(apSegment[0]) ){
+        rc = fts3MsrBufferData(pMsr, pList, nList+1);
+        if( rc!=SQLITE_OK ) return rc;
+        assert( (pMsr->aBuffer[nList] & 0xFE)==0x00 );
+        pList = pMsr->aBuffer;
+      }
 
-/*
-** Append a single varint to a PendingList buffer. SQLITE_OK is returned
-** if successful, or an SQLite error code otherwise.
-**
-** This function also serves to allocate the PendingList structure itself.
-** For example, to create a new PendingList structure containing two
-** varints:
-**
-**   PendingList *p = 0;
-**   fts3PendingListAppendVarint(&p, 1);
-**   fts3PendingListAppendVarint(&p, 2);
-*/
-static int fts3PendingListAppendVarint(
-  PendingList **pp,               /* IN/OUT: Pointer to PendingList struct */
-  sqlite3_int64 i                 /* Value to append to data */
-){
-  PendingList *p = *pp;
+      if( pMsr->iColFilter>=0 ){
+        fts3ColumnFilter(pMsr->iColFilter, 1, &pList, &nList);
+      }
 
-  /* Allocate or grow the PendingList as required. */
-  if( !p ){
-    p = sqlite3_malloc(sizeof(*p) + 100);
-    if( !p ){
-      return SQLITE_NOMEM;
-    }
-    p->nSpace = 100;
-    p->aData = (char *)&p[1];
-    p->nData = 0;
-  }
-  else if( p->nData+FTS3_VARINT_MAX+1>p->nSpace ){
-    int nNew = p->nSpace * 2;
-    p = sqlite3_realloc(p, sizeof(*p) + nNew);
-    if( !p ){
-      sqlite3_free(*pp);
-      *pp = 0;
-      return SQLITE_NOMEM;
+      if( nList>0 ){
+        *paPoslist = pList;
+        *piDocid = iDocid;
+        *pnPoslist = nList;
+        break;
+      }
     }
-    p->nSpace = nNew;
-    p->aData = (char *)&p[1];
   }
 
-  /* Append the new serialized varint to the end of the list. */
-  p->nData += sqlite3Fts3PutVarint(&p->aData[p->nData], i);
-  p->aData[p->nData] = '\0';
-  *pp = p;
   return SQLITE_OK;
 }
 
-/*
-** Add a docid/column/position entry to a PendingList structure. Non-zero
-** is returned if the structure is sqlite3_realloced as part of adding
-** the entry. Otherwise, zero.
-**
-** If an OOM error occurs, *pRc is set to SQLITE_NOMEM before returning.
-** Zero is always returned in this case. Otherwise, if no OOM error occurs,
-** it is set to SQLITE_OK.
-*/
-static int fts3PendingListAppend(
-  PendingList **pp,               /* IN/OUT: PendingList structure */
-  sqlite3_int64 iDocid,           /* Docid for entry to add */
-  sqlite3_int64 iCol,             /* Column for entry to add */
-  sqlite3_int64 iPos,             /* Position of term for entry to add */
-  int *pRc                        /* OUT: Return code */
+static int fts3SegReaderStart(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr,       /* Cursor object */
+  const char *zTerm,              /* Term searched for (or NULL) */
+  int nTerm                       /* Length of zTerm in bytes */
 ){
-  PendingList *p = *pp;
-  int rc = SQLITE_OK;
+  int i;
+  int nSeg = pCsr->nSegment;
 
-  assert( !p || p->iLastDocid<=iDocid );
+  /* If the Fts3SegFilter defines a specific term (or term prefix) to search 
+  ** for, then advance each segment iterator until it points to a term of
+  ** equal or greater value than the specified term. This prevents many
+  ** unnecessary merge/sort operations for the case where single segment
+  ** b-tree leaf nodes contain more than one term.
+  */
+  for(i=0; pCsr->bRestart==0 && i<pCsr->nSegment; i++){
+    int res = 0;
+    Fts3SegReader *pSeg = pCsr->apSegment[i];
+    do {
+      int rc = fts3SegReaderNext(p, pSeg, 0);
+      if( rc!=SQLITE_OK ) return rc;
+    }while( zTerm && (res = fts3SegReaderTermCmp(pSeg, zTerm, nTerm))<0 );
 
-  if( !p || p->iLastDocid!=iDocid ){
-    sqlite3_int64 iDelta = iDocid - (p ? p->iLastDocid : 0);
-    if( p ){
-      assert( p->nData<p->nSpace );
-      assert( p->aData[p->nData]==0 );
-      p->nData++;
-    }
-    if( SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, iDelta)) ){
-      goto pendinglistappend_out;
-    }
-    p->iLastCol = -1;
-    p->iLastPos = 0;
-    p->iLastDocid = iDocid;
-  }
-  if( iCol>0 && p->iLastCol!=iCol ){
-    if( SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, 1))
-     || SQLITE_OK!=(rc = fts3PendingListAppendVarint(&p, iCol))
-    ){
-      goto pendinglistappend_out;
-    }
-    p->iLastCol = iCol;
-    p->iLastPos = 0;
-  }
-  if( iCol>=0 ){
-    assert( iPos>p->iLastPos || (iPos==0 && p->iLastPos==0) );
-    rc = fts3PendingListAppendVarint(&p, 2+iPos-p->iLastPos);
-    if( rc==SQLITE_OK ){
-      p->iLastPos = iPos;
+    if( pSeg->bLookup && res!=0 ){
+      fts3SegReaderSetEof(pSeg);
     }
   }
+  fts3SegReaderSort(pCsr->apSegment, nSeg, nSeg, fts3SegReaderCmp);
 
- pendinglistappend_out:
-  *pRc = rc;
-  if( p!=*pp ){
-    *pp = p;
-    return 1;
-  }
-  return 0;
+  return SQLITE_OK;
 }
 
-/*
-** Free a PendingList object allocated by fts3PendingListAppend().
-*/
-static void fts3PendingListDelete(PendingList *pList){
-  sqlite3_free(pList);
+SQLITE_PRIVATE int sqlite3Fts3SegReaderStart(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr,       /* Cursor object */
+  Fts3SegFilter *pFilter          /* Restrictions on range of iteration */
+){
+  pCsr->pFilter = pFilter;
+  return fts3SegReaderStart(p, pCsr, pFilter->zTerm, pFilter->nTerm);
 }
 
-/*
-** Add an entry to one of the pending-terms hash tables.
-*/
-static int fts3PendingTermsAddOne(
-  Fts3Table *p,
-  int iCol,
-  int iPos,
-  Fts3Hash *pHash,                /* Pending terms hash table to add entry to */
-  const char *zToken,
-  int nToken
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrStart(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr,       /* Cursor object */
+  int iCol,                       /* Column to match on. */
+  const char *zTerm,              /* Term to iterate through a doclist for */
+  int nTerm                       /* Number of bytes in zTerm */
 ){
-  PendingList *pList;
-  int rc = SQLITE_OK;
+  int i;
+  int rc;
+  int nSegment = pCsr->nSegment;
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
+    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
+  );
 
-  pList = (PendingList *)fts3HashFind(pHash, zToken, nToken);
-  if( pList ){
-    p->nPendingData -= (pList->nData + nToken + sizeof(Fts3HashElem));
-  }
-  if( fts3PendingListAppend(&pList, p->iPrevDocid, iCol, iPos, &rc) ){
-    if( pList==fts3HashInsert(pHash, zToken, nToken, pList) ){
-      /* Malloc failed while inserting the new entry. This can only 
-      ** happen if there was no previous entry for this token.
-      */
-      assert( 0==fts3HashFind(pHash, zToken, nToken) );
-      sqlite3_free(pList);
-      rc = SQLITE_NOMEM;
+  assert( pCsr->pFilter==0 );
+  assert( zTerm && nTerm>0 );
+
+  /* Advance each segment iterator until it points to the term zTerm/nTerm. */
+  rc = fts3SegReaderStart(p, pCsr, zTerm, nTerm);
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Determine how many of the segments actually point to zTerm/nTerm. */
+  for(i=0; i<nSegment; i++){
+    Fts3SegReader *pSeg = pCsr->apSegment[i];
+    if( !pSeg->aNode || fts3SegReaderTermCmp(pSeg, zTerm, nTerm) ){
+      break;
     }
   }
-  if( rc==SQLITE_OK ){
-    p->nPendingData += (pList->nData + nToken + sizeof(Fts3HashElem));
+  pCsr->nAdvance = i;
+
+  /* Advance each of the segments to point to the first docid. */
+  for(i=0; i<pCsr->nAdvance; i++){
+    rc = fts3SegReaderFirstDocid(p, pCsr->apSegment[i]);
+    if( rc!=SQLITE_OK ) return rc;
   }
-  return rc;
+  fts3SegReaderSort(pCsr->apSegment, i, i, xCmp);
+
+  assert( iCol<0 || iCol<p->nColumn );
+  pCsr->iColFilter = iCol;
+
+  return SQLITE_OK;
 }
 
 /*
-** Tokenize the nul-terminated string zText and add all tokens to the
-** pending-terms hash-table. The docid used is that currently stored in
-** p->iPrevDocid, and the column is specified by argument iCol.
+** This function is called on a MultiSegReader that has been started using
+** sqlite3Fts3MsrIncrStart(). One or more calls to MsrIncrNext() may also
+** have been made. Calling this function puts the MultiSegReader in such
+** a state that if the next two calls are:
 **
-** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
+**   sqlite3Fts3SegReaderStart()
+**   sqlite3Fts3SegReaderStep()
+**
+** then the entire doclist for the term is available in 
+** MultiSegReader.aDoclist/nDoclist.
 */
-static int fts3PendingTermsAdd(
-  Fts3Table *p,                   /* Table into which text will be inserted */
-  int iLangid,                    /* Language id to use */
-  const char *zText,              /* Text of document to be inserted */
-  int iCol,                       /* Column into which text is being inserted */
-  u32 *pnWord                     /* IN/OUT: Incr. by number tokens inserted */
-){
-  int rc;
-  int iStart = 0;
-  int iEnd = 0;
-  int iPos = 0;
-  int nWord = 0;
+SQLITE_PRIVATE int sqlite3Fts3MsrIncrRestart(Fts3MultiSegReader *pCsr){
+  int i;                          /* Used to iterate through segment-readers */
 
-  char const *zToken;
-  int nToken = 0;
+  assert( pCsr->zTerm==0 );
+  assert( pCsr->nTerm==0 );
+  assert( pCsr->aDoclist==0 );
+  assert( pCsr->nDoclist==0 );
 
-  sqlite3_tokenizer *pTokenizer = p->pTokenizer;
-  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
-  sqlite3_tokenizer_cursor *pCsr;
-  int (*xNext)(sqlite3_tokenizer_cursor *pCursor,
-      const char**,int*,int*,int*,int*);
+  pCsr->nAdvance = 0;
+  pCsr->bRestart = 1;
+  for(i=0; i<pCsr->nSegment; i++){
+    pCsr->apSegment[i]->pOffsetList = 0;
+    pCsr->apSegment[i]->nOffsetList = 0;
+    pCsr->apSegment[i]->iDocid = 0;
+  }
 
-  assert( pTokenizer && pModule );
+  return SQLITE_OK;
+}
 
-  /* If the user has inserted a NULL value, this function may be called with
-  ** zText==0. In this case, add zero token entries to the hash table and 
-  ** return early. */
-  if( zText==0 ){
-    *pnWord = 0;
-    return SQLITE_OK;
-  }
 
-  rc = sqlite3Fts3OpenTokenizer(pTokenizer, iLangid, zText, -1, &pCsr);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
+SQLITE_PRIVATE int sqlite3Fts3SegReaderStep(
+  Fts3Table *p,                   /* Virtual table handle */
+  Fts3MultiSegReader *pCsr        /* Cursor object */
+){
+  int rc = SQLITE_OK;
 
-  xNext = pModule->xNext;
-  while( SQLITE_OK==rc
-      && SQLITE_OK==(rc = xNext(pCsr, &zToken, &nToken, &iStart, &iEnd, &iPos))
-  ){
+  int isIgnoreEmpty =  (pCsr->pFilter->flags & FTS3_SEGMENT_IGNORE_EMPTY);
+  int isRequirePos =   (pCsr->pFilter->flags & FTS3_SEGMENT_REQUIRE_POS);
+  int isColFilter =    (pCsr->pFilter->flags & FTS3_SEGMENT_COLUMN_FILTER);
+  int isPrefix =       (pCsr->pFilter->flags & FTS3_SEGMENT_PREFIX);
+  int isScan =         (pCsr->pFilter->flags & FTS3_SEGMENT_SCAN);
+  int isFirst =        (pCsr->pFilter->flags & FTS3_SEGMENT_FIRST);
+
+  Fts3SegReader **apSegment = pCsr->apSegment;
+  int nSegment = pCsr->nSegment;
+  Fts3SegFilter *pFilter = pCsr->pFilter;
+  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
+    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
+  );
+
+  if( pCsr->nSegment==0 ) return SQLITE_OK;
+
+  do {
+    int nMerge;
     int i;
-    if( iPos>=nWord ) nWord = iPos+1;
+  
+    /* Advance the first pCsr->nAdvance entries in the apSegment[] array
+    ** forward. Then sort the list in order of current term again.  
+    */
+    for(i=0; i<pCsr->nAdvance; i++){
+      Fts3SegReader *pSeg = apSegment[i];
+      if( pSeg->bLookup ){
+        fts3SegReaderSetEof(pSeg);
+      }else{
+        rc = fts3SegReaderNext(p, pSeg, 0);
+      }
+      if( rc!=SQLITE_OK ) return rc;
+    }
+    fts3SegReaderSort(apSegment, nSegment, pCsr->nAdvance, fts3SegReaderCmp);
+    pCsr->nAdvance = 0;
 
-    /* Positions cannot be negative; we use -1 as a terminator internally.
-    ** Tokens must have a non-zero length.
+    /* If all the seg-readers are at EOF, we're finished. return SQLITE_OK. */
+    assert( rc==SQLITE_OK );
+    if( apSegment[0]->aNode==0 ) break;
+
+    pCsr->nTerm = apSegment[0]->nTerm;
+    pCsr->zTerm = apSegment[0]->zTerm;
+
+    /* If this is a prefix-search, and if the term that apSegment[0] points
+    ** to does not share a suffix with pFilter->zTerm/nTerm, then all 
+    ** required callbacks have been made. In this case exit early.
+    **
+    ** Similarly, if this is a search for an exact match, and the first term
+    ** of segment apSegment[0] is not a match, exit early.
     */
-    if( iPos<0 || !zToken || nToken<=0 ){
-      rc = SQLITE_ERROR;
-      break;
+    if( pFilter->zTerm && !isScan ){
+      if( pCsr->nTerm<pFilter->nTerm 
+       || (!isPrefix && pCsr->nTerm>pFilter->nTerm)
+       || memcmp(pCsr->zTerm, pFilter->zTerm, pFilter->nTerm) 
+      ){
+        break;
+      }
     }
 
-    /* Add the term to the terms index */
-    rc = fts3PendingTermsAddOne(
-        p, iCol, iPos, &p->aIndex[0].hPending, zToken, nToken
-    );
-    
-    /* Add the term to each of the prefix indexes that it is not too 
-    ** short for. */
-    for(i=1; rc==SQLITE_OK && i<p->nIndex; i++){
-      struct Fts3Index *pIndex = &p->aIndex[i];
-      if( nToken<pIndex->nPrefix ) continue;
-      rc = fts3PendingTermsAddOne(
-          p, iCol, iPos, &pIndex->hPending, zToken, pIndex->nPrefix
-      );
+    nMerge = 1;
+    while( nMerge<nSegment 
+        && apSegment[nMerge]->aNode
+        && apSegment[nMerge]->nTerm==pCsr->nTerm 
+        && 0==memcmp(pCsr->zTerm, apSegment[nMerge]->zTerm, pCsr->nTerm)
+    ){
+      nMerge++;
     }
-  }
 
-  pModule->xClose(pCsr);
-  *pnWord += nWord;
-  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
+    assert( isIgnoreEmpty || (isRequirePos && !isColFilter) );
+    if( nMerge==1 
+     && !isIgnoreEmpty 
+     && !isFirst 
+     && (p->bDescIdx==0 || fts3SegReaderIsPending(apSegment[0])==0)
+    ){
+      pCsr->nDoclist = apSegment[0]->nDoclist;
+      if( fts3SegReaderIsPending(apSegment[0]) ){
+        rc = fts3MsrBufferData(pCsr, apSegment[0]->aDoclist, pCsr->nDoclist);
+        pCsr->aDoclist = pCsr->aBuffer;
+      }else{
+        pCsr->aDoclist = apSegment[0]->aDoclist;
+      }
+      if( rc==SQLITE_OK ) rc = SQLITE_ROW;
+    }else{
+      int nDoclist = 0;           /* Size of doclist */
+      sqlite3_int64 iPrev = 0;    /* Previous docid stored in doclist */
+
+      /* The current term of the first nMerge entries in the array
+      ** of Fts3SegReader objects is the same. The doclists must be merged
+      ** and a single term returned with the merged doclist.
+      */
+      for(i=0; i<nMerge; i++){
+        fts3SegReaderFirstDocid(p, apSegment[i]);
+      }
+      fts3SegReaderSort(apSegment, nMerge, nMerge, xCmp);
+      while( apSegment[0]->pOffsetList ){
+        int j;                    /* Number of segments that share a docid */
+        char *pList = 0;
+        int nList = 0;
+        int nByte;
+        sqlite3_int64 iDocid = apSegment[0]->iDocid;
+        fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
+        j = 1;
+        while( j<nMerge
+            && apSegment[j]->pOffsetList
+            && apSegment[j]->iDocid==iDocid
+        ){
+          fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
+          j++;
+        }
+
+        if( isColFilter ){
+          fts3ColumnFilter(pFilter->iCol, 0, &pList, &nList);
+        }
+
+        if( !isIgnoreEmpty || nList>0 ){
+
+          /* Calculate the 'docid' delta value to write into the merged 
+          ** doclist. */
+          sqlite3_int64 iDelta;
+          if( p->bDescIdx && nDoclist>0 ){
+            iDelta = iPrev - iDocid;
+          }else{
+            iDelta = iDocid - iPrev;
+          }
+          assert( iDelta>0 || (nDoclist==0 && iDelta==iDocid) );
+          assert( nDoclist>0 || iDelta==iDocid );
+
+          nByte = sqlite3Fts3VarintLen(iDelta) + (isRequirePos?nList+1:0);
+          if( nDoclist+nByte>pCsr->nBuffer ){
+            char *aNew;
+            pCsr->nBuffer = (nDoclist+nByte)*2;
+            aNew = sqlite3_realloc(pCsr->aBuffer, pCsr->nBuffer);
+            if( !aNew ){
+              return SQLITE_NOMEM;
+            }
+            pCsr->aBuffer = aNew;
+          }
+
+          if( isFirst ){
+            char *a = &pCsr->aBuffer[nDoclist];
+            int nWrite;
+           
+            nWrite = sqlite3Fts3FirstFilter(iDelta, pList, nList, a);
+            if( nWrite ){
+              iPrev = iDocid;
+              nDoclist += nWrite;
+            }
+          }else{
+            nDoclist += sqlite3Fts3PutVarint(&pCsr->aBuffer[nDoclist], iDelta);
+            iPrev = iDocid;
+            if( isRequirePos ){
+              memcpy(&pCsr->aBuffer[nDoclist], pList, nList);
+              nDoclist += nList;
+              pCsr->aBuffer[nDoclist++] = '\0';
+            }
+          }
+        }
+
+        fts3SegReaderSort(apSegment, nMerge, j, xCmp);
+      }
+      if( nDoclist>0 ){
+        pCsr->aDoclist = pCsr->aBuffer;
+        pCsr->nDoclist = nDoclist;
+        rc = SQLITE_ROW;
+      }
+    }
+    pCsr->nAdvance = nMerge;
+  }while( rc==SQLITE_OK );
+
+  return rc;
 }
 
-/* 
-** Calling this function indicates that subsequent calls to 
-** fts3PendingTermsAdd() are to add term/position-list pairs for the
-** contents of the document with docid iDocid.
-*/
-static int fts3PendingTermsDocid(
-  Fts3Table *p,                   /* Full-text table handle */
-  int iLangid,                    /* Language id of row being written */
-  sqlite_int64 iDocid             /* Docid of row being written */
+
+SQLITE_PRIVATE void sqlite3Fts3SegReaderFinish(
+  Fts3MultiSegReader *pCsr       /* Cursor object */
 ){
-  assert( iLangid>=0 );
+  if( pCsr ){
+    int i;
+    for(i=0; i<pCsr->nSegment; i++){
+      sqlite3Fts3SegReaderFree(pCsr->apSegment[i]);
+    }
+    sqlite3_free(pCsr->apSegment);
+    sqlite3_free(pCsr->aBuffer);
 
-  /* TODO(shess) Explore whether partially flushing the buffer on
-  ** forced-flush would provide better performance.  I suspect that if
-  ** we ordered the doclists by size and flushed the largest until the
-  ** buffer was half empty, that would let the less frequent terms
-  ** generate longer doclists.
-  */
-  if( iDocid<=p->iPrevDocid 
-   || p->iPrevLangid!=iLangid
-   || p->nPendingData>p->nMaxPendingData 
-  ){
-    int rc = sqlite3Fts3PendingTermsFlush(p);
-    if( rc!=SQLITE_OK ) return rc;
+    pCsr->nSegment = 0;
+    pCsr->apSegment = 0;
+    pCsr->aBuffer = 0;
   }
-  p->iPrevDocid = iDocid;
-  p->iPrevLangid = iLangid;
-  return SQLITE_OK;
 }
 
 /*
-** Discard the contents of the pending-terms hash tables. 
+** Decode the "end_block" field, selected by column iCol of the SELECT 
+** statement passed as the first argument. 
+**
+** The "end_block" field may contain either an integer, or a text field
+** containing the text representation of two non-negative integers separated 
+** by one or more space (0x20) characters. In the first case, set *piEndBlock 
+** to the integer value and *pnByte to zero before returning. In the second, 
+** set *piEndBlock to the first value and *pnByte to the second.
 */
-SQLITE_PRIVATE void sqlite3Fts3PendingTermsClear(Fts3Table *p){
-  int i;
-  for(i=0; i<p->nIndex; i++){
-    Fts3HashElem *pElem;
-    Fts3Hash *pHash = &p->aIndex[i].hPending;
-    for(pElem=fts3HashFirst(pHash); pElem; pElem=fts3HashNext(pElem)){
-      PendingList *pList = (PendingList *)fts3HashData(pElem);
-      fts3PendingListDelete(pList);
+static void fts3ReadEndBlockField(
+  sqlite3_stmt *pStmt, 
+  int iCol, 
+  i64 *piEndBlock,
+  i64 *pnByte
+){
+  const unsigned char *zText = sqlite3_column_text(pStmt, iCol);
+  if( zText ){
+    int i;
+    int iMul = 1;
+    i64 iVal = 0;
+    for(i=0; zText[i]>='0' && zText[i]<='9'; i++){
+      iVal = iVal*10 + (zText[i] - '0');
     }
-    fts3HashClear(pHash);
+    *piEndBlock = iVal;
+    while( zText[i]==' ' ) i++;
+    iVal = 0;
+    if( zText[i]=='-' ){
+      i++;
+      iMul = -1;
+    }
+    for(/* no-op */; zText[i]>='0' && zText[i]<='9'; i++){
+      iVal = iVal*10 + (zText[i] - '0');
+    }
+    *pnByte = (iVal * (i64)iMul);
   }
-  p->nPendingData = 0;
 }
 
+
 /*
-** This function is called by the xUpdate() method as part of an INSERT
-** operation. It adds entries for each term in the new record to the
-** pendingTerms hash table.
-**
-** Argument apVal is the same as the similarly named argument passed to
-** fts3InsertData(). Parameter iDocid is the docid of the new row.
+** A segment of size nByte bytes has just been written to absolute level
+** iAbsLevel. Promote any segments that should be promoted as a result.
 */
-static int fts3InsertTerms(
-  Fts3Table *p, 
-  int iLangid, 
-  sqlite3_value **apVal, 
-  u32 *aSz
+static int fts3PromoteSegments(
+  Fts3Table *p,                   /* FTS table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level just updated */
+  sqlite3_int64 nByte             /* Size of new segment at iAbsLevel */
 ){
-  int i;                          /* Iterator variable */
-  for(i=2; i<p->nColumn+2; i++){
-    int iCol = i-2;
-    if( p->abNotindexed[iCol]==0 ){
-      const char *zText = (const char *)sqlite3_value_text(apVal[i]);
-      int rc = fts3PendingTermsAdd(p, iLangid, zText, iCol, &aSz[iCol]);
-      if( rc!=SQLITE_OK ){
-        return rc;
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pRange;
+
+  rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE2, &pRange, 0);
+
+  if( rc==SQLITE_OK ){
+    int bOk = 0;
+    i64 iLast = (iAbsLevel/FTS3_SEGDIR_MAXLEVEL + 1) * FTS3_SEGDIR_MAXLEVEL - 1;
+    i64 nLimit = (nByte*3)/2;
+
+    /* Loop through all entries in the %_segdir table corresponding to 
+    ** segments in this index on levels greater than iAbsLevel. If there is
+    ** at least one such segment, and it is possible to determine that all 
+    ** such segments are smaller than nLimit bytes in size, they will be 
+    ** promoted to level iAbsLevel.  */
+    sqlite3_bind_int64(pRange, 1, iAbsLevel+1);
+    sqlite3_bind_int64(pRange, 2, iLast);
+    while( SQLITE_ROW==sqlite3_step(pRange) ){
+      i64 nSize = 0, dummy;
+      fts3ReadEndBlockField(pRange, 2, &dummy, &nSize);
+      if( nSize<=0 || nSize>nLimit ){
+        /* If nSize==0, then the %_segdir.end_block field does not not 
+        ** contain a size value. This happens if it was written by an
+        ** old version of FTS. In this case it is not possible to determine
+        ** the size of the segment, and so segment promotion does not
+        ** take place.  */
+        bOk = 0;
+        break;
+      }
+      bOk = 1;
+    }
+    rc = sqlite3_reset(pRange);
+
+    if( bOk ){
+      int iIdx = 0;
+      sqlite3_stmt *pUpdate1 = 0;
+      sqlite3_stmt *pUpdate2 = 0;
+
+      if( rc==SQLITE_OK ){
+        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL_IDX, &pUpdate1, 0);
+      }
+      if( rc==SQLITE_OK ){
+        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL, &pUpdate2, 0);
+      }
+
+      if( rc==SQLITE_OK ){
+
+        /* Loop through all %_segdir entries for segments in this index with
+        ** levels equal to or greater than iAbsLevel. As each entry is visited,
+        ** updated it to set (level = -1) and (idx = N), where N is 0 for the
+        ** oldest segment in the range, 1 for the next oldest, and so on.
+        **
+        ** In other words, move all segments being promoted to level -1,
+        ** setting the "idx" fields as appropriate to keep them in the same
+        ** order. The contents of level -1 (which is never used, except
+        ** transiently here), will be moved back to level iAbsLevel below.  */
+        sqlite3_bind_int64(pRange, 1, iAbsLevel);
+        while( SQLITE_ROW==sqlite3_step(pRange) ){
+          sqlite3_bind_int(pUpdate1, 1, iIdx++);
+          sqlite3_bind_int(pUpdate1, 2, sqlite3_column_int(pRange, 0));
+          sqlite3_bind_int(pUpdate1, 3, sqlite3_column_int(pRange, 1));
+          sqlite3_step(pUpdate1);
+          rc = sqlite3_reset(pUpdate1);
+          if( rc!=SQLITE_OK ){
+            sqlite3_reset(pRange);
+            break;
+          }
+        }
+      }
+      if( rc==SQLITE_OK ){
+        rc = sqlite3_reset(pRange);
+      }
+
+      /* Move level -1 to level iAbsLevel */
+      if( rc==SQLITE_OK ){
+        sqlite3_bind_int64(pUpdate2, 1, iAbsLevel);
+        sqlite3_step(pUpdate2);
+        rc = sqlite3_reset(pUpdate2);
       }
-      aSz[p->nColumn] += sqlite3_value_bytes(apVal[i]);
     }
   }
-  return SQLITE_OK;
+
+
+  return rc;
 }
 
 /*
-** This function is called by the xUpdate() method for an INSERT operation.
-** The apVal parameter is passed a copy of the apVal argument passed by
-** SQLite to the xUpdate() method. i.e:
+** Merge all level iLevel segments in the database into a single 
+** iLevel+1 segment. Or, if iLevel<0, merge all segments into a
+** single segment with a level equal to the numerically largest level 
+** currently present in the database.
 **
-**   apVal[0]                Not used for INSERT.
-**   apVal[1]                rowid
-**   apVal[2]                Left-most user-defined column
-**   ...
-**   apVal[p->nColumn+1]     Right-most user-defined column
-**   apVal[p->nColumn+2]     Hidden column with same name as table
-**   apVal[p->nColumn+3]     Hidden "docid" column (alias for rowid)
-**   apVal[p->nColumn+4]     Hidden languageid column
+** If this function is called with iLevel<0, but there is only one
+** segment in the database, SQLITE_DONE is returned immediately. 
+** Otherwise, if successful, SQLITE_OK is returned. If an error occurs, 
+** an SQLite error code is returned.
 */
-static int fts3InsertData(
-  Fts3Table *p,                   /* Full-text table */
-  sqlite3_value **apVal,          /* Array of values to insert */
-  sqlite3_int64 *piDocid          /* OUT: Docid for row just inserted */
+static int fts3SegmentMerge(
+  Fts3Table *p, 
+  int iLangid,                    /* Language id to merge */
+  int iIndex,                     /* Index in p->aIndex[] to merge */
+  int iLevel                      /* Level to merge */
 ){
   int rc;                         /* Return code */
-  sqlite3_stmt *pContentInsert;   /* INSERT INTO %_content VALUES(...) */
+  int iIdx = 0;                   /* Index of new segment */
+  sqlite3_int64 iNewLevel = 0;    /* Level/index to create new segment at */
+  SegmentWriter *pWriter = 0;     /* Used to write the new, merged, segment */
+  Fts3SegFilter filter;           /* Segment term filter condition */
+  Fts3MultiSegReader csr;         /* Cursor to iterate through level(s) */
+  int bIgnoreEmpty = 0;           /* True to ignore empty segments */
+  i64 iMaxLevel = 0;              /* Max level number for this index/langid */
 
-  if( p->zContentTbl ){
-    sqlite3_value *pRowid = apVal[p->nColumn+3];
-    if( sqlite3_value_type(pRowid)==SQLITE_NULL ){
-      pRowid = apVal[1];
-    }
-    if( sqlite3_value_type(pRowid)!=SQLITE_INTEGER ){
-      return SQLITE_CONSTRAINT;
+  assert( iLevel==FTS3_SEGCURSOR_ALL
+       || iLevel==FTS3_SEGCURSOR_PENDING
+       || iLevel>=0
+  );
+  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
+  assert( iIndex>=0 && iIndex<p->nIndex );
+
+  rc = sqlite3Fts3SegReaderCursor(p, iLangid, iIndex, iLevel, 0, 0, 1, 0, &csr);
+  if( rc!=SQLITE_OK || csr.nSegment==0 ) goto finished;
+
+  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
+    rc = fts3SegmentMaxLevel(p, iLangid, iIndex, &iMaxLevel);
+    if( rc!=SQLITE_OK ) goto finished;
+  }
+
+  if( iLevel==FTS3_SEGCURSOR_ALL ){
+    /* This call is to merge all segments in the database to a single
+    ** segment. The level of the new segment is equal to the numerically
+    ** greatest segment level currently present in the database for this
+    ** index. The idx of the new segment is always 0.  */
+    if( csr.nSegment==1 ){
+      rc = SQLITE_DONE;
+      goto finished;
     }
-    *piDocid = sqlite3_value_int64(pRowid);
-    return SQLITE_OK;
+    iNewLevel = iMaxLevel;
+    bIgnoreEmpty = 1;
+
+  }else{
+    /* This call is to merge all segments at level iLevel. find the next
+    ** available segment index at level iLevel+1. The call to
+    ** fts3AllocateSegdirIdx() will merge the segments at level iLevel+1 to 
+    ** a single iLevel+2 segment if necessary.  */
+    assert( FTS3_SEGCURSOR_PENDING==-1 );
+    iNewLevel = getAbsoluteLevel(p, iLangid, iIndex, iLevel+1);
+    rc = fts3AllocateSegdirIdx(p, iLangid, iIndex, iLevel+1, &iIdx);
+    bIgnoreEmpty = (iLevel!=FTS3_SEGCURSOR_PENDING) && (iNewLevel>iMaxLevel);
   }
+  if( rc!=SQLITE_OK ) goto finished;
 
-  /* Locate the statement handle used to insert data into the %_content
-  ** table. The SQL for this statement is:
-  **
-  **   INSERT INTO %_content VALUES(?, ?, ?, ...)
-  **
-  ** The statement features N '?' variables, where N is the number of user
-  ** defined columns in the FTS3 table, plus one for the docid field.
-  */
-  rc = fts3SqlStmt(p, SQL_CONTENT_INSERT, &pContentInsert, &apVal[1]);
-  if( rc==SQLITE_OK && p->zLanguageid ){
-    rc = sqlite3_bind_int(
-        pContentInsert, p->nColumn+2, 
-        sqlite3_value_int(apVal[p->nColumn+4])
-    );
+  assert( csr.nSegment>0 );
+  assert( iNewLevel>=getAbsoluteLevel(p, iLangid, iIndex, 0) );
+  assert( iNewLevel<getAbsoluteLevel(p, iLangid, iIndex,FTS3_SEGDIR_MAXLEVEL) );
+
+  memset(&filter, 0, sizeof(Fts3SegFilter));
+  filter.flags = FTS3_SEGMENT_REQUIRE_POS;
+  filter.flags |= (bIgnoreEmpty ? FTS3_SEGMENT_IGNORE_EMPTY : 0);
+
+  rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
+  while( SQLITE_OK==rc ){
+    rc = sqlite3Fts3SegReaderStep(p, &csr);
+    if( rc!=SQLITE_ROW ) break;
+    rc = fts3SegWriterAdd(p, &pWriter, 1, 
+        csr.zTerm, csr.nTerm, csr.aDoclist, csr.nDoclist);
   }
-  if( rc!=SQLITE_OK ) return rc;
+  if( rc!=SQLITE_OK ) goto finished;
+  assert( pWriter || bIgnoreEmpty );
 
-  /* There is a quirk here. The users INSERT statement may have specified
-  ** a value for the "rowid" field, for the "docid" field, or for both.
-  ** Which is a problem, since "rowid" and "docid" are aliases for the
-  ** same value. For example:
-  **
-  **   INSERT INTO fts3tbl(rowid, docid) VALUES(1, 2);
-  **
-  ** In FTS3, this is an error. It is an error to specify non-NULL values
-  ** for both docid and some other rowid alias.
-  */
-  if( SQLITE_NULL!=sqlite3_value_type(apVal[3+p->nColumn]) ){
-    if( SQLITE_NULL==sqlite3_value_type(apVal[0])
-     && SQLITE_NULL!=sqlite3_value_type(apVal[1])
-    ){
-      /* A rowid/docid conflict. */
-      return SQLITE_ERROR;
+  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
+    rc = fts3DeleteSegdir(
+        p, iLangid, iIndex, iLevel, csr.apSegment, csr.nSegment
+    );
+    if( rc!=SQLITE_OK ) goto finished;
+  }
+  if( pWriter ){
+    rc = fts3SegWriterFlush(p, pWriter, iNewLevel, iIdx);
+    if( rc==SQLITE_OK ){
+      if( iLevel==FTS3_SEGCURSOR_PENDING || iNewLevel<iMaxLevel ){
+        rc = fts3PromoteSegments(p, iNewLevel, pWriter->nLeafData);
+      }
     }
-    rc = sqlite3_bind_value(pContentInsert, 1, apVal[3+p->nColumn]);
-    if( rc!=SQLITE_OK ) return rc;
   }
 
-  /* Execute the statement to insert the record. Set *piDocid to the 
-  ** new docid value. 
-  */
-  sqlite3_step(pContentInsert);
-  rc = sqlite3_reset(pContentInsert);
-
-  *piDocid = sqlite3_last_insert_rowid(p->db);
+ finished:
+  fts3SegWriterFree(pWriter);
+  sqlite3Fts3SegReaderFinish(&csr);
   return rc;
 }
 
 
-
-/*
-** Remove all data from the FTS3 table. Clear the hash table containing
-** pending terms.
+/* 
+** Flush the contents of pendingTerms to level 0 segments. 
 */
-static int fts3DeleteAll(Fts3Table *p, int bContent){
-  int rc = SQLITE_OK;             /* Return code */
-
-  /* Discard the contents of the pending-terms hash table. */
+SQLITE_PRIVATE int sqlite3Fts3PendingTermsFlush(Fts3Table *p){
+  int rc = SQLITE_OK;
+  int i;
+        
+  for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
+    rc = fts3SegmentMerge(p, p->iPrevLangid, i, FTS3_SEGCURSOR_PENDING);
+    if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+  }
   sqlite3Fts3PendingTermsClear(p);
 
-  /* Delete everything from the shadow tables. Except, leave %_content as
-  ** is if bContent is false.  */
-  assert( p->zContentTbl==0 || bContent==0 );
-  if( bContent ) fts3SqlExec(&rc, p, SQL_DELETE_ALL_CONTENT, 0);
-  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGMENTS, 0);
-  fts3SqlExec(&rc, p, SQL_DELETE_ALL_SEGDIR, 0);
-  if( p->bHasDocsize ){
-    fts3SqlExec(&rc, p, SQL_DELETE_ALL_DOCSIZE, 0);
-  }
-  if( p->bHasStat ){
-    fts3SqlExec(&rc, p, SQL_DELETE_ALL_STAT, 0);
+  /* Determine the auto-incr-merge setting if unknown.  If enabled,
+  ** estimate the number of leaf blocks of content to be written
+  */
+  if( rc==SQLITE_OK && p->bHasStat
+   && p->nAutoincrmerge==0xff && p->nLeafAdd>0
+  ){
+    sqlite3_stmt *pStmt = 0;
+    rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int(pStmt, 1, FTS_STAT_AUTOINCRMERGE);
+      rc = sqlite3_step(pStmt);
+      if( rc==SQLITE_ROW ){
+        p->nAutoincrmerge = sqlite3_column_int(pStmt, 0);
+        if( p->nAutoincrmerge==1 ) p->nAutoincrmerge = 8;
+      }else if( rc==SQLITE_DONE ){
+        p->nAutoincrmerge = 0;
+      }
+      rc = sqlite3_reset(pStmt);
+    }
   }
   return rc;
 }
 
 /*
-**
+** Encode N integers as varints into a blob.
 */
-static int langidFromSelect(Fts3Table *p, sqlite3_stmt *pSelect){
-  int iLangid = 0;
-  if( p->zLanguageid ) iLangid = sqlite3_column_int(pSelect, p->nColumn+1);
-  return iLangid;
+static void fts3EncodeIntArray(
+  int N,             /* The number of integers to encode */
+  u32 *a,            /* The integer values */
+  char *zBuf,        /* Write the BLOB here */
+  int *pNBuf         /* Write number of bytes if zBuf[] used here */
+){
+  int i, j;
+  for(i=j=0; i<N; i++){
+    j += sqlite3Fts3PutVarint(&zBuf[j], (sqlite3_int64)a[i]);
+  }
+  *pNBuf = j;
 }
 
 /*
-** The first element in the apVal[] array is assumed to contain the docid
-** (an integer) of a row about to be deleted. Remove all terms from the
-** full-text index.
+** Decode a blob of varints into N integers
 */
-static void fts3DeleteTerms( 
-  int *pRC,               /* Result code */
-  Fts3Table *p,           /* The FTS table to delete from */
-  sqlite3_value *pRowid,  /* The docid to be deleted */
-  u32 *aSz,               /* Sizes of deleted document written here */
-  int *pbFound            /* OUT: Set to true if row really does exist */
+static void fts3DecodeIntArray(
+  int N,             /* The number of integers to decode */
+  u32 *a,            /* Write the integer values */
+  const char *zBuf,  /* The BLOB containing the varints */
+  int nBuf           /* size of the BLOB */
 ){
-  int rc;
-  sqlite3_stmt *pSelect;
-
-  assert( *pbFound==0 );
-  if( *pRC ) return;
-  rc = fts3SqlStmt(p, SQL_SELECT_CONTENT_BY_ROWID, &pSelect, &pRowid);
-  if( rc==SQLITE_OK ){
-    if( SQLITE_ROW==sqlite3_step(pSelect) ){
-      int i;
-      int iLangid = langidFromSelect(p, pSelect);
-      rc = fts3PendingTermsDocid(p, iLangid, sqlite3_column_int64(pSelect, 0));
-      for(i=1; rc==SQLITE_OK && i<=p->nColumn; i++){
-        int iCol = i-1;
-        if( p->abNotindexed[iCol]==0 ){
-          const char *zText = (const char *)sqlite3_column_text(pSelect, i);
-          rc = fts3PendingTermsAdd(p, iLangid, zText, -1, &aSz[iCol]);
-          aSz[p->nColumn] += sqlite3_column_bytes(pSelect, i);
-        }
-      }
-      if( rc!=SQLITE_OK ){
-        sqlite3_reset(pSelect);
-        *pRC = rc;
-        return;
-      }
-      *pbFound = 1;
-    }
-    rc = sqlite3_reset(pSelect);
-  }else{
-    sqlite3_reset(pSelect);
+  int i, j;
+  UNUSED_PARAMETER(nBuf);
+  for(i=j=0; i<N; i++){
+    sqlite3_int64 x;
+    j += sqlite3Fts3GetVarint(&zBuf[j], &x);
+    assert(j<=nBuf);
+    a[i] = (u32)(x & 0xffffffff);
   }
-  *pRC = rc;
 }
 
 /*
-** Forward declaration to account for the circular dependency between
-** functions fts3SegmentMerge() and fts3AllocateSegdirIdx().
+** Insert the sizes (in tokens) for each column of the document
+** with docid equal to p->iPrevDocid.  The sizes are encoded as
+** a blob of varints.
 */
-static int fts3SegmentMerge(Fts3Table *, int, int, int);
+static void fts3InsertDocsize(
+  int *pRC,                       /* Result code */
+  Fts3Table *p,                   /* Table into which to insert */
+  u32 *aSz                        /* Sizes of each column, in tokens */
+){
+  char *pBlob;             /* The BLOB encoding of the document size */
+  int nBlob;               /* Number of bytes in the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement used to insert the encoding */
+  int rc;                  /* Result code from subfunctions */
 
-/* 
-** This function allocates a new level iLevel index in the segdir table.
-** Usually, indexes are allocated within a level sequentially starting
-** with 0, so the allocated index is one greater than the value returned
-** by:
+  if( *pRC ) return;
+  pBlob = sqlite3_malloc( 10*p->nColumn );
+  if( pBlob==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  fts3EncodeIntArray(p->nColumn, aSz, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_DOCSIZE, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(pBlob);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int64(pStmt, 1, p->iPrevDocid);
+  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, sqlite3_free);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+}
+
+/*
+** Record 0 of the %_stat table contains a blob consisting of N varints,
+** where N is the number of user defined columns in the fts3 table plus
+** two. If nCol is the number of user defined columns, then values of the 
+** varints are set as follows:
 **
-**   SELECT max(idx) FROM %_segdir WHERE level = :iLevel
+**   Varint 0:       Total number of rows in the table.
 **
-** However, if there are already FTS3_MERGE_COUNT indexes at the requested
-** level, they are merged into a single level (iLevel+1) segment and the 
-** allocated index is 0.
+**   Varint 1..nCol: For each column, the total number of tokens stored in
+**                   the column for all rows of the table.
+**
+**   Varint 1+nCol:  The total size, in bytes, of all text values in all
+**                   columns of all rows of the table.
 **
-** If successful, *piIdx is set to the allocated index slot and SQLITE_OK
-** returned. Otherwise, an SQLite error code is returned.
 */
-static int fts3AllocateSegdirIdx(
-  Fts3Table *p, 
-  int iLangid,                    /* Language id */
-  int iIndex,                     /* Index for p->aIndex */
-  int iLevel, 
-  int *piIdx
+static void fts3UpdateDocTotals(
+  int *pRC,                       /* The result code */
+  Fts3Table *p,                   /* Table being updated */
+  u32 *aSzIns,                    /* Size increases */
+  u32 *aSzDel,                    /* Size decreases */
+  int nChng                       /* Change in the number of documents */
 ){
-  int rc;                         /* Return Code */
-  sqlite3_stmt *pNextIdx;         /* Query for next idx at level iLevel */
-  int iNext = 0;                  /* Result of query pNextIdx */
+  char *pBlob;             /* Storage for BLOB written into %_stat */
+  int nBlob;               /* Size of BLOB written into %_stat */
+  u32 *a;                  /* Array of integers that becomes the BLOB */
+  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
+  int i;                   /* Loop counter */
+  int rc;                  /* Result code from subfunctions */
 
-  assert( iLangid>=0 );
-  assert( p->nIndex>=1 );
+  const int nStat = p->nColumn+2;
 
-  /* Set variable iNext to the next available segdir index at level iLevel. */
-  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENT_INDEX, &pNextIdx, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(
-        pNextIdx, 1, getAbsoluteLevel(p, iLangid, iIndex, iLevel)
-    );
-    if( SQLITE_ROW==sqlite3_step(pNextIdx) ){
-      iNext = sqlite3_column_int(pNextIdx, 0);
+  if( *pRC ) return;
+  a = sqlite3_malloc( (sizeof(u32)+10)*nStat );
+  if( a==0 ){
+    *pRC = SQLITE_NOMEM;
+    return;
+  }
+  pBlob = (char*)&a[nStat];
+  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
+  if( sqlite3_step(pStmt)==SQLITE_ROW ){
+    fts3DecodeIntArray(nStat, a,
+         sqlite3_column_blob(pStmt, 0),
+         sqlite3_column_bytes(pStmt, 0));
+  }else{
+    memset(a, 0, sizeof(u32)*(nStat) );
+  }
+  rc = sqlite3_reset(pStmt);
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
+  }
+  if( nChng<0 && a[0]<(u32)(-nChng) ){
+    a[0] = 0;
+  }else{
+    a[0] += nChng;
+  }
+  for(i=0; i<p->nColumn+1; i++){
+    u32 x = a[i+1];
+    if( x+aSzIns[i] < aSzDel[i] ){
+      x = 0;
+    }else{
+      x = x + aSzIns[i] - aSzDel[i];
     }
-    rc = sqlite3_reset(pNextIdx);
+    a[i+1] = x;
+  }
+  fts3EncodeIntArray(nStat, a, pBlob, &nBlob);
+  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pStmt, 0);
+  if( rc ){
+    sqlite3_free(a);
+    *pRC = rc;
+    return;
   }
+  sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
+  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, SQLITE_STATIC);
+  sqlite3_step(pStmt);
+  *pRC = sqlite3_reset(pStmt);
+  sqlite3_free(a);
+}
 
+/*
+** Merge the entire database so that there is one segment for each 
+** iIndex/iLangid combination.
+*/
+static int fts3DoOptimize(Fts3Table *p, int bReturnDone){
+  int bSeenDone = 0;
+  int rc;
+  sqlite3_stmt *pAllLangid = 0;
+
+  rc = fts3SqlStmt(p, SQL_SELECT_ALL_LANGID, &pAllLangid, 0);
   if( rc==SQLITE_OK ){
-    /* If iNext is FTS3_MERGE_COUNT, indicating that level iLevel is already
-    ** full, merge all segments in level iLevel into a single iLevel+1
-    ** segment and allocate (newly freed) index 0 at level iLevel. Otherwise,
-    ** if iNext is less than FTS3_MERGE_COUNT, allocate index iNext.
-    */
-    if( iNext>=FTS3_MERGE_COUNT ){
-      fts3LogMerge(16, getAbsoluteLevel(p, iLangid, iIndex, iLevel));
-      rc = fts3SegmentMerge(p, iLangid, iIndex, iLevel);
-      *piIdx = 0;
-    }else{
-      *piIdx = iNext;
+    int rc2;
+    sqlite3_bind_int(pAllLangid, 1, p->iPrevLangid);
+    sqlite3_bind_int(pAllLangid, 2, p->nIndex);
+    while( sqlite3_step(pAllLangid)==SQLITE_ROW ){
+      int i;
+      int iLangid = sqlite3_column_int(pAllLangid, 0);
+      for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
+        rc = fts3SegmentMerge(p, iLangid, i, FTS3_SEGCURSOR_ALL);
+        if( rc==SQLITE_DONE ){
+          bSeenDone = 1;
+          rc = SQLITE_OK;
+        }
+      }
     }
+    rc2 = sqlite3_reset(pAllLangid);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
 
-  return rc;
+  sqlite3Fts3SegmentsClose(p);
+  sqlite3Fts3PendingTermsClear(p);
+
+  return (rc==SQLITE_OK && bReturnDone && bSeenDone) ? SQLITE_DONE : rc;
 }
 
 /*
-** The %_segments table is declared as follows:
-**
-**   CREATE TABLE %_segments(blockid INTEGER PRIMARY KEY, block BLOB)
-**
-** This function reads data from a single row of the %_segments table. The
-** specific row is identified by the iBlockid parameter. If paBlob is not
-** NULL, then a buffer is allocated using sqlite3_malloc() and populated
-** with the contents of the blob stored in the "block" column of the 
-** identified table row is. Whether or not paBlob is NULL, *pnBlob is set
-** to the size of the blob in bytes before returning.
+** This function is called when the user executes the following statement:
 **
-** If an error occurs, or the table does not contain the specified row,
-** an SQLite error code is returned. Otherwise, SQLITE_OK is returned. If
-** paBlob is non-NULL, then it is the responsibility of the caller to
-** eventually free the returned buffer.
+**     INSERT INTO <tbl>(<tbl>) VALUES('rebuild');
 **
-** This function may leave an open sqlite3_blob* handle in the
-** Fts3Table.pSegments variable. This handle is reused by subsequent calls
-** to this function. The handle may be closed by calling the
-** sqlite3Fts3SegmentsClose() function. Reusing a blob handle is a handy
-** performance improvement, but the blob handle should always be closed
-** before control is returned to the user (to prevent a lock being held
-** on the database file for longer than necessary). Thus, any virtual table
-** method (xFilter etc.) that may directly or indirectly call this function
-** must call sqlite3Fts3SegmentsClose() before returning.
+** The entire FTS index is discarded and rebuilt. If the table is one 
+** created using the content=xxx option, then the new index is based on
+** the current contents of the xxx table. Otherwise, it is rebuilt based
+** on the contents of the %_content table.
 */
-SQLITE_PRIVATE int sqlite3Fts3ReadBlock(
-  Fts3Table *p,                   /* FTS3 table handle */
-  sqlite3_int64 iBlockid,         /* Access the row with blockid=$iBlockid */
-  char **paBlob,                  /* OUT: Blob data in malloc'd buffer */
-  int *pnBlob,                    /* OUT: Size of blob data */
-  int *pnLoad                     /* OUT: Bytes actually loaded */
-){
-  int rc;                         /* Return code */
+static int fts3DoRebuild(Fts3Table *p){
+  int rc;                         /* Return Code */
 
-  /* pnBlob must be non-NULL. paBlob may be NULL or non-NULL. */
-  assert( pnBlob );
+  rc = fts3DeleteAll(p, 0);
+  if( rc==SQLITE_OK ){
+    u32 *aSz = 0;
+    u32 *aSzIns = 0;
+    u32 *aSzDel = 0;
+    sqlite3_stmt *pStmt = 0;
+    int nEntry = 0;
 
-  if( p->pSegments ){
-    rc = sqlite3_blob_reopen(p->pSegments, iBlockid);
-  }else{
-    if( 0==p->zSegmentsTbl ){
-      p->zSegmentsTbl = sqlite3_mprintf("%s_segments", p->zName);
-      if( 0==p->zSegmentsTbl ) return SQLITE_NOMEM;
+    /* Compose and prepare an SQL statement to loop through the content table */
+    char *zSql = sqlite3_mprintf("SELECT %s" , p->zReadExprlist);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+      sqlite3_free(zSql);
     }
-    rc = sqlite3_blob_open(
-       p->db, p->zDb, p->zSegmentsTbl, "block", iBlockid, 0, &p->pSegments
-    );
-  }
 
-  if( rc==SQLITE_OK ){
-    int nByte = sqlite3_blob_bytes(p->pSegments);
-    *pnBlob = nByte;
-    if( paBlob ){
-      char *aByte = sqlite3_malloc(nByte + FTS3_NODE_PADDING);
-      if( !aByte ){
+    if( rc==SQLITE_OK ){
+      int nByte = sizeof(u32) * (p->nColumn+1)*3;
+      aSz = (u32 *)sqlite3_malloc(nByte);
+      if( aSz==0 ){
         rc = SQLITE_NOMEM;
       }else{
-        if( pnLoad && nByte>(FTS3_NODE_CHUNK_THRESHOLD) ){
-          nByte = FTS3_NODE_CHUNKSIZE;
-          *pnLoad = nByte;
+        memset(aSz, 0, nByte);
+        aSzIns = &aSz[p->nColumn+1];
+        aSzDel = &aSzIns[p->nColumn+1];
+      }
+    }
+
+    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      int iCol;
+      int iLangid = langidFromSelect(p, pStmt);
+      rc = fts3PendingTermsDocid(p, iLangid, sqlite3_column_int64(pStmt, 0));
+      memset(aSz, 0, sizeof(aSz[0]) * (p->nColumn+1));
+      for(iCol=0; rc==SQLITE_OK && iCol<p->nColumn; iCol++){
+        if( p->abNotindexed[iCol]==0 ){
+          const char *z = (const char *) sqlite3_column_text(pStmt, iCol+1);
+          rc = fts3PendingTermsAdd(p, iLangid, z, iCol, &aSz[iCol]);
+          aSz[p->nColumn] += sqlite3_column_bytes(pStmt, iCol+1);
         }
-        rc = sqlite3_blob_read(p->pSegments, aByte, nByte, 0);
-        memset(&aByte[nByte], 0, FTS3_NODE_PADDING);
-        if( rc!=SQLITE_OK ){
-          sqlite3_free(aByte);
-          aByte = 0;
+      }
+      if( p->bHasDocsize ){
+        fts3InsertDocsize(&rc, p, aSz);
+      }
+      if( rc!=SQLITE_OK ){
+        sqlite3_finalize(pStmt);
+        pStmt = 0;
+      }else{
+        nEntry++;
+        for(iCol=0; iCol<=p->nColumn; iCol++){
+          aSzIns[iCol] += aSz[iCol];
         }
       }
-      *paBlob = aByte;
+    }
+    if( p->bFts4 ){
+      fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nEntry);
+    }
+    sqlite3_free(aSz);
+
+    if( pStmt ){
+      int rc2 = sqlite3_finalize(pStmt);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
     }
   }
 
   return rc;
 }
 
+
 /*
-** Close the blob handle at p->pSegments, if it is open. See comments above
-** the sqlite3Fts3ReadBlock() function for details.
+** This function opens a cursor used to read the input data for an 
+** incremental merge operation. Specifically, it opens a cursor to scan
+** the oldest nSeg segments (idx=0 through idx=(nSeg-1)) in absolute 
+** level iAbsLevel.
 */
-SQLITE_PRIVATE void sqlite3Fts3SegmentsClose(Fts3Table *p){
-  sqlite3_blob_close(p->pSegments);
-  p->pSegments = 0;
-}
-    
-static int fts3SegReaderIncrRead(Fts3SegReader *pReader){
-  int nRead;                      /* Number of bytes to read */
-  int rc;                         /* Return code */
+static int fts3IncrmergeCsr(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level to open */
+  int nSeg,                       /* Number of segments to merge */
+  Fts3MultiSegReader *pCsr        /* Cursor object to populate */
+){
+  int rc;                         /* Return Code */
+  sqlite3_stmt *pStmt = 0;        /* Statement used to read %_segdir entry */  
+  int nByte;                      /* Bytes allocated at pCsr->apSegment[] */
 
-  nRead = MIN(pReader->nNode - pReader->nPopulate, FTS3_NODE_CHUNKSIZE);
-  rc = sqlite3_blob_read(
-      pReader->pBlob, 
-      &pReader->aNode[pReader->nPopulate],
-      nRead,
-      pReader->nPopulate
-  );
+  /* Allocate space for the Fts3MultiSegReader.aCsr[] array */
+  memset(pCsr, 0, sizeof(*pCsr));
+  nByte = sizeof(Fts3SegReader *) * nSeg;
+  pCsr->apSegment = (Fts3SegReader **)sqlite3_malloc(nByte);
 
+  if( pCsr->apSegment==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    memset(pCsr->apSegment, 0, nByte);
+    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL, &pStmt, 0);
+  }
   if( rc==SQLITE_OK ){
-    pReader->nPopulate += nRead;
-    memset(&pReader->aNode[pReader->nPopulate], 0, FTS3_NODE_PADDING);
-    if( pReader->nPopulate==pReader->nNode ){
-      sqlite3_blob_close(pReader->pBlob);
-      pReader->pBlob = 0;
-      pReader->nPopulate = 0;
+    int i;
+    int rc2;
+    sqlite3_bind_int64(pStmt, 1, iAbsLevel);
+    assert( pCsr->nSegment==0 );
+    for(i=0; rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW && i<nSeg; i++){
+      rc = sqlite3Fts3SegReaderNew(i, 0,
+          sqlite3_column_int64(pStmt, 1),        /* segdir.start_block */
+          sqlite3_column_int64(pStmt, 2),        /* segdir.leaves_end_block */
+          sqlite3_column_int64(pStmt, 3),        /* segdir.end_block */
+          sqlite3_column_blob(pStmt, 4),         /* segdir.root */
+          sqlite3_column_bytes(pStmt, 4),        /* segdir.root */
+          &pCsr->apSegment[i]
+      );
+      pCsr->nSegment++;
     }
+    rc2 = sqlite3_reset(pStmt);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
-  return rc;
-}
 
-static int fts3SegReaderRequire(Fts3SegReader *pReader, char *pFrom, int nByte){
-  int rc = SQLITE_OK;
-  assert( !pReader->pBlob 
-       || (pFrom>=pReader->aNode && pFrom<&pReader->aNode[pReader->nNode])
-  );
-  while( pReader->pBlob && rc==SQLITE_OK 
-     &&  (pFrom - pReader->aNode + nByte)>pReader->nPopulate
-  ){
-    rc = fts3SegReaderIncrRead(pReader);
-  }
   return rc;
 }
 
+typedef struct IncrmergeWriter IncrmergeWriter;
+typedef struct NodeWriter NodeWriter;
+typedef struct Blob Blob;
+typedef struct NodeReader NodeReader;
+
 /*
-** Set an Fts3SegReader cursor to point at EOF.
+** An instance of the following structure is used as a dynamic buffer
+** to build up nodes or other blobs of data in.
+**
+** The function blobGrowBuffer() is used to extend the allocation.
 */
-static void fts3SegReaderSetEof(Fts3SegReader *pSeg){
-  if( !fts3SegReaderIsRootOnly(pSeg) ){
-    sqlite3_free(pSeg->aNode);
-    sqlite3_blob_close(pSeg->pBlob);
-    pSeg->pBlob = 0;
-  }
-  pSeg->aNode = 0;
-}
+struct Blob {
+  char *a;                        /* Pointer to allocation */
+  int n;                          /* Number of valid bytes of data in a[] */
+  int nAlloc;                     /* Allocated size of a[] (nAlloc>=n) */
+};
 
 /*
-** Move the iterator passed as the first argument to the next term in the
-** segment. If successful, SQLITE_OK is returned. If there is no next term,
-** SQLITE_DONE. Otherwise, an SQLite error code.
+** This structure is used to build up buffers containing segment b-tree 
+** nodes (blocks).
 */
-static int fts3SegReaderNext(
-  Fts3Table *p, 
-  Fts3SegReader *pReader,
-  int bIncr
-){
-  int rc;                         /* Return code of various sub-routines */
-  char *pNext;                    /* Cursor variable */
-  int nPrefix;                    /* Number of bytes in term prefix */
-  int nSuffix;                    /* Number of bytes in term suffix */
-
-  if( !pReader->aDoclist ){
-    pNext = pReader->aNode;
-  }else{
-    pNext = &pReader->aDoclist[pReader->nDoclist];
-  }
-
-  if( !pNext || pNext>=&pReader->aNode[pReader->nNode] ){
+struct NodeWriter {
+  sqlite3_int64 iBlock;           /* Current block id */
+  Blob key;                       /* Last key written to the current block */
+  Blob block;                     /* Current block image */
+};
 
-    if( fts3SegReaderIsPending(pReader) ){
-      Fts3HashElem *pElem = *(pReader->ppNextElem);
-      if( pElem==0 ){
-        pReader->aNode = 0;
-      }else{
-        PendingList *pList = (PendingList *)fts3HashData(pElem);
-        pReader->zTerm = (char *)fts3HashKey(pElem);
-        pReader->nTerm = fts3HashKeysize(pElem);
-        pReader->nNode = pReader->nDoclist = pList->nData + 1;
-        pReader->aNode = pReader->aDoclist = pList->aData;
-        pReader->ppNextElem++;
-        assert( pReader->aNode );
-      }
-      return SQLITE_OK;
-    }
+/*
+** An object of this type contains the state required to create or append
+** to an appendable b-tree segment.
+*/
+struct IncrmergeWriter {
+  int nLeafEst;                   /* Space allocated for leaf blocks */
+  int nWork;                      /* Number of leaf pages flushed */
+  sqlite3_int64 iAbsLevel;        /* Absolute level of input segments */
+  int iIdx;                       /* Index of *output* segment in iAbsLevel+1 */
+  sqlite3_int64 iStart;           /* Block number of first allocated block */
+  sqlite3_int64 iEnd;             /* Block number of last allocated block */
+  sqlite3_int64 nLeafData;        /* Bytes of leaf page data so far */
+  u8 bNoLeafData;                 /* If true, store 0 for segment size */
+  NodeWriter aNodeWriter[FTS_MAX_APPENDABLE_HEIGHT];
+};
 
-    fts3SegReaderSetEof(pReader);
+/*
+** An object of the following type is used to read data from a single
+** FTS segment node. See the following functions:
+**
+**     nodeReaderInit()
+**     nodeReaderNext()
+**     nodeReaderRelease()
+*/
+struct NodeReader {
+  const char *aNode;
+  int nNode;
+  int iOff;                       /* Current offset within aNode[] */
 
-    /* If iCurrentBlock>=iLeafEndBlock, this is an EOF condition. All leaf 
-    ** blocks have already been traversed.  */
-    assert( pReader->iCurrentBlock<=pReader->iLeafEndBlock );
-    if( pReader->iCurrentBlock>=pReader->iLeafEndBlock ){
-      return SQLITE_OK;
-    }
+  /* Output variables. Containing the current node entry. */
+  sqlite3_int64 iChild;           /* Pointer to child node */
+  Blob term;                      /* Current term */
+  const char *aDoclist;           /* Pointer to doclist */
+  int nDoclist;                   /* Size of doclist in bytes */
+};
 
-    rc = sqlite3Fts3ReadBlock(
-        p, ++pReader->iCurrentBlock, &pReader->aNode, &pReader->nNode, 
-        (bIncr ? &pReader->nPopulate : 0)
-    );
-    if( rc!=SQLITE_OK ) return rc;
-    assert( pReader->pBlob==0 );
-    if( bIncr && pReader->nPopulate<pReader->nNode ){
-      pReader->pBlob = p->pSegments;
-      p->pSegments = 0;
+/*
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, if the allocation at pBlob->a is not already at least nMin
+** bytes in size, extend (realloc) it to be so.
+**
+** If an OOM error occurs, set *pRc to SQLITE_NOMEM and leave pBlob->a
+** unmodified. Otherwise, if the allocation succeeds, update pBlob->nAlloc
+** to reflect the new size of the pBlob->a[] buffer.
+*/
+static void blobGrowBuffer(Blob *pBlob, int nMin, int *pRc){
+  if( *pRc==SQLITE_OK && nMin>pBlob->nAlloc ){
+    int nAlloc = nMin;
+    char *a = (char *)sqlite3_realloc(pBlob->a, nAlloc);
+    if( a ){
+      pBlob->nAlloc = nAlloc;
+      pBlob->a = a;
+    }else{
+      *pRc = SQLITE_NOMEM;
     }
-    pNext = pReader->aNode;
   }
+}
 
-  assert( !fts3SegReaderIsPending(pReader) );
+/*
+** Attempt to advance the node-reader object passed as the first argument to
+** the next entry on the node. 
+**
+** Return an error code if an error occurs (SQLITE_NOMEM is possible). 
+** Otherwise return SQLITE_OK. If there is no next entry on the node
+** (e.g. because the current entry is the last) set NodeReader->aNode to
+** NULL to indicate EOF. Otherwise, populate the NodeReader structure output 
+** variables for the new entry.
+*/
+static int nodeReaderNext(NodeReader *p){
+  int bFirst = (p->term.n==0);    /* True for first term on the node */
+  int nPrefix = 0;                /* Bytes to copy from previous term */
+  int nSuffix = 0;                /* Bytes to append to the prefix */
+  int rc = SQLITE_OK;             /* Return code */
 
-  rc = fts3SegReaderRequire(pReader, pNext, FTS3_VARINT_MAX*2);
-  if( rc!=SQLITE_OK ) return rc;
-  
-  /* Because of the FTS3_NODE_PADDING bytes of padding, the following is 
-  ** safe (no risk of overread) even if the node data is corrupted. */
-  pNext += fts3GetVarint32(pNext, &nPrefix);
-  pNext += fts3GetVarint32(pNext, &nSuffix);
-  if( nPrefix<0 || nSuffix<=0 
-   || &pNext[nSuffix]>&pReader->aNode[pReader->nNode] 
-  ){
-    return FTS_CORRUPT_VTAB;
-  }
+  assert( p->aNode );
+  if( p->iChild && bFirst==0 ) p->iChild++;
+  if( p->iOff>=p->nNode ){
+    /* EOF */
+    p->aNode = 0;
+  }else{
+    if( bFirst==0 ){
+      p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nPrefix);
+    }
+    p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nSuffix);
 
-  if( nPrefix+nSuffix>pReader->nTermAlloc ){
-    int nNew = (nPrefix+nSuffix)*2;
-    char *zNew = sqlite3_realloc(pReader->zTerm, nNew);
-    if( !zNew ){
-      return SQLITE_NOMEM;
+    blobGrowBuffer(&p->term, nPrefix+nSuffix, &rc);
+    if( rc==SQLITE_OK ){
+      memcpy(&p->term.a[nPrefix], &p->aNode[p->iOff], nSuffix);
+      p->term.n = nPrefix+nSuffix;
+      p->iOff += nSuffix;
+      if( p->iChild==0 ){
+        p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &p->nDoclist);
+        p->aDoclist = &p->aNode[p->iOff];
+        p->iOff += p->nDoclist;
+      }
     }
-    pReader->zTerm = zNew;
-    pReader->nTermAlloc = nNew;
   }
 
-  rc = fts3SegReaderRequire(pReader, pNext, nSuffix+FTS3_VARINT_MAX);
-  if( rc!=SQLITE_OK ) return rc;
+  assert( p->iOff<=p->nNode );
 
-  memcpy(&pReader->zTerm[nPrefix], pNext, nSuffix);
-  pReader->nTerm = nPrefix+nSuffix;
-  pNext += nSuffix;
-  pNext += fts3GetVarint32(pNext, &pReader->nDoclist);
-  pReader->aDoclist = pNext;
-  pReader->pOffsetList = 0;
+  return rc;
+}
 
-  /* Check that the doclist does not appear to extend past the end of the
-  ** b-tree node. And that the final byte of the doclist is 0x00. If either 
-  ** of these statements is untrue, then the data structure is corrupt.
-  */
-  if( &pReader->aDoclist[pReader->nDoclist]>&pReader->aNode[pReader->nNode] 
-   || (pReader->nPopulate==0 && pReader->aDoclist[pReader->nDoclist-1])
-  ){
-    return FTS_CORRUPT_VTAB;
-  }
-  return SQLITE_OK;
+/*
+** Release all dynamic resources held by node-reader object *p.
+*/
+static void nodeReaderRelease(NodeReader *p){
+  sqlite3_free(p->term.a);
 }
 
 /*
-** Set the SegReader to point to the first docid in the doclist associated
-** with the current term.
+** Initialize a node-reader object to read the node in buffer aNode/nNode.
+**
+** If successful, SQLITE_OK is returned and the NodeReader object set to 
+** point to the first entry on the node (if any). Otherwise, an SQLite
+** error code is returned.
 */
-static int fts3SegReaderFirstDocid(Fts3Table *pTab, Fts3SegReader *pReader){
-  int rc = SQLITE_OK;
-  assert( pReader->aDoclist );
-  assert( !pReader->pOffsetList );
-  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
-    u8 bEof = 0;
-    pReader->iDocid = 0;
-    pReader->nOffsetList = 0;
-    sqlite3Fts3DoclistPrev(0,
-        pReader->aDoclist, pReader->nDoclist, &pReader->pOffsetList, 
-        &pReader->iDocid, &pReader->nOffsetList, &bEof
-    );
+static int nodeReaderInit(NodeReader *p, const char *aNode, int nNode){
+  memset(p, 0, sizeof(NodeReader));
+  p->aNode = aNode;
+  p->nNode = nNode;
+
+  /* Figure out if this is a leaf or an internal node. */
+  if( p->aNode[0] ){
+    /* An internal node. */
+    p->iOff = 1 + sqlite3Fts3GetVarint(&p->aNode[1], &p->iChild);
   }else{
-    rc = fts3SegReaderRequire(pReader, pReader->aDoclist, FTS3_VARINT_MAX);
-    if( rc==SQLITE_OK ){
-      int n = sqlite3Fts3GetVarint(pReader->aDoclist, &pReader->iDocid);
-      pReader->pOffsetList = &pReader->aDoclist[n];
-    }
+    p->iOff = 1;
   }
-  return rc;
+
+  return nodeReaderNext(p);
 }
 
 /*
-** Advance the SegReader to point to the next docid in the doclist
-** associated with the current term.
-** 
-** If arguments ppOffsetList and pnOffsetList are not NULL, then 
-** *ppOffsetList is set to point to the first column-offset list
-** in the doclist entry (i.e. immediately past the docid varint).
-** *pnOffsetList is set to the length of the set of column-offset
-** lists, not including the nul-terminator byte. For example:
+** This function is called while writing an FTS segment each time a leaf o
+** node is finished and written to disk. The key (zTerm/nTerm) is guaranteed
+** to be greater than the largest key on the node just written, but smaller
+** than or equal to the first key that will be written to the next leaf
+** node.
+**
+** The block id of the leaf node just written to disk may be found in
+** (pWriter->aNodeWriter[0].iBlock) when this function is called.
 */
-static int fts3SegReaderNextDocid(
-  Fts3Table *pTab,
-  Fts3SegReader *pReader,         /* Reader to advance to next docid */
-  char **ppOffsetList,            /* OUT: Pointer to current position-list */
-  int *pnOffsetList               /* OUT: Length of *ppOffsetList in bytes */
+static int fts3IncrmergePush(
+  Fts3Table *p,                   /* Fts3 table handle */
+  IncrmergeWriter *pWriter,       /* Writer object */
+  const char *zTerm,              /* Term to write to internal node */
+  int nTerm                       /* Bytes at zTerm */
 ){
-  int rc = SQLITE_OK;
-  char *p = pReader->pOffsetList;
-  char c = 0;
+  sqlite3_int64 iPtr = pWriter->aNodeWriter[0].iBlock;
+  int iLayer;
 
-  assert( p );
+  assert( nTerm>0 );
+  for(iLayer=1; ALWAYS(iLayer<FTS_MAX_APPENDABLE_HEIGHT); iLayer++){
+    sqlite3_int64 iNextPtr = 0;
+    NodeWriter *pNode = &pWriter->aNodeWriter[iLayer];
+    int rc = SQLITE_OK;
+    int nPrefix;
+    int nSuffix;
+    int nSpace;
 
-  if( pTab->bDescIdx && fts3SegReaderIsPending(pReader) ){
-    /* A pending-terms seg-reader for an FTS4 table that uses order=desc.
-    ** Pending-terms doclists are always built up in ascending order, so
-    ** we have to iterate through them backwards here. */
-    u8 bEof = 0;
-    if( ppOffsetList ){
-      *ppOffsetList = pReader->pOffsetList;
-      *pnOffsetList = pReader->nOffsetList - 1;
-    }
-    sqlite3Fts3DoclistPrev(0,
-        pReader->aDoclist, pReader->nDoclist, &p, &pReader->iDocid,
-        &pReader->nOffsetList, &bEof
-    );
-    if( bEof ){
-      pReader->pOffsetList = 0;
-    }else{
-      pReader->pOffsetList = p;
-    }
-  }else{
-    char *pEnd = &pReader->aDoclist[pReader->nDoclist];
+    /* Figure out how much space the key will consume if it is written to
+    ** the current node of layer iLayer. Due to the prefix compression, 
+    ** the space required changes depending on which node the key is to
+    ** be added to.  */
+    nPrefix = fts3PrefixCompress(pNode->key.a, pNode->key.n, zTerm, nTerm);
+    nSuffix = nTerm - nPrefix;
+    nSpace  = sqlite3Fts3VarintLen(nPrefix);
+    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
 
-    /* Pointer p currently points at the first byte of an offset list. The
-    ** following block advances it to point one byte past the end of
-    ** the same offset list. */
-    while( 1 ){
-  
-      /* The following line of code (and the "p++" below the while() loop) is
-      ** normally all that is required to move pointer p to the desired 
-      ** position. The exception is if this node is being loaded from disk
-      ** incrementally and pointer "p" now points to the first byte past
-      ** the populated part of pReader->aNode[].
-      */
-      while( *p | c ) c = *p++ & 0x80;
-      assert( *p==0 );
-  
-      if( pReader->pBlob==0 || p<&pReader->aNode[pReader->nPopulate] ) break;
-      rc = fts3SegReaderIncrRead(pReader);
-      if( rc!=SQLITE_OK ) return rc;
-    }
-    p++;
-  
-    /* If required, populate the output variables with a pointer to and the
-    ** size of the previous offset-list.
-    */
-    if( ppOffsetList ){
-      *ppOffsetList = pReader->pOffsetList;
-      *pnOffsetList = (int)(p - pReader->pOffsetList - 1);
-    }
+    if( pNode->key.n==0 || (pNode->block.n + nSpace)<=p->nNodeSize ){ 
+      /* If the current node of layer iLayer contains zero keys, or if adding
+      ** the key to it will not cause it to grow to larger than nNodeSize 
+      ** bytes in size, write the key here.  */
 
-    /* List may have been edited in place by fts3EvalNearTrim() */
-    while( p<pEnd && *p==0 ) p++;
-  
-    /* If there are no more entries in the doclist, set pOffsetList to
-    ** NULL. Otherwise, set Fts3SegReader.iDocid to the next docid and
-    ** Fts3SegReader.pOffsetList to point to the next offset list before
-    ** returning.
-    */
-    if( p>=pEnd ){
-      pReader->pOffsetList = 0;
-    }else{
-      rc = fts3SegReaderRequire(pReader, p, FTS3_VARINT_MAX);
-      if( rc==SQLITE_OK ){
-        sqlite3_int64 iDelta;
-        pReader->pOffsetList = p + sqlite3Fts3GetVarint(p, &iDelta);
-        if( pTab->bDescIdx ){
-          pReader->iDocid -= iDelta;
-        }else{
-          pReader->iDocid += iDelta;
+      Blob *pBlk = &pNode->block;
+      if( pBlk->n==0 ){
+        blobGrowBuffer(pBlk, p->nNodeSize, &rc);
+        if( rc==SQLITE_OK ){
+          pBlk->a[0] = (char)iLayer;
+          pBlk->n = 1 + sqlite3Fts3PutVarint(&pBlk->a[1], iPtr);
         }
       }
-    }
-  }
-
-  return SQLITE_OK;
-}
+      blobGrowBuffer(pBlk, pBlk->n + nSpace, &rc);
+      blobGrowBuffer(&pNode->key, nTerm, &rc);
 
+      if( rc==SQLITE_OK ){
+        if( pNode->key.n ){
+          pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nPrefix);
+        }
+        pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nSuffix);
+        memcpy(&pBlk->a[pBlk->n], &zTerm[nPrefix], nSuffix);
+        pBlk->n += nSuffix;
 
-SQLITE_PRIVATE int sqlite3Fts3MsrOvfl(
-  Fts3Cursor *pCsr, 
-  Fts3MultiSegReader *pMsr,
-  int *pnOvfl
-){
-  Fts3Table *p = (Fts3Table*)pCsr->base.pVtab;
-  int nOvfl = 0;
-  int ii;
-  int rc = SQLITE_OK;
-  int pgsz = p->nPgsz;
+        memcpy(pNode->key.a, zTerm, nTerm);
+        pNode->key.n = nTerm;
+      }
+    }else{
+      /* Otherwise, flush the current node of layer iLayer to disk.
+      ** Then allocate a new, empty sibling node. The key will be written
+      ** into the parent of this node. */
+      rc = fts3WriteSegment(p, pNode->iBlock, pNode->block.a, pNode->block.n);
 
-  assert( p->bFts4 );
-  assert( pgsz>0 );
+      assert( pNode->block.nAlloc>=p->nNodeSize );
+      pNode->block.a[0] = (char)iLayer;
+      pNode->block.n = 1 + sqlite3Fts3PutVarint(&pNode->block.a[1], iPtr+1);
 
-  for(ii=0; rc==SQLITE_OK && ii<pMsr->nSegment; ii++){
-    Fts3SegReader *pReader = pMsr->apSegment[ii];
-    if( !fts3SegReaderIsPending(pReader) 
-     && !fts3SegReaderIsRootOnly(pReader) 
-    ){
-      sqlite3_int64 jj;
-      for(jj=pReader->iStartBlock; jj<=pReader->iLeafEndBlock; jj++){
-        int nBlob;
-        rc = sqlite3Fts3ReadBlock(p, jj, 0, &nBlob, 0);
-        if( rc!=SQLITE_OK ) break;
-        if( (nBlob+35)>pgsz ){
-          nOvfl += (nBlob + 34)/pgsz;
-        }
-      }
+      iNextPtr = pNode->iBlock;
+      pNode->iBlock++;
+      pNode->key.n = 0;
     }
-  }
-  *pnOvfl = nOvfl;
-  return rc;
-}
 
-/*
-** Free all allocations associated with the iterator passed as the 
-** second argument.
-*/
-SQLITE_PRIVATE void sqlite3Fts3SegReaderFree(Fts3SegReader *pReader){
-  if( pReader && !fts3SegReaderIsPending(pReader) ){
-    sqlite3_free(pReader->zTerm);
-    if( !fts3SegReaderIsRootOnly(pReader) ){
-      sqlite3_free(pReader->aNode);
-      sqlite3_blob_close(pReader->pBlob);
-    }
+    if( rc!=SQLITE_OK || iNextPtr==0 ) return rc;
+    iPtr = iNextPtr;
   }
-  sqlite3_free(pReader);
+
+  assert( 0 );
+  return 0;
 }
 
 /*
-** Allocate a new SegReader object.
+** Append a term and (optionally) doclist to the FTS segment node currently
+** stored in blob *pNode. The node need not contain any terms, but the
+** header must be written before this function is called.
+**
+** A node header is a single 0x00 byte for a leaf node, or a height varint
+** followed by the left-hand-child varint for an internal node.
+**
+** The term to be appended is passed via arguments zTerm/nTerm. For a 
+** leaf node, the doclist is passed as aDoclist/nDoclist. For an internal
+** node, both aDoclist and nDoclist must be passed 0.
+**
+** If the size of the value in blob pPrev is zero, then this is the first
+** term written to the node. Otherwise, pPrev contains a copy of the 
+** previous term. Before this function returns, it is updated to contain a
+** copy of zTerm/nTerm.
+**
+** It is assumed that the buffer associated with pNode is already large
+** enough to accommodate the new entry. The buffer associated with pPrev
+** is extended by this function if requrired.
+**
+** If an error (i.e. OOM condition) occurs, an SQLite error code is
+** returned. Otherwise, SQLITE_OK.
 */
-SQLITE_PRIVATE int sqlite3Fts3SegReaderNew(
-  int iAge,                       /* Segment "age". */
-  int bLookup,                    /* True for a lookup only */
-  sqlite3_int64 iStartLeaf,       /* First leaf to traverse */
-  sqlite3_int64 iEndLeaf,         /* Final leaf to traverse */
-  sqlite3_int64 iEndBlock,        /* Final block of segment */
-  const char *zRoot,              /* Buffer containing root node */
-  int nRoot,                      /* Size of buffer containing root node */
-  Fts3SegReader **ppReader        /* OUT: Allocated Fts3SegReader */
+static int fts3AppendToNode(
+  Blob *pNode,                    /* Current node image to append to */
+  Blob *pPrev,                    /* Buffer containing previous term written */
+  const char *zTerm,              /* New term to write */
+  int nTerm,                      /* Size of zTerm in bytes */
+  const char *aDoclist,           /* Doclist (or NULL) to write */
+  int nDoclist                    /* Size of aDoclist in bytes */ 
 ){
-  Fts3SegReader *pReader;         /* Newly allocated SegReader object */
-  int nExtra = 0;                 /* Bytes to allocate segment root node */
+  int rc = SQLITE_OK;             /* Return code */
+  int bFirst = (pPrev->n==0);     /* True if this is the first term written */
+  int nPrefix;                    /* Size of term prefix in bytes */
+  int nSuffix;                    /* Size of term suffix in bytes */
 
-  assert( iStartLeaf<=iEndLeaf );
-  if( iStartLeaf==0 ){
-    nExtra = nRoot + FTS3_NODE_PADDING;
-  }
+  /* Node must have already been started. There must be a doclist for a
+  ** leaf node, and there must not be a doclist for an internal node.  */
+  assert( pNode->n>0 );
+  assert( (pNode->a[0]=='\0')==(aDoclist!=0) );
 
-  pReader = (Fts3SegReader *)sqlite3_malloc(sizeof(Fts3SegReader) + nExtra);
-  if( !pReader ){
-    return SQLITE_NOMEM;
+  blobGrowBuffer(pPrev, nTerm, &rc);
+  if( rc!=SQLITE_OK ) return rc;
+
+  nPrefix = fts3PrefixCompress(pPrev->a, pPrev->n, zTerm, nTerm);
+  nSuffix = nTerm - nPrefix;
+  memcpy(pPrev->a, zTerm, nTerm);
+  pPrev->n = nTerm;
+
+  if( bFirst==0 ){
+    pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nPrefix);
   }
-  memset(pReader, 0, sizeof(Fts3SegReader));
-  pReader->iIdx = iAge;
-  pReader->bLookup = bLookup!=0;
-  pReader->iStartBlock = iStartLeaf;
-  pReader->iLeafEndBlock = iEndLeaf;
-  pReader->iEndBlock = iEndBlock;
+  pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nSuffix);
+  memcpy(&pNode->a[pNode->n], &zTerm[nPrefix], nSuffix);
+  pNode->n += nSuffix;
 
-  if( nExtra ){
-    /* The entire segment is stored in the root node. */
-    pReader->aNode = (char *)&pReader[1];
-    pReader->rootOnly = 1;
-    pReader->nNode = nRoot;
-    memcpy(pReader->aNode, zRoot, nRoot);
-    memset(&pReader->aNode[nRoot], 0, FTS3_NODE_PADDING);
-  }else{
-    pReader->iCurrentBlock = iStartLeaf-1;
+  if( aDoclist ){
+    pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nDoclist);
+    memcpy(&pNode->a[pNode->n], aDoclist, nDoclist);
+    pNode->n += nDoclist;
   }
-  *ppReader = pReader;
+
+  assert( pNode->n<=pNode->nAlloc );
+
   return SQLITE_OK;
 }
 
 /*
-** This is a comparison function used as a qsort() callback when sorting
-** an array of pending terms by term. This occurs as part of flushing
-** the contents of the pending-terms hash table to the database.
+** Append the current term and doclist pointed to by cursor pCsr to the
+** appendable b-tree segment opened for writing by pWriter.
+**
+** Return SQLITE_OK if successful, or an SQLite error code otherwise.
 */
-static int SQLITE_CDECL fts3CompareElemByTerm(
-  const void *lhs,
-  const void *rhs
+static int fts3IncrmergeAppend(
+  Fts3Table *p,                   /* Fts3 table handle */
+  IncrmergeWriter *pWriter,       /* Writer object */
+  Fts3MultiSegReader *pCsr        /* Cursor containing term and doclist */
 ){
-  char *z1 = fts3HashKey(*(Fts3HashElem **)lhs);
-  char *z2 = fts3HashKey(*(Fts3HashElem **)rhs);
-  int n1 = fts3HashKeysize(*(Fts3HashElem **)lhs);
-  int n2 = fts3HashKeysize(*(Fts3HashElem **)rhs);
+  const char *zTerm = pCsr->zTerm;
+  int nTerm = pCsr->nTerm;
+  const char *aDoclist = pCsr->aDoclist;
+  int nDoclist = pCsr->nDoclist;
+  int rc = SQLITE_OK;           /* Return code */
+  int nSpace;                   /* Total space in bytes required on leaf */
+  int nPrefix;                  /* Size of prefix shared with previous term */
+  int nSuffix;                  /* Size of suffix (nTerm - nPrefix) */
+  NodeWriter *pLeaf;            /* Object used to write leaf nodes */
 
-  int n = (n1<n2 ? n1 : n2);
-  int c = memcmp(z1, z2, n);
-  if( c==0 ){
-    c = n1 - n2;
+  pLeaf = &pWriter->aNodeWriter[0];
+  nPrefix = fts3PrefixCompress(pLeaf->key.a, pLeaf->key.n, zTerm, nTerm);
+  nSuffix = nTerm - nPrefix;
+
+  nSpace  = sqlite3Fts3VarintLen(nPrefix);
+  nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
+  nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
+
+  /* If the current block is not empty, and if adding this term/doclist
+  ** to the current block would make it larger than Fts3Table.nNodeSize
+  ** bytes, write this block out to the database. */
+  if( pLeaf->block.n>0 && (pLeaf->block.n + nSpace)>p->nNodeSize ){
+    rc = fts3WriteSegment(p, pLeaf->iBlock, pLeaf->block.a, pLeaf->block.n);
+    pWriter->nWork++;
+
+    /* Add the current term to the parent node. The term added to the 
+    ** parent must:
+    **
+    **   a) be greater than the largest term on the leaf node just written
+    **      to the database (still available in pLeaf->key), and
+    **
+    **   b) be less than or equal to the term about to be added to the new
+    **      leaf node (zTerm/nTerm).
+    **
+    ** In other words, it must be the prefix of zTerm 1 byte longer than
+    ** the common prefix (if any) of zTerm and pWriter->zTerm.
+    */
+    if( rc==SQLITE_OK ){
+      rc = fts3IncrmergePush(p, pWriter, zTerm, nPrefix+1);
+    }
+
+    /* Advance to the next output block */
+    pLeaf->iBlock++;
+    pLeaf->key.n = 0;
+    pLeaf->block.n = 0;
+
+    nSuffix = nTerm;
+    nSpace  = 1;
+    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
+    nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
   }
-  return c;
+
+  pWriter->nLeafData += nSpace;
+  blobGrowBuffer(&pLeaf->block, pLeaf->block.n + nSpace, &rc);
+  if( rc==SQLITE_OK ){
+    if( pLeaf->block.n==0 ){
+      pLeaf->block.n = 1;
+      pLeaf->block.a[0] = '\0';
+    }
+    rc = fts3AppendToNode(
+        &pLeaf->block, &pLeaf->key, zTerm, nTerm, aDoclist, nDoclist
+    );
+  }
+
+  return rc;
 }
 
 /*
-** This function is used to allocate an Fts3SegReader that iterates through
-** a subset of the terms stored in the Fts3Table.pendingTerms array.
-**
-** If the isPrefixIter parameter is zero, then the returned SegReader iterates
-** through each term in the pending-terms table. Or, if isPrefixIter is
-** non-zero, it iterates through each term and its prefixes. For example, if
-** the pending terms hash table contains the terms "sqlite", "mysql" and
-** "firebird", then the iterator visits the following 'terms' (in the order
-** shown):
-**
-**   f fi fir fire fireb firebi firebir firebird
-**   m my mys mysq mysql
-**   s sq sql sqli sqlit sqlite
+** This function is called to release all dynamic resources held by the
+** merge-writer object pWriter, and if no error has occurred, to flush
+** all outstanding node buffers held by pWriter to disk.
 **
-** Whereas if isPrefixIter is zero, the terms visited are:
+** If *pRc is not SQLITE_OK when this function is called, then no attempt
+** is made to write any data to disk. Instead, this function serves only
+** to release outstanding resources.
 **
-**   firebird mysql sqlite
+** Otherwise, if *pRc is initially SQLITE_OK and an error occurs while
+** flushing buffers to disk, *pRc is set to an SQLite error code before
+** returning.
 */
-SQLITE_PRIVATE int sqlite3Fts3SegReaderPending(
-  Fts3Table *p,                   /* Virtual table handle */
-  int iIndex,                     /* Index for p->aIndex */
-  const char *zTerm,              /* Term to search for */
-  int nTerm,                      /* Size of buffer zTerm */
-  int bPrefix,                    /* True for a prefix iterator */
-  Fts3SegReader **ppReader        /* OUT: SegReader for pending-terms */
+static void fts3IncrmergeRelease(
+  Fts3Table *p,                   /* FTS3 table handle */
+  IncrmergeWriter *pWriter,       /* Merge-writer object */
+  int *pRc                        /* IN/OUT: Error code */
 ){
-  Fts3SegReader *pReader = 0;     /* Fts3SegReader object to return */
-  Fts3HashElem *pE;               /* Iterator variable */
-  Fts3HashElem **aElem = 0;       /* Array of term hash entries to scan */
-  int nElem = 0;                  /* Size of array at aElem */
-  int rc = SQLITE_OK;             /* Return Code */
-  Fts3Hash *pHash;
-
-  pHash = &p->aIndex[iIndex].hPending;
-  if( bPrefix ){
-    int nAlloc = 0;               /* Size of allocated array at aElem */
-
-    for(pE=fts3HashFirst(pHash); pE; pE=fts3HashNext(pE)){
-      char *zKey = (char *)fts3HashKey(pE);
-      int nKey = fts3HashKeysize(pE);
-      if( nTerm==0 || (nKey>=nTerm && 0==memcmp(zKey, zTerm, nTerm)) ){
-        if( nElem==nAlloc ){
-          Fts3HashElem **aElem2;
-          nAlloc += 16;
-          aElem2 = (Fts3HashElem **)sqlite3_realloc(
-              aElem, nAlloc*sizeof(Fts3HashElem *)
-          );
-          if( !aElem2 ){
-            rc = SQLITE_NOMEM;
-            nElem = 0;
-            break;
-          }
-          aElem = aElem2;
-        }
+  int i;                          /* Used to iterate through non-root layers */
+  int iRoot;                      /* Index of root in pWriter->aNodeWriter */
+  NodeWriter *pRoot;              /* NodeWriter for root node */
+  int rc = *pRc;                  /* Error code */
 
-        aElem[nElem++] = pE;
-      }
-    }
+  /* Set iRoot to the index in pWriter->aNodeWriter[] of the output segment 
+  ** root node. If the segment fits entirely on a single leaf node, iRoot
+  ** will be set to 0. If the root node is the parent of the leaves, iRoot
+  ** will be 1. And so on.  */
+  for(iRoot=FTS_MAX_APPENDABLE_HEIGHT-1; iRoot>=0; iRoot--){
+    NodeWriter *pNode = &pWriter->aNodeWriter[iRoot];
+    if( pNode->block.n>0 ) break;
+    assert( *pRc || pNode->block.nAlloc==0 );
+    assert( *pRc || pNode->key.nAlloc==0 );
+    sqlite3_free(pNode->block.a);
+    sqlite3_free(pNode->key.a);
+  }
 
-    /* If more than one term matches the prefix, sort the Fts3HashElem
-    ** objects in term order using qsort(). This uses the same comparison
-    ** callback as is used when flushing terms to disk.
-    */
-    if( nElem>1 ){
-      qsort(aElem, nElem, sizeof(Fts3HashElem *), fts3CompareElemByTerm);
-    }
+  /* Empty output segment. This is a no-op. */
+  if( iRoot<0 ) return;
 
-  }else{
-    /* The query is a simple term lookup that matches at most one term in
-    ** the index. All that is required is a straight hash-lookup. 
-    **
-    ** Because the stack address of pE may be accessed via the aElem pointer
-    ** below, the "Fts3HashElem *pE" must be declared so that it is valid
-    ** within this entire function, not just this "else{...}" block.
-    */
-    pE = fts3HashFindElem(pHash, zTerm, nTerm);
-    if( pE ){
-      aElem = &pE;
-      nElem = 1;
+  /* The entire output segment fits on a single node. Normally, this means
+  ** the node would be stored as a blob in the "root" column of the %_segdir
+  ** table. However, this is not permitted in this case. The problem is that 
+  ** space has already been reserved in the %_segments table, and so the 
+  ** start_block and end_block fields of the %_segdir table must be populated. 
+  ** And, by design or by accident, released versions of FTS cannot handle 
+  ** segments that fit entirely on the root node with start_block!=0.
+  **
+  ** Instead, create a synthetic root node that contains nothing but a 
+  ** pointer to the single content node. So that the segment consists of a
+  ** single leaf and a single interior (root) node.
+  **
+  ** Todo: Better might be to defer allocating space in the %_segments 
+  ** table until we are sure it is needed.
+  */
+  if( iRoot==0 ){
+    Blob *pBlock = &pWriter->aNodeWriter[1].block;
+    blobGrowBuffer(pBlock, 1 + FTS3_VARINT_MAX, &rc);
+    if( rc==SQLITE_OK ){
+      pBlock->a[0] = 0x01;
+      pBlock->n = 1 + sqlite3Fts3PutVarint(
+          &pBlock->a[1], pWriter->aNodeWriter[0].iBlock
+      );
     }
+    iRoot = 1;
   }
+  pRoot = &pWriter->aNodeWriter[iRoot];
 
-  if( nElem>0 ){
-    int nByte = sizeof(Fts3SegReader) + (nElem+1)*sizeof(Fts3HashElem *);
-    pReader = (Fts3SegReader *)sqlite3_malloc(nByte);
-    if( !pReader ){
-      rc = SQLITE_NOMEM;
-    }else{
-      memset(pReader, 0, nByte);
-      pReader->iIdx = 0x7FFFFFFF;
-      pReader->ppNextElem = (Fts3HashElem **)&pReader[1];
-      memcpy(pReader->ppNextElem, aElem, nElem*sizeof(Fts3HashElem *));
+  /* Flush all currently outstanding nodes to disk. */
+  for(i=0; i<iRoot; i++){
+    NodeWriter *pNode = &pWriter->aNodeWriter[i];
+    if( pNode->block.n>0 && rc==SQLITE_OK ){
+      rc = fts3WriteSegment(p, pNode->iBlock, pNode->block.a, pNode->block.n);
     }
+    sqlite3_free(pNode->block.a);
+    sqlite3_free(pNode->key.a);
   }
 
-  if( bPrefix ){
-    sqlite3_free(aElem);
+  /* Write the %_segdir record. */
+  if( rc==SQLITE_OK ){
+    rc = fts3WriteSegdir(p, 
+        pWriter->iAbsLevel+1,               /* level */
+        pWriter->iIdx,                      /* idx */
+        pWriter->iStart,                    /* start_block */
+        pWriter->aNodeWriter[0].iBlock,     /* leaves_end_block */
+        pWriter->iEnd,                      /* end_block */
+        (pWriter->bNoLeafData==0 ? pWriter->nLeafData : 0),   /* end_block */
+        pRoot->block.a, pRoot->block.n      /* root */
+    );
   }
-  *ppReader = pReader;
-  return rc;
+  sqlite3_free(pRoot->block.a);
+  sqlite3_free(pRoot->key.a);
+
+  *pRc = rc;
 }
 
 /*
-** Compare the entries pointed to by two Fts3SegReader structures. 
-** Comparison is as follows:
-**
-**   1) EOF is greater than not EOF.
-**
-**   2) The current terms (if any) are compared using memcmp(). If one
-**      term is a prefix of another, the longer term is considered the
-**      larger.
+** Compare the term in buffer zLhs (size in bytes nLhs) with that in
+** zRhs (size in bytes nRhs) using memcmp. If one term is a prefix of
+** the other, it is considered to be smaller than the other.
 **
-**   3) By segment age. An older segment is considered larger.
+** Return -ve if zLhs is smaller than zRhs, 0 if it is equal, or +ve
+** if it is greater.
 */
-static int fts3SegReaderCmp(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
-  int rc;
-  if( pLhs->aNode && pRhs->aNode ){
-    int rc2 = pLhs->nTerm - pRhs->nTerm;
-    if( rc2<0 ){
-      rc = memcmp(pLhs->zTerm, pRhs->zTerm, pLhs->nTerm);
-    }else{
-      rc = memcmp(pLhs->zTerm, pRhs->zTerm, pRhs->nTerm);
-    }
-    if( rc==0 ){
-      rc = rc2;
-    }
-  }else{
-    rc = (pLhs->aNode==0) - (pRhs->aNode==0);
-  }
-  if( rc==0 ){
-    rc = pRhs->iIdx - pLhs->iIdx;
-  }
-  assert( rc!=0 );
-  return rc;
+static int fts3TermCmp(
+  const char *zLhs, int nLhs,     /* LHS of comparison */
+  const char *zRhs, int nRhs      /* RHS of comparison */
+){
+  int nCmp = MIN(nLhs, nRhs);
+  int res;
+
+  res = memcmp(zLhs, zRhs, nCmp);
+  if( res==0 ) res = nLhs - nRhs;
+
+  return res;
 }
 
+
 /*
-** A different comparison function for SegReader structures. In this
-** version, it is assumed that each SegReader points to an entry in
-** a doclist for identical terms. Comparison is made as follows:
-**
-**   1) EOF (end of doclist in this case) is greater than not EOF.
+** Query to see if the entry in the %_segments table with blockid iEnd is 
+** NULL. If no error occurs and the entry is NULL, set *pbRes 1 before
+** returning. Otherwise, set *pbRes to 0. 
 **
-**   2) By current docid.
+** Or, if an error occurs while querying the database, return an SQLite 
+** error code. The final value of *pbRes is undefined in this case.
 **
-**   3) By segment age. An older segment is considered larger.
+** This is used to test if a segment is an "appendable" segment. If it
+** is, then a NULL entry has been inserted into the %_segments table
+** with blockid %_segdir.end_block.
 */
-static int fts3SegReaderDoclistCmp(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
-  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
-  if( rc==0 ){
-    if( pLhs->iDocid==pRhs->iDocid ){
-      rc = pRhs->iIdx - pLhs->iIdx;
-    }else{
-      rc = (pLhs->iDocid > pRhs->iDocid) ? 1 : -1;
-    }
-  }
-  assert( pLhs->aNode && pRhs->aNode );
-  return rc;
-}
-static int fts3SegReaderDoclistCmpRev(Fts3SegReader *pLhs, Fts3SegReader *pRhs){
-  int rc = (pLhs->pOffsetList==0)-(pRhs->pOffsetList==0);
-  if( rc==0 ){
-    if( pLhs->iDocid==pRhs->iDocid ){
-      rc = pRhs->iIdx - pLhs->iIdx;
-    }else{
-      rc = (pLhs->iDocid < pRhs->iDocid) ? 1 : -1;
-    }
+static int fts3IsAppendable(Fts3Table *p, sqlite3_int64 iEnd, int *pbRes){
+  int bRes = 0;                   /* Result to set *pbRes to */
+  sqlite3_stmt *pCheck = 0;       /* Statement to query database with */
+  int rc;                         /* Return code */
+
+  rc = fts3SqlStmt(p, SQL_SEGMENT_IS_APPENDABLE, &pCheck, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pCheck, 1, iEnd);
+    if( SQLITE_ROW==sqlite3_step(pCheck) ) bRes = 1;
+    rc = sqlite3_reset(pCheck);
   }
-  assert( pLhs->aNode && pRhs->aNode );
+  
+  *pbRes = bRes;
   return rc;
 }
 
 /*
-** Compare the term that the Fts3SegReader object passed as the first argument
-** points to with the term specified by arguments zTerm and nTerm. 
+** This function is called when initializing an incremental-merge operation.
+** It checks if the existing segment with index value iIdx at absolute level 
+** (iAbsLevel+1) can be appended to by the incremental merge. If it can, the
+** merge-writer object *pWriter is initialized to write to it.
 **
-** If the pSeg iterator is already at EOF, return 0. Otherwise, return
-** -ve if the pSeg term is less than zTerm/nTerm, 0 if the two terms are
-** equal, or +ve if the pSeg term is greater than zTerm/nTerm.
+** An existing segment can be appended to by an incremental merge if:
+**
+**   * It was initially created as an appendable segment (with all required
+**     space pre-allocated), and
+**
+**   * The first key read from the input (arguments zKey and nKey) is 
+**     greater than the largest key currently stored in the potential
+**     output segment.
 */
-static int fts3SegReaderTermCmp(
-  Fts3SegReader *pSeg,            /* Segment reader object */
-  const char *zTerm,              /* Term to compare to */
-  int nTerm                       /* Size of term zTerm in bytes */
+static int fts3IncrmergeLoad(
+  Fts3Table *p,                   /* Fts3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level of input segments */
+  int iIdx,                       /* Index of candidate output segment */
+  const char *zKey,               /* First key to write */
+  int nKey,                       /* Number of bytes in nKey */
+  IncrmergeWriter *pWriter        /* Populate this object */
 ){
-  int res = 0;
-  if( pSeg->aNode ){
-    if( pSeg->nTerm>nTerm ){
-      res = memcmp(pSeg->zTerm, zTerm, nTerm);
+  int rc;                         /* Return code */
+  sqlite3_stmt *pSelect = 0;      /* SELECT to read %_segdir entry */
+
+  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR, &pSelect, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_int64 iStart = 0;     /* Value of %_segdir.start_block */
+    sqlite3_int64 iLeafEnd = 0;   /* Value of %_segdir.leaves_end_block */
+    sqlite3_int64 iEnd = 0;       /* Value of %_segdir.end_block */
+    const char *aRoot = 0;        /* Pointer to %_segdir.root buffer */
+    int nRoot = 0;                /* Size of aRoot[] in bytes */
+    int rc2;                      /* Return code from sqlite3_reset() */
+    int bAppendable = 0;          /* Set to true if segment is appendable */
+
+    /* Read the %_segdir entry for index iIdx absolute level (iAbsLevel+1) */
+    sqlite3_bind_int64(pSelect, 1, iAbsLevel+1);
+    sqlite3_bind_int(pSelect, 2, iIdx);
+    if( sqlite3_step(pSelect)==SQLITE_ROW ){
+      iStart = sqlite3_column_int64(pSelect, 1);
+      iLeafEnd = sqlite3_column_int64(pSelect, 2);
+      fts3ReadEndBlockField(pSelect, 3, &iEnd, &pWriter->nLeafData);
+      if( pWriter->nLeafData<0 ){
+        pWriter->nLeafData = pWriter->nLeafData * -1;
+      }
+      pWriter->bNoLeafData = (pWriter->nLeafData==0);
+      nRoot = sqlite3_column_bytes(pSelect, 4);
+      aRoot = sqlite3_column_blob(pSelect, 4);
     }else{
-      res = memcmp(pSeg->zTerm, zTerm, pSeg->nTerm);
+      return sqlite3_reset(pSelect);
     }
-    if( res==0 ){
-      res = pSeg->nTerm-nTerm;
+
+    /* Check for the zero-length marker in the %_segments table */
+    rc = fts3IsAppendable(p, iEnd, &bAppendable);
+
+    /* Check that zKey/nKey is larger than the largest key the candidate */
+    if( rc==SQLITE_OK && bAppendable ){
+      char *aLeaf = 0;
+      int nLeaf = 0;
+
+      rc = sqlite3Fts3ReadBlock(p, iLeafEnd, &aLeaf, &nLeaf, 0);
+      if( rc==SQLITE_OK ){
+        NodeReader reader;
+        for(rc = nodeReaderInit(&reader, aLeaf, nLeaf);
+            rc==SQLITE_OK && reader.aNode;
+            rc = nodeReaderNext(&reader)
+        ){
+          assert( reader.aNode );
+        }
+        if( fts3TermCmp(zKey, nKey, reader.term.a, reader.term.n)<=0 ){
+          bAppendable = 0;
+        }
+        nodeReaderRelease(&reader);
+      }
+      sqlite3_free(aLeaf);
     }
-  }
-  return res;
-}
 
-/*
-** Argument apSegment is an array of nSegment elements. It is known that
-** the final (nSegment-nSuspect) members are already in sorted order
-** (according to the comparison function provided). This function shuffles
-** the array around until all entries are in sorted order.
-*/
-static void fts3SegReaderSort(
-  Fts3SegReader **apSegment,                     /* Array to sort entries of */
-  int nSegment,                                  /* Size of apSegment array */
-  int nSuspect,                                  /* Unsorted entry count */
-  int (*xCmp)(Fts3SegReader *, Fts3SegReader *)  /* Comparison function */
-){
-  int i;                          /* Iterator variable */
+    if( rc==SQLITE_OK && bAppendable ){
+      /* It is possible to append to this segment. Set up the IncrmergeWriter
+      ** object to do so.  */
+      int i;
+      int nHeight = (int)aRoot[0];
+      NodeWriter *pNode;
 
-  assert( nSuspect<=nSegment );
+      pWriter->nLeafEst = (int)((iEnd - iStart) + 1)/FTS_MAX_APPENDABLE_HEIGHT;
+      pWriter->iStart = iStart;
+      pWriter->iEnd = iEnd;
+      pWriter->iAbsLevel = iAbsLevel;
+      pWriter->iIdx = iIdx;
 
-  if( nSuspect==nSegment ) nSuspect--;
-  for(i=nSuspect-1; i>=0; i--){
-    int j;
-    for(j=i; j<(nSegment-1); j++){
-      Fts3SegReader *pTmp;
-      if( xCmp(apSegment[j], apSegment[j+1])<0 ) break;
-      pTmp = apSegment[j+1];
-      apSegment[j+1] = apSegment[j];
-      apSegment[j] = pTmp;
+      for(i=nHeight+1; i<FTS_MAX_APPENDABLE_HEIGHT; i++){
+        pWriter->aNodeWriter[i].iBlock = pWriter->iStart + i*pWriter->nLeafEst;
+      }
+
+      pNode = &pWriter->aNodeWriter[nHeight];
+      pNode->iBlock = pWriter->iStart + pWriter->nLeafEst*nHeight;
+      blobGrowBuffer(&pNode->block, MAX(nRoot, p->nNodeSize), &rc);
+      if( rc==SQLITE_OK ){
+        memcpy(pNode->block.a, aRoot, nRoot);
+        pNode->block.n = nRoot;
+      }
+
+      for(i=nHeight; i>=0 && rc==SQLITE_OK; i--){
+        NodeReader reader;
+        pNode = &pWriter->aNodeWriter[i];
+
+        rc = nodeReaderInit(&reader, pNode->block.a, pNode->block.n);
+        while( reader.aNode && rc==SQLITE_OK ) rc = nodeReaderNext(&reader);
+        blobGrowBuffer(&pNode->key, reader.term.n, &rc);
+        if( rc==SQLITE_OK ){
+          memcpy(pNode->key.a, reader.term.a, reader.term.n);
+          pNode->key.n = reader.term.n;
+          if( i>0 ){
+            char *aBlock = 0;
+            int nBlock = 0;
+            pNode = &pWriter->aNodeWriter[i-1];
+            pNode->iBlock = reader.iChild;
+            rc = sqlite3Fts3ReadBlock(p, reader.iChild, &aBlock, &nBlock, 0);
+            blobGrowBuffer(&pNode->block, MAX(nBlock, p->nNodeSize), &rc);
+            if( rc==SQLITE_OK ){
+              memcpy(pNode->block.a, aBlock, nBlock);
+              pNode->block.n = nBlock;
+            }
+            sqlite3_free(aBlock);
+          }
+        }
+        nodeReaderRelease(&reader);
+      }
     }
-  }
 
-#ifndef NDEBUG
-  /* Check that the list really is sorted now. */
-  for(i=0; i<(nSuspect-1); i++){
-    assert( xCmp(apSegment[i], apSegment[i+1])<0 );
+    rc2 = sqlite3_reset(pSelect);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
-#endif
-}
 
-/* 
-** Insert a record into the %_segments table.
-*/
-static int fts3WriteSegment(
-  Fts3Table *p,                   /* Virtual table handle */
-  sqlite3_int64 iBlock,           /* Block id for new block */
-  char *z,                        /* Pointer to buffer containing block data */
-  int n                           /* Size of buffer z in bytes */
-){
-  sqlite3_stmt *pStmt;
-  int rc = fts3SqlStmt(p, SQL_INSERT_SEGMENTS, &pStmt, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pStmt, 1, iBlock);
-    sqlite3_bind_blob(pStmt, 2, z, n, SQLITE_STATIC);
-    sqlite3_step(pStmt);
-    rc = sqlite3_reset(pStmt);
-  }
   return rc;
 }
 
 /*
-** Find the largest relative level number in the table. If successful, set
-** *pnMax to this value and return SQLITE_OK. Otherwise, if an error occurs,
-** set *pnMax to zero and return an SQLite error code.
+** Determine the largest segment index value that exists within absolute
+** level iAbsLevel+1. If no error occurs, set *piIdx to this value plus
+** one before returning SQLITE_OK. Or, if there are no segments at all 
+** within level iAbsLevel, set *piIdx to zero.
+**
+** If an error occurs, return an SQLite error code. The final value of
+** *piIdx is undefined in this case.
 */
-SQLITE_PRIVATE int sqlite3Fts3MaxLevel(Fts3Table *p, int *pnMax){
+static int fts3IncrmergeOutputIdx( 
+  Fts3Table *p,                   /* FTS Table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute index of input segments */
+  int *piIdx                      /* OUT: Next free index at iAbsLevel+1 */
+){
   int rc;
-  int mxLevel = 0;
-  sqlite3_stmt *pStmt = 0;
+  sqlite3_stmt *pOutputIdx = 0;   /* SQL used to find output index */
 
-  rc = fts3SqlStmt(p, SQL_SELECT_MXLEVEL, &pStmt, 0);
+  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENT_INDEX, &pOutputIdx, 0);
   if( rc==SQLITE_OK ){
-    if( SQLITE_ROW==sqlite3_step(pStmt) ){
-      mxLevel = sqlite3_column_int(pStmt, 0);
-    }
-    rc = sqlite3_reset(pStmt);
+    sqlite3_bind_int64(pOutputIdx, 1, iAbsLevel+1);
+    sqlite3_step(pOutputIdx);
+    *piIdx = sqlite3_column_int(pOutputIdx, 0);
+    rc = sqlite3_reset(pOutputIdx);
   }
-  *pnMax = mxLevel;
+
   return rc;
 }
 
 /* 
-** Insert a record into the %_segdir table.
+** Allocate an appendable output segment on absolute level iAbsLevel+1
+** with idx value iIdx.
+**
+** In the %_segdir table, a segment is defined by the values in three
+** columns:
+**
+**     start_block
+**     leaves_end_block
+**     end_block
+**
+** When an appendable segment is allocated, it is estimated that the
+** maximum number of leaf blocks that may be required is the sum of the
+** number of leaf blocks consumed by the input segments, plus the number
+** of input segments, multiplied by two. This value is stored in stack 
+** variable nLeafEst.
+**
+** A total of 16*nLeafEst blocks are allocated when an appendable segment
+** is created ((1 + end_block - start_block)==16*nLeafEst). The contiguous
+** array of leaf nodes starts at the first block allocated. The array
+** of interior nodes that are parents of the leaf nodes start at block
+** (start_block + (1 + end_block - start_block) / 16). And so on.
+**
+** In the actual code below, the value "16" is replaced with the 
+** pre-processor macro FTS_MAX_APPENDABLE_HEIGHT.
 */
-static int fts3WriteSegdir(
-  Fts3Table *p,                   /* Virtual table handle */
-  sqlite3_int64 iLevel,           /* Value for "level" field (absolute level) */
-  int iIdx,                       /* Value for "idx" field */
-  sqlite3_int64 iStartBlock,      /* Value for "start_block" field */
-  sqlite3_int64 iLeafEndBlock,    /* Value for "leaves_end_block" field */
-  sqlite3_int64 iEndBlock,        /* Value for "end_block" field */
-  sqlite3_int64 nLeafData,        /* Bytes of leaf data in segment */
-  char *zRoot,                    /* Blob value for "root" field */
-  int nRoot                       /* Number of bytes in buffer zRoot */
+static int fts3IncrmergeWriter( 
+  Fts3Table *p,                   /* Fts3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level of input segments */
+  int iIdx,                       /* Index of new output segment */
+  Fts3MultiSegReader *pCsr,       /* Cursor that data will be read from */
+  IncrmergeWriter *pWriter        /* Populate this object */
 ){
-  sqlite3_stmt *pStmt;
-  int rc = fts3SqlStmt(p, SQL_INSERT_SEGDIR, &pStmt, 0);
+  int rc;                         /* Return Code */
+  int i;                          /* Iterator variable */
+  int nLeafEst = 0;               /* Blocks allocated for leaf nodes */
+  sqlite3_stmt *pLeafEst = 0;     /* SQL used to determine nLeafEst */
+  sqlite3_stmt *pFirstBlock = 0;  /* SQL used to determine first block */
+
+  /* Calculate nLeafEst. */
+  rc = fts3SqlStmt(p, SQL_MAX_LEAF_NODE_ESTIMATE, &pLeafEst, 0);
   if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pStmt, 1, iLevel);
-    sqlite3_bind_int(pStmt, 2, iIdx);
-    sqlite3_bind_int64(pStmt, 3, iStartBlock);
-    sqlite3_bind_int64(pStmt, 4, iLeafEndBlock);
-    if( nLeafData==0 ){
-      sqlite3_bind_int64(pStmt, 5, iEndBlock);
-    }else{
-      char *zEnd = sqlite3_mprintf("%lld %lld", iEndBlock, nLeafData);
-      if( !zEnd ) return SQLITE_NOMEM;
-      sqlite3_bind_text(pStmt, 5, zEnd, -1, sqlite3_free);
+    sqlite3_bind_int64(pLeafEst, 1, iAbsLevel);
+    sqlite3_bind_int64(pLeafEst, 2, pCsr->nSegment);
+    if( SQLITE_ROW==sqlite3_step(pLeafEst) ){
+      nLeafEst = sqlite3_column_int(pLeafEst, 0);
     }
-    sqlite3_bind_blob(pStmt, 6, zRoot, nRoot, SQLITE_STATIC);
-    sqlite3_step(pStmt);
-    rc = sqlite3_reset(pStmt);
+    rc = sqlite3_reset(pLeafEst);
   }
-  return rc;
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Calculate the first block to use in the output segment */
+  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENTS_ID, &pFirstBlock, 0);
+  if( rc==SQLITE_OK ){
+    if( SQLITE_ROW==sqlite3_step(pFirstBlock) ){
+      pWriter->iStart = sqlite3_column_int64(pFirstBlock, 0);
+      pWriter->iEnd = pWriter->iStart - 1;
+      pWriter->iEnd += nLeafEst * FTS_MAX_APPENDABLE_HEIGHT;
+    }
+    rc = sqlite3_reset(pFirstBlock);
+  }
+  if( rc!=SQLITE_OK ) return rc;
+
+  /* Insert the marker in the %_segments table to make sure nobody tries
+  ** to steal the space just allocated. This is also used to identify 
+  ** appendable segments.  */
+  rc = fts3WriteSegment(p, pWriter->iEnd, 0, 0);
+  if( rc!=SQLITE_OK ) return rc;
+
+  pWriter->iAbsLevel = iAbsLevel;
+  pWriter->nLeafEst = nLeafEst;
+  pWriter->iIdx = iIdx;
+
+  /* Set up the array of NodeWriter objects */
+  for(i=0; i<FTS_MAX_APPENDABLE_HEIGHT; i++){
+    pWriter->aNodeWriter[i].iBlock = pWriter->iStart + i*pWriter->nLeafEst;
+  }
+  return SQLITE_OK;
 }
 
 /*
-** Return the size of the common prefix (if any) shared by zPrev and
-** zNext, in bytes. For example, 
+** Remove an entry from the %_segdir table. This involves running the 
+** following two statements:
 **
-**   fts3PrefixCompress("abc", 3, "abcdef", 6)   // returns 3
-**   fts3PrefixCompress("abX", 3, "abcdef", 6)   // returns 2
-**   fts3PrefixCompress("abX", 3, "Xbcdef", 6)   // returns 0
+**   DELETE FROM %_segdir WHERE level = :iAbsLevel AND idx = :iIdx
+**   UPDATE %_segdir SET idx = idx - 1 WHERE level = :iAbsLevel AND idx > :iIdx
+**
+** The DELETE statement removes the specific %_segdir level. The UPDATE 
+** statement ensures that the remaining segments have contiguously allocated
+** idx values.
 */
-static int fts3PrefixCompress(
-  const char *zPrev,              /* Buffer containing previous term */
-  int nPrev,                      /* Size of buffer zPrev in bytes */
-  const char *zNext,              /* Buffer containing next term */
-  int nNext                       /* Size of buffer zNext in bytes */
+static int fts3RemoveSegdirEntry(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level to delete from */
+  int iIdx                        /* Index of %_segdir entry to delete */
 ){
-  int n;
-  UNUSED_PARAMETER(nNext);
-  for(n=0; n<nPrev && zPrev[n]==zNext[n]; n++);
-  return n;
+  int rc;                         /* Return code */
+  sqlite3_stmt *pDelete = 0;      /* DELETE statement */
+
+  rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_ENTRY, &pDelete, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pDelete, 1, iAbsLevel);
+    sqlite3_bind_int(pDelete, 2, iIdx);
+    sqlite3_step(pDelete);
+    rc = sqlite3_reset(pDelete);
+  }
+
+  return rc;
 }
 
 /*
-** Add term zTerm to the SegmentNode. It is guaranteed that zTerm is larger
-** (according to memcmp) than the previous term.
+** One or more segments have just been removed from absolute level iAbsLevel.
+** Update the 'idx' values of the remaining segments in the level so that
+** the idx values are a contiguous sequence starting from 0.
 */
-static int fts3NodeAddTerm(
-  Fts3Table *p,                   /* Virtual table handle */
-  SegmentNode **ppTree,           /* IN/OUT: SegmentNode handle */ 
-  int isCopyTerm,                 /* True if zTerm/nTerm is transient */
-  const char *zTerm,              /* Pointer to buffer containing term */
-  int nTerm                       /* Size of term in bytes */
+static int fts3RepackSegdirLevel(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel         /* Absolute level to repack */
 ){
-  SegmentNode *pTree = *ppTree;
-  int rc;
-  SegmentNode *pNew;
-
-  /* First try to append the term to the current node. Return early if 
-  ** this is possible.
-  */
-  if( pTree ){
-    int nData = pTree->nData;     /* Current size of node in bytes */
-    int nReq = nData;             /* Required space after adding zTerm */
-    int nPrefix;                  /* Number of bytes of prefix compression */
-    int nSuffix;                  /* Suffix length */
-
-    nPrefix = fts3PrefixCompress(pTree->zTerm, pTree->nTerm, zTerm, nTerm);
-    nSuffix = nTerm-nPrefix;
-
-    nReq += sqlite3Fts3VarintLen(nPrefix)+sqlite3Fts3VarintLen(nSuffix)+nSuffix;
-    if( nReq<=p->nNodeSize || !pTree->zTerm ){
-
-      if( nReq>p->nNodeSize ){
-        /* An unusual case: this is the first term to be added to the node
-        ** and the static node buffer (p->nNodeSize bytes) is not large
-        ** enough. Use a separately malloced buffer instead This wastes
-        ** p->nNodeSize bytes, but since this scenario only comes about when
-        ** the database contain two terms that share a prefix of almost 2KB, 
-        ** this is not expected to be a serious problem. 
-        */
-        assert( pTree->aData==(char *)&pTree[1] );
-        pTree->aData = (char *)sqlite3_malloc(nReq);
-        if( !pTree->aData ){
-          return SQLITE_NOMEM;
-        }
-      }
-
-      if( pTree->zTerm ){
-        /* There is no prefix-length field for first term in a node */
-        nData += sqlite3Fts3PutVarint(&pTree->aData[nData], nPrefix);
-      }
-
-      nData += sqlite3Fts3PutVarint(&pTree->aData[nData], nSuffix);
-      memcpy(&pTree->aData[nData], &zTerm[nPrefix], nSuffix);
-      pTree->nData = nData + nSuffix;
-      pTree->nEntry++;
+  int rc;                         /* Return code */
+  int *aIdx = 0;                  /* Array of remaining idx values */
+  int nIdx = 0;                   /* Valid entries in aIdx[] */
+  int nAlloc = 0;                 /* Allocated size of aIdx[] */
+  int i;                          /* Iterator variable */
+  sqlite3_stmt *pSelect = 0;      /* Select statement to read idx values */
+  sqlite3_stmt *pUpdate = 0;      /* Update statement to modify idx values */
 
-      if( isCopyTerm ){
-        if( pTree->nMalloc<nTerm ){
-          char *zNew = sqlite3_realloc(pTree->zMalloc, nTerm*2);
-          if( !zNew ){
-            return SQLITE_NOMEM;
-          }
-          pTree->nMalloc = nTerm*2;
-          pTree->zMalloc = zNew;
+  rc = fts3SqlStmt(p, SQL_SELECT_INDEXES, &pSelect, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int64(pSelect, 1, iAbsLevel);
+    while( SQLITE_ROW==sqlite3_step(pSelect) ){
+      if( nIdx>=nAlloc ){
+        int *aNew;
+        nAlloc += 16;
+        aNew = sqlite3_realloc(aIdx, nAlloc*sizeof(int));
+        if( !aNew ){
+          rc = SQLITE_NOMEM;
+          break;
         }
-        pTree->zTerm = pTree->zMalloc;
-        memcpy(pTree->zTerm, zTerm, nTerm);
-        pTree->nTerm = nTerm;
-      }else{
-        pTree->zTerm = (char *)zTerm;
-        pTree->nTerm = nTerm;
+        aIdx = aNew;
       }
-      return SQLITE_OK;
+      aIdx[nIdx++] = sqlite3_column_int(pSelect, 0);
     }
+    rc2 = sqlite3_reset(pSelect);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
 
-  /* If control flows to here, it was not possible to append zTerm to the
-  ** current node. Create a new node (a right-sibling of the current node).
-  ** If this is the first node in the tree, the term is added to it.
-  **
-  ** Otherwise, the term is not added to the new node, it is left empty for
-  ** now. Instead, the term is inserted into the parent of pTree. If pTree 
-  ** has no parent, one is created here.
-  */
-  pNew = (SegmentNode *)sqlite3_malloc(sizeof(SegmentNode) + p->nNodeSize);
-  if( !pNew ){
-    return SQLITE_NOMEM;
+  if( rc==SQLITE_OK ){
+    rc = fts3SqlStmt(p, SQL_SHIFT_SEGDIR_ENTRY, &pUpdate, 0);
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pUpdate, 2, iAbsLevel);
   }
-  memset(pNew, 0, sizeof(SegmentNode));
-  pNew->nData = 1 + FTS3_VARINT_MAX;
-  pNew->aData = (char *)&pNew[1];
 
-  if( pTree ){
-    SegmentNode *pParent = pTree->pParent;
-    rc = fts3NodeAddTerm(p, &pParent, isCopyTerm, zTerm, nTerm);
-    if( pTree->pParent==0 ){
-      pTree->pParent = pParent;
+  assert( p->bIgnoreSavepoint==0 );
+  p->bIgnoreSavepoint = 1;
+  for(i=0; rc==SQLITE_OK && i<nIdx; i++){
+    if( aIdx[i]!=i ){
+      sqlite3_bind_int(pUpdate, 3, aIdx[i]);
+      sqlite3_bind_int(pUpdate, 1, i);
+      sqlite3_step(pUpdate);
+      rc = sqlite3_reset(pUpdate);
     }
-    pTree->pRight = pNew;
-    pNew->pLeftmost = pTree->pLeftmost;
-    pNew->pParent = pParent;
-    pNew->zMalloc = pTree->zMalloc;
-    pNew->nMalloc = pTree->nMalloc;
-    pTree->zMalloc = 0;
-  }else{
-    pNew->pLeftmost = pNew;
-    rc = fts3NodeAddTerm(p, &pNew, isCopyTerm, zTerm, nTerm); 
   }
+  p->bIgnoreSavepoint = 0;
 
-  *ppTree = pNew;
+  sqlite3_free(aIdx);
   return rc;
 }
 
-/*
-** Helper function for fts3NodeWrite().
-*/
-static int fts3TreeFinishNode(
-  SegmentNode *pTree, 
-  int iHeight, 
-  sqlite3_int64 iLeftChild
-){
-  int nStart;
-  assert( iHeight>=1 && iHeight<128 );
-  nStart = FTS3_VARINT_MAX - sqlite3Fts3VarintLen(iLeftChild);
-  pTree->aData[nStart] = (char)iHeight;
-  sqlite3Fts3PutVarint(&pTree->aData[nStart+1], iLeftChild);
-  return nStart;
+static void fts3StartNode(Blob *pNode, int iHeight, sqlite3_int64 iChild){
+  pNode->a[0] = (char)iHeight;
+  if( iChild ){
+    assert( pNode->nAlloc>=1+sqlite3Fts3VarintLen(iChild) );
+    pNode->n = 1 + sqlite3Fts3PutVarint(&pNode->a[1], iChild);
+  }else{
+    assert( pNode->nAlloc>=1 );
+    pNode->n = 1;
+  }
 }
 
 /*
-** Write the buffer for the segment node pTree and all of its peers to the
-** database. Then call this function recursively to write the parent of 
-** pTree and its peers to the database. 
-**
-** Except, if pTree is a root node, do not write it to the database. Instead,
-** set output variables *paRoot and *pnRoot to contain the root node.
+** The first two arguments are a pointer to and the size of a segment b-tree
+** node. The node may be a leaf or an internal node.
 **
-** If successful, SQLITE_OK is returned and output variable *piLast is
-** set to the largest blockid written to the database (or zero if no
-** blocks were written to the db). Otherwise, an SQLite error code is 
-** returned.
+** This function creates a new node image in blob object *pNew by copying
+** all terms that are greater than or equal to zTerm/nTerm (for leaf nodes)
+** or greater than zTerm/nTerm (for internal nodes) from aNode/nNode.
 */
-static int fts3NodeWrite(
-  Fts3Table *p,                   /* Virtual table handle */
-  SegmentNode *pTree,             /* SegmentNode handle */
-  int iHeight,                    /* Height of this node in tree */
-  sqlite3_int64 iLeaf,            /* Block id of first leaf node */
-  sqlite3_int64 iFree,            /* Block id of next free slot in %_segments */
-  sqlite3_int64 *piLast,          /* OUT: Block id of last entry written */
-  char **paRoot,                  /* OUT: Data for root node */
-  int *pnRoot                     /* OUT: Size of root node in bytes */
+static int fts3TruncateNode(
+  const char *aNode,              /* Current node image */
+  int nNode,                      /* Size of aNode in bytes */
+  Blob *pNew,                     /* OUT: Write new node image here */
+  const char *zTerm,              /* Omit all terms smaller than this */
+  int nTerm,                      /* Size of zTerm in bytes */
+  sqlite3_int64 *piBlock          /* OUT: Block number in next layer down */
 ){
-  int rc = SQLITE_OK;
+  NodeReader reader;              /* Reader object */
+  Blob prev = {0, 0, 0};          /* Previous term written to new node */
+  int rc = SQLITE_OK;             /* Return code */
+  int bLeaf = aNode[0]=='\0';     /* True for a leaf node */
 
-  if( !pTree->pParent ){
-    /* Root node of the tree. */
-    int nStart = fts3TreeFinishNode(pTree, iHeight, iLeaf);
-    *piLast = iFree-1;
-    *pnRoot = pTree->nData - nStart;
-    *paRoot = &pTree->aData[nStart];
-  }else{
-    SegmentNode *pIter;
-    sqlite3_int64 iNextFree = iFree;
-    sqlite3_int64 iNextLeaf = iLeaf;
-    for(pIter=pTree->pLeftmost; pIter && rc==SQLITE_OK; pIter=pIter->pRight){
-      int nStart = fts3TreeFinishNode(pIter, iHeight, iNextLeaf);
-      int nWrite = pIter->nData - nStart;
-  
-      rc = fts3WriteSegment(p, iNextFree, &pIter->aData[nStart], nWrite);
-      iNextFree++;
-      iNextLeaf += (pIter->nEntry+1);
-    }
-    if( rc==SQLITE_OK ){
-      assert( iNextLeaf==iFree );
-      rc = fts3NodeWrite(
-          p, pTree->pParent, iHeight+1, iFree, iNextFree, piLast, paRoot, pnRoot
-      );
+  /* Allocate required output space */
+  blobGrowBuffer(pNew, nNode, &rc);
+  if( rc!=SQLITE_OK ) return rc;
+  pNew->n = 0;
+
+  /* Populate new node buffer */
+  for(rc = nodeReaderInit(&reader, aNode, nNode); 
+      rc==SQLITE_OK && reader.aNode; 
+      rc = nodeReaderNext(&reader)
+  ){
+    if( pNew->n==0 ){
+      int res = fts3TermCmp(reader.term.a, reader.term.n, zTerm, nTerm);
+      if( res<0 || (bLeaf==0 && res==0) ) continue;
+      fts3StartNode(pNew, (int)aNode[0], reader.iChild);
+      *piBlock = reader.iChild;
     }
+    rc = fts3AppendToNode(
+        pNew, &prev, reader.term.a, reader.term.n,
+        reader.aDoclist, reader.nDoclist
+    );
+    if( rc!=SQLITE_OK ) break;
+  }
+  if( pNew->n==0 ){
+    fts3StartNode(pNew, (int)aNode[0], reader.iChild);
+    *piBlock = reader.iChild;
   }
+  assert( pNew->n<=pNew->nAlloc );
 
+  nodeReaderRelease(&reader);
+  sqlite3_free(prev.a);
   return rc;
 }
 
 /*
-** Free all memory allocations associated with the tree pTree.
-*/
-static void fts3NodeFree(SegmentNode *pTree){
-  if( pTree ){
-    SegmentNode *p = pTree->pLeftmost;
-    fts3NodeFree(p->pParent);
-    while( p ){
-      SegmentNode *pRight = p->pRight;
-      if( p->aData!=(char *)&p[1] ){
-        sqlite3_free(p->aData);
-      }
-      assert( pRight==0 || p->zMalloc==0 );
-      sqlite3_free(p->zMalloc);
-      sqlite3_free(p);
-      p = pRight;
-    }
-  }
-}
-
-/*
-** Add a term to the segment being constructed by the SegmentWriter object
-** *ppWriter. When adding the first term to a segment, *ppWriter should
-** be passed NULL. This function will allocate a new SegmentWriter object
-** and return it via the input/output variable *ppWriter in this case.
+** Remove all terms smaller than zTerm/nTerm from segment iIdx in absolute 
+** level iAbsLevel. This may involve deleting entries from the %_segments
+** table, and modifying existing entries in both the %_segments and %_segdir
+** tables.
 **
-** If successful, SQLITE_OK is returned. Otherwise, an SQLite error code.
+** SQLITE_OK is returned if the segment is updated successfully. Or an
+** SQLite error code otherwise.
 */
-static int fts3SegWriterAdd(
-  Fts3Table *p,                   /* Virtual table handle */
-  SegmentWriter **ppWriter,       /* IN/OUT: SegmentWriter handle */ 
-  int isCopyTerm,                 /* True if buffer zTerm must be copied */
-  const char *zTerm,              /* Pointer to buffer containing term */
-  int nTerm,                      /* Size of term in bytes */
-  const char *aDoclist,           /* Pointer to buffer containing doclist */
-  int nDoclist                    /* Size of doclist in bytes */
+static int fts3TruncateSegment(
+  Fts3Table *p,                   /* FTS3 table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level of segment to modify */
+  int iIdx,                       /* Index within level of segment to modify */
+  const char *zTerm,              /* Remove terms smaller than this */
+  int nTerm                      /* Number of bytes in buffer zTerm */
 ){
-  int nPrefix;                    /* Size of term prefix in bytes */
-  int nSuffix;                    /* Size of term suffix in bytes */
-  int nReq;                       /* Number of bytes required on leaf page */
-  int nData;
-  SegmentWriter *pWriter = *ppWriter;
-
-  if( !pWriter ){
-    int rc;
-    sqlite3_stmt *pStmt;
-
-    /* Allocate the SegmentWriter structure */
-    pWriter = (SegmentWriter *)sqlite3_malloc(sizeof(SegmentWriter));
-    if( !pWriter ) return SQLITE_NOMEM;
-    memset(pWriter, 0, sizeof(SegmentWriter));
-    *ppWriter = pWriter;
-
-    /* Allocate a buffer in which to accumulate data */
-    pWriter->aData = (char *)sqlite3_malloc(p->nNodeSize);
-    if( !pWriter->aData ) return SQLITE_NOMEM;
-    pWriter->nSize = p->nNodeSize;
+  int rc = SQLITE_OK;             /* Return code */
+  Blob root = {0,0,0};            /* New root page image */
+  Blob block = {0,0,0};           /* Buffer used for any other block */
+  sqlite3_int64 iBlock = 0;       /* Block id */
+  sqlite3_int64 iNewStart = 0;    /* New value for iStartBlock */
+  sqlite3_int64 iOldStart = 0;    /* Old value for iStartBlock */
+  sqlite3_stmt *pFetch = 0;       /* Statement used to fetch segdir */
 
-    /* Find the next free blockid in the %_segments table */
-    rc = fts3SqlStmt(p, SQL_NEXT_SEGMENTS_ID, &pStmt, 0);
-    if( rc!=SQLITE_OK ) return rc;
-    if( SQLITE_ROW==sqlite3_step(pStmt) ){
-      pWriter->iFree = sqlite3_column_int64(pStmt, 0);
-      pWriter->iFirst = pWriter->iFree;
+  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR, &pFetch, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;                      /* sqlite3_reset() return code */
+    sqlite3_bind_int64(pFetch, 1, iAbsLevel);
+    sqlite3_bind_int(pFetch, 2, iIdx);
+    if( SQLITE_ROW==sqlite3_step(pFetch) ){
+      const char *aRoot = sqlite3_column_blob(pFetch, 4);
+      int nRoot = sqlite3_column_bytes(pFetch, 4);
+      iOldStart = sqlite3_column_int64(pFetch, 1);
+      rc = fts3TruncateNode(aRoot, nRoot, &root, zTerm, nTerm, &iBlock);
     }
-    rc = sqlite3_reset(pStmt);
-    if( rc!=SQLITE_OK ) return rc;
+    rc2 = sqlite3_reset(pFetch);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
-  nData = pWriter->nData;
-
-  nPrefix = fts3PrefixCompress(pWriter->zTerm, pWriter->nTerm, zTerm, nTerm);
-  nSuffix = nTerm-nPrefix;
 
-  /* Figure out how many bytes are required by this new entry */
-  nReq = sqlite3Fts3VarintLen(nPrefix) +    /* varint containing prefix size */
-    sqlite3Fts3VarintLen(nSuffix) +         /* varint containing suffix size */
-    nSuffix +                               /* Term suffix */
-    sqlite3Fts3VarintLen(nDoclist) +        /* Size of doclist */
-    nDoclist;                               /* Doclist data */
-
-  if( nData>0 && nData+nReq>p->nNodeSize ){
-    int rc;
-
-    /* The current leaf node is full. Write it out to the database. */
-    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, nData);
-    if( rc!=SQLITE_OK ) return rc;
-    p->nLeafAdd++;
-
-    /* Add the current term to the interior node tree. The term added to
-    ** the interior tree must:
-    **
-    **   a) be greater than the largest term on the leaf node just written
-    **      to the database (still available in pWriter->zTerm), and
-    **
-    **   b) be less than or equal to the term about to be added to the new
-    **      leaf node (zTerm/nTerm).
-    **
-    ** In other words, it must be the prefix of zTerm 1 byte longer than
-    ** the common prefix (if any) of zTerm and pWriter->zTerm.
-    */
-    assert( nPrefix<nTerm );
-    rc = fts3NodeAddTerm(p, &pWriter->pTree, isCopyTerm, zTerm, nPrefix+1);
-    if( rc!=SQLITE_OK ) return rc;
-
-    nData = 0;
-    pWriter->nTerm = 0;
+  while( rc==SQLITE_OK && iBlock ){
+    char *aBlock = 0;
+    int nBlock = 0;
+    iNewStart = iBlock;
 
-    nPrefix = 0;
-    nSuffix = nTerm;
-    nReq = 1 +                              /* varint containing prefix size */
-      sqlite3Fts3VarintLen(nTerm) +         /* varint containing suffix size */
-      nTerm +                               /* Term suffix */
-      sqlite3Fts3VarintLen(nDoclist) +      /* Size of doclist */
-      nDoclist;                             /* Doclist data */
+    rc = sqlite3Fts3ReadBlock(p, iBlock, &aBlock, &nBlock, 0);
+    if( rc==SQLITE_OK ){
+      rc = fts3TruncateNode(aBlock, nBlock, &block, zTerm, nTerm, &iBlock);
+    }
+    if( rc==SQLITE_OK ){
+      rc = fts3WriteSegment(p, iNewStart, block.a, block.n);
+    }
+    sqlite3_free(aBlock);
   }
 
-  /* Increase the total number of bytes written to account for the new entry. */
-  pWriter->nLeafData += nReq;
-
-  /* If the buffer currently allocated is too small for this entry, realloc
-  ** the buffer to make it large enough.
-  */
-  if( nReq>pWriter->nSize ){
-    char *aNew = sqlite3_realloc(pWriter->aData, nReq);
-    if( !aNew ) return SQLITE_NOMEM;
-    pWriter->aData = aNew;
-    pWriter->nSize = nReq;
+  /* Variable iNewStart now contains the first valid leaf node. */
+  if( rc==SQLITE_OK && iNewStart ){
+    sqlite3_stmt *pDel = 0;
+    rc = fts3SqlStmt(p, SQL_DELETE_SEGMENTS_RANGE, &pDel, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pDel, 1, iOldStart);
+      sqlite3_bind_int64(pDel, 2, iNewStart-1);
+      sqlite3_step(pDel);
+      rc = sqlite3_reset(pDel);
+    }
   }
-  assert( nData+nReq<=pWriter->nSize );
-
-  /* Append the prefix-compressed term and doclist to the buffer. */
-  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nPrefix);
-  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nSuffix);
-  memcpy(&pWriter->aData[nData], &zTerm[nPrefix], nSuffix);
-  nData += nSuffix;
-  nData += sqlite3Fts3PutVarint(&pWriter->aData[nData], nDoclist);
-  memcpy(&pWriter->aData[nData], aDoclist, nDoclist);
-  pWriter->nData = nData + nDoclist;
 
-  /* Save the current term so that it can be used to prefix-compress the next.
-  ** If the isCopyTerm parameter is true, then the buffer pointed to by
-  ** zTerm is transient, so take a copy of the term data. Otherwise, just
-  ** store a copy of the pointer.
-  */
-  if( isCopyTerm ){
-    if( nTerm>pWriter->nMalloc ){
-      char *zNew = sqlite3_realloc(pWriter->zMalloc, nTerm*2);
-      if( !zNew ){
-        return SQLITE_NOMEM;
-      }
-      pWriter->nMalloc = nTerm*2;
-      pWriter->zMalloc = zNew;
-      pWriter->zTerm = zNew;
+  if( rc==SQLITE_OK ){
+    sqlite3_stmt *pChomp = 0;
+    rc = fts3SqlStmt(p, SQL_CHOMP_SEGDIR, &pChomp, 0);
+    if( rc==SQLITE_OK ){
+      sqlite3_bind_int64(pChomp, 1, iNewStart);
+      sqlite3_bind_blob(pChomp, 2, root.a, root.n, SQLITE_STATIC);
+      sqlite3_bind_int64(pChomp, 3, iAbsLevel);
+      sqlite3_bind_int(pChomp, 4, iIdx);
+      sqlite3_step(pChomp);
+      rc = sqlite3_reset(pChomp);
     }
-    assert( pWriter->zTerm==pWriter->zMalloc );
-    memcpy(pWriter->zTerm, zTerm, nTerm);
-  }else{
-    pWriter->zTerm = (char *)zTerm;
   }
-  pWriter->nTerm = nTerm;
 
-  return SQLITE_OK;
+  sqlite3_free(root.a);
+  sqlite3_free(block.a);
+  return rc;
 }
 
 /*
-** Flush all data associated with the SegmentWriter object pWriter to the
-** database. This function must be called after all terms have been added
-** to the segment using fts3SegWriterAdd(). If successful, SQLITE_OK is
-** returned. Otherwise, an SQLite error code.
+** This function is called after an incrmental-merge operation has run to
+** merge (or partially merge) two or more segments from absolute level
+** iAbsLevel.
+**
+** Each input segment is either removed from the db completely (if all of
+** its data was copied to the output segment by the incrmerge operation)
+** or modified in place so that it no longer contains those entries that
+** have been duplicated in the output segment.
 */
-static int fts3SegWriterFlush(
-  Fts3Table *p,                   /* Virtual table handle */
-  SegmentWriter *pWriter,         /* SegmentWriter to flush to the db */
-  sqlite3_int64 iLevel,           /* Value for 'level' column of %_segdir */
-  int iIdx                        /* Value for 'idx' column of %_segdir */
+static int fts3IncrmergeChomp(
+  Fts3Table *p,                   /* FTS table handle */
+  sqlite3_int64 iAbsLevel,        /* Absolute level containing segments */
+  Fts3MultiSegReader *pCsr,       /* Chomp all segments opened by this cursor */
+  int *pnRem                      /* Number of segments not deleted */
 ){
-  int rc;                         /* Return code */
-  if( pWriter->pTree ){
-    sqlite3_int64 iLast = 0;      /* Largest block id written to database */
-    sqlite3_int64 iLastLeaf;      /* Largest leaf block id written to db */
-    char *zRoot = NULL;           /* Pointer to buffer containing root node */
-    int nRoot = 0;                /* Size of buffer zRoot */
+  int i;
+  int nRem = 0;
+  int rc = SQLITE_OK;
 
-    iLastLeaf = pWriter->iFree;
-    rc = fts3WriteSegment(p, pWriter->iFree++, pWriter->aData, pWriter->nData);
-    if( rc==SQLITE_OK ){
-      rc = fts3NodeWrite(p, pWriter->pTree, 1,
-          pWriter->iFirst, pWriter->iFree, &iLast, &zRoot, &nRoot);
+  for(i=pCsr->nSegment-1; i>=0 && rc==SQLITE_OK; i--){
+    Fts3SegReader *pSeg = 0;
+    int j;
+
+    /* Find the Fts3SegReader object with Fts3SegReader.iIdx==i. It is hiding
+    ** somewhere in the pCsr->apSegment[] array.  */
+    for(j=0; ALWAYS(j<pCsr->nSegment); j++){
+      pSeg = pCsr->apSegment[j];
+      if( pSeg->iIdx==i ) break;
     }
-    if( rc==SQLITE_OK ){
-      rc = fts3WriteSegdir(p, iLevel, iIdx, 
-          pWriter->iFirst, iLastLeaf, iLast, pWriter->nLeafData, zRoot, nRoot);
+    assert( j<pCsr->nSegment && pSeg->iIdx==i );
+
+    if( pSeg->aNode==0 ){
+      /* Seg-reader is at EOF. Remove the entire input segment. */
+      rc = fts3DeleteSegment(p, pSeg);
+      if( rc==SQLITE_OK ){
+        rc = fts3RemoveSegdirEntry(p, iAbsLevel, pSeg->iIdx);
+      }
+      *pnRem = 0;
+    }else{
+      /* The incremental merge did not copy all the data from this 
+      ** segment to the upper level. The segment is modified in place
+      ** so that it contains no keys smaller than zTerm/nTerm. */ 
+      const char *zTerm = pSeg->zTerm;
+      int nTerm = pSeg->nTerm;
+      rc = fts3TruncateSegment(p, iAbsLevel, pSeg->iIdx, zTerm, nTerm);
+      nRem++;
     }
-  }else{
-    /* The entire tree fits on the root node. Write it to the segdir table. */
-    rc = fts3WriteSegdir(p, iLevel, iIdx, 
-        0, 0, 0, pWriter->nLeafData, pWriter->aData, pWriter->nData);
   }
-  p->nLeafAdd++;
+
+  if( rc==SQLITE_OK && nRem!=pCsr->nSegment ){
+    rc = fts3RepackSegdirLevel(p, iAbsLevel);
+  }
+
+  *pnRem = nRem;
   return rc;
 }
 
 /*
-** Release all memory held by the SegmentWriter object passed as the 
-** first argument.
+** Store an incr-merge hint in the database.
 */
-static void fts3SegWriterFree(SegmentWriter *pWriter){
-  if( pWriter ){
-    sqlite3_free(pWriter->aData);
-    sqlite3_free(pWriter->zMalloc);
-    fts3NodeFree(pWriter->pTree);
-    sqlite3_free(pWriter);
+static int fts3IncrmergeHintStore(Fts3Table *p, Blob *pHint){
+  sqlite3_stmt *pReplace = 0;
+  int rc;                         /* Return code */
+
+  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pReplace, 0);
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int(pReplace, 1, FTS_STAT_INCRMERGEHINT);
+    sqlite3_bind_blob(pReplace, 2, pHint->a, pHint->n, SQLITE_STATIC);
+    sqlite3_step(pReplace);
+    rc = sqlite3_reset(pReplace);
   }
+
+  return rc;
 }
 
 /*
-** The first value in the apVal[] array is assumed to contain an integer.
-** This function tests if there exist any documents with docid values that
-** are different from that integer. i.e. if deleting the document with docid
-** pRowid would mean the FTS3 table were empty.
+** Load an incr-merge hint from the database. The incr-merge hint, if one 
+** exists, is stored in the rowid==1 row of the %_stat table.
 **
-** If successful, *pisEmpty is set to true if the table is empty except for
-** document pRowid, or false otherwise, and SQLITE_OK is returned. If an
-** error occurs, an SQLite error code is returned.
+** If successful, populate blob *pHint with the value read from the %_stat
+** table and return SQLITE_OK. Otherwise, if an error occurs, return an
+** SQLite error code.
 */
-static int fts3IsEmpty(Fts3Table *p, sqlite3_value *pRowid, int *pisEmpty){
-  sqlite3_stmt *pStmt;
+static int fts3IncrmergeHintLoad(Fts3Table *p, Blob *pHint){
+  sqlite3_stmt *pSelect = 0;
   int rc;
-  if( p->zContentTbl ){
-    /* If using the content=xxx option, assume the table is never empty */
-    *pisEmpty = 0;
-    rc = SQLITE_OK;
-  }else{
-    rc = fts3SqlStmt(p, SQL_IS_EMPTY, &pStmt, &pRowid);
-    if( rc==SQLITE_OK ){
-      if( SQLITE_ROW==sqlite3_step(pStmt) ){
-        *pisEmpty = sqlite3_column_int(pStmt, 0);
+
+  pHint->n = 0;
+  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pSelect, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int(pSelect, 1, FTS_STAT_INCRMERGEHINT);
+    if( SQLITE_ROW==sqlite3_step(pSelect) ){
+      const char *aHint = sqlite3_column_blob(pSelect, 0);
+      int nHint = sqlite3_column_bytes(pSelect, 0);
+      if( aHint ){
+        blobGrowBuffer(pHint, nHint, &rc);
+        if( rc==SQLITE_OK ){
+          memcpy(pHint->a, aHint, nHint);
+          pHint->n = nHint;
+        }
       }
-      rc = sqlite3_reset(pStmt);
     }
+    rc2 = sqlite3_reset(pSelect);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
+
   return rc;
 }
 
 /*
-** Set *pnMax to the largest segment level in the database for the index
-** iIndex.
-**
-** Segment levels are stored in the 'level' column of the %_segdir table.
+** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, append an entry to the hint stored in blob *pHint. Each entry
+** consists of two varints, the absolute level number of the input segments 
+** and the number of input segments.
 **
-** Return SQLITE_OK if successful, or an SQLite error code if not.
+** If successful, leave *pRc set to SQLITE_OK and return. If an error occurs,
+** set *pRc to an SQLite error code before returning.
 */
-static int fts3SegmentMaxLevel(
-  Fts3Table *p, 
-  int iLangid,
-  int iIndex, 
-  sqlite3_int64 *pnMax
+static void fts3IncrmergeHintPush(
+  Blob *pHint,                    /* Hint blob to append to */
+  i64 iAbsLevel,                  /* First varint to store in hint */
+  int nInput,                     /* Second varint to store in hint */
+  int *pRc                        /* IN/OUT: Error code */
 ){
-  sqlite3_stmt *pStmt;
-  int rc;
-  assert( iIndex>=0 && iIndex<p->nIndex );
-
-  /* Set pStmt to the compiled version of:
-  **
-  **   SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?
-  **
-  ** (1024 is actually the value of macro FTS3_SEGDIR_PREFIXLEVEL_STR).
-  */
-  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR_MAX_LEVEL, &pStmt, 0);
-  if( rc!=SQLITE_OK ) return rc;
-  sqlite3_bind_int64(pStmt, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
-  sqlite3_bind_int64(pStmt, 2, 
-      getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
-  );
-  if( SQLITE_ROW==sqlite3_step(pStmt) ){
-    *pnMax = sqlite3_column_int64(pStmt, 0);
+  blobGrowBuffer(pHint, pHint->n + 2*FTS3_VARINT_MAX, pRc);
+  if( *pRc==SQLITE_OK ){
+    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], iAbsLevel);
+    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], (i64)nInput);
   }
-  return sqlite3_reset(pStmt);
 }
 
 /*
-** iAbsLevel is an absolute level that may be assumed to exist within
-** the database. This function checks if it is the largest level number
-** within its index. Assuming no error occurs, *pbMax is set to 1 if
-** iAbsLevel is indeed the largest level, or 0 otherwise, and SQLITE_OK
-** is returned. If an error occurs, an error code is returned and the
-** final value of *pbMax is undefined.
+** Read the last entry (most recently pushed) from the hint blob *pHint
+** and then remove the entry. Write the two values read to *piAbsLevel and 
+** *pnInput before returning.
+**
+** If no error occurs, return SQLITE_OK. If the hint blob in *pHint does
+** not contain at least two valid varints, return SQLITE_CORRUPT_VTAB.
 */
-static int fts3SegmentIsMaxLevel(Fts3Table *p, i64 iAbsLevel, int *pbMax){
+static int fts3IncrmergeHintPop(Blob *pHint, i64 *piAbsLevel, int *pnInput){
+  const int nHint = pHint->n;
+  int i;
 
-  /* Set pStmt to the compiled version of:
-  **
-  **   SELECT max(level) FROM %Q.'%q_segdir' WHERE level BETWEEN ? AND ?
-  **
-  ** (1024 is actually the value of macro FTS3_SEGDIR_PREFIXLEVEL_STR).
-  */
-  sqlite3_stmt *pStmt;
-  int rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR_MAX_LEVEL, &pStmt, 0);
-  if( rc!=SQLITE_OK ) return rc;
-  sqlite3_bind_int64(pStmt, 1, iAbsLevel+1);
-  sqlite3_bind_int64(pStmt, 2, 
-      ((iAbsLevel/FTS3_SEGDIR_MAXLEVEL)+1) * FTS3_SEGDIR_MAXLEVEL
-  );
+  i = pHint->n-2;
+  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
+  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
 
-  *pbMax = 0;
-  if( SQLITE_ROW==sqlite3_step(pStmt) ){
-    *pbMax = sqlite3_column_type(pStmt, 0)==SQLITE_NULL;
-  }
-  return sqlite3_reset(pStmt);
+  pHint->n = i;
+  i += sqlite3Fts3GetVarint(&pHint->a[i], piAbsLevel);
+  i += fts3GetVarint32(&pHint->a[i], pnInput);
+  if( i!=nHint ) return FTS_CORRUPT_VTAB;
+
+  return SQLITE_OK;
 }
 
+
 /*
-** Delete all entries in the %_segments table associated with the segment
-** opened with seg-reader pSeg. This function does not affect the contents
-** of the %_segdir table.
+** Attempt an incremental merge that writes nMerge leaf blocks.
+**
+** Incremental merges happen nMin segments at a time. The segments 
+** to be merged are the nMin oldest segments (the ones with the smallest 
+** values for the _segdir.idx field) in the highest level that contains 
+** at least nMin segments. Multiple merges might occur in an attempt to 
+** write the quota of nMerge leaf blocks.
 */
-static int fts3DeleteSegment(
-  Fts3Table *p,                   /* FTS table handle */
-  Fts3SegReader *pSeg             /* Segment to delete */
-){
-  int rc = SQLITE_OK;             /* Return code */
-  if( pSeg->iStartBlock ){
-    sqlite3_stmt *pDelete;        /* SQL statement to delete rows */
-    rc = fts3SqlStmt(p, SQL_DELETE_SEGMENTS_RANGE, &pDelete, 0);
+SQLITE_PRIVATE int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
+  int rc;                         /* Return code */
+  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
+  Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
+  Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
+  IncrmergeWriter *pWriter;       /* Writer object */
+  int nSeg = 0;                   /* Number of input segments */
+  sqlite3_int64 iAbsLevel = 0;    /* Absolute level number to work on */
+  Blob hint = {0, 0, 0};          /* Hint read from %_stat table */
+  int bDirtyHint = 0;             /* True if blob 'hint' has been modified */
+
+  /* Allocate space for the cursor, filter and writer objects */
+  const int nAlloc = sizeof(*pCsr) + sizeof(*pFilter) + sizeof(*pWriter);
+  pWriter = (IncrmergeWriter *)sqlite3_malloc(nAlloc);
+  if( !pWriter ) return SQLITE_NOMEM;
+  pFilter = (Fts3SegFilter *)&pWriter[1];
+  pCsr = (Fts3MultiSegReader *)&pFilter[1];
+
+  rc = fts3IncrmergeHintLoad(p, &hint);
+  while( rc==SQLITE_OK && nRem>0 ){
+    const i64 nMod = FTS3_SEGDIR_MAXLEVEL * p->nIndex;
+    sqlite3_stmt *pFindLevel = 0; /* SQL used to determine iAbsLevel */
+    int bUseHint = 0;             /* True if attempting to append */
+    int iIdx = 0;                 /* Largest idx in level (iAbsLevel+1) */
+
+    /* Search the %_segdir table for the absolute level with the smallest
+    ** relative level number that contains at least nMin segments, if any.
+    ** If one is found, set iAbsLevel to the absolute level number and
+    ** nSeg to nMin. If no level with at least nMin segments can be found, 
+    ** set nSeg to -1.
+    */
+    rc = fts3SqlStmt(p, SQL_FIND_MERGE_LEVEL, &pFindLevel, 0);
+    sqlite3_bind_int(pFindLevel, 1, nMin);
+    if( sqlite3_step(pFindLevel)==SQLITE_ROW ){
+      iAbsLevel = sqlite3_column_int64(pFindLevel, 0);
+      nSeg = nMin;
+    }else{
+      nSeg = -1;
+    }
+    rc = sqlite3_reset(pFindLevel);
+
+    /* If the hint read from the %_stat table is not empty, check if the
+    ** last entry in it specifies a relative level smaller than or equal
+    ** to the level identified by the block above (if any). If so, this 
+    ** iteration of the loop will work on merging at the hinted level.
+    */
+    if( rc==SQLITE_OK && hint.n ){
+      int nHint = hint.n;
+      sqlite3_int64 iHintAbsLevel = 0;      /* Hint level */
+      int nHintSeg = 0;                     /* Hint number of segments */
+
+      rc = fts3IncrmergeHintPop(&hint, &iHintAbsLevel, &nHintSeg);
+      if( nSeg<0 || (iAbsLevel % nMod) >= (iHintAbsLevel % nMod) ){
+        iAbsLevel = iHintAbsLevel;
+        nSeg = nHintSeg;
+        bUseHint = 1;
+        bDirtyHint = 1;
+      }else{
+        /* This undoes the effect of the HintPop() above - so that no entry
+        ** is removed from the hint blob.  */
+        hint.n = nHint;
+      }
+    }
+
+    /* If nSeg is less that zero, then there is no level with at least
+    ** nMin segments and no hint in the %_stat table. No work to do.
+    ** Exit early in this case.  */
+    if( nSeg<0 ) break;
+
+    /* Open a cursor to iterate through the contents of the oldest nSeg 
+    ** indexes of absolute level iAbsLevel. If this cursor is opened using 
+    ** the 'hint' parameters, it is possible that there are less than nSeg
+    ** segments available in level iAbsLevel. In this case, no work is
+    ** done on iAbsLevel - fall through to the next iteration of the loop 
+    ** to start work on some other level.  */
+    memset(pWriter, 0, nAlloc);
+    pFilter->flags = FTS3_SEGMENT_REQUIRE_POS;
+
     if( rc==SQLITE_OK ){
-      sqlite3_bind_int64(pDelete, 1, pSeg->iStartBlock);
-      sqlite3_bind_int64(pDelete, 2, pSeg->iEndBlock);
-      sqlite3_step(pDelete);
-      rc = sqlite3_reset(pDelete);
+      rc = fts3IncrmergeOutputIdx(p, iAbsLevel, &iIdx);
+      assert( bUseHint==1 || bUseHint==0 );
+      if( iIdx==0 || (bUseHint && iIdx==1) ){
+        int bIgnore = 0;
+        rc = fts3SegmentIsMaxLevel(p, iAbsLevel+1, &bIgnore);
+        if( bIgnore ){
+          pFilter->flags |= FTS3_SEGMENT_IGNORE_EMPTY;
+        }
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      rc = fts3IncrmergeCsr(p, iAbsLevel, nSeg, pCsr);
+    }
+    if( SQLITE_OK==rc && pCsr->nSegment==nSeg
+     && SQLITE_OK==(rc = sqlite3Fts3SegReaderStart(p, pCsr, pFilter))
+     && SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, pCsr))
+    ){
+      if( bUseHint && iIdx>0 ){
+        const char *zKey = pCsr->zTerm;
+        int nKey = pCsr->nTerm;
+        rc = fts3IncrmergeLoad(p, iAbsLevel, iIdx-1, zKey, nKey, pWriter);
+      }else{
+        rc = fts3IncrmergeWriter(p, iAbsLevel, iIdx, pCsr, pWriter);
+      }
+
+      if( rc==SQLITE_OK && pWriter->nLeafEst ){
+        fts3LogMerge(nSeg, iAbsLevel);
+        do {
+          rc = fts3IncrmergeAppend(p, pWriter, pCsr);
+          if( rc==SQLITE_OK ) rc = sqlite3Fts3SegReaderStep(p, pCsr);
+          if( pWriter->nWork>=nRem && rc==SQLITE_ROW ) rc = SQLITE_OK;
+        }while( rc==SQLITE_ROW );
+
+        /* Update or delete the input segments */
+        if( rc==SQLITE_OK ){
+          nRem -= (1 + pWriter->nWork);
+          rc = fts3IncrmergeChomp(p, iAbsLevel, pCsr, &nSeg);
+          if( nSeg!=0 ){
+            bDirtyHint = 1;
+            fts3IncrmergeHintPush(&hint, iAbsLevel, nSeg, &rc);
+          }
+        }
+      }
+
+      if( nSeg!=0 ){
+        pWriter->nLeafData = pWriter->nLeafData * -1;
+      }
+      fts3IncrmergeRelease(p, pWriter, &rc);
+      if( nSeg==0 && pWriter->bNoLeafData==0 ){
+        fts3PromoteSegments(p, iAbsLevel+1, pWriter->nLeafData);
+      }
     }
+
+    sqlite3Fts3SegReaderFinish(pCsr);
+  }
+
+  /* Write the hint values into the %_stat table for the next incr-merger */
+  if( bDirtyHint && rc==SQLITE_OK ){
+    rc = fts3IncrmergeHintStore(p, &hint);
   }
+
+  sqlite3_free(pWriter);
+  sqlite3_free(hint.a);
   return rc;
 }
 
 /*
-** This function is used after merging multiple segments into a single large
-** segment to delete the old, now redundant, segment b-trees. Specifically,
-** it:
-** 
-**   1) Deletes all %_segments entries for the segments associated with 
-**      each of the SegReader objects in the array passed as the third 
-**      argument, and
+** Convert the text beginning at *pz into an integer and return
+** its value.  Advance *pz to point to the first character past
+** the integer.
+*/
+static int fts3Getint(const char **pz){
+  const char *z = *pz;
+  int i = 0;
+  while( (*z)>='0' && (*z)<='9' ) i = 10*i + *(z++) - '0';
+  *pz = z;
+  return i;
+}
+
+/*
+** Process statements of the form:
 **
-**   2) deletes all %_segdir entries with level iLevel, or all %_segdir
-**      entries regardless of level if (iLevel<0).
+**    INSERT INTO table(table) VALUES('merge=A,B');
 **
-** SQLITE_OK is returned if successful, otherwise an SQLite error code.
+** A and B are integers that decode to be the number of leaf pages
+** written for the merge, and the minimum number of segments on a level
+** before it will be selected for a merge, respectively.
 */
-static int fts3DeleteSegdir(
-  Fts3Table *p,                   /* Virtual table handle */
-  int iLangid,                    /* Language id */
-  int iIndex,                     /* Index for p->aIndex */
-  int iLevel,                     /* Level of %_segdir entries to delete */
-  Fts3SegReader **apSegment,      /* Array of SegReader objects */
-  int nReader                     /* Size of array apSegment */
+static int fts3DoIncrmerge(
+  Fts3Table *p,                   /* FTS3 table handle */
+  const char *zParam              /* Nul-terminated string containing "A,B" */
 ){
-  int rc = SQLITE_OK;             /* Return Code */
-  int i;                          /* Iterator variable */
-  sqlite3_stmt *pDelete = 0;      /* SQL statement to delete rows */
+  int rc;
+  int nMin = (FTS3_MERGE_COUNT / 2);
+  int nMerge = 0;
+  const char *z = zParam;
 
-  for(i=0; rc==SQLITE_OK && i<nReader; i++){
-    rc = fts3DeleteSegment(p, apSegment[i]);
-  }
-  if( rc!=SQLITE_OK ){
-    return rc;
+  /* Read the first integer value */
+  nMerge = fts3Getint(&z);
+
+  /* If the first integer value is followed by a ',',  read the second
+  ** integer value. */
+  if( z[0]==',' && z[1]!='\0' ){
+    z++;
+    nMin = fts3Getint(&z);
   }
 
-  assert( iLevel>=0 || iLevel==FTS3_SEGCURSOR_ALL );
-  if( iLevel==FTS3_SEGCURSOR_ALL ){
-    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_RANGE, &pDelete, 0);
-    if( rc==SQLITE_OK ){
-      sqlite3_bind_int64(pDelete, 1, getAbsoluteLevel(p, iLangid, iIndex, 0));
-      sqlite3_bind_int64(pDelete, 2, 
-          getAbsoluteLevel(p, iLangid, iIndex, FTS3_SEGDIR_MAXLEVEL-1)
-      );
-    }
+  if( z[0]!='\0' || nMin<2 ){
+    rc = SQLITE_ERROR;
   }else{
-    rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_LEVEL, &pDelete, 0);
+    rc = SQLITE_OK;
+    if( !p->bHasStat ){
+      assert( p->bFts4==0 );
+      sqlite3Fts3CreateStatTable(&rc, p);
+    }
     if( rc==SQLITE_OK ){
-      sqlite3_bind_int64(
-          pDelete, 1, getAbsoluteLevel(p, iLangid, iIndex, iLevel)
-      );
+      rc = sqlite3Fts3Incrmerge(p, nMerge, nMin);
     }
+    sqlite3Fts3SegmentsClose(p);
   }
-
-  if( rc==SQLITE_OK ){
-    sqlite3_step(pDelete);
-    rc = sqlite3_reset(pDelete);
-  }
-
   return rc;
 }
 
 /*
-** When this function is called, buffer *ppList (size *pnList bytes) contains 
-** a position list that may (or may not) feature multiple columns. This
-** function adjusts the pointer *ppList and the length *pnList so that they
-** identify the subset of the position list that corresponds to column iCol.
+** Process statements of the form:
 **
-** If there are no entries in the input position list for column iCol, then
-** *pnList is set to zero before returning.
+**    INSERT INTO table(table) VALUES('automerge=X');
 **
-** If parameter bZero is non-zero, then any part of the input list following
-** the end of the output list is zeroed before returning.
+** where X is an integer.  X==0 means to turn automerge off.  X!=0 means
+** turn it on.  The setting is persistent.
 */
-static void fts3ColumnFilter(
-  int iCol,                       /* Column to filter on */
-  int bZero,                      /* Zero out anything following *ppList */
-  char **ppList,                  /* IN/OUT: Pointer to position list */
-  int *pnList                     /* IN/OUT: Size of buffer *ppList in bytes */
+static int fts3DoAutoincrmerge(
+  Fts3Table *p,                   /* FTS3 table handle */
+  const char *zParam              /* Nul-terminated string containing boolean */
 ){
-  char *pList = *ppList;
-  int nList = *pnList;
-  char *pEnd = &pList[nList];
-  int iCurrent = 0;
-  char *p = pList;
-
-  assert( iCol>=0 );
-  while( 1 ){
-    char c = 0;
-    while( p<pEnd && (c | *p)&0xFE ) c = *p++ & 0x80;
-  
-    if( iCol==iCurrent ){
-      nList = (int)(p - pList);
-      break;
-    }
-
-    nList -= (int)(p - pList);
-    pList = p;
-    if( nList==0 ){
-      break;
-    }
-    p = &pList[1];
-    p += fts3GetVarint32(p, &iCurrent);
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pStmt = 0;
+  p->nAutoincrmerge = fts3Getint(&zParam);
+  if( p->nAutoincrmerge==1 || p->nAutoincrmerge>FTS3_MERGE_COUNT ){
+    p->nAutoincrmerge = 8;
   }
-
-  if( bZero && &pList[nList]!=pEnd ){
-    memset(&pList[nList], 0, pEnd - &pList[nList]);
+  if( !p->bHasStat ){
+    assert( p->bFts4==0 );
+    sqlite3Fts3CreateStatTable(&rc, p);
+    if( rc ) return rc;
   }
-  *ppList = pList;
-  *pnList = nList;
+  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pStmt, 0);
+  if( rc ) return rc;
+  sqlite3_bind_int(pStmt, 1, FTS_STAT_AUTOINCRMERGE);
+  sqlite3_bind_int(pStmt, 2, p->nAutoincrmerge);
+  sqlite3_step(pStmt);
+  rc = sqlite3_reset(pStmt);
+  return rc;
 }
 
 /*
-** Cache data in the Fts3MultiSegReader.aBuffer[] buffer (overwriting any
-** existing data). Grow the buffer if required.
-**
-** If successful, return SQLITE_OK. Otherwise, if an OOM error is encountered
-** trying to resize the buffer, return SQLITE_NOMEM.
+** Return a 64-bit checksum for the FTS index entry specified by the
+** arguments to this function.
 */
-static int fts3MsrBufferData(
-  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
-  char *pList,
-  int nList
+static u64 fts3ChecksumEntry(
+  const char *zTerm,              /* Pointer to buffer containing term */
+  int nTerm,                      /* Size of zTerm in bytes */
+  int iLangid,                    /* Language id for current row */
+  int iIndex,                     /* Index (0..Fts3Table.nIndex-1) */
+  i64 iDocid,                     /* Docid for current row. */
+  int iCol,                       /* Column number */
+  int iPos                        /* Position */
 ){
-  if( nList>pMsr->nBuffer ){
-    char *pNew;
-    pMsr->nBuffer = nList*2;
-    pNew = (char *)sqlite3_realloc(pMsr->aBuffer, pMsr->nBuffer);
-    if( !pNew ) return SQLITE_NOMEM;
-    pMsr->aBuffer = pNew;
-  }
+  int i;
+  u64 ret = (u64)iDocid;
 
-  memcpy(pMsr->aBuffer, pList, nList);
-  return SQLITE_OK;
+  ret += (ret<<3) + iLangid;
+  ret += (ret<<3) + iIndex;
+  ret += (ret<<3) + iCol;
+  ret += (ret<<3) + iPos;
+  for(i=0; i<nTerm; i++) ret += (ret<<3) + zTerm[i];
+
+  return ret;
 }
 
-SQLITE_PRIVATE int sqlite3Fts3MsrIncrNext(
-  Fts3Table *p,                   /* Virtual table handle */
-  Fts3MultiSegReader *pMsr,       /* Multi-segment-reader handle */
-  sqlite3_int64 *piDocid,         /* OUT: Docid value */
-  char **paPoslist,               /* OUT: Pointer to position list */
-  int *pnPoslist                  /* OUT: Size of position list in bytes */
+/*
+** Return a checksum of all entries in the FTS index that correspond to
+** language id iLangid. The checksum is calculated by XORing the checksums
+** of each individual entry (see fts3ChecksumEntry()) together.
+**
+** If successful, the checksum value is returned and *pRc set to SQLITE_OK.
+** Otherwise, if an error occurs, *pRc is set to an SQLite error code. The
+** return value is undefined in this case.
+*/
+static u64 fts3ChecksumIndex(
+  Fts3Table *p,                   /* FTS3 table handle */
+  int iLangid,                    /* Language id to return cksum for */
+  int iIndex,                     /* Index to cksum (0..p->nIndex-1) */
+  int *pRc                        /* OUT: Return code */
 ){
-  int nMerge = pMsr->nAdvance;
-  Fts3SegReader **apSegment = pMsr->apSegment;
-  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
-    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
-  );
-
-  if( nMerge==0 ){
-    *paPoslist = 0;
-    return SQLITE_OK;
-  }
+  Fts3SegFilter filter;
+  Fts3MultiSegReader csr;
+  int rc;
+  u64 cksum = 0;
 
-  while( 1 ){
-    Fts3SegReader *pSeg;
-    pSeg = pMsr->apSegment[0];
+  assert( *pRc==SQLITE_OK );
 
-    if( pSeg->pOffsetList==0 ){
-      *paPoslist = 0;
-      break;
-    }else{
-      int rc;
-      char *pList;
-      int nList;
-      int j;
-      sqlite3_int64 iDocid = apSegment[0]->iDocid;
+  memset(&filter, 0, sizeof(filter));
+  memset(&csr, 0, sizeof(csr));
+  filter.flags =  FTS3_SEGMENT_REQUIRE_POS|FTS3_SEGMENT_IGNORE_EMPTY;
+  filter.flags |= FTS3_SEGMENT_SCAN;
 
-      rc = fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
-      j = 1;
-      while( rc==SQLITE_OK 
-        && j<nMerge
-        && apSegment[j]->pOffsetList
-        && apSegment[j]->iDocid==iDocid
-      ){
-        rc = fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
-        j++;
-      }
-      if( rc!=SQLITE_OK ) return rc;
-      fts3SegReaderSort(pMsr->apSegment, nMerge, j, xCmp);
+  rc = sqlite3Fts3SegReaderCursor(
+      p, iLangid, iIndex, FTS3_SEGCURSOR_ALL, 0, 0, 0, 1,&csr
+  );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
+  }
 
-      if( nList>0 && fts3SegReaderIsPending(apSegment[0]) ){
-        rc = fts3MsrBufferData(pMsr, pList, nList+1);
-        if( rc!=SQLITE_OK ) return rc;
-        assert( (pMsr->aBuffer[nList] & 0xFE)==0x00 );
-        pList = pMsr->aBuffer;
-      }
+  if( rc==SQLITE_OK ){
+    while( SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, &csr)) ){
+      char *pCsr = csr.aDoclist;
+      char *pEnd = &pCsr[csr.nDoclist];
 
-      if( pMsr->iColFilter>=0 ){
-        fts3ColumnFilter(pMsr->iColFilter, 1, &pList, &nList);
-      }
+      i64 iDocid = 0;
+      i64 iCol = 0;
+      i64 iPos = 0;
 
-      if( nList>0 ){
-        *paPoslist = pList;
-        *piDocid = iDocid;
-        *pnPoslist = nList;
-        break;
+      pCsr += sqlite3Fts3GetVarint(pCsr, &iDocid);
+      while( pCsr<pEnd ){
+        i64 iVal = 0;
+        pCsr += sqlite3Fts3GetVarint(pCsr, &iVal);
+        if( pCsr<pEnd ){
+          if( iVal==0 || iVal==1 ){
+            iCol = 0;
+            iPos = 0;
+            if( iVal ){
+              pCsr += sqlite3Fts3GetVarint(pCsr, &iCol);
+            }else{
+              pCsr += sqlite3Fts3GetVarint(pCsr, &iVal);
+              iDocid += iVal;
+            }
+          }else{
+            iPos += (iVal - 2);
+            cksum = cksum ^ fts3ChecksumEntry(
+                csr.zTerm, csr.nTerm, iLangid, iIndex, iDocid,
+                (int)iCol, (int)iPos
+            );
+          }
+        }
       }
     }
   }
+  sqlite3Fts3SegReaderFinish(&csr);
 
-  return SQLITE_OK;
+  *pRc = rc;
+  return cksum;
 }
 
-static int fts3SegReaderStart(
-  Fts3Table *p,                   /* Virtual table handle */
-  Fts3MultiSegReader *pCsr,       /* Cursor object */
-  const char *zTerm,              /* Term searched for (or NULL) */
-  int nTerm                       /* Length of zTerm in bytes */
-){
-  int i;
-  int nSeg = pCsr->nSegment;
-
-  /* If the Fts3SegFilter defines a specific term (or term prefix) to search 
-  ** for, then advance each segment iterator until it points to a term of
-  ** equal or greater value than the specified term. This prevents many
-  ** unnecessary merge/sort operations for the case where single segment
-  ** b-tree leaf nodes contain more than one term.
-  */
-  for(i=0; pCsr->bRestart==0 && i<pCsr->nSegment; i++){
-    int res = 0;
-    Fts3SegReader *pSeg = pCsr->apSegment[i];
-    do {
-      int rc = fts3SegReaderNext(p, pSeg, 0);
-      if( rc!=SQLITE_OK ) return rc;
-    }while( zTerm && (res = fts3SegReaderTermCmp(pSeg, zTerm, nTerm))<0 );
+/*
+** Check if the contents of the FTS index match the current contents of the
+** content table. If no error occurs and the contents do match, set *pbOk
+** to true and return SQLITE_OK. Or if the contents do not match, set *pbOk
+** to false before returning.
+**
+** If an error occurs (e.g. an OOM or IO error), return an SQLite error 
+** code. The final value of *pbOk is undefined in this case.
+*/
+static int fts3IntegrityCheck(Fts3Table *p, int *pbOk){
+  int rc = SQLITE_OK;             /* Return code */
+  u64 cksum1 = 0;                 /* Checksum based on FTS index contents */
+  u64 cksum2 = 0;                 /* Checksum based on %_content contents */
+  sqlite3_stmt *pAllLangid = 0;   /* Statement to return all language-ids */
 
-    if( pSeg->bLookup && res!=0 ){
-      fts3SegReaderSetEof(pSeg);
+  /* This block calculates the checksum according to the FTS index. */
+  rc = fts3SqlStmt(p, SQL_SELECT_ALL_LANGID, &pAllLangid, 0);
+  if( rc==SQLITE_OK ){
+    int rc2;
+    sqlite3_bind_int(pAllLangid, 1, p->iPrevLangid);
+    sqlite3_bind_int(pAllLangid, 2, p->nIndex);
+    while( rc==SQLITE_OK && sqlite3_step(pAllLangid)==SQLITE_ROW ){
+      int iLangid = sqlite3_column_int(pAllLangid, 0);
+      int i;
+      for(i=0; i<p->nIndex; i++){
+        cksum1 = cksum1 ^ fts3ChecksumIndex(p, iLangid, i, &rc);
+      }
     }
+    rc2 = sqlite3_reset(pAllLangid);
+    if( rc==SQLITE_OK ) rc = rc2;
   }
-  fts3SegReaderSort(pCsr->apSegment, nSeg, nSeg, fts3SegReaderCmp);
-
-  return SQLITE_OK;
-}
 
-SQLITE_PRIVATE int sqlite3Fts3SegReaderStart(
-  Fts3Table *p,                   /* Virtual table handle */
-  Fts3MultiSegReader *pCsr,       /* Cursor object */
-  Fts3SegFilter *pFilter          /* Restrictions on range of iteration */
-){
-  pCsr->pFilter = pFilter;
-  return fts3SegReaderStart(p, pCsr, pFilter->zTerm, pFilter->nTerm);
-}
+  /* This block calculates the checksum according to the %_content table */
+  if( rc==SQLITE_OK ){
+    sqlite3_tokenizer_module const *pModule = p->pTokenizer->pModule;
+    sqlite3_stmt *pStmt = 0;
+    char *zSql;
+   
+    zSql = sqlite3_mprintf("SELECT %s" , p->zReadExprlist);
+    if( !zSql ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+      sqlite3_free(zSql);
+    }
 
-SQLITE_PRIVATE int sqlite3Fts3MsrIncrStart(
-  Fts3Table *p,                   /* Virtual table handle */
-  Fts3MultiSegReader *pCsr,       /* Cursor object */
-  int iCol,                       /* Column to match on. */
-  const char *zTerm,              /* Term to iterate through a doclist for */
-  int nTerm                       /* Number of bytes in zTerm */
-){
-  int i;
-  int rc;
-  int nSegment = pCsr->nSegment;
-  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
-    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
-  );
+    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      i64 iDocid = sqlite3_column_int64(pStmt, 0);
+      int iLang = langidFromSelect(p, pStmt);
+      int iCol;
 
-  assert( pCsr->pFilter==0 );
-  assert( zTerm && nTerm>0 );
+      for(iCol=0; rc==SQLITE_OK && iCol<p->nColumn; iCol++){
+        if( p->abNotindexed[iCol]==0 ){
+          const char *zText = (const char *)sqlite3_column_text(pStmt, iCol+1);
+          int nText = sqlite3_column_bytes(pStmt, iCol+1);
+          sqlite3_tokenizer_cursor *pT = 0;
 
-  /* Advance each segment iterator until it points to the term zTerm/nTerm. */
-  rc = fts3SegReaderStart(p, pCsr, zTerm, nTerm);
-  if( rc!=SQLITE_OK ) return rc;
+          rc = sqlite3Fts3OpenTokenizer(p->pTokenizer, iLang, zText, nText,&pT);
+          while( rc==SQLITE_OK ){
+            char const *zToken;       /* Buffer containing token */
+            int nToken = 0;           /* Number of bytes in token */
+            int iDum1 = 0, iDum2 = 0; /* Dummy variables */
+            int iPos = 0;             /* Position of token in zText */
 
-  /* Determine how many of the segments actually point to zTerm/nTerm. */
-  for(i=0; i<nSegment; i++){
-    Fts3SegReader *pSeg = pCsr->apSegment[i];
-    if( !pSeg->aNode || fts3SegReaderTermCmp(pSeg, zTerm, nTerm) ){
-      break;
+            rc = pModule->xNext(pT, &zToken, &nToken, &iDum1, &iDum2, &iPos);
+            if( rc==SQLITE_OK ){
+              int i;
+              cksum2 = cksum2 ^ fts3ChecksumEntry(
+                  zToken, nToken, iLang, 0, iDocid, iCol, iPos
+              );
+              for(i=1; i<p->nIndex; i++){
+                if( p->aIndex[i].nPrefix<=nToken ){
+                  cksum2 = cksum2 ^ fts3ChecksumEntry(
+                      zToken, p->aIndex[i].nPrefix, iLang, i, iDocid, iCol, iPos
+                  );
+                }
+              }
+            }
+          }
+          if( pT ) pModule->xClose(pT);
+          if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+        }
+      }
     }
-  }
-  pCsr->nAdvance = i;
 
-  /* Advance each of the segments to point to the first docid. */
-  for(i=0; i<pCsr->nAdvance; i++){
-    rc = fts3SegReaderFirstDocid(p, pCsr->apSegment[i]);
-    if( rc!=SQLITE_OK ) return rc;
+    sqlite3_finalize(pStmt);
   }
-  fts3SegReaderSort(pCsr->apSegment, i, i, xCmp);
 
-  assert( iCol<0 || iCol<p->nColumn );
-  pCsr->iColFilter = iCol;
-
-  return SQLITE_OK;
+  *pbOk = (cksum1==cksum2);
+  return rc;
 }
 
 /*
-** This function is called on a MultiSegReader that has been started using
-** sqlite3Fts3MsrIncrStart(). One or more calls to MsrIncrNext() may also
-** have been made. Calling this function puts the MultiSegReader in such
-** a state that if the next two calls are:
+** Run the integrity-check. If no error occurs and the current contents of
+** the FTS index are correct, return SQLITE_OK. Or, if the contents of the
+** FTS index are incorrect, return SQLITE_CORRUPT_VTAB.
 **
-**   sqlite3Fts3SegReaderStart()
-**   sqlite3Fts3SegReaderStep()
+** Or, if an error (e.g. an OOM or IO error) occurs, return an SQLite 
+** error code.
 **
-** then the entire doclist for the term is available in 
-** MultiSegReader.aDoclist/nDoclist.
+** The integrity-check works as follows. For each token and indexed token
+** prefix in the document set, a 64-bit checksum is calculated (by code
+** in fts3ChecksumEntry()) based on the following:
+**
+**     + The index number (0 for the main index, 1 for the first prefix
+**       index etc.),
+**     + The token (or token prefix) text itself, 
+**     + The language-id of the row it appears in,
+**     + The docid of the row it appears in,
+**     + The column it appears in, and
+**     + The tokens position within that column.
+**
+** The checksums for all entries in the index are XORed together to create
+** a single checksum for the entire index.
+**
+** The integrity-check code calculates the same checksum in two ways:
+**
+**     1. By scanning the contents of the FTS index, and 
+**     2. By scanning and tokenizing the content table.
+**
+** If the two checksums are identical, the integrity-check is deemed to have
+** passed.
 */
-SQLITE_PRIVATE int sqlite3Fts3MsrIncrRestart(Fts3MultiSegReader *pCsr){
-  int i;                          /* Used to iterate through segment-readers */
+static int fts3DoIntegrityCheck(
+  Fts3Table *p                    /* FTS3 table handle */
+){
+  int rc;
+  int bOk = 0;
+  rc = fts3IntegrityCheck(p, &bOk);
+  if( rc==SQLITE_OK && bOk==0 ) rc = FTS_CORRUPT_VTAB;
+  return rc;
+}
 
-  assert( pCsr->zTerm==0 );
-  assert( pCsr->nTerm==0 );
-  assert( pCsr->aDoclist==0 );
-  assert( pCsr->nDoclist==0 );
+/*
+** Handle a 'special' INSERT of the form:
+**
+**   "INSERT INTO tbl(tbl) VALUES(<expr>)"
+**
+** Argument pVal contains the result of <expr>. Currently the only 
+** meaningful value to insert is the text 'optimize'.
+*/
+static int fts3SpecialInsert(Fts3Table *p, sqlite3_value *pVal){
+  int rc;                         /* Return Code */
+  const char *zVal = (const char *)sqlite3_value_text(pVal);
+  int nVal = sqlite3_value_bytes(pVal);
 
-  pCsr->nAdvance = 0;
-  pCsr->bRestart = 1;
-  for(i=0; i<pCsr->nSegment; i++){
-    pCsr->apSegment[i]->pOffsetList = 0;
-    pCsr->apSegment[i]->nOffsetList = 0;
-    pCsr->apSegment[i]->iDocid = 0;
+  if( !zVal ){
+    return SQLITE_NOMEM;
+  }else if( nVal==8 && 0==sqlite3_strnicmp(zVal, "optimize", 8) ){
+    rc = fts3DoOptimize(p, 0);
+  }else if( nVal==7 && 0==sqlite3_strnicmp(zVal, "rebuild", 7) ){
+    rc = fts3DoRebuild(p);
+  }else if( nVal==15 && 0==sqlite3_strnicmp(zVal, "integrity-check", 15) ){
+    rc = fts3DoIntegrityCheck(p);
+  }else if( nVal>6 && 0==sqlite3_strnicmp(zVal, "merge=", 6) ){
+    rc = fts3DoIncrmerge(p, &zVal[6]);
+  }else if( nVal>10 && 0==sqlite3_strnicmp(zVal, "automerge=", 10) ){
+    rc = fts3DoAutoincrmerge(p, &zVal[10]);
+#ifdef SQLITE_TEST
+  }else if( nVal>9 && 0==sqlite3_strnicmp(zVal, "nodesize=", 9) ){
+    p->nNodeSize = atoi(&zVal[9]);
+    rc = SQLITE_OK;
+  }else if( nVal>11 && 0==sqlite3_strnicmp(zVal, "maxpending=", 9) ){
+    p->nMaxPendingData = atoi(&zVal[11]);
+    rc = SQLITE_OK;
+  }else if( nVal>21 && 0==sqlite3_strnicmp(zVal, "test-no-incr-doclist=", 21) ){
+    p->bNoIncrDoclist = atoi(&zVal[21]);
+    rc = SQLITE_OK;
+#endif
+  }else{
+    rc = SQLITE_ERROR;
   }
 
-  return SQLITE_OK;
+  return rc;
 }
 
+#ifndef SQLITE_DISABLE_FTS4_DEFERRED
+/*
+** Delete all cached deferred doclists. Deferred doclists are cached
+** (allocated) by the sqlite3Fts3CacheDeferredDoclists() function.
+*/
+SQLITE_PRIVATE void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *pCsr){
+  Fts3DeferredToken *pDef;
+  for(pDef=pCsr->pDeferred; pDef; pDef=pDef->pNext){
+    fts3PendingListDelete(pDef->pList);
+    pDef->pList = 0;
+  }
+}
 
-SQLITE_PRIVATE int sqlite3Fts3SegReaderStep(
-  Fts3Table *p,                   /* Virtual table handle */
-  Fts3MultiSegReader *pCsr        /* Cursor object */
-){
-  int rc = SQLITE_OK;
-
-  int isIgnoreEmpty =  (pCsr->pFilter->flags & FTS3_SEGMENT_IGNORE_EMPTY);
-  int isRequirePos =   (pCsr->pFilter->flags & FTS3_SEGMENT_REQUIRE_POS);
-  int isColFilter =    (pCsr->pFilter->flags & FTS3_SEGMENT_COLUMN_FILTER);
-  int isPrefix =       (pCsr->pFilter->flags & FTS3_SEGMENT_PREFIX);
-  int isScan =         (pCsr->pFilter->flags & FTS3_SEGMENT_SCAN);
-  int isFirst =        (pCsr->pFilter->flags & FTS3_SEGMENT_FIRST);
-
-  Fts3SegReader **apSegment = pCsr->apSegment;
-  int nSegment = pCsr->nSegment;
-  Fts3SegFilter *pFilter = pCsr->pFilter;
-  int (*xCmp)(Fts3SegReader *, Fts3SegReader *) = (
-    p->bDescIdx ? fts3SegReaderDoclistCmpRev : fts3SegReaderDoclistCmp
-  );
-
-  if( pCsr->nSegment==0 ) return SQLITE_OK;
-
-  do {
-    int nMerge;
-    int i;
-  
-    /* Advance the first pCsr->nAdvance entries in the apSegment[] array
-    ** forward. Then sort the list in order of current term again.  
-    */
-    for(i=0; i<pCsr->nAdvance; i++){
-      Fts3SegReader *pSeg = apSegment[i];
-      if( pSeg->bLookup ){
-        fts3SegReaderSetEof(pSeg);
-      }else{
-        rc = fts3SegReaderNext(p, pSeg, 0);
-      }
-      if( rc!=SQLITE_OK ) return rc;
-    }
-    fts3SegReaderSort(apSegment, nSegment, pCsr->nAdvance, fts3SegReaderCmp);
-    pCsr->nAdvance = 0;
-
-    /* If all the seg-readers are at EOF, we're finished. return SQLITE_OK. */
-    assert( rc==SQLITE_OK );
-    if( apSegment[0]->aNode==0 ) break;
-
-    pCsr->nTerm = apSegment[0]->nTerm;
-    pCsr->zTerm = apSegment[0]->zTerm;
-
-    /* If this is a prefix-search, and if the term that apSegment[0] points
-    ** to does not share a suffix with pFilter->zTerm/nTerm, then all 
-    ** required callbacks have been made. In this case exit early.
-    **
-    ** Similarly, if this is a search for an exact match, and the first term
-    ** of segment apSegment[0] is not a match, exit early.
-    */
-    if( pFilter->zTerm && !isScan ){
-      if( pCsr->nTerm<pFilter->nTerm 
-       || (!isPrefix && pCsr->nTerm>pFilter->nTerm)
-       || memcmp(pCsr->zTerm, pFilter->zTerm, pFilter->nTerm) 
-      ){
-        break;
-      }
-    }
-
-    nMerge = 1;
-    while( nMerge<nSegment 
-        && apSegment[nMerge]->aNode
-        && apSegment[nMerge]->nTerm==pCsr->nTerm 
-        && 0==memcmp(pCsr->zTerm, apSegment[nMerge]->zTerm, pCsr->nTerm)
-    ){
-      nMerge++;
-    }
-
-    assert( isIgnoreEmpty || (isRequirePos && !isColFilter) );
-    if( nMerge==1 
-     && !isIgnoreEmpty 
-     && !isFirst 
-     && (p->bDescIdx==0 || fts3SegReaderIsPending(apSegment[0])==0)
-    ){
-      pCsr->nDoclist = apSegment[0]->nDoclist;
-      if( fts3SegReaderIsPending(apSegment[0]) ){
-        rc = fts3MsrBufferData(pCsr, apSegment[0]->aDoclist, pCsr->nDoclist);
-        pCsr->aDoclist = pCsr->aBuffer;
-      }else{
-        pCsr->aDoclist = apSegment[0]->aDoclist;
-      }
-      if( rc==SQLITE_OK ) rc = SQLITE_ROW;
-    }else{
-      int nDoclist = 0;           /* Size of doclist */
-      sqlite3_int64 iPrev = 0;    /* Previous docid stored in doclist */
-
-      /* The current term of the first nMerge entries in the array
-      ** of Fts3SegReader objects is the same. The doclists must be merged
-      ** and a single term returned with the merged doclist.
-      */
-      for(i=0; i<nMerge; i++){
-        fts3SegReaderFirstDocid(p, apSegment[i]);
-      }
-      fts3SegReaderSort(apSegment, nMerge, nMerge, xCmp);
-      while( apSegment[0]->pOffsetList ){
-        int j;                    /* Number of segments that share a docid */
-        char *pList = 0;
-        int nList = 0;
-        int nByte;
-        sqlite3_int64 iDocid = apSegment[0]->iDocid;
-        fts3SegReaderNextDocid(p, apSegment[0], &pList, &nList);
-        j = 1;
-        while( j<nMerge
-            && apSegment[j]->pOffsetList
-            && apSegment[j]->iDocid==iDocid
-        ){
-          fts3SegReaderNextDocid(p, apSegment[j], 0, 0);
-          j++;
-        }
-
-        if( isColFilter ){
-          fts3ColumnFilter(pFilter->iCol, 0, &pList, &nList);
-        }
-
-        if( !isIgnoreEmpty || nList>0 ){
+/*
+** Free all entries in the pCsr->pDeffered list. Entries are added to 
+** this list using sqlite3Fts3DeferToken().
+*/
+SQLITE_PRIVATE void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *pCsr){
+  Fts3DeferredToken *pDef;
+  Fts3DeferredToken *pNext;
+  for(pDef=pCsr->pDeferred; pDef; pDef=pNext){
+    pNext = pDef->pNext;
+    fts3PendingListDelete(pDef->pList);
+    sqlite3_free(pDef);
+  }
+  pCsr->pDeferred = 0;
+}
 
-          /* Calculate the 'docid' delta value to write into the merged 
-          ** doclist. */
-          sqlite3_int64 iDelta;
-          if( p->bDescIdx && nDoclist>0 ){
-            iDelta = iPrev - iDocid;
-          }else{
-            iDelta = iDocid - iPrev;
-          }
-          assert( iDelta>0 || (nDoclist==0 && iDelta==iDocid) );
-          assert( nDoclist>0 || iDelta==iDocid );
+/*
+** Generate deferred-doclists for all tokens in the pCsr->pDeferred list
+** based on the row that pCsr currently points to.
+**
+** A deferred-doclist is like any other doclist with position information
+** included, except that it only contains entries for a single row of the
+** table, not for all rows.
+*/
+SQLITE_PRIVATE int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *pCsr){
+  int rc = SQLITE_OK;             /* Return code */
+  if( pCsr->pDeferred ){
+    int i;                        /* Used to iterate through table columns */
+    sqlite3_int64 iDocid;         /* Docid of the row pCsr points to */
+    Fts3DeferredToken *pDef;      /* Used to iterate through deferred tokens */
+  
+    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
+    sqlite3_tokenizer *pT = p->pTokenizer;
+    sqlite3_tokenizer_module const *pModule = pT->pModule;
+   
+    assert( pCsr->isRequireSeek==0 );
+    iDocid = sqlite3_column_int64(pCsr->pStmt, 0);
+  
+    for(i=0; i<p->nColumn && rc==SQLITE_OK; i++){
+      if( p->abNotindexed[i]==0 ){
+        const char *zText = (const char *)sqlite3_column_text(pCsr->pStmt, i+1);
+        sqlite3_tokenizer_cursor *pTC = 0;
 
-          nByte = sqlite3Fts3VarintLen(iDelta) + (isRequirePos?nList+1:0);
-          if( nDoclist+nByte>pCsr->nBuffer ){
-            char *aNew;
-            pCsr->nBuffer = (nDoclist+nByte)*2;
-            aNew = sqlite3_realloc(pCsr->aBuffer, pCsr->nBuffer);
-            if( !aNew ){
-              return SQLITE_NOMEM;
-            }
-            pCsr->aBuffer = aNew;
-          }
+        rc = sqlite3Fts3OpenTokenizer(pT, pCsr->iLangid, zText, -1, &pTC);
+        while( rc==SQLITE_OK ){
+          char const *zToken;       /* Buffer containing token */
+          int nToken = 0;           /* Number of bytes in token */
+          int iDum1 = 0, iDum2 = 0; /* Dummy variables */
+          int iPos = 0;             /* Position of token in zText */
 
-          if( isFirst ){
-            char *a = &pCsr->aBuffer[nDoclist];
-            int nWrite;
-           
-            nWrite = sqlite3Fts3FirstFilter(iDelta, pList, nList, a);
-            if( nWrite ){
-              iPrev = iDocid;
-              nDoclist += nWrite;
-            }
-          }else{
-            nDoclist += sqlite3Fts3PutVarint(&pCsr->aBuffer[nDoclist], iDelta);
-            iPrev = iDocid;
-            if( isRequirePos ){
-              memcpy(&pCsr->aBuffer[nDoclist], pList, nList);
-              nDoclist += nList;
-              pCsr->aBuffer[nDoclist++] = '\0';
+          rc = pModule->xNext(pTC, &zToken, &nToken, &iDum1, &iDum2, &iPos);
+          for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
+            Fts3PhraseToken *pPT = pDef->pToken;
+            if( (pDef->iCol>=p->nColumn || pDef->iCol==i)
+                && (pPT->bFirst==0 || iPos==0)
+                && (pPT->n==nToken || (pPT->isPrefix && pPT->n<nToken))
+                && (0==memcmp(zToken, pPT->z, pPT->n))
+              ){
+              fts3PendingListAppend(&pDef->pList, iDocid, i, iPos, &rc);
             }
           }
         }
-
-        fts3SegReaderSort(apSegment, nMerge, j, xCmp);
+        if( pTC ) pModule->xClose(pTC);
+        if( rc==SQLITE_DONE ) rc = SQLITE_OK;
       }
-      if( nDoclist>0 ){
-        pCsr->aDoclist = pCsr->aBuffer;
-        pCsr->nDoclist = nDoclist;
-        rc = SQLITE_ROW;
+    }
+
+    for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
+      if( pDef->pList ){
+        rc = fts3PendingListAppendVarint(&pDef->pList, 0);
       }
     }
-    pCsr->nAdvance = nMerge;
-  }while( rc==SQLITE_OK );
+  }
 
   return rc;
 }
 
-
-SQLITE_PRIVATE void sqlite3Fts3SegReaderFinish(
-  Fts3MultiSegReader *pCsr       /* Cursor object */
+SQLITE_PRIVATE int sqlite3Fts3DeferredTokenList(
+  Fts3DeferredToken *p, 
+  char **ppData, 
+  int *pnData
 ){
-  if( pCsr ){
-    int i;
-    for(i=0; i<pCsr->nSegment; i++){
-      sqlite3Fts3SegReaderFree(pCsr->apSegment[i]);
-    }
-    sqlite3_free(pCsr->apSegment);
-    sqlite3_free(pCsr->aBuffer);
+  char *pRet;
+  int nSkip;
+  sqlite3_int64 dummy;
 
-    pCsr->nSegment = 0;
-    pCsr->apSegment = 0;
-    pCsr->aBuffer = 0;
+  *ppData = 0;
+  *pnData = 0;
+
+  if( p->pList==0 ){
+    return SQLITE_OK;
   }
+
+  pRet = (char *)sqlite3_malloc(p->pList->nData);
+  if( !pRet ) return SQLITE_NOMEM;
+
+  nSkip = sqlite3Fts3GetVarint(p->pList->aData, &dummy);
+  *pnData = p->pList->nData - nSkip;
+  *ppData = pRet;
+  
+  memcpy(pRet, &p->pList->aData[nSkip], *pnData);
+  return SQLITE_OK;
 }
 
 /*
-** Decode the "end_block" field, selected by column iCol of the SELECT 
-** statement passed as the first argument. 
-**
-** The "end_block" field may contain either an integer, or a text field
-** containing the text representation of two non-negative integers separated 
-** by one or more space (0x20) characters. In the first case, set *piEndBlock 
-** to the integer value and *pnByte to zero before returning. In the second, 
-** set *piEndBlock to the first value and *pnByte to the second.
+** Add an entry for token pToken to the pCsr->pDeferred list.
 */
-static void fts3ReadEndBlockField(
-  sqlite3_stmt *pStmt, 
-  int iCol, 
-  i64 *piEndBlock,
-  i64 *pnByte
+SQLITE_PRIVATE int sqlite3Fts3DeferToken(
+  Fts3Cursor *pCsr,               /* Fts3 table cursor */
+  Fts3PhraseToken *pToken,        /* Token to defer */
+  int iCol                        /* Column that token must appear in (or -1) */
 ){
-  const unsigned char *zText = sqlite3_column_text(pStmt, iCol);
-  if( zText ){
-    int i;
-    int iMul = 1;
-    i64 iVal = 0;
-    for(i=0; zText[i]>='0' && zText[i]<='9'; i++){
-      iVal = iVal*10 + (zText[i] - '0');
-    }
-    *piEndBlock = iVal;
-    while( zText[i]==' ' ) i++;
-    iVal = 0;
-    if( zText[i]=='-' ){
-      i++;
-      iMul = -1;
-    }
-    for(/* no-op */; zText[i]>='0' && zText[i]<='9'; i++){
-      iVal = iVal*10 + (zText[i] - '0');
-    }
-    *pnByte = (iVal * (i64)iMul);
+  Fts3DeferredToken *pDeferred;
+  pDeferred = sqlite3_malloc(sizeof(*pDeferred));
+  if( !pDeferred ){
+    return SQLITE_NOMEM;
   }
-}
+  memset(pDeferred, 0, sizeof(*pDeferred));
+  pDeferred->pToken = pToken;
+  pDeferred->pNext = pCsr->pDeferred; 
+  pDeferred->iCol = iCol;
+  pCsr->pDeferred = pDeferred;
+
+  assert( pToken->pDeferred==0 );
+  pToken->pDeferred = pDeferred;
 
+  return SQLITE_OK;
+}
+#endif
 
 /*
-** A segment of size nByte bytes has just been written to absolute level
-** iAbsLevel. Promote any segments that should be promoted as a result.
+** SQLite value pRowid contains the rowid of a row that may or may not be
+** present in the FTS3 table. If it is, delete it and adjust the contents
+** of subsiduary data structures accordingly.
 */
-static int fts3PromoteSegments(
-  Fts3Table *p,                   /* FTS table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level just updated */
-  sqlite3_int64 nByte             /* Size of new segment at iAbsLevel */
+static int fts3DeleteByRowid(
+  Fts3Table *p, 
+  sqlite3_value *pRowid, 
+  int *pnChng,                    /* IN/OUT: Decrement if row is deleted */
+  u32 *aSzDel
 ){
-  int rc = SQLITE_OK;
-  sqlite3_stmt *pRange;
-
-  rc = fts3SqlStmt(p, SQL_SELECT_LEVEL_RANGE2, &pRange, 0);
-
-  if( rc==SQLITE_OK ){
-    int bOk = 0;
-    i64 iLast = (iAbsLevel/FTS3_SEGDIR_MAXLEVEL + 1) * FTS3_SEGDIR_MAXLEVEL - 1;
-    i64 nLimit = (nByte*3)/2;
-
-    /* Loop through all entries in the %_segdir table corresponding to 
-    ** segments in this index on levels greater than iAbsLevel. If there is
-    ** at least one such segment, and it is possible to determine that all 
-    ** such segments are smaller than nLimit bytes in size, they will be 
-    ** promoted to level iAbsLevel.  */
-    sqlite3_bind_int64(pRange, 1, iAbsLevel+1);
-    sqlite3_bind_int64(pRange, 2, iLast);
-    while( SQLITE_ROW==sqlite3_step(pRange) ){
-      i64 nSize = 0, dummy;
-      fts3ReadEndBlockField(pRange, 2, &dummy, &nSize);
-      if( nSize<=0 || nSize>nLimit ){
-        /* If nSize==0, then the %_segdir.end_block field does not not 
-        ** contain a size value. This happens if it was written by an
-        ** old version of FTS. In this case it is not possible to determine
-        ** the size of the segment, and so segment promotion does not
-        ** take place.  */
-        bOk = 0;
-        break;
-      }
-      bOk = 1;
-    }
-    rc = sqlite3_reset(pRange);
-
-    if( bOk ){
-      int iIdx = 0;
-      sqlite3_stmt *pUpdate1 = 0;
-      sqlite3_stmt *pUpdate2 = 0;
-
-      if( rc==SQLITE_OK ){
-        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL_IDX, &pUpdate1, 0);
-      }
-      if( rc==SQLITE_OK ){
-        rc = fts3SqlStmt(p, SQL_UPDATE_LEVEL, &pUpdate2, 0);
-      }
-
-      if( rc==SQLITE_OK ){
+  int rc = SQLITE_OK;             /* Return code */
+  int bFound = 0;                 /* True if *pRowid really is in the table */
 
-        /* Loop through all %_segdir entries for segments in this index with
-        ** levels equal to or greater than iAbsLevel. As each entry is visited,
-        ** updated it to set (level = -1) and (idx = N), where N is 0 for the
-        ** oldest segment in the range, 1 for the next oldest, and so on.
-        **
-        ** In other words, move all segments being promoted to level -1,
-        ** setting the "idx" fields as appropriate to keep them in the same
-        ** order. The contents of level -1 (which is never used, except
-        ** transiently here), will be moved back to level iAbsLevel below.  */
-        sqlite3_bind_int64(pRange, 1, iAbsLevel);
-        while( SQLITE_ROW==sqlite3_step(pRange) ){
-          sqlite3_bind_int(pUpdate1, 1, iIdx++);
-          sqlite3_bind_int(pUpdate1, 2, sqlite3_column_int(pRange, 0));
-          sqlite3_bind_int(pUpdate1, 3, sqlite3_column_int(pRange, 1));
-          sqlite3_step(pUpdate1);
-          rc = sqlite3_reset(pUpdate1);
-          if( rc!=SQLITE_OK ){
-            sqlite3_reset(pRange);
-            break;
-          }
+  fts3DeleteTerms(&rc, p, pRowid, aSzDel, &bFound);
+  if( bFound && rc==SQLITE_OK ){
+    int isEmpty = 0;              /* Deleting *pRowid leaves the table empty */
+    rc = fts3IsEmpty(p, pRowid, &isEmpty);
+    if( rc==SQLITE_OK ){
+      if( isEmpty ){
+        /* Deleting this row means the whole table is empty. In this case
+        ** delete the contents of all three tables and throw away any
+        ** data in the pendingTerms hash table.  */
+        rc = fts3DeleteAll(p, 1);
+        *pnChng = 0;
+        memset(aSzDel, 0, sizeof(u32) * (p->nColumn+1) * 2);
+      }else{
+        *pnChng = *pnChng - 1;
+        if( p->zContentTbl==0 ){
+          fts3SqlExec(&rc, p, SQL_DELETE_CONTENT, &pRowid);
+        }
+        if( p->bHasDocsize ){
+          fts3SqlExec(&rc, p, SQL_DELETE_DOCSIZE, &pRowid);
         }
-      }
-      if( rc==SQLITE_OK ){
-        rc = sqlite3_reset(pRange);
-      }
-
-      /* Move level -1 to level iAbsLevel */
-      if( rc==SQLITE_OK ){
-        sqlite3_bind_int64(pUpdate2, 1, iAbsLevel);
-        sqlite3_step(pUpdate2);
-        rc = sqlite3_reset(pUpdate2);
       }
     }
   }
 
-
   return rc;
 }
 
 /*
-** Merge all level iLevel segments in the database into a single 
-** iLevel+1 segment. Or, if iLevel<0, merge all segments into a
-** single segment with a level equal to the numerically largest level 
-** currently present in the database.
+** This function does the work for the xUpdate method of FTS3 virtual
+** tables. The schema of the virtual table being:
 **
-** If this function is called with iLevel<0, but there is only one
-** segment in the database, SQLITE_DONE is returned immediately. 
-** Otherwise, if successful, SQLITE_OK is returned. If an error occurs, 
-** an SQLite error code is returned.
+**     CREATE TABLE <table name>( 
+**       <user columns>,
+**       <table name> HIDDEN, 
+**       docid HIDDEN, 
+**       <langid> HIDDEN
+**     );
+**
+** 
 */
-static int fts3SegmentMerge(
-  Fts3Table *p, 
-  int iLangid,                    /* Language id to merge */
-  int iIndex,                     /* Index in p->aIndex[] to merge */
-  int iLevel                      /* Level to merge */
+SQLITE_PRIVATE int sqlite3Fts3UpdateMethod(
+  sqlite3_vtab *pVtab,            /* FTS3 vtab object */
+  int nArg,                       /* Size of argument array */
+  sqlite3_value **apVal,          /* Array of arguments */
+  sqlite_int64 *pRowid            /* OUT: The affected (or effected) rowid */
 ){
-  int rc;                         /* Return code */
-  int iIdx = 0;                   /* Index of new segment */
-  sqlite3_int64 iNewLevel = 0;    /* Level/index to create new segment at */
-  SegmentWriter *pWriter = 0;     /* Used to write the new, merged, segment */
-  Fts3SegFilter filter;           /* Segment term filter condition */
-  Fts3MultiSegReader csr;         /* Cursor to iterate through level(s) */
-  int bIgnoreEmpty = 0;           /* True to ignore empty segments */
-  i64 iMaxLevel = 0;              /* Max level number for this index/langid */
+  Fts3Table *p = (Fts3Table *)pVtab;
+  int rc = SQLITE_OK;             /* Return Code */
+  int isRemove = 0;               /* True for an UPDATE or DELETE */
+  u32 *aSzIns = 0;                /* Sizes of inserted documents */
+  u32 *aSzDel = 0;                /* Sizes of deleted documents */
+  int nChng = 0;                  /* Net change in number of documents */
+  int bInsertDone = 0;
 
-  assert( iLevel==FTS3_SEGCURSOR_ALL
-       || iLevel==FTS3_SEGCURSOR_PENDING
-       || iLevel>=0
-  );
-  assert( iLevel<FTS3_SEGDIR_MAXLEVEL );
-  assert( iIndex>=0 && iIndex<p->nIndex );
+  /* At this point it must be known if the %_stat table exists or not.
+  ** So bHasStat may not be 2.  */
+  assert( p->bHasStat==0 || p->bHasStat==1 );
 
-  rc = sqlite3Fts3SegReaderCursor(p, iLangid, iIndex, iLevel, 0, 0, 1, 0, &csr);
-  if( rc!=SQLITE_OK || csr.nSegment==0 ) goto finished;
+  assert( p->pSegments==0 );
+  assert( 
+      nArg==1                     /* DELETE operations */
+   || nArg==(2 + p->nColumn + 3)  /* INSERT or UPDATE operations */
+  );
 
-  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
-    rc = fts3SegmentMaxLevel(p, iLangid, iIndex, &iMaxLevel);
-    if( rc!=SQLITE_OK ) goto finished;
+  /* Check for a "special" INSERT operation. One of the form:
+  **
+  **   INSERT INTO xyz(xyz) VALUES('command');
+  */
+  if( nArg>1 
+   && sqlite3_value_type(apVal[0])==SQLITE_NULL 
+   && sqlite3_value_type(apVal[p->nColumn+2])!=SQLITE_NULL 
+  ){
+    rc = fts3SpecialInsert(p, apVal[p->nColumn+2]);
+    goto update_out;
   }
 
-  if( iLevel==FTS3_SEGCURSOR_ALL ){
-    /* This call is to merge all segments in the database to a single
-    ** segment. The level of the new segment is equal to the numerically
-    ** greatest segment level currently present in the database for this
-    ** index. The idx of the new segment is always 0.  */
-    if( csr.nSegment==1 ){
-      rc = SQLITE_DONE;
-      goto finished;
-    }
-    iNewLevel = iMaxLevel;
-    bIgnoreEmpty = 1;
+  if( nArg>1 && sqlite3_value_int(apVal[2 + p->nColumn + 2])<0 ){
+    rc = SQLITE_CONSTRAINT;
+    goto update_out;
+  }
 
-  }else{
-    /* This call is to merge all segments at level iLevel. find the next
-    ** available segment index at level iLevel+1. The call to
-    ** fts3AllocateSegdirIdx() will merge the segments at level iLevel+1 to 
-    ** a single iLevel+2 segment if necessary.  */
-    assert( FTS3_SEGCURSOR_PENDING==-1 );
-    iNewLevel = getAbsoluteLevel(p, iLangid, iIndex, iLevel+1);
-    rc = fts3AllocateSegdirIdx(p, iLangid, iIndex, iLevel+1, &iIdx);
-    bIgnoreEmpty = (iLevel!=FTS3_SEGCURSOR_PENDING) && (iNewLevel>iMaxLevel);
+  /* Allocate space to hold the change in document sizes */
+  aSzDel = sqlite3_malloc( sizeof(aSzDel[0])*(p->nColumn+1)*2 );
+  if( aSzDel==0 ){
+    rc = SQLITE_NOMEM;
+    goto update_out;
   }
-  if( rc!=SQLITE_OK ) goto finished;
+  aSzIns = &aSzDel[p->nColumn+1];
+  memset(aSzDel, 0, sizeof(aSzDel[0])*(p->nColumn+1)*2);
 
-  assert( csr.nSegment>0 );
-  assert( iNewLevel>=getAbsoluteLevel(p, iLangid, iIndex, 0) );
-  assert( iNewLevel<getAbsoluteLevel(p, iLangid, iIndex,FTS3_SEGDIR_MAXLEVEL) );
+  rc = fts3Writelock(p);
+  if( rc!=SQLITE_OK ) goto update_out;
 
-  memset(&filter, 0, sizeof(Fts3SegFilter));
-  filter.flags = FTS3_SEGMENT_REQUIRE_POS;
-  filter.flags |= (bIgnoreEmpty ? FTS3_SEGMENT_IGNORE_EMPTY : 0);
+  /* If this is an INSERT operation, or an UPDATE that modifies the rowid
+  ** value, then this operation requires constraint handling.
+  **
+  ** If the on-conflict mode is REPLACE, this means that the existing row
+  ** should be deleted from the database before inserting the new row. Or,
+  ** if the on-conflict mode is other than REPLACE, then this method must
+  ** detect the conflict and return SQLITE_CONSTRAINT before beginning to
+  ** modify the database file.
+  */
+  if( nArg>1 && p->zContentTbl==0 ){
+    /* Find the value object that holds the new rowid value. */
+    sqlite3_value *pNewRowid = apVal[3+p->nColumn];
+    if( sqlite3_value_type(pNewRowid)==SQLITE_NULL ){
+      pNewRowid = apVal[1];
+    }
 
-  rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
-  while( SQLITE_OK==rc ){
-    rc = sqlite3Fts3SegReaderStep(p, &csr);
-    if( rc!=SQLITE_ROW ) break;
-    rc = fts3SegWriterAdd(p, &pWriter, 1, 
-        csr.zTerm, csr.nTerm, csr.aDoclist, csr.nDoclist);
+    if( sqlite3_value_type(pNewRowid)!=SQLITE_NULL && ( 
+        sqlite3_value_type(apVal[0])==SQLITE_NULL
+     || sqlite3_value_int64(apVal[0])!=sqlite3_value_int64(pNewRowid)
+    )){
+      /* The new rowid is not NULL (in this case the rowid will be
+      ** automatically assigned and there is no chance of a conflict), and 
+      ** the statement is either an INSERT or an UPDATE that modifies the
+      ** rowid column. So if the conflict mode is REPLACE, then delete any
+      ** existing row with rowid=pNewRowid. 
+      **
+      ** Or, if the conflict mode is not REPLACE, insert the new record into 
+      ** the %_content table. If we hit the duplicate rowid constraint (or any
+      ** other error) while doing so, return immediately.
+      **
+      ** This branch may also run if pNewRowid contains a value that cannot
+      ** be losslessly converted to an integer. In this case, the eventual 
+      ** call to fts3InsertData() (either just below or further on in this
+      ** function) will return SQLITE_MISMATCH. If fts3DeleteByRowid is 
+      ** invoked, it will delete zero rows (since no row will have
+      ** docid=$pNewRowid if $pNewRowid is not an integer value).
+      */
+      if( sqlite3_vtab_on_conflict(p->db)==SQLITE_REPLACE ){
+        rc = fts3DeleteByRowid(p, pNewRowid, &nChng, aSzDel);
+      }else{
+        rc = fts3InsertData(p, apVal, pRowid);
+        bInsertDone = 1;
+      }
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    goto update_out;
   }
-  if( rc!=SQLITE_OK ) goto finished;
-  assert( pWriter || bIgnoreEmpty );
 
-  if( iLevel!=FTS3_SEGCURSOR_PENDING ){
-    rc = fts3DeleteSegdir(
-        p, iLangid, iIndex, iLevel, csr.apSegment, csr.nSegment
-    );
-    if( rc!=SQLITE_OK ) goto finished;
+  /* If this is a DELETE or UPDATE operation, remove the old record. */
+  if( sqlite3_value_type(apVal[0])!=SQLITE_NULL ){
+    assert( sqlite3_value_type(apVal[0])==SQLITE_INTEGER );
+    rc = fts3DeleteByRowid(p, apVal[0], &nChng, aSzDel);
+    isRemove = 1;
   }
-  if( pWriter ){
-    rc = fts3SegWriterFlush(p, pWriter, iNewLevel, iIdx);
-    if( rc==SQLITE_OK ){
-      if( iLevel==FTS3_SEGCURSOR_PENDING || iNewLevel<iMaxLevel ){
-        rc = fts3PromoteSegments(p, iNewLevel, pWriter->nLeafData);
+  
+  /* If this is an INSERT or UPDATE operation, insert the new record. */
+  if( nArg>1 && rc==SQLITE_OK ){
+    int iLangid = sqlite3_value_int(apVal[2 + p->nColumn + 2]);
+    if( bInsertDone==0 ){
+      rc = fts3InsertData(p, apVal, pRowid);
+      if( rc==SQLITE_CONSTRAINT && p->zContentTbl==0 ){
+        rc = FTS_CORRUPT_VTAB;
       }
     }
+    if( rc==SQLITE_OK && (!isRemove || *pRowid!=p->iPrevDocid ) ){
+      rc = fts3PendingTermsDocid(p, iLangid, *pRowid);
+    }
+    if( rc==SQLITE_OK ){
+      assert( p->iPrevDocid==*pRowid );
+      rc = fts3InsertTerms(p, iLangid, apVal, aSzIns);
+    }
+    if( p->bHasDocsize ){
+      fts3InsertDocsize(&rc, p, aSzIns);
+    }
+    nChng++;
   }
 
- finished:
-  fts3SegWriterFree(pWriter);
-  sqlite3Fts3SegReaderFinish(&csr);
+  if( p->bFts4 ){
+    fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nChng);
+  }
+
+ update_out:
+  sqlite3_free(aSzDel);
+  sqlite3Fts3SegmentsClose(p);
   return rc;
 }
 
-
 /* 
-** Flush the contents of pendingTerms to level 0 segments. 
+** Flush any data in the pending-terms hash table to disk. If successful,
+** merge all segments in the database (including the new segment, if 
+** there was any data to flush) into a single segment. 
 */
-SQLITE_PRIVATE int sqlite3Fts3PendingTermsFlush(Fts3Table *p){
-  int rc = SQLITE_OK;
-  int i;
-        
-  for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
-    rc = fts3SegmentMerge(p, p->iPrevLangid, i, FTS3_SEGCURSOR_PENDING);
-    if( rc==SQLITE_DONE ) rc = SQLITE_OK;
-  }
-  sqlite3Fts3PendingTermsClear(p);
-
-  /* Determine the auto-incr-merge setting if unknown.  If enabled,
-  ** estimate the number of leaf blocks of content to be written
-  */
-  if( rc==SQLITE_OK && p->bHasStat
-   && p->nAutoincrmerge==0xff && p->nLeafAdd>0
-  ){
-    sqlite3_stmt *pStmt = 0;
-    rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pStmt, 0);
-    if( rc==SQLITE_OK ){
-      sqlite3_bind_int(pStmt, 1, FTS_STAT_AUTOINCRMERGE);
-      rc = sqlite3_step(pStmt);
-      if( rc==SQLITE_ROW ){
-        p->nAutoincrmerge = sqlite3_column_int(pStmt, 0);
-        if( p->nAutoincrmerge==1 ) p->nAutoincrmerge = 8;
-      }else if( rc==SQLITE_DONE ){
-        p->nAutoincrmerge = 0;
-      }
-      rc = sqlite3_reset(pStmt);
+SQLITE_PRIVATE int sqlite3Fts3Optimize(Fts3Table *p){
+  int rc;
+  rc = sqlite3_exec(p->db, "SAVEPOINT fts3", 0, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = fts3DoOptimize(p, 1);
+    if( rc==SQLITE_OK || rc==SQLITE_DONE ){
+      int rc2 = sqlite3_exec(p->db, "RELEASE fts3", 0, 0, 0);
+      if( rc2!=SQLITE_OK ) rc = rc2;
+    }else{
+      sqlite3_exec(p->db, "ROLLBACK TO fts3", 0, 0, 0);
+      sqlite3_exec(p->db, "RELEASE fts3", 0, 0, 0);
     }
   }
+  sqlite3Fts3SegmentsClose(p);
   return rc;
 }
 
+#endif
+
+/************** End of fts3_write.c ******************************************/
+/************** Begin file fts3_snippet.c ************************************/
 /*
-** Encode N integers as varints into a blob.
+** 2009 Oct 23
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
 */
-static void fts3EncodeIntArray(
-  int N,             /* The number of integers to encode */
-  u32 *a,            /* The integer values */
-  char *zBuf,        /* Write the BLOB here */
-  int *pNBuf         /* Write number of bytes if zBuf[] used here */
-){
-  int i, j;
-  for(i=j=0; i<N; i++){
-    j += sqlite3Fts3PutVarint(&zBuf[j], (sqlite3_int64)a[i]);
-  }
-  *pNBuf = j;
-}
+
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <string.h> */
+/* #include <assert.h> */
 
 /*
-** Decode a blob of varints into N integers
+** Characters that may appear in the second argument to matchinfo().
 */
-static void fts3DecodeIntArray(
-  int N,             /* The number of integers to decode */
-  u32 *a,            /* Write the integer values */
-  const char *zBuf,  /* The BLOB containing the varints */
-  int nBuf           /* size of the BLOB */
-){
-  int i, j;
-  UNUSED_PARAMETER(nBuf);
-  for(i=j=0; i<N; i++){
-    sqlite3_int64 x;
-    j += sqlite3Fts3GetVarint(&zBuf[j], &x);
-    assert(j<=nBuf);
-    a[i] = (u32)(x & 0xffffffff);
-  }
-}
+#define FTS3_MATCHINFO_NPHRASE   'p'        /* 1 value */
+#define FTS3_MATCHINFO_NCOL      'c'        /* 1 value */
+#define FTS3_MATCHINFO_NDOC      'n'        /* 1 value */
+#define FTS3_MATCHINFO_AVGLENGTH 'a'        /* nCol values */
+#define FTS3_MATCHINFO_LENGTH    'l'        /* nCol values */
+#define FTS3_MATCHINFO_LCS       's'        /* nCol values */
+#define FTS3_MATCHINFO_HITS      'x'        /* 3*nCol*nPhrase values */
+#define FTS3_MATCHINFO_LHITS     'y'        /* nCol*nPhrase values */
+#define FTS3_MATCHINFO_LHITS_BM  'b'        /* nCol*nPhrase values */
 
 /*
-** Insert the sizes (in tokens) for each column of the document
-** with docid equal to p->iPrevDocid.  The sizes are encoded as
-** a blob of varints.
+** The default value for the second argument to matchinfo(). 
 */
-static void fts3InsertDocsize(
-  int *pRC,                       /* Result code */
-  Fts3Table *p,                   /* Table into which to insert */
-  u32 *aSz                        /* Sizes of each column, in tokens */
-){
-  char *pBlob;             /* The BLOB encoding of the document size */
-  int nBlob;               /* Number of bytes in the BLOB */
-  sqlite3_stmt *pStmt;     /* Statement used to insert the encoding */
-  int rc;                  /* Result code from subfunctions */
+#define FTS3_MATCHINFO_DEFAULT   "pcx"
 
-  if( *pRC ) return;
-  pBlob = sqlite3_malloc( 10*p->nColumn );
-  if( pBlob==0 ){
-    *pRC = SQLITE_NOMEM;
-    return;
-  }
-  fts3EncodeIntArray(p->nColumn, aSz, pBlob, &nBlob);
-  rc = fts3SqlStmt(p, SQL_REPLACE_DOCSIZE, &pStmt, 0);
-  if( rc ){
-    sqlite3_free(pBlob);
-    *pRC = rc;
-    return;
-  }
-  sqlite3_bind_int64(pStmt, 1, p->iPrevDocid);
-  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, sqlite3_free);
-  sqlite3_step(pStmt);
-  *pRC = sqlite3_reset(pStmt);
-}
 
 /*
-** Record 0 of the %_stat table contains a blob consisting of N varints,
-** where N is the number of user defined columns in the fts3 table plus
-** two. If nCol is the number of user defined columns, then values of the 
-** varints are set as follows:
-**
-**   Varint 0:       Total number of rows in the table.
-**
-**   Varint 1..nCol: For each column, the total number of tokens stored in
-**                   the column for all rows of the table.
-**
-**   Varint 1+nCol:  The total size, in bytes, of all text values in all
-**                   columns of all rows of the table.
-**
+** Used as an fts3ExprIterate() context when loading phrase doclists to
+** Fts3Expr.aDoclist[]/nDoclist.
 */
-static void fts3UpdateDocTotals(
-  int *pRC,                       /* The result code */
-  Fts3Table *p,                   /* Table being updated */
-  u32 *aSzIns,                    /* Size increases */
-  u32 *aSzDel,                    /* Size decreases */
-  int nChng                       /* Change in the number of documents */
-){
-  char *pBlob;             /* Storage for BLOB written into %_stat */
-  int nBlob;               /* Size of BLOB written into %_stat */
-  u32 *a;                  /* Array of integers that becomes the BLOB */
-  sqlite3_stmt *pStmt;     /* Statement for reading and writing */
-  int i;                   /* Loop counter */
-  int rc;                  /* Result code from subfunctions */
+typedef struct LoadDoclistCtx LoadDoclistCtx;
+struct LoadDoclistCtx {
+  Fts3Cursor *pCsr;               /* FTS3 Cursor */
+  int nPhrase;                    /* Number of phrases seen so far */
+  int nToken;                     /* Number of tokens seen so far */
+};
 
-  const int nStat = p->nColumn+2;
+/*
+** The following types are used as part of the implementation of the 
+** fts3BestSnippet() routine.
+*/
+typedef struct SnippetIter SnippetIter;
+typedef struct SnippetPhrase SnippetPhrase;
+typedef struct SnippetFragment SnippetFragment;
 
-  if( *pRC ) return;
-  a = sqlite3_malloc( (sizeof(u32)+10)*nStat );
-  if( a==0 ){
-    *pRC = SQLITE_NOMEM;
-    return;
-  }
-  pBlob = (char*)&a[nStat];
-  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pStmt, 0);
-  if( rc ){
-    sqlite3_free(a);
-    *pRC = rc;
-    return;
+struct SnippetIter {
+  Fts3Cursor *pCsr;               /* Cursor snippet is being generated from */
+  int iCol;                       /* Extract snippet from this column */
+  int nSnippet;                   /* Requested snippet length (in tokens) */
+  int nPhrase;                    /* Number of phrases in query */
+  SnippetPhrase *aPhrase;         /* Array of size nPhrase */
+  int iCurrent;                   /* First token of current snippet */
+};
+
+struct SnippetPhrase {
+  int nToken;                     /* Number of tokens in phrase */
+  char *pList;                    /* Pointer to start of phrase position list */
+  int iHead;                      /* Next value in position list */
+  char *pHead;                    /* Position list data following iHead */
+  int iTail;                      /* Next value in trailing position list */
+  char *pTail;                    /* Position list data following iTail */
+};
+
+struct SnippetFragment {
+  int iCol;                       /* Column snippet is extracted from */
+  int iPos;                       /* Index of first token in snippet */
+  u64 covered;                    /* Mask of query phrases covered */
+  u64 hlmask;                     /* Mask of snippet terms to highlight */
+};
+
+/*
+** This type is used as an fts3ExprIterate() context object while 
+** accumulating the data returned by the matchinfo() function.
+*/
+typedef struct MatchInfo MatchInfo;
+struct MatchInfo {
+  Fts3Cursor *pCursor;            /* FTS3 Cursor */
+  int nCol;                       /* Number of columns in table */
+  int nPhrase;                    /* Number of matchable phrases in query */
+  sqlite3_int64 nDoc;             /* Number of docs in database */
+  char flag;
+  u32 *aMatchinfo;                /* Pre-allocated buffer */
+};
+
+/*
+** An instance of this structure is used to manage a pair of buffers, each
+** (nElem * sizeof(u32)) bytes in size. See the MatchinfoBuffer code below
+** for details.
+*/
+struct MatchinfoBuffer {
+  u8 aRef[3];
+  int nElem;
+  int bGlobal;                    /* Set if global data is loaded */
+  char *zMatchinfo;
+  u32 aMatchinfo[1];
+};
+
+
+/*
+** The snippet() and offsets() functions both return text values. An instance
+** of the following structure is used to accumulate those values while the
+** functions are running. See fts3StringAppend() for details.
+*/
+typedef struct StrBuffer StrBuffer;
+struct StrBuffer {
+  char *z;                        /* Pointer to buffer containing string */
+  int n;                          /* Length of z in bytes (excl. nul-term) */
+  int nAlloc;                     /* Allocated size of buffer z in bytes */
+};
+
+
+/*************************************************************************
+** Start of MatchinfoBuffer code.
+*/
+
+/*
+** Allocate a two-slot MatchinfoBuffer object.
+*/
+static MatchinfoBuffer *fts3MIBufferNew(int nElem, const char *zMatchinfo){
+  MatchinfoBuffer *pRet;
+  int nByte = sizeof(u32) * (2*nElem + 1) + sizeof(MatchinfoBuffer);
+  int nStr = (int)strlen(zMatchinfo);
+
+  pRet = sqlite3_malloc(nByte + nStr+1);
+  if( pRet ){
+    memset(pRet, 0, nByte);
+    pRet->aMatchinfo[0] = (u8*)(&pRet->aMatchinfo[1]) - (u8*)pRet;
+    pRet->aMatchinfo[1+nElem] = pRet->aMatchinfo[0] + sizeof(u32)*(nElem+1);
+    pRet->nElem = nElem;
+    pRet->zMatchinfo = ((char*)pRet) + nByte;
+    memcpy(pRet->zMatchinfo, zMatchinfo, nStr+1);
+    pRet->aRef[0] = 1;
   }
-  sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
-  if( sqlite3_step(pStmt)==SQLITE_ROW ){
-    fts3DecodeIntArray(nStat, a,
-         sqlite3_column_blob(pStmt, 0),
-         sqlite3_column_bytes(pStmt, 0));
+
+  return pRet;
+}
+
+static void fts3MIBufferFree(void *p){
+  MatchinfoBuffer *pBuf = (MatchinfoBuffer*)((u8*)p - ((u32*)p)[-1]);
+
+  assert( (u32*)p==&pBuf->aMatchinfo[1] 
+       || (u32*)p==&pBuf->aMatchinfo[pBuf->nElem+2] 
+  );
+  if( (u32*)p==&pBuf->aMatchinfo[1] ){
+    pBuf->aRef[1] = 0;
   }else{
-    memset(a, 0, sizeof(u32)*(nStat) );
+    pBuf->aRef[2] = 0;
   }
-  rc = sqlite3_reset(pStmt);
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(a);
-    *pRC = rc;
-    return;
+
+  if( pBuf->aRef[0]==0 && pBuf->aRef[1]==0 && pBuf->aRef[2]==0 ){
+    sqlite3_free(pBuf);
   }
-  if( nChng<0 && a[0]<(u32)(-nChng) ){
-    a[0] = 0;
-  }else{
-    a[0] += nChng;
+}
+
+static void (*fts3MIBufferAlloc(MatchinfoBuffer *p, u32 **paOut))(void*){
+  void (*xRet)(void*) = 0;
+  u32 *aOut = 0;
+
+  if( p->aRef[1]==0 ){
+    p->aRef[1] = 1;
+    aOut = &p->aMatchinfo[1];
+    xRet = fts3MIBufferFree;
   }
-  for(i=0; i<p->nColumn+1; i++){
-    u32 x = a[i+1];
-    if( x+aSzIns[i] < aSzDel[i] ){
-      x = 0;
-    }else{
-      x = x + aSzIns[i] - aSzDel[i];
+  else if( p->aRef[2]==0 ){
+    p->aRef[2] = 1;
+    aOut = &p->aMatchinfo[p->nElem+2];
+    xRet = fts3MIBufferFree;
+  }else{
+    aOut = (u32*)sqlite3_malloc(p->nElem * sizeof(u32));
+    if( aOut ){
+      xRet = sqlite3_free;
+      if( p->bGlobal ) memcpy(aOut, &p->aMatchinfo[1], p->nElem*sizeof(u32));
     }
-    a[i+1] = x;
-  }
-  fts3EncodeIntArray(nStat, a, pBlob, &nBlob);
-  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pStmt, 0);
-  if( rc ){
-    sqlite3_free(a);
-    *pRC = rc;
-    return;
   }
-  sqlite3_bind_int(pStmt, 1, FTS_STAT_DOCTOTAL);
-  sqlite3_bind_blob(pStmt, 2, pBlob, nBlob, SQLITE_STATIC);
-  sqlite3_step(pStmt);
-  *pRC = sqlite3_reset(pStmt);
-  sqlite3_free(a);
+
+  *paOut = aOut;
+  return xRet;
+}
+
+static void fts3MIBufferSetGlobal(MatchinfoBuffer *p){
+  p->bGlobal = 1;
+  memcpy(&p->aMatchinfo[2+p->nElem], &p->aMatchinfo[1], p->nElem*sizeof(u32));
 }
 
 /*
-** Merge the entire database so that there is one segment for each 
-** iIndex/iLangid combination.
+** Free a MatchinfoBuffer object allocated using fts3MIBufferNew()
 */
-static int fts3DoOptimize(Fts3Table *p, int bReturnDone){
-  int bSeenDone = 0;
-  int rc;
-  sqlite3_stmt *pAllLangid = 0;
-
-  rc = fts3SqlStmt(p, SQL_SELECT_ALL_LANGID, &pAllLangid, 0);
-  if( rc==SQLITE_OK ){
-    int rc2;
-    sqlite3_bind_int(pAllLangid, 1, p->iPrevLangid);
-    sqlite3_bind_int(pAllLangid, 2, p->nIndex);
-    while( sqlite3_step(pAllLangid)==SQLITE_ROW ){
-      int i;
-      int iLangid = sqlite3_column_int(pAllLangid, 0);
-      for(i=0; rc==SQLITE_OK && i<p->nIndex; i++){
-        rc = fts3SegmentMerge(p, iLangid, i, FTS3_SEGCURSOR_ALL);
-        if( rc==SQLITE_DONE ){
-          bSeenDone = 1;
-          rc = SQLITE_OK;
-        }
-      }
+SQLITE_PRIVATE void sqlite3Fts3MIBufferFree(MatchinfoBuffer *p){
+  if( p ){
+    assert( p->aRef[0]==1 );
+    p->aRef[0] = 0;
+    if( p->aRef[0]==0 && p->aRef[1]==0 && p->aRef[2]==0 ){
+      sqlite3_free(p);
     }
-    rc2 = sqlite3_reset(pAllLangid);
-    if( rc==SQLITE_OK ) rc = rc2;
   }
+}
 
-  sqlite3Fts3SegmentsClose(p);
-  sqlite3Fts3PendingTermsClear(p);
+/* 
+** End of MatchinfoBuffer code.
+*************************************************************************/
 
-  return (rc==SQLITE_OK && bReturnDone && bSeenDone) ? SQLITE_DONE : rc;
-}
 
 /*
-** This function is called when the user executes the following statement:
+** This function is used to help iterate through a position-list. A position
+** list is a list of unique integers, sorted from smallest to largest. Each
+** element of the list is represented by an FTS3 varint that takes the value
+** of the difference between the current element and the previous one plus
+** two. For example, to store the position-list:
 **
-**     INSERT INTO <tbl>(<tbl>) VALUES('rebuild');
+**     4 9 113
 **
-** The entire FTS index is discarded and rebuilt. If the table is one 
-** created using the content=xxx option, then the new index is based on
-** the current contents of the xxx table. Otherwise, it is rebuilt based
-** on the contents of the %_content table.
+** the three varints:
+**
+**     6 7 106
+**
+** are encoded.
+**
+** When this function is called, *pp points to the start of an element of
+** the list. *piPos contains the value of the previous entry in the list.
+** After it returns, *piPos contains the value of the next element of the
+** list and *pp is advanced to the following varint.
 */
-static int fts3DoRebuild(Fts3Table *p){
-  int rc;                         /* Return Code */
-
-  rc = fts3DeleteAll(p, 0);
-  if( rc==SQLITE_OK ){
-    u32 *aSz = 0;
-    u32 *aSzIns = 0;
-    u32 *aSzDel = 0;
-    sqlite3_stmt *pStmt = 0;
-    int nEntry = 0;
-
-    /* Compose and prepare an SQL statement to loop through the content table */
-    char *zSql = sqlite3_mprintf("SELECT %s" , p->zReadExprlist);
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-    }else{
-      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
-      sqlite3_free(zSql);
-    }
-
-    if( rc==SQLITE_OK ){
-      int nByte = sizeof(u32) * (p->nColumn+1)*3;
-      aSz = (u32 *)sqlite3_malloc(nByte);
-      if( aSz==0 ){
-        rc = SQLITE_NOMEM;
-      }else{
-        memset(aSz, 0, nByte);
-        aSzIns = &aSz[p->nColumn+1];
-        aSzDel = &aSzIns[p->nColumn+1];
-      }
-    }
-
-    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
-      int iCol;
-      int iLangid = langidFromSelect(p, pStmt);
-      rc = fts3PendingTermsDocid(p, iLangid, sqlite3_column_int64(pStmt, 0));
-      memset(aSz, 0, sizeof(aSz[0]) * (p->nColumn+1));
-      for(iCol=0; rc==SQLITE_OK && iCol<p->nColumn; iCol++){
-        if( p->abNotindexed[iCol]==0 ){
-          const char *z = (const char *) sqlite3_column_text(pStmt, iCol+1);
-          rc = fts3PendingTermsAdd(p, iLangid, z, iCol, &aSz[iCol]);
-          aSz[p->nColumn] += sqlite3_column_bytes(pStmt, iCol+1);
-        }
-      }
-      if( p->bHasDocsize ){
-        fts3InsertDocsize(&rc, p, aSz);
-      }
-      if( rc!=SQLITE_OK ){
-        sqlite3_finalize(pStmt);
-        pStmt = 0;
-      }else{
-        nEntry++;
-        for(iCol=0; iCol<=p->nColumn; iCol++){
-          aSzIns[iCol] += aSz[iCol];
-        }
-      }
-    }
-    if( p->bFts4 ){
-      fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nEntry);
-    }
-    sqlite3_free(aSz);
-
-    if( pStmt ){
-      int rc2 = sqlite3_finalize(pStmt);
-      if( rc==SQLITE_OK ){
-        rc = rc2;
-      }
-    }
-  }
-
-  return rc;
+static void fts3GetDeltaPosition(char **pp, int *piPos){
+  int iVal;
+  *pp += fts3GetVarint32(*pp, &iVal);
+  *piPos += (iVal-2);
 }
 
-
 /*
-** This function opens a cursor used to read the input data for an 
-** incremental merge operation. Specifically, it opens a cursor to scan
-** the oldest nSeg segments (idx=0 through idx=(nSeg-1)) in absolute 
-** level iAbsLevel.
+** Helper function for fts3ExprIterate() (see below).
 */
-static int fts3IncrmergeCsr(
-  Fts3Table *p,                   /* FTS3 table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level to open */
-  int nSeg,                       /* Number of segments to merge */
-  Fts3MultiSegReader *pCsr        /* Cursor object to populate */
+static int fts3ExprIterate2(
+  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
+  int *piPhrase,                  /* Pointer to phrase counter */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
+  void *pCtx                      /* Second argument to pass to callback */
 ){
-  int rc;                         /* Return Code */
-  sqlite3_stmt *pStmt = 0;        /* Statement used to read %_segdir entry */  
-  int nByte;                      /* Bytes allocated at pCsr->apSegment[] */
-
-  /* Allocate space for the Fts3MultiSegReader.aCsr[] array */
-  memset(pCsr, 0, sizeof(*pCsr));
-  nByte = sizeof(Fts3SegReader *) * nSeg;
-  pCsr->apSegment = (Fts3SegReader **)sqlite3_malloc(nByte);
+  int rc;                         /* Return code */
+  int eType = pExpr->eType;     /* Type of expression node pExpr */
 
-  if( pCsr->apSegment==0 ){
-    rc = SQLITE_NOMEM;
-  }else{
-    memset(pCsr->apSegment, 0, nByte);
-    rc = fts3SqlStmt(p, SQL_SELECT_LEVEL, &pStmt, 0);
-  }
-  if( rc==SQLITE_OK ){
-    int i;
-    int rc2;
-    sqlite3_bind_int64(pStmt, 1, iAbsLevel);
-    assert( pCsr->nSegment==0 );
-    for(i=0; rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW && i<nSeg; i++){
-      rc = sqlite3Fts3SegReaderNew(i, 0,
-          sqlite3_column_int64(pStmt, 1),        /* segdir.start_block */
-          sqlite3_column_int64(pStmt, 2),        /* segdir.leaves_end_block */
-          sqlite3_column_int64(pStmt, 3),        /* segdir.end_block */
-          sqlite3_column_blob(pStmt, 4),         /* segdir.root */
-          sqlite3_column_bytes(pStmt, 4),        /* segdir.root */
-          &pCsr->apSegment[i]
-      );
-      pCsr->nSegment++;
+  if( eType!=FTSQUERY_PHRASE ){
+    assert( pExpr->pLeft && pExpr->pRight );
+    rc = fts3ExprIterate2(pExpr->pLeft, piPhrase, x, pCtx);
+    if( rc==SQLITE_OK && eType!=FTSQUERY_NOT ){
+      rc = fts3ExprIterate2(pExpr->pRight, piPhrase, x, pCtx);
     }
-    rc2 = sqlite3_reset(pStmt);
-    if( rc==SQLITE_OK ) rc = rc2;
+  }else{
+    rc = x(pExpr, *piPhrase, pCtx);
+    (*piPhrase)++;
   }
-
   return rc;
 }
 
-typedef struct IncrmergeWriter IncrmergeWriter;
-typedef struct NodeWriter NodeWriter;
-typedef struct Blob Blob;
-typedef struct NodeReader NodeReader;
-
 /*
-** An instance of the following structure is used as a dynamic buffer
-** to build up nodes or other blobs of data in.
+** Iterate through all phrase nodes in an FTS3 query, except those that
+** are part of a sub-tree that is the right-hand-side of a NOT operator.
+** For each phrase node found, the supplied callback function is invoked.
 **
-** The function blobGrowBuffer() is used to extend the allocation.
+** If the callback function returns anything other than SQLITE_OK, 
+** the iteration is abandoned and the error code returned immediately.
+** Otherwise, SQLITE_OK is returned after a callback has been made for
+** all eligible phrase nodes.
 */
-struct Blob {
-  char *a;                        /* Pointer to allocation */
-  int n;                          /* Number of valid bytes of data in a[] */
-  int nAlloc;                     /* Allocated size of a[] (nAlloc>=n) */
-};
+static int fts3ExprIterate(
+  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
+  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
+  void *pCtx                      /* Second argument to pass to callback */
+){
+  int iPhrase = 0;                /* Variable used as the phrase counter */
+  return fts3ExprIterate2(pExpr, &iPhrase, x, pCtx);
+}
 
-/*
-** This structure is used to build up buffers containing segment b-tree 
-** nodes (blocks).
-*/
-struct NodeWriter {
-  sqlite3_int64 iBlock;           /* Current block id */
-  Blob key;                       /* Last key written to the current block */
-  Blob block;                     /* Current block image */
-};
 
 /*
-** An object of this type contains the state required to create or append
-** to an appendable b-tree segment.
-*/
-struct IncrmergeWriter {
-  int nLeafEst;                   /* Space allocated for leaf blocks */
-  int nWork;                      /* Number of leaf pages flushed */
-  sqlite3_int64 iAbsLevel;        /* Absolute level of input segments */
-  int iIdx;                       /* Index of *output* segment in iAbsLevel+1 */
-  sqlite3_int64 iStart;           /* Block number of first allocated block */
-  sqlite3_int64 iEnd;             /* Block number of last allocated block */
-  sqlite3_int64 nLeafData;        /* Bytes of leaf page data so far */
-  u8 bNoLeafData;                 /* If true, store 0 for segment size */
-  NodeWriter aNodeWriter[FTS_MAX_APPENDABLE_HEIGHT];
-};
+** This is an fts3ExprIterate() callback used while loading the doclists
+** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
+** fts3ExprLoadDoclists().
+*/
+static int fts3ExprLoadDoclistsCb(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  int rc = SQLITE_OK;
+  Fts3Phrase *pPhrase = pExpr->pPhrase;
+  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
+
+  UNUSED_PARAMETER(iPhrase);
+
+  p->nPhrase++;
+  p->nToken += pPhrase->nToken;
+
+  return rc;
+}
 
 /*
-** An object of the following type is used to read data from a single
-** FTS segment node. See the following functions:
+** Load the doclists for each phrase in the query associated with FTS3 cursor
+** pCsr. 
 **
-**     nodeReaderInit()
-**     nodeReaderNext()
-**     nodeReaderRelease()
+** If pnPhrase is not NULL, then *pnPhrase is set to the number of matchable 
+** phrases in the expression (all phrases except those directly or 
+** indirectly descended from the right-hand-side of a NOT operator). If 
+** pnToken is not NULL, then it is set to the number of tokens in all
+** matchable phrases of the expression.
 */
-struct NodeReader {
-  const char *aNode;
-  int nNode;
-  int iOff;                       /* Current offset within aNode[] */
+static int fts3ExprLoadDoclists(
+  Fts3Cursor *pCsr,               /* Fts3 cursor for current query */
+  int *pnPhrase,                  /* OUT: Number of phrases in query */
+  int *pnToken                    /* OUT: Number of tokens in query */
+){
+  int rc;                         /* Return Code */
+  LoadDoclistCtx sCtx = {0,0,0};  /* Context for fts3ExprIterate() */
+  sCtx.pCsr = pCsr;
+  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb, (void *)&sCtx);
+  if( pnPhrase ) *pnPhrase = sCtx.nPhrase;
+  if( pnToken ) *pnToken = sCtx.nToken;
+  return rc;
+}
 
-  /* Output variables. Containing the current node entry. */
-  sqlite3_int64 iChild;           /* Pointer to child node */
-  Blob term;                      /* Current term */
-  const char *aDoclist;           /* Pointer to doclist */
-  int nDoclist;                   /* Size of doclist in bytes */
-};
+static int fts3ExprPhraseCountCb(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  (*(int *)ctx)++;
+  pExpr->iPhrase = iPhrase;
+  return SQLITE_OK;
+}
+static int fts3ExprPhraseCount(Fts3Expr *pExpr){
+  int nPhrase = 0;
+  (void)fts3ExprIterate(pExpr, fts3ExprPhraseCountCb, (void *)&nPhrase);
+  return nPhrase;
+}
 
 /*
-** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
-** Otherwise, if the allocation at pBlob->a is not already at least nMin
-** bytes in size, extend (realloc) it to be so.
-**
-** If an OOM error occurs, set *pRc to SQLITE_NOMEM and leave pBlob->a
-** unmodified. Otherwise, if the allocation succeeds, update pBlob->nAlloc
-** to reflect the new size of the pBlob->a[] buffer.
+** Advance the position list iterator specified by the first two 
+** arguments so that it points to the first element with a value greater
+** than or equal to parameter iNext.
 */
-static void blobGrowBuffer(Blob *pBlob, int nMin, int *pRc){
-  if( *pRc==SQLITE_OK && nMin>pBlob->nAlloc ){
-    int nAlloc = nMin;
-    char *a = (char *)sqlite3_realloc(pBlob->a, nAlloc);
-    if( a ){
-      pBlob->nAlloc = nAlloc;
-      pBlob->a = a;
-    }else{
-      *pRc = SQLITE_NOMEM;
+static void fts3SnippetAdvance(char **ppIter, int *piIter, int iNext){
+  char *pIter = *ppIter;
+  if( pIter ){
+    int iIter = *piIter;
+
+    while( iIter<iNext ){
+      if( 0==(*pIter & 0xFE) ){
+        iIter = -1;
+        pIter = 0;
+        break;
+      }
+      fts3GetDeltaPosition(&pIter, &iIter);
     }
+
+    *piIter = iIter;
+    *ppIter = pIter;
   }
 }
 
 /*
-** Attempt to advance the node-reader object passed as the first argument to
-** the next entry on the node. 
-**
-** Return an error code if an error occurs (SQLITE_NOMEM is possible). 
-** Otherwise return SQLITE_OK. If there is no next entry on the node
-** (e.g. because the current entry is the last) set NodeReader->aNode to
-** NULL to indicate EOF. Otherwise, populate the NodeReader structure output 
-** variables for the new entry.
+** Advance the snippet iterator to the next candidate snippet.
 */
-static int nodeReaderNext(NodeReader *p){
-  int bFirst = (p->term.n==0);    /* True for first term on the node */
-  int nPrefix = 0;                /* Bytes to copy from previous term */
-  int nSuffix = 0;                /* Bytes to append to the prefix */
-  int rc = SQLITE_OK;             /* Return code */
+static int fts3SnippetNextCandidate(SnippetIter *pIter){
+  int i;                          /* Loop counter */
 
-  assert( p->aNode );
-  if( p->iChild && bFirst==0 ) p->iChild++;
-  if( p->iOff>=p->nNode ){
-    /* EOF */
-    p->aNode = 0;
-  }else{
-    if( bFirst==0 ){
-      p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nPrefix);
+  if( pIter->iCurrent<0 ){
+    /* The SnippetIter object has just been initialized. The first snippet
+    ** candidate always starts at offset 0 (even if this candidate has a
+    ** score of 0.0).
+    */
+    pIter->iCurrent = 0;
+
+    /* Advance the 'head' iterator of each phrase to the first offset that
+    ** is greater than or equal to (iNext+nSnippet).
+    */
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, pIter->nSnippet);
     }
-    p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &nSuffix);
+  }else{
+    int iStart;
+    int iEnd = 0x7FFFFFFF;
 
-    blobGrowBuffer(&p->term, nPrefix+nSuffix, &rc);
-    if( rc==SQLITE_OK ){
-      memcpy(&p->term.a[nPrefix], &p->aNode[p->iOff], nSuffix);
-      p->term.n = nPrefix+nSuffix;
-      p->iOff += nSuffix;
-      if( p->iChild==0 ){
-        p->iOff += fts3GetVarint32(&p->aNode[p->iOff], &p->nDoclist);
-        p->aDoclist = &p->aNode[p->iOff];
-        p->iOff += p->nDoclist;
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      if( pPhrase->pHead && pPhrase->iHead<iEnd ){
+        iEnd = pPhrase->iHead;
       }
     }
-  }
+    if( iEnd==0x7FFFFFFF ){
+      return 1;
+    }
 
-  assert( p->iOff<=p->nNode );
+    pIter->iCurrent = iStart = iEnd - pIter->nSnippet + 1;
+    for(i=0; i<pIter->nPhrase; i++){
+      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, iEnd+1);
+      fts3SnippetAdvance(&pPhrase->pTail, &pPhrase->iTail, iStart);
+    }
+  }
 
-  return rc;
+  return 0;
 }
 
 /*
-** Release all dynamic resources held by node-reader object *p.
+** Retrieve information about the current candidate snippet of snippet 
+** iterator pIter.
 */
-static void nodeReaderRelease(NodeReader *p){
-  sqlite3_free(p->term.a);
+static void fts3SnippetDetails(
+  SnippetIter *pIter,             /* Snippet iterator */
+  u64 mCovered,                   /* Bitmask of phrases already covered */
+  int *piToken,                   /* OUT: First token of proposed snippet */
+  int *piScore,                   /* OUT: "Score" for this snippet */
+  u64 *pmCover,                   /* OUT: Bitmask of phrases covered */
+  u64 *pmHighlight                /* OUT: Bitmask of terms to highlight */
+){
+  int iStart = pIter->iCurrent;   /* First token of snippet */
+  int iScore = 0;                 /* Score of this snippet */
+  int i;                          /* Loop counter */
+  u64 mCover = 0;                 /* Mask of phrases covered by this snippet */
+  u64 mHighlight = 0;             /* Mask of tokens to highlight in snippet */
+
+  for(i=0; i<pIter->nPhrase; i++){
+    SnippetPhrase *pPhrase = &pIter->aPhrase[i];
+    if( pPhrase->pTail ){
+      char *pCsr = pPhrase->pTail;
+      int iCsr = pPhrase->iTail;
+
+      while( iCsr<(iStart+pIter->nSnippet) ){
+        int j;
+        u64 mPhrase = (u64)1 << i;
+        u64 mPos = (u64)1 << (iCsr - iStart);
+        assert( iCsr>=iStart );
+        if( (mCover|mCovered)&mPhrase ){
+          iScore++;
+        }else{
+          iScore += 1000;
+        }
+        mCover |= mPhrase;
+
+        for(j=0; j<pPhrase->nToken; j++){
+          mHighlight |= (mPos>>j);
+        }
+
+        if( 0==(*pCsr & 0x0FE) ) break;
+        fts3GetDeltaPosition(&pCsr, &iCsr);
+      }
+    }
+  }
+
+  /* Set the output variables before returning. */
+  *piToken = iStart;
+  *piScore = iScore;
+  *pmCover = mCover;
+  *pmHighlight = mHighlight;
 }
 
 /*
-** Initialize a node-reader object to read the node in buffer aNode/nNode.
-**
-** If successful, SQLITE_OK is returned and the NodeReader object set to 
-** point to the first entry on the node (if any). Otherwise, an SQLite
-** error code is returned.
+** This function is an fts3ExprIterate() callback used by fts3BestSnippet().
+** Each invocation populates an element of the SnippetIter.aPhrase[] array.
 */
-static int nodeReaderInit(NodeReader *p, const char *aNode, int nNode){
-  memset(p, 0, sizeof(NodeReader));
-  p->aNode = aNode;
-  p->nNode = nNode;
+static int fts3SnippetFindPositions(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  SnippetIter *p = (SnippetIter *)ctx;
+  SnippetPhrase *pPhrase = &p->aPhrase[iPhrase];
+  char *pCsr;
+  int rc;
 
-  /* Figure out if this is a leaf or an internal node. */
-  if( p->aNode[0] ){
-    /* An internal node. */
-    p->iOff = 1 + sqlite3Fts3GetVarint(&p->aNode[1], &p->iChild);
+  pPhrase->nToken = pExpr->pPhrase->nToken;
+  rc = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iCol, &pCsr);
+  assert( rc==SQLITE_OK || pCsr==0 );
+  if( pCsr ){
+    int iFirst = 0;
+    pPhrase->pList = pCsr;
+    fts3GetDeltaPosition(&pCsr, &iFirst);
+    assert( iFirst>=0 );
+    pPhrase->pHead = pCsr;
+    pPhrase->pTail = pCsr;
+    pPhrase->iHead = iFirst;
+    pPhrase->iTail = iFirst;
   }else{
-    p->iOff = 1;
+    assert( rc!=SQLITE_OK || (
+       pPhrase->pList==0 && pPhrase->pHead==0 && pPhrase->pTail==0 
+    ));
   }
 
-  return nodeReaderNext(p);
+  return rc;
 }
 
 /*
-** This function is called while writing an FTS segment each time a leaf o
-** node is finished and written to disk. The key (zTerm/nTerm) is guaranteed
-** to be greater than the largest key on the node just written, but smaller
-** than or equal to the first key that will be written to the next leaf
-** node.
+** Select the fragment of text consisting of nFragment contiguous tokens 
+** from column iCol that represent the "best" snippet. The best snippet
+** is the snippet with the highest score, where scores are calculated
+** by adding:
 **
-** The block id of the leaf node just written to disk may be found in
-** (pWriter->aNodeWriter[0].iBlock) when this function is called.
+**   (a) +1 point for each occurrence of a matchable phrase in the snippet.
+**
+**   (b) +1000 points for the first occurrence of each matchable phrase in 
+**       the snippet for which the corresponding mCovered bit is not set.
+**
+** The selected snippet parameters are stored in structure *pFragment before
+** returning. The score of the selected snippet is stored in *piScore
+** before returning.
 */
-static int fts3IncrmergePush(
-  Fts3Table *p,                   /* Fts3 table handle */
-  IncrmergeWriter *pWriter,       /* Writer object */
-  const char *zTerm,              /* Term to write to internal node */
-  int nTerm                       /* Bytes at zTerm */
+static int fts3BestSnippet(
+  int nSnippet,                   /* Desired snippet length */
+  Fts3Cursor *pCsr,               /* Cursor to create snippet for */
+  int iCol,                       /* Index of column to create snippet from */
+  u64 mCovered,                   /* Mask of phrases already covered */
+  u64 *pmSeen,                    /* IN/OUT: Mask of phrases seen */
+  SnippetFragment *pFragment,     /* OUT: Best snippet found */
+  int *piScore                    /* OUT: Score of snippet pFragment */
 ){
-  sqlite3_int64 iPtr = pWriter->aNodeWriter[0].iBlock;
-  int iLayer;
-
-  assert( nTerm>0 );
-  for(iLayer=1; ALWAYS(iLayer<FTS_MAX_APPENDABLE_HEIGHT); iLayer++){
-    sqlite3_int64 iNextPtr = 0;
-    NodeWriter *pNode = &pWriter->aNodeWriter[iLayer];
-    int rc = SQLITE_OK;
-    int nPrefix;
-    int nSuffix;
-    int nSpace;
+  int rc;                         /* Return Code */
+  int nList;                      /* Number of phrases in expression */
+  SnippetIter sIter;              /* Iterates through snippet candidates */
+  int nByte;                      /* Number of bytes of space to allocate */
+  int iBestScore = -1;            /* Best snippet score found so far */
+  int i;                          /* Loop counter */
 
-    /* Figure out how much space the key will consume if it is written to
-    ** the current node of layer iLayer. Due to the prefix compression, 
-    ** the space required changes depending on which node the key is to
-    ** be added to.  */
-    nPrefix = fts3PrefixCompress(pNode->key.a, pNode->key.n, zTerm, nTerm);
-    nSuffix = nTerm - nPrefix;
-    nSpace  = sqlite3Fts3VarintLen(nPrefix);
-    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
+  memset(&sIter, 0, sizeof(sIter));
 
-    if( pNode->key.n==0 || (pNode->block.n + nSpace)<=p->nNodeSize ){ 
-      /* If the current node of layer iLayer contains zero keys, or if adding
-      ** the key to it will not cause it to grow to larger than nNodeSize 
-      ** bytes in size, write the key here.  */
+  /* Iterate through the phrases in the expression to count them. The same
+  ** callback makes sure the doclists are loaded for each phrase.
+  */
+  rc = fts3ExprLoadDoclists(pCsr, &nList, 0);
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
 
-      Blob *pBlk = &pNode->block;
-      if( pBlk->n==0 ){
-        blobGrowBuffer(pBlk, p->nNodeSize, &rc);
-        if( rc==SQLITE_OK ){
-          pBlk->a[0] = (char)iLayer;
-          pBlk->n = 1 + sqlite3Fts3PutVarint(&pBlk->a[1], iPtr);
-        }
-      }
-      blobGrowBuffer(pBlk, pBlk->n + nSpace, &rc);
-      blobGrowBuffer(&pNode->key, nTerm, &rc);
+  /* Now that it is known how many phrases there are, allocate and zero
+  ** the required space using malloc().
+  */
+  nByte = sizeof(SnippetPhrase) * nList;
+  sIter.aPhrase = (SnippetPhrase *)sqlite3_malloc(nByte);
+  if( !sIter.aPhrase ){
+    return SQLITE_NOMEM;
+  }
+  memset(sIter.aPhrase, 0, nByte);
 
-      if( rc==SQLITE_OK ){
-        if( pNode->key.n ){
-          pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nPrefix);
-        }
-        pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nSuffix);
-        memcpy(&pBlk->a[pBlk->n], &zTerm[nPrefix], nSuffix);
-        pBlk->n += nSuffix;
+  /* Initialize the contents of the SnippetIter object. Then iterate through
+  ** the set of phrases in the expression to populate the aPhrase[] array.
+  */
+  sIter.pCsr = pCsr;
+  sIter.iCol = iCol;
+  sIter.nSnippet = nSnippet;
+  sIter.nPhrase = nList;
+  sIter.iCurrent = -1;
+  rc = fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void*)&sIter);
+  if( rc==SQLITE_OK ){
 
-        memcpy(pNode->key.a, zTerm, nTerm);
-        pNode->key.n = nTerm;
+    /* Set the *pmSeen output variable. */
+    for(i=0; i<nList; i++){
+      if( sIter.aPhrase[i].pHead ){
+        *pmSeen |= (u64)1 << i;
       }
-    }else{
-      /* Otherwise, flush the current node of layer iLayer to disk.
-      ** Then allocate a new, empty sibling node. The key will be written
-      ** into the parent of this node. */
-      rc = fts3WriteSegment(p, pNode->iBlock, pNode->block.a, pNode->block.n);
-
-      assert( pNode->block.nAlloc>=p->nNodeSize );
-      pNode->block.a[0] = (char)iLayer;
-      pNode->block.n = 1 + sqlite3Fts3PutVarint(&pNode->block.a[1], iPtr+1);
+    }
 
-      iNextPtr = pNode->iBlock;
-      pNode->iBlock++;
-      pNode->key.n = 0;
+    /* Loop through all candidate snippets. Store the best snippet in 
+     ** *pFragment. Store its associated 'score' in iBestScore.
+     */
+    pFragment->iCol = iCol;
+    while( !fts3SnippetNextCandidate(&sIter) ){
+      int iPos;
+      int iScore;
+      u64 mCover;
+      u64 mHighlite;
+      fts3SnippetDetails(&sIter, mCovered, &iPos, &iScore, &mCover,&mHighlite);
+      assert( iScore>=0 );
+      if( iScore>iBestScore ){
+        pFragment->iPos = iPos;
+        pFragment->hlmask = mHighlite;
+        pFragment->covered = mCover;
+        iBestScore = iScore;
+      }
     }
 
-    if( rc!=SQLITE_OK || iNextPtr==0 ) return rc;
-    iPtr = iNextPtr;
+    *piScore = iBestScore;
   }
-
-  assert( 0 );
-  return 0;
+  sqlite3_free(sIter.aPhrase);
+  return rc;
 }
 
+
 /*
-** Append a term and (optionally) doclist to the FTS segment node currently
-** stored in blob *pNode. The node need not contain any terms, but the
-** header must be written before this function is called.
-**
-** A node header is a single 0x00 byte for a leaf node, or a height varint
-** followed by the left-hand-child varint for an internal node.
-**
-** The term to be appended is passed via arguments zTerm/nTerm. For a 
-** leaf node, the doclist is passed as aDoclist/nDoclist. For an internal
-** node, both aDoclist and nDoclist must be passed 0.
-**
-** If the size of the value in blob pPrev is zero, then this is the first
-** term written to the node. Otherwise, pPrev contains a copy of the 
-** previous term. Before this function returns, it is updated to contain a
-** copy of zTerm/nTerm.
-**
-** It is assumed that the buffer associated with pNode is already large
-** enough to accommodate the new entry. The buffer associated with pPrev
-** is extended by this function if requrired.
+** Append a string to the string-buffer passed as the first argument.
 **
-** If an error (i.e. OOM condition) occurs, an SQLite error code is
-** returned. Otherwise, SQLITE_OK.
+** If nAppend is negative, then the length of the string zAppend is
+** determined using strlen().
 */
-static int fts3AppendToNode(
-  Blob *pNode,                    /* Current node image to append to */
-  Blob *pPrev,                    /* Buffer containing previous term written */
-  const char *zTerm,              /* New term to write */
-  int nTerm,                      /* Size of zTerm in bytes */
-  const char *aDoclist,           /* Doclist (or NULL) to write */
-  int nDoclist                    /* Size of aDoclist in bytes */ 
+static int fts3StringAppend(
+  StrBuffer *pStr,                /* Buffer to append to */
+  const char *zAppend,            /* Pointer to data to append to buffer */
+  int nAppend                     /* Size of zAppend in bytes (or -1) */
 ){
-  int rc = SQLITE_OK;             /* Return code */
-  int bFirst = (pPrev->n==0);     /* True if this is the first term written */
-  int nPrefix;                    /* Size of term prefix in bytes */
-  int nSuffix;                    /* Size of term suffix in bytes */
-
-  /* Node must have already been started. There must be a doclist for a
-  ** leaf node, and there must not be a doclist for an internal node.  */
-  assert( pNode->n>0 );
-  assert( (pNode->a[0]=='\0')==(aDoclist!=0) );
-
-  blobGrowBuffer(pPrev, nTerm, &rc);
-  if( rc!=SQLITE_OK ) return rc;
-
-  nPrefix = fts3PrefixCompress(pPrev->a, pPrev->n, zTerm, nTerm);
-  nSuffix = nTerm - nPrefix;
-  memcpy(pPrev->a, zTerm, nTerm);
-  pPrev->n = nTerm;
-
-  if( bFirst==0 ){
-    pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nPrefix);
+  if( nAppend<0 ){
+    nAppend = (int)strlen(zAppend);
   }
-  pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nSuffix);
-  memcpy(&pNode->a[pNode->n], &zTerm[nPrefix], nSuffix);
-  pNode->n += nSuffix;
 
-  if( aDoclist ){
-    pNode->n += sqlite3Fts3PutVarint(&pNode->a[pNode->n], nDoclist);
-    memcpy(&pNode->a[pNode->n], aDoclist, nDoclist);
-    pNode->n += nDoclist;
+  /* If there is insufficient space allocated at StrBuffer.z, use realloc()
+  ** to grow the buffer until so that it is big enough to accomadate the
+  ** appended data.
+  */
+  if( pStr->n+nAppend+1>=pStr->nAlloc ){
+    int nAlloc = pStr->nAlloc+nAppend+100;
+    char *zNew = sqlite3_realloc(pStr->z, nAlloc);
+    if( !zNew ){
+      return SQLITE_NOMEM;
+    }
+    pStr->z = zNew;
+    pStr->nAlloc = nAlloc;
   }
+  assert( pStr->z!=0 && (pStr->nAlloc >= pStr->n+nAppend+1) );
 
-  assert( pNode->n<=pNode->nAlloc );
+  /* Append the data to the string buffer. */
+  memcpy(&pStr->z[pStr->n], zAppend, nAppend);
+  pStr->n += nAppend;
+  pStr->z[pStr->n] = '\0';
 
   return SQLITE_OK;
 }
 
 /*
-** Append the current term and doclist pointed to by cursor pCsr to the
-** appendable b-tree segment opened for writing by pWriter.
+** The fts3BestSnippet() function often selects snippets that end with a
+** query term. That is, the final term of the snippet is always a term
+** that requires highlighting. For example, if 'X' is a highlighted term
+** and '.' is a non-highlighted term, BestSnippet() may select:
 **
-** Return SQLITE_OK if successful, or an SQLite error code otherwise.
+**     ........X.....X
+**
+** This function "shifts" the beginning of the snippet forward in the 
+** document so that there are approximately the same number of 
+** non-highlighted terms to the right of the final highlighted term as there
+** are to the left of the first highlighted term. For example, to this:
+**
+**     ....X.....X....
+**
+** This is done as part of extracting the snippet text, not when selecting
+** the snippet. Snippet selection is done based on doclists only, so there
+** is no way for fts3BestSnippet() to know whether or not the document 
+** actually contains terms that follow the final highlighted term. 
 */
-static int fts3IncrmergeAppend(
-  Fts3Table *p,                   /* Fts3 table handle */
-  IncrmergeWriter *pWriter,       /* Writer object */
-  Fts3MultiSegReader *pCsr        /* Cursor containing term and doclist */
+static int fts3SnippetShift(
+  Fts3Table *pTab,                /* FTS3 table snippet comes from */
+  int iLangid,                    /* Language id to use in tokenizing */
+  int nSnippet,                   /* Number of tokens desired for snippet */
+  const char *zDoc,               /* Document text to extract snippet from */
+  int nDoc,                       /* Size of buffer zDoc in bytes */
+  int *piPos,                     /* IN/OUT: First token of snippet */
+  u64 *pHlmask                    /* IN/OUT: Mask of tokens to highlight */
 ){
-  const char *zTerm = pCsr->zTerm;
-  int nTerm = pCsr->nTerm;
-  const char *aDoclist = pCsr->aDoclist;
-  int nDoclist = pCsr->nDoclist;
-  int rc = SQLITE_OK;           /* Return code */
-  int nSpace;                   /* Total space in bytes required on leaf */
-  int nPrefix;                  /* Size of prefix shared with previous term */
-  int nSuffix;                  /* Size of suffix (nTerm - nPrefix) */
-  NodeWriter *pLeaf;            /* Object used to write leaf nodes */
-
-  pLeaf = &pWriter->aNodeWriter[0];
-  nPrefix = fts3PrefixCompress(pLeaf->key.a, pLeaf->key.n, zTerm, nTerm);
-  nSuffix = nTerm - nPrefix;
+  u64 hlmask = *pHlmask;          /* Local copy of initial highlight-mask */
 
-  nSpace  = sqlite3Fts3VarintLen(nPrefix);
-  nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
-  nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
+  if( hlmask ){
+    int nLeft;                    /* Tokens to the left of first highlight */
+    int nRight;                   /* Tokens to the right of last highlight */
+    int nDesired;                 /* Ideal number of tokens to shift forward */
 
-  /* If the current block is not empty, and if adding this term/doclist
-  ** to the current block would make it larger than Fts3Table.nNodeSize
-  ** bytes, write this block out to the database. */
-  if( pLeaf->block.n>0 && (pLeaf->block.n + nSpace)>p->nNodeSize ){
-    rc = fts3WriteSegment(p, pLeaf->iBlock, pLeaf->block.a, pLeaf->block.n);
-    pWriter->nWork++;
+    for(nLeft=0; !(hlmask & ((u64)1 << nLeft)); nLeft++);
+    for(nRight=0; !(hlmask & ((u64)1 << (nSnippet-1-nRight))); nRight++);
+    nDesired = (nLeft-nRight)/2;
 
-    /* Add the current term to the parent node. The term added to the 
-    ** parent must:
-    **
-    **   a) be greater than the largest term on the leaf node just written
-    **      to the database (still available in pLeaf->key), and
-    **
-    **   b) be less than or equal to the term about to be added to the new
-    **      leaf node (zTerm/nTerm).
-    **
-    ** In other words, it must be the prefix of zTerm 1 byte longer than
-    ** the common prefix (if any) of zTerm and pWriter->zTerm.
+    /* Ideally, the start of the snippet should be pushed forward in the
+    ** document nDesired tokens. This block checks if there are actually
+    ** nDesired tokens to the right of the snippet. If so, *piPos and
+    ** *pHlMask are updated to shift the snippet nDesired tokens to the
+    ** right. Otherwise, the snippet is shifted by the number of tokens
+    ** available.
     */
-    if( rc==SQLITE_OK ){
-      rc = fts3IncrmergePush(p, pWriter, zTerm, nPrefix+1);
-    }
-
-    /* Advance to the next output block */
-    pLeaf->iBlock++;
-    pLeaf->key.n = 0;
-    pLeaf->block.n = 0;
+    if( nDesired>0 ){
+      int nShift;                 /* Number of tokens to shift snippet by */
+      int iCurrent = 0;           /* Token counter */
+      int rc;                     /* Return Code */
+      sqlite3_tokenizer_module *pMod;
+      sqlite3_tokenizer_cursor *pC;
+      pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
 
-    nSuffix = nTerm;
-    nSpace  = 1;
-    nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
-    nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;
-  }
+      /* Open a cursor on zDoc/nDoc. Check if there are (nSnippet+nDesired)
+      ** or more tokens in zDoc/nDoc.
+      */
+      rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, iLangid, zDoc, nDoc, &pC);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+      while( rc==SQLITE_OK && iCurrent<(nSnippet+nDesired) ){
+        const char *ZDUMMY; int DUMMY1 = 0, DUMMY2 = 0, DUMMY3 = 0;
+        rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
+      }
+      pMod->xClose(pC);
+      if( rc!=SQLITE_OK && rc!=SQLITE_DONE ){ return rc; }
 
-  pWriter->nLeafData += nSpace;
-  blobGrowBuffer(&pLeaf->block, pLeaf->block.n + nSpace, &rc);
-  if( rc==SQLITE_OK ){
-    if( pLeaf->block.n==0 ){
-      pLeaf->block.n = 1;
-      pLeaf->block.a[0] = '\0';
+      nShift = (rc==SQLITE_DONE)+iCurrent-nSnippet;
+      assert( nShift<=nDesired );
+      if( nShift>0 ){
+        *piPos += nShift;
+        *pHlmask = hlmask >> nShift;
+      }
     }
-    rc = fts3AppendToNode(
-        &pLeaf->block, &pLeaf->key, zTerm, nTerm, aDoclist, nDoclist
-    );
   }
-
-  return rc;
+  return SQLITE_OK;
 }
 
 /*
-** This function is called to release all dynamic resources held by the
-** merge-writer object pWriter, and if no error has occurred, to flush
-** all outstanding node buffers held by pWriter to disk.
-**
-** If *pRc is not SQLITE_OK when this function is called, then no attempt
-** is made to write any data to disk. Instead, this function serves only
-** to release outstanding resources.
-**
-** Otherwise, if *pRc is initially SQLITE_OK and an error occurs while
-** flushing buffers to disk, *pRc is set to an SQLite error code before
-** returning.
+** Extract the snippet text for fragment pFragment from cursor pCsr and
+** append it to string buffer pOut.
 */
-static void fts3IncrmergeRelease(
-  Fts3Table *p,                   /* FTS3 table handle */
-  IncrmergeWriter *pWriter,       /* Merge-writer object */
-  int *pRc                        /* IN/OUT: Error code */
+static int fts3SnippetText(
+  Fts3Cursor *pCsr,               /* FTS3 Cursor */
+  SnippetFragment *pFragment,     /* Snippet to extract */
+  int iFragment,                  /* Fragment number */
+  int isLast,                     /* True for final fragment in snippet */
+  int nSnippet,                   /* Number of tokens in extracted snippet */
+  const char *zOpen,              /* String inserted before highlighted term */
+  const char *zClose,             /* String inserted after highlighted term */
+  const char *zEllipsis,          /* String inserted between snippets */
+  StrBuffer *pOut                 /* Write output here */
 ){
-  int i;                          /* Used to iterate through non-root layers */
-  int iRoot;                      /* Index of root in pWriter->aNodeWriter */
-  NodeWriter *pRoot;              /* NodeWriter for root node */
-  int rc = *pRc;                  /* Error code */
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc;                         /* Return code */
+  const char *zDoc;               /* Document text to extract snippet from */
+  int nDoc;                       /* Size of zDoc in bytes */
+  int iCurrent = 0;               /* Current token number of document */
+  int iEnd = 0;                   /* Byte offset of end of current token */
+  int isShiftDone = 0;            /* True after snippet is shifted */
+  int iPos = pFragment->iPos;     /* First token of snippet */
+  u64 hlmask = pFragment->hlmask; /* Highlight-mask for snippet */
+  int iCol = pFragment->iCol+1;   /* Query column to extract text from */
+  sqlite3_tokenizer_module *pMod; /* Tokenizer module methods object */
+  sqlite3_tokenizer_cursor *pC;   /* Tokenizer cursor open on zDoc/nDoc */
+  
+  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol);
+  if( zDoc==0 ){
+    if( sqlite3_column_type(pCsr->pStmt, iCol)!=SQLITE_NULL ){
+      return SQLITE_NOMEM;
+    }
+    return SQLITE_OK;
+  }
+  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol);
 
-  /* Set iRoot to the index in pWriter->aNodeWriter[] of the output segment 
-  ** root node. If the segment fits entirely on a single leaf node, iRoot
-  ** will be set to 0. If the root node is the parent of the leaves, iRoot
-  ** will be 1. And so on.  */
-  for(iRoot=FTS_MAX_APPENDABLE_HEIGHT-1; iRoot>=0; iRoot--){
-    NodeWriter *pNode = &pWriter->aNodeWriter[iRoot];
-    if( pNode->block.n>0 ) break;
-    assert( *pRc || pNode->block.nAlloc==0 );
-    assert( *pRc || pNode->key.nAlloc==0 );
-    sqlite3_free(pNode->block.a);
-    sqlite3_free(pNode->key.a);
+  /* Open a token cursor on the document. */
+  pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
+  rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, pCsr->iLangid, zDoc,nDoc,&pC);
+  if( rc!=SQLITE_OK ){
+    return rc;
   }
 
-  /* Empty output segment. This is a no-op. */
-  if( iRoot<0 ) return;
+  while( rc==SQLITE_OK ){
+    const char *ZDUMMY;           /* Dummy argument used with tokenizer */
+    int DUMMY1 = -1;              /* Dummy argument used with tokenizer */
+    int iBegin = 0;               /* Offset in zDoc of start of token */
+    int iFin = 0;                 /* Offset in zDoc of end of token */
+    int isHighlight = 0;          /* True for highlighted terms */
 
-  /* The entire output segment fits on a single node. Normally, this means
-  ** the node would be stored as a blob in the "root" column of the %_segdir
-  ** table. However, this is not permitted in this case. The problem is that 
-  ** space has already been reserved in the %_segments table, and so the 
-  ** start_block and end_block fields of the %_segdir table must be populated. 
-  ** And, by design or by accident, released versions of FTS cannot handle 
-  ** segments that fit entirely on the root node with start_block!=0.
-  **
-  ** Instead, create a synthetic root node that contains nothing but a 
-  ** pointer to the single content node. So that the segment consists of a
-  ** single leaf and a single interior (root) node.
-  **
-  ** Todo: Better might be to defer allocating space in the %_segments 
-  ** table until we are sure it is needed.
-  */
-  if( iRoot==0 ){
-    Blob *pBlock = &pWriter->aNodeWriter[1].block;
-    blobGrowBuffer(pBlock, 1 + FTS3_VARINT_MAX, &rc);
-    if( rc==SQLITE_OK ){
-      pBlock->a[0] = 0x01;
-      pBlock->n = 1 + sqlite3Fts3PutVarint(
-          &pBlock->a[1], pWriter->aNodeWriter[0].iBlock
+    /* Variable DUMMY1 is initialized to a negative value above. Elsewhere
+    ** in the FTS code the variable that the third argument to xNext points to
+    ** is initialized to zero before the first (*but not necessarily
+    ** subsequent*) call to xNext(). This is done for a particular application
+    ** that needs to know whether or not the tokenizer is being used for
+    ** snippet generation or for some other purpose.
+    **
+    ** Extreme care is required when writing code to depend on this
+    ** initialization. It is not a documented part of the tokenizer interface.
+    ** If a tokenizer is used directly by any code outside of FTS, this
+    ** convention might not be respected.  */
+    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
+    if( rc!=SQLITE_OK ){
+      if( rc==SQLITE_DONE ){
+        /* Special case - the last token of the snippet is also the last token
+        ** of the column. Append any punctuation that occurred between the end
+        ** of the previous token and the end of the document to the output. 
+        ** Then break out of the loop. */
+        rc = fts3StringAppend(pOut, &zDoc[iEnd], -1);
+      }
+      break;
+    }
+    if( iCurrent<iPos ){ continue; }
+
+    if( !isShiftDone ){
+      int n = nDoc - iBegin;
+      rc = fts3SnippetShift(
+          pTab, pCsr->iLangid, nSnippet, &zDoc[iBegin], n, &iPos, &hlmask
       );
+      isShiftDone = 1;
+
+      /* Now that the shift has been done, check if the initial "..." are
+      ** required. They are required if (a) this is not the first fragment,
+      ** or (b) this fragment does not begin at position 0 of its column. 
+      */
+      if( rc==SQLITE_OK ){
+        if( iPos>0 || iFragment>0 ){
+          rc = fts3StringAppend(pOut, zEllipsis, -1);
+        }else if( iBegin ){
+          rc = fts3StringAppend(pOut, zDoc, iBegin);
+        }
+      }
+      if( rc!=SQLITE_OK || iCurrent<iPos ) continue;
     }
-    iRoot = 1;
-  }
-  pRoot = &pWriter->aNodeWriter[iRoot];
 
-  /* Flush all currently outstanding nodes to disk. */
-  for(i=0; i<iRoot; i++){
-    NodeWriter *pNode = &pWriter->aNodeWriter[i];
-    if( pNode->block.n>0 && rc==SQLITE_OK ){
-      rc = fts3WriteSegment(p, pNode->iBlock, pNode->block.a, pNode->block.n);
+    if( iCurrent>=(iPos+nSnippet) ){
+      if( isLast ){
+        rc = fts3StringAppend(pOut, zEllipsis, -1);
+      }
+      break;
     }
-    sqlite3_free(pNode->block.a);
-    sqlite3_free(pNode->key.a);
-  }
 
-  /* Write the %_segdir record. */
-  if( rc==SQLITE_OK ){
-    rc = fts3WriteSegdir(p, 
-        pWriter->iAbsLevel+1,               /* level */
-        pWriter->iIdx,                      /* idx */
-        pWriter->iStart,                    /* start_block */
-        pWriter->aNodeWriter[0].iBlock,     /* leaves_end_block */
-        pWriter->iEnd,                      /* end_block */
-        (pWriter->bNoLeafData==0 ? pWriter->nLeafData : 0),   /* end_block */
-        pRoot->block.a, pRoot->block.n      /* root */
-    );
+    /* Set isHighlight to true if this term should be highlighted. */
+    isHighlight = (hlmask & ((u64)1 << (iCurrent-iPos)))!=0;
+
+    if( iCurrent>iPos ) rc = fts3StringAppend(pOut, &zDoc[iEnd], iBegin-iEnd);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zOpen, -1);
+    if( rc==SQLITE_OK ) rc = fts3StringAppend(pOut, &zDoc[iBegin], iFin-iBegin);
+    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zClose, -1);
+
+    iEnd = iFin;
   }
-  sqlite3_free(pRoot->block.a);
-  sqlite3_free(pRoot->key.a);
 
-  *pRc = rc;
+  pMod->xClose(pC);
+  return rc;
 }
 
+
 /*
-** Compare the term in buffer zLhs (size in bytes nLhs) with that in
-** zRhs (size in bytes nRhs) using memcmp. If one term is a prefix of
-** the other, it is considered to be smaller than the other.
+** This function is used to count the entries in a column-list (a 
+** delta-encoded list of term offsets within a single column of a single 
+** row). When this function is called, *ppCollist should point to the
+** beginning of the first varint in the column-list (the varint that
+** contains the position of the first matching term in the column data).
+** Before returning, *ppCollist is set to point to the first byte after
+** the last varint in the column-list (either the 0x00 signifying the end
+** of the position-list, or the 0x01 that precedes the column number of
+** the next column in the position-list).
 **
-** Return -ve if zLhs is smaller than zRhs, 0 if it is equal, or +ve
-** if it is greater.
+** The number of elements in the column-list is returned.
 */
-static int fts3TermCmp(
-  const char *zLhs, int nLhs,     /* LHS of comparison */
-  const char *zRhs, int nRhs      /* RHS of comparison */
-){
-  int nCmp = MIN(nLhs, nRhs);
-  int res;
+static int fts3ColumnlistCount(char **ppCollist){
+  char *pEnd = *ppCollist;
+  char c = 0;
+  int nEntry = 0;
 
-  res = memcmp(zLhs, zRhs, nCmp);
-  if( res==0 ) res = nLhs - nRhs;
+  /* A column-list is terminated by either a 0x01 or 0x00. */
+  while( 0xFE & (*pEnd | c) ){
+    c = *pEnd++ & 0x80;
+    if( !c ) nEntry++;
+  }
 
-  return res;
+  *ppCollist = pEnd;
+  return nEntry;
 }
 
-
 /*
-** Query to see if the entry in the %_segments table with blockid iEnd is 
-** NULL. If no error occurs and the entry is NULL, set *pbRes 1 before
-** returning. Otherwise, set *pbRes to 0. 
-**
-** Or, if an error occurs while querying the database, return an SQLite 
-** error code. The final value of *pbRes is undefined in this case.
-**
-** This is used to test if a segment is an "appendable" segment. If it
-** is, then a NULL entry has been inserted into the %_segments table
-** with blockid %_segdir.end_block.
+** This function gathers 'y' or 'b' data for a single phrase.
 */
-static int fts3IsAppendable(Fts3Table *p, sqlite3_int64 iEnd, int *pbRes){
-  int bRes = 0;                   /* Result to set *pbRes to */
-  sqlite3_stmt *pCheck = 0;       /* Statement to query database with */
-  int rc;                         /* Return code */
+static void fts3ExprLHits(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  MatchInfo *p                    /* Matchinfo context */
+){
+  Fts3Table *pTab = (Fts3Table *)p->pCursor->base.pVtab;
+  int iStart;
+  Fts3Phrase *pPhrase = pExpr->pPhrase;
+  char *pIter = pPhrase->doclist.pList;
+  int iCol = 0;
 
-  rc = fts3SqlStmt(p, SQL_SEGMENT_IS_APPENDABLE, &pCheck, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pCheck, 1, iEnd);
-    if( SQLITE_ROW==sqlite3_step(pCheck) ) bRes = 1;
-    rc = sqlite3_reset(pCheck);
+  assert( p->flag==FTS3_MATCHINFO_LHITS_BM || p->flag==FTS3_MATCHINFO_LHITS );
+  if( p->flag==FTS3_MATCHINFO_LHITS ){
+    iStart = pExpr->iPhrase * p->nCol;
+  }else{
+    iStart = pExpr->iPhrase * ((p->nCol + 31) / 32);
+  }
+
+  while( 1 ){
+    int nHit = fts3ColumnlistCount(&pIter);
+    if( (pPhrase->iColumn>=pTab->nColumn || pPhrase->iColumn==iCol) ){
+      if( p->flag==FTS3_MATCHINFO_LHITS ){
+        p->aMatchinfo[iStart + iCol] = (u32)nHit;
+      }else if( nHit ){
+        p->aMatchinfo[iStart + (iCol+1)/32] |= (1 << (iCol&0x1F));
+      }
+    }
+    assert( *pIter==0x00 || *pIter==0x01 );
+    if( *pIter!=0x01 ) break;
+    pIter++;
+    pIter += fts3GetVarint32(pIter, &iCol);
   }
-  
-  *pbRes = bRes;
-  return rc;
 }
 
 /*
-** This function is called when initializing an incremental-merge operation.
-** It checks if the existing segment with index value iIdx at absolute level 
-** (iAbsLevel+1) can be appended to by the incremental merge. If it can, the
-** merge-writer object *pWriter is initialized to write to it.
+** Gather the results for matchinfo directives 'y' and 'b'.
+*/
+static void fts3ExprLHitGather(
+  Fts3Expr *pExpr,
+  MatchInfo *p
+){
+  assert( (pExpr->pLeft==0)==(pExpr->pRight==0) );
+  if( pExpr->bEof==0 && pExpr->iDocid==p->pCursor->iPrevId ){
+    if( pExpr->pLeft ){
+      fts3ExprLHitGather(pExpr->pLeft, p);
+      fts3ExprLHitGather(pExpr->pRight, p);
+    }else{
+      fts3ExprLHits(pExpr, p);
+    }
+  }
+}
+
+/*
+** fts3ExprIterate() callback used to collect the "global" matchinfo stats
+** for a single query. 
 **
-** An existing segment can be appended to by an incremental merge if:
+** fts3ExprIterate() callback to load the 'global' elements of a
+** FTS3_MATCHINFO_HITS matchinfo array. The global stats are those elements 
+** of the matchinfo array that are constant for all rows returned by the 
+** current query.
 **
-**   * It was initially created as an appendable segment (with all required
-**     space pre-allocated), and
+** Argument pCtx is actually a pointer to a struct of type MatchInfo. This
+** function populates Matchinfo.aMatchinfo[] as follows:
 **
-**   * The first key read from the input (arguments zKey and nKey) is 
-**     greater than the largest key currently stored in the potential
-**     output segment.
+**   for(iCol=0; iCol<nCol; iCol++){
+**     aMatchinfo[3*iPhrase*nCol + 3*iCol + 1] = X;
+**     aMatchinfo[3*iPhrase*nCol + 3*iCol + 2] = Y;
+**   }
+**
+** where X is the number of matches for phrase iPhrase is column iCol of all
+** rows of the table. Y is the number of rows for which column iCol contains
+** at least one instance of phrase iPhrase.
+**
+** If the phrase pExpr consists entirely of deferred tokens, then all X and
+** Y values are set to nDoc, where nDoc is the number of documents in the 
+** file system. This is done because the full-text index doclist is required
+** to calculate these values properly, and the full-text index doclist is
+** not available for deferred tokens.
 */
-static int fts3IncrmergeLoad(
-  Fts3Table *p,                   /* Fts3 table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level of input segments */
-  int iIdx,                       /* Index of candidate output segment */
-  const char *zKey,               /* First key to write */
-  int nKey,                       /* Number of bytes in nKey */
-  IncrmergeWriter *pWriter        /* Populate this object */
+static int fts3ExprGlobalHitsCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number (numbered from zero) */
+  void *pCtx                      /* Pointer to MatchInfo structure */
 ){
-  int rc;                         /* Return code */
-  sqlite3_stmt *pSelect = 0;      /* SELECT to read %_segdir entry */
+  MatchInfo *p = (MatchInfo *)pCtx;
+  return sqlite3Fts3EvalPhraseStats(
+      p->pCursor, pExpr, &p->aMatchinfo[3*iPhrase*p->nCol]
+  );
+}
 
-  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR, &pSelect, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_int64 iStart = 0;     /* Value of %_segdir.start_block */
-    sqlite3_int64 iLeafEnd = 0;   /* Value of %_segdir.leaves_end_block */
-    sqlite3_int64 iEnd = 0;       /* Value of %_segdir.end_block */
-    const char *aRoot = 0;        /* Pointer to %_segdir.root buffer */
-    int nRoot = 0;                /* Size of aRoot[] in bytes */
-    int rc2;                      /* Return code from sqlite3_reset() */
-    int bAppendable = 0;          /* Set to true if segment is appendable */
+/*
+** fts3ExprIterate() callback used to collect the "local" part of the
+** FTS3_MATCHINFO_HITS array. The local stats are those elements of the 
+** array that are different for each row returned by the query.
+*/
+static int fts3ExprLocalHitsCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number */
+  void *pCtx                      /* Pointer to MatchInfo structure */
+){
+  int rc = SQLITE_OK;
+  MatchInfo *p = (MatchInfo *)pCtx;
+  int iStart = iPhrase * p->nCol * 3;
+  int i;
 
-    /* Read the %_segdir entry for index iIdx absolute level (iAbsLevel+1) */
-    sqlite3_bind_int64(pSelect, 1, iAbsLevel+1);
-    sqlite3_bind_int(pSelect, 2, iIdx);
-    if( sqlite3_step(pSelect)==SQLITE_ROW ){
-      iStart = sqlite3_column_int64(pSelect, 1);
-      iLeafEnd = sqlite3_column_int64(pSelect, 2);
-      fts3ReadEndBlockField(pSelect, 3, &iEnd, &pWriter->nLeafData);
-      if( pWriter->nLeafData<0 ){
-        pWriter->nLeafData = pWriter->nLeafData * -1;
-      }
-      pWriter->bNoLeafData = (pWriter->nLeafData==0);
-      nRoot = sqlite3_column_bytes(pSelect, 4);
-      aRoot = sqlite3_column_blob(pSelect, 4);
+  for(i=0; i<p->nCol && rc==SQLITE_OK; i++){
+    char *pCsr;
+    rc = sqlite3Fts3EvalPhrasePoslist(p->pCursor, pExpr, i, &pCsr);
+    if( pCsr ){
+      p->aMatchinfo[iStart+i*3] = fts3ColumnlistCount(&pCsr);
     }else{
-      return sqlite3_reset(pSelect);
+      p->aMatchinfo[iStart+i*3] = 0;
     }
+  }
 
-    /* Check for the zero-length marker in the %_segments table */
-    rc = fts3IsAppendable(p, iEnd, &bAppendable);
+  return rc;
+}
 
-    /* Check that zKey/nKey is larger than the largest key the candidate */
-    if( rc==SQLITE_OK && bAppendable ){
-      char *aLeaf = 0;
-      int nLeaf = 0;
+static int fts3MatchinfoCheck(
+  Fts3Table *pTab, 
+  char cArg,
+  char **pzErr
+){
+  if( (cArg==FTS3_MATCHINFO_NPHRASE)
+   || (cArg==FTS3_MATCHINFO_NCOL)
+   || (cArg==FTS3_MATCHINFO_NDOC && pTab->bFts4)
+   || (cArg==FTS3_MATCHINFO_AVGLENGTH && pTab->bFts4)
+   || (cArg==FTS3_MATCHINFO_LENGTH && pTab->bHasDocsize)
+   || (cArg==FTS3_MATCHINFO_LCS)
+   || (cArg==FTS3_MATCHINFO_HITS)
+   || (cArg==FTS3_MATCHINFO_LHITS)
+   || (cArg==FTS3_MATCHINFO_LHITS_BM)
+  ){
+    return SQLITE_OK;
+  }
+  sqlite3Fts3ErrMsg(pzErr, "unrecognized matchinfo request: %c", cArg);
+  return SQLITE_ERROR;
+}
 
-      rc = sqlite3Fts3ReadBlock(p, iLeafEnd, &aLeaf, &nLeaf, 0);
-      if( rc==SQLITE_OK ){
-        NodeReader reader;
-        for(rc = nodeReaderInit(&reader, aLeaf, nLeaf);
-            rc==SQLITE_OK && reader.aNode;
-            rc = nodeReaderNext(&reader)
-        ){
-          assert( reader.aNode );
-        }
-        if( fts3TermCmp(zKey, nKey, reader.term.a, reader.term.n)<=0 ){
-          bAppendable = 0;
-        }
-        nodeReaderRelease(&reader);
-      }
-      sqlite3_free(aLeaf);
-    }
+static int fts3MatchinfoSize(MatchInfo *pInfo, char cArg){
+  int nVal;                       /* Number of integers output by cArg */
 
-    if( rc==SQLITE_OK && bAppendable ){
-      /* It is possible to append to this segment. Set up the IncrmergeWriter
-      ** object to do so.  */
-      int i;
-      int nHeight = (int)aRoot[0];
-      NodeWriter *pNode;
+  switch( cArg ){
+    case FTS3_MATCHINFO_NDOC:
+    case FTS3_MATCHINFO_NPHRASE: 
+    case FTS3_MATCHINFO_NCOL: 
+      nVal = 1;
+      break;
 
-      pWriter->nLeafEst = (int)((iEnd - iStart) + 1)/FTS_MAX_APPENDABLE_HEIGHT;
-      pWriter->iStart = iStart;
-      pWriter->iEnd = iEnd;
-      pWriter->iAbsLevel = iAbsLevel;
-      pWriter->iIdx = iIdx;
+    case FTS3_MATCHINFO_AVGLENGTH:
+    case FTS3_MATCHINFO_LENGTH:
+    case FTS3_MATCHINFO_LCS:
+      nVal = pInfo->nCol;
+      break;
 
-      for(i=nHeight+1; i<FTS_MAX_APPENDABLE_HEIGHT; i++){
-        pWriter->aNodeWriter[i].iBlock = pWriter->iStart + i*pWriter->nLeafEst;
-      }
+    case FTS3_MATCHINFO_LHITS:
+      nVal = pInfo->nCol * pInfo->nPhrase;
+      break;
 
-      pNode = &pWriter->aNodeWriter[nHeight];
-      pNode->iBlock = pWriter->iStart + pWriter->nLeafEst*nHeight;
-      blobGrowBuffer(&pNode->block, MAX(nRoot, p->nNodeSize), &rc);
-      if( rc==SQLITE_OK ){
-        memcpy(pNode->block.a, aRoot, nRoot);
-        pNode->block.n = nRoot;
-      }
+    case FTS3_MATCHINFO_LHITS_BM:
+      nVal = pInfo->nPhrase * ((pInfo->nCol + 31) / 32);
+      break;
 
-      for(i=nHeight; i>=0 && rc==SQLITE_OK; i--){
-        NodeReader reader;
-        pNode = &pWriter->aNodeWriter[i];
+    default:
+      assert( cArg==FTS3_MATCHINFO_HITS );
+      nVal = pInfo->nCol * pInfo->nPhrase * 3;
+      break;
+  }
 
-        rc = nodeReaderInit(&reader, pNode->block.a, pNode->block.n);
-        while( reader.aNode && rc==SQLITE_OK ) rc = nodeReaderNext(&reader);
-        blobGrowBuffer(&pNode->key, reader.term.n, &rc);
-        if( rc==SQLITE_OK ){
-          memcpy(pNode->key.a, reader.term.a, reader.term.n);
-          pNode->key.n = reader.term.n;
-          if( i>0 ){
-            char *aBlock = 0;
-            int nBlock = 0;
-            pNode = &pWriter->aNodeWriter[i-1];
-            pNode->iBlock = reader.iChild;
-            rc = sqlite3Fts3ReadBlock(p, reader.iChild, &aBlock, &nBlock, 0);
-            blobGrowBuffer(&pNode->block, MAX(nBlock, p->nNodeSize), &rc);
-            if( rc==SQLITE_OK ){
-              memcpy(pNode->block.a, aBlock, nBlock);
-              pNode->block.n = nBlock;
-            }
-            sqlite3_free(aBlock);
-          }
-        }
-        nodeReaderRelease(&reader);
-      }
-    }
+  return nVal;
+}
 
-    rc2 = sqlite3_reset(pSelect);
-    if( rc==SQLITE_OK ) rc = rc2;
+static int fts3MatchinfoSelectDoctotal(
+  Fts3Table *pTab,
+  sqlite3_stmt **ppStmt,
+  sqlite3_int64 *pnDoc,
+  const char **paLen
+){
+  sqlite3_stmt *pStmt;
+  const char *a;
+  sqlite3_int64 nDoc;
+
+  if( !*ppStmt ){
+    int rc = sqlite3Fts3SelectDoctotal(pTab, ppStmt);
+    if( rc!=SQLITE_OK ) return rc;
   }
+  pStmt = *ppStmt;
+  assert( sqlite3_data_count(pStmt)==1 );
 
-  return rc;
+  a = sqlite3_column_blob(pStmt, 0);
+  a += sqlite3Fts3GetVarint(a, &nDoc);
+  if( nDoc==0 ) return FTS_CORRUPT_VTAB;
+  *pnDoc = (u32)nDoc;
+
+  if( paLen ) *paLen = a;
+  return SQLITE_OK;
 }
 
 /*
-** Determine the largest segment index value that exists within absolute
-** level iAbsLevel+1. If no error occurs, set *piIdx to this value plus
-** one before returning SQLITE_OK. Or, if there are no segments at all 
-** within level iAbsLevel, set *piIdx to zero.
-**
-** If an error occurs, return an SQLite error code. The final value of
-** *piIdx is undefined in this case.
+** An instance of the following structure is used to store state while 
+** iterating through a multi-column position-list corresponding to the
+** hits for a single phrase on a single row in order to calculate the
+** values for a matchinfo() FTS3_MATCHINFO_LCS request.
 */
-static int fts3IncrmergeOutputIdx( 
-  Fts3Table *p,                   /* FTS Table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute index of input segments */
-  int *piIdx                      /* OUT: Next free index at iAbsLevel+1 */
+typedef struct LcsIterator LcsIterator;
+struct LcsIterator {
+  Fts3Expr *pExpr;                /* Pointer to phrase expression */
+  int iPosOffset;                 /* Tokens count up to end of this phrase */
+  char *pRead;                    /* Cursor used to iterate through aDoclist */
+  int iPos;                       /* Current position */
+};
+
+/* 
+** If LcsIterator.iCol is set to the following value, the iterator has
+** finished iterating through all offsets for all columns.
+*/
+#define LCS_ITERATOR_FINISHED 0x7FFFFFFF;
+
+static int fts3MatchinfoLcsCb(
+  Fts3Expr *pExpr,                /* Phrase expression node */
+  int iPhrase,                    /* Phrase number (numbered from zero) */
+  void *pCtx                      /* Pointer to MatchInfo structure */
 ){
-  int rc;
-  sqlite3_stmt *pOutputIdx = 0;   /* SQL used to find output index */
+  LcsIterator *aIter = (LcsIterator *)pCtx;
+  aIter[iPhrase].pExpr = pExpr;
+  return SQLITE_OK;
+}
 
-  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENT_INDEX, &pOutputIdx, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pOutputIdx, 1, iAbsLevel+1);
-    sqlite3_step(pOutputIdx);
-    *piIdx = sqlite3_column_int(pOutputIdx, 0);
-    rc = sqlite3_reset(pOutputIdx);
+/*
+** Advance the iterator passed as an argument to the next position. Return
+** 1 if the iterator is at EOF or if it now points to the start of the
+** position list for the next column.
+*/
+static int fts3LcsIteratorAdvance(LcsIterator *pIter){
+  char *pRead = pIter->pRead;
+  sqlite3_int64 iRead;
+  int rc = 0;
+
+  pRead += sqlite3Fts3GetVarint(pRead, &iRead);
+  if( iRead==0 || iRead==1 ){
+    pRead = 0;
+    rc = 1;
+  }else{
+    pIter->iPos += (int)(iRead-2);
   }
 
+  pIter->pRead = pRead;
   return rc;
 }
-
-/* 
-** Allocate an appendable output segment on absolute level iAbsLevel+1
-** with idx value iIdx.
-**
-** In the %_segdir table, a segment is defined by the values in three
-** columns:
-**
-**     start_block
-**     leaves_end_block
-**     end_block
-**
-** When an appendable segment is allocated, it is estimated that the
-** maximum number of leaf blocks that may be required is the sum of the
-** number of leaf blocks consumed by the input segments, plus the number
-** of input segments, multiplied by two. This value is stored in stack 
-** variable nLeafEst.
+  
+/*
+** This function implements the FTS3_MATCHINFO_LCS matchinfo() flag. 
 **
-** A total of 16*nLeafEst blocks are allocated when an appendable segment
-** is created ((1 + end_block - start_block)==16*nLeafEst). The contiguous
-** array of leaf nodes starts at the first block allocated. The array
-** of interior nodes that are parents of the leaf nodes start at block
-** (start_block + (1 + end_block - start_block) / 16). And so on.
+** If the call is successful, the longest-common-substring lengths for each
+** column are written into the first nCol elements of the pInfo->aMatchinfo[] 
+** array before returning. SQLITE_OK is returned in this case.
 **
-** In the actual code below, the value "16" is replaced with the 
-** pre-processor macro FTS_MAX_APPENDABLE_HEIGHT.
+** Otherwise, if an error occurs, an SQLite error code is returned and the
+** data written to the first nCol elements of pInfo->aMatchinfo[] is 
+** undefined.
 */
-static int fts3IncrmergeWriter( 
-  Fts3Table *p,                   /* Fts3 table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level of input segments */
-  int iIdx,                       /* Index of new output segment */
-  Fts3MultiSegReader *pCsr,       /* Cursor that data will be read from */
-  IncrmergeWriter *pWriter        /* Populate this object */
-){
-  int rc;                         /* Return Code */
-  int i;                          /* Iterator variable */
-  int nLeafEst = 0;               /* Blocks allocated for leaf nodes */
-  sqlite3_stmt *pLeafEst = 0;     /* SQL used to determine nLeafEst */
-  sqlite3_stmt *pFirstBlock = 0;  /* SQL used to determine first block */
+static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
+  LcsIterator *aIter;
+  int i;
+  int iCol;
+  int nToken = 0;
 
-  /* Calculate nLeafEst. */
-  rc = fts3SqlStmt(p, SQL_MAX_LEAF_NODE_ESTIMATE, &pLeafEst, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pLeafEst, 1, iAbsLevel);
-    sqlite3_bind_int64(pLeafEst, 2, pCsr->nSegment);
-    if( SQLITE_ROW==sqlite3_step(pLeafEst) ){
-      nLeafEst = sqlite3_column_int(pLeafEst, 0);
-    }
-    rc = sqlite3_reset(pLeafEst);
+  /* Allocate and populate the array of LcsIterator objects. The array
+  ** contains one element for each matchable phrase in the query.
+  **/
+  aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
+  if( !aIter ) return SQLITE_NOMEM;
+  memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
+  (void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);
+
+  for(i=0; i<pInfo->nPhrase; i++){
+    LcsIterator *pIter = &aIter[i];
+    nToken -= pIter->pExpr->pPhrase->nToken;
+    pIter->iPosOffset = nToken;
   }
-  if( rc!=SQLITE_OK ) return rc;
 
-  /* Calculate the first block to use in the output segment */
-  rc = fts3SqlStmt(p, SQL_NEXT_SEGMENTS_ID, &pFirstBlock, 0);
-  if( rc==SQLITE_OK ){
-    if( SQLITE_ROW==sqlite3_step(pFirstBlock) ){
-      pWriter->iStart = sqlite3_column_int64(pFirstBlock, 0);
-      pWriter->iEnd = pWriter->iStart - 1;
-      pWriter->iEnd += nLeafEst * FTS_MAX_APPENDABLE_HEIGHT;
+  for(iCol=0; iCol<pInfo->nCol; iCol++){
+    int nLcs = 0;                 /* LCS value for this column */
+    int nLive = 0;                /* Number of iterators in aIter not at EOF */
+
+    for(i=0; i<pInfo->nPhrase; i++){
+      int rc;
+      LcsIterator *pIt = &aIter[i];
+      rc = sqlite3Fts3EvalPhrasePoslist(pCsr, pIt->pExpr, iCol, &pIt->pRead);
+      if( rc!=SQLITE_OK ) return rc;
+      if( pIt->pRead ){
+        pIt->iPos = pIt->iPosOffset;
+        fts3LcsIteratorAdvance(&aIter[i]);
+        nLive++;
+      }
     }
-    rc = sqlite3_reset(pFirstBlock);
-  }
-  if( rc!=SQLITE_OK ) return rc;
 
-  /* Insert the marker in the %_segments table to make sure nobody tries
-  ** to steal the space just allocated. This is also used to identify 
-  ** appendable segments.  */
-  rc = fts3WriteSegment(p, pWriter->iEnd, 0, 0);
-  if( rc!=SQLITE_OK ) return rc;
+    while( nLive>0 ){
+      LcsIterator *pAdv = 0;      /* The iterator to advance by one position */
+      int nThisLcs = 0;           /* LCS for the current iterator positions */
 
-  pWriter->iAbsLevel = iAbsLevel;
-  pWriter->nLeafEst = nLeafEst;
-  pWriter->iIdx = iIdx;
+      for(i=0; i<pInfo->nPhrase; i++){
+        LcsIterator *pIter = &aIter[i];
+        if( pIter->pRead==0 ){
+          /* This iterator is already at EOF for this column. */
+          nThisLcs = 0;
+        }else{
+          if( pAdv==0 || pIter->iPos<pAdv->iPos ){
+            pAdv = pIter;
+          }
+          if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){
+            nThisLcs++;
+          }else{
+            nThisLcs = 1;
+          }
+          if( nThisLcs>nLcs ) nLcs = nThisLcs;
+        }
+      }
+      if( fts3LcsIteratorAdvance(pAdv) ) nLive--;
+    }
 
-  /* Set up the array of NodeWriter objects */
-  for(i=0; i<FTS_MAX_APPENDABLE_HEIGHT; i++){
-    pWriter->aNodeWriter[i].iBlock = pWriter->iStart + i*pWriter->nLeafEst;
+    pInfo->aMatchinfo[iCol] = nLcs;
   }
+
+  sqlite3_free(aIter);
   return SQLITE_OK;
 }
 
 /*
-** Remove an entry from the %_segdir table. This involves running the 
-** following two statements:
+** Populate the buffer pInfo->aMatchinfo[] with an array of integers to
+** be returned by the matchinfo() function. Argument zArg contains the 
+** format string passed as the second argument to matchinfo (or the
+** default value "pcx" if no second argument was specified). The format
+** string has already been validated and the pInfo->aMatchinfo[] array
+** is guaranteed to be large enough for the output.
 **
-**   DELETE FROM %_segdir WHERE level = :iAbsLevel AND idx = :iIdx
-**   UPDATE %_segdir SET idx = idx - 1 WHERE level = :iAbsLevel AND idx > :iIdx
+** If bGlobal is true, then populate all fields of the matchinfo() output.
+** If it is false, then assume that those fields that do not change between
+** rows (i.e. FTS3_MATCHINFO_NPHRASE, NCOL, NDOC, AVGLENGTH and part of HITS)
+** have already been populated.
 **
-** The DELETE statement removes the specific %_segdir level. The UPDATE 
-** statement ensures that the remaining segments have contiguously allocated
-** idx values.
+** Return SQLITE_OK if successful, or an SQLite error code if an error 
+** occurs. If a value other than SQLITE_OK is returned, the state the
+** pInfo->aMatchinfo[] buffer is left in is undefined.
 */
-static int fts3RemoveSegdirEntry(
-  Fts3Table *p,                   /* FTS3 table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level to delete from */
-  int iIdx                        /* Index of %_segdir entry to delete */
+static int fts3MatchinfoValues(
+  Fts3Cursor *pCsr,               /* FTS3 cursor object */
+  int bGlobal,                    /* True to grab the global stats */
+  MatchInfo *pInfo,               /* Matchinfo context object */
+  const char *zArg                /* Matchinfo format string */
 ){
-  int rc;                         /* Return code */
-  sqlite3_stmt *pDelete = 0;      /* DELETE statement */
+  int rc = SQLITE_OK;
+  int i;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  sqlite3_stmt *pSelect = 0;
 
-  rc = fts3SqlStmt(p, SQL_DELETE_SEGDIR_ENTRY, &pDelete, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pDelete, 1, iAbsLevel);
-    sqlite3_bind_int(pDelete, 2, iIdx);
-    sqlite3_step(pDelete);
-    rc = sqlite3_reset(pDelete);
-  }
+  for(i=0; rc==SQLITE_OK && zArg[i]; i++){
+    pInfo->flag = zArg[i];
+    switch( zArg[i] ){
+      case FTS3_MATCHINFO_NPHRASE:
+        if( bGlobal ) pInfo->aMatchinfo[0] = pInfo->nPhrase;
+        break;
 
-  return rc;
-}
+      case FTS3_MATCHINFO_NCOL:
+        if( bGlobal ) pInfo->aMatchinfo[0] = pInfo->nCol;
+        break;
+        
+      case FTS3_MATCHINFO_NDOC:
+        if( bGlobal ){
+          sqlite3_int64 nDoc = 0;
+          rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &nDoc, 0);
+          pInfo->aMatchinfo[0] = (u32)nDoc;
+        }
+        break;
 
-/*
-** One or more segments have just been removed from absolute level iAbsLevel.
-** Update the 'idx' values of the remaining segments in the level so that
-** the idx values are a contiguous sequence starting from 0.
-*/
-static int fts3RepackSegdirLevel(
-  Fts3Table *p,                   /* FTS3 table handle */
-  sqlite3_int64 iAbsLevel         /* Absolute level to repack */
-){
-  int rc;                         /* Return code */
-  int *aIdx = 0;                  /* Array of remaining idx values */
-  int nIdx = 0;                   /* Valid entries in aIdx[] */
-  int nAlloc = 0;                 /* Allocated size of aIdx[] */
-  int i;                          /* Iterator variable */
-  sqlite3_stmt *pSelect = 0;      /* Select statement to read idx values */
-  sqlite3_stmt *pUpdate = 0;      /* Update statement to modify idx values */
+      case FTS3_MATCHINFO_AVGLENGTH: 
+        if( bGlobal ){
+          sqlite3_int64 nDoc;     /* Number of rows in table */
+          const char *a;          /* Aggregate column length array */
 
-  rc = fts3SqlStmt(p, SQL_SELECT_INDEXES, &pSelect, 0);
-  if( rc==SQLITE_OK ){
-    int rc2;
-    sqlite3_bind_int64(pSelect, 1, iAbsLevel);
-    while( SQLITE_ROW==sqlite3_step(pSelect) ){
-      if( nIdx>=nAlloc ){
-        int *aNew;
-        nAlloc += 16;
-        aNew = sqlite3_realloc(aIdx, nAlloc*sizeof(int));
-        if( !aNew ){
-          rc = SQLITE_NOMEM;
-          break;
+          rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &nDoc, &a);
+          if( rc==SQLITE_OK ){
+            int iCol;
+            for(iCol=0; iCol<pInfo->nCol; iCol++){
+              u32 iVal;
+              sqlite3_int64 nToken;
+              a += sqlite3Fts3GetVarint(a, &nToken);
+              iVal = (u32)(((u32)(nToken&0xffffffff)+nDoc/2)/nDoc);
+              pInfo->aMatchinfo[iCol] = iVal;
+            }
+          }
         }
-        aIdx = aNew;
+        break;
+
+      case FTS3_MATCHINFO_LENGTH: {
+        sqlite3_stmt *pSelectDocsize = 0;
+        rc = sqlite3Fts3SelectDocsize(pTab, pCsr->iPrevId, &pSelectDocsize);
+        if( rc==SQLITE_OK ){
+          int iCol;
+          const char *a = sqlite3_column_blob(pSelectDocsize, 0);
+          for(iCol=0; iCol<pInfo->nCol; iCol++){
+            sqlite3_int64 nToken;
+            a += sqlite3Fts3GetVarint(a, &nToken);
+            pInfo->aMatchinfo[iCol] = (u32)nToken;
+          }
+        }
+        sqlite3_reset(pSelectDocsize);
+        break;
       }
-      aIdx[nIdx++] = sqlite3_column_int(pSelect, 0);
-    }
-    rc2 = sqlite3_reset(pSelect);
-    if( rc==SQLITE_OK ) rc = rc2;
-  }
 
-  if( rc==SQLITE_OK ){
-    rc = fts3SqlStmt(p, SQL_SHIFT_SEGDIR_ENTRY, &pUpdate, 0);
-  }
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pUpdate, 2, iAbsLevel);
-  }
+      case FTS3_MATCHINFO_LCS:
+        rc = fts3ExprLoadDoclists(pCsr, 0, 0);
+        if( rc==SQLITE_OK ){
+          rc = fts3MatchinfoLcs(pCsr, pInfo);
+        }
+        break;
 
-  assert( p->bIgnoreSavepoint==0 );
-  p->bIgnoreSavepoint = 1;
-  for(i=0; rc==SQLITE_OK && i<nIdx; i++){
-    if( aIdx[i]!=i ){
-      sqlite3_bind_int(pUpdate, 3, aIdx[i]);
-      sqlite3_bind_int(pUpdate, 1, i);
-      sqlite3_step(pUpdate);
-      rc = sqlite3_reset(pUpdate);
+      case FTS3_MATCHINFO_LHITS_BM:
+      case FTS3_MATCHINFO_LHITS: {
+        int nZero = fts3MatchinfoSize(pInfo, zArg[i]) * sizeof(u32);
+        memset(pInfo->aMatchinfo, 0, nZero);
+        fts3ExprLHitGather(pCsr->pExpr, pInfo);
+        break;
+      }
+
+      default: {
+        Fts3Expr *pExpr;
+        assert( zArg[i]==FTS3_MATCHINFO_HITS );
+        pExpr = pCsr->pExpr;
+        rc = fts3ExprLoadDoclists(pCsr, 0, 0);
+        if( rc!=SQLITE_OK ) break;
+        if( bGlobal ){
+          if( pCsr->pDeferred ){
+            rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &pInfo->nDoc, 0);
+            if( rc!=SQLITE_OK ) break;
+          }
+          rc = fts3ExprIterate(pExpr, fts3ExprGlobalHitsCb,(void*)pInfo);
+          sqlite3Fts3EvalTestDeferred(pCsr, &rc);
+          if( rc!=SQLITE_OK ) break;
+        }
+        (void)fts3ExprIterate(pExpr, fts3ExprLocalHitsCb,(void*)pInfo);
+        break;
+      }
     }
+
+    pInfo->aMatchinfo += fts3MatchinfoSize(pInfo, zArg[i]);
   }
-  p->bIgnoreSavepoint = 0;
 
-  sqlite3_free(aIdx);
+  sqlite3_reset(pSelect);
   return rc;
 }
 
-static void fts3StartNode(Blob *pNode, int iHeight, sqlite3_int64 iChild){
-  pNode->a[0] = (char)iHeight;
-  if( iChild ){
-    assert( pNode->nAlloc>=1+sqlite3Fts3VarintLen(iChild) );
-    pNode->n = 1 + sqlite3Fts3PutVarint(&pNode->a[1], iChild);
-  }else{
-    assert( pNode->nAlloc>=1 );
-    pNode->n = 1;
-  }
-}
 
 /*
-** The first two arguments are a pointer to and the size of a segment b-tree
-** node. The node may be a leaf or an internal node.
-**
-** This function creates a new node image in blob object *pNew by copying
-** all terms that are greater than or equal to zTerm/nTerm (for leaf nodes)
-** or greater than zTerm/nTerm (for internal nodes) from aNode/nNode.
+** Populate pCsr->aMatchinfo[] with data for the current row. The 
+** 'matchinfo' data is an array of 32-bit unsigned integers (C type u32).
 */
-static int fts3TruncateNode(
-  const char *aNode,              /* Current node image */
-  int nNode,                      /* Size of aNode in bytes */
-  Blob *pNew,                     /* OUT: Write new node image here */
-  const char *zTerm,              /* Omit all terms smaller than this */
-  int nTerm,                      /* Size of zTerm in bytes */
-  sqlite3_int64 *piBlock          /* OUT: Block number in next layer down */
+static void fts3GetMatchinfo(
+  sqlite3_context *pCtx,        /* Return results here */
+  Fts3Cursor *pCsr,               /* FTS3 Cursor object */
+  const char *zArg                /* Second argument to matchinfo() function */
 ){
-  NodeReader reader;              /* Reader object */
-  Blob prev = {0, 0, 0};          /* Previous term written to new node */
-  int rc = SQLITE_OK;             /* Return code */
-  int bLeaf = aNode[0]=='\0';     /* True for a leaf node */
+  MatchInfo sInfo;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  int rc = SQLITE_OK;
+  int bGlobal = 0;                /* Collect 'global' stats as well as local */
 
-  /* Allocate required output space */
-  blobGrowBuffer(pNew, nNode, &rc);
-  if( rc!=SQLITE_OK ) return rc;
-  pNew->n = 0;
+  u32 *aOut = 0;
+  void (*xDestroyOut)(void*) = 0;
 
-  /* Populate new node buffer */
-  for(rc = nodeReaderInit(&reader, aNode, nNode); 
-      rc==SQLITE_OK && reader.aNode; 
-      rc = nodeReaderNext(&reader)
-  ){
-    if( pNew->n==0 ){
-      int res = fts3TermCmp(reader.term.a, reader.term.n, zTerm, nTerm);
-      if( res<0 || (bLeaf==0 && res==0) ) continue;
-      fts3StartNode(pNew, (int)aNode[0], reader.iChild);
-      *piBlock = reader.iChild;
-    }
-    rc = fts3AppendToNode(
-        pNew, &prev, reader.term.a, reader.term.n,
-        reader.aDoclist, reader.nDoclist
-    );
-    if( rc!=SQLITE_OK ) break;
-  }
-  if( pNew->n==0 ){
-    fts3StartNode(pNew, (int)aNode[0], reader.iChild);
-    *piBlock = reader.iChild;
+  memset(&sInfo, 0, sizeof(MatchInfo));
+  sInfo.pCursor = pCsr;
+  sInfo.nCol = pTab->nColumn;
+
+  /* If there is cached matchinfo() data, but the format string for the 
+  ** cache does not match the format string for this request, discard 
+  ** the cached data. */
+  if( pCsr->pMIBuffer && strcmp(pCsr->pMIBuffer->zMatchinfo, zArg) ){
+    sqlite3Fts3MIBufferFree(pCsr->pMIBuffer);
+    pCsr->pMIBuffer = 0;
   }
-  assert( pNew->n<=pNew->nAlloc );
 
-  nodeReaderRelease(&reader);
-  sqlite3_free(prev.a);
-  return rc;
-}
+  /* If Fts3Cursor.pMIBuffer is NULL, then this is the first time the
+  ** matchinfo function has been called for this query. In this case 
+  ** allocate the array used to accumulate the matchinfo data and
+  ** initialize those elements that are constant for every row.
+  */
+  if( pCsr->pMIBuffer==0 ){
+    int nMatchinfo = 0;           /* Number of u32 elements in match-info */
+    int i;                        /* Used to iterate through zArg */
 
-/*
-** Remove all terms smaller than zTerm/nTerm from segment iIdx in absolute 
-** level iAbsLevel. This may involve deleting entries from the %_segments
-** table, and modifying existing entries in both the %_segments and %_segdir
-** tables.
-**
-** SQLITE_OK is returned if the segment is updated successfully. Or an
-** SQLite error code otherwise.
-*/
-static int fts3TruncateSegment(
-  Fts3Table *p,                   /* FTS3 table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level of segment to modify */
-  int iIdx,                       /* Index within level of segment to modify */
-  const char *zTerm,              /* Remove terms smaller than this */
-  int nTerm                      /* Number of bytes in buffer zTerm */
-){
-  int rc = SQLITE_OK;             /* Return code */
-  Blob root = {0,0,0};            /* New root page image */
-  Blob block = {0,0,0};           /* Buffer used for any other block */
-  sqlite3_int64 iBlock = 0;       /* Block id */
-  sqlite3_int64 iNewStart = 0;    /* New value for iStartBlock */
-  sqlite3_int64 iOldStart = 0;    /* Old value for iStartBlock */
-  sqlite3_stmt *pFetch = 0;       /* Statement used to fetch segdir */
+    /* Determine the number of phrases in the query */
+    pCsr->nPhrase = fts3ExprPhraseCount(pCsr->pExpr);
+    sInfo.nPhrase = pCsr->nPhrase;
 
-  rc = fts3SqlStmt(p, SQL_SELECT_SEGDIR, &pFetch, 0);
-  if( rc==SQLITE_OK ){
-    int rc2;                      /* sqlite3_reset() return code */
-    sqlite3_bind_int64(pFetch, 1, iAbsLevel);
-    sqlite3_bind_int(pFetch, 2, iIdx);
-    if( SQLITE_ROW==sqlite3_step(pFetch) ){
-      const char *aRoot = sqlite3_column_blob(pFetch, 4);
-      int nRoot = sqlite3_column_bytes(pFetch, 4);
-      iOldStart = sqlite3_column_int64(pFetch, 1);
-      rc = fts3TruncateNode(aRoot, nRoot, &root, zTerm, nTerm, &iBlock);
+    /* Determine the number of integers in the buffer returned by this call. */
+    for(i=0; zArg[i]; i++){
+      char *zErr = 0;
+      if( fts3MatchinfoCheck(pTab, zArg[i], &zErr) ){
+        sqlite3_result_error(pCtx, zErr, -1);
+        sqlite3_free(zErr);
+        return;
+      }
+      nMatchinfo += fts3MatchinfoSize(&sInfo, zArg[i]);
     }
-    rc2 = sqlite3_reset(pFetch);
-    if( rc==SQLITE_OK ) rc = rc2;
-  }
 
-  while( rc==SQLITE_OK && iBlock ){
-    char *aBlock = 0;
-    int nBlock = 0;
-    iNewStart = iBlock;
+    /* Allocate space for Fts3Cursor.aMatchinfo[] and Fts3Cursor.zMatchinfo. */
+    pCsr->pMIBuffer = fts3MIBufferNew(nMatchinfo, zArg);
+    if( !pCsr->pMIBuffer ) rc = SQLITE_NOMEM;
 
-    rc = sqlite3Fts3ReadBlock(p, iBlock, &aBlock, &nBlock, 0);
-    if( rc==SQLITE_OK ){
-      rc = fts3TruncateNode(aBlock, nBlock, &block, zTerm, nTerm, &iBlock);
-    }
-    if( rc==SQLITE_OK ){
-      rc = fts3WriteSegment(p, iNewStart, block.a, block.n);
-    }
-    sqlite3_free(aBlock);
+    pCsr->isMatchinfoNeeded = 1;
+    bGlobal = 1;
   }
 
-  /* Variable iNewStart now contains the first valid leaf node. */
-  if( rc==SQLITE_OK && iNewStart ){
-    sqlite3_stmt *pDel = 0;
-    rc = fts3SqlStmt(p, SQL_DELETE_SEGMENTS_RANGE, &pDel, 0);
-    if( rc==SQLITE_OK ){
-      sqlite3_bind_int64(pDel, 1, iOldStart);
-      sqlite3_bind_int64(pDel, 2, iNewStart-1);
-      sqlite3_step(pDel);
-      rc = sqlite3_reset(pDel);
+  if( rc==SQLITE_OK ){
+    xDestroyOut = fts3MIBufferAlloc(pCsr->pMIBuffer, &aOut);
+    if( xDestroyOut==0 ){
+      rc = SQLITE_NOMEM;
     }
   }
 
   if( rc==SQLITE_OK ){
-    sqlite3_stmt *pChomp = 0;
-    rc = fts3SqlStmt(p, SQL_CHOMP_SEGDIR, &pChomp, 0);
-    if( rc==SQLITE_OK ){
-      sqlite3_bind_int64(pChomp, 1, iNewStart);
-      sqlite3_bind_blob(pChomp, 2, root.a, root.n, SQLITE_STATIC);
-      sqlite3_bind_int64(pChomp, 3, iAbsLevel);
-      sqlite3_bind_int(pChomp, 4, iIdx);
-      sqlite3_step(pChomp);
-      rc = sqlite3_reset(pChomp);
+    sInfo.aMatchinfo = aOut;
+    sInfo.nPhrase = pCsr->nPhrase;
+    rc = fts3MatchinfoValues(pCsr, bGlobal, &sInfo, zArg);
+    if( bGlobal ){
+      fts3MIBufferSetGlobal(pCsr->pMIBuffer);
     }
   }
 
-  sqlite3_free(root.a);
-  sqlite3_free(block.a);
-  return rc;
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx, rc);
+    if( xDestroyOut ) xDestroyOut(aOut);
+  }else{
+    int n = pCsr->pMIBuffer->nElem * sizeof(u32);
+    sqlite3_result_blob(pCtx, aOut, n, xDestroyOut);
+  }
 }
 
 /*
-** This function is called after an incrmental-merge operation has run to
-** merge (or partially merge) two or more segments from absolute level
-** iAbsLevel.
-**
-** Each input segment is either removed from the db completely (if all of
-** its data was copied to the output segment by the incrmerge operation)
-** or modified in place so that it no longer contains those entries that
-** have been duplicated in the output segment.
+** Implementation of snippet() function.
 */
-static int fts3IncrmergeChomp(
-  Fts3Table *p,                   /* FTS table handle */
-  sqlite3_int64 iAbsLevel,        /* Absolute level containing segments */
-  Fts3MultiSegReader *pCsr,       /* Chomp all segments opened by this cursor */
-  int *pnRem                      /* Number of segments not deleted */
+SQLITE_PRIVATE void sqlite3Fts3Snippet(
+  sqlite3_context *pCtx,          /* SQLite function call context */
+  Fts3Cursor *pCsr,               /* Cursor object */
+  const char *zStart,             /* Snippet start text - "<b>" */
+  const char *zEnd,               /* Snippet end text - "</b>" */
+  const char *zEllipsis,          /* Snippet ellipsis text - "<b>...</b>" */
+  int iCol,                       /* Extract snippet from this column */
+  int nToken                      /* Approximate number of tokens in snippet */
 ){
-  int i;
-  int nRem = 0;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
   int rc = SQLITE_OK;
+  int i;
+  StrBuffer res = {0, 0, 0};
 
-  for(i=pCsr->nSegment-1; i>=0 && rc==SQLITE_OK; i--){
-    Fts3SegReader *pSeg = 0;
-    int j;
+  /* The returned text includes up to four fragments of text extracted from
+  ** the data in the current row. The first iteration of the for(...) loop
+  ** below attempts to locate a single fragment of text nToken tokens in 
+  ** size that contains at least one instance of all phrases in the query
+  ** expression that appear in the current row. If such a fragment of text
+  ** cannot be found, the second iteration of the loop attempts to locate
+  ** a pair of fragments, and so on.
+  */
+  int nSnippet = 0;               /* Number of fragments in this snippet */
+  SnippetFragment aSnippet[4];    /* Maximum of 4 fragments per snippet */
+  int nFToken = -1;               /* Number of tokens in each fragment */
 
-    /* Find the Fts3SegReader object with Fts3SegReader.iIdx==i. It is hiding
-    ** somewhere in the pCsr->apSegment[] array.  */
-    for(j=0; ALWAYS(j<pCsr->nSegment); j++){
-      pSeg = pCsr->apSegment[j];
-      if( pSeg->iIdx==i ) break;
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
+  }
+
+  for(nSnippet=1; 1; nSnippet++){
+
+    int iSnip;                    /* Loop counter 0..nSnippet-1 */
+    u64 mCovered = 0;             /* Bitmask of phrases covered by snippet */
+    u64 mSeen = 0;                /* Bitmask of phrases seen by BestSnippet() */
+
+    if( nToken>=0 ){
+      nFToken = (nToken+nSnippet-1) / nSnippet;
+    }else{
+      nFToken = -1 * nToken;
     }
-    assert( j<pCsr->nSegment && pSeg->iIdx==i );
 
-    if( pSeg->aNode==0 ){
-      /* Seg-reader is at EOF. Remove the entire input segment. */
-      rc = fts3DeleteSegment(p, pSeg);
-      if( rc==SQLITE_OK ){
-        rc = fts3RemoveSegdirEntry(p, iAbsLevel, pSeg->iIdx);
+    for(iSnip=0; iSnip<nSnippet; iSnip++){
+      int iBestScore = -1;        /* Best score of columns checked so far */
+      int iRead;                  /* Used to iterate through columns */
+      SnippetFragment *pFragment = &aSnippet[iSnip];
+
+      memset(pFragment, 0, sizeof(*pFragment));
+
+      /* Loop through all columns of the table being considered for snippets.
+      ** If the iCol argument to this function was negative, this means all
+      ** columns of the FTS3 table. Otherwise, only column iCol is considered.
+      */
+      for(iRead=0; iRead<pTab->nColumn; iRead++){
+        SnippetFragment sF = {0, 0, 0, 0};
+        int iS = 0;
+        if( iCol>=0 && iRead!=iCol ) continue;
+
+        /* Find the best snippet of nFToken tokens in column iRead. */
+        rc = fts3BestSnippet(nFToken, pCsr, iRead, mCovered, &mSeen, &sF, &iS);
+        if( rc!=SQLITE_OK ){
+          goto snippet_out;
+        }
+        if( iS>iBestScore ){
+          *pFragment = sF;
+          iBestScore = iS;
+        }
       }
-      *pnRem = 0;
-    }else{
-      /* The incremental merge did not copy all the data from this 
-      ** segment to the upper level. The segment is modified in place
-      ** so that it contains no keys smaller than zTerm/nTerm. */ 
-      const char *zTerm = pSeg->zTerm;
-      int nTerm = pSeg->nTerm;
-      rc = fts3TruncateSegment(p, iAbsLevel, pSeg->iIdx, zTerm, nTerm);
-      nRem++;
+
+      mCovered |= pFragment->covered;
     }
+
+    /* If all query phrases seen by fts3BestSnippet() are present in at least
+    ** one of the nSnippet snippet fragments, break out of the loop.
+    */
+    assert( (mCovered&mSeen)==mCovered );
+    if( mSeen==mCovered || nSnippet==SizeofArray(aSnippet) ) break;
   }
 
-  if( rc==SQLITE_OK && nRem!=pCsr->nSegment ){
-    rc = fts3RepackSegdirLevel(p, iAbsLevel);
+  assert( nFToken>0 );
+
+  for(i=0; i<nSnippet && rc==SQLITE_OK; i++){
+    rc = fts3SnippetText(pCsr, &aSnippet[i], 
+        i, (i==nSnippet-1), nFToken, zStart, zEnd, zEllipsis, &res
+    );
   }
 
-  *pnRem = nRem;
-  return rc;
+ snippet_out:
+  sqlite3Fts3SegmentsClose(pTab);
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx, rc);
+    sqlite3_free(res.z);
+  }else{
+    sqlite3_result_text(pCtx, res.z, -1, sqlite3_free);
+  }
 }
 
-/*
-** Store an incr-merge hint in the database.
-*/
-static int fts3IncrmergeHintStore(Fts3Table *p, Blob *pHint){
-  sqlite3_stmt *pReplace = 0;
-  int rc;                         /* Return code */
 
-  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pReplace, 0);
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int(pReplace, 1, FTS_STAT_INCRMERGEHINT);
-    sqlite3_bind_blob(pReplace, 2, pHint->a, pHint->n, SQLITE_STATIC);
-    sqlite3_step(pReplace);
-    rc = sqlite3_reset(pReplace);
-  }
+typedef struct TermOffset TermOffset;
+typedef struct TermOffsetCtx TermOffsetCtx;
 
-  return rc;
-}
+struct TermOffset {
+  char *pList;                    /* Position-list */
+  int iPos;                       /* Position just read from pList */
+  int iOff;                       /* Offset of this term from read positions */
+};
+
+struct TermOffsetCtx {
+  Fts3Cursor *pCsr;
+  int iCol;                       /* Column of table to populate aTerm for */
+  int iTerm;
+  sqlite3_int64 iDocid;
+  TermOffset *aTerm;
+};
 
 /*
-** Load an incr-merge hint from the database. The incr-merge hint, if one 
-** exists, is stored in the rowid==1 row of the %_stat table.
-**
-** If successful, populate blob *pHint with the value read from the %_stat
-** table and return SQLITE_OK. Otherwise, if an error occurs, return an
-** SQLite error code.
+** This function is an fts3ExprIterate() callback used by sqlite3Fts3Offsets().
 */
-static int fts3IncrmergeHintLoad(Fts3Table *p, Blob *pHint){
-  sqlite3_stmt *pSelect = 0;
+static int fts3ExprTermOffsetInit(Fts3Expr *pExpr, int iPhrase, void *ctx){
+  TermOffsetCtx *p = (TermOffsetCtx *)ctx;
+  int nTerm;                      /* Number of tokens in phrase */
+  int iTerm;                      /* For looping through nTerm phrase terms */
+  char *pList;                    /* Pointer to position list for phrase */
+  int iPos = 0;                   /* First position in position-list */
   int rc;
 
-  pHint->n = 0;
-  rc = fts3SqlStmt(p, SQL_SELECT_STAT, &pSelect, 0);
-  if( rc==SQLITE_OK ){
-    int rc2;
-    sqlite3_bind_int(pSelect, 1, FTS_STAT_INCRMERGEHINT);
-    if( SQLITE_ROW==sqlite3_step(pSelect) ){
-      const char *aHint = sqlite3_column_blob(pSelect, 0);
-      int nHint = sqlite3_column_bytes(pSelect, 0);
-      if( aHint ){
-        blobGrowBuffer(pHint, nHint, &rc);
-        if( rc==SQLITE_OK ){
-          memcpy(pHint->a, aHint, nHint);
-          pHint->n = nHint;
-        }
-      }
-    }
-    rc2 = sqlite3_reset(pSelect);
-    if( rc==SQLITE_OK ) rc = rc2;
+  UNUSED_PARAMETER(iPhrase);
+  rc = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iCol, &pList);
+  nTerm = pExpr->pPhrase->nToken;
+  if( pList ){
+    fts3GetDeltaPosition(&pList, &iPos);
+    assert( iPos>=0 );
+  }
+
+  for(iTerm=0; iTerm<nTerm; iTerm++){
+    TermOffset *pT = &p->aTerm[p->iTerm++];
+    pT->iOff = nTerm-iTerm-1;
+    pT->pList = pList;
+    pT->iPos = iPos;
   }
 
   return rc;
 }
 
 /*
-** If *pRc is not SQLITE_OK when this function is called, it is a no-op.
-** Otherwise, append an entry to the hint stored in blob *pHint. Each entry
-** consists of two varints, the absolute level number of the input segments 
-** and the number of input segments.
-**
-** If successful, leave *pRc set to SQLITE_OK and return. If an error occurs,
-** set *pRc to an SQLite error code before returning.
+** Implementation of offsets() function.
 */
-static void fts3IncrmergeHintPush(
-  Blob *pHint,                    /* Hint blob to append to */
-  i64 iAbsLevel,                  /* First varint to store in hint */
-  int nInput,                     /* Second varint to store in hint */
-  int *pRc                        /* IN/OUT: Error code */
+SQLITE_PRIVATE void sqlite3Fts3Offsets(
+  sqlite3_context *pCtx,          /* SQLite function call context */
+  Fts3Cursor *pCsr                /* Cursor object */
 ){
-  blobGrowBuffer(pHint, pHint->n + 2*FTS3_VARINT_MAX, pRc);
-  if( *pRc==SQLITE_OK ){
-    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], iAbsLevel);
-    pHint->n += sqlite3Fts3PutVarint(&pHint->a[pHint->n], (i64)nInput);
-  }
-}
-
-/*
-** Read the last entry (most recently pushed) from the hint blob *pHint
-** and then remove the entry. Write the two values read to *piAbsLevel and 
-** *pnInput before returning.
-**
-** If no error occurs, return SQLITE_OK. If the hint blob in *pHint does
-** not contain at least two valid varints, return SQLITE_CORRUPT_VTAB.
-*/
-static int fts3IncrmergeHintPop(Blob *pHint, i64 *piAbsLevel, int *pnInput){
-  const int nHint = pHint->n;
-  int i;
-
-  i = pHint->n-2;
-  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
-  while( i>0 && (pHint->a[i-1] & 0x80) ) i--;
-
-  pHint->n = i;
-  i += sqlite3Fts3GetVarint(&pHint->a[i], piAbsLevel);
-  i += fts3GetVarint32(&pHint->a[i], pnInput);
-  if( i!=nHint ) return FTS_CORRUPT_VTAB;
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  sqlite3_tokenizer_module const *pMod = pTab->pTokenizer->pModule;
+  int rc;                         /* Return Code */
+  int nToken;                     /* Number of tokens in query */
+  int iCol;                       /* Column currently being processed */
+  StrBuffer res = {0, 0, 0};      /* Result string */
+  TermOffsetCtx sCtx;             /* Context for fts3ExprTermOffsetInit() */
 
-  return SQLITE_OK;
-}
+  if( !pCsr->pExpr ){
+    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
+    return;
+  }
 
+  memset(&sCtx, 0, sizeof(sCtx));
+  assert( pCsr->isRequireSeek==0 );
 
-/*
-** Attempt an incremental merge that writes nMerge leaf blocks.
-**
-** Incremental merges happen nMin segments at a time. The segments 
-** to be merged are the nMin oldest segments (the ones with the smallest 
-** values for the _segdir.idx field) in the highest level that contains 
-** at least nMin segments. Multiple merges might occur in an attempt to 
-** write the quota of nMerge leaf blocks.
-*/
-SQLITE_PRIVATE int sqlite3Fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
-  int rc;                         /* Return code */
-  int nRem = nMerge;              /* Number of leaf pages yet to  be written */
-  Fts3MultiSegReader *pCsr;       /* Cursor used to read input data */
-  Fts3SegFilter *pFilter;         /* Filter used with cursor pCsr */
-  IncrmergeWriter *pWriter;       /* Writer object */
-  int nSeg = 0;                   /* Number of input segments */
-  sqlite3_int64 iAbsLevel = 0;    /* Absolute level number to work on */
-  Blob hint = {0, 0, 0};          /* Hint read from %_stat table */
-  int bDirtyHint = 0;             /* True if blob 'hint' has been modified */
+  /* Count the number of terms in the query */
+  rc = fts3ExprLoadDoclists(pCsr, 0, &nToken);
+  if( rc!=SQLITE_OK ) goto offsets_out;
 
-  /* Allocate space for the cursor, filter and writer objects */
-  const int nAlloc = sizeof(*pCsr) + sizeof(*pFilter) + sizeof(*pWriter);
-  pWriter = (IncrmergeWriter *)sqlite3_malloc(nAlloc);
-  if( !pWriter ) return SQLITE_NOMEM;
-  pFilter = (Fts3SegFilter *)&pWriter[1];
-  pCsr = (Fts3MultiSegReader *)&pFilter[1];
+  /* Allocate the array of TermOffset iterators. */
+  sCtx.aTerm = (TermOffset *)sqlite3_malloc(sizeof(TermOffset)*nToken);
+  if( 0==sCtx.aTerm ){
+    rc = SQLITE_NOMEM;
+    goto offsets_out;
+  }
+  sCtx.iDocid = pCsr->iPrevId;
+  sCtx.pCsr = pCsr;
 
-  rc = fts3IncrmergeHintLoad(p, &hint);
-  while( rc==SQLITE_OK && nRem>0 ){
-    const i64 nMod = FTS3_SEGDIR_MAXLEVEL * p->nIndex;
-    sqlite3_stmt *pFindLevel = 0; /* SQL used to determine iAbsLevel */
-    int bUseHint = 0;             /* True if attempting to append */
-    int iIdx = 0;                 /* Largest idx in level (iAbsLevel+1) */
+  /* Loop through the table columns, appending offset information to 
+  ** string-buffer res for each column.
+  */
+  for(iCol=0; iCol<pTab->nColumn; iCol++){
+    sqlite3_tokenizer_cursor *pC; /* Tokenizer cursor */
+    const char *ZDUMMY;           /* Dummy argument used with xNext() */
+    int NDUMMY = 0;               /* Dummy argument used with xNext() */
+    int iStart = 0;
+    int iEnd = 0;
+    int iCurrent = 0;
+    const char *zDoc;
+    int nDoc;
 
-    /* Search the %_segdir table for the absolute level with the smallest
-    ** relative level number that contains at least nMin segments, if any.
-    ** If one is found, set iAbsLevel to the absolute level number and
-    ** nSeg to nMin. If no level with at least nMin segments can be found, 
-    ** set nSeg to -1.
+    /* Initialize the contents of sCtx.aTerm[] for column iCol. There is 
+    ** no way that this operation can fail, so the return code from
+    ** fts3ExprIterate() can be discarded.
     */
-    rc = fts3SqlStmt(p, SQL_FIND_MERGE_LEVEL, &pFindLevel, 0);
-    sqlite3_bind_int(pFindLevel, 1, nMin);
-    if( sqlite3_step(pFindLevel)==SQLITE_ROW ){
-      iAbsLevel = sqlite3_column_int64(pFindLevel, 0);
-      nSeg = nMin;
-    }else{
-      nSeg = -1;
-    }
-    rc = sqlite3_reset(pFindLevel);
+    sCtx.iCol = iCol;
+    sCtx.iTerm = 0;
+    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprTermOffsetInit, (void*)&sCtx);
 
-    /* If the hint read from the %_stat table is not empty, check if the
-    ** last entry in it specifies a relative level smaller than or equal
-    ** to the level identified by the block above (if any). If so, this 
-    ** iteration of the loop will work on merging at the hinted level.
+    /* Retreive the text stored in column iCol. If an SQL NULL is stored 
+    ** in column iCol, jump immediately to the next iteration of the loop.
+    ** If an OOM occurs while retrieving the data (this can happen if SQLite
+    ** needs to transform the data from utf-16 to utf-8), return SQLITE_NOMEM 
+    ** to the caller. 
     */
-    if( rc==SQLITE_OK && hint.n ){
-      int nHint = hint.n;
-      sqlite3_int64 iHintAbsLevel = 0;      /* Hint level */
-      int nHintSeg = 0;                     /* Hint number of segments */
-
-      rc = fts3IncrmergeHintPop(&hint, &iHintAbsLevel, &nHintSeg);
-      if( nSeg<0 || (iAbsLevel % nMod) >= (iHintAbsLevel % nMod) ){
-        iAbsLevel = iHintAbsLevel;
-        nSeg = nHintSeg;
-        bUseHint = 1;
-        bDirtyHint = 1;
-      }else{
-        /* This undoes the effect of the HintPop() above - so that no entry
-        ** is removed from the hint blob.  */
-        hint.n = nHint;
-      }
-    }
-
-    /* If nSeg is less that zero, then there is no level with at least
-    ** nMin segments and no hint in the %_stat table. No work to do.
-    ** Exit early in this case.  */
-    if( nSeg<0 ) break;
-
-    /* Open a cursor to iterate through the contents of the oldest nSeg 
-    ** indexes of absolute level iAbsLevel. If this cursor is opened using 
-    ** the 'hint' parameters, it is possible that there are less than nSeg
-    ** segments available in level iAbsLevel. In this case, no work is
-    ** done on iAbsLevel - fall through to the next iteration of the loop 
-    ** to start work on some other level.  */
-    memset(pWriter, 0, nAlloc);
-    pFilter->flags = FTS3_SEGMENT_REQUIRE_POS;
-
-    if( rc==SQLITE_OK ){
-      rc = fts3IncrmergeOutputIdx(p, iAbsLevel, &iIdx);
-      assert( bUseHint==1 || bUseHint==0 );
-      if( iIdx==0 || (bUseHint && iIdx==1) ){
-        int bIgnore = 0;
-        rc = fts3SegmentIsMaxLevel(p, iAbsLevel+1, &bIgnore);
-        if( bIgnore ){
-          pFilter->flags |= FTS3_SEGMENT_IGNORE_EMPTY;
-        }
+    zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
+    nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
+    if( zDoc==0 ){
+      if( sqlite3_column_type(pCsr->pStmt, iCol+1)==SQLITE_NULL ){
+        continue;
       }
+      rc = SQLITE_NOMEM;
+      goto offsets_out;
     }
 
-    if( rc==SQLITE_OK ){
-      rc = fts3IncrmergeCsr(p, iAbsLevel, nSeg, pCsr);
-    }
-    if( SQLITE_OK==rc && pCsr->nSegment==nSeg
-     && SQLITE_OK==(rc = sqlite3Fts3SegReaderStart(p, pCsr, pFilter))
-     && SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, pCsr))
-    ){
-      if( bUseHint && iIdx>0 ){
-        const char *zKey = pCsr->zTerm;
-        int nKey = pCsr->nTerm;
-        rc = fts3IncrmergeLoad(p, iAbsLevel, iIdx-1, zKey, nKey, pWriter);
-      }else{
-        rc = fts3IncrmergeWriter(p, iAbsLevel, iIdx, pCsr, pWriter);
-      }
+    /* Initialize a tokenizer iterator to iterate through column iCol. */
+    rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, pCsr->iLangid,
+        zDoc, nDoc, &pC
+    );
+    if( rc!=SQLITE_OK ) goto offsets_out;
 
-      if( rc==SQLITE_OK && pWriter->nLeafEst ){
-        fts3LogMerge(nSeg, iAbsLevel);
-        do {
-          rc = fts3IncrmergeAppend(p, pWriter, pCsr);
-          if( rc==SQLITE_OK ) rc = sqlite3Fts3SegReaderStep(p, pCsr);
-          if( pWriter->nWork>=nRem && rc==SQLITE_ROW ) rc = SQLITE_OK;
-        }while( rc==SQLITE_ROW );
+    rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+    while( rc==SQLITE_OK ){
+      int i;                      /* Used to loop through terms */
+      int iMinPos = 0x7FFFFFFF;   /* Position of next token */
+      TermOffset *pTerm = 0;      /* TermOffset associated with next token */
 
-        /* Update or delete the input segments */
-        if( rc==SQLITE_OK ){
-          nRem -= (1 + pWriter->nWork);
-          rc = fts3IncrmergeChomp(p, iAbsLevel, pCsr, &nSeg);
-          if( nSeg!=0 ){
-            bDirtyHint = 1;
-            fts3IncrmergeHintPush(&hint, iAbsLevel, nSeg, &rc);
-          }
+      for(i=0; i<nToken; i++){
+        TermOffset *pT = &sCtx.aTerm[i];
+        if( pT->pList && (pT->iPos-pT->iOff)<iMinPos ){
+          iMinPos = pT->iPos-pT->iOff;
+          pTerm = pT;
         }
       }
 
-      if( nSeg!=0 ){
-        pWriter->nLeafData = pWriter->nLeafData * -1;
-      }
-      fts3IncrmergeRelease(p, pWriter, &rc);
-      if( nSeg==0 && pWriter->bNoLeafData==0 ){
-        fts3PromoteSegments(p, iAbsLevel+1, pWriter->nLeafData);
+      if( !pTerm ){
+        /* All offsets for this column have been gathered. */
+        rc = SQLITE_DONE;
+      }else{
+        assert( iCurrent<=iMinPos );
+        if( 0==(0xFE&*pTerm->pList) ){
+          pTerm->pList = 0;
+        }else{
+          fts3GetDeltaPosition(&pTerm->pList, &pTerm->iPos);
+        }
+        while( rc==SQLITE_OK && iCurrent<iMinPos ){
+          rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
+        }
+        if( rc==SQLITE_OK ){
+          char aBuffer[64];
+          sqlite3_snprintf(sizeof(aBuffer), aBuffer, 
+              "%d %d %d %d ", iCol, pTerm-sCtx.aTerm, iStart, iEnd-iStart
+          );
+          rc = fts3StringAppend(&res, aBuffer, -1);
+        }else if( rc==SQLITE_DONE && pTab->zContentTbl==0 ){
+          rc = FTS_CORRUPT_VTAB;
+        }
       }
     }
+    if( rc==SQLITE_DONE ){
+      rc = SQLITE_OK;
+    }
 
-    sqlite3Fts3SegReaderFinish(pCsr);
+    pMod->xClose(pC);
+    if( rc!=SQLITE_OK ) goto offsets_out;
   }
 
-  /* Write the hint values into the %_stat table for the next incr-merger */
-  if( bDirtyHint && rc==SQLITE_OK ){
-    rc = fts3IncrmergeHintStore(p, &hint);
+ offsets_out:
+  sqlite3_free(sCtx.aTerm);
+  assert( rc!=SQLITE_DONE );
+  sqlite3Fts3SegmentsClose(pTab);
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx,  rc);
+    sqlite3_free(res.z);
+  }else{
+    sqlite3_result_text(pCtx, res.z, res.n-1, sqlite3_free);
   }
-
-  sqlite3_free(pWriter);
-  sqlite3_free(hint.a);
-  return rc;
-}
-
-/*
-** Convert the text beginning at *pz into an integer and return
-** its value.  Advance *pz to point to the first character past
-** the integer.
-*/
-static int fts3Getint(const char **pz){
-  const char *z = *pz;
-  int i = 0;
-  while( (*z)>='0' && (*z)<='9' ) i = 10*i + *(z++) - '0';
-  *pz = z;
-  return i;
+  return;
 }
 
 /*
-** Process statements of the form:
-**
-**    INSERT INTO table(table) VALUES('merge=A,B');
-**
-** A and B are integers that decode to be the number of leaf pages
-** written for the merge, and the minimum number of segments on a level
-** before it will be selected for a merge, respectively.
+** Implementation of matchinfo() function.
 */
-static int fts3DoIncrmerge(
-  Fts3Table *p,                   /* FTS3 table handle */
-  const char *zParam              /* Nul-terminated string containing "A,B" */
+SQLITE_PRIVATE void sqlite3Fts3Matchinfo(
+  sqlite3_context *pContext,      /* Function call context */
+  Fts3Cursor *pCsr,               /* FTS3 table cursor */
+  const char *zArg                /* Second arg to matchinfo() function */
 ){
-  int rc;
-  int nMin = (FTS3_MERGE_COUNT / 2);
-  int nMerge = 0;
-  const char *z = zParam;
-
-  /* Read the first integer value */
-  nMerge = fts3Getint(&z);
+  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
+  const char *zFormat;
 
-  /* If the first integer value is followed by a ',',  read the second
-  ** integer value. */
-  if( z[0]==',' && z[1]!='\0' ){
-    z++;
-    nMin = fts3Getint(&z);
+  if( zArg ){
+    zFormat = zArg;
+  }else{
+    zFormat = FTS3_MATCHINFO_DEFAULT;
   }
 
-  if( z[0]!='\0' || nMin<2 ){
-    rc = SQLITE_ERROR;
+  if( !pCsr->pExpr ){
+    sqlite3_result_blob(pContext, "", 0, SQLITE_STATIC);
+    return;
   }else{
-    rc = SQLITE_OK;
-    if( !p->bHasStat ){
-      assert( p->bFts4==0 );
-      sqlite3Fts3CreateStatTable(&rc, p);
-    }
-    if( rc==SQLITE_OK ){
-      rc = sqlite3Fts3Incrmerge(p, nMerge, nMin);
-    }
-    sqlite3Fts3SegmentsClose(p);
+    /* Retrieve matchinfo() data. */
+    fts3GetMatchinfo(pContext, pCsr, zFormat);
+    sqlite3Fts3SegmentsClose(pTab);
   }
-  return rc;
 }
 
+#endif
+
+/************** End of fts3_snippet.c ****************************************/
+/************** Begin file fts3_unicode.c ************************************/
 /*
-** Process statements of the form:
+** 2012 May 24
 **
-**    INSERT INTO table(table) VALUES('automerge=X');
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
 **
-** where X is an integer.  X==0 means to turn automerge off.  X!=0 means
-** turn it on.  The setting is persistent.
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** Implementation of the "unicode" full-text-search tokenizer.
 */
-static int fts3DoAutoincrmerge(
-  Fts3Table *p,                   /* FTS3 table handle */
-  const char *zParam              /* Nul-terminated string containing boolean */
-){
-  int rc = SQLITE_OK;
-  sqlite3_stmt *pStmt = 0;
-  p->nAutoincrmerge = fts3Getint(&zParam);
-  if( p->nAutoincrmerge==1 || p->nAutoincrmerge>FTS3_MERGE_COUNT ){
-    p->nAutoincrmerge = 8;
-  }
-  if( !p->bHasStat ){
-    assert( p->bFts4==0 );
-    sqlite3Fts3CreateStatTable(&rc, p);
-    if( rc ) return rc;
-  }
-  rc = fts3SqlStmt(p, SQL_REPLACE_STAT, &pStmt, 0);
-  if( rc ) return rc;
-  sqlite3_bind_int(pStmt, 1, FTS_STAT_AUTOINCRMERGE);
-  sqlite3_bind_int(pStmt, 2, p->nAutoincrmerge);
-  sqlite3_step(pStmt);
-  rc = sqlite3_reset(pStmt);
-  return rc;
-}
+
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+
+/* #include <assert.h> */
+/* #include <stdlib.h> */
+/* #include <stdio.h> */
+/* #include <string.h> */
+
+/* #include "fts3_tokenizer.h" */
 
 /*
-** Return a 64-bit checksum for the FTS index entry specified by the
-** arguments to this function.
+** The following two macros - READ_UTF8 and WRITE_UTF8 - have been copied
+** from the sqlite3 source file utf.c. If this file is compiled as part
+** of the amalgamation, they are not required.
 */
-static u64 fts3ChecksumEntry(
-  const char *zTerm,              /* Pointer to buffer containing term */
-  int nTerm,                      /* Size of zTerm in bytes */
-  int iLangid,                    /* Language id for current row */
-  int iIndex,                     /* Index (0..Fts3Table.nIndex-1) */
-  i64 iDocid,                     /* Docid for current row. */
-  int iCol,                       /* Column number */
-  int iPos                        /* Position */
-){
-  int i;
-  u64 ret = (u64)iDocid;
+#ifndef SQLITE_AMALGAMATION
 
-  ret += (ret<<3) + iLangid;
-  ret += (ret<<3) + iIndex;
-  ret += (ret<<3) + iCol;
-  ret += (ret<<3) + iPos;
-  for(i=0; i<nTerm; i++) ret += (ret<<3) + zTerm[i];
+static const unsigned char sqlite3Utf8Trans1[] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
+};
 
-  return ret;
+#define READ_UTF8(zIn, zTerm, c)                           \
+  c = *(zIn++);                                            \
+  if( c>=0xc0 ){                                           \
+    c = sqlite3Utf8Trans1[c-0xc0];                         \
+    while( zIn!=zTerm && (*zIn & 0xc0)==0x80 ){            \
+      c = (c<<6) + (0x3f & *(zIn++));                      \
+    }                                                      \
+    if( c<0x80                                             \
+        || (c&0xFFFFF800)==0xD800                          \
+        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }        \
+  }
+
+#define WRITE_UTF8(zOut, c) {                          \
+  if( c<0x00080 ){                                     \
+    *zOut++ = (u8)(c&0xFF);                            \
+  }                                                    \
+  else if( c<0x00800 ){                                \
+    *zOut++ = 0xC0 + (u8)((c>>6)&0x1F);                \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+  else if( c<0x10000 ){                                \
+    *zOut++ = 0xE0 + (u8)((c>>12)&0x0F);               \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }else{                                               \
+    *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);             \
+    *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);             \
+    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
+    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
+  }                                                    \
+}
+
+#endif /* ifndef SQLITE_AMALGAMATION */
+
+typedef struct unicode_tokenizer unicode_tokenizer;
+typedef struct unicode_cursor unicode_cursor;
+
+struct unicode_tokenizer {
+  sqlite3_tokenizer base;
+  int bRemoveDiacritic;
+  int nException;
+  int *aiException;
+};
+
+struct unicode_cursor {
+  sqlite3_tokenizer_cursor base;
+  const unsigned char *aInput;    /* Input text being tokenized */
+  int nInput;                     /* Size of aInput[] in bytes */
+  int iOff;                       /* Current offset within aInput[] */
+  int iToken;                     /* Index of next token to be returned */
+  char *zToken;                   /* storage for current token */
+  int nAlloc;                     /* space allocated at zToken */
+};
+
+
+/*
+** Destroy a tokenizer allocated by unicodeCreate().
+*/
+static int unicodeDestroy(sqlite3_tokenizer *pTokenizer){
+  if( pTokenizer ){
+    unicode_tokenizer *p = (unicode_tokenizer *)pTokenizer;
+    sqlite3_free(p->aiException);
+    sqlite3_free(p);
+  }
+  return SQLITE_OK;
 }
 
 /*
-** Return a checksum of all entries in the FTS index that correspond to
-** language id iLangid. The checksum is calculated by XORing the checksums
-** of each individual entry (see fts3ChecksumEntry()) together.
+** As part of a tokenchars= or separators= option, the CREATE VIRTUAL TABLE
+** statement has specified that the tokenizer for this table shall consider
+** all characters in string zIn/nIn to be separators (if bAlnum==0) or
+** token characters (if bAlnum==1).
 **
-** If successful, the checksum value is returned and *pRc set to SQLITE_OK.
-** Otherwise, if an error occurs, *pRc is set to an SQLite error code. The
-** return value is undefined in this case.
+** For each codepoint in the zIn/nIn string, this function checks if the
+** sqlite3FtsUnicodeIsalnum() function already returns the desired result.
+** If so, no action is taken. Otherwise, the codepoint is added to the 
+** unicode_tokenizer.aiException[] array. For the purposes of tokenization,
+** the return value of sqlite3FtsUnicodeIsalnum() is inverted for all
+** codepoints in the aiException[] array.
+**
+** If a standalone diacritic mark (one that sqlite3FtsUnicodeIsdiacritic()
+** identifies as a diacritic) occurs in the zIn/nIn string it is ignored.
+** It is not possible to change the behavior of the tokenizer with respect
+** to these codepoints.
 */
-static u64 fts3ChecksumIndex(
-  Fts3Table *p,                   /* FTS3 table handle */
-  int iLangid,                    /* Language id to return cksum for */
-  int iIndex,                     /* Index to cksum (0..p->nIndex-1) */
-  int *pRc                        /* OUT: Return code */
+static int unicodeAddExceptions(
+  unicode_tokenizer *p,           /* Tokenizer to add exceptions to */
+  int bAlnum,                     /* Replace Isalnum() return value with this */
+  const char *zIn,                /* Array of characters to make exceptions */
+  int nIn                         /* Length of z in bytes */
 ){
-  Fts3SegFilter filter;
-  Fts3MultiSegReader csr;
-  int rc;
-  u64 cksum = 0;
-
-  assert( *pRc==SQLITE_OK );
+  const unsigned char *z = (const unsigned char *)zIn;
+  const unsigned char *zTerm = &z[nIn];
+  int iCode;
+  int nEntry = 0;
 
-  memset(&filter, 0, sizeof(filter));
-  memset(&csr, 0, sizeof(csr));
-  filter.flags =  FTS3_SEGMENT_REQUIRE_POS|FTS3_SEGMENT_IGNORE_EMPTY;
-  filter.flags |= FTS3_SEGMENT_SCAN;
+  assert( bAlnum==0 || bAlnum==1 );
 
-  rc = sqlite3Fts3SegReaderCursor(
-      p, iLangid, iIndex, FTS3_SEGCURSOR_ALL, 0, 0, 0, 1,&csr
-  );
-  if( rc==SQLITE_OK ){
-    rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
+  while( z<zTerm ){
+    READ_UTF8(z, zTerm, iCode);
+    assert( (sqlite3FtsUnicodeIsalnum(iCode) & 0xFFFFFFFE)==0 );
+    if( sqlite3FtsUnicodeIsalnum(iCode)!=bAlnum 
+     && sqlite3FtsUnicodeIsdiacritic(iCode)==0 
+    ){
+      nEntry++;
+    }
   }
 
-  if( rc==SQLITE_OK ){
-    while( SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, &csr)) ){
-      char *pCsr = csr.aDoclist;
-      char *pEnd = &pCsr[csr.nDoclist];
+  if( nEntry ){
+    int *aNew;                    /* New aiException[] array */
+    int nNew;                     /* Number of valid entries in array aNew[] */
 
-      i64 iDocid = 0;
-      i64 iCol = 0;
-      i64 iPos = 0;
+    aNew = sqlite3_realloc(p->aiException, (p->nException+nEntry)*sizeof(int));
+    if( aNew==0 ) return SQLITE_NOMEM;
+    nNew = p->nException;
 
-      pCsr += sqlite3Fts3GetVarint(pCsr, &iDocid);
-      while( pCsr<pEnd ){
-        i64 iVal = 0;
-        pCsr += sqlite3Fts3GetVarint(pCsr, &iVal);
-        if( pCsr<pEnd ){
-          if( iVal==0 || iVal==1 ){
-            iCol = 0;
-            iPos = 0;
-            if( iVal ){
-              pCsr += sqlite3Fts3GetVarint(pCsr, &iCol);
-            }else{
-              pCsr += sqlite3Fts3GetVarint(pCsr, &iVal);
-              iDocid += iVal;
-            }
-          }else{
-            iPos += (iVal - 2);
-            cksum = cksum ^ fts3ChecksumEntry(
-                csr.zTerm, csr.nTerm, iLangid, iIndex, iDocid,
-                (int)iCol, (int)iPos
-            );
-          }
-        }
+    z = (const unsigned char *)zIn;
+    while( z<zTerm ){
+      READ_UTF8(z, zTerm, iCode);
+      if( sqlite3FtsUnicodeIsalnum(iCode)!=bAlnum 
+       && sqlite3FtsUnicodeIsdiacritic(iCode)==0
+      ){
+        int i, j;
+        for(i=0; i<nNew && aNew[i]<iCode; i++);
+        for(j=nNew; j>i; j--) aNew[j] = aNew[j-1];
+        aNew[i] = iCode;
+        nNew++;
       }
     }
+    p->aiException = aNew;
+    p->nException = nNew;
   }
-  sqlite3Fts3SegReaderFinish(&csr);
 
-  *pRc = rc;
-  return cksum;
+  return SQLITE_OK;
 }
 
 /*
-** Check if the contents of the FTS index match the current contents of the
-** content table. If no error occurs and the contents do match, set *pbOk
-** to true and return SQLITE_OK. Or if the contents do not match, set *pbOk
-** to false before returning.
-**
-** If an error occurs (e.g. an OOM or IO error), return an SQLite error 
-** code. The final value of *pbOk is undefined in this case.
+** Return true if the p->aiException[] array contains the value iCode.
 */
-static int fts3IntegrityCheck(Fts3Table *p, int *pbOk){
-  int rc = SQLITE_OK;             /* Return code */
-  u64 cksum1 = 0;                 /* Checksum based on FTS index contents */
-  u64 cksum2 = 0;                 /* Checksum based on %_content contents */
-  sqlite3_stmt *pAllLangid = 0;   /* Statement to return all language-ids */
+static int unicodeIsException(unicode_tokenizer *p, int iCode){
+  if( p->nException>0 ){
+    int *a = p->aiException;
+    int iLo = 0;
+    int iHi = p->nException-1;
 
-  /* This block calculates the checksum according to the FTS index. */
-  rc = fts3SqlStmt(p, SQL_SELECT_ALL_LANGID, &pAllLangid, 0);
-  if( rc==SQLITE_OK ){
-    int rc2;
-    sqlite3_bind_int(pAllLangid, 1, p->iPrevLangid);
-    sqlite3_bind_int(pAllLangid, 2, p->nIndex);
-    while( rc==SQLITE_OK && sqlite3_step(pAllLangid)==SQLITE_ROW ){
-      int iLangid = sqlite3_column_int(pAllLangid, 0);
-      int i;
-      for(i=0; i<p->nIndex; i++){
-        cksum1 = cksum1 ^ fts3ChecksumIndex(p, iLangid, i, &rc);
+    while( iHi>=iLo ){
+      int iTest = (iHi + iLo) / 2;
+      if( iCode==a[iTest] ){
+        return 1;
+      }else if( iCode>a[iTest] ){
+        iLo = iTest+1;
+      }else{
+        iHi = iTest-1;
       }
     }
-    rc2 = sqlite3_reset(pAllLangid);
-    if( rc==SQLITE_OK ) rc = rc2;
   }
 
-  /* This block calculates the checksum according to the %_content table */
-  if( rc==SQLITE_OK ){
-    sqlite3_tokenizer_module const *pModule = p->pTokenizer->pModule;
-    sqlite3_stmt *pStmt = 0;
-    char *zSql;
-   
-    zSql = sqlite3_mprintf("SELECT %s" , p->zReadExprlist);
-    if( !zSql ){
-      rc = SQLITE_NOMEM;
-    }else{
-      rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
-      sqlite3_free(zSql);
-    }
+  return 0;
+}
 
-    while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
-      i64 iDocid = sqlite3_column_int64(pStmt, 0);
-      int iLang = langidFromSelect(p, pStmt);
-      int iCol;
+/*
+** Return true if, for the purposes of tokenization, codepoint iCode is
+** considered a token character (not a separator).
+*/
+static int unicodeIsAlnum(unicode_tokenizer *p, int iCode){
+  assert( (sqlite3FtsUnicodeIsalnum(iCode) & 0xFFFFFFFE)==0 );
+  return sqlite3FtsUnicodeIsalnum(iCode) ^ unicodeIsException(p, iCode);
+}
 
-      for(iCol=0; rc==SQLITE_OK && iCol<p->nColumn; iCol++){
-        if( p->abNotindexed[iCol]==0 ){
-          const char *zText = (const char *)sqlite3_column_text(pStmt, iCol+1);
-          int nText = sqlite3_column_bytes(pStmt, iCol+1);
-          sqlite3_tokenizer_cursor *pT = 0;
+/*
+** Create a new tokenizer instance.
+*/
+static int unicodeCreate(
+  int nArg,                       /* Size of array argv[] */
+  const char * const *azArg,      /* Tokenizer creation arguments */
+  sqlite3_tokenizer **pp          /* OUT: New tokenizer handle */
+){
+  unicode_tokenizer *pNew;        /* New tokenizer object */
+  int i;
+  int rc = SQLITE_OK;
 
-          rc = sqlite3Fts3OpenTokenizer(p->pTokenizer, iLang, zText, nText,&pT);
-          while( rc==SQLITE_OK ){
-            char const *zToken;       /* Buffer containing token */
-            int nToken = 0;           /* Number of bytes in token */
-            int iDum1 = 0, iDum2 = 0; /* Dummy variables */
-            int iPos = 0;             /* Position of token in zText */
+  pNew = (unicode_tokenizer *) sqlite3_malloc(sizeof(unicode_tokenizer));
+  if( pNew==NULL ) return SQLITE_NOMEM;
+  memset(pNew, 0, sizeof(unicode_tokenizer));
+  pNew->bRemoveDiacritic = 1;
 
-            rc = pModule->xNext(pT, &zToken, &nToken, &iDum1, &iDum2, &iPos);
-            if( rc==SQLITE_OK ){
-              int i;
-              cksum2 = cksum2 ^ fts3ChecksumEntry(
-                  zToken, nToken, iLang, 0, iDocid, iCol, iPos
-              );
-              for(i=1; i<p->nIndex; i++){
-                if( p->aIndex[i].nPrefix<=nToken ){
-                  cksum2 = cksum2 ^ fts3ChecksumEntry(
-                      zToken, p->aIndex[i].nPrefix, iLang, i, iDocid, iCol, iPos
-                  );
-                }
-              }
-            }
-          }
-          if( pT ) pModule->xClose(pT);
-          if( rc==SQLITE_DONE ) rc = SQLITE_OK;
-        }
-      }
-    }
+  for(i=0; rc==SQLITE_OK && i<nArg; i++){
+    const char *z = azArg[i];
+    int n = (int)strlen(z);
 
-    sqlite3_finalize(pStmt);
+    if( n==19 && memcmp("remove_diacritics=1", z, 19)==0 ){
+      pNew->bRemoveDiacritic = 1;
+    }
+    else if( n==19 && memcmp("remove_diacritics=0", z, 19)==0 ){
+      pNew->bRemoveDiacritic = 0;
+    }
+    else if( n>=11 && memcmp("tokenchars=", z, 11)==0 ){
+      rc = unicodeAddExceptions(pNew, 1, &z[11], n-11);
+    }
+    else if( n>=11 && memcmp("separators=", z, 11)==0 ){
+      rc = unicodeAddExceptions(pNew, 0, &z[11], n-11);
+    }
+    else{
+      /* Unrecognized argument */
+      rc  = SQLITE_ERROR;
+    }
   }
 
-  *pbOk = (cksum1==cksum2);
+  if( rc!=SQLITE_OK ){
+    unicodeDestroy((sqlite3_tokenizer *)pNew);
+    pNew = 0;
+  }
+  *pp = (sqlite3_tokenizer *)pNew;
   return rc;
 }
 
 /*
-** Run the integrity-check. If no error occurs and the current contents of
-** the FTS index are correct, return SQLITE_OK. Or, if the contents of the
-** FTS index are incorrect, return SQLITE_CORRUPT_VTAB.
-**
-** Or, if an error (e.g. an OOM or IO error) occurs, return an SQLite 
-** error code.
-**
-** The integrity-check works as follows. For each token and indexed token
-** prefix in the document set, a 64-bit checksum is calculated (by code
-** in fts3ChecksumEntry()) based on the following:
-**
-**     + The index number (0 for the main index, 1 for the first prefix
-**       index etc.),
-**     + The token (or token prefix) text itself, 
-**     + The language-id of the row it appears in,
-**     + The docid of the row it appears in,
-**     + The column it appears in, and
-**     + The tokens position within that column.
-**
-** The checksums for all entries in the index are XORed together to create
-** a single checksum for the entire index.
-**
-** The integrity-check code calculates the same checksum in two ways:
-**
-**     1. By scanning the contents of the FTS index, and 
-**     2. By scanning and tokenizing the content table.
-**
-** If the two checksums are identical, the integrity-check is deemed to have
-** passed.
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is pInput[0..nBytes-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
 */
-static int fts3DoIntegrityCheck(
-  Fts3Table *p                    /* FTS3 table handle */
+static int unicodeOpen(
+  sqlite3_tokenizer *p,           /* The tokenizer */
+  const char *aInput,             /* Input string */
+  int nInput,                     /* Size of string aInput in bytes */
+  sqlite3_tokenizer_cursor **pp   /* OUT: New cursor object */
 ){
-  int rc;
-  int bOk = 0;
-  rc = fts3IntegrityCheck(p, &bOk);
-  if( rc==SQLITE_OK && bOk==0 ) rc = FTS_CORRUPT_VTAB;
-  return rc;
-}
-
-/*
-** Handle a 'special' INSERT of the form:
-**
-**   "INSERT INTO tbl(tbl) VALUES(<expr>)"
-**
-** Argument pVal contains the result of <expr>. Currently the only 
-** meaningful value to insert is the text 'optimize'.
-*/
-static int fts3SpecialInsert(Fts3Table *p, sqlite3_value *pVal){
-  int rc;                         /* Return Code */
-  const char *zVal = (const char *)sqlite3_value_text(pVal);
-  int nVal = sqlite3_value_bytes(pVal);
+  unicode_cursor *pCsr;
 
-  if( !zVal ){
+  pCsr = (unicode_cursor *)sqlite3_malloc(sizeof(unicode_cursor));
+  if( pCsr==0 ){
     return SQLITE_NOMEM;
-  }else if( nVal==8 && 0==sqlite3_strnicmp(zVal, "optimize", 8) ){
-    rc = fts3DoOptimize(p, 0);
-  }else if( nVal==7 && 0==sqlite3_strnicmp(zVal, "rebuild", 7) ){
-    rc = fts3DoRebuild(p);
-  }else if( nVal==15 && 0==sqlite3_strnicmp(zVal, "integrity-check", 15) ){
-    rc = fts3DoIntegrityCheck(p);
-  }else if( nVal>6 && 0==sqlite3_strnicmp(zVal, "merge=", 6) ){
-    rc = fts3DoIncrmerge(p, &zVal[6]);
-  }else if( nVal>10 && 0==sqlite3_strnicmp(zVal, "automerge=", 10) ){
-    rc = fts3DoAutoincrmerge(p, &zVal[10]);
-#ifdef SQLITE_TEST
-  }else if( nVal>9 && 0==sqlite3_strnicmp(zVal, "nodesize=", 9) ){
-    p->nNodeSize = atoi(&zVal[9]);
-    rc = SQLITE_OK;
-  }else if( nVal>11 && 0==sqlite3_strnicmp(zVal, "maxpending=", 9) ){
-    p->nMaxPendingData = atoi(&zVal[11]);
-    rc = SQLITE_OK;
-  }else if( nVal>21 && 0==sqlite3_strnicmp(zVal, "test-no-incr-doclist=", 21) ){
-    p->bNoIncrDoclist = atoi(&zVal[21]);
-    rc = SQLITE_OK;
-#endif
+  }
+  memset(pCsr, 0, sizeof(unicode_cursor));
+
+  pCsr->aInput = (const unsigned char *)aInput;
+  if( aInput==0 ){
+    pCsr->nInput = 0;
+  }else if( nInput<0 ){
+    pCsr->nInput = (int)strlen(aInput);
   }else{
-    rc = SQLITE_ERROR;
+    pCsr->nInput = nInput;
   }
 
-  return rc;
+  *pp = &pCsr->base;
+  UNUSED_PARAMETER(p);
+  return SQLITE_OK;
 }
 
-#ifndef SQLITE_DISABLE_FTS4_DEFERRED
 /*
-** Delete all cached deferred doclists. Deferred doclists are cached
-** (allocated) by the sqlite3Fts3CacheDeferredDoclists() function.
+** Close a tokenization cursor previously opened by a call to
+** simpleOpen() above.
 */
-SQLITE_PRIVATE void sqlite3Fts3FreeDeferredDoclists(Fts3Cursor *pCsr){
-  Fts3DeferredToken *pDef;
-  for(pDef=pCsr->pDeferred; pDef; pDef=pDef->pNext){
-    fts3PendingListDelete(pDef->pList);
-    pDef->pList = 0;
-  }
+static int unicodeClose(sqlite3_tokenizer_cursor *pCursor){
+  unicode_cursor *pCsr = (unicode_cursor *) pCursor;
+  sqlite3_free(pCsr->zToken);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
 }
 
 /*
-** Free all entries in the pCsr->pDeffered list. Entries are added to 
-** this list using sqlite3Fts3DeferToken().
+** Extract the next token from a tokenization cursor.  The cursor must
+** have been opened by a prior call to simpleOpen().
 */
-SQLITE_PRIVATE void sqlite3Fts3FreeDeferredTokens(Fts3Cursor *pCsr){
-  Fts3DeferredToken *pDef;
-  Fts3DeferredToken *pNext;
-  for(pDef=pCsr->pDeferred; pDef; pDef=pNext){
-    pNext = pDef->pNext;
-    fts3PendingListDelete(pDef->pList);
-    sqlite3_free(pDef);
-  }
-  pCsr->pDeferred = 0;
-}
+static int unicodeNext(
+  sqlite3_tokenizer_cursor *pC,   /* Cursor returned by simpleOpen */
+  const char **paToken,           /* OUT: Token text */
+  int *pnToken,                   /* OUT: Number of bytes at *paToken */
+  int *piStart,                   /* OUT: Starting offset of token */
+  int *piEnd,                     /* OUT: Ending offset of token */
+  int *piPos                      /* OUT: Position integer of token */
+){
+  unicode_cursor *pCsr = (unicode_cursor *)pC;
+  unicode_tokenizer *p = ((unicode_tokenizer *)pCsr->base.pTokenizer);
+  int iCode = 0;
+  char *zOut;
+  const unsigned char *z = &pCsr->aInput[pCsr->iOff];
+  const unsigned char *zStart = z;
+  const unsigned char *zEnd;
+  const unsigned char *zTerm = &pCsr->aInput[pCsr->nInput];
 
-/*
-** Generate deferred-doclists for all tokens in the pCsr->pDeferred list
-** based on the row that pCsr currently points to.
-**
-** A deferred-doclist is like any other doclist with position information
-** included, except that it only contains entries for a single row of the
-** table, not for all rows.
-*/
-SQLITE_PRIVATE int sqlite3Fts3CacheDeferredDoclists(Fts3Cursor *pCsr){
-  int rc = SQLITE_OK;             /* Return code */
-  if( pCsr->pDeferred ){
-    int i;                        /* Used to iterate through table columns */
-    sqlite3_int64 iDocid;         /* Docid of the row pCsr points to */
-    Fts3DeferredToken *pDef;      /* Used to iterate through deferred tokens */
-  
-    Fts3Table *p = (Fts3Table *)pCsr->base.pVtab;
-    sqlite3_tokenizer *pT = p->pTokenizer;
-    sqlite3_tokenizer_module const *pModule = pT->pModule;
-   
-    assert( pCsr->isRequireSeek==0 );
-    iDocid = sqlite3_column_int64(pCsr->pStmt, 0);
-  
-    for(i=0; i<p->nColumn && rc==SQLITE_OK; i++){
-      if( p->abNotindexed[i]==0 ){
-        const char *zText = (const char *)sqlite3_column_text(pCsr->pStmt, i+1);
-        sqlite3_tokenizer_cursor *pTC = 0;
+  /* Scan past any delimiter characters before the start of the next token.
+  ** Return SQLITE_DONE early if this takes us all the way to the end of 
+  ** the input.  */
+  while( z<zTerm ){
+    READ_UTF8(z, zTerm, iCode);
+    if( unicodeIsAlnum(p, iCode) ) break;
+    zStart = z;
+  }
+  if( zStart>=zTerm ) return SQLITE_DONE;
 
-        rc = sqlite3Fts3OpenTokenizer(pT, pCsr->iLangid, zText, -1, &pTC);
-        while( rc==SQLITE_OK ){
-          char const *zToken;       /* Buffer containing token */
-          int nToken = 0;           /* Number of bytes in token */
-          int iDum1 = 0, iDum2 = 0; /* Dummy variables */
-          int iPos = 0;             /* Position of token in zText */
+  zOut = pCsr->zToken;
+  do {
+    int iOut;
 
-          rc = pModule->xNext(pTC, &zToken, &nToken, &iDum1, &iDum2, &iPos);
-          for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
-            Fts3PhraseToken *pPT = pDef->pToken;
-            if( (pDef->iCol>=p->nColumn || pDef->iCol==i)
-                && (pPT->bFirst==0 || iPos==0)
-                && (pPT->n==nToken || (pPT->isPrefix && pPT->n<nToken))
-                && (0==memcmp(zToken, pPT->z, pPT->n))
-              ){
-              fts3PendingListAppend(&pDef->pList, iDocid, i, iPos, &rc);
-            }
-          }
-        }
-        if( pTC ) pModule->xClose(pTC);
-        if( rc==SQLITE_DONE ) rc = SQLITE_OK;
-      }
+    /* Grow the output buffer if required. */
+    if( (zOut-pCsr->zToken)>=(pCsr->nAlloc-4) ){
+      char *zNew = sqlite3_realloc(pCsr->zToken, pCsr->nAlloc+64);
+      if( !zNew ) return SQLITE_NOMEM;
+      zOut = &zNew[zOut - pCsr->zToken];
+      pCsr->zToken = zNew;
+      pCsr->nAlloc += 64;
     }
 
-    for(pDef=pCsr->pDeferred; pDef && rc==SQLITE_OK; pDef=pDef->pNext){
-      if( pDef->pList ){
-        rc = fts3PendingListAppendVarint(&pDef->pList, 0);
-      }
+    /* Write the folded case of the last character read to the output */
+    zEnd = z;
+    iOut = sqlite3FtsUnicodeFold(iCode, p->bRemoveDiacritic);
+    if( iOut ){
+      WRITE_UTF8(zOut, iOut);
     }
-  }
 
-  return rc;
+    /* If the cursor is not at EOF, read the next character */
+    if( z>=zTerm ) break;
+    READ_UTF8(z, zTerm, iCode);
+  }while( unicodeIsAlnum(p, iCode) 
+       || sqlite3FtsUnicodeIsdiacritic(iCode)
+  );
+
+  /* Set the output variables and return. */
+  pCsr->iOff = (int)(z - pCsr->aInput);
+  *paToken = pCsr->zToken;
+  *pnToken = (int)(zOut - pCsr->zToken);
+  *piStart = (int)(zStart - pCsr->aInput);
+  *piEnd = (int)(zEnd - pCsr->aInput);
+  *piPos = pCsr->iToken++;
+  return SQLITE_OK;
 }
 
-SQLITE_PRIVATE int sqlite3Fts3DeferredTokenList(
-  Fts3DeferredToken *p, 
-  char **ppData, 
-  int *pnData
-){
-  char *pRet;
-  int nSkip;
-  sqlite3_int64 dummy;
+/*
+** Set *ppModule to a pointer to the sqlite3_tokenizer_module 
+** structure for the unicode tokenizer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3UnicodeTokenizer(sqlite3_tokenizer_module const **ppModule){
+  static const sqlite3_tokenizer_module module = {
+    0,
+    unicodeCreate,
+    unicodeDestroy,
+    unicodeOpen,
+    unicodeClose,
+    unicodeNext,
+    0,
+  };
+  *ppModule = &module;
+}
 
-  *ppData = 0;
-  *pnData = 0;
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+#endif /* ifndef SQLITE_DISABLE_FTS3_UNICODE */
 
-  if( p->pList==0 ){
-    return SQLITE_OK;
-  }
+/************** End of fts3_unicode.c ****************************************/
+/************** Begin file fts3_unicode2.c ***********************************/
+/*
+** 2012 May 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+*/
 
-  pRet = (char *)sqlite3_malloc(p->pList->nData);
-  if( !pRet ) return SQLITE_NOMEM;
+/*
+** DO NOT EDIT THIS MACHINE GENERATED FILE.
+*/
 
-  nSkip = sqlite3Fts3GetVarint(p->pList->aData, &dummy);
-  *pnData = p->pList->nData - nSkip;
-  *ppData = pRet;
-  
-  memcpy(pRet, &p->pList->aData[nSkip], *pnData);
-  return SQLITE_OK;
-}
+#ifndef SQLITE_DISABLE_FTS3_UNICODE
+#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+
+/* #include <assert.h> */
 
 /*
-** Add an entry for token pToken to the pCsr->pDeferred list.
+** Return true if the argument corresponds to a unicode codepoint
+** classified as either a letter or a number. Otherwise false.
+**
+** The results are undefined if the value passed to this function
+** is less than zero.
 */
-SQLITE_PRIVATE int sqlite3Fts3DeferToken(
-  Fts3Cursor *pCsr,               /* Fts3 table cursor */
-  Fts3PhraseToken *pToken,        /* Token to defer */
-  int iCol                        /* Column that token must appear in (or -1) */
-){
-  Fts3DeferredToken *pDeferred;
-  pDeferred = sqlite3_malloc(sizeof(*pDeferred));
-  if( !pDeferred ){
-    return SQLITE_NOMEM;
-  }
-  memset(pDeferred, 0, sizeof(*pDeferred));
-  pDeferred->pToken = pToken;
-  pDeferred->pNext = pCsr->pDeferred; 
-  pDeferred->iCol = iCol;
-  pCsr->pDeferred = pDeferred;
-
-  assert( pToken->pDeferred==0 );
-  pToken->pDeferred = pDeferred;
+SQLITE_PRIVATE int sqlite3FtsUnicodeIsalnum(int c){
+  /* Each unsigned integer in the following array corresponds to a contiguous
+  ** range of unicode codepoints that are not either letters or numbers (i.e.
+  ** codepoints for which this function should return 0).
+  **
+  ** The most significant 22 bits in each 32-bit value contain the first 
+  ** codepoint in the range. The least significant 10 bits are used to store
+  ** the size of the range (always at least 1). In other words, the value 
+  ** ((C<<22) + N) represents a range of N codepoints starting with codepoint 
+  ** C. It is not possible to represent a range larger than 1023 codepoints 
+  ** using this format.
+  */
+  static const unsigned int aEntry[] = {
+    0x00000030, 0x0000E807, 0x00016C06, 0x0001EC2F, 0x0002AC07,
+    0x0002D001, 0x0002D803, 0x0002EC01, 0x0002FC01, 0x00035C01,
+    0x0003DC01, 0x000B0804, 0x000B480E, 0x000B9407, 0x000BB401,
+    0x000BBC81, 0x000DD401, 0x000DF801, 0x000E1002, 0x000E1C01,
+    0x000FD801, 0x00120808, 0x00156806, 0x00162402, 0x00163C01,
+    0x00164437, 0x0017CC02, 0x00180005, 0x00181816, 0x00187802,
+    0x00192C15, 0x0019A804, 0x0019C001, 0x001B5001, 0x001B580F,
+    0x001B9C07, 0x001BF402, 0x001C000E, 0x001C3C01, 0x001C4401,
+    0x001CC01B, 0x001E980B, 0x001FAC09, 0x001FD804, 0x00205804,
+    0x00206C09, 0x00209403, 0x0020A405, 0x0020C00F, 0x00216403,
+    0x00217801, 0x0023901B, 0x00240004, 0x0024E803, 0x0024F812,
+    0x00254407, 0x00258804, 0x0025C001, 0x00260403, 0x0026F001,
+    0x0026F807, 0x00271C02, 0x00272C03, 0x00275C01, 0x00278802,
+    0x0027C802, 0x0027E802, 0x00280403, 0x0028F001, 0x0028F805,
+    0x00291C02, 0x00292C03, 0x00294401, 0x0029C002, 0x0029D401,
+    0x002A0403, 0x002AF001, 0x002AF808, 0x002B1C03, 0x002B2C03,
+    0x002B8802, 0x002BC002, 0x002C0403, 0x002CF001, 0x002CF807,
+    0x002D1C02, 0x002D2C03, 0x002D5802, 0x002D8802, 0x002DC001,
+    0x002E0801, 0x002EF805, 0x002F1803, 0x002F2804, 0x002F5C01,
+    0x002FCC08, 0x00300403, 0x0030F807, 0x00311803, 0x00312804,
+    0x00315402, 0x00318802, 0x0031FC01, 0x00320802, 0x0032F001,
+    0x0032F807, 0x00331803, 0x00332804, 0x00335402, 0x00338802,
+    0x00340802, 0x0034F807, 0x00351803, 0x00352804, 0x00355C01,
+    0x00358802, 0x0035E401, 0x00360802, 0x00372801, 0x00373C06,
+    0x00375801, 0x00376008, 0x0037C803, 0x0038C401, 0x0038D007,
+    0x0038FC01, 0x00391C09, 0x00396802, 0x003AC401, 0x003AD006,
+    0x003AEC02, 0x003B2006, 0x003C041F, 0x003CD00C, 0x003DC417,
+    0x003E340B, 0x003E6424, 0x003EF80F, 0x003F380D, 0x0040AC14,
+    0x00412806, 0x00415804, 0x00417803, 0x00418803, 0x00419C07,
+    0x0041C404, 0x0042080C, 0x00423C01, 0x00426806, 0x0043EC01,
+    0x004D740C, 0x004E400A, 0x00500001, 0x0059B402, 0x005A0001,
+    0x005A6C02, 0x005BAC03, 0x005C4803, 0x005CC805, 0x005D4802,
+    0x005DC802, 0x005ED023, 0x005F6004, 0x005F7401, 0x0060000F,
+    0x0062A401, 0x0064800C, 0x0064C00C, 0x00650001, 0x00651002,
+    0x0066C011, 0x00672002, 0x00677822, 0x00685C05, 0x00687802,
+    0x0069540A, 0x0069801D, 0x0069FC01, 0x006A8007, 0x006AA006,
+    0x006C0005, 0x006CD011, 0x006D6823, 0x006E0003, 0x006E840D,
+    0x006F980E, 0x006FF004, 0x00709014, 0x0070EC05, 0x0071F802,
+    0x00730008, 0x00734019, 0x0073B401, 0x0073C803, 0x00770027,
+    0x0077F004, 0x007EF401, 0x007EFC03, 0x007F3403, 0x007F7403,
+    0x007FB403, 0x007FF402, 0x00800065, 0x0081A806, 0x0081E805,
+    0x00822805, 0x0082801A, 0x00834021, 0x00840002, 0x00840C04,
+    0x00842002, 0x00845001, 0x00845803, 0x00847806, 0x00849401,
+    0x00849C01, 0x0084A401, 0x0084B801, 0x0084E802, 0x00850005,
+    0x00852804, 0x00853C01, 0x00864264, 0x00900027, 0x0091000B,
+    0x0092704E, 0x00940200, 0x009C0475, 0x009E53B9, 0x00AD400A,
+    0x00B39406, 0x00B3BC03, 0x00B3E404, 0x00B3F802, 0x00B5C001,
+    0x00B5FC01, 0x00B7804F, 0x00B8C00C, 0x00BA001A, 0x00BA6C59,
+    0x00BC00D6, 0x00BFC00C, 0x00C00005, 0x00C02019, 0x00C0A807,
+    0x00C0D802, 0x00C0F403, 0x00C26404, 0x00C28001, 0x00C3EC01,
+    0x00C64002, 0x00C6580A, 0x00C70024, 0x00C8001F, 0x00C8A81E,
+    0x00C94001, 0x00C98020, 0x00CA2827, 0x00CB003F, 0x00CC0100,
+    0x01370040, 0x02924037, 0x0293F802, 0x02983403, 0x0299BC10,
+    0x029A7C01, 0x029BC008, 0x029C0017, 0x029C8002, 0x029E2402,
+    0x02A00801, 0x02A01801, 0x02A02C01, 0x02A08C09, 0x02A0D804,
+    0x02A1D004, 0x02A20002, 0x02A2D011, 0x02A33802, 0x02A38012,
+    0x02A3E003, 0x02A4980A, 0x02A51C0D, 0x02A57C01, 0x02A60004,
+    0x02A6CC1B, 0x02A77802, 0x02A8A40E, 0x02A90C01, 0x02A93002,
+    0x02A97004, 0x02A9DC03, 0x02A9EC01, 0x02AAC001, 0x02AAC803,
+    0x02AADC02, 0x02AAF802, 0x02AB0401, 0x02AB7802, 0x02ABAC07,
+    0x02ABD402, 0x02AF8C0B, 0x03600001, 0x036DFC02, 0x036FFC02,
+    0x037FFC01, 0x03EC7801, 0x03ECA401, 0x03EEC810, 0x03F4F802,
+    0x03F7F002, 0x03F8001A, 0x03F88007, 0x03F8C023, 0x03F95013,
+    0x03F9A004, 0x03FBFC01, 0x03FC040F, 0x03FC6807, 0x03FCEC06,
+    0x03FD6C0B, 0x03FF8007, 0x03FFA007, 0x03FFE405, 0x04040003,
+    0x0404DC09, 0x0405E411, 0x0406400C, 0x0407402E, 0x040E7C01,
+    0x040F4001, 0x04215C01, 0x04247C01, 0x0424FC01, 0x04280403,
+    0x04281402, 0x04283004, 0x0428E003, 0x0428FC01, 0x04294009,
+    0x0429FC01, 0x042CE407, 0x04400003, 0x0440E016, 0x04420003,
+    0x0442C012, 0x04440003, 0x04449C0E, 0x04450004, 0x04460003,
+    0x0446CC0E, 0x04471404, 0x045AAC0D, 0x0491C004, 0x05BD442E,
+    0x05BE3C04, 0x074000F6, 0x07440027, 0x0744A4B5, 0x07480046,
+    0x074C0057, 0x075B0401, 0x075B6C01, 0x075BEC01, 0x075C5401,
+    0x075CD401, 0x075D3C01, 0x075DBC01, 0x075E2401, 0x075EA401,
+    0x075F0C01, 0x07BBC002, 0x07C0002C, 0x07C0C064, 0x07C2800F,
+    0x07C2C40E, 0x07C3040F, 0x07C3440F, 0x07C4401F, 0x07C4C03C,
+    0x07C5C02B, 0x07C7981D, 0x07C8402B, 0x07C90009, 0x07C94002,
+    0x07CC0021, 0x07CCC006, 0x07CCDC46, 0x07CE0014, 0x07CE8025,
+    0x07CF1805, 0x07CF8011, 0x07D0003F, 0x07D10001, 0x07D108B6,
+    0x07D3E404, 0x07D4003E, 0x07D50004, 0x07D54018, 0x07D7EC46,
+    0x07D9140B, 0x07DA0046, 0x07DC0074, 0x38000401, 0x38008060,
+    0x380400F0,
+  };
+  static const unsigned int aAscii[4] = {
+    0xFFFFFFFF, 0xFC00FFFF, 0xF8000001, 0xF8000001,
+  };
 
-  return SQLITE_OK;
+  if( c<128 ){
+    return ( (aAscii[c >> 5] & (1 << (c & 0x001F)))==0 );
+  }else if( c<(1<<22) ){
+    unsigned int key = (((unsigned int)c)<<10) | 0x000003FF;
+    int iRes = 0;
+    int iHi = sizeof(aEntry)/sizeof(aEntry[0]) - 1;
+    int iLo = 0;
+    while( iHi>=iLo ){
+      int iTest = (iHi + iLo) / 2;
+      if( key >= aEntry[iTest] ){
+        iRes = iTest;
+        iLo = iTest+1;
+      }else{
+        iHi = iTest-1;
+      }
+    }
+    assert( aEntry[0]<key );
+    assert( key>=aEntry[iRes] );
+    return (((unsigned int)c) >= ((aEntry[iRes]>>10) + (aEntry[iRes]&0x3FF)));
+  }
+  return 1;
 }
-#endif
+
 
 /*
-** SQLite value pRowid contains the rowid of a row that may or may not be
-** present in the FTS3 table. If it is, delete it and adjust the contents
-** of subsiduary data structures accordingly.
+** If the argument is a codepoint corresponding to a lowercase letter
+** in the ASCII range with a diacritic added, return the codepoint
+** of the ASCII letter only. For example, if passed 235 - "LATIN
+** SMALL LETTER E WITH DIAERESIS" - return 65 ("LATIN SMALL LETTER
+** E"). The resuls of passing a codepoint that corresponds to an
+** uppercase letter are undefined.
 */
-static int fts3DeleteByRowid(
-  Fts3Table *p, 
-  sqlite3_value *pRowid, 
-  int *pnChng,                    /* IN/OUT: Decrement if row is deleted */
-  u32 *aSzDel
-){
-  int rc = SQLITE_OK;             /* Return code */
-  int bFound = 0;                 /* True if *pRowid really is in the table */
+static int remove_diacritic(int c){
+  unsigned short aDia[] = {
+        0,  1797,  1848,  1859,  1891,  1928,  1940,  1995, 
+     2024,  2040,  2060,  2110,  2168,  2206,  2264,  2286, 
+     2344,  2383,  2472,  2488,  2516,  2596,  2668,  2732, 
+     2782,  2842,  2894,  2954,  2984,  3000,  3028,  3336, 
+     3456,  3696,  3712,  3728,  3744,  3896,  3912,  3928, 
+     3968,  4008,  4040,  4106,  4138,  4170,  4202,  4234, 
+     4266,  4296,  4312,  4344,  4408,  4424,  4472,  4504, 
+     6148,  6198,  6264,  6280,  6360,  6429,  6505,  6529, 
+    61448, 61468, 61534, 61592, 61642, 61688, 61704, 61726, 
+    61784, 61800, 61836, 61880, 61914, 61948, 61998, 62122, 
+    62154, 62200, 62218, 62302, 62364, 62442, 62478, 62536, 
+    62554, 62584, 62604, 62640, 62648, 62656, 62664, 62730, 
+    62924, 63050, 63082, 63274, 63390, 
+  };
+  char aChar[] = {
+    '\0', 'a',  'c',  'e',  'i',  'n',  'o',  'u',  'y',  'y',  'a',  'c',  
+    'd',  'e',  'e',  'g',  'h',  'i',  'j',  'k',  'l',  'n',  'o',  'r',  
+    's',  't',  'u',  'u',  'w',  'y',  'z',  'o',  'u',  'a',  'i',  'o',  
+    'u',  'g',  'k',  'o',  'j',  'g',  'n',  'a',  'e',  'i',  'o',  'r',  
+    'u',  's',  't',  'h',  'a',  'e',  'o',  'y',  '\0', '\0', '\0', '\0', 
+    '\0', '\0', '\0', '\0', 'a',  'b',  'd',  'd',  'e',  'f',  'g',  'h',  
+    'h',  'i',  'k',  'l',  'l',  'm',  'n',  'p',  'r',  'r',  's',  't',  
+    'u',  'v',  'w',  'w',  'x',  'y',  'z',  'h',  't',  'w',  'y',  'a',  
+    'e',  'i',  'o',  'u',  'y',  
+  };
 
-  fts3DeleteTerms(&rc, p, pRowid, aSzDel, &bFound);
-  if( bFound && rc==SQLITE_OK ){
-    int isEmpty = 0;              /* Deleting *pRowid leaves the table empty */
-    rc = fts3IsEmpty(p, pRowid, &isEmpty);
-    if( rc==SQLITE_OK ){
-      if( isEmpty ){
-        /* Deleting this row means the whole table is empty. In this case
-        ** delete the contents of all three tables and throw away any
-        ** data in the pendingTerms hash table.  */
-        rc = fts3DeleteAll(p, 1);
-        *pnChng = 0;
-        memset(aSzDel, 0, sizeof(u32) * (p->nColumn+1) * 2);
-      }else{
-        *pnChng = *pnChng - 1;
-        if( p->zContentTbl==0 ){
-          fts3SqlExec(&rc, p, SQL_DELETE_CONTENT, &pRowid);
-        }
-        if( p->bHasDocsize ){
-          fts3SqlExec(&rc, p, SQL_DELETE_DOCSIZE, &pRowid);
-        }
-      }
+  unsigned int key = (((unsigned int)c)<<3) | 0x00000007;
+  int iRes = 0;
+  int iHi = sizeof(aDia)/sizeof(aDia[0]) - 1;
+  int iLo = 0;
+  while( iHi>=iLo ){
+    int iTest = (iHi + iLo) / 2;
+    if( key >= aDia[iTest] ){
+      iRes = iTest;
+      iLo = iTest+1;
+    }else{
+      iHi = iTest-1;
     }
   }
-
-  return rc;
+  assert( key>=aDia[iRes] );
+  return ((c > (aDia[iRes]>>3) + (aDia[iRes]&0x07)) ? c : (int)aChar[iRes]);
 }
 
+
 /*
-** This function does the work for the xUpdate method of FTS3 virtual
-** tables. The schema of the virtual table being:
-**
-**     CREATE TABLE <table name>( 
-**       <user columns>,
-**       <table name> HIDDEN, 
-**       docid HIDDEN, 
-**       <langid> HIDDEN
-**     );
-**
-** 
+** Return true if the argument interpreted as a unicode codepoint
+** is a diacritical modifier character.
 */
-SQLITE_PRIVATE int sqlite3Fts3UpdateMethod(
-  sqlite3_vtab *pVtab,            /* FTS3 vtab object */
-  int nArg,                       /* Size of argument array */
-  sqlite3_value **apVal,          /* Array of arguments */
-  sqlite_int64 *pRowid            /* OUT: The affected (or effected) rowid */
-){
-  Fts3Table *p = (Fts3Table *)pVtab;
-  int rc = SQLITE_OK;             /* Return Code */
-  int isRemove = 0;               /* True for an UPDATE or DELETE */
-  u32 *aSzIns = 0;                /* Sizes of inserted documents */
-  u32 *aSzDel = 0;                /* Sizes of deleted documents */
-  int nChng = 0;                  /* Net change in number of documents */
-  int bInsertDone = 0;
-
-  /* At this point it must be known if the %_stat table exists or not.
-  ** So bHasStat may not be 2.  */
-  assert( p->bHasStat==0 || p->bHasStat==1 );
+SQLITE_PRIVATE int sqlite3FtsUnicodeIsdiacritic(int c){
+  unsigned int mask0 = 0x08029FDF;
+  unsigned int mask1 = 0x000361F8;
+  if( c<768 || c>817 ) return 0;
+  return (c < 768+32) ?
+      (mask0 & (1 << (c-768))) :
+      (mask1 & (1 << (c-768-32)));
+}
 
-  assert( p->pSegments==0 );
-  assert( 
-      nArg==1                     /* DELETE operations */
-   || nArg==(2 + p->nColumn + 3)  /* INSERT or UPDATE operations */
-  );
 
-  /* Check for a "special" INSERT operation. One of the form:
+/*
+** Interpret the argument as a unicode codepoint. If the codepoint
+** is an upper case character that has a lower case equivalent,
+** return the codepoint corresponding to the lower case version.
+** Otherwise, return a copy of the argument.
+**
+** The results are undefined if the value passed to this function
+** is less than zero.
+*/
+SQLITE_PRIVATE int sqlite3FtsUnicodeFold(int c, int bRemoveDiacritic){
+  /* Each entry in the following array defines a rule for folding a range
+  ** of codepoints to lower case. The rule applies to a range of nRange
+  ** codepoints starting at codepoint iCode.
   **
-  **   INSERT INTO xyz(xyz) VALUES('command');
+  ** If the least significant bit in flags is clear, then the rule applies
+  ** to all nRange codepoints (i.e. all nRange codepoints are upper case and
+  ** need to be folded). Or, if it is set, then the rule only applies to
+  ** every second codepoint in the range, starting with codepoint C.
+  **
+  ** The 7 most significant bits in flags are an index into the aiOff[]
+  ** array. If a specific codepoint C does require folding, then its lower
+  ** case equivalent is ((C + aiOff[flags>>1]) & 0xFFFF).
+  **
+  ** The contents of this array are generated by parsing the CaseFolding.txt
+  ** file distributed as part of the "Unicode Character Database". See
+  ** http://www.unicode.org for details.
   */
-  if( nArg>1 
-   && sqlite3_value_type(apVal[0])==SQLITE_NULL 
-   && sqlite3_value_type(apVal[p->nColumn+2])!=SQLITE_NULL 
-  ){
-    rc = fts3SpecialInsert(p, apVal[p->nColumn+2]);
-    goto update_out;
-  }
-
-  if( nArg>1 && sqlite3_value_int(apVal[2 + p->nColumn + 2])<0 ){
-    rc = SQLITE_CONSTRAINT;
-    goto update_out;
-  }
+  static const struct TableEntry {
+    unsigned short iCode;
+    unsigned char flags;
+    unsigned char nRange;
+  } aEntry[] = {
+    {65, 14, 26},          {181, 64, 1},          {192, 14, 23},
+    {216, 14, 7},          {256, 1, 48},          {306, 1, 6},
+    {313, 1, 16},          {330, 1, 46},          {376, 116, 1},
+    {377, 1, 6},           {383, 104, 1},         {385, 50, 1},
+    {386, 1, 4},           {390, 44, 1},          {391, 0, 1},
+    {393, 42, 2},          {395, 0, 1},           {398, 32, 1},
+    {399, 38, 1},          {400, 40, 1},          {401, 0, 1},
+    {403, 42, 1},          {404, 46, 1},          {406, 52, 1},
+    {407, 48, 1},          {408, 0, 1},           {412, 52, 1},
+    {413, 54, 1},          {415, 56, 1},          {416, 1, 6},
+    {422, 60, 1},          {423, 0, 1},           {425, 60, 1},
+    {428, 0, 1},           {430, 60, 1},          {431, 0, 1},
+    {433, 58, 2},          {435, 1, 4},           {439, 62, 1},
+    {440, 0, 1},           {444, 0, 1},           {452, 2, 1},
+    {453, 0, 1},           {455, 2, 1},           {456, 0, 1},
+    {458, 2, 1},           {459, 1, 18},          {478, 1, 18},
+    {497, 2, 1},           {498, 1, 4},           {502, 122, 1},
+    {503, 134, 1},         {504, 1, 40},          {544, 110, 1},
+    {546, 1, 18},          {570, 70, 1},          {571, 0, 1},
+    {573, 108, 1},         {574, 68, 1},          {577, 0, 1},
+    {579, 106, 1},         {580, 28, 1},          {581, 30, 1},
+    {582, 1, 10},          {837, 36, 1},          {880, 1, 4},
+    {886, 0, 1},           {902, 18, 1},          {904, 16, 3},
+    {908, 26, 1},          {910, 24, 2},          {913, 14, 17},
+    {931, 14, 9},          {962, 0, 1},           {975, 4, 1},
+    {976, 140, 1},         {977, 142, 1},         {981, 146, 1},
+    {982, 144, 1},         {984, 1, 24},          {1008, 136, 1},
+    {1009, 138, 1},        {1012, 130, 1},        {1013, 128, 1},
+    {1015, 0, 1},          {1017, 152, 1},        {1018, 0, 1},
+    {1021, 110, 3},        {1024, 34, 16},        {1040, 14, 32},
+    {1120, 1, 34},         {1162, 1, 54},         {1216, 6, 1},
+    {1217, 1, 14},         {1232, 1, 88},         {1329, 22, 38},
+    {4256, 66, 38},        {4295, 66, 1},         {4301, 66, 1},
+    {7680, 1, 150},        {7835, 132, 1},        {7838, 96, 1},
+    {7840, 1, 96},         {7944, 150, 8},        {7960, 150, 6},
+    {7976, 150, 8},        {7992, 150, 8},        {8008, 150, 6},
+    {8025, 151, 8},        {8040, 150, 8},        {8072, 150, 8},
+    {8088, 150, 8},        {8104, 150, 8},        {8120, 150, 2},
+    {8122, 126, 2},        {8124, 148, 1},        {8126, 100, 1},
+    {8136, 124, 4},        {8140, 148, 1},        {8152, 150, 2},
+    {8154, 120, 2},        {8168, 150, 2},        {8170, 118, 2},
+    {8172, 152, 1},        {8184, 112, 2},        {8186, 114, 2},
+    {8188, 148, 1},        {8486, 98, 1},         {8490, 92, 1},
+    {8491, 94, 1},         {8498, 12, 1},         {8544, 8, 16},
+    {8579, 0, 1},          {9398, 10, 26},        {11264, 22, 47},
+    {11360, 0, 1},         {11362, 88, 1},        {11363, 102, 1},
+    {11364, 90, 1},        {11367, 1, 6},         {11373, 84, 1},
+    {11374, 86, 1},        {11375, 80, 1},        {11376, 82, 1},
+    {11378, 0, 1},         {11381, 0, 1},         {11390, 78, 2},
+    {11392, 1, 100},       {11499, 1, 4},         {11506, 0, 1},
+    {42560, 1, 46},        {42624, 1, 24},        {42786, 1, 14},
+    {42802, 1, 62},        {42873, 1, 4},         {42877, 76, 1},
+    {42878, 1, 10},        {42891, 0, 1},         {42893, 74, 1},
+    {42896, 1, 4},         {42912, 1, 10},        {42922, 72, 1},
+    {65313, 14, 26},       
+  };
+  static const unsigned short aiOff[] = {
+   1,     2,     8,     15,    16,    26,    28,    32,    
+   37,    38,    40,    48,    63,    64,    69,    71,    
+   79,    80,    116,   202,   203,   205,   206,   207,   
+   209,   210,   211,   213,   214,   217,   218,   219,   
+   775,   7264,  10792, 10795, 23228, 23256, 30204, 54721, 
+   54753, 54754, 54756, 54787, 54793, 54809, 57153, 57274, 
+   57921, 58019, 58363, 61722, 65268, 65341, 65373, 65406, 
+   65408, 65410, 65415, 65424, 65436, 65439, 65450, 65462, 
+   65472, 65476, 65478, 65480, 65482, 65488, 65506, 65511, 
+   65514, 65521, 65527, 65528, 65529, 
+  };
 
-  /* Allocate space to hold the change in document sizes */
-  aSzDel = sqlite3_malloc( sizeof(aSzDel[0])*(p->nColumn+1)*2 );
-  if( aSzDel==0 ){
-    rc = SQLITE_NOMEM;
-    goto update_out;
-  }
-  aSzIns = &aSzDel[p->nColumn+1];
-  memset(aSzDel, 0, sizeof(aSzDel[0])*(p->nColumn+1)*2);
+  int ret = c;
 
-  rc = fts3Writelock(p);
-  if( rc!=SQLITE_OK ) goto update_out;
+  assert( c>=0 );
+  assert( sizeof(unsigned short)==2 && sizeof(unsigned char)==1 );
 
-  /* If this is an INSERT operation, or an UPDATE that modifies the rowid
-  ** value, then this operation requires constraint handling.
-  **
-  ** If the on-conflict mode is REPLACE, this means that the existing row
-  ** should be deleted from the database before inserting the new row. Or,
-  ** if the on-conflict mode is other than REPLACE, then this method must
-  ** detect the conflict and return SQLITE_CONSTRAINT before beginning to
-  ** modify the database file.
-  */
-  if( nArg>1 && p->zContentTbl==0 ){
-    /* Find the value object that holds the new rowid value. */
-    sqlite3_value *pNewRowid = apVal[3+p->nColumn];
-    if( sqlite3_value_type(pNewRowid)==SQLITE_NULL ){
-      pNewRowid = apVal[1];
-    }
+  if( c<128 ){
+    if( c>='A' && c<='Z' ) ret = c + ('a' - 'A');
+  }else if( c<65536 ){
+    int iHi = sizeof(aEntry)/sizeof(aEntry[0]) - 1;
+    int iLo = 0;
+    int iRes = -1;
 
-    if( sqlite3_value_type(pNewRowid)!=SQLITE_NULL && ( 
-        sqlite3_value_type(apVal[0])==SQLITE_NULL
-     || sqlite3_value_int64(apVal[0])!=sqlite3_value_int64(pNewRowid)
-    )){
-      /* The new rowid is not NULL (in this case the rowid will be
-      ** automatically assigned and there is no chance of a conflict), and 
-      ** the statement is either an INSERT or an UPDATE that modifies the
-      ** rowid column. So if the conflict mode is REPLACE, then delete any
-      ** existing row with rowid=pNewRowid. 
-      **
-      ** Or, if the conflict mode is not REPLACE, insert the new record into 
-      ** the %_content table. If we hit the duplicate rowid constraint (or any
-      ** other error) while doing so, return immediately.
-      **
-      ** This branch may also run if pNewRowid contains a value that cannot
-      ** be losslessly converted to an integer. In this case, the eventual 
-      ** call to fts3InsertData() (either just below or further on in this
-      ** function) will return SQLITE_MISMATCH. If fts3DeleteByRowid is 
-      ** invoked, it will delete zero rows (since no row will have
-      ** docid=$pNewRowid if $pNewRowid is not an integer value).
-      */
-      if( sqlite3_vtab_on_conflict(p->db)==SQLITE_REPLACE ){
-        rc = fts3DeleteByRowid(p, pNewRowid, &nChng, aSzDel);
+    while( iHi>=iLo ){
+      int iTest = (iHi + iLo) / 2;
+      int cmp = (c - aEntry[iTest].iCode);
+      if( cmp>=0 ){
+        iRes = iTest;
+        iLo = iTest+1;
       }else{
-        rc = fts3InsertData(p, apVal, pRowid);
-        bInsertDone = 1;
+        iHi = iTest-1;
       }
     }
-  }
-  if( rc!=SQLITE_OK ){
-    goto update_out;
-  }
+    assert( iRes<0 || c>=aEntry[iRes].iCode );
 
-  /* If this is a DELETE or UPDATE operation, remove the old record. */
-  if( sqlite3_value_type(apVal[0])!=SQLITE_NULL ){
-    assert( sqlite3_value_type(apVal[0])==SQLITE_INTEGER );
-    rc = fts3DeleteByRowid(p, apVal[0], &nChng, aSzDel);
-    isRemove = 1;
-  }
-  
-  /* If this is an INSERT or UPDATE operation, insert the new record. */
-  if( nArg>1 && rc==SQLITE_OK ){
-    int iLangid = sqlite3_value_int(apVal[2 + p->nColumn + 2]);
-    if( bInsertDone==0 ){
-      rc = fts3InsertData(p, apVal, pRowid);
-      if( rc==SQLITE_CONSTRAINT && p->zContentTbl==0 ){
-        rc = FTS_CORRUPT_VTAB;
+    if( iRes>=0 ){
+      const struct TableEntry *p = &aEntry[iRes];
+      if( c<(p->iCode + p->nRange) && 0==(0x01 & p->flags & (p->iCode ^ c)) ){
+        ret = (c + (aiOff[p->flags>>1])) & 0x0000FFFF;
+        assert( ret>0 );
       }
     }
-    if( rc==SQLITE_OK && (!isRemove || *pRowid!=p->iPrevDocid ) ){
-      rc = fts3PendingTermsDocid(p, iLangid, *pRowid);
-    }
-    if( rc==SQLITE_OK ){
-      assert( p->iPrevDocid==*pRowid );
-      rc = fts3InsertTerms(p, iLangid, apVal, aSzIns);
-    }
-    if( p->bHasDocsize ){
-      fts3InsertDocsize(&rc, p, aSzIns);
-    }
-    nChng++;
-  }
 
-  if( p->bFts4 ){
-    fts3UpdateDocTotals(&rc, p, aSzIns, aSzDel, nChng);
+    if( bRemoveDiacritic ) ret = remove_diacritic(ret);
   }
-
- update_out:
-  sqlite3_free(aSzDel);
-  sqlite3Fts3SegmentsClose(p);
-  return rc;
-}
-
-/* 
-** Flush any data in the pending-terms hash table to disk. If successful,
-** merge all segments in the database (including the new segment, if 
-** there was any data to flush) into a single segment. 
-*/
-SQLITE_PRIVATE int sqlite3Fts3Optimize(Fts3Table *p){
-  int rc;
-  rc = sqlite3_exec(p->db, "SAVEPOINT fts3", 0, 0, 0);
-  if( rc==SQLITE_OK ){
-    rc = fts3DoOptimize(p, 1);
-    if( rc==SQLITE_OK || rc==SQLITE_DONE ){
-      int rc2 = sqlite3_exec(p->db, "RELEASE fts3", 0, 0, 0);
-      if( rc2!=SQLITE_OK ) rc = rc2;
-    }else{
-      sqlite3_exec(p->db, "ROLLBACK TO fts3", 0, 0, 0);
-      sqlite3_exec(p->db, "RELEASE fts3", 0, 0, 0);
-    }
+  
+  else if( c>=66560 && c<66600 ){
+    ret = c + 40;
   }
-  sqlite3Fts3SegmentsClose(p);
-  return rc;
-}
 
-#endif
+  return ret;
+}
+#endif /* defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4) */
+#endif /* !defined(SQLITE_DISABLE_FTS3_UNICODE) */
 
-/************** End of fts3_write.c ******************************************/
-/************** Begin file fts3_snippet.c ************************************/
+/************** End of fts3_unicode2.c ***************************************/
+/************** Begin file rtree.c *******************************************/
 /*
-** 2009 Oct 23
+** 2001 September 15
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
@@ -148633,6585 +152601,8372 @@ SQLITE_PRIVATE int sqlite3Fts3Optimize(Fts3Table *p){
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
-******************************************************************************
+*************************************************************************
+** This file contains code for implementations of the r-tree and r*-tree
+** algorithms packaged as an SQLite virtual table module.
 */
 
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+/*
+** Database Format of R-Tree Tables
+** --------------------------------
+**
+** The data structure for a single virtual r-tree table is stored in three 
+** native SQLite tables declared as follows. In each case, the '%' character
+** in the table name is replaced with the user-supplied name of the r-tree
+** table.
+**
+**   CREATE TABLE %_node(nodeno INTEGER PRIMARY KEY, data BLOB)
+**   CREATE TABLE %_parent(nodeno INTEGER PRIMARY KEY, parentnode INTEGER)
+**   CREATE TABLE %_rowid(rowid INTEGER PRIMARY KEY, nodeno INTEGER)
+**
+** The data for each node of the r-tree structure is stored in the %_node
+** table. For each node that is not the root node of the r-tree, there is
+** an entry in the %_parent table associating the node with its parent.
+** And for each row of data in the table, there is an entry in the %_rowid
+** table that maps from the entries rowid to the id of the node that it
+** is stored on.
+**
+** The root node of an r-tree always exists, even if the r-tree table is
+** empty. The nodeno of the root node is always 1. All other nodes in the
+** table must be the same size as the root node. The content of each node
+** is formatted as follows:
+**
+**   1. If the node is the root node (node 1), then the first 2 bytes
+**      of the node contain the tree depth as a big-endian integer.
+**      For non-root nodes, the first 2 bytes are left unused.
+**
+**   2. The next 2 bytes contain the number of entries currently 
+**      stored in the node.
+**
+**   3. The remainder of the node contains the node entries. Each entry
+**      consists of a single 8-byte integer followed by an even number
+**      of 4-byte coordinates. For leaf nodes the integer is the rowid
+**      of a record. For internal nodes it is the node number of a
+**      child page.
+*/
+
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RTREE)
+
+#ifndef SQLITE_CORE
+/*   #include "sqlite3ext.h" */
+  SQLITE_EXTENSION_INIT1
+#else
+/*   #include "sqlite3.h" */
+#endif
 
 /* #include <string.h> */
 /* #include <assert.h> */
+/* #include <stdio.h> */
 
-/*
-** Characters that may appear in the second argument to matchinfo().
-*/
-#define FTS3_MATCHINFO_NPHRASE   'p'        /* 1 value */
-#define FTS3_MATCHINFO_NCOL      'c'        /* 1 value */
-#define FTS3_MATCHINFO_NDOC      'n'        /* 1 value */
-#define FTS3_MATCHINFO_AVGLENGTH 'a'        /* nCol values */
-#define FTS3_MATCHINFO_LENGTH    'l'        /* nCol values */
-#define FTS3_MATCHINFO_LCS       's'        /* nCol values */
-#define FTS3_MATCHINFO_HITS      'x'        /* 3*nCol*nPhrase values */
-#define FTS3_MATCHINFO_LHITS     'y'        /* nCol*nPhrase values */
+#ifndef SQLITE_AMALGAMATION
+#include "sqlite3rtree.h"
+typedef sqlite3_int64 i64;
+typedef unsigned char u8;
+typedef unsigned short u16;
+typedef unsigned int u32;
+#endif
 
-/*
-** The default value for the second argument to matchinfo(). 
+/*  The following macro is used to suppress compiler warnings.
 */
-#define FTS3_MATCHINFO_DEFAULT   "pcx"
+#ifndef UNUSED_PARAMETER
+# define UNUSED_PARAMETER(x) (void)(x)
+#endif
+
+typedef struct Rtree Rtree;
+typedef struct RtreeCursor RtreeCursor;
+typedef struct RtreeNode RtreeNode;
+typedef struct RtreeCell RtreeCell;
+typedef struct RtreeConstraint RtreeConstraint;
+typedef struct RtreeMatchArg RtreeMatchArg;
+typedef struct RtreeGeomCallback RtreeGeomCallback;
+typedef union RtreeCoord RtreeCoord;
+typedef struct RtreeSearchPoint RtreeSearchPoint;
 
+/* The rtree may have between 1 and RTREE_MAX_DIMENSIONS dimensions. */
+#define RTREE_MAX_DIMENSIONS 5
 
-/*
-** Used as an fts3ExprIterate() context when loading phrase doclists to
-** Fts3Expr.aDoclist[]/nDoclist.
+/* Size of hash table Rtree.aHash. This hash table is not expected to
+** ever contain very many entries, so a fixed number of buckets is 
+** used.
 */
-typedef struct LoadDoclistCtx LoadDoclistCtx;
-struct LoadDoclistCtx {
-  Fts3Cursor *pCsr;               /* FTS3 Cursor */
-  int nPhrase;                    /* Number of phrases seen so far */
-  int nToken;                     /* Number of tokens seen so far */
-};
+#define HASHSIZE 97
 
-/*
-** The following types are used as part of the implementation of the 
-** fts3BestSnippet() routine.
+/* The xBestIndex method of this virtual table requires an estimate of
+** the number of rows in the virtual table to calculate the costs of
+** various strategies. If possible, this estimate is loaded from the
+** sqlite_stat1 table (with RTREE_MIN_ROWEST as a hard-coded minimum).
+** Otherwise, if no sqlite_stat1 entry is available, use 
+** RTREE_DEFAULT_ROWEST.
 */
-typedef struct SnippetIter SnippetIter;
-typedef struct SnippetPhrase SnippetPhrase;
-typedef struct SnippetFragment SnippetFragment;
+#define RTREE_DEFAULT_ROWEST 1048576
+#define RTREE_MIN_ROWEST         100
 
-struct SnippetIter {
-  Fts3Cursor *pCsr;               /* Cursor snippet is being generated from */
-  int iCol;                       /* Extract snippet from this column */
-  int nSnippet;                   /* Requested snippet length (in tokens) */
-  int nPhrase;                    /* Number of phrases in query */
-  SnippetPhrase *aPhrase;         /* Array of size nPhrase */
-  int iCurrent;                   /* First token of current snippet */
-};
+/* 
+** An rtree virtual-table object.
+*/
+struct Rtree {
+  sqlite3_vtab base;          /* Base class.  Must be first */
+  sqlite3 *db;                /* Host database connection */
+  int iNodeSize;              /* Size in bytes of each node in the node table */
+  u8 nDim;                    /* Number of dimensions */
+  u8 eCoordType;              /* RTREE_COORD_REAL32 or RTREE_COORD_INT32 */
+  u8 nBytesPerCell;           /* Bytes consumed per cell */
+  int iDepth;                 /* Current depth of the r-tree structure */
+  char *zDb;                  /* Name of database containing r-tree table */
+  char *zName;                /* Name of r-tree table */ 
+  int nBusy;                  /* Current number of users of this structure */
+  i64 nRowEst;                /* Estimated number of rows in this table */
 
-struct SnippetPhrase {
-  int nToken;                     /* Number of tokens in phrase */
-  char *pList;                    /* Pointer to start of phrase position list */
-  int iHead;                      /* Next value in position list */
-  char *pHead;                    /* Position list data following iHead */
-  int iTail;                      /* Next value in trailing position list */
-  char *pTail;                    /* Position list data following iTail */
-};
+  /* List of nodes removed during a CondenseTree operation. List is
+  ** linked together via the pointer normally used for hash chains -
+  ** RtreeNode.pNext. RtreeNode.iNode stores the depth of the sub-tree 
+  ** headed by the node (leaf nodes have RtreeNode.iNode==0).
+  */
+  RtreeNode *pDeleted;
+  int iReinsertHeight;        /* Height of sub-trees Reinsert() has run on */
 
-struct SnippetFragment {
-  int iCol;                       /* Column snippet is extracted from */
-  int iPos;                       /* Index of first token in snippet */
-  u64 covered;                    /* Mask of query phrases covered */
-  u64 hlmask;                     /* Mask of snippet terms to highlight */
-};
+  /* Statements to read/write/delete a record from xxx_node */
+  sqlite3_stmt *pReadNode;
+  sqlite3_stmt *pWriteNode;
+  sqlite3_stmt *pDeleteNode;
 
-/*
-** This type is used as an fts3ExprIterate() context object while 
-** accumulating the data returned by the matchinfo() function.
-*/
-typedef struct MatchInfo MatchInfo;
-struct MatchInfo {
-  Fts3Cursor *pCursor;            /* FTS3 Cursor */
-  int nCol;                       /* Number of columns in table */
-  int nPhrase;                    /* Number of matchable phrases in query */
-  sqlite3_int64 nDoc;             /* Number of docs in database */
-  u32 *aMatchinfo;                /* Pre-allocated buffer */
+  /* Statements to read/write/delete a record from xxx_rowid */
+  sqlite3_stmt *pReadRowid;
+  sqlite3_stmt *pWriteRowid;
+  sqlite3_stmt *pDeleteRowid;
+
+  /* Statements to read/write/delete a record from xxx_parent */
+  sqlite3_stmt *pReadParent;
+  sqlite3_stmt *pWriteParent;
+  sqlite3_stmt *pDeleteParent;
+
+  RtreeNode *aHash[HASHSIZE]; /* Hash table of in-memory nodes. */ 
 };
 
+/* Possible values for Rtree.eCoordType: */
+#define RTREE_COORD_REAL32 0
+#define RTREE_COORD_INT32  1
 
+/*
+** If SQLITE_RTREE_INT_ONLY is defined, then this virtual table will
+** only deal with integer coordinates.  No floating point operations
+** will be done.
+*/
+#ifdef SQLITE_RTREE_INT_ONLY
+  typedef sqlite3_int64 RtreeDValue;       /* High accuracy coordinate */
+  typedef int RtreeValue;                  /* Low accuracy coordinate */
+# define RTREE_ZERO 0
+#else
+  typedef double RtreeDValue;              /* High accuracy coordinate */
+  typedef float RtreeValue;                /* Low accuracy coordinate */
+# define RTREE_ZERO 0.0
+#endif
 
 /*
-** The snippet() and offsets() functions both return text values. An instance
-** of the following structure is used to accumulate those values while the
-** functions are running. See fts3StringAppend() for details.
+** When doing a search of an r-tree, instances of the following structure
+** record intermediate results from the tree walk.
+**
+** The id is always a node-id.  For iLevel>=1 the id is the node-id of
+** the node that the RtreeSearchPoint represents.  When iLevel==0, however,
+** the id is of the parent node and the cell that RtreeSearchPoint
+** represents is the iCell-th entry in the parent node.
 */
-typedef struct StrBuffer StrBuffer;
-struct StrBuffer {
-  char *z;                        /* Pointer to buffer containing string */
-  int n;                          /* Length of z in bytes (excl. nul-term) */
-  int nAlloc;                     /* Allocated size of buffer z in bytes */
+struct RtreeSearchPoint {
+  RtreeDValue rScore;    /* The score for this node.  Smallest goes first. */
+  sqlite3_int64 id;      /* Node ID */
+  u8 iLevel;             /* 0=entries.  1=leaf node.  2+ for higher */
+  u8 eWithin;            /* PARTLY_WITHIN or FULLY_WITHIN */
+  u8 iCell;              /* Cell index within the node */
 };
 
-
 /*
-** This function is used to help iterate through a position-list. A position
-** list is a list of unique integers, sorted from smallest to largest. Each
-** element of the list is represented by an FTS3 varint that takes the value
-** of the difference between the current element and the previous one plus
-** two. For example, to store the position-list:
-**
-**     4 9 113
-**
-** the three varints:
-**
-**     6 7 106
+** The minimum number of cells allowed for a node is a third of the 
+** maximum. In Gutman's notation:
 **
-** are encoded.
+**     m = M/3
 **
-** When this function is called, *pp points to the start of an element of
-** the list. *piPos contains the value of the previous entry in the list.
-** After it returns, *piPos contains the value of the next element of the
-** list and *pp is advanced to the following varint.
+** If an R*-tree "Reinsert" operation is required, the same number of
+** cells are removed from the overfull node and reinserted into the tree.
 */
-static void fts3GetDeltaPosition(char **pp, int *piPos){
-  int iVal;
-  *pp += fts3GetVarint32(*pp, &iVal);
-  *piPos += (iVal-2);
-}
+#define RTREE_MINCELLS(p) ((((p)->iNodeSize-4)/(p)->nBytesPerCell)/3)
+#define RTREE_REINSERT(p) RTREE_MINCELLS(p)
+#define RTREE_MAXCELLS 51
 
 /*
-** Helper function for fts3ExprIterate() (see below).
+** The smallest possible node-size is (512-64)==448 bytes. And the largest
+** supported cell size is 48 bytes (8 byte rowid + ten 4 byte coordinates).
+** Therefore all non-root nodes must contain at least 3 entries. Since 
+** 2^40 is greater than 2^64, an r-tree structure always has a depth of
+** 40 or less.
 */
-static int fts3ExprIterate2(
-  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
-  int *piPhrase,                  /* Pointer to phrase counter */
-  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
-  void *pCtx                      /* Second argument to pass to callback */
-){
-  int rc;                         /* Return code */
-  int eType = pExpr->eType;       /* Type of expression node pExpr */
+#define RTREE_MAX_DEPTH 40
 
-  if( eType!=FTSQUERY_PHRASE ){
-    assert( pExpr->pLeft && pExpr->pRight );
-    rc = fts3ExprIterate2(pExpr->pLeft, piPhrase, x, pCtx);
-    if( rc==SQLITE_OK && eType!=FTSQUERY_NOT ){
-      rc = fts3ExprIterate2(pExpr->pRight, piPhrase, x, pCtx);
-    }
-  }else{
-    rc = x(pExpr, *piPhrase, pCtx);
-    (*piPhrase)++;
-  }
-  return rc;
-}
 
 /*
-** Iterate through all phrase nodes in an FTS3 query, except those that
-** are part of a sub-tree that is the right-hand-side of a NOT operator.
-** For each phrase node found, the supplied callback function is invoked.
-**
-** If the callback function returns anything other than SQLITE_OK, 
-** the iteration is abandoned and the error code returned immediately.
-** Otherwise, SQLITE_OK is returned after a callback has been made for
-** all eligible phrase nodes.
+** Number of entries in the cursor RtreeNode cache.  The first entry is
+** used to cache the RtreeNode for RtreeCursor.sPoint.  The remaining
+** entries cache the RtreeNode for the first elements of the priority queue.
 */
-static int fts3ExprIterate(
-  Fts3Expr *pExpr,                /* Expression to iterate phrases of */
-  int (*x)(Fts3Expr*,int,void*),  /* Callback function to invoke for phrases */
-  void *pCtx                      /* Second argument to pass to callback */
-){
-  int iPhrase = 0;                /* Variable used as the phrase counter */
-  return fts3ExprIterate2(pExpr, &iPhrase, x, pCtx);
-}
+#define RTREE_CACHE_SZ  5
 
-/*
-** This is an fts3ExprIterate() callback used while loading the doclists
-** for each phrase into Fts3Expr.aDoclist[]/nDoclist. See also
-** fts3ExprLoadDoclists().
+/* 
+** An rtree cursor object.
 */
-static int fts3ExprLoadDoclistsCb(Fts3Expr *pExpr, int iPhrase, void *ctx){
-  int rc = SQLITE_OK;
-  Fts3Phrase *pPhrase = pExpr->pPhrase;
-  LoadDoclistCtx *p = (LoadDoclistCtx *)ctx;
-
-  UNUSED_PARAMETER(iPhrase);
-
-  p->nPhrase++;
-  p->nToken += pPhrase->nToken;
+struct RtreeCursor {
+  sqlite3_vtab_cursor base;         /* Base class.  Must be first */
+  u8 atEOF;                         /* True if at end of search */
+  u8 bPoint;                        /* True if sPoint is valid */
+  int iStrategy;                    /* Copy of idxNum search parameter */
+  int nConstraint;                  /* Number of entries in aConstraint */
+  RtreeConstraint *aConstraint;     /* Search constraints. */
+  int nPointAlloc;                  /* Number of slots allocated for aPoint[] */
+  int nPoint;                       /* Number of slots used in aPoint[] */
+  int mxLevel;                      /* iLevel value for root of the tree */
+  RtreeSearchPoint *aPoint;         /* Priority queue for search points */
+  RtreeSearchPoint sPoint;          /* Cached next search point */
+  RtreeNode *aNode[RTREE_CACHE_SZ]; /* Rtree node cache */
+  u32 anQueue[RTREE_MAX_DEPTH+1];   /* Number of queued entries by iLevel */
+};
 
-  return rc;
-}
+/* Return the Rtree of a RtreeCursor */
+#define RTREE_OF_CURSOR(X)   ((Rtree*)((X)->base.pVtab))
 
 /*
-** Load the doclists for each phrase in the query associated with FTS3 cursor
-** pCsr. 
-**
-** If pnPhrase is not NULL, then *pnPhrase is set to the number of matchable 
-** phrases in the expression (all phrases except those directly or 
-** indirectly descended from the right-hand-side of a NOT operator). If 
-** pnToken is not NULL, then it is set to the number of tokens in all
-** matchable phrases of the expression.
+** A coordinate can be either a floating point number or a integer.  All
+** coordinates within a single R-Tree are always of the same time.
 */
-static int fts3ExprLoadDoclists(
-  Fts3Cursor *pCsr,               /* Fts3 cursor for current query */
-  int *pnPhrase,                  /* OUT: Number of phrases in query */
-  int *pnToken                    /* OUT: Number of tokens in query */
-){
-  int rc;                         /* Return Code */
-  LoadDoclistCtx sCtx = {0,0,0};  /* Context for fts3ExprIterate() */
-  sCtx.pCsr = pCsr;
-  rc = fts3ExprIterate(pCsr->pExpr, fts3ExprLoadDoclistsCb, (void *)&sCtx);
-  if( pnPhrase ) *pnPhrase = sCtx.nPhrase;
-  if( pnToken ) *pnToken = sCtx.nToken;
-  return rc;
-}
-
-static int fts3ExprPhraseCountCb(Fts3Expr *pExpr, int iPhrase, void *ctx){
-  (*(int *)ctx)++;
-  UNUSED_PARAMETER(pExpr);
-  UNUSED_PARAMETER(iPhrase);
-  return SQLITE_OK;
-}
-static int fts3ExprPhraseCount(Fts3Expr *pExpr){
-  int nPhrase = 0;
-  (void)fts3ExprIterate(pExpr, fts3ExprPhraseCountCb, (void *)&nPhrase);
-  return nPhrase;
-}
+union RtreeCoord {
+  RtreeValue f;      /* Floating point value */
+  int i;             /* Integer value */
+  u32 u;             /* Unsigned for byte-order conversions */
+};
 
 /*
-** Advance the position list iterator specified by the first two 
-** arguments so that it points to the first element with a value greater
-** than or equal to parameter iNext.
+** The argument is an RtreeCoord. Return the value stored within the RtreeCoord
+** formatted as a RtreeDValue (double or int64). This macro assumes that local
+** variable pRtree points to the Rtree structure associated with the
+** RtreeCoord.
 */
-static void fts3SnippetAdvance(char **ppIter, int *piIter, int iNext){
-  char *pIter = *ppIter;
-  if( pIter ){
-    int iIter = *piIter;
-
-    while( iIter<iNext ){
-      if( 0==(*pIter & 0xFE) ){
-        iIter = -1;
-        pIter = 0;
-        break;
-      }
-      fts3GetDeltaPosition(&pIter, &iIter);
-    }
-
-    *piIter = iIter;
-    *ppIter = pIter;
-  }
-}
+#ifdef SQLITE_RTREE_INT_ONLY
+# define DCOORD(coord) ((RtreeDValue)coord.i)
+#else
+# define DCOORD(coord) (                           \
+    (pRtree->eCoordType==RTREE_COORD_REAL32) ?      \
+      ((double)coord.f) :                           \
+      ((double)coord.i)                             \
+  )
+#endif
 
 /*
-** Advance the snippet iterator to the next candidate snippet.
+** A search constraint.
 */
-static int fts3SnippetNextCandidate(SnippetIter *pIter){
-  int i;                          /* Loop counter */
-
-  if( pIter->iCurrent<0 ){
-    /* The SnippetIter object has just been initialized. The first snippet
-    ** candidate always starts at offset 0 (even if this candidate has a
-    ** score of 0.0).
-    */
-    pIter->iCurrent = 0;
-
-    /* Advance the 'head' iterator of each phrase to the first offset that
-    ** is greater than or equal to (iNext+nSnippet).
-    */
-    for(i=0; i<pIter->nPhrase; i++){
-      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
-      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, pIter->nSnippet);
-    }
-  }else{
-    int iStart;
-    int iEnd = 0x7FFFFFFF;
-
-    for(i=0; i<pIter->nPhrase; i++){
-      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
-      if( pPhrase->pHead && pPhrase->iHead<iEnd ){
-        iEnd = pPhrase->iHead;
-      }
-    }
-    if( iEnd==0x7FFFFFFF ){
-      return 1;
-    }
+struct RtreeConstraint {
+  int iCoord;                     /* Index of constrained coordinate */
+  int op;                         /* Constraining operation */
+  union {
+    RtreeDValue rValue;             /* Constraint value. */
+    int (*xGeom)(sqlite3_rtree_geometry*,int,RtreeDValue*,int*);
+    int (*xQueryFunc)(sqlite3_rtree_query_info*);
+  } u;
+  sqlite3_rtree_query_info *pInfo;  /* xGeom and xQueryFunc argument */
+};
 
-    pIter->iCurrent = iStart = iEnd - pIter->nSnippet + 1;
-    for(i=0; i<pIter->nPhrase; i++){
-      SnippetPhrase *pPhrase = &pIter->aPhrase[i];
-      fts3SnippetAdvance(&pPhrase->pHead, &pPhrase->iHead, iEnd+1);
-      fts3SnippetAdvance(&pPhrase->pTail, &pPhrase->iTail, iStart);
-    }
-  }
+/* Possible values for RtreeConstraint.op */
+#define RTREE_EQ    0x41  /* A */
+#define RTREE_LE    0x42  /* B */
+#define RTREE_LT    0x43  /* C */
+#define RTREE_GE    0x44  /* D */
+#define RTREE_GT    0x45  /* E */
+#define RTREE_MATCH 0x46  /* F: Old-style sqlite3_rtree_geometry_callback() */
+#define RTREE_QUERY 0x47  /* G: New-style sqlite3_rtree_query_callback() */
 
-  return 0;
-}
 
-/*
-** Retrieve information about the current candidate snippet of snippet 
-** iterator pIter.
+/* 
+** An rtree structure node.
 */
-static void fts3SnippetDetails(
-  SnippetIter *pIter,             /* Snippet iterator */
-  u64 mCovered,                   /* Bitmask of phrases already covered */
-  int *piToken,                   /* OUT: First token of proposed snippet */
-  int *piScore,                   /* OUT: "Score" for this snippet */
-  u64 *pmCover,                   /* OUT: Bitmask of phrases covered */
-  u64 *pmHighlight                /* OUT: Bitmask of terms to highlight */
-){
-  int iStart = pIter->iCurrent;   /* First token of snippet */
-  int iScore = 0;                 /* Score of this snippet */
-  int i;                          /* Loop counter */
-  u64 mCover = 0;                 /* Mask of phrases covered by this snippet */
-  u64 mHighlight = 0;             /* Mask of tokens to highlight in snippet */
-
-  for(i=0; i<pIter->nPhrase; i++){
-    SnippetPhrase *pPhrase = &pIter->aPhrase[i];
-    if( pPhrase->pTail ){
-      char *pCsr = pPhrase->pTail;
-      int iCsr = pPhrase->iTail;
-
-      while( iCsr<(iStart+pIter->nSnippet) ){
-        int j;
-        u64 mPhrase = (u64)1 << i;
-        u64 mPos = (u64)1 << (iCsr - iStart);
-        assert( iCsr>=iStart );
-        if( (mCover|mCovered)&mPhrase ){
-          iScore++;
-        }else{
-          iScore += 1000;
-        }
-        mCover |= mPhrase;
-
-        for(j=0; j<pPhrase->nToken; j++){
-          mHighlight |= (mPos>>j);
-        }
-
-        if( 0==(*pCsr & 0x0FE) ) break;
-        fts3GetDeltaPosition(&pCsr, &iCsr);
-      }
-    }
-  }
+struct RtreeNode {
+  RtreeNode *pParent;         /* Parent node */
+  i64 iNode;                  /* The node number */
+  int nRef;                   /* Number of references to this node */
+  int isDirty;                /* True if the node needs to be written to disk */
+  u8 *zData;                  /* Content of the node, as should be on disk */
+  RtreeNode *pNext;           /* Next node in this hash collision chain */
+};
 
-  /* Set the output variables before returning. */
-  *piToken = iStart;
-  *piScore = iScore;
-  *pmCover = mCover;
-  *pmHighlight = mHighlight;
-}
+/* Return the number of cells in a node  */
+#define NCELL(pNode) readInt16(&(pNode)->zData[2])
 
-/*
-** This function is an fts3ExprIterate() callback used by fts3BestSnippet().
-** Each invocation populates an element of the SnippetIter.aPhrase[] array.
+/* 
+** A single cell from a node, deserialized
 */
-static int fts3SnippetFindPositions(Fts3Expr *pExpr, int iPhrase, void *ctx){
-  SnippetIter *p = (SnippetIter *)ctx;
-  SnippetPhrase *pPhrase = &p->aPhrase[iPhrase];
-  char *pCsr;
-  int rc;
-
-  pPhrase->nToken = pExpr->pPhrase->nToken;
-  rc = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iCol, &pCsr);
-  assert( rc==SQLITE_OK || pCsr==0 );
-  if( pCsr ){
-    int iFirst = 0;
-    pPhrase->pList = pCsr;
-    fts3GetDeltaPosition(&pCsr, &iFirst);
-    assert( iFirst>=0 );
-    pPhrase->pHead = pCsr;
-    pPhrase->pTail = pCsr;
-    pPhrase->iHead = iFirst;
-    pPhrase->iTail = iFirst;
-  }else{
-    assert( rc!=SQLITE_OK || (
-       pPhrase->pList==0 && pPhrase->pHead==0 && pPhrase->pTail==0 
-    ));
-  }
+struct RtreeCell {
+  i64 iRowid;                                 /* Node or entry ID */
+  RtreeCoord aCoord[RTREE_MAX_DIMENSIONS*2];  /* Bounding box coordinates */
+};
 
-  return rc;
-}
 
 /*
-** Select the fragment of text consisting of nFragment contiguous tokens 
-** from column iCol that represent the "best" snippet. The best snippet
-** is the snippet with the highest score, where scores are calculated
-** by adding:
-**
-**   (a) +1 point for each occurrence of a matchable phrase in the snippet.
-**
-**   (b) +1000 points for the first occurrence of each matchable phrase in 
-**       the snippet for which the corresponding mCovered bit is not set.
+** This object becomes the sqlite3_user_data() for the SQL functions
+** that are created by sqlite3_rtree_geometry_callback() and
+** sqlite3_rtree_query_callback() and which appear on the right of MATCH
+** operators in order to constrain a search.
 **
-** The selected snippet parameters are stored in structure *pFragment before
-** returning. The score of the selected snippet is stored in *piScore
-** before returning.
+** xGeom and xQueryFunc are the callback functions.  Exactly one of 
+** xGeom and xQueryFunc fields is non-NULL, depending on whether the
+** SQL function was created using sqlite3_rtree_geometry_callback() or
+** sqlite3_rtree_query_callback().
+** 
+** This object is deleted automatically by the destructor mechanism in
+** sqlite3_create_function_v2().
 */
-static int fts3BestSnippet(
-  int nSnippet,                   /* Desired snippet length */
-  Fts3Cursor *pCsr,               /* Cursor to create snippet for */
-  int iCol,                       /* Index of column to create snippet from */
-  u64 mCovered,                   /* Mask of phrases already covered */
-  u64 *pmSeen,                    /* IN/OUT: Mask of phrases seen */
-  SnippetFragment *pFragment,     /* OUT: Best snippet found */
-  int *piScore                    /* OUT: Score of snippet pFragment */
-){
-  int rc;                         /* Return Code */
-  int nList;                      /* Number of phrases in expression */
-  SnippetIter sIter;              /* Iterates through snippet candidates */
-  int nByte;                      /* Number of bytes of space to allocate */
-  int iBestScore = -1;            /* Best snippet score found so far */
-  int i;                          /* Loop counter */
-
-  memset(&sIter, 0, sizeof(sIter));
-
-  /* Iterate through the phrases in the expression to count them. The same
-  ** callback makes sure the doclists are loaded for each phrase.
-  */
-  rc = fts3ExprLoadDoclists(pCsr, &nList, 0);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  /* Now that it is known how many phrases there are, allocate and zero
-  ** the required space using malloc().
-  */
-  nByte = sizeof(SnippetPhrase) * nList;
-  sIter.aPhrase = (SnippetPhrase *)sqlite3_malloc(nByte);
-  if( !sIter.aPhrase ){
-    return SQLITE_NOMEM;
-  }
-  memset(sIter.aPhrase, 0, nByte);
+struct RtreeGeomCallback {
+  int (*xGeom)(sqlite3_rtree_geometry*, int, RtreeDValue*, int*);
+  int (*xQueryFunc)(sqlite3_rtree_query_info*);
+  void (*xDestructor)(void*);
+  void *pContext;
+};
 
-  /* Initialize the contents of the SnippetIter object. Then iterate through
-  ** the set of phrases in the expression to populate the aPhrase[] array.
-  */
-  sIter.pCsr = pCsr;
-  sIter.iCol = iCol;
-  sIter.nSnippet = nSnippet;
-  sIter.nPhrase = nList;
-  sIter.iCurrent = -1;
-  rc = fts3ExprIterate(pCsr->pExpr, fts3SnippetFindPositions, (void *)&sIter);
-  if( rc==SQLITE_OK ){
 
-    /* Set the *pmSeen output variable. */
-    for(i=0; i<nList; i++){
-      if( sIter.aPhrase[i].pHead ){
-        *pmSeen |= (u64)1 << i;
-      }
-    }
+/*
+** Value for the first field of every RtreeMatchArg object. The MATCH
+** operator tests that the first field of a blob operand matches this
+** value to avoid operating on invalid blobs (which could cause a segfault).
+*/
+#define RTREE_GEOMETRY_MAGIC 0x891245AB
 
-    /* Loop through all candidate snippets. Store the best snippet in 
-     ** *pFragment. Store its associated 'score' in iBestScore.
-     */
-    pFragment->iCol = iCol;
-    while( !fts3SnippetNextCandidate(&sIter) ){
-      int iPos;
-      int iScore;
-      u64 mCover;
-      u64 mHighlite;
-      fts3SnippetDetails(&sIter, mCovered, &iPos, &iScore, &mCover,&mHighlite);
-      assert( iScore>=0 );
-      if( iScore>iBestScore ){
-        pFragment->iPos = iPos;
-        pFragment->hlmask = mHighlite;
-        pFragment->covered = mCover;
-        iBestScore = iScore;
-      }
-    }
+/*
+** An instance of this structure (in the form of a BLOB) is returned by
+** the SQL functions that sqlite3_rtree_geometry_callback() and
+** sqlite3_rtree_query_callback() create, and is read as the right-hand
+** operand to the MATCH operator of an R-Tree.
+*/
+struct RtreeMatchArg {
+  u32 magic;                  /* Always RTREE_GEOMETRY_MAGIC */
+  RtreeGeomCallback cb;       /* Info about the callback functions */
+  int nParam;                 /* Number of parameters to the SQL function */
+  sqlite3_value **apSqlParam; /* Original SQL parameter values */
+  RtreeDValue aParam[1];      /* Values for parameters to the SQL function */
+};
 
-    *piScore = iBestScore;
-  }
-  sqlite3_free(sIter.aPhrase);
-  return rc;
-}
+#ifndef MAX
+# define MAX(x,y) ((x) < (y) ? (y) : (x))
+#endif
+#ifndef MIN
+# define MIN(x,y) ((x) > (y) ? (y) : (x))
+#endif
 
+/*
+** Functions to deserialize a 16 bit integer, 32 bit real number and
+** 64 bit integer. The deserialized value is returned.
+*/
+static int readInt16(u8 *p){
+  return (p[0]<<8) + p[1];
+}
+static void readCoord(u8 *p, RtreeCoord *pCoord){
+  pCoord->u = (
+    (((u32)p[0]) << 24) + 
+    (((u32)p[1]) << 16) + 
+    (((u32)p[2]) <<  8) + 
+    (((u32)p[3]) <<  0)
+  );
+}
+static i64 readInt64(u8 *p){
+  return (
+    (((i64)p[0]) << 56) + 
+    (((i64)p[1]) << 48) + 
+    (((i64)p[2]) << 40) + 
+    (((i64)p[3]) << 32) + 
+    (((i64)p[4]) << 24) + 
+    (((i64)p[5]) << 16) + 
+    (((i64)p[6]) <<  8) + 
+    (((i64)p[7]) <<  0)
+  );
+}
 
 /*
-** Append a string to the string-buffer passed as the first argument.
-**
-** If nAppend is negative, then the length of the string zAppend is
-** determined using strlen().
+** Functions to serialize a 16 bit integer, 32 bit real number and
+** 64 bit integer. The value returned is the number of bytes written
+** to the argument buffer (always 2, 4 and 8 respectively).
 */
-static int fts3StringAppend(
-  StrBuffer *pStr,                /* Buffer to append to */
-  const char *zAppend,            /* Pointer to data to append to buffer */
-  int nAppend                     /* Size of zAppend in bytes (or -1) */
-){
-  if( nAppend<0 ){
-    nAppend = (int)strlen(zAppend);
-  }
+static int writeInt16(u8 *p, int i){
+  p[0] = (i>> 8)&0xFF;
+  p[1] = (i>> 0)&0xFF;
+  return 2;
+}
+static int writeCoord(u8 *p, RtreeCoord *pCoord){
+  u32 i;
+  assert( sizeof(RtreeCoord)==4 );
+  assert( sizeof(u32)==4 );
+  i = pCoord->u;
+  p[0] = (i>>24)&0xFF;
+  p[1] = (i>>16)&0xFF;
+  p[2] = (i>> 8)&0xFF;
+  p[3] = (i>> 0)&0xFF;
+  return 4;
+}
+static int writeInt64(u8 *p, i64 i){
+  p[0] = (i>>56)&0xFF;
+  p[1] = (i>>48)&0xFF;
+  p[2] = (i>>40)&0xFF;
+  p[3] = (i>>32)&0xFF;
+  p[4] = (i>>24)&0xFF;
+  p[5] = (i>>16)&0xFF;
+  p[6] = (i>> 8)&0xFF;
+  p[7] = (i>> 0)&0xFF;
+  return 8;
+}
 
-  /* If there is insufficient space allocated at StrBuffer.z, use realloc()
-  ** to grow the buffer until so that it is big enough to accomadate the
-  ** appended data.
-  */
-  if( pStr->n+nAppend+1>=pStr->nAlloc ){
-    int nAlloc = pStr->nAlloc+nAppend+100;
-    char *zNew = sqlite3_realloc(pStr->z, nAlloc);
-    if( !zNew ){
-      return SQLITE_NOMEM;
-    }
-    pStr->z = zNew;
-    pStr->nAlloc = nAlloc;
+/*
+** Increment the reference count of node p.
+*/
+static void nodeReference(RtreeNode *p){
+  if( p ){
+    p->nRef++;
   }
-  assert( pStr->z!=0 && (pStr->nAlloc >= pStr->n+nAppend+1) );
-
-  /* Append the data to the string buffer. */
-  memcpy(&pStr->z[pStr->n], zAppend, nAppend);
-  pStr->n += nAppend;
-  pStr->z[pStr->n] = '\0';
-
-  return SQLITE_OK;
 }
 
 /*
-** The fts3BestSnippet() function often selects snippets that end with a
-** query term. That is, the final term of the snippet is always a term
-** that requires highlighting. For example, if 'X' is a highlighted term
-** and '.' is a non-highlighted term, BestSnippet() may select:
-**
-**     ........X.....X
-**
-** This function "shifts" the beginning of the snippet forward in the 
-** document so that there are approximately the same number of 
-** non-highlighted terms to the right of the final highlighted term as there
-** are to the left of the first highlighted term. For example, to this:
-**
-**     ....X.....X....
-**
-** This is done as part of extracting the snippet text, not when selecting
-** the snippet. Snippet selection is done based on doclists only, so there
-** is no way for fts3BestSnippet() to know whether or not the document 
-** actually contains terms that follow the final highlighted term. 
+** Clear the content of node p (set all bytes to 0x00).
 */
-static int fts3SnippetShift(
-  Fts3Table *pTab,                /* FTS3 table snippet comes from */
-  int iLangid,                    /* Language id to use in tokenizing */
-  int nSnippet,                   /* Number of tokens desired for snippet */
-  const char *zDoc,               /* Document text to extract snippet from */
-  int nDoc,                       /* Size of buffer zDoc in bytes */
-  int *piPos,                     /* IN/OUT: First token of snippet */
-  u64 *pHlmask                    /* IN/OUT: Mask of tokens to highlight */
-){
-  u64 hlmask = *pHlmask;          /* Local copy of initial highlight-mask */
+static void nodeZero(Rtree *pRtree, RtreeNode *p){
+  memset(&p->zData[2], 0, pRtree->iNodeSize-2);
+  p->isDirty = 1;
+}
 
-  if( hlmask ){
-    int nLeft;                    /* Tokens to the left of first highlight */
-    int nRight;                   /* Tokens to the right of last highlight */
-    int nDesired;                 /* Ideal number of tokens to shift forward */
+/*
+** Given a node number iNode, return the corresponding key to use
+** in the Rtree.aHash table.
+*/
+static int nodeHash(i64 iNode){
+  return iNode % HASHSIZE;
+}
 
-    for(nLeft=0; !(hlmask & ((u64)1 << nLeft)); nLeft++);
-    for(nRight=0; !(hlmask & ((u64)1 << (nSnippet-1-nRight))); nRight++);
-    nDesired = (nLeft-nRight)/2;
+/*
+** Search the node hash table for node iNode. If found, return a pointer
+** to it. Otherwise, return 0.
+*/
+static RtreeNode *nodeHashLookup(Rtree *pRtree, i64 iNode){
+  RtreeNode *p;
+  for(p=pRtree->aHash[nodeHash(iNode)]; p && p->iNode!=iNode; p=p->pNext);
+  return p;
+}
 
-    /* Ideally, the start of the snippet should be pushed forward in the
-    ** document nDesired tokens. This block checks if there are actually
-    ** nDesired tokens to the right of the snippet. If so, *piPos and
-    ** *pHlMask are updated to shift the snippet nDesired tokens to the
-    ** right. Otherwise, the snippet is shifted by the number of tokens
-    ** available.
-    */
-    if( nDesired>0 ){
-      int nShift;                 /* Number of tokens to shift snippet by */
-      int iCurrent = 0;           /* Token counter */
-      int rc;                     /* Return Code */
-      sqlite3_tokenizer_module *pMod;
-      sqlite3_tokenizer_cursor *pC;
-      pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
+/*
+** Add node pNode to the node hash table.
+*/
+static void nodeHashInsert(Rtree *pRtree, RtreeNode *pNode){
+  int iHash;
+  assert( pNode->pNext==0 );
+  iHash = nodeHash(pNode->iNode);
+  pNode->pNext = pRtree->aHash[iHash];
+  pRtree->aHash[iHash] = pNode;
+}
 
-      /* Open a cursor on zDoc/nDoc. Check if there are (nSnippet+nDesired)
-      ** or more tokens in zDoc/nDoc.
-      */
-      rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, iLangid, zDoc, nDoc, &pC);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-      while( rc==SQLITE_OK && iCurrent<(nSnippet+nDesired) ){
-        const char *ZDUMMY; int DUMMY1 = 0, DUMMY2 = 0, DUMMY3 = 0;
-        rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &DUMMY2, &DUMMY3, &iCurrent);
-      }
-      pMod->xClose(pC);
-      if( rc!=SQLITE_OK && rc!=SQLITE_DONE ){ return rc; }
+/*
+** Remove node pNode from the node hash table.
+*/
+static void nodeHashDelete(Rtree *pRtree, RtreeNode *pNode){
+  RtreeNode **pp;
+  if( pNode->iNode!=0 ){
+    pp = &pRtree->aHash[nodeHash(pNode->iNode)];
+    for( ; (*pp)!=pNode; pp = &(*pp)->pNext){ assert(*pp); }
+    *pp = pNode->pNext;
+    pNode->pNext = 0;
+  }
+}
 
-      nShift = (rc==SQLITE_DONE)+iCurrent-nSnippet;
-      assert( nShift<=nDesired );
-      if( nShift>0 ){
-        *piPos += nShift;
-        *pHlmask = hlmask >> nShift;
-      }
-    }
+/*
+** Allocate and return new r-tree node. Initially, (RtreeNode.iNode==0),
+** indicating that node has not yet been assigned a node number. It is
+** assigned a node number when nodeWrite() is called to write the
+** node contents out to the database.
+*/
+static RtreeNode *nodeNew(Rtree *pRtree, RtreeNode *pParent){
+  RtreeNode *pNode;
+  pNode = (RtreeNode *)sqlite3_malloc(sizeof(RtreeNode) + pRtree->iNodeSize);
+  if( pNode ){
+    memset(pNode, 0, sizeof(RtreeNode) + pRtree->iNodeSize);
+    pNode->zData = (u8 *)&pNode[1];
+    pNode->nRef = 1;
+    pNode->pParent = pParent;
+    pNode->isDirty = 1;
+    nodeReference(pParent);
   }
-  return SQLITE_OK;
+  return pNode;
 }
 
 /*
-** Extract the snippet text for fragment pFragment from cursor pCsr and
-** append it to string buffer pOut.
+** Obtain a reference to an r-tree node.
 */
-static int fts3SnippetText(
-  Fts3Cursor *pCsr,               /* FTS3 Cursor */
-  SnippetFragment *pFragment,     /* Snippet to extract */
-  int iFragment,                  /* Fragment number */
-  int isLast,                     /* True for final fragment in snippet */
-  int nSnippet,                   /* Number of tokens in extracted snippet */
-  const char *zOpen,              /* String inserted before highlighted term */
-  const char *zClose,             /* String inserted after highlighted term */
-  const char *zEllipsis,          /* String inserted between snippets */
-  StrBuffer *pOut                 /* Write output here */
+static int nodeAcquire(
+  Rtree *pRtree,             /* R-tree structure */
+  i64 iNode,                 /* Node number to load */
+  RtreeNode *pParent,        /* Either the parent node or NULL */
+  RtreeNode **ppNode         /* OUT: Acquired node */
 ){
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  int rc;                         /* Return code */
-  const char *zDoc;               /* Document text to extract snippet from */
-  int nDoc;                       /* Size of zDoc in bytes */
-  int iCurrent = 0;               /* Current token number of document */
-  int iEnd = 0;                   /* Byte offset of end of current token */
-  int isShiftDone = 0;            /* True after snippet is shifted */
-  int iPos = pFragment->iPos;     /* First token of snippet */
-  u64 hlmask = pFragment->hlmask; /* Highlight-mask for snippet */
-  int iCol = pFragment->iCol+1;   /* Query column to extract text from */
-  sqlite3_tokenizer_module *pMod; /* Tokenizer module methods object */
-  sqlite3_tokenizer_cursor *pC;   /* Tokenizer cursor open on zDoc/nDoc */
-  
-  zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol);
-  if( zDoc==0 ){
-    if( sqlite3_column_type(pCsr->pStmt, iCol)!=SQLITE_NULL ){
-      return SQLITE_NOMEM;
+  int rc;
+  int rc2 = SQLITE_OK;
+  RtreeNode *pNode;
+
+  /* Check if the requested node is already in the hash table. If so,
+  ** increase its reference count and return it.
+  */
+  if( (pNode = nodeHashLookup(pRtree, iNode)) ){
+    assert( !pParent || !pNode->pParent || pNode->pParent==pParent );
+    if( pParent && !pNode->pParent ){
+      nodeReference(pParent);
+      pNode->pParent = pParent;
     }
+    pNode->nRef++;
+    *ppNode = pNode;
     return SQLITE_OK;
   }
-  nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol);
-
-  /* Open a token cursor on the document. */
-  pMod = (sqlite3_tokenizer_module *)pTab->pTokenizer->pModule;
-  rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, pCsr->iLangid, zDoc,nDoc,&pC);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  while( rc==SQLITE_OK ){
-    const char *ZDUMMY;           /* Dummy argument used with tokenizer */
-    int DUMMY1 = -1;              /* Dummy argument used with tokenizer */
-    int iBegin = 0;               /* Offset in zDoc of start of token */
-    int iFin = 0;                 /* Offset in zDoc of end of token */
-    int isHighlight = 0;          /* True for highlighted terms */
 
-    /* Variable DUMMY1 is initialized to a negative value above. Elsewhere
-    ** in the FTS code the variable that the third argument to xNext points to
-    ** is initialized to zero before the first (*but not necessarily
-    ** subsequent*) call to xNext(). This is done for a particular application
-    ** that needs to know whether or not the tokenizer is being used for
-    ** snippet generation or for some other purpose.
-    **
-    ** Extreme care is required when writing code to depend on this
-    ** initialization. It is not a documented part of the tokenizer interface.
-    ** If a tokenizer is used directly by any code outside of FTS, this
-    ** convention might not be respected.  */
-    rc = pMod->xNext(pC, &ZDUMMY, &DUMMY1, &iBegin, &iFin, &iCurrent);
-    if( rc!=SQLITE_OK ){
-      if( rc==SQLITE_DONE ){
-        /* Special case - the last token of the snippet is also the last token
-        ** of the column. Append any punctuation that occurred between the end
-        ** of the previous token and the end of the document to the output. 
-        ** Then break out of the loop. */
-        rc = fts3StringAppend(pOut, &zDoc[iEnd], -1);
+  sqlite3_bind_int64(pRtree->pReadNode, 1, iNode);
+  rc = sqlite3_step(pRtree->pReadNode);
+  if( rc==SQLITE_ROW ){
+    const u8 *zBlob = sqlite3_column_blob(pRtree->pReadNode, 0);
+    if( pRtree->iNodeSize==sqlite3_column_bytes(pRtree->pReadNode, 0) ){
+      pNode = (RtreeNode *)sqlite3_malloc(sizeof(RtreeNode)+pRtree->iNodeSize);
+      if( !pNode ){
+        rc2 = SQLITE_NOMEM;
+      }else{
+        pNode->pParent = pParent;
+        pNode->zData = (u8 *)&pNode[1];
+        pNode->nRef = 1;
+        pNode->iNode = iNode;
+        pNode->isDirty = 0;
+        pNode->pNext = 0;
+        memcpy(pNode->zData, zBlob, pRtree->iNodeSize);
+        nodeReference(pParent);
       }
-      break;
     }
-    if( iCurrent<iPos ){ continue; }
-
-    if( !isShiftDone ){
-      int n = nDoc - iBegin;
-      rc = fts3SnippetShift(
-          pTab, pCsr->iLangid, nSnippet, &zDoc[iBegin], n, &iPos, &hlmask
-      );
-      isShiftDone = 1;
+  }
+  rc = sqlite3_reset(pRtree->pReadNode);
+  if( rc==SQLITE_OK ) rc = rc2;
 
-      /* Now that the shift has been done, check if the initial "..." are
-      ** required. They are required if (a) this is not the first fragment,
-      ** or (b) this fragment does not begin at position 0 of its column. 
-      */
-      if( rc==SQLITE_OK ){
-        if( iPos>0 || iFragment>0 ){
-          rc = fts3StringAppend(pOut, zEllipsis, -1);
-        }else if( iBegin ){
-          rc = fts3StringAppend(pOut, zDoc, iBegin);
-        }
-      }
-      if( rc!=SQLITE_OK || iCurrent<iPos ) continue;
+  /* If the root node was just loaded, set pRtree->iDepth to the height
+  ** of the r-tree structure. A height of zero means all data is stored on
+  ** the root node. A height of one means the children of the root node
+  ** are the leaves, and so on. If the depth as specified on the root node
+  ** is greater than RTREE_MAX_DEPTH, the r-tree structure must be corrupt.
+  */
+  if( pNode && iNode==1 ){
+    pRtree->iDepth = readInt16(pNode->zData);
+    if( pRtree->iDepth>RTREE_MAX_DEPTH ){
+      rc = SQLITE_CORRUPT_VTAB;
     }
+  }
 
-    if( iCurrent>=(iPos+nSnippet) ){
-      if( isLast ){
-        rc = fts3StringAppend(pOut, zEllipsis, -1);
-      }
-      break;
+  /* If no error has occurred so far, check if the "number of entries"
+  ** field on the node is too large. If so, set the return code to 
+  ** SQLITE_CORRUPT_VTAB.
+  */
+  if( pNode && rc==SQLITE_OK ){
+    if( NCELL(pNode)>((pRtree->iNodeSize-4)/pRtree->nBytesPerCell) ){
+      rc = SQLITE_CORRUPT_VTAB;
     }
+  }
 
-    /* Set isHighlight to true if this term should be highlighted. */
-    isHighlight = (hlmask & ((u64)1 << (iCurrent-iPos)))!=0;
-
-    if( iCurrent>iPos ) rc = fts3StringAppend(pOut, &zDoc[iEnd], iBegin-iEnd);
-    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zOpen, -1);
-    if( rc==SQLITE_OK ) rc = fts3StringAppend(pOut, &zDoc[iBegin], iFin-iBegin);
-    if( rc==SQLITE_OK && isHighlight ) rc = fts3StringAppend(pOut, zClose, -1);
-
-    iEnd = iFin;
+  if( rc==SQLITE_OK ){
+    if( pNode!=0 ){
+      nodeHashInsert(pRtree, pNode);
+    }else{
+      rc = SQLITE_CORRUPT_VTAB;
+    }
+    *ppNode = pNode;
+  }else{
+    sqlite3_free(pNode);
+    *ppNode = 0;
   }
 
-  pMod->xClose(pC);
   return rc;
 }
 
-
 /*
-** This function is used to count the entries in a column-list (a 
-** delta-encoded list of term offsets within a single column of a single 
-** row). When this function is called, *ppCollist should point to the
-** beginning of the first varint in the column-list (the varint that
-** contains the position of the first matching term in the column data).
-** Before returning, *ppCollist is set to point to the first byte after
-** the last varint in the column-list (either the 0x00 signifying the end
-** of the position-list, or the 0x01 that precedes the column number of
-** the next column in the position-list).
-**
-** The number of elements in the column-list is returned.
+** Overwrite cell iCell of node pNode with the contents of pCell.
 */
-static int fts3ColumnlistCount(char **ppCollist){
-  char *pEnd = *ppCollist;
-  char c = 0;
-  int nEntry = 0;
-
-  /* A column-list is terminated by either a 0x01 or 0x00. */
-  while( 0xFE & (*pEnd | c) ){
-    c = *pEnd++ & 0x80;
-    if( !c ) nEntry++;
+static void nodeOverwriteCell(
+  Rtree *pRtree,             /* The overall R-Tree */
+  RtreeNode *pNode,          /* The node into which the cell is to be written */
+  RtreeCell *pCell,          /* The cell to write */
+  int iCell                  /* Index into pNode into which pCell is written */
+){
+  int ii;
+  u8 *p = &pNode->zData[4 + pRtree->nBytesPerCell*iCell];
+  p += writeInt64(p, pCell->iRowid);
+  for(ii=0; ii<(pRtree->nDim*2); ii++){
+    p += writeCoord(p, &pCell->aCoord[ii]);
   }
+  pNode->isDirty = 1;
+}
 
-  *ppCollist = pEnd;
-  return nEntry;
+/*
+** Remove the cell with index iCell from node pNode.
+*/
+static void nodeDeleteCell(Rtree *pRtree, RtreeNode *pNode, int iCell){
+  u8 *pDst = &pNode->zData[4 + pRtree->nBytesPerCell*iCell];
+  u8 *pSrc = &pDst[pRtree->nBytesPerCell];
+  int nByte = (NCELL(pNode) - iCell - 1) * pRtree->nBytesPerCell;
+  memmove(pDst, pSrc, nByte);
+  writeInt16(&pNode->zData[2], NCELL(pNode)-1);
+  pNode->isDirty = 1;
 }
 
 /*
-** fts3ExprIterate() callback used to collect the "global" matchinfo stats
-** for a single query. 
-**
-** fts3ExprIterate() callback to load the 'global' elements of a
-** FTS3_MATCHINFO_HITS matchinfo array. The global stats are those elements 
-** of the matchinfo array that are constant for all rows returned by the 
-** current query.
-**
-** Argument pCtx is actually a pointer to a struct of type MatchInfo. This
-** function populates Matchinfo.aMatchinfo[] as follows:
-**
-**   for(iCol=0; iCol<nCol; iCol++){
-**     aMatchinfo[3*iPhrase*nCol + 3*iCol + 1] = X;
-**     aMatchinfo[3*iPhrase*nCol + 3*iCol + 2] = Y;
-**   }
-**
-** where X is the number of matches for phrase iPhrase is column iCol of all
-** rows of the table. Y is the number of rows for which column iCol contains
-** at least one instance of phrase iPhrase.
+** Insert the contents of cell pCell into node pNode. If the insert
+** is successful, return SQLITE_OK.
 **
-** If the phrase pExpr consists entirely of deferred tokens, then all X and
-** Y values are set to nDoc, where nDoc is the number of documents in the 
-** file system. This is done because the full-text index doclist is required
-** to calculate these values properly, and the full-text index doclist is
-** not available for deferred tokens.
+** If there is not enough free space in pNode, return SQLITE_FULL.
 */
-static int fts3ExprGlobalHitsCb(
-  Fts3Expr *pExpr,                /* Phrase expression node */
-  int iPhrase,                    /* Phrase number (numbered from zero) */
-  void *pCtx                      /* Pointer to MatchInfo structure */
+static int nodeInsertCell(
+  Rtree *pRtree,                /* The overall R-Tree */
+  RtreeNode *pNode,             /* Write new cell into this node */
+  RtreeCell *pCell              /* The cell to be inserted */
 ){
-  MatchInfo *p = (MatchInfo *)pCtx;
-  return sqlite3Fts3EvalPhraseStats(
-      p->pCursor, pExpr, &p->aMatchinfo[3*iPhrase*p->nCol]
-  );
+  int nCell;                    /* Current number of cells in pNode */
+  int nMaxCell;                 /* Maximum number of cells for pNode */
+
+  nMaxCell = (pRtree->iNodeSize-4)/pRtree->nBytesPerCell;
+  nCell = NCELL(pNode);
+
+  assert( nCell<=nMaxCell );
+  if( nCell<nMaxCell ){
+    nodeOverwriteCell(pRtree, pNode, pCell, nCell);
+    writeInt16(&pNode->zData[2], nCell+1);
+    pNode->isDirty = 1;
+  }
+
+  return (nCell==nMaxCell);
 }
 
 /*
-** fts3ExprIterate() callback used to collect the "local" part of the
-** FTS3_MATCHINFO_HITS array. The local stats are those elements of the 
-** array that are different for each row returned by the query.
+** If the node is dirty, write it out to the database.
 */
-static int fts3ExprLocalHitsCb(
-  Fts3Expr *pExpr,                /* Phrase expression node */
-  int iPhrase,                    /* Phrase number */
-  void *pCtx                      /* Pointer to MatchInfo structure */
-){
+static int nodeWrite(Rtree *pRtree, RtreeNode *pNode){
   int rc = SQLITE_OK;
-  MatchInfo *p = (MatchInfo *)pCtx;
-  int iStart = iPhrase * p->nCol * 3;
-  int i;
-
-  for(i=0; i<p->nCol && rc==SQLITE_OK; i++){
-    char *pCsr;
-    rc = sqlite3Fts3EvalPhrasePoslist(p->pCursor, pExpr, i, &pCsr);
-    if( pCsr ){
-      p->aMatchinfo[iStart+i*3] = fts3ColumnlistCount(&pCsr);
+  if( pNode->isDirty ){
+    sqlite3_stmt *p = pRtree->pWriteNode;
+    if( pNode->iNode ){
+      sqlite3_bind_int64(p, 1, pNode->iNode);
     }else{
-      p->aMatchinfo[iStart+i*3] = 0;
+      sqlite3_bind_null(p, 1);
+    }
+    sqlite3_bind_blob(p, 2, pNode->zData, pRtree->iNodeSize, SQLITE_STATIC);
+    sqlite3_step(p);
+    pNode->isDirty = 0;
+    rc = sqlite3_reset(p);
+    if( pNode->iNode==0 && rc==SQLITE_OK ){
+      pNode->iNode = sqlite3_last_insert_rowid(pRtree->db);
+      nodeHashInsert(pRtree, pNode);
     }
   }
-
   return rc;
 }
 
 /*
-** fts3ExprIterate() callback used to gather information for the matchinfo
-** directive 'y'.
+** Release a reference to a node. If the node is dirty and the reference
+** count drops to zero, the node data is written to the database.
 */
-static int fts3ExprLHitsCb(
-  Fts3Expr *pExpr,                /* Phrase expression node */
-  int iPhrase,                    /* Phrase number */
-  void *pCtx                      /* Pointer to MatchInfo structure */
-){
-  MatchInfo *p = (MatchInfo *)pCtx;
-  Fts3Table *pTab = (Fts3Table *)p->pCursor->base.pVtab;
+static int nodeRelease(Rtree *pRtree, RtreeNode *pNode){
   int rc = SQLITE_OK;
-  int iStart = iPhrase * p->nCol;
-  Fts3Expr *pEof;                 /* Ancestor node already at EOF */
-  
-  /* This must be a phrase */
-  assert( pExpr->pPhrase );
-
-  /* Initialize all output integers to zero. */
-  memset(&p->aMatchinfo[iStart], 0, sizeof(u32) * p->nCol);
-
-  /* Check if this or any parent node is at EOF. If so, then all output
-  ** values are zero.  */
-  for(pEof=pExpr; pEof && pEof->bEof==0; pEof=pEof->pParent);
-
-  if( pEof==0 && pExpr->iDocid==p->pCursor->iPrevId ){
-    Fts3Phrase *pPhrase = pExpr->pPhrase;
-    char *pIter = pPhrase->doclist.pList;
-    int iCol = 0;
-
-    while( 1 ){
-      int nHit = fts3ColumnlistCount(&pIter);
-      if( (pPhrase->iColumn>=pTab->nColumn || pPhrase->iColumn==iCol) ){
-        p->aMatchinfo[iStart + iCol] = (u32)nHit;
+  if( pNode ){
+    assert( pNode->nRef>0 );
+    pNode->nRef--;
+    if( pNode->nRef==0 ){
+      if( pNode->iNode==1 ){
+        pRtree->iDepth = -1;
       }
-      assert( *pIter==0x00 || *pIter==0x01 );
-      if( *pIter!=0x01 ) break;
-      pIter++;
-      pIter += fts3GetVarint32(pIter, &iCol);
+      if( pNode->pParent ){
+        rc = nodeRelease(pRtree, pNode->pParent);
+      }
+      if( rc==SQLITE_OK ){
+        rc = nodeWrite(pRtree, pNode);
+      }
+      nodeHashDelete(pRtree, pNode);
+      sqlite3_free(pNode);
     }
   }
-
   return rc;
 }
 
-static int fts3MatchinfoCheck(
-  Fts3Table *pTab, 
-  char cArg,
-  char **pzErr
+/*
+** Return the 64-bit integer value associated with cell iCell of
+** node pNode. If pNode is a leaf node, this is a rowid. If it is
+** an internal node, then the 64-bit integer is a child page number.
+*/
+static i64 nodeGetRowid(
+  Rtree *pRtree,       /* The overall R-Tree */
+  RtreeNode *pNode,    /* The node from which to extract the ID */
+  int iCell            /* The cell index from which to extract the ID */
 ){
-  if( (cArg==FTS3_MATCHINFO_NPHRASE)
-   || (cArg==FTS3_MATCHINFO_NCOL)
-   || (cArg==FTS3_MATCHINFO_NDOC && pTab->bFts4)
-   || (cArg==FTS3_MATCHINFO_AVGLENGTH && pTab->bFts4)
-   || (cArg==FTS3_MATCHINFO_LENGTH && pTab->bHasDocsize)
-   || (cArg==FTS3_MATCHINFO_LCS)
-   || (cArg==FTS3_MATCHINFO_HITS)
-   || (cArg==FTS3_MATCHINFO_LHITS)
-  ){
-    return SQLITE_OK;
-  }
-  sqlite3Fts3ErrMsg(pzErr, "unrecognized matchinfo request: %c", cArg);
-  return SQLITE_ERROR;
+  assert( iCell<NCELL(pNode) );
+  return readInt64(&pNode->zData[4 + pRtree->nBytesPerCell*iCell]);
 }
 
-static int fts3MatchinfoSize(MatchInfo *pInfo, char cArg){
-  int nVal;                       /* Number of integers output by cArg */
-
-  switch( cArg ){
-    case FTS3_MATCHINFO_NDOC:
-    case FTS3_MATCHINFO_NPHRASE: 
-    case FTS3_MATCHINFO_NCOL: 
-      nVal = 1;
-      break;
+/*
+** Return coordinate iCoord from cell iCell in node pNode.
+*/
+static void nodeGetCoord(
+  Rtree *pRtree,               /* The overall R-Tree */
+  RtreeNode *pNode,            /* The node from which to extract a coordinate */
+  int iCell,                   /* The index of the cell within the node */
+  int iCoord,                  /* Which coordinate to extract */
+  RtreeCoord *pCoord           /* OUT: Space to write result to */
+){
+  readCoord(&pNode->zData[12 + pRtree->nBytesPerCell*iCell + 4*iCoord], pCoord);
+}
 
-    case FTS3_MATCHINFO_AVGLENGTH:
-    case FTS3_MATCHINFO_LENGTH:
-    case FTS3_MATCHINFO_LCS:
-      nVal = pInfo->nCol;
-      break;
+/*
+** Deserialize cell iCell of node pNode. Populate the structure pointed
+** to by pCell with the results.
+*/
+static void nodeGetCell(
+  Rtree *pRtree,               /* The overall R-Tree */
+  RtreeNode *pNode,            /* The node containing the cell to be read */
+  int iCell,                   /* Index of the cell within the node */
+  RtreeCell *pCell             /* OUT: Write the cell contents here */
+){
+  u8 *pData;
+  RtreeCoord *pCoord;
+  int ii;
+  pCell->iRowid = nodeGetRowid(pRtree, pNode, iCell);
+  pData = pNode->zData + (12 + pRtree->nBytesPerCell*iCell);
+  pCoord = pCell->aCoord;
+  for(ii=0; ii<pRtree->nDim*2; ii++){
+    readCoord(&pData[ii*4], &pCoord[ii]);
+  }
+}
 
-    case FTS3_MATCHINFO_LHITS:
-      nVal = pInfo->nCol * pInfo->nPhrase;
-      break;
 
-    default:
-      assert( cArg==FTS3_MATCHINFO_HITS );
-      nVal = pInfo->nCol * pInfo->nPhrase * 3;
-      break;
-  }
+/* Forward declaration for the function that does the work of
+** the virtual table module xCreate() and xConnect() methods.
+*/
+static int rtreeInit(
+  sqlite3 *, void *, int, const char *const*, sqlite3_vtab **, char **, int
+);
 
-  return nVal;
+/* 
+** Rtree virtual table module xCreate method.
+*/
+static int rtreeCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  return rtreeInit(db, pAux, argc, argv, ppVtab, pzErr, 1);
 }
 
-static int fts3MatchinfoSelectDoctotal(
-  Fts3Table *pTab,
-  sqlite3_stmt **ppStmt,
-  sqlite3_int64 *pnDoc,
-  const char **paLen
+/* 
+** Rtree virtual table module xConnect method.
+*/
+static int rtreeConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
 ){
-  sqlite3_stmt *pStmt;
-  const char *a;
-  sqlite3_int64 nDoc;
-
-  if( !*ppStmt ){
-    int rc = sqlite3Fts3SelectDoctotal(pTab, ppStmt);
-    if( rc!=SQLITE_OK ) return rc;
-  }
-  pStmt = *ppStmt;
-  assert( sqlite3_data_count(pStmt)==1 );
-
-  a = sqlite3_column_blob(pStmt, 0);
-  a += sqlite3Fts3GetVarint(a, &nDoc);
-  if( nDoc==0 ) return FTS_CORRUPT_VTAB;
-  *pnDoc = (u32)nDoc;
+  return rtreeInit(db, pAux, argc, argv, ppVtab, pzErr, 0);
+}
 
-  if( paLen ) *paLen = a;
-  return SQLITE_OK;
+/*
+** Increment the r-tree reference count.
+*/
+static void rtreeReference(Rtree *pRtree){
+  pRtree->nBusy++;
 }
 
 /*
-** An instance of the following structure is used to store state while 
-** iterating through a multi-column position-list corresponding to the
-** hits for a single phrase on a single row in order to calculate the
-** values for a matchinfo() FTS3_MATCHINFO_LCS request.
+** Decrement the r-tree reference count. When the reference count reaches
+** zero the structure is deleted.
 */
-typedef struct LcsIterator LcsIterator;
-struct LcsIterator {
-  Fts3Expr *pExpr;                /* Pointer to phrase expression */
-  int iPosOffset;                 /* Tokens count up to end of this phrase */
-  char *pRead;                    /* Cursor used to iterate through aDoclist */
-  int iPos;                       /* Current position */
-};
+static void rtreeRelease(Rtree *pRtree){
+  pRtree->nBusy--;
+  if( pRtree->nBusy==0 ){
+    sqlite3_finalize(pRtree->pReadNode);
+    sqlite3_finalize(pRtree->pWriteNode);
+    sqlite3_finalize(pRtree->pDeleteNode);
+    sqlite3_finalize(pRtree->pReadRowid);
+    sqlite3_finalize(pRtree->pWriteRowid);
+    sqlite3_finalize(pRtree->pDeleteRowid);
+    sqlite3_finalize(pRtree->pReadParent);
+    sqlite3_finalize(pRtree->pWriteParent);
+    sqlite3_finalize(pRtree->pDeleteParent);
+    sqlite3_free(pRtree);
+  }
+}
 
 /* 
-** If LcsIterator.iCol is set to the following value, the iterator has
-** finished iterating through all offsets for all columns.
+** Rtree virtual table module xDisconnect method.
 */
-#define LCS_ITERATOR_FINISHED 0x7FFFFFFF;
-
-static int fts3MatchinfoLcsCb(
-  Fts3Expr *pExpr,                /* Phrase expression node */
-  int iPhrase,                    /* Phrase number (numbered from zero) */
-  void *pCtx                      /* Pointer to MatchInfo structure */
-){
-  LcsIterator *aIter = (LcsIterator *)pCtx;
-  aIter[iPhrase].pExpr = pExpr;
+static int rtreeDisconnect(sqlite3_vtab *pVtab){
+  rtreeRelease((Rtree *)pVtab);
   return SQLITE_OK;
 }
 
-/*
-** Advance the iterator passed as an argument to the next position. Return
-** 1 if the iterator is at EOF or if it now points to the start of the
-** position list for the next column.
+/* 
+** Rtree virtual table module xDestroy method.
 */
-static int fts3LcsIteratorAdvance(LcsIterator *pIter){
-  char *pRead = pIter->pRead;
-  sqlite3_int64 iRead;
-  int rc = 0;
-
-  pRead += sqlite3Fts3GetVarint(pRead, &iRead);
-  if( iRead==0 || iRead==1 ){
-    pRead = 0;
-    rc = 1;
+static int rtreeDestroy(sqlite3_vtab *pVtab){
+  Rtree *pRtree = (Rtree *)pVtab;
+  int rc;
+  char *zCreate = sqlite3_mprintf(
+    "DROP TABLE '%q'.'%q_node';"
+    "DROP TABLE '%q'.'%q_rowid';"
+    "DROP TABLE '%q'.'%q_parent';",
+    pRtree->zDb, pRtree->zName, 
+    pRtree->zDb, pRtree->zName,
+    pRtree->zDb, pRtree->zName
+  );
+  if( !zCreate ){
+    rc = SQLITE_NOMEM;
   }else{
-    pIter->iPos += (int)(iRead-2);
+    rc = sqlite3_exec(pRtree->db, zCreate, 0, 0, 0);
+    sqlite3_free(zCreate);
+  }
+  if( rc==SQLITE_OK ){
+    rtreeRelease(pRtree);
   }
 
-  pIter->pRead = pRead;
   return rc;
 }
-  
-/*
-** This function implements the FTS3_MATCHINFO_LCS matchinfo() flag. 
-**
-** If the call is successful, the longest-common-substring lengths for each
-** column are written into the first nCol elements of the pInfo->aMatchinfo[] 
-** array before returning. SQLITE_OK is returned in this case.
-**
-** Otherwise, if an error occurs, an SQLite error code is returned and the
-** data written to the first nCol elements of pInfo->aMatchinfo[] is 
-** undefined.
-*/
-static int fts3MatchinfoLcs(Fts3Cursor *pCsr, MatchInfo *pInfo){
-  LcsIterator *aIter;
-  int i;
-  int iCol;
-  int nToken = 0;
 
-  /* Allocate and populate the array of LcsIterator objects. The array
-  ** contains one element for each matchable phrase in the query.
-  **/
-  aIter = sqlite3_malloc(sizeof(LcsIterator) * pCsr->nPhrase);
-  if( !aIter ) return SQLITE_NOMEM;
-  memset(aIter, 0, sizeof(LcsIterator) * pCsr->nPhrase);
-  (void)fts3ExprIterate(pCsr->pExpr, fts3MatchinfoLcsCb, (void*)aIter);
+/* 
+** Rtree virtual table module xOpen method.
+*/
+static int rtreeOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  RtreeCursor *pCsr;
 
-  for(i=0; i<pInfo->nPhrase; i++){
-    LcsIterator *pIter = &aIter[i];
-    nToken -= pIter->pExpr->pPhrase->nToken;
-    pIter->iPosOffset = nToken;
+  pCsr = (RtreeCursor *)sqlite3_malloc(sizeof(RtreeCursor));
+  if( pCsr ){
+    memset(pCsr, 0, sizeof(RtreeCursor));
+    pCsr->base.pVtab = pVTab;
+    rc = SQLITE_OK;
   }
+  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
 
-  for(iCol=0; iCol<pInfo->nCol; iCol++){
-    int nLcs = 0;                 /* LCS value for this column */
-    int nLive = 0;                /* Number of iterators in aIter not at EOF */
-
-    for(i=0; i<pInfo->nPhrase; i++){
-      int rc;
-      LcsIterator *pIt = &aIter[i];
-      rc = sqlite3Fts3EvalPhrasePoslist(pCsr, pIt->pExpr, iCol, &pIt->pRead);
-      if( rc!=SQLITE_OK ) return rc;
-      if( pIt->pRead ){
-        pIt->iPos = pIt->iPosOffset;
-        fts3LcsIteratorAdvance(&aIter[i]);
-        nLive++;
-      }
-    }
+  return rc;
+}
 
-    while( nLive>0 ){
-      LcsIterator *pAdv = 0;      /* The iterator to advance by one position */
-      int nThisLcs = 0;           /* LCS for the current iterator positions */
 
-      for(i=0; i<pInfo->nPhrase; i++){
-        LcsIterator *pIter = &aIter[i];
-        if( pIter->pRead==0 ){
-          /* This iterator is already at EOF for this column. */
-          nThisLcs = 0;
-        }else{
-          if( pAdv==0 || pIter->iPos<pAdv->iPos ){
-            pAdv = pIter;
-          }
-          if( nThisLcs==0 || pIter->iPos==pIter[-1].iPos ){
-            nThisLcs++;
-          }else{
-            nThisLcs = 1;
-          }
-          if( nThisLcs>nLcs ) nLcs = nThisLcs;
-        }
+/*
+** Free the RtreeCursor.aConstraint[] array and its contents.
+*/
+static void freeCursorConstraints(RtreeCursor *pCsr){
+  if( pCsr->aConstraint ){
+    int i;                        /* Used to iterate through constraint array */
+    for(i=0; i<pCsr->nConstraint; i++){
+      sqlite3_rtree_query_info *pInfo = pCsr->aConstraint[i].pInfo;
+      if( pInfo ){
+        if( pInfo->xDelUser ) pInfo->xDelUser(pInfo->pUser);
+        sqlite3_free(pInfo);
       }
-      if( fts3LcsIteratorAdvance(pAdv) ) nLive--;
     }
-
-    pInfo->aMatchinfo[iCol] = nLcs;
+    sqlite3_free(pCsr->aConstraint);
+    pCsr->aConstraint = 0;
   }
+}
 
-  sqlite3_free(aIter);
+/* 
+** Rtree virtual table module xClose method.
+*/
+static int rtreeClose(sqlite3_vtab_cursor *cur){
+  Rtree *pRtree = (Rtree *)(cur->pVtab);
+  int ii;
+  RtreeCursor *pCsr = (RtreeCursor *)cur;
+  freeCursorConstraints(pCsr);
+  sqlite3_free(pCsr->aPoint);
+  for(ii=0; ii<RTREE_CACHE_SZ; ii++) nodeRelease(pRtree, pCsr->aNode[ii]);
+  sqlite3_free(pCsr);
   return SQLITE_OK;
 }
 
 /*
-** Populate the buffer pInfo->aMatchinfo[] with an array of integers to
-** be returned by the matchinfo() function. Argument zArg contains the 
-** format string passed as the second argument to matchinfo (or the
-** default value "pcx" if no second argument was specified). The format
-** string has already been validated and the pInfo->aMatchinfo[] array
-** is guaranteed to be large enough for the output.
-**
-** If bGlobal is true, then populate all fields of the matchinfo() output.
-** If it is false, then assume that those fields that do not change between
-** rows (i.e. FTS3_MATCHINFO_NPHRASE, NCOL, NDOC, AVGLENGTH and part of HITS)
-** have already been populated.
+** Rtree virtual table module xEof method.
 **
-** Return SQLITE_OK if successful, or an SQLite error code if an error 
-** occurs. If a value other than SQLITE_OK is returned, the state the
-** pInfo->aMatchinfo[] buffer is left in is undefined.
+** Return non-zero if the cursor does not currently point to a valid 
+** record (i.e if the scan has finished), or zero otherwise.
 */
-static int fts3MatchinfoValues(
-  Fts3Cursor *pCsr,               /* FTS3 cursor object */
-  int bGlobal,                    /* True to grab the global stats */
-  MatchInfo *pInfo,               /* Matchinfo context object */
-  const char *zArg                /* Matchinfo format string */
-){
-  int rc = SQLITE_OK;
-  int i;
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  sqlite3_stmt *pSelect = 0;
-
-  for(i=0; rc==SQLITE_OK && zArg[i]; i++){
-
-    switch( zArg[i] ){
-      case FTS3_MATCHINFO_NPHRASE:
-        if( bGlobal ) pInfo->aMatchinfo[0] = pInfo->nPhrase;
-        break;
-
-      case FTS3_MATCHINFO_NCOL:
-        if( bGlobal ) pInfo->aMatchinfo[0] = pInfo->nCol;
-        break;
-        
-      case FTS3_MATCHINFO_NDOC:
-        if( bGlobal ){
-          sqlite3_int64 nDoc = 0;
-          rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &nDoc, 0);
-          pInfo->aMatchinfo[0] = (u32)nDoc;
-        }
-        break;
-
-      case FTS3_MATCHINFO_AVGLENGTH: 
-        if( bGlobal ){
-          sqlite3_int64 nDoc;     /* Number of rows in table */
-          const char *a;          /* Aggregate column length array */
-
-          rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &nDoc, &a);
-          if( rc==SQLITE_OK ){
-            int iCol;
-            for(iCol=0; iCol<pInfo->nCol; iCol++){
-              u32 iVal;
-              sqlite3_int64 nToken;
-              a += sqlite3Fts3GetVarint(a, &nToken);
-              iVal = (u32)(((u32)(nToken&0xffffffff)+nDoc/2)/nDoc);
-              pInfo->aMatchinfo[iCol] = iVal;
-            }
-          }
-        }
-        break;
+static int rtreeEof(sqlite3_vtab_cursor *cur){
+  RtreeCursor *pCsr = (RtreeCursor *)cur;
+  return pCsr->atEOF;
+}
 
-      case FTS3_MATCHINFO_LENGTH: {
-        sqlite3_stmt *pSelectDocsize = 0;
-        rc = sqlite3Fts3SelectDocsize(pTab, pCsr->iPrevId, &pSelectDocsize);
-        if( rc==SQLITE_OK ){
-          int iCol;
-          const char *a = sqlite3_column_blob(pSelectDocsize, 0);
-          for(iCol=0; iCol<pInfo->nCol; iCol++){
-            sqlite3_int64 nToken;
-            a += sqlite3Fts3GetVarint(a, &nToken);
-            pInfo->aMatchinfo[iCol] = (u32)nToken;
-          }
-        }
-        sqlite3_reset(pSelectDocsize);
-        break;
-      }
+/*
+** Convert raw bits from the on-disk RTree record into a coordinate value.
+** The on-disk format is big-endian and needs to be converted for little-
+** endian platforms.  The on-disk record stores integer coordinates if
+** eInt is true and it stores 32-bit floating point records if eInt is
+** false.  a[] is the four bytes of the on-disk record to be decoded.
+** Store the results in "r".
+**
+** There are three versions of this macro, one each for little-endian and
+** big-endian processors and a third generic implementation.  The endian-
+** specific implementations are much faster and are preferred if the
+** processor endianness is known at compile-time.  The SQLITE_BYTEORDER
+** macro is part of sqliteInt.h and hence the endian-specific
+** implementation will only be used if this module is compiled as part
+** of the amalgamation.
+*/
+#if defined(SQLITE_BYTEORDER) && SQLITE_BYTEORDER==1234
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    memcpy(&c.u,a,4);                                           \
+    c.u = ((c.u>>24)&0xff)|((c.u>>8)&0xff00)|                   \
+          ((c.u&0xff)<<24)|((c.u&0xff00)<<8);                   \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#elif defined(SQLITE_BYTEORDER) && SQLITE_BYTEORDER==4321
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    memcpy(&c.u,a,4);                                           \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#else
+#define RTREE_DECODE_COORD(eInt, a, r) {                        \
+    RtreeCoord c;    /* Coordinate decoded */                   \
+    c.u = ((u32)a[0]<<24) + ((u32)a[1]<<16)                     \
+           +((u32)a[2]<<8) + a[3];                              \
+    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
+}
+#endif
 
-      case FTS3_MATCHINFO_LCS:
-        rc = fts3ExprLoadDoclists(pCsr, 0, 0);
-        if( rc==SQLITE_OK ){
-          rc = fts3MatchinfoLcs(pCsr, pInfo);
-        }
-        break;
+/*
+** Check the RTree node or entry given by pCellData and p against the MATCH
+** constraint pConstraint.  
+*/
+static int rtreeCallbackConstraint(
+  RtreeConstraint *pConstraint,  /* The constraint to test */
+  int eInt,                      /* True if RTree holding integer coordinates */
+  u8 *pCellData,                 /* Raw cell content */
+  RtreeSearchPoint *pSearch,     /* Container of this cell */
+  sqlite3_rtree_dbl *prScore,    /* OUT: score for the cell */
+  int *peWithin                  /* OUT: visibility of the cell */
+){
+  int i;                                                /* Loop counter */
+  sqlite3_rtree_query_info *pInfo = pConstraint->pInfo; /* Callback info */
+  int nCoord = pInfo->nCoord;                           /* No. of coordinates */
+  int rc;                                             /* Callback return code */
+  sqlite3_rtree_dbl aCoord[RTREE_MAX_DIMENSIONS*2];   /* Decoded coordinates */
 
-      case FTS3_MATCHINFO_LHITS:
-        (void)fts3ExprIterate(pCsr->pExpr, fts3ExprLHitsCb, (void*)pInfo);
-        break;
+  assert( pConstraint->op==RTREE_MATCH || pConstraint->op==RTREE_QUERY );
+  assert( nCoord==2 || nCoord==4 || nCoord==6 || nCoord==8 || nCoord==10 );
 
-      default: {
-        Fts3Expr *pExpr;
-        assert( zArg[i]==FTS3_MATCHINFO_HITS );
-        pExpr = pCsr->pExpr;
-        rc = fts3ExprLoadDoclists(pCsr, 0, 0);
-        if( rc!=SQLITE_OK ) break;
-        if( bGlobal ){
-          if( pCsr->pDeferred ){
-            rc = fts3MatchinfoSelectDoctotal(pTab, &pSelect, &pInfo->nDoc, 0);
-            if( rc!=SQLITE_OK ) break;
-          }
-          rc = fts3ExprIterate(pExpr, fts3ExprGlobalHitsCb,(void*)pInfo);
-          if( rc!=SQLITE_OK ) break;
-        }
-        (void)fts3ExprIterate(pExpr, fts3ExprLocalHitsCb,(void*)pInfo);
-        break;
-      }
+  if( pConstraint->op==RTREE_QUERY && pSearch->iLevel==1 ){
+    pInfo->iRowid = readInt64(pCellData);
+  }
+  pCellData += 8;
+  for(i=0; i<nCoord; i++, pCellData += 4){
+    RTREE_DECODE_COORD(eInt, pCellData, aCoord[i]);
+  }
+  if( pConstraint->op==RTREE_MATCH ){
+    rc = pConstraint->u.xGeom((sqlite3_rtree_geometry*)pInfo,
+                              nCoord, aCoord, &i);
+    if( i==0 ) *peWithin = NOT_WITHIN;
+    *prScore = RTREE_ZERO;
+  }else{
+    pInfo->aCoord = aCoord;
+    pInfo->iLevel = pSearch->iLevel - 1;
+    pInfo->rScore = pInfo->rParentScore = pSearch->rScore;
+    pInfo->eWithin = pInfo->eParentWithin = pSearch->eWithin;
+    rc = pConstraint->u.xQueryFunc(pInfo);
+    if( pInfo->eWithin<*peWithin ) *peWithin = pInfo->eWithin;
+    if( pInfo->rScore<*prScore || *prScore<RTREE_ZERO ){
+      *prScore = pInfo->rScore;
     }
-
-    pInfo->aMatchinfo += fts3MatchinfoSize(pInfo, zArg[i]);
   }
-
-  sqlite3_reset(pSelect);
   return rc;
 }
 
-
-/*
-** Populate pCsr->aMatchinfo[] with data for the current row. The 
-** 'matchinfo' data is an array of 32-bit unsigned integers (C type u32).
+/* 
+** Check the internal RTree node given by pCellData against constraint p.
+** If this constraint cannot be satisfied by any child within the node,
+** set *peWithin to NOT_WITHIN.
 */
-static int fts3GetMatchinfo(
-  Fts3Cursor *pCsr,               /* FTS3 Cursor object */
-  const char *zArg                /* Second argument to matchinfo() function */
+static void rtreeNonleafConstraint(
+  RtreeConstraint *p,        /* The constraint to test */
+  int eInt,                  /* True if RTree holds integer coordinates */
+  u8 *pCellData,             /* Raw cell content as appears on disk */
+  int *peWithin              /* Adjust downward, as appropriate */
 ){
-  MatchInfo sInfo;
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  int rc = SQLITE_OK;
-  int bGlobal = 0;                /* Collect 'global' stats as well as local */
+  sqlite3_rtree_dbl val;     /* Coordinate value convert to a double */
 
-  memset(&sInfo, 0, sizeof(MatchInfo));
-  sInfo.pCursor = pCsr;
-  sInfo.nCol = pTab->nColumn;
+  /* p->iCoord might point to either a lower or upper bound coordinate
+  ** in a coordinate pair.  But make pCellData point to the lower bound.
+  */
+  pCellData += 8 + 4*(p->iCoord&0xfe);
 
-  /* If there is cached matchinfo() data, but the format string for the 
-  ** cache does not match the format string for this request, discard 
-  ** the cached data. */
-  if( pCsr->zMatchinfo && strcmp(pCsr->zMatchinfo, zArg) ){
-    assert( pCsr->aMatchinfo );
-    sqlite3_free(pCsr->aMatchinfo);
-    pCsr->zMatchinfo = 0;
-    pCsr->aMatchinfo = 0;
+  assert(p->op==RTREE_LE || p->op==RTREE_LT || p->op==RTREE_GE 
+      || p->op==RTREE_GT || p->op==RTREE_EQ );
+  switch( p->op ){
+    case RTREE_LE:
+    case RTREE_LT:
+    case RTREE_EQ:
+      RTREE_DECODE_COORD(eInt, pCellData, val);
+      /* val now holds the lower bound of the coordinate pair */
+      if( p->u.rValue>=val ) return;
+      if( p->op!=RTREE_EQ ) break;  /* RTREE_LE and RTREE_LT end here */
+      /* Fall through for the RTREE_EQ case */
+
+    default: /* RTREE_GT or RTREE_GE,  or fallthrough of RTREE_EQ */
+      pCellData += 4;
+      RTREE_DECODE_COORD(eInt, pCellData, val);
+      /* val now holds the upper bound of the coordinate pair */
+      if( p->u.rValue<=val ) return;
   }
+  *peWithin = NOT_WITHIN;
+}
 
-  /* If Fts3Cursor.aMatchinfo[] is NULL, then this is the first time the
-  ** matchinfo function has been called for this query. In this case 
-  ** allocate the array used to accumulate the matchinfo data and
-  ** initialize those elements that are constant for every row.
-  */
-  if( pCsr->aMatchinfo==0 ){
-    int nMatchinfo = 0;           /* Number of u32 elements in match-info */
-    int nArg;                     /* Bytes in zArg */
-    int i;                        /* Used to iterate through zArg */
+/*
+** Check the leaf RTree cell given by pCellData against constraint p.
+** If this constraint is not satisfied, set *peWithin to NOT_WITHIN.
+** If the constraint is satisfied, leave *peWithin unchanged.
+**
+** The constraint is of the form:  xN op $val
+**
+** The op is given by p->op.  The xN is p->iCoord-th coordinate in
+** pCellData.  $val is given by p->u.rValue.
+*/
+static void rtreeLeafConstraint(
+  RtreeConstraint *p,        /* The constraint to test */
+  int eInt,                  /* True if RTree holds integer coordinates */
+  u8 *pCellData,             /* Raw cell content as appears on disk */
+  int *peWithin              /* Adjust downward, as appropriate */
+){
+  RtreeDValue xN;      /* Coordinate value converted to a double */
 
-    /* Determine the number of phrases in the query */
-    pCsr->nPhrase = fts3ExprPhraseCount(pCsr->pExpr);
-    sInfo.nPhrase = pCsr->nPhrase;
+  assert(p->op==RTREE_LE || p->op==RTREE_LT || p->op==RTREE_GE 
+      || p->op==RTREE_GT || p->op==RTREE_EQ );
+  pCellData += 8 + p->iCoord*4;
+  RTREE_DECODE_COORD(eInt, pCellData, xN);
+  switch( p->op ){
+    case RTREE_LE: if( xN <= p->u.rValue ) return;  break;
+    case RTREE_LT: if( xN <  p->u.rValue ) return;  break;
+    case RTREE_GE: if( xN >= p->u.rValue ) return;  break;
+    case RTREE_GT: if( xN >  p->u.rValue ) return;  break;
+    default:       if( xN == p->u.rValue ) return;  break;
+  }
+  *peWithin = NOT_WITHIN;
+}
 
-    /* Determine the number of integers in the buffer returned by this call. */
-    for(i=0; zArg[i]; i++){
-      nMatchinfo += fts3MatchinfoSize(&sInfo, zArg[i]);
+/*
+** One of the cells in node pNode is guaranteed to have a 64-bit 
+** integer value equal to iRowid. Return the index of this cell.
+*/
+static int nodeRowidIndex(
+  Rtree *pRtree, 
+  RtreeNode *pNode, 
+  i64 iRowid,
+  int *piIndex
+){
+  int ii;
+  int nCell = NCELL(pNode);
+  assert( nCell<200 );
+  for(ii=0; ii<nCell; ii++){
+    if( nodeGetRowid(pRtree, pNode, ii)==iRowid ){
+      *piIndex = ii;
+      return SQLITE_OK;
     }
-
-    /* Allocate space for Fts3Cursor.aMatchinfo[] and Fts3Cursor.zMatchinfo. */
-    nArg = (int)strlen(zArg);
-    pCsr->aMatchinfo = (u32 *)sqlite3_malloc(sizeof(u32)*nMatchinfo + nArg + 1);
-    if( !pCsr->aMatchinfo ) return SQLITE_NOMEM;
-
-    pCsr->zMatchinfo = (char *)&pCsr->aMatchinfo[nMatchinfo];
-    pCsr->nMatchinfo = nMatchinfo;
-    memcpy(pCsr->zMatchinfo, zArg, nArg+1);
-    memset(pCsr->aMatchinfo, 0, sizeof(u32)*nMatchinfo);
-    pCsr->isMatchinfoNeeded = 1;
-    bGlobal = 1;
   }
+  return SQLITE_CORRUPT_VTAB;
+}
 
-  sInfo.aMatchinfo = pCsr->aMatchinfo;
-  sInfo.nPhrase = pCsr->nPhrase;
-  if( pCsr->isMatchinfoNeeded ){
-    rc = fts3MatchinfoValues(pCsr, bGlobal, &sInfo, zArg);
-    pCsr->isMatchinfoNeeded = 0;
+/*
+** Return the index of the cell containing a pointer to node pNode
+** in its parent. If pNode is the root node, return -1.
+*/
+static int nodeParentIndex(Rtree *pRtree, RtreeNode *pNode, int *piIndex){
+  RtreeNode *pParent = pNode->pParent;
+  if( pParent ){
+    return nodeRowidIndex(pRtree, pParent, pNode->iNode, piIndex);
   }
-
-  return rc;
+  *piIndex = -1;
+  return SQLITE_OK;
 }
 
 /*
-** Implementation of snippet() function.
+** Compare two search points.  Return negative, zero, or positive if the first
+** is less than, equal to, or greater than the second.
+**
+** The rScore is the primary key.  Smaller rScore values come first.
+** If the rScore is a tie, then use iLevel as the tie breaker with smaller
+** iLevel values coming first.  In this way, if rScore is the same for all
+** SearchPoints, then iLevel becomes the deciding factor and the result
+** is a depth-first search, which is the desired default behavior.
 */
-SQLITE_PRIVATE void sqlite3Fts3Snippet(
-  sqlite3_context *pCtx,          /* SQLite function call context */
-  Fts3Cursor *pCsr,               /* Cursor object */
-  const char *zStart,             /* Snippet start text - "<b>" */
-  const char *zEnd,               /* Snippet end text - "</b>" */
-  const char *zEllipsis,          /* Snippet ellipsis text - "<b>...</b>" */
-  int iCol,                       /* Extract snippet from this column */
-  int nToken                      /* Approximate number of tokens in snippet */
+static int rtreeSearchPointCompare(
+  const RtreeSearchPoint *pA,
+  const RtreeSearchPoint *pB
 ){
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  int rc = SQLITE_OK;
-  int i;
-  StrBuffer res = {0, 0, 0};
-
-  /* The returned text includes up to four fragments of text extracted from
-  ** the data in the current row. The first iteration of the for(...) loop
-  ** below attempts to locate a single fragment of text nToken tokens in 
-  ** size that contains at least one instance of all phrases in the query
-  ** expression that appear in the current row. If such a fragment of text
-  ** cannot be found, the second iteration of the loop attempts to locate
-  ** a pair of fragments, and so on.
-  */
-  int nSnippet = 0;               /* Number of fragments in this snippet */
-  SnippetFragment aSnippet[4];    /* Maximum of 4 fragments per snippet */
-  int nFToken = -1;               /* Number of tokens in each fragment */
+  if( pA->rScore<pB->rScore ) return -1;
+  if( pA->rScore>pB->rScore ) return +1;
+  if( pA->iLevel<pB->iLevel ) return -1;
+  if( pA->iLevel>pB->iLevel ) return +1;
+  return 0;
+}
 
-  if( !pCsr->pExpr ){
-    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
-    return;
+/*
+** Interchange to search points in a cursor.
+*/
+static void rtreeSearchPointSwap(RtreeCursor *p, int i, int j){
+  RtreeSearchPoint t = p->aPoint[i];
+  assert( i<j );
+  p->aPoint[i] = p->aPoint[j];
+  p->aPoint[j] = t;
+  i++; j++;
+  if( i<RTREE_CACHE_SZ ){
+    if( j>=RTREE_CACHE_SZ ){
+      nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
+      p->aNode[i] = 0;
+    }else{
+      RtreeNode *pTemp = p->aNode[i];
+      p->aNode[i] = p->aNode[j];
+      p->aNode[j] = pTemp;
+    }
   }
+}
 
-  for(nSnippet=1; 1; nSnippet++){
-
-    int iSnip;                    /* Loop counter 0..nSnippet-1 */
-    u64 mCovered = 0;             /* Bitmask of phrases covered by snippet */
-    u64 mSeen = 0;                /* Bitmask of phrases seen by BestSnippet() */
+/*
+** Return the search point with the lowest current score.
+*/
+static RtreeSearchPoint *rtreeSearchPointFirst(RtreeCursor *pCur){
+  return pCur->bPoint ? &pCur->sPoint : pCur->nPoint ? pCur->aPoint : 0;
+}
 
-    if( nToken>=0 ){
-      nFToken = (nToken+nSnippet-1) / nSnippet;
-    }else{
-      nFToken = -1 * nToken;
-    }
+/*
+** Get the RtreeNode for the search point with the lowest score.
+*/
+static RtreeNode *rtreeNodeOfFirstSearchPoint(RtreeCursor *pCur, int *pRC){
+  sqlite3_int64 id;
+  int ii = 1 - pCur->bPoint;
+  assert( ii==0 || ii==1 );
+  assert( pCur->bPoint || pCur->nPoint );
+  if( pCur->aNode[ii]==0 ){
+    assert( pRC!=0 );
+    id = ii ? pCur->aPoint[0].id : pCur->sPoint.id;
+    *pRC = nodeAcquire(RTREE_OF_CURSOR(pCur), id, 0, &pCur->aNode[ii]);
+  }
+  return pCur->aNode[ii];
+}
 
-    for(iSnip=0; iSnip<nSnippet; iSnip++){
-      int iBestScore = -1;        /* Best score of columns checked so far */
-      int iRead;                  /* Used to iterate through columns */
-      SnippetFragment *pFragment = &aSnippet[iSnip];
+/*
+** Push a new element onto the priority queue
+*/
+static RtreeSearchPoint *rtreeEnqueue(
+  RtreeCursor *pCur,    /* The cursor */
+  RtreeDValue rScore,   /* Score for the new search point */
+  u8 iLevel             /* Level for the new search point */
+){
+  int i, j;
+  RtreeSearchPoint *pNew;
+  if( pCur->nPoint>=pCur->nPointAlloc ){
+    int nNew = pCur->nPointAlloc*2 + 8;
+    pNew = sqlite3_realloc(pCur->aPoint, nNew*sizeof(pCur->aPoint[0]));
+    if( pNew==0 ) return 0;
+    pCur->aPoint = pNew;
+    pCur->nPointAlloc = nNew;
+  }
+  i = pCur->nPoint++;
+  pNew = pCur->aPoint + i;
+  pNew->rScore = rScore;
+  pNew->iLevel = iLevel;
+  assert( iLevel<=RTREE_MAX_DEPTH );
+  while( i>0 ){
+    RtreeSearchPoint *pParent;
+    j = (i-1)/2;
+    pParent = pCur->aPoint + j;
+    if( rtreeSearchPointCompare(pNew, pParent)>=0 ) break;
+    rtreeSearchPointSwap(pCur, j, i);
+    i = j;
+    pNew = pParent;
+  }
+  return pNew;
+}
 
-      memset(pFragment, 0, sizeof(*pFragment));
+/*
+** Allocate a new RtreeSearchPoint and return a pointer to it.  Return
+** NULL if malloc fails.
+*/
+static RtreeSearchPoint *rtreeSearchPointNew(
+  RtreeCursor *pCur,    /* The cursor */
+  RtreeDValue rScore,   /* Score for the new search point */
+  u8 iLevel             /* Level for the new search point */
+){
+  RtreeSearchPoint *pNew, *pFirst;
+  pFirst = rtreeSearchPointFirst(pCur);
+  pCur->anQueue[iLevel]++;
+  if( pFirst==0
+   || pFirst->rScore>rScore 
+   || (pFirst->rScore==rScore && pFirst->iLevel>iLevel)
+  ){
+    if( pCur->bPoint ){
+      int ii;
+      pNew = rtreeEnqueue(pCur, rScore, iLevel);
+      if( pNew==0 ) return 0;
+      ii = (int)(pNew - pCur->aPoint) + 1;
+      if( ii<RTREE_CACHE_SZ ){
+        assert( pCur->aNode[ii]==0 );
+        pCur->aNode[ii] = pCur->aNode[0];
+       }else{
+        nodeRelease(RTREE_OF_CURSOR(pCur), pCur->aNode[0]);
+      }
+      pCur->aNode[0] = 0;
+      *pNew = pCur->sPoint;
+    }
+    pCur->sPoint.rScore = rScore;
+    pCur->sPoint.iLevel = iLevel;
+    pCur->bPoint = 1;
+    return &pCur->sPoint;
+  }else{
+    return rtreeEnqueue(pCur, rScore, iLevel);
+  }
+}
 
-      /* Loop through all columns of the table being considered for snippets.
-      ** If the iCol argument to this function was negative, this means all
-      ** columns of the FTS3 table. Otherwise, only column iCol is considered.
-      */
-      for(iRead=0; iRead<pTab->nColumn; iRead++){
-        SnippetFragment sF = {0, 0, 0, 0};
-        int iS = 0;
-        if( iCol>=0 && iRead!=iCol ) continue;
+#if 0
+/* Tracing routines for the RtreeSearchPoint queue */
+static void tracePoint(RtreeSearchPoint *p, int idx, RtreeCursor *pCur){
+  if( idx<0 ){ printf(" s"); }else{ printf("%2d", idx); }
+  printf(" %d.%05lld.%02d %g %d",
+    p->iLevel, p->id, p->iCell, p->rScore, p->eWithin
+  );
+  idx++;
+  if( idx<RTREE_CACHE_SZ ){
+    printf(" %p\n", pCur->aNode[idx]);
+  }else{
+    printf("\n");
+  }
+}
+static void traceQueue(RtreeCursor *pCur, const char *zPrefix){
+  int ii;
+  printf("=== %9s ", zPrefix);
+  if( pCur->bPoint ){
+    tracePoint(&pCur->sPoint, -1, pCur);
+  }
+  for(ii=0; ii<pCur->nPoint; ii++){
+    if( ii>0 || pCur->bPoint ) printf("              ");
+    tracePoint(&pCur->aPoint[ii], ii, pCur);
+  }
+}
+# define RTREE_QUEUE_TRACE(A,B) traceQueue(A,B)
+#else
+# define RTREE_QUEUE_TRACE(A,B)   /* no-op */
+#endif
 
-        /* Find the best snippet of nFToken tokens in column iRead. */
-        rc = fts3BestSnippet(nFToken, pCsr, iRead, mCovered, &mSeen, &sF, &iS);
-        if( rc!=SQLITE_OK ){
-          goto snippet_out;
+/* Remove the search point with the lowest current score.
+*/
+static void rtreeSearchPointPop(RtreeCursor *p){
+  int i, j, k, n;
+  i = 1 - p->bPoint;
+  assert( i==0 || i==1 );
+  if( p->aNode[i] ){
+    nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
+    p->aNode[i] = 0;
+  }
+  if( p->bPoint ){
+    p->anQueue[p->sPoint.iLevel]--;
+    p->bPoint = 0;
+  }else if( p->nPoint ){
+    p->anQueue[p->aPoint[0].iLevel]--;
+    n = --p->nPoint;
+    p->aPoint[0] = p->aPoint[n];
+    if( n<RTREE_CACHE_SZ-1 ){
+      p->aNode[1] = p->aNode[n+1];
+      p->aNode[n+1] = 0;
+    }
+    i = 0;
+    while( (j = i*2+1)<n ){
+      k = j+1;
+      if( k<n && rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[j])<0 ){
+        if( rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[i])<0 ){
+          rtreeSearchPointSwap(p, i, k);
+          i = k;
+        }else{
+          break;
         }
-        if( iS>iBestScore ){
-          *pFragment = sF;
-          iBestScore = iS;
+      }else{
+        if( rtreeSearchPointCompare(&p->aPoint[j], &p->aPoint[i])<0 ){
+          rtreeSearchPointSwap(p, i, j);
+          i = j;
+        }else{
+          break;
         }
       }
-
-      mCovered |= pFragment->covered;
     }
-
-    /* If all query phrases seen by fts3BestSnippet() are present in at least
-    ** one of the nSnippet snippet fragments, break out of the loop.
-    */
-    assert( (mCovered&mSeen)==mCovered );
-    if( mSeen==mCovered || nSnippet==SizeofArray(aSnippet) ) break;
   }
+}
 
-  assert( nFToken>0 );
 
-  for(i=0; i<nSnippet && rc==SQLITE_OK; i++){
-    rc = fts3SnippetText(pCsr, &aSnippet[i], 
-        i, (i==nSnippet-1), nFToken, zStart, zEnd, zEllipsis, &res
-    );
-  }
+/*
+** Continue the search on cursor pCur until the front of the queue
+** contains an entry suitable for returning as a result-set row,
+** or until the RtreeSearchPoint queue is empty, indicating that the
+** query has completed.
+*/
+static int rtreeStepToLeaf(RtreeCursor *pCur){
+  RtreeSearchPoint *p;
+  Rtree *pRtree = RTREE_OF_CURSOR(pCur);
+  RtreeNode *pNode;
+  int eWithin;
+  int rc = SQLITE_OK;
+  int nCell;
+  int nConstraint = pCur->nConstraint;
+  int ii;
+  int eInt;
+  RtreeSearchPoint x;
 
- snippet_out:
-  sqlite3Fts3SegmentsClose(pTab);
-  if( rc!=SQLITE_OK ){
-    sqlite3_result_error_code(pCtx, rc);
-    sqlite3_free(res.z);
-  }else{
-    sqlite3_result_text(pCtx, res.z, -1, sqlite3_free);
+  eInt = pRtree->eCoordType==RTREE_COORD_INT32;
+  while( (p = rtreeSearchPointFirst(pCur))!=0 && p->iLevel>0 ){
+    pNode = rtreeNodeOfFirstSearchPoint(pCur, &rc);
+    if( rc ) return rc;
+    nCell = NCELL(pNode);
+    assert( nCell<200 );
+    while( p->iCell<nCell ){
+      sqlite3_rtree_dbl rScore = (sqlite3_rtree_dbl)-1;
+      u8 *pCellData = pNode->zData + (4+pRtree->nBytesPerCell*p->iCell);
+      eWithin = FULLY_WITHIN;
+      for(ii=0; ii<nConstraint; ii++){
+        RtreeConstraint *pConstraint = pCur->aConstraint + ii;
+        if( pConstraint->op>=RTREE_MATCH ){
+          rc = rtreeCallbackConstraint(pConstraint, eInt, pCellData, p,
+                                       &rScore, &eWithin);
+          if( rc ) return rc;
+        }else if( p->iLevel==1 ){
+          rtreeLeafConstraint(pConstraint, eInt, pCellData, &eWithin);
+        }else{
+          rtreeNonleafConstraint(pConstraint, eInt, pCellData, &eWithin);
+        }
+        if( eWithin==NOT_WITHIN ) break;
+      }
+      p->iCell++;
+      if( eWithin==NOT_WITHIN ) continue;
+      x.iLevel = p->iLevel - 1;
+      if( x.iLevel ){
+        x.id = readInt64(pCellData);
+        x.iCell = 0;
+      }else{
+        x.id = p->id;
+        x.iCell = p->iCell - 1;
+      }
+      if( p->iCell>=nCell ){
+        RTREE_QUEUE_TRACE(pCur, "POP-S:");
+        rtreeSearchPointPop(pCur);
+      }
+      if( rScore<RTREE_ZERO ) rScore = RTREE_ZERO;
+      p = rtreeSearchPointNew(pCur, rScore, x.iLevel);
+      if( p==0 ) return SQLITE_NOMEM;
+      p->eWithin = eWithin;
+      p->id = x.id;
+      p->iCell = x.iCell;
+      RTREE_QUEUE_TRACE(pCur, "PUSH-S:");
+      break;
+    }
+    if( p->iCell>=nCell ){
+      RTREE_QUEUE_TRACE(pCur, "POP-Se:");
+      rtreeSearchPointPop(pCur);
+    }
   }
+  pCur->atEOF = p==0;
+  return SQLITE_OK;
 }
 
+/* 
+** Rtree virtual table module xNext method.
+*/
+static int rtreeNext(sqlite3_vtab_cursor *pVtabCursor){
+  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
+  int rc = SQLITE_OK;
 
-typedef struct TermOffset TermOffset;
-typedef struct TermOffsetCtx TermOffsetCtx;
-
-struct TermOffset {
-  char *pList;                    /* Position-list */
-  int iPos;                       /* Position just read from pList */
-  int iOff;                       /* Offset of this term from read positions */
-};
+  /* Move to the next entry that matches the configured constraints. */
+  RTREE_QUEUE_TRACE(pCsr, "POP-Nx:");
+  rtreeSearchPointPop(pCsr);
+  rc = rtreeStepToLeaf(pCsr);
+  return rc;
+}
 
-struct TermOffsetCtx {
-  Fts3Cursor *pCsr;
-  int iCol;                       /* Column of table to populate aTerm for */
-  int iTerm;
-  sqlite3_int64 iDocid;
-  TermOffset *aTerm;
-};
+/* 
+** Rtree virtual table module xRowid method.
+*/
+static int rtreeRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *pRowid){
+  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
+  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
+  int rc = SQLITE_OK;
+  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);
+  if( rc==SQLITE_OK && p ){
+    *pRowid = nodeGetRowid(RTREE_OF_CURSOR(pCsr), pNode, p->iCell);
+  }
+  return rc;
+}
 
-/*
-** This function is an fts3ExprIterate() callback used by sqlite3Fts3Offsets().
+/* 
+** Rtree virtual table module xColumn method.
 */
-static int fts3ExprTermOffsetInit(Fts3Expr *pExpr, int iPhrase, void *ctx){
-  TermOffsetCtx *p = (TermOffsetCtx *)ctx;
-  int nTerm;                      /* Number of tokens in phrase */
-  int iTerm;                      /* For looping through nTerm phrase terms */
-  char *pList;                    /* Pointer to position list for phrase */
-  int iPos = 0;                   /* First position in position-list */
-  int rc;
+static int rtreeColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  Rtree *pRtree = (Rtree *)cur->pVtab;
+  RtreeCursor *pCsr = (RtreeCursor *)cur;
+  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
+  RtreeCoord c;
+  int rc = SQLITE_OK;
+  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);
 
-  UNUSED_PARAMETER(iPhrase);
-  rc = sqlite3Fts3EvalPhrasePoslist(p->pCsr, pExpr, p->iCol, &pList);
-  nTerm = pExpr->pPhrase->nToken;
-  if( pList ){
-    fts3GetDeltaPosition(&pList, &iPos);
-    assert( iPos>=0 );
+  if( rc ) return rc;
+  if( p==0 ) return SQLITE_OK;
+  if( i==0 ){
+    sqlite3_result_int64(ctx, nodeGetRowid(pRtree, pNode, p->iCell));
+  }else{
+    if( rc ) return rc;
+    nodeGetCoord(pRtree, pNode, p->iCell, i-1, &c);
+#ifndef SQLITE_RTREE_INT_ONLY
+    if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+      sqlite3_result_double(ctx, c.f);
+    }else
+#endif
+    {
+      assert( pRtree->eCoordType==RTREE_COORD_INT32 );
+      sqlite3_result_int(ctx, c.i);
+    }
   }
+  return SQLITE_OK;
+}
 
-  for(iTerm=0; iTerm<nTerm; iTerm++){
-    TermOffset *pT = &p->aTerm[p->iTerm++];
-    pT->iOff = nTerm-iTerm-1;
-    pT->pList = pList;
-    pT->iPos = iPos;
+/* 
+** Use nodeAcquire() to obtain the leaf node containing the record with 
+** rowid iRowid. If successful, set *ppLeaf to point to the node and
+** return SQLITE_OK. If there is no such record in the table, set
+** *ppLeaf to 0 and return SQLITE_OK. If an error occurs, set *ppLeaf
+** to zero and return an SQLite error code.
+*/
+static int findLeafNode(
+  Rtree *pRtree,              /* RTree to search */
+  i64 iRowid,                 /* The rowid searching for */
+  RtreeNode **ppLeaf,         /* Write the node here */
+  sqlite3_int64 *piNode       /* Write the node-id here */
+){
+  int rc;
+  *ppLeaf = 0;
+  sqlite3_bind_int64(pRtree->pReadRowid, 1, iRowid);
+  if( sqlite3_step(pRtree->pReadRowid)==SQLITE_ROW ){
+    i64 iNode = sqlite3_column_int64(pRtree->pReadRowid, 0);
+    if( piNode ) *piNode = iNode;
+    rc = nodeAcquire(pRtree, iNode, 0, ppLeaf);
+    sqlite3_reset(pRtree->pReadRowid);
+  }else{
+    rc = sqlite3_reset(pRtree->pReadRowid);
   }
-
   return rc;
 }
 
 /*
-** Implementation of offsets() function.
+** This function is called to configure the RtreeConstraint object passed
+** as the second argument for a MATCH constraint. The value passed as the
+** first argument to this function is the right-hand operand to the MATCH
+** operator.
 */
-SQLITE_PRIVATE void sqlite3Fts3Offsets(
-  sqlite3_context *pCtx,          /* SQLite function call context */
-  Fts3Cursor *pCsr                /* Cursor object */
-){
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  sqlite3_tokenizer_module const *pMod = pTab->pTokenizer->pModule;
-  int rc;                         /* Return Code */
-  int nToken;                     /* Number of tokens in query */
-  int iCol;                       /* Column currently being processed */
-  StrBuffer res = {0, 0, 0};      /* Result string */
-  TermOffsetCtx sCtx;             /* Context for fts3ExprTermOffsetInit() */
-
-  if( !pCsr->pExpr ){
-    sqlite3_result_text(pCtx, "", 0, SQLITE_STATIC);
-    return;
-  }
-
-  memset(&sCtx, 0, sizeof(sCtx));
-  assert( pCsr->isRequireSeek==0 );
+static int deserializeGeometry(sqlite3_value *pValue, RtreeConstraint *pCons){
+  RtreeMatchArg *pBlob;              /* BLOB returned by geometry function */
+  sqlite3_rtree_query_info *pInfo;   /* Callback information */
+  int nBlob;                         /* Size of the geometry function blob */
+  int nExpected;                     /* Expected size of the BLOB */
 
-  /* Count the number of terms in the query */
-  rc = fts3ExprLoadDoclists(pCsr, 0, &nToken);
-  if( rc!=SQLITE_OK ) goto offsets_out;
+  /* Check that value is actually a blob. */
+  if( sqlite3_value_type(pValue)!=SQLITE_BLOB ) return SQLITE_ERROR;
 
-  /* Allocate the array of TermOffset iterators. */
-  sCtx.aTerm = (TermOffset *)sqlite3_malloc(sizeof(TermOffset)*nToken);
-  if( 0==sCtx.aTerm ){
-    rc = SQLITE_NOMEM;
-    goto offsets_out;
+  /* Check that the blob is roughly the right size. */
+  nBlob = sqlite3_value_bytes(pValue);
+  if( nBlob<(int)sizeof(RtreeMatchArg) ){
+    return SQLITE_ERROR;
   }
-  sCtx.iDocid = pCsr->iPrevId;
-  sCtx.pCsr = pCsr;
 
-  /* Loop through the table columns, appending offset information to 
-  ** string-buffer res for each column.
-  */
-  for(iCol=0; iCol<pTab->nColumn; iCol++){
-    sqlite3_tokenizer_cursor *pC; /* Tokenizer cursor */
-    const char *ZDUMMY;           /* Dummy argument used with xNext() */
-    int NDUMMY = 0;               /* Dummy argument used with xNext() */
-    int iStart = 0;
-    int iEnd = 0;
-    int iCurrent = 0;
-    const char *zDoc;
-    int nDoc;
+  pInfo = (sqlite3_rtree_query_info*)sqlite3_malloc( sizeof(*pInfo)+nBlob );
+  if( !pInfo ) return SQLITE_NOMEM;
+  memset(pInfo, 0, sizeof(*pInfo));
+  pBlob = (RtreeMatchArg*)&pInfo[1];
 
-    /* Initialize the contents of sCtx.aTerm[] for column iCol. There is 
-    ** no way that this operation can fail, so the return code from
-    ** fts3ExprIterate() can be discarded.
-    */
-    sCtx.iCol = iCol;
-    sCtx.iTerm = 0;
-    (void)fts3ExprIterate(pCsr->pExpr, fts3ExprTermOffsetInit, (void *)&sCtx);
+  memcpy(pBlob, sqlite3_value_blob(pValue), nBlob);
+  nExpected = (int)(sizeof(RtreeMatchArg) +
+                    pBlob->nParam*sizeof(sqlite3_value*) +
+                    (pBlob->nParam-1)*sizeof(RtreeDValue));
+  if( pBlob->magic!=RTREE_GEOMETRY_MAGIC || nBlob!=nExpected ){
+    sqlite3_free(pInfo);
+    return SQLITE_ERROR;
+  }
+  pInfo->pContext = pBlob->cb.pContext;
+  pInfo->nParam = pBlob->nParam;
+  pInfo->aParam = pBlob->aParam;
+  pInfo->apSqlParam = pBlob->apSqlParam;
 
-    /* Retreive the text stored in column iCol. If an SQL NULL is stored 
-    ** in column iCol, jump immediately to the next iteration of the loop.
-    ** If an OOM occurs while retrieving the data (this can happen if SQLite
-    ** needs to transform the data from utf-16 to utf-8), return SQLITE_NOMEM 
-    ** to the caller. 
-    */
-    zDoc = (const char *)sqlite3_column_text(pCsr->pStmt, iCol+1);
-    nDoc = sqlite3_column_bytes(pCsr->pStmt, iCol+1);
-    if( zDoc==0 ){
-      if( sqlite3_column_type(pCsr->pStmt, iCol+1)==SQLITE_NULL ){
-        continue;
-      }
-      rc = SQLITE_NOMEM;
-      goto offsets_out;
-    }
+  if( pBlob->cb.xGeom ){
+    pCons->u.xGeom = pBlob->cb.xGeom;
+  }else{
+    pCons->op = RTREE_QUERY;
+    pCons->u.xQueryFunc = pBlob->cb.xQueryFunc;
+  }
+  pCons->pInfo = pInfo;
+  return SQLITE_OK;
+}
 
-    /* Initialize a tokenizer iterator to iterate through column iCol. */
-    rc = sqlite3Fts3OpenTokenizer(pTab->pTokenizer, pCsr->iLangid,
-        zDoc, nDoc, &pC
-    );
-    if( rc!=SQLITE_OK ) goto offsets_out;
+/* 
+** Rtree virtual table module xFilter method.
+*/
+static int rtreeFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  Rtree *pRtree = (Rtree *)pVtabCursor->pVtab;
+  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
+  RtreeNode *pRoot = 0;
+  int ii;
+  int rc = SQLITE_OK;
+  int iCell = 0;
 
-    rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
-    while( rc==SQLITE_OK ){
-      int i;                      /* Used to loop through terms */
-      int iMinPos = 0x7FFFFFFF;   /* Position of next token */
-      TermOffset *pTerm = 0;      /* TermOffset associated with next token */
+  rtreeReference(pRtree);
 
-      for(i=0; i<nToken; i++){
-        TermOffset *pT = &sCtx.aTerm[i];
-        if( pT->pList && (pT->iPos-pT->iOff)<iMinPos ){
-          iMinPos = pT->iPos-pT->iOff;
-          pTerm = pT;
-        }
-      }
+  /* Reset the cursor to the same state as rtreeOpen() leaves it in. */
+  freeCursorConstraints(pCsr);
+  sqlite3_free(pCsr->aPoint);
+  memset(pCsr, 0, sizeof(RtreeCursor));
+  pCsr->base.pVtab = (sqlite3_vtab*)pRtree;
 
-      if( !pTerm ){
-        /* All offsets for this column have been gathered. */
-        rc = SQLITE_DONE;
+  pCsr->iStrategy = idxNum;
+  if( idxNum==1 ){
+    /* Special case - lookup by rowid. */
+    RtreeNode *pLeaf;        /* Leaf on which the required cell resides */
+    RtreeSearchPoint *p;     /* Search point for the the leaf */
+    i64 iRowid = sqlite3_value_int64(argv[0]);
+    i64 iNode = 0;
+    rc = findLeafNode(pRtree, iRowid, &pLeaf, &iNode);
+    if( rc==SQLITE_OK && pLeaf!=0 ){
+      p = rtreeSearchPointNew(pCsr, RTREE_ZERO, 0);
+      assert( p!=0 );  /* Always returns pCsr->sPoint */
+      pCsr->aNode[0] = pLeaf;
+      p->id = iNode;
+      p->eWithin = PARTLY_WITHIN;
+      rc = nodeRowidIndex(pRtree, pLeaf, iRowid, &iCell);
+      p->iCell = iCell;
+      RTREE_QUEUE_TRACE(pCsr, "PUSH-F1:");
+    }else{
+      pCsr->atEOF = 1;
+    }
+  }else{
+    /* Normal case - r-tree scan. Set up the RtreeCursor.aConstraint array 
+    ** with the configured constraints. 
+    */
+    rc = nodeAcquire(pRtree, 1, 0, &pRoot);
+    if( rc==SQLITE_OK && argc>0 ){
+      pCsr->aConstraint = sqlite3_malloc(sizeof(RtreeConstraint)*argc);
+      pCsr->nConstraint = argc;
+      if( !pCsr->aConstraint ){
+        rc = SQLITE_NOMEM;
       }else{
-        assert( iCurrent<=iMinPos );
-        if( 0==(0xFE&*pTerm->pList) ){
-          pTerm->pList = 0;
-        }else{
-          fts3GetDeltaPosition(&pTerm->pList, &pTerm->iPos);
-        }
-        while( rc==SQLITE_OK && iCurrent<iMinPos ){
-          rc = pMod->xNext(pC, &ZDUMMY, &NDUMMY, &iStart, &iEnd, &iCurrent);
-        }
-        if( rc==SQLITE_OK ){
-          char aBuffer[64];
-          sqlite3_snprintf(sizeof(aBuffer), aBuffer, 
-              "%d %d %d %d ", iCol, pTerm-sCtx.aTerm, iStart, iEnd-iStart
-          );
-          rc = fts3StringAppend(&res, aBuffer, -1);
-        }else if( rc==SQLITE_DONE && pTab->zContentTbl==0 ){
-          rc = FTS_CORRUPT_VTAB;
+        memset(pCsr->aConstraint, 0, sizeof(RtreeConstraint)*argc);
+        memset(pCsr->anQueue, 0, sizeof(u32)*(pRtree->iDepth + 1));
+        assert( (idxStr==0 && argc==0)
+                || (idxStr && (int)strlen(idxStr)==argc*2) );
+        for(ii=0; ii<argc; ii++){
+          RtreeConstraint *p = &pCsr->aConstraint[ii];
+          p->op = idxStr[ii*2];
+          p->iCoord = idxStr[ii*2+1]-'0';
+          if( p->op>=RTREE_MATCH ){
+            /* A MATCH operator. The right-hand-side must be a blob that
+            ** can be cast into an RtreeMatchArg object. One created using
+            ** an sqlite3_rtree_geometry_callback() SQL user function.
+            */
+            rc = deserializeGeometry(argv[ii], p);
+            if( rc!=SQLITE_OK ){
+              break;
+            }
+            p->pInfo->nCoord = pRtree->nDim*2;
+            p->pInfo->anQueue = pCsr->anQueue;
+            p->pInfo->mxLevel = pRtree->iDepth + 1;
+          }else{
+#ifdef SQLITE_RTREE_INT_ONLY
+            p->u.rValue = sqlite3_value_int64(argv[ii]);
+#else
+            p->u.rValue = sqlite3_value_double(argv[ii]);
+#endif
+          }
         }
       }
     }
-    if( rc==SQLITE_DONE ){
-      rc = SQLITE_OK;
+    if( rc==SQLITE_OK ){
+      RtreeSearchPoint *pNew;
+      pNew = rtreeSearchPointNew(pCsr, RTREE_ZERO, pRtree->iDepth+1);
+      if( pNew==0 ) return SQLITE_NOMEM;
+      pNew->id = 1;
+      pNew->iCell = 0;
+      pNew->eWithin = PARTLY_WITHIN;
+      assert( pCsr->bPoint==1 );
+      pCsr->aNode[0] = pRoot;
+      pRoot = 0;
+      RTREE_QUEUE_TRACE(pCsr, "PUSH-Fm:");
+      rc = rtreeStepToLeaf(pCsr);
     }
-
-    pMod->xClose(pC);
-    if( rc!=SQLITE_OK ) goto offsets_out;
   }
 
- offsets_out:
-  sqlite3_free(sCtx.aTerm);
-  assert( rc!=SQLITE_DONE );
-  sqlite3Fts3SegmentsClose(pTab);
-  if( rc!=SQLITE_OK ){
-    sqlite3_result_error_code(pCtx,  rc);
-    sqlite3_free(res.z);
-  }else{
-    sqlite3_result_text(pCtx, res.z, res.n-1, sqlite3_free);
-  }
-  return;
+  nodeRelease(pRtree, pRoot);
+  rtreeRelease(pRtree);
+  return rc;
 }
 
 /*
-** Implementation of matchinfo() function.
+** Set the pIdxInfo->estimatedRows variable to nRow. Unless this
+** extension is currently being used by a version of SQLite too old to
+** support estimatedRows. In that case this function is a no-op.
 */
-SQLITE_PRIVATE void sqlite3Fts3Matchinfo(
-  sqlite3_context *pContext,      /* Function call context */
-  Fts3Cursor *pCsr,               /* FTS3 table cursor */
-  const char *zArg                /* Second arg to matchinfo() function */
-){
-  Fts3Table *pTab = (Fts3Table *)pCsr->base.pVtab;
-  int rc;
-  int i;
-  const char *zFormat;
-
-  if( zArg ){
-    for(i=0; zArg[i]; i++){
-      char *zErr = 0;
-      if( fts3MatchinfoCheck(pTab, zArg[i], &zErr) ){
-        sqlite3_result_error(pContext, zErr, -1);
-        sqlite3_free(zErr);
-        return;
-      }
-    }
-    zFormat = zArg;
-  }else{
-    zFormat = FTS3_MATCHINFO_DEFAULT;
-  }
-
-  if( !pCsr->pExpr ){
-    sqlite3_result_blob(pContext, "", 0, SQLITE_STATIC);
-    return;
-  }
-
-  /* Retrieve matchinfo() data. */
-  rc = fts3GetMatchinfo(pCsr, zFormat);
-  sqlite3Fts3SegmentsClose(pTab);
-
-  if( rc!=SQLITE_OK ){
-    sqlite3_result_error_code(pContext, rc);
-  }else{
-    int n = pCsr->nMatchinfo * sizeof(u32);
-    sqlite3_result_blob(pContext, pCsr->aMatchinfo, n, SQLITE_TRANSIENT);
+static void setEstimatedRows(sqlite3_index_info *pIdxInfo, i64 nRow){
+#if SQLITE_VERSION_NUMBER>=3008002
+  if( sqlite3_libversion_number()>=3008002 ){
+    pIdxInfo->estimatedRows = nRow;
   }
-}
-
 #endif
+}
 
-/************** End of fts3_snippet.c ****************************************/
-/************** Begin file fts3_unicode.c ************************************/
 /*
-** 2012 May 24
+** Rtree virtual table module xBestIndex method. There are three
+** table scan strategies to choose from (in order from most to 
+** least desirable):
 **
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
+**   idxNum     idxStr        Strategy
+**   ------------------------------------------------
+**     1        Unused        Direct lookup by rowid.
+**     2        See below     R-tree query or full-table scan.
+**   ------------------------------------------------
 **
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
+** If strategy 1 is used, then idxStr is not meaningful. If strategy
+** 2 is used, idxStr is formatted to contain 2 bytes for each 
+** constraint used. The first two bytes of idxStr correspond to 
+** the constraint in sqlite3_index_info.aConstraintUsage[] with
+** (argvIndex==1) etc.
 **
-******************************************************************************
+** The first of each pair of bytes in idxStr identifies the constraint
+** operator as follows:
 **
-** Implementation of the "unicode" full-text-search tokenizer.
-*/
-
-#ifndef SQLITE_DISABLE_FTS3_UNICODE
-
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
-
-/* #include <assert.h> */
-/* #include <stdlib.h> */
-/* #include <stdio.h> */
-/* #include <string.h> */
-
-
-/*
-** The following two macros - READ_UTF8 and WRITE_UTF8 - have been copied
-** from the sqlite3 source file utf.c. If this file is compiled as part
-** of the amalgamation, they are not required.
+**   Operator    Byte Value
+**   ----------------------
+**      =        0x41 ('A')
+**     <=        0x42 ('B')
+**      <        0x43 ('C')
+**     >=        0x44 ('D')
+**      >        0x45 ('E')
+**   MATCH       0x46 ('F')
+**   ----------------------
+**
+** The second of each pair of bytes identifies the coordinate column
+** to which the constraint applies. The leftmost coordinate column
+** is 'a', the second from the left 'b' etc.
 */
-#ifndef SQLITE_AMALGAMATION
+static int rtreeBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  Rtree *pRtree = (Rtree*)tab;
+  int rc = SQLITE_OK;
+  int ii;
+  int bMatch = 0;                 /* True if there exists a MATCH constraint */
+  i64 nRow;                       /* Estimated rows returned by this scan */
 
-static const unsigned char sqlite3Utf8Trans1[] = {
-  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
-  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
-  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
-  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
-  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-  0x00, 0x01, 0x02, 0x03, 0x00, 0x01, 0x00, 0x00,
-};
+  int iIdx = 0;
+  char zIdxStr[RTREE_MAX_DIMENSIONS*8+1];
+  memset(zIdxStr, 0, sizeof(zIdxStr));
 
-#define READ_UTF8(zIn, zTerm, c)                           \
-  c = *(zIn++);                                            \
-  if( c>=0xc0 ){                                           \
-    c = sqlite3Utf8Trans1[c-0xc0];                         \
-    while( zIn!=zTerm && (*zIn & 0xc0)==0x80 ){            \
-      c = (c<<6) + (0x3f & *(zIn++));                      \
-    }                                                      \
-    if( c<0x80                                             \
-        || (c&0xFFFFF800)==0xD800                          \
-        || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }        \
+  /* Check if there exists a MATCH constraint - even an unusable one. If there
+  ** is, do not consider the lookup-by-rowid plan as using such a plan would
+  ** require the VDBE to evaluate the MATCH constraint, which is not currently
+  ** possible. */
+  for(ii=0; ii<pIdxInfo->nConstraint; ii++){
+    if( pIdxInfo->aConstraint[ii].op==SQLITE_INDEX_CONSTRAINT_MATCH ){
+      bMatch = 1;
+    }
   }
 
-#define WRITE_UTF8(zOut, c) {                          \
-  if( c<0x00080 ){                                     \
-    *zOut++ = (u8)(c&0xFF);                            \
-  }                                                    \
-  else if( c<0x00800 ){                                \
-    *zOut++ = 0xC0 + (u8)((c>>6)&0x1F);                \
-    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
-  }                                                    \
-  else if( c<0x10000 ){                                \
-    *zOut++ = 0xE0 + (u8)((c>>12)&0x0F);               \
-    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
-    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
-  }else{                                               \
-    *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);             \
-    *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);             \
-    *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);              \
-    *zOut++ = 0x80 + (u8)(c & 0x3F);                   \
-  }                                                    \
-}
+  assert( pIdxInfo->idxStr==0 );
+  for(ii=0; ii<pIdxInfo->nConstraint && iIdx<(int)(sizeof(zIdxStr)-1); ii++){
+    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[ii];
+
+    if( bMatch==0 && p->usable 
+     && p->iColumn==0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ 
+    ){
+      /* We have an equality constraint on the rowid. Use strategy 1. */
+      int jj;
+      for(jj=0; jj<ii; jj++){
+        pIdxInfo->aConstraintUsage[jj].argvIndex = 0;
+        pIdxInfo->aConstraintUsage[jj].omit = 0;
+      }
+      pIdxInfo->idxNum = 1;
+      pIdxInfo->aConstraintUsage[ii].argvIndex = 1;
+      pIdxInfo->aConstraintUsage[jj].omit = 1;
 
-#endif /* ifndef SQLITE_AMALGAMATION */
+      /* This strategy involves a two rowid lookups on an B-Tree structures
+      ** and then a linear search of an R-Tree node. This should be 
+      ** considered almost as quick as a direct rowid lookup (for which 
+      ** sqlite uses an internal cost of 0.0). It is expected to return
+      ** a single row.
+      */ 
+      pIdxInfo->estimatedCost = 30.0;
+      setEstimatedRows(pIdxInfo, 1);
+      return SQLITE_OK;
+    }
 
-typedef struct unicode_tokenizer unicode_tokenizer;
-typedef struct unicode_cursor unicode_cursor;
+    if( p->usable && (p->iColumn>0 || p->op==SQLITE_INDEX_CONSTRAINT_MATCH) ){
+      u8 op;
+      switch( p->op ){
+        case SQLITE_INDEX_CONSTRAINT_EQ: op = RTREE_EQ; break;
+        case SQLITE_INDEX_CONSTRAINT_GT: op = RTREE_GT; break;
+        case SQLITE_INDEX_CONSTRAINT_LE: op = RTREE_LE; break;
+        case SQLITE_INDEX_CONSTRAINT_LT: op = RTREE_LT; break;
+        case SQLITE_INDEX_CONSTRAINT_GE: op = RTREE_GE; break;
+        default:
+          assert( p->op==SQLITE_INDEX_CONSTRAINT_MATCH );
+          op = RTREE_MATCH; 
+          break;
+      }
+      zIdxStr[iIdx++] = op;
+      zIdxStr[iIdx++] = p->iColumn - 1 + '0';
+      pIdxInfo->aConstraintUsage[ii].argvIndex = (iIdx/2);
+      pIdxInfo->aConstraintUsage[ii].omit = 1;
+    }
+  }
 
-struct unicode_tokenizer {
-  sqlite3_tokenizer base;
-  int bRemoveDiacritic;
-  int nException;
-  int *aiException;
-};
+  pIdxInfo->idxNum = 2;
+  pIdxInfo->needToFreeIdxStr = 1;
+  if( iIdx>0 && 0==(pIdxInfo->idxStr = sqlite3_mprintf("%s", zIdxStr)) ){
+    return SQLITE_NOMEM;
+  }
 
-struct unicode_cursor {
-  sqlite3_tokenizer_cursor base;
-  const unsigned char *aInput;    /* Input text being tokenized */
-  int nInput;                     /* Size of aInput[] in bytes */
-  int iOff;                       /* Current offset within aInput[] */
-  int iToken;                     /* Index of next token to be returned */
-  char *zToken;                   /* storage for current token */
-  int nAlloc;                     /* space allocated at zToken */
-};
+  nRow = pRtree->nRowEst / (iIdx + 1);
+  pIdxInfo->estimatedCost = (double)6.0 * (double)nRow;
+  setEstimatedRows(pIdxInfo, nRow);
 
+  return rc;
+}
 
 /*
-** Destroy a tokenizer allocated by unicodeCreate().
+** Return the N-dimensional volumn of the cell stored in *p.
 */
-static int unicodeDestroy(sqlite3_tokenizer *pTokenizer){
-  if( pTokenizer ){
-    unicode_tokenizer *p = (unicode_tokenizer *)pTokenizer;
-    sqlite3_free(p->aiException);
-    sqlite3_free(p);
+static RtreeDValue cellArea(Rtree *pRtree, RtreeCell *p){
+  RtreeDValue area = (RtreeDValue)1;
+  int ii;
+  for(ii=0; ii<(pRtree->nDim*2); ii+=2){
+    area = (area * (DCOORD(p->aCoord[ii+1]) - DCOORD(p->aCoord[ii])));
   }
-  return SQLITE_OK;
+  return area;
 }
 
 /*
-** As part of a tokenchars= or separators= option, the CREATE VIRTUAL TABLE
-** statement has specified that the tokenizer for this table shall consider
-** all characters in string zIn/nIn to be separators (if bAlnum==0) or
-** token characters (if bAlnum==1).
-**
-** For each codepoint in the zIn/nIn string, this function checks if the
-** sqlite3FtsUnicodeIsalnum() function already returns the desired result.
-** If so, no action is taken. Otherwise, the codepoint is added to the 
-** unicode_tokenizer.aiException[] array. For the purposes of tokenization,
-** the return value of sqlite3FtsUnicodeIsalnum() is inverted for all
-** codepoints in the aiException[] array.
-**
-** If a standalone diacritic mark (one that sqlite3FtsUnicodeIsdiacritic()
-** identifies as a diacritic) occurs in the zIn/nIn string it is ignored.
-** It is not possible to change the behavior of the tokenizer with respect
-** to these codepoints.
+** Return the margin length of cell p. The margin length is the sum
+** of the objects size in each dimension.
 */
-static int unicodeAddExceptions(
-  unicode_tokenizer *p,           /* Tokenizer to add exceptions to */
-  int bAlnum,                     /* Replace Isalnum() return value with this */
-  const char *zIn,                /* Array of characters to make exceptions */
-  int nIn                         /* Length of z in bytes */
-){
-  const unsigned char *z = (const unsigned char *)zIn;
-  const unsigned char *zTerm = &z[nIn];
-  int iCode;
-  int nEntry = 0;
-
-  assert( bAlnum==0 || bAlnum==1 );
+static RtreeDValue cellMargin(Rtree *pRtree, RtreeCell *p){
+  RtreeDValue margin = (RtreeDValue)0;
+  int ii;
+  for(ii=0; ii<(pRtree->nDim*2); ii+=2){
+    margin += (DCOORD(p->aCoord[ii+1]) - DCOORD(p->aCoord[ii]));
+  }
+  return margin;
+}
 
-  while( z<zTerm ){
-    READ_UTF8(z, zTerm, iCode);
-    assert( (sqlite3FtsUnicodeIsalnum(iCode) & 0xFFFFFFFE)==0 );
-    if( sqlite3FtsUnicodeIsalnum(iCode)!=bAlnum 
-     && sqlite3FtsUnicodeIsdiacritic(iCode)==0 
-    ){
-      nEntry++;
+/*
+** Store the union of cells p1 and p2 in p1.
+*/
+static void cellUnion(Rtree *pRtree, RtreeCell *p1, RtreeCell *p2){
+  int ii;
+  if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+    for(ii=0; ii<(pRtree->nDim*2); ii+=2){
+      p1->aCoord[ii].f = MIN(p1->aCoord[ii].f, p2->aCoord[ii].f);
+      p1->aCoord[ii+1].f = MAX(p1->aCoord[ii+1].f, p2->aCoord[ii+1].f);
+    }
+  }else{
+    for(ii=0; ii<(pRtree->nDim*2); ii+=2){
+      p1->aCoord[ii].i = MIN(p1->aCoord[ii].i, p2->aCoord[ii].i);
+      p1->aCoord[ii+1].i = MAX(p1->aCoord[ii+1].i, p2->aCoord[ii+1].i);
     }
   }
+}
 
-  if( nEntry ){
-    int *aNew;                    /* New aiException[] array */
-    int nNew;                     /* Number of valid entries in array aNew[] */
-
-    aNew = sqlite3_realloc(p->aiException, (p->nException+nEntry)*sizeof(int));
-    if( aNew==0 ) return SQLITE_NOMEM;
-    nNew = p->nException;
-
-    z = (const unsigned char *)zIn;
-    while( z<zTerm ){
-      READ_UTF8(z, zTerm, iCode);
-      if( sqlite3FtsUnicodeIsalnum(iCode)!=bAlnum 
-       && sqlite3FtsUnicodeIsdiacritic(iCode)==0
-      ){
-        int i, j;
-        for(i=0; i<nNew && aNew[i]<iCode; i++);
-        for(j=nNew; j>i; j--) aNew[j] = aNew[j-1];
-        aNew[i] = iCode;
-        nNew++;
-      }
+/*
+** Return true if the area covered by p2 is a subset of the area covered
+** by p1. False otherwise.
+*/
+static int cellContains(Rtree *pRtree, RtreeCell *p1, RtreeCell *p2){
+  int ii;
+  int isInt = (pRtree->eCoordType==RTREE_COORD_INT32);
+  for(ii=0; ii<(pRtree->nDim*2); ii+=2){
+    RtreeCoord *a1 = &p1->aCoord[ii];
+    RtreeCoord *a2 = &p2->aCoord[ii];
+    if( (!isInt && (a2[0].f<a1[0].f || a2[1].f>a1[1].f)) 
+     || ( isInt && (a2[0].i<a1[0].i || a2[1].i>a1[1].i)) 
+    ){
+      return 0;
     }
-    p->aiException = aNew;
-    p->nException = nNew;
   }
-
-  return SQLITE_OK;
+  return 1;
 }
 
 /*
-** Return true if the p->aiException[] array contains the value iCode.
+** Return the amount cell p would grow by if it were unioned with pCell.
 */
-static int unicodeIsException(unicode_tokenizer *p, int iCode){
-  if( p->nException>0 ){
-    int *a = p->aiException;
-    int iLo = 0;
-    int iHi = p->nException-1;
+static RtreeDValue cellGrowth(Rtree *pRtree, RtreeCell *p, RtreeCell *pCell){
+  RtreeDValue area;
+  RtreeCell cell;
+  memcpy(&cell, p, sizeof(RtreeCell));
+  area = cellArea(pRtree, &cell);
+  cellUnion(pRtree, &cell, pCell);
+  return (cellArea(pRtree, &cell)-area);
+}
 
-    while( iHi>=iLo ){
-      int iTest = (iHi + iLo) / 2;
-      if( iCode==a[iTest] ){
-        return 1;
-      }else if( iCode>a[iTest] ){
-        iLo = iTest+1;
+static RtreeDValue cellOverlap(
+  Rtree *pRtree, 
+  RtreeCell *p, 
+  RtreeCell *aCell, 
+  int nCell
+){
+  int ii;
+  RtreeDValue overlap = RTREE_ZERO;
+  for(ii=0; ii<nCell; ii++){
+    int jj;
+    RtreeDValue o = (RtreeDValue)1;
+    for(jj=0; jj<(pRtree->nDim*2); jj+=2){
+      RtreeDValue x1, x2;
+      x1 = MAX(DCOORD(p->aCoord[jj]), DCOORD(aCell[ii].aCoord[jj]));
+      x2 = MIN(DCOORD(p->aCoord[jj+1]), DCOORD(aCell[ii].aCoord[jj+1]));
+      if( x2<x1 ){
+        o = (RtreeDValue)0;
+        break;
       }else{
-        iHi = iTest-1;
+        o = o * (x2-x1);
       }
     }
+    overlap += o;
   }
-
-  return 0;
+  return overlap;
 }
 
-/*
-** Return true if, for the purposes of tokenization, codepoint iCode is
-** considered a token character (not a separator).
-*/
-static int unicodeIsAlnum(unicode_tokenizer *p, int iCode){
-  assert( (sqlite3FtsUnicodeIsalnum(iCode) & 0xFFFFFFFE)==0 );
-  return sqlite3FtsUnicodeIsalnum(iCode) ^ unicodeIsException(p, iCode);
-}
 
 /*
-** Create a new tokenizer instance.
+** This function implements the ChooseLeaf algorithm from Gutman[84].
+** ChooseSubTree in r*tree terminology.
 */
-static int unicodeCreate(
-  int nArg,                       /* Size of array argv[] */
-  const char * const *azArg,      /* Tokenizer creation arguments */
-  sqlite3_tokenizer **pp          /* OUT: New tokenizer handle */
+static int ChooseLeaf(
+  Rtree *pRtree,               /* Rtree table */
+  RtreeCell *pCell,            /* Cell to insert into rtree */
+  int iHeight,                 /* Height of sub-tree rooted at pCell */
+  RtreeNode **ppLeaf           /* OUT: Selected leaf page */
 ){
-  unicode_tokenizer *pNew;        /* New tokenizer object */
-  int i;
-  int rc = SQLITE_OK;
+  int rc;
+  int ii;
+  RtreeNode *pNode;
+  rc = nodeAcquire(pRtree, 1, 0, &pNode);
 
-  pNew = (unicode_tokenizer *) sqlite3_malloc(sizeof(unicode_tokenizer));
-  if( pNew==NULL ) return SQLITE_NOMEM;
-  memset(pNew, 0, sizeof(unicode_tokenizer));
-  pNew->bRemoveDiacritic = 1;
+  for(ii=0; rc==SQLITE_OK && ii<(pRtree->iDepth-iHeight); ii++){
+    int iCell;
+    sqlite3_int64 iBest = 0;
 
-  for(i=0; rc==SQLITE_OK && i<nArg; i++){
-    const char *z = azArg[i];
-    int n = (int)strlen(z);
+    RtreeDValue fMinGrowth = RTREE_ZERO;
+    RtreeDValue fMinArea = RTREE_ZERO;
 
-    if( n==19 && memcmp("remove_diacritics=1", z, 19)==0 ){
-      pNew->bRemoveDiacritic = 1;
-    }
-    else if( n==19 && memcmp("remove_diacritics=0", z, 19)==0 ){
-      pNew->bRemoveDiacritic = 0;
-    }
-    else if( n>=11 && memcmp("tokenchars=", z, 11)==0 ){
-      rc = unicodeAddExceptions(pNew, 1, &z[11], n-11);
-    }
-    else if( n>=11 && memcmp("separators=", z, 11)==0 ){
-      rc = unicodeAddExceptions(pNew, 0, &z[11], n-11);
-    }
-    else{
-      /* Unrecognized argument */
-      rc  = SQLITE_ERROR;
+    int nCell = NCELL(pNode);
+    RtreeCell cell;
+    RtreeNode *pChild;
+
+    RtreeCell *aCell = 0;
+
+    /* Select the child node which will be enlarged the least if pCell
+    ** is inserted into it. Resolve ties by choosing the entry with
+    ** the smallest area.
+    */
+    for(iCell=0; iCell<nCell; iCell++){
+      int bBest = 0;
+      RtreeDValue growth;
+      RtreeDValue area;
+      nodeGetCell(pRtree, pNode, iCell, &cell);
+      growth = cellGrowth(pRtree, &cell, pCell);
+      area = cellArea(pRtree, &cell);
+      if( iCell==0||growth<fMinGrowth||(growth==fMinGrowth && area<fMinArea) ){
+        bBest = 1;
+      }
+      if( bBest ){
+        fMinGrowth = growth;
+        fMinArea = area;
+        iBest = cell.iRowid;
+      }
     }
-  }
 
-  if( rc!=SQLITE_OK ){
-    unicodeDestroy((sqlite3_tokenizer *)pNew);
-    pNew = 0;
+    sqlite3_free(aCell);
+    rc = nodeAcquire(pRtree, iBest, pNode, &pChild);
+    nodeRelease(pRtree, pNode);
+    pNode = pChild;
   }
-  *pp = (sqlite3_tokenizer *)pNew;
+
+  *ppLeaf = pNode;
   return rc;
 }
 
 /*
-** Prepare to begin tokenizing a particular string.  The input
-** string to be tokenized is pInput[0..nBytes-1].  A cursor
-** used to incrementally tokenize this string is returned in 
-** *ppCursor.
+** A cell with the same content as pCell has just been inserted into
+** the node pNode. This function updates the bounding box cells in
+** all ancestor elements.
 */
-static int unicodeOpen(
-  sqlite3_tokenizer *p,           /* The tokenizer */
-  const char *aInput,             /* Input string */
-  int nInput,                     /* Size of string aInput in bytes */
-  sqlite3_tokenizer_cursor **pp   /* OUT: New cursor object */
+static int AdjustTree(
+  Rtree *pRtree,                    /* Rtree table */
+  RtreeNode *pNode,                 /* Adjust ancestry of this node. */
+  RtreeCell *pCell                  /* This cell was just inserted */
 ){
-  unicode_cursor *pCsr;
+  RtreeNode *p = pNode;
+  while( p->pParent ){
+    RtreeNode *pParent = p->pParent;
+    RtreeCell cell;
+    int iCell;
 
-  pCsr = (unicode_cursor *)sqlite3_malloc(sizeof(unicode_cursor));
-  if( pCsr==0 ){
-    return SQLITE_NOMEM;
-  }
-  memset(pCsr, 0, sizeof(unicode_cursor));
+    if( nodeParentIndex(pRtree, p, &iCell) ){
+      return SQLITE_CORRUPT_VTAB;
+    }
 
-  pCsr->aInput = (const unsigned char *)aInput;
-  if( aInput==0 ){
-    pCsr->nInput = 0;
-  }else if( nInput<0 ){
-    pCsr->nInput = (int)strlen(aInput);
-  }else{
-    pCsr->nInput = nInput;
+    nodeGetCell(pRtree, pParent, iCell, &cell);
+    if( !cellContains(pRtree, &cell, pCell) ){
+      cellUnion(pRtree, &cell, pCell);
+      nodeOverwriteCell(pRtree, pParent, &cell, iCell);
+    }
+ 
+    p = pParent;
   }
-
-  *pp = &pCsr->base;
-  UNUSED_PARAMETER(p);
   return SQLITE_OK;
 }
 
 /*
-** Close a tokenization cursor previously opened by a call to
-** simpleOpen() above.
+** Write mapping (iRowid->iNode) to the <rtree>_rowid table.
 */
-static int unicodeClose(sqlite3_tokenizer_cursor *pCursor){
-  unicode_cursor *pCsr = (unicode_cursor *) pCursor;
-  sqlite3_free(pCsr->zToken);
-  sqlite3_free(pCsr);
-  return SQLITE_OK;
+static int rowidWrite(Rtree *pRtree, sqlite3_int64 iRowid, sqlite3_int64 iNode){
+  sqlite3_bind_int64(pRtree->pWriteRowid, 1, iRowid);
+  sqlite3_bind_int64(pRtree->pWriteRowid, 2, iNode);
+  sqlite3_step(pRtree->pWriteRowid);
+  return sqlite3_reset(pRtree->pWriteRowid);
 }
 
 /*
-** Extract the next token from a tokenization cursor.  The cursor must
-** have been opened by a prior call to simpleOpen().
+** Write mapping (iNode->iPar) to the <rtree>_parent table.
 */
-static int unicodeNext(
-  sqlite3_tokenizer_cursor *pC,   /* Cursor returned by simpleOpen */
-  const char **paToken,           /* OUT: Token text */
-  int *pnToken,                   /* OUT: Number of bytes at *paToken */
-  int *piStart,                   /* OUT: Starting offset of token */
-  int *piEnd,                     /* OUT: Ending offset of token */
-  int *piPos                      /* OUT: Position integer of token */
-){
-  unicode_cursor *pCsr = (unicode_cursor *)pC;
-  unicode_tokenizer *p = ((unicode_tokenizer *)pCsr->base.pTokenizer);
-  int iCode = 0;
-  char *zOut;
-  const unsigned char *z = &pCsr->aInput[pCsr->iOff];
-  const unsigned char *zStart = z;
-  const unsigned char *zEnd;
-  const unsigned char *zTerm = &pCsr->aInput[pCsr->nInput];
-
-  /* Scan past any delimiter characters before the start of the next token.
-  ** Return SQLITE_DONE early if this takes us all the way to the end of 
-  ** the input.  */
-  while( z<zTerm ){
-    READ_UTF8(z, zTerm, iCode);
-    if( unicodeIsAlnum(p, iCode) ) break;
-    zStart = z;
-  }
-  if( zStart>=zTerm ) return SQLITE_DONE;
-
-  zOut = pCsr->zToken;
-  do {
-    int iOut;
-
-    /* Grow the output buffer if required. */
-    if( (zOut-pCsr->zToken)>=(pCsr->nAlloc-4) ){
-      char *zNew = sqlite3_realloc(pCsr->zToken, pCsr->nAlloc+64);
-      if( !zNew ) return SQLITE_NOMEM;
-      zOut = &zNew[zOut - pCsr->zToken];
-      pCsr->zToken = zNew;
-      pCsr->nAlloc += 64;
-    }
-
-    /* Write the folded case of the last character read to the output */
-    zEnd = z;
-    iOut = sqlite3FtsUnicodeFold(iCode, p->bRemoveDiacritic);
-    if( iOut ){
-      WRITE_UTF8(zOut, iOut);
-    }
-
-    /* If the cursor is not at EOF, read the next character */
-    if( z>=zTerm ) break;
-    READ_UTF8(z, zTerm, iCode);
-  }while( unicodeIsAlnum(p, iCode) 
-       || sqlite3FtsUnicodeIsdiacritic(iCode)
-  );
-
-  /* Set the output variables and return. */
-  pCsr->iOff = (int)(z - pCsr->aInput);
-  *paToken = pCsr->zToken;
-  *pnToken = (int)(zOut - pCsr->zToken);
-  *piStart = (int)(zStart - pCsr->aInput);
-  *piEnd = (int)(zEnd - pCsr->aInput);
-  *piPos = pCsr->iToken++;
-  return SQLITE_OK;
+static int parentWrite(Rtree *pRtree, sqlite3_int64 iNode, sqlite3_int64 iPar){
+  sqlite3_bind_int64(pRtree->pWriteParent, 1, iNode);
+  sqlite3_bind_int64(pRtree->pWriteParent, 2, iPar);
+  sqlite3_step(pRtree->pWriteParent);
+  return sqlite3_reset(pRtree->pWriteParent);
 }
 
-/*
-** Set *ppModule to a pointer to the sqlite3_tokenizer_module 
-** structure for the unicode tokenizer.
-*/
-SQLITE_PRIVATE void sqlite3Fts3UnicodeTokenizer(sqlite3_tokenizer_module const **ppModule){
-  static const sqlite3_tokenizer_module module = {
-    0,
-    unicodeCreate,
-    unicodeDestroy,
-    unicodeOpen,
-    unicodeClose,
-    unicodeNext,
-    0,
-  };
-  *ppModule = &module;
-}
+static int rtreeInsertCell(Rtree *, RtreeNode *, RtreeCell *, int);
 
-#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
-#endif /* ifndef SQLITE_DISABLE_FTS3_UNICODE */
 
-/************** End of fts3_unicode.c ****************************************/
-/************** Begin file fts3_unicode2.c ***********************************/
 /*
-** 2012 May 25
+** Arguments aIdx, aDistance and aSpare all point to arrays of size
+** nIdx. The aIdx array contains the set of integers from 0 to 
+** (nIdx-1) in no particular order. This function sorts the values
+** in aIdx according to the indexed values in aDistance. For
+** example, assuming the inputs:
 **
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
+**   aIdx      = { 0,   1,   2,   3 }
+**   aDistance = { 5.0, 2.0, 7.0, 6.0 }
 **
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
+** this function sets the aIdx array to contain:
 **
-******************************************************************************
+**   aIdx      = { 0,   1,   2,   3 }
+**
+** The aSpare array is used as temporary working space by the
+** sorting algorithm.
 */
+static void SortByDistance(
+  int *aIdx, 
+  int nIdx, 
+  RtreeDValue *aDistance, 
+  int *aSpare
+){
+  if( nIdx>1 ){
+    int iLeft = 0;
+    int iRight = 0;
 
-/*
-** DO NOT EDIT THIS MACHINE GENERATED FILE.
-*/
+    int nLeft = nIdx/2;
+    int nRight = nIdx-nLeft;
+    int *aLeft = aIdx;
+    int *aRight = &aIdx[nLeft];
 
-#ifndef SQLITE_DISABLE_FTS3_UNICODE
-#if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
+    SortByDistance(aLeft, nLeft, aDistance, aSpare);
+    SortByDistance(aRight, nRight, aDistance, aSpare);
 
-/* #include <assert.h> */
+    memcpy(aSpare, aLeft, sizeof(int)*nLeft);
+    aLeft = aSpare;
+
+    while( iLeft<nLeft || iRight<nRight ){
+      if( iLeft==nLeft ){
+        aIdx[iLeft+iRight] = aRight[iRight];
+        iRight++;
+      }else if( iRight==nRight ){
+        aIdx[iLeft+iRight] = aLeft[iLeft];
+        iLeft++;
+      }else{
+        RtreeDValue fLeft = aDistance[aLeft[iLeft]];
+        RtreeDValue fRight = aDistance[aRight[iRight]];
+        if( fLeft<fRight ){
+          aIdx[iLeft+iRight] = aLeft[iLeft];
+          iLeft++;
+        }else{
+          aIdx[iLeft+iRight] = aRight[iRight];
+          iRight++;
+        }
+      }
+    }
+
+#if 0
+    /* Check that the sort worked */
+    {
+      int jj;
+      for(jj=1; jj<nIdx; jj++){
+        RtreeDValue left = aDistance[aIdx[jj-1]];
+        RtreeDValue right = aDistance[aIdx[jj]];
+        assert( left<=right );
+      }
+    }
+#endif
+  }
+}
 
 /*
-** Return true if the argument corresponds to a unicode codepoint
-** classified as either a letter or a number. Otherwise false.
+** Arguments aIdx, aCell and aSpare all point to arrays of size
+** nIdx. The aIdx array contains the set of integers from 0 to 
+** (nIdx-1) in no particular order. This function sorts the values
+** in aIdx according to dimension iDim of the cells in aCell. The
+** minimum value of dimension iDim is considered first, the
+** maximum used to break ties.
 **
-** The results are undefined if the value passed to this function
-** is less than zero.
+** The aSpare array is used as temporary working space by the
+** sorting algorithm.
 */
-SQLITE_PRIVATE int sqlite3FtsUnicodeIsalnum(int c){
-  /* Each unsigned integer in the following array corresponds to a contiguous
-  ** range of unicode codepoints that are not either letters or numbers (i.e.
-  ** codepoints for which this function should return 0).
-  **
-  ** The most significant 22 bits in each 32-bit value contain the first 
-  ** codepoint in the range. The least significant 10 bits are used to store
-  ** the size of the range (always at least 1). In other words, the value 
-  ** ((C<<22) + N) represents a range of N codepoints starting with codepoint 
-  ** C. It is not possible to represent a range larger than 1023 codepoints 
-  ** using this format.
-  */
-  static const unsigned int aEntry[] = {
-    0x00000030, 0x0000E807, 0x00016C06, 0x0001EC2F, 0x0002AC07,
-    0x0002D001, 0x0002D803, 0x0002EC01, 0x0002FC01, 0x00035C01,
-    0x0003DC01, 0x000B0804, 0x000B480E, 0x000B9407, 0x000BB401,
-    0x000BBC81, 0x000DD401, 0x000DF801, 0x000E1002, 0x000E1C01,
-    0x000FD801, 0x00120808, 0x00156806, 0x00162402, 0x00163C01,
-    0x00164437, 0x0017CC02, 0x00180005, 0x00181816, 0x00187802,
-    0x00192C15, 0x0019A804, 0x0019C001, 0x001B5001, 0x001B580F,
-    0x001B9C07, 0x001BF402, 0x001C000E, 0x001C3C01, 0x001C4401,
-    0x001CC01B, 0x001E980B, 0x001FAC09, 0x001FD804, 0x00205804,
-    0x00206C09, 0x00209403, 0x0020A405, 0x0020C00F, 0x00216403,
-    0x00217801, 0x0023901B, 0x00240004, 0x0024E803, 0x0024F812,
-    0x00254407, 0x00258804, 0x0025C001, 0x00260403, 0x0026F001,
-    0x0026F807, 0x00271C02, 0x00272C03, 0x00275C01, 0x00278802,
-    0x0027C802, 0x0027E802, 0x00280403, 0x0028F001, 0x0028F805,
-    0x00291C02, 0x00292C03, 0x00294401, 0x0029C002, 0x0029D401,
-    0x002A0403, 0x002AF001, 0x002AF808, 0x002B1C03, 0x002B2C03,
-    0x002B8802, 0x002BC002, 0x002C0403, 0x002CF001, 0x002CF807,
-    0x002D1C02, 0x002D2C03, 0x002D5802, 0x002D8802, 0x002DC001,
-    0x002E0801, 0x002EF805, 0x002F1803, 0x002F2804, 0x002F5C01,
-    0x002FCC08, 0x00300403, 0x0030F807, 0x00311803, 0x00312804,
-    0x00315402, 0x00318802, 0x0031FC01, 0x00320802, 0x0032F001,
-    0x0032F807, 0x00331803, 0x00332804, 0x00335402, 0x00338802,
-    0x00340802, 0x0034F807, 0x00351803, 0x00352804, 0x00355C01,
-    0x00358802, 0x0035E401, 0x00360802, 0x00372801, 0x00373C06,
-    0x00375801, 0x00376008, 0x0037C803, 0x0038C401, 0x0038D007,
-    0x0038FC01, 0x00391C09, 0x00396802, 0x003AC401, 0x003AD006,
-    0x003AEC02, 0x003B2006, 0x003C041F, 0x003CD00C, 0x003DC417,
-    0x003E340B, 0x003E6424, 0x003EF80F, 0x003F380D, 0x0040AC14,
-    0x00412806, 0x00415804, 0x00417803, 0x00418803, 0x00419C07,
-    0x0041C404, 0x0042080C, 0x00423C01, 0x00426806, 0x0043EC01,
-    0x004D740C, 0x004E400A, 0x00500001, 0x0059B402, 0x005A0001,
-    0x005A6C02, 0x005BAC03, 0x005C4803, 0x005CC805, 0x005D4802,
-    0x005DC802, 0x005ED023, 0x005F6004, 0x005F7401, 0x0060000F,
-    0x0062A401, 0x0064800C, 0x0064C00C, 0x00650001, 0x00651002,
-    0x0066C011, 0x00672002, 0x00677822, 0x00685C05, 0x00687802,
-    0x0069540A, 0x0069801D, 0x0069FC01, 0x006A8007, 0x006AA006,
-    0x006C0005, 0x006CD011, 0x006D6823, 0x006E0003, 0x006E840D,
-    0x006F980E, 0x006FF004, 0x00709014, 0x0070EC05, 0x0071F802,
-    0x00730008, 0x00734019, 0x0073B401, 0x0073C803, 0x00770027,
-    0x0077F004, 0x007EF401, 0x007EFC03, 0x007F3403, 0x007F7403,
-    0x007FB403, 0x007FF402, 0x00800065, 0x0081A806, 0x0081E805,
-    0x00822805, 0x0082801A, 0x00834021, 0x00840002, 0x00840C04,
-    0x00842002, 0x00845001, 0x00845803, 0x00847806, 0x00849401,
-    0x00849C01, 0x0084A401, 0x0084B801, 0x0084E802, 0x00850005,
-    0x00852804, 0x00853C01, 0x00864264, 0x00900027, 0x0091000B,
-    0x0092704E, 0x00940200, 0x009C0475, 0x009E53B9, 0x00AD400A,
-    0x00B39406, 0x00B3BC03, 0x00B3E404, 0x00B3F802, 0x00B5C001,
-    0x00B5FC01, 0x00B7804F, 0x00B8C00C, 0x00BA001A, 0x00BA6C59,
-    0x00BC00D6, 0x00BFC00C, 0x00C00005, 0x00C02019, 0x00C0A807,
-    0x00C0D802, 0x00C0F403, 0x00C26404, 0x00C28001, 0x00C3EC01,
-    0x00C64002, 0x00C6580A, 0x00C70024, 0x00C8001F, 0x00C8A81E,
-    0x00C94001, 0x00C98020, 0x00CA2827, 0x00CB003F, 0x00CC0100,
-    0x01370040, 0x02924037, 0x0293F802, 0x02983403, 0x0299BC10,
-    0x029A7C01, 0x029BC008, 0x029C0017, 0x029C8002, 0x029E2402,
-    0x02A00801, 0x02A01801, 0x02A02C01, 0x02A08C09, 0x02A0D804,
-    0x02A1D004, 0x02A20002, 0x02A2D011, 0x02A33802, 0x02A38012,
-    0x02A3E003, 0x02A4980A, 0x02A51C0D, 0x02A57C01, 0x02A60004,
-    0x02A6CC1B, 0x02A77802, 0x02A8A40E, 0x02A90C01, 0x02A93002,
-    0x02A97004, 0x02A9DC03, 0x02A9EC01, 0x02AAC001, 0x02AAC803,
-    0x02AADC02, 0x02AAF802, 0x02AB0401, 0x02AB7802, 0x02ABAC07,
-    0x02ABD402, 0x02AF8C0B, 0x03600001, 0x036DFC02, 0x036FFC02,
-    0x037FFC01, 0x03EC7801, 0x03ECA401, 0x03EEC810, 0x03F4F802,
-    0x03F7F002, 0x03F8001A, 0x03F88007, 0x03F8C023, 0x03F95013,
-    0x03F9A004, 0x03FBFC01, 0x03FC040F, 0x03FC6807, 0x03FCEC06,
-    0x03FD6C0B, 0x03FF8007, 0x03FFA007, 0x03FFE405, 0x04040003,
-    0x0404DC09, 0x0405E411, 0x0406400C, 0x0407402E, 0x040E7C01,
-    0x040F4001, 0x04215C01, 0x04247C01, 0x0424FC01, 0x04280403,
-    0x04281402, 0x04283004, 0x0428E003, 0x0428FC01, 0x04294009,
-    0x0429FC01, 0x042CE407, 0x04400003, 0x0440E016, 0x04420003,
-    0x0442C012, 0x04440003, 0x04449C0E, 0x04450004, 0x04460003,
-    0x0446CC0E, 0x04471404, 0x045AAC0D, 0x0491C004, 0x05BD442E,
-    0x05BE3C04, 0x074000F6, 0x07440027, 0x0744A4B5, 0x07480046,
-    0x074C0057, 0x075B0401, 0x075B6C01, 0x075BEC01, 0x075C5401,
-    0x075CD401, 0x075D3C01, 0x075DBC01, 0x075E2401, 0x075EA401,
-    0x075F0C01, 0x07BBC002, 0x07C0002C, 0x07C0C064, 0x07C2800F,
-    0x07C2C40E, 0x07C3040F, 0x07C3440F, 0x07C4401F, 0x07C4C03C,
-    0x07C5C02B, 0x07C7981D, 0x07C8402B, 0x07C90009, 0x07C94002,
-    0x07CC0021, 0x07CCC006, 0x07CCDC46, 0x07CE0014, 0x07CE8025,
-    0x07CF1805, 0x07CF8011, 0x07D0003F, 0x07D10001, 0x07D108B6,
-    0x07D3E404, 0x07D4003E, 0x07D50004, 0x07D54018, 0x07D7EC46,
-    0x07D9140B, 0x07DA0046, 0x07DC0074, 0x38000401, 0x38008060,
-    0x380400F0,
-  };
-  static const unsigned int aAscii[4] = {
-    0xFFFFFFFF, 0xFC00FFFF, 0xF8000001, 0xF8000001,
-  };
+static void SortByDimension(
+  Rtree *pRtree,
+  int *aIdx, 
+  int nIdx, 
+  int iDim, 
+  RtreeCell *aCell, 
+  int *aSpare
+){
+  if( nIdx>1 ){
 
-  if( c<128 ){
-    return ( (aAscii[c >> 5] & (1 << (c & 0x001F)))==0 );
-  }else if( c<(1<<22) ){
-    unsigned int key = (((unsigned int)c)<<10) | 0x000003FF;
-    int iRes = 0;
-    int iHi = sizeof(aEntry)/sizeof(aEntry[0]) - 1;
-    int iLo = 0;
-    while( iHi>=iLo ){
-      int iTest = (iHi + iLo) / 2;
-      if( key >= aEntry[iTest] ){
-        iRes = iTest;
-        iLo = iTest+1;
+    int iLeft = 0;
+    int iRight = 0;
+
+    int nLeft = nIdx/2;
+    int nRight = nIdx-nLeft;
+    int *aLeft = aIdx;
+    int *aRight = &aIdx[nLeft];
+
+    SortByDimension(pRtree, aLeft, nLeft, iDim, aCell, aSpare);
+    SortByDimension(pRtree, aRight, nRight, iDim, aCell, aSpare);
+
+    memcpy(aSpare, aLeft, sizeof(int)*nLeft);
+    aLeft = aSpare;
+    while( iLeft<nLeft || iRight<nRight ){
+      RtreeDValue xleft1 = DCOORD(aCell[aLeft[iLeft]].aCoord[iDim*2]);
+      RtreeDValue xleft2 = DCOORD(aCell[aLeft[iLeft]].aCoord[iDim*2+1]);
+      RtreeDValue xright1 = DCOORD(aCell[aRight[iRight]].aCoord[iDim*2]);
+      RtreeDValue xright2 = DCOORD(aCell[aRight[iRight]].aCoord[iDim*2+1]);
+      if( (iLeft!=nLeft) && ((iRight==nRight)
+       || (xleft1<xright1)
+       || (xleft1==xright1 && xleft2<xright2)
+      )){
+        aIdx[iLeft+iRight] = aLeft[iLeft];
+        iLeft++;
       }else{
-        iHi = iTest-1;
+        aIdx[iLeft+iRight] = aRight[iRight];
+        iRight++;
       }
     }
-    assert( aEntry[0]<key );
-    assert( key>=aEntry[iRes] );
-    return (((unsigned int)c) >= ((aEntry[iRes]>>10) + (aEntry[iRes]&0x3FF)));
+
+#if 0
+    /* Check that the sort worked */
+    {
+      int jj;
+      for(jj=1; jj<nIdx; jj++){
+        RtreeDValue xleft1 = aCell[aIdx[jj-1]].aCoord[iDim*2];
+        RtreeDValue xleft2 = aCell[aIdx[jj-1]].aCoord[iDim*2+1];
+        RtreeDValue xright1 = aCell[aIdx[jj]].aCoord[iDim*2];
+        RtreeDValue xright2 = aCell[aIdx[jj]].aCoord[iDim*2+1];
+        assert( xleft1<=xright1 && (xleft1<xright1 || xleft2<=xright2) );
+      }
+    }
+#endif
   }
-  return 1;
 }
 
-
 /*
-** If the argument is a codepoint corresponding to a lowercase letter
-** in the ASCII range with a diacritic added, return the codepoint
-** of the ASCII letter only. For example, if passed 235 - "LATIN
-** SMALL LETTER E WITH DIAERESIS" - return 65 ("LATIN SMALL LETTER
-** E"). The resuls of passing a codepoint that corresponds to an
-** uppercase letter are undefined.
+** Implementation of the R*-tree variant of SplitNode from Beckman[1990].
 */
-static int remove_diacritic(int c){
-  unsigned short aDia[] = {
-        0,  1797,  1848,  1859,  1891,  1928,  1940,  1995, 
-     2024,  2040,  2060,  2110,  2168,  2206,  2264,  2286, 
-     2344,  2383,  2472,  2488,  2516,  2596,  2668,  2732, 
-     2782,  2842,  2894,  2954,  2984,  3000,  3028,  3336, 
-     3456,  3696,  3712,  3728,  3744,  3896,  3912,  3928, 
-     3968,  4008,  4040,  4106,  4138,  4170,  4202,  4234, 
-     4266,  4296,  4312,  4344,  4408,  4424,  4472,  4504, 
-     6148,  6198,  6264,  6280,  6360,  6429,  6505,  6529, 
-    61448, 61468, 61534, 61592, 61642, 61688, 61704, 61726, 
-    61784, 61800, 61836, 61880, 61914, 61948, 61998, 62122, 
-    62154, 62200, 62218, 62302, 62364, 62442, 62478, 62536, 
-    62554, 62584, 62604, 62640, 62648, 62656, 62664, 62730, 
-    62924, 63050, 63082, 63274, 63390, 
-  };
-  char aChar[] = {
-    '\0', 'a',  'c',  'e',  'i',  'n',  'o',  'u',  'y',  'y',  'a',  'c',  
-    'd',  'e',  'e',  'g',  'h',  'i',  'j',  'k',  'l',  'n',  'o',  'r',  
-    's',  't',  'u',  'u',  'w',  'y',  'z',  'o',  'u',  'a',  'i',  'o',  
-    'u',  'g',  'k',  'o',  'j',  'g',  'n',  'a',  'e',  'i',  'o',  'r',  
-    'u',  's',  't',  'h',  'a',  'e',  'o',  'y',  '\0', '\0', '\0', '\0', 
-    '\0', '\0', '\0', '\0', 'a',  'b',  'd',  'd',  'e',  'f',  'g',  'h',  
-    'h',  'i',  'k',  'l',  'l',  'm',  'n',  'p',  'r',  'r',  's',  't',  
-    'u',  'v',  'w',  'w',  'x',  'y',  'z',  'h',  't',  'w',  'y',  'a',  
-    'e',  'i',  'o',  'u',  'y',  
-  };
+static int splitNodeStartree(
+  Rtree *pRtree,
+  RtreeCell *aCell,
+  int nCell,
+  RtreeNode *pLeft,
+  RtreeNode *pRight,
+  RtreeCell *pBboxLeft,
+  RtreeCell *pBboxRight
+){
+  int **aaSorted;
+  int *aSpare;
+  int ii;
 
-  unsigned int key = (((unsigned int)c)<<3) | 0x00000007;
-  int iRes = 0;
-  int iHi = sizeof(aDia)/sizeof(aDia[0]) - 1;
-  int iLo = 0;
-  while( iHi>=iLo ){
-    int iTest = (iHi + iLo) / 2;
-    if( key >= aDia[iTest] ){
-      iRes = iTest;
-      iLo = iTest+1;
-    }else{
-      iHi = iTest-1;
+  int iBestDim = 0;
+  int iBestSplit = 0;
+  RtreeDValue fBestMargin = RTREE_ZERO;
+
+  int nByte = (pRtree->nDim+1)*(sizeof(int*)+nCell*sizeof(int));
+
+  aaSorted = (int **)sqlite3_malloc(nByte);
+  if( !aaSorted ){
+    return SQLITE_NOMEM;
+  }
+
+  aSpare = &((int *)&aaSorted[pRtree->nDim])[pRtree->nDim*nCell];
+  memset(aaSorted, 0, nByte);
+  for(ii=0; ii<pRtree->nDim; ii++){
+    int jj;
+    aaSorted[ii] = &((int *)&aaSorted[pRtree->nDim])[ii*nCell];
+    for(jj=0; jj<nCell; jj++){
+      aaSorted[ii][jj] = jj;
     }
+    SortByDimension(pRtree, aaSorted[ii], nCell, ii, aCell, aSpare);
   }
-  assert( key>=aDia[iRes] );
-  return ((c > (aDia[iRes]>>3) + (aDia[iRes]&0x07)) ? c : (int)aChar[iRes]);
+
+  for(ii=0; ii<pRtree->nDim; ii++){
+    RtreeDValue margin = RTREE_ZERO;
+    RtreeDValue fBestOverlap = RTREE_ZERO;
+    RtreeDValue fBestArea = RTREE_ZERO;
+    int iBestLeft = 0;
+    int nLeft;
+
+    for(
+      nLeft=RTREE_MINCELLS(pRtree); 
+      nLeft<=(nCell-RTREE_MINCELLS(pRtree)); 
+      nLeft++
+    ){
+      RtreeCell left;
+      RtreeCell right;
+      int kk;
+      RtreeDValue overlap;
+      RtreeDValue area;
+
+      memcpy(&left, &aCell[aaSorted[ii][0]], sizeof(RtreeCell));
+      memcpy(&right, &aCell[aaSorted[ii][nCell-1]], sizeof(RtreeCell));
+      for(kk=1; kk<(nCell-1); kk++){
+        if( kk<nLeft ){
+          cellUnion(pRtree, &left, &aCell[aaSorted[ii][kk]]);
+        }else{
+          cellUnion(pRtree, &right, &aCell[aaSorted[ii][kk]]);
+        }
+      }
+      margin += cellMargin(pRtree, &left);
+      margin += cellMargin(pRtree, &right);
+      overlap = cellOverlap(pRtree, &left, &right, 1);
+      area = cellArea(pRtree, &left) + cellArea(pRtree, &right);
+      if( (nLeft==RTREE_MINCELLS(pRtree))
+       || (overlap<fBestOverlap)
+       || (overlap==fBestOverlap && area<fBestArea)
+      ){
+        iBestLeft = nLeft;
+        fBestOverlap = overlap;
+        fBestArea = area;
+      }
+    }
+
+    if( ii==0 || margin<fBestMargin ){
+      iBestDim = ii;
+      fBestMargin = margin;
+      iBestSplit = iBestLeft;
+    }
+  }
+
+  memcpy(pBboxLeft, &aCell[aaSorted[iBestDim][0]], sizeof(RtreeCell));
+  memcpy(pBboxRight, &aCell[aaSorted[iBestDim][iBestSplit]], sizeof(RtreeCell));
+  for(ii=0; ii<nCell; ii++){
+    RtreeNode *pTarget = (ii<iBestSplit)?pLeft:pRight;
+    RtreeCell *pBbox = (ii<iBestSplit)?pBboxLeft:pBboxRight;
+    RtreeCell *pCell = &aCell[aaSorted[iBestDim][ii]];
+    nodeInsertCell(pRtree, pTarget, pCell);
+    cellUnion(pRtree, pBbox, pCell);
+  }
+
+  sqlite3_free(aaSorted);
+  return SQLITE_OK;
 }
 
 
-/*
-** Return true if the argument interpreted as a unicode codepoint
-** is a diacritical modifier character.
-*/
-SQLITE_PRIVATE int sqlite3FtsUnicodeIsdiacritic(int c){
-  unsigned int mask0 = 0x08029FDF;
-  unsigned int mask1 = 0x000361F8;
-  if( c<768 || c>817 ) return 0;
-  return (c < 768+32) ?
-      (mask0 & (1 << (c-768))) :
-      (mask1 & (1 << (c-768-32)));
+static int updateMapping(
+  Rtree *pRtree, 
+  i64 iRowid, 
+  RtreeNode *pNode, 
+  int iHeight
+){
+  int (*xSetMapping)(Rtree *, sqlite3_int64, sqlite3_int64);
+  xSetMapping = ((iHeight==0)?rowidWrite:parentWrite);
+  if( iHeight>0 ){
+    RtreeNode *pChild = nodeHashLookup(pRtree, iRowid);
+    if( pChild ){
+      nodeRelease(pRtree, pChild->pParent);
+      nodeReference(pNode);
+      pChild->pParent = pNode;
+    }
+  }
+  return xSetMapping(pRtree, iRowid, pNode->iNode);
 }
 
+static int SplitNode(
+  Rtree *pRtree,
+  RtreeNode *pNode,
+  RtreeCell *pCell,
+  int iHeight
+){
+  int i;
+  int newCellIsRight = 0;
 
-/*
-** Interpret the argument as a unicode codepoint. If the codepoint
-** is an upper case character that has a lower case equivalent,
-** return the codepoint corresponding to the lower case version.
-** Otherwise, return a copy of the argument.
-**
-** The results are undefined if the value passed to this function
-** is less than zero.
-*/
-SQLITE_PRIVATE int sqlite3FtsUnicodeFold(int c, int bRemoveDiacritic){
-  /* Each entry in the following array defines a rule for folding a range
-  ** of codepoints to lower case. The rule applies to a range of nRange
-  ** codepoints starting at codepoint iCode.
-  **
-  ** If the least significant bit in flags is clear, then the rule applies
-  ** to all nRange codepoints (i.e. all nRange codepoints are upper case and
-  ** need to be folded). Or, if it is set, then the rule only applies to
-  ** every second codepoint in the range, starting with codepoint C.
-  **
-  ** The 7 most significant bits in flags are an index into the aiOff[]
-  ** array. If a specific codepoint C does require folding, then its lower
-  ** case equivalent is ((C + aiOff[flags>>1]) & 0xFFFF).
-  **
-  ** The contents of this array are generated by parsing the CaseFolding.txt
-  ** file distributed as part of the "Unicode Character Database". See
-  ** http://www.unicode.org for details.
+  int rc = SQLITE_OK;
+  int nCell = NCELL(pNode);
+  RtreeCell *aCell;
+  int *aiUsed;
+
+  RtreeNode *pLeft = 0;
+  RtreeNode *pRight = 0;
+
+  RtreeCell leftbbox;
+  RtreeCell rightbbox;
+
+  /* Allocate an array and populate it with a copy of pCell and 
+  ** all cells from node pLeft. Then zero the original node.
   */
-  static const struct TableEntry {
-    unsigned short iCode;
-    unsigned char flags;
-    unsigned char nRange;
-  } aEntry[] = {
-    {65, 14, 26},          {181, 64, 1},          {192, 14, 23},
-    {216, 14, 7},          {256, 1, 48},          {306, 1, 6},
-    {313, 1, 16},          {330, 1, 46},          {376, 116, 1},
-    {377, 1, 6},           {383, 104, 1},         {385, 50, 1},
-    {386, 1, 4},           {390, 44, 1},          {391, 0, 1},
-    {393, 42, 2},          {395, 0, 1},           {398, 32, 1},
-    {399, 38, 1},          {400, 40, 1},          {401, 0, 1},
-    {403, 42, 1},          {404, 46, 1},          {406, 52, 1},
-    {407, 48, 1},          {408, 0, 1},           {412, 52, 1},
-    {413, 54, 1},          {415, 56, 1},          {416, 1, 6},
-    {422, 60, 1},          {423, 0, 1},           {425, 60, 1},
-    {428, 0, 1},           {430, 60, 1},          {431, 0, 1},
-    {433, 58, 2},          {435, 1, 4},           {439, 62, 1},
-    {440, 0, 1},           {444, 0, 1},           {452, 2, 1},
-    {453, 0, 1},           {455, 2, 1},           {456, 0, 1},
-    {458, 2, 1},           {459, 1, 18},          {478, 1, 18},
-    {497, 2, 1},           {498, 1, 4},           {502, 122, 1},
-    {503, 134, 1},         {504, 1, 40},          {544, 110, 1},
-    {546, 1, 18},          {570, 70, 1},          {571, 0, 1},
-    {573, 108, 1},         {574, 68, 1},          {577, 0, 1},
-    {579, 106, 1},         {580, 28, 1},          {581, 30, 1},
-    {582, 1, 10},          {837, 36, 1},          {880, 1, 4},
-    {886, 0, 1},           {902, 18, 1},          {904, 16, 3},
-    {908, 26, 1},          {910, 24, 2},          {913, 14, 17},
-    {931, 14, 9},          {962, 0, 1},           {975, 4, 1},
-    {976, 140, 1},         {977, 142, 1},         {981, 146, 1},
-    {982, 144, 1},         {984, 1, 24},          {1008, 136, 1},
-    {1009, 138, 1},        {1012, 130, 1},        {1013, 128, 1},
-    {1015, 0, 1},          {1017, 152, 1},        {1018, 0, 1},
-    {1021, 110, 3},        {1024, 34, 16},        {1040, 14, 32},
-    {1120, 1, 34},         {1162, 1, 54},         {1216, 6, 1},
-    {1217, 1, 14},         {1232, 1, 88},         {1329, 22, 38},
-    {4256, 66, 38},        {4295, 66, 1},         {4301, 66, 1},
-    {7680, 1, 150},        {7835, 132, 1},        {7838, 96, 1},
-    {7840, 1, 96},         {7944, 150, 8},        {7960, 150, 6},
-    {7976, 150, 8},        {7992, 150, 8},        {8008, 150, 6},
-    {8025, 151, 8},        {8040, 150, 8},        {8072, 150, 8},
-    {8088, 150, 8},        {8104, 150, 8},        {8120, 150, 2},
-    {8122, 126, 2},        {8124, 148, 1},        {8126, 100, 1},
-    {8136, 124, 4},        {8140, 148, 1},        {8152, 150, 2},
-    {8154, 120, 2},        {8168, 150, 2},        {8170, 118, 2},
-    {8172, 152, 1},        {8184, 112, 2},        {8186, 114, 2},
-    {8188, 148, 1},        {8486, 98, 1},         {8490, 92, 1},
-    {8491, 94, 1},         {8498, 12, 1},         {8544, 8, 16},
-    {8579, 0, 1},          {9398, 10, 26},        {11264, 22, 47},
-    {11360, 0, 1},         {11362, 88, 1},        {11363, 102, 1},
-    {11364, 90, 1},        {11367, 1, 6},         {11373, 84, 1},
-    {11374, 86, 1},        {11375, 80, 1},        {11376, 82, 1},
-    {11378, 0, 1},         {11381, 0, 1},         {11390, 78, 2},
-    {11392, 1, 100},       {11499, 1, 4},         {11506, 0, 1},
-    {42560, 1, 46},        {42624, 1, 24},        {42786, 1, 14},
-    {42802, 1, 62},        {42873, 1, 4},         {42877, 76, 1},
-    {42878, 1, 10},        {42891, 0, 1},         {42893, 74, 1},
-    {42896, 1, 4},         {42912, 1, 10},        {42922, 72, 1},
-    {65313, 14, 26},       
-  };
-  static const unsigned short aiOff[] = {
-   1,     2,     8,     15,    16,    26,    28,    32,    
-   37,    38,    40,    48,    63,    64,    69,    71,    
-   79,    80,    116,   202,   203,   205,   206,   207,   
-   209,   210,   211,   213,   214,   217,   218,   219,   
-   775,   7264,  10792, 10795, 23228, 23256, 30204, 54721, 
-   54753, 54754, 54756, 54787, 54793, 54809, 57153, 57274, 
-   57921, 58019, 58363, 61722, 65268, 65341, 65373, 65406, 
-   65408, 65410, 65415, 65424, 65436, 65439, 65450, 65462, 
-   65472, 65476, 65478, 65480, 65482, 65488, 65506, 65511, 
-   65514, 65521, 65527, 65528, 65529, 
-  };
+  aCell = sqlite3_malloc((sizeof(RtreeCell)+sizeof(int))*(nCell+1));
+  if( !aCell ){
+    rc = SQLITE_NOMEM;
+    goto splitnode_out;
+  }
+  aiUsed = (int *)&aCell[nCell+1];
+  memset(aiUsed, 0, sizeof(int)*(nCell+1));
+  for(i=0; i<nCell; i++){
+    nodeGetCell(pRtree, pNode, i, &aCell[i]);
+  }
+  nodeZero(pRtree, pNode);
+  memcpy(&aCell[nCell], pCell, sizeof(RtreeCell));
+  nCell++;
+
+  if( pNode->iNode==1 ){
+    pRight = nodeNew(pRtree, pNode);
+    pLeft = nodeNew(pRtree, pNode);
+    pRtree->iDepth++;
+    pNode->isDirty = 1;
+    writeInt16(pNode->zData, pRtree->iDepth);
+  }else{
+    pLeft = pNode;
+    pRight = nodeNew(pRtree, pLeft->pParent);
+    nodeReference(pLeft);
+  }
 
-  int ret = c;
+  if( !pLeft || !pRight ){
+    rc = SQLITE_NOMEM;
+    goto splitnode_out;
+  }
 
-  assert( c>=0 );
-  assert( sizeof(unsigned short)==2 && sizeof(unsigned char)==1 );
+  memset(pLeft->zData, 0, pRtree->iNodeSize);
+  memset(pRight->zData, 0, pRtree->iNodeSize);
 
-  if( c<128 ){
-    if( c>='A' && c<='Z' ) ret = c + ('a' - 'A');
-  }else if( c<65536 ){
-    int iHi = sizeof(aEntry)/sizeof(aEntry[0]) - 1;
-    int iLo = 0;
-    int iRes = -1;
+  rc = splitNodeStartree(pRtree, aCell, nCell, pLeft, pRight,
+                         &leftbbox, &rightbbox);
+  if( rc!=SQLITE_OK ){
+    goto splitnode_out;
+  }
 
-    while( iHi>=iLo ){
-      int iTest = (iHi + iLo) / 2;
-      int cmp = (c - aEntry[iTest].iCode);
-      if( cmp>=0 ){
-        iRes = iTest;
-        iLo = iTest+1;
-      }else{
-        iHi = iTest-1;
-      }
+  /* Ensure both child nodes have node numbers assigned to them by calling
+  ** nodeWrite(). Node pRight always needs a node number, as it was created
+  ** by nodeNew() above. But node pLeft sometimes already has a node number.
+  ** In this case avoid the all to nodeWrite().
+  */
+  if( SQLITE_OK!=(rc = nodeWrite(pRtree, pRight))
+   || (0==pLeft->iNode && SQLITE_OK!=(rc = nodeWrite(pRtree, pLeft)))
+  ){
+    goto splitnode_out;
+  }
+
+  rightbbox.iRowid = pRight->iNode;
+  leftbbox.iRowid = pLeft->iNode;
+
+  if( pNode->iNode==1 ){
+    rc = rtreeInsertCell(pRtree, pLeft->pParent, &leftbbox, iHeight+1);
+    if( rc!=SQLITE_OK ){
+      goto splitnode_out;
     }
-    assert( iRes<0 || c>=aEntry[iRes].iCode );
+  }else{
+    RtreeNode *pParent = pLeft->pParent;
+    int iCell;
+    rc = nodeParentIndex(pRtree, pLeft, &iCell);
+    if( rc==SQLITE_OK ){
+      nodeOverwriteCell(pRtree, pParent, &leftbbox, iCell);
+      rc = AdjustTree(pRtree, pParent, &leftbbox);
+    }
+    if( rc!=SQLITE_OK ){
+      goto splitnode_out;
+    }
+  }
+  if( (rc = rtreeInsertCell(pRtree, pRight->pParent, &rightbbox, iHeight+1)) ){
+    goto splitnode_out;
+  }
 
-    if( iRes>=0 ){
-      const struct TableEntry *p = &aEntry[iRes];
-      if( c<(p->iCode + p->nRange) && 0==(0x01 & p->flags & (p->iCode ^ c)) ){
-        ret = (c + (aiOff[p->flags>>1])) & 0x0000FFFF;
-        assert( ret>0 );
+  for(i=0; i<NCELL(pRight); i++){
+    i64 iRowid = nodeGetRowid(pRtree, pRight, i);
+    rc = updateMapping(pRtree, iRowid, pRight, iHeight);
+    if( iRowid==pCell->iRowid ){
+      newCellIsRight = 1;
+    }
+    if( rc!=SQLITE_OK ){
+      goto splitnode_out;
+    }
+  }
+  if( pNode->iNode==1 ){
+    for(i=0; i<NCELL(pLeft); i++){
+      i64 iRowid = nodeGetRowid(pRtree, pLeft, i);
+      rc = updateMapping(pRtree, iRowid, pLeft, iHeight);
+      if( rc!=SQLITE_OK ){
+        goto splitnode_out;
       }
     }
+  }else if( newCellIsRight==0 ){
+    rc = updateMapping(pRtree, pCell->iRowid, pLeft, iHeight);
+  }
 
-    if( bRemoveDiacritic ) ret = remove_diacritic(ret);
+  if( rc==SQLITE_OK ){
+    rc = nodeRelease(pRtree, pRight);
+    pRight = 0;
   }
-  
-  else if( c>=66560 && c<66600 ){
-    ret = c + 40;
+  if( rc==SQLITE_OK ){
+    rc = nodeRelease(pRtree, pLeft);
+    pLeft = 0;
   }
 
-  return ret;
+splitnode_out:
+  nodeRelease(pRtree, pRight);
+  nodeRelease(pRtree, pLeft);
+  sqlite3_free(aCell);
+  return rc;
 }
-#endif /* defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4) */
-#endif /* !defined(SQLITE_DISABLE_FTS3_UNICODE) */
 
-/************** End of fts3_unicode2.c ***************************************/
-/************** Begin file rtree.c *******************************************/
 /*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
+** If node pLeaf is not the root of the r-tree and its pParent pointer is 
+** still NULL, load all ancestor nodes of pLeaf into memory and populate
+** the pLeaf->pParent chain all the way up to the root node.
 **
-*************************************************************************
-** This file contains code for implementations of the r-tree and r*-tree
-** algorithms packaged as an SQLite virtual table module.
+** This operation is required when a row is deleted (or updated - an update
+** is implemented as a delete followed by an insert). SQLite provides the
+** rowid of the row to delete, which can be used to find the leaf on which
+** the entry resides (argument pLeaf). Once the leaf is located, this 
+** function is called to determine its ancestry.
 */
+static int fixLeafParent(Rtree *pRtree, RtreeNode *pLeaf){
+  int rc = SQLITE_OK;
+  RtreeNode *pChild = pLeaf;
+  while( rc==SQLITE_OK && pChild->iNode!=1 && pChild->pParent==0 ){
+    int rc2 = SQLITE_OK;          /* sqlite3_reset() return code */
+    sqlite3_bind_int64(pRtree->pReadParent, 1, pChild->iNode);
+    rc = sqlite3_step(pRtree->pReadParent);
+    if( rc==SQLITE_ROW ){
+      RtreeNode *pTest;           /* Used to test for reference loops */
+      i64 iNode;                  /* Node number of parent node */
 
-/*
-** Database Format of R-Tree Tables
-** --------------------------------
-**
-** The data structure for a single virtual r-tree table is stored in three 
-** native SQLite tables declared as follows. In each case, the '%' character
-** in the table name is replaced with the user-supplied name of the r-tree
-** table.
-**
-**   CREATE TABLE %_node(nodeno INTEGER PRIMARY KEY, data BLOB)
-**   CREATE TABLE %_parent(nodeno INTEGER PRIMARY KEY, parentnode INTEGER)
-**   CREATE TABLE %_rowid(rowid INTEGER PRIMARY KEY, nodeno INTEGER)
-**
-** The data for each node of the r-tree structure is stored in the %_node
-** table. For each node that is not the root node of the r-tree, there is
-** an entry in the %_parent table associating the node with its parent.
-** And for each row of data in the table, there is an entry in the %_rowid
-** table that maps from the entries rowid to the id of the node that it
-** is stored on.
-**
-** The root node of an r-tree always exists, even if the r-tree table is
-** empty. The nodeno of the root node is always 1. All other nodes in the
-** table must be the same size as the root node. The content of each node
-** is formatted as follows:
-**
-**   1. If the node is the root node (node 1), then the first 2 bytes
-**      of the node contain the tree depth as a big-endian integer.
-**      For non-root nodes, the first 2 bytes are left unused.
-**
-**   2. The next 2 bytes contain the number of entries currently 
-**      stored in the node.
-**
-**   3. The remainder of the node contains the node entries. Each entry
-**      consists of a single 8-byte integer followed by an even number
-**      of 4-byte coordinates. For leaf nodes the integer is the rowid
-**      of a record. For internal nodes it is the node number of a
-**      child page.
-*/
+      /* Before setting pChild->pParent, test that we are not creating a
+      ** loop of references (as we would if, say, pChild==pParent). We don't
+      ** want to do this as it leads to a memory leak when trying to delete
+      ** the referenced counted node structures.
+      */
+      iNode = sqlite3_column_int64(pRtree->pReadParent, 0);
+      for(pTest=pLeaf; pTest && pTest->iNode!=iNode; pTest=pTest->pParent);
+      if( !pTest ){
+        rc2 = nodeAcquire(pRtree, iNode, 0, &pChild->pParent);
+      }
+    }
+    rc = sqlite3_reset(pRtree->pReadParent);
+    if( rc==SQLITE_OK ) rc = rc2;
+    if( rc==SQLITE_OK && !pChild->pParent ) rc = SQLITE_CORRUPT_VTAB;
+    pChild = pChild->pParent;
+  }
+  return rc;
+}
 
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RTREE)
+static int deleteCell(Rtree *, RtreeNode *, int, int);
 
-#ifndef SQLITE_CORE
-  SQLITE_EXTENSION_INIT1
-#else
-#endif
+static int removeNode(Rtree *pRtree, RtreeNode *pNode, int iHeight){
+  int rc;
+  int rc2;
+  RtreeNode *pParent = 0;
+  int iCell;
 
-/* #include <string.h> */
-/* #include <assert.h> */
-/* #include <stdio.h> */
+  assert( pNode->nRef==1 );
 
-#ifndef SQLITE_AMALGAMATION
-#include "sqlite3rtree.h"
-typedef sqlite3_int64 i64;
-typedef unsigned char u8;
-typedef unsigned short u16;
-typedef unsigned int u32;
-#endif
+  /* Remove the entry in the parent cell. */
+  rc = nodeParentIndex(pRtree, pNode, &iCell);
+  if( rc==SQLITE_OK ){
+    pParent = pNode->pParent;
+    pNode->pParent = 0;
+    rc = deleteCell(pRtree, pParent, iCell, iHeight+1);
+  }
+  rc2 = nodeRelease(pRtree, pParent);
+  if( rc==SQLITE_OK ){
+    rc = rc2;
+  }
+  if( rc!=SQLITE_OK ){
+    return rc;
+  }
 
-/*  The following macro is used to suppress compiler warnings.
-*/
-#ifndef UNUSED_PARAMETER
-# define UNUSED_PARAMETER(x) (void)(x)
-#endif
+  /* Remove the xxx_node entry. */
+  sqlite3_bind_int64(pRtree->pDeleteNode, 1, pNode->iNode);
+  sqlite3_step(pRtree->pDeleteNode);
+  if( SQLITE_OK!=(rc = sqlite3_reset(pRtree->pDeleteNode)) ){
+    return rc;
+  }
 
-typedef struct Rtree Rtree;
-typedef struct RtreeCursor RtreeCursor;
-typedef struct RtreeNode RtreeNode;
-typedef struct RtreeCell RtreeCell;
-typedef struct RtreeConstraint RtreeConstraint;
-typedef struct RtreeMatchArg RtreeMatchArg;
-typedef struct RtreeGeomCallback RtreeGeomCallback;
-typedef union RtreeCoord RtreeCoord;
-typedef struct RtreeSearchPoint RtreeSearchPoint;
+  /* Remove the xxx_parent entry. */
+  sqlite3_bind_int64(pRtree->pDeleteParent, 1, pNode->iNode);
+  sqlite3_step(pRtree->pDeleteParent);
+  if( SQLITE_OK!=(rc = sqlite3_reset(pRtree->pDeleteParent)) ){
+    return rc;
+  }
+  
+  /* Remove the node from the in-memory hash table and link it into
+  ** the Rtree.pDeleted list. Its contents will be re-inserted later on.
+  */
+  nodeHashDelete(pRtree, pNode);
+  pNode->iNode = iHeight;
+  pNode->pNext = pRtree->pDeleted;
+  pNode->nRef++;
+  pRtree->pDeleted = pNode;
 
-/* The rtree may have between 1 and RTREE_MAX_DIMENSIONS dimensions. */
-#define RTREE_MAX_DIMENSIONS 5
+  return SQLITE_OK;
+}
 
-/* Size of hash table Rtree.aHash. This hash table is not expected to
-** ever contain very many entries, so a fixed number of buckets is 
-** used.
-*/
-#define HASHSIZE 97
+static int fixBoundingBox(Rtree *pRtree, RtreeNode *pNode){
+  RtreeNode *pParent = pNode->pParent;
+  int rc = SQLITE_OK; 
+  if( pParent ){
+    int ii; 
+    int nCell = NCELL(pNode);
+    RtreeCell box;                            /* Bounding box for pNode */
+    nodeGetCell(pRtree, pNode, 0, &box);
+    for(ii=1; ii<nCell; ii++){
+      RtreeCell cell;
+      nodeGetCell(pRtree, pNode, ii, &cell);
+      cellUnion(pRtree, &box, &cell);
+    }
+    box.iRowid = pNode->iNode;
+    rc = nodeParentIndex(pRtree, pNode, &ii);
+    if( rc==SQLITE_OK ){
+      nodeOverwriteCell(pRtree, pParent, &box, ii);
+      rc = fixBoundingBox(pRtree, pParent);
+    }
+  }
+  return rc;
+}
 
-/* The xBestIndex method of this virtual table requires an estimate of
-** the number of rows in the virtual table to calculate the costs of
-** various strategies. If possible, this estimate is loaded from the
-** sqlite_stat1 table (with RTREE_MIN_ROWEST as a hard-coded minimum).
-** Otherwise, if no sqlite_stat1 entry is available, use 
-** RTREE_DEFAULT_ROWEST.
+/*
+** Delete the cell at index iCell of node pNode. After removing the
+** cell, adjust the r-tree data structure if required.
 */
-#define RTREE_DEFAULT_ROWEST 1048576
-#define RTREE_MIN_ROWEST         100
+static int deleteCell(Rtree *pRtree, RtreeNode *pNode, int iCell, int iHeight){
+  RtreeNode *pParent;
+  int rc;
 
-/* 
-** An rtree virtual-table object.
-*/
-struct Rtree {
-  sqlite3_vtab base;          /* Base class.  Must be first */
-  sqlite3 *db;                /* Host database connection */
-  int iNodeSize;              /* Size in bytes of each node in the node table */
-  u8 nDim;                    /* Number of dimensions */
-  u8 eCoordType;              /* RTREE_COORD_REAL32 or RTREE_COORD_INT32 */
-  u8 nBytesPerCell;           /* Bytes consumed per cell */
-  int iDepth;                 /* Current depth of the r-tree structure */
-  char *zDb;                  /* Name of database containing r-tree table */
-  char *zName;                /* Name of r-tree table */ 
-  int nBusy;                  /* Current number of users of this structure */
-  i64 nRowEst;                /* Estimated number of rows in this table */
+  if( SQLITE_OK!=(rc = fixLeafParent(pRtree, pNode)) ){
+    return rc;
+  }
 
-  /* List of nodes removed during a CondenseTree operation. List is
-  ** linked together via the pointer normally used for hash chains -
-  ** RtreeNode.pNext. RtreeNode.iNode stores the depth of the sub-tree 
-  ** headed by the node (leaf nodes have RtreeNode.iNode==0).
+  /* Remove the cell from the node. This call just moves bytes around
+  ** the in-memory node image, so it cannot fail.
   */
-  RtreeNode *pDeleted;
-  int iReinsertHeight;        /* Height of sub-trees Reinsert() has run on */
+  nodeDeleteCell(pRtree, pNode, iCell);
 
-  /* Statements to read/write/delete a record from xxx_node */
-  sqlite3_stmt *pReadNode;
-  sqlite3_stmt *pWriteNode;
-  sqlite3_stmt *pDeleteNode;
+  /* If the node is not the tree root and now has less than the minimum
+  ** number of cells, remove it from the tree. Otherwise, update the
+  ** cell in the parent node so that it tightly contains the updated
+  ** node.
+  */
+  pParent = pNode->pParent;
+  assert( pParent || pNode->iNode==1 );
+  if( pParent ){
+    if( NCELL(pNode)<RTREE_MINCELLS(pRtree) ){
+      rc = removeNode(pRtree, pNode, iHeight);
+    }else{
+      rc = fixBoundingBox(pRtree, pNode);
+    }
+  }
 
-  /* Statements to read/write/delete a record from xxx_rowid */
-  sqlite3_stmt *pReadRowid;
-  sqlite3_stmt *pWriteRowid;
-  sqlite3_stmt *pDeleteRowid;
+  return rc;
+}
 
-  /* Statements to read/write/delete a record from xxx_parent */
-  sqlite3_stmt *pReadParent;
-  sqlite3_stmt *pWriteParent;
-  sqlite3_stmt *pDeleteParent;
+static int Reinsert(
+  Rtree *pRtree, 
+  RtreeNode *pNode, 
+  RtreeCell *pCell, 
+  int iHeight
+){
+  int *aOrder;
+  int *aSpare;
+  RtreeCell *aCell;
+  RtreeDValue *aDistance;
+  int nCell;
+  RtreeDValue aCenterCoord[RTREE_MAX_DIMENSIONS];
+  int iDim;
+  int ii;
+  int rc = SQLITE_OK;
+  int n;
 
-  RtreeNode *aHash[HASHSIZE]; /* Hash table of in-memory nodes. */ 
-};
+  memset(aCenterCoord, 0, sizeof(RtreeDValue)*RTREE_MAX_DIMENSIONS);
 
-/* Possible values for Rtree.eCoordType: */
-#define RTREE_COORD_REAL32 0
-#define RTREE_COORD_INT32  1
+  nCell = NCELL(pNode)+1;
+  n = (nCell+1)&(~1);
 
-/*
-** If SQLITE_RTREE_INT_ONLY is defined, then this virtual table will
-** only deal with integer coordinates.  No floating point operations
-** will be done.
-*/
-#ifdef SQLITE_RTREE_INT_ONLY
-  typedef sqlite3_int64 RtreeDValue;       /* High accuracy coordinate */
-  typedef int RtreeValue;                  /* Low accuracy coordinate */
-# define RTREE_ZERO 0
-#else
-  typedef double RtreeDValue;              /* High accuracy coordinate */
-  typedef float RtreeValue;                /* Low accuracy coordinate */
-# define RTREE_ZERO 0.0
-#endif
+  /* Allocate the buffers used by this operation. The allocation is
+  ** relinquished before this function returns.
+  */
+  aCell = (RtreeCell *)sqlite3_malloc(n * (
+    sizeof(RtreeCell)     +         /* aCell array */
+    sizeof(int)           +         /* aOrder array */
+    sizeof(int)           +         /* aSpare array */
+    sizeof(RtreeDValue)             /* aDistance array */
+  ));
+  if( !aCell ){
+    return SQLITE_NOMEM;
+  }
+  aOrder    = (int *)&aCell[n];
+  aSpare    = (int *)&aOrder[n];
+  aDistance = (RtreeDValue *)&aSpare[n];
 
-/*
-** When doing a search of an r-tree, instances of the following structure
-** record intermediate results from the tree walk.
-**
-** The id is always a node-id.  For iLevel>=1 the id is the node-id of
-** the node that the RtreeSearchPoint represents.  When iLevel==0, however,
-** the id is of the parent node and the cell that RtreeSearchPoint
-** represents is the iCell-th entry in the parent node.
-*/
-struct RtreeSearchPoint {
-  RtreeDValue rScore;    /* The score for this node.  Smallest goes first. */
-  sqlite3_int64 id;      /* Node ID */
-  u8 iLevel;             /* 0=entries.  1=leaf node.  2+ for higher */
-  u8 eWithin;            /* PARTLY_WITHIN or FULLY_WITHIN */
-  u8 iCell;              /* Cell index within the node */
-};
+  for(ii=0; ii<nCell; ii++){
+    if( ii==(nCell-1) ){
+      memcpy(&aCell[ii], pCell, sizeof(RtreeCell));
+    }else{
+      nodeGetCell(pRtree, pNode, ii, &aCell[ii]);
+    }
+    aOrder[ii] = ii;
+    for(iDim=0; iDim<pRtree->nDim; iDim++){
+      aCenterCoord[iDim] += DCOORD(aCell[ii].aCoord[iDim*2]);
+      aCenterCoord[iDim] += DCOORD(aCell[ii].aCoord[iDim*2+1]);
+    }
+  }
+  for(iDim=0; iDim<pRtree->nDim; iDim++){
+    aCenterCoord[iDim] = (aCenterCoord[iDim]/(nCell*(RtreeDValue)2));
+  }
 
-/*
-** The minimum number of cells allowed for a node is a third of the 
-** maximum. In Gutman's notation:
-**
-**     m = M/3
-**
-** If an R*-tree "Reinsert" operation is required, the same number of
-** cells are removed from the overfull node and reinserted into the tree.
-*/
-#define RTREE_MINCELLS(p) ((((p)->iNodeSize-4)/(p)->nBytesPerCell)/3)
-#define RTREE_REINSERT(p) RTREE_MINCELLS(p)
-#define RTREE_MAXCELLS 51
+  for(ii=0; ii<nCell; ii++){
+    aDistance[ii] = RTREE_ZERO;
+    for(iDim=0; iDim<pRtree->nDim; iDim++){
+      RtreeDValue coord = (DCOORD(aCell[ii].aCoord[iDim*2+1]) - 
+                               DCOORD(aCell[ii].aCoord[iDim*2]));
+      aDistance[ii] += (coord-aCenterCoord[iDim])*(coord-aCenterCoord[iDim]);
+    }
+  }
 
-/*
-** The smallest possible node-size is (512-64)==448 bytes. And the largest
-** supported cell size is 48 bytes (8 byte rowid + ten 4 byte coordinates).
-** Therefore all non-root nodes must contain at least 3 entries. Since 
-** 2^40 is greater than 2^64, an r-tree structure always has a depth of
-** 40 or less.
-*/
-#define RTREE_MAX_DEPTH 40
+  SortByDistance(aOrder, nCell, aDistance, aSpare);
+  nodeZero(pRtree, pNode);
+
+  for(ii=0; rc==SQLITE_OK && ii<(nCell-(RTREE_MINCELLS(pRtree)+1)); ii++){
+    RtreeCell *p = &aCell[aOrder[ii]];
+    nodeInsertCell(pRtree, pNode, p);
+    if( p->iRowid==pCell->iRowid ){
+      if( iHeight==0 ){
+        rc = rowidWrite(pRtree, p->iRowid, pNode->iNode);
+      }else{
+        rc = parentWrite(pRtree, p->iRowid, pNode->iNode);
+      }
+    }
+  }
+  if( rc==SQLITE_OK ){
+    rc = fixBoundingBox(pRtree, pNode);
+  }
+  for(; rc==SQLITE_OK && ii<nCell; ii++){
+    /* Find a node to store this cell in. pNode->iNode currently contains
+    ** the height of the sub-tree headed by the cell.
+    */
+    RtreeNode *pInsert;
+    RtreeCell *p = &aCell[aOrder[ii]];
+    rc = ChooseLeaf(pRtree, p, iHeight, &pInsert);
+    if( rc==SQLITE_OK ){
+      int rc2;
+      rc = rtreeInsertCell(pRtree, pInsert, p, iHeight);
+      rc2 = nodeRelease(pRtree, pInsert);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
 
+  sqlite3_free(aCell);
+  return rc;
+}
 
 /*
-** Number of entries in the cursor RtreeNode cache.  The first entry is
-** used to cache the RtreeNode for RtreeCursor.sPoint.  The remaining
-** entries cache the RtreeNode for the first elements of the priority queue.
+** Insert cell pCell into node pNode. Node pNode is the head of a 
+** subtree iHeight high (leaf nodes have iHeight==0).
 */
-#define RTREE_CACHE_SZ  5
+static int rtreeInsertCell(
+  Rtree *pRtree,
+  RtreeNode *pNode,
+  RtreeCell *pCell,
+  int iHeight
+){
+  int rc = SQLITE_OK;
+  if( iHeight>0 ){
+    RtreeNode *pChild = nodeHashLookup(pRtree, pCell->iRowid);
+    if( pChild ){
+      nodeRelease(pRtree, pChild->pParent);
+      nodeReference(pNode);
+      pChild->pParent = pNode;
+    }
+  }
+  if( nodeInsertCell(pRtree, pNode, pCell) ){
+    if( iHeight<=pRtree->iReinsertHeight || pNode->iNode==1){
+      rc = SplitNode(pRtree, pNode, pCell, iHeight);
+    }else{
+      pRtree->iReinsertHeight = iHeight;
+      rc = Reinsert(pRtree, pNode, pCell, iHeight);
+    }
+  }else{
+    rc = AdjustTree(pRtree, pNode, pCell);
+    if( rc==SQLITE_OK ){
+      if( iHeight==0 ){
+        rc = rowidWrite(pRtree, pCell->iRowid, pNode->iNode);
+      }else{
+        rc = parentWrite(pRtree, pCell->iRowid, pNode->iNode);
+      }
+    }
+  }
+  return rc;
+}
 
-/* 
-** An rtree cursor object.
-*/
-struct RtreeCursor {
-  sqlite3_vtab_cursor base;         /* Base class.  Must be first */
-  u8 atEOF;                         /* True if at end of search */
-  u8 bPoint;                        /* True if sPoint is valid */
-  int iStrategy;                    /* Copy of idxNum search parameter */
-  int nConstraint;                  /* Number of entries in aConstraint */
-  RtreeConstraint *aConstraint;     /* Search constraints. */
-  int nPointAlloc;                  /* Number of slots allocated for aPoint[] */
-  int nPoint;                       /* Number of slots used in aPoint[] */
-  int mxLevel;                      /* iLevel value for root of the tree */
-  RtreeSearchPoint *aPoint;         /* Priority queue for search points */
-  RtreeSearchPoint sPoint;          /* Cached next search point */
-  RtreeNode *aNode[RTREE_CACHE_SZ]; /* Rtree node cache */
-  u32 anQueue[RTREE_MAX_DEPTH+1];   /* Number of queued entries by iLevel */
-};
+static int reinsertNodeContent(Rtree *pRtree, RtreeNode *pNode){
+  int ii;
+  int rc = SQLITE_OK;
+  int nCell = NCELL(pNode);
 
-/* Return the Rtree of a RtreeCursor */
-#define RTREE_OF_CURSOR(X)   ((Rtree*)((X)->base.pVtab))
+  for(ii=0; rc==SQLITE_OK && ii<nCell; ii++){
+    RtreeNode *pInsert;
+    RtreeCell cell;
+    nodeGetCell(pRtree, pNode, ii, &cell);
 
-/*
-** A coordinate can be either a floating point number or a integer.  All
-** coordinates within a single R-Tree are always of the same time.
-*/
-union RtreeCoord {
-  RtreeValue f;      /* Floating point value */
-  int i;             /* Integer value */
-  u32 u;             /* Unsigned for byte-order conversions */
-};
+    /* Find a node to store this cell in. pNode->iNode currently contains
+    ** the height of the sub-tree headed by the cell.
+    */
+    rc = ChooseLeaf(pRtree, &cell, (int)pNode->iNode, &pInsert);
+    if( rc==SQLITE_OK ){
+      int rc2;
+      rc = rtreeInsertCell(pRtree, pInsert, &cell, (int)pNode->iNode);
+      rc2 = nodeRelease(pRtree, pInsert);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
+  }
+  return rc;
+}
 
 /*
-** The argument is an RtreeCoord. Return the value stored within the RtreeCoord
-** formatted as a RtreeDValue (double or int64). This macro assumes that local
-** variable pRtree points to the Rtree structure associated with the
-** RtreeCoord.
+** Select a currently unused rowid for a new r-tree record.
 */
-#ifdef SQLITE_RTREE_INT_ONLY
-# define DCOORD(coord) ((RtreeDValue)coord.i)
-#else
-# define DCOORD(coord) (                           \
-    (pRtree->eCoordType==RTREE_COORD_REAL32) ?      \
-      ((double)coord.f) :                           \
-      ((double)coord.i)                             \
-  )
-#endif
+static int newRowid(Rtree *pRtree, i64 *piRowid){
+  int rc;
+  sqlite3_bind_null(pRtree->pWriteRowid, 1);
+  sqlite3_bind_null(pRtree->pWriteRowid, 2);
+  sqlite3_step(pRtree->pWriteRowid);
+  rc = sqlite3_reset(pRtree->pWriteRowid);
+  *piRowid = sqlite3_last_insert_rowid(pRtree->db);
+  return rc;
+}
 
 /*
-** A search constraint.
+** Remove the entry with rowid=iDelete from the r-tree structure.
 */
-struct RtreeConstraint {
-  int iCoord;                     /* Index of constrained coordinate */
-  int op;                         /* Constraining operation */
-  union {
-    RtreeDValue rValue;             /* Constraint value. */
-    int (*xGeom)(sqlite3_rtree_geometry*,int,RtreeDValue*,int*);
-    int (*xQueryFunc)(sqlite3_rtree_query_info*);
-  } u;
-  sqlite3_rtree_query_info *pInfo;  /* xGeom and xQueryFunc argument */
-};
+static int rtreeDeleteRowid(Rtree *pRtree, sqlite3_int64 iDelete){
+  int rc;                         /* Return code */
+  RtreeNode *pLeaf = 0;           /* Leaf node containing record iDelete */
+  int iCell;                      /* Index of iDelete cell in pLeaf */
+  RtreeNode *pRoot;               /* Root node of rtree structure */
 
-/* Possible values for RtreeConstraint.op */
-#define RTREE_EQ    0x41  /* A */
-#define RTREE_LE    0x42  /* B */
-#define RTREE_LT    0x43  /* C */
-#define RTREE_GE    0x44  /* D */
-#define RTREE_GT    0x45  /* E */
-#define RTREE_MATCH 0x46  /* F: Old-style sqlite3_rtree_geometry_callback() */
-#define RTREE_QUERY 0x47  /* G: New-style sqlite3_rtree_query_callback() */
 
+  /* Obtain a reference to the root node to initialize Rtree.iDepth */
+  rc = nodeAcquire(pRtree, 1, 0, &pRoot);
 
-/* 
-** An rtree structure node.
-*/
-struct RtreeNode {
-  RtreeNode *pParent;         /* Parent node */
-  i64 iNode;                  /* The node number */
-  int nRef;                   /* Number of references to this node */
-  int isDirty;                /* True if the node needs to be written to disk */
-  u8 *zData;                  /* Content of the node, as should be on disk */
-  RtreeNode *pNext;           /* Next node in this hash collision chain */
-};
+  /* Obtain a reference to the leaf node that contains the entry 
+  ** about to be deleted. 
+  */
+  if( rc==SQLITE_OK ){
+    rc = findLeafNode(pRtree, iDelete, &pLeaf, 0);
+  }
 
-/* Return the number of cells in a node  */
-#define NCELL(pNode) readInt16(&(pNode)->zData[2])
+  /* Delete the cell in question from the leaf node. */
+  if( rc==SQLITE_OK ){
+    int rc2;
+    rc = nodeRowidIndex(pRtree, pLeaf, iDelete, &iCell);
+    if( rc==SQLITE_OK ){
+      rc = deleteCell(pRtree, pLeaf, iCell, 0);
+    }
+    rc2 = nodeRelease(pRtree, pLeaf);
+    if( rc==SQLITE_OK ){
+      rc = rc2;
+    }
+  }
 
-/* 
-** A single cell from a node, deserialized
-*/
-struct RtreeCell {
-  i64 iRowid;                                 /* Node or entry ID */
-  RtreeCoord aCoord[RTREE_MAX_DIMENSIONS*2];  /* Bounding box coordinates */
-};
+  /* Delete the corresponding entry in the <rtree>_rowid table. */
+  if( rc==SQLITE_OK ){
+    sqlite3_bind_int64(pRtree->pDeleteRowid, 1, iDelete);
+    sqlite3_step(pRtree->pDeleteRowid);
+    rc = sqlite3_reset(pRtree->pDeleteRowid);
+  }
 
+  /* Check if the root node now has exactly one child. If so, remove
+  ** it, schedule the contents of the child for reinsertion and 
+  ** reduce the tree height by one.
+  **
+  ** This is equivalent to copying the contents of the child into
+  ** the root node (the operation that Gutman's paper says to perform 
+  ** in this scenario).
+  */
+  if( rc==SQLITE_OK && pRtree->iDepth>0 && NCELL(pRoot)==1 ){
+    int rc2;
+    RtreeNode *pChild;
+    i64 iChild = nodeGetRowid(pRtree, pRoot, 0);
+    rc = nodeAcquire(pRtree, iChild, pRoot, &pChild);
+    if( rc==SQLITE_OK ){
+      rc = removeNode(pRtree, pChild, pRtree->iDepth-1);
+    }
+    rc2 = nodeRelease(pRtree, pChild);
+    if( rc==SQLITE_OK ) rc = rc2;
+    if( rc==SQLITE_OK ){
+      pRtree->iDepth--;
+      writeInt16(pRoot->zData, pRtree->iDepth);
+      pRoot->isDirty = 1;
+    }
+  }
 
-/*
-** This object becomes the sqlite3_user_data() for the SQL functions
-** that are created by sqlite3_rtree_geometry_callback() and
-** sqlite3_rtree_query_callback() and which appear on the right of MATCH
-** operators in order to constrain a search.
-**
-** xGeom and xQueryFunc are the callback functions.  Exactly one of 
-** xGeom and xQueryFunc fields is non-NULL, depending on whether the
-** SQL function was created using sqlite3_rtree_geometry_callback() or
-** sqlite3_rtree_query_callback().
-** 
-** This object is deleted automatically by the destructor mechanism in
-** sqlite3_create_function_v2().
-*/
-struct RtreeGeomCallback {
-  int (*xGeom)(sqlite3_rtree_geometry*, int, RtreeDValue*, int*);
-  int (*xQueryFunc)(sqlite3_rtree_query_info*);
-  void (*xDestructor)(void*);
-  void *pContext;
-};
+  /* Re-insert the contents of any underfull nodes removed from the tree. */
+  for(pLeaf=pRtree->pDeleted; pLeaf; pLeaf=pRtree->pDeleted){
+    if( rc==SQLITE_OK ){
+      rc = reinsertNodeContent(pRtree, pLeaf);
+    }
+    pRtree->pDeleted = pLeaf->pNext;
+    sqlite3_free(pLeaf);
+  }
 
+  /* Release the reference to the root node. */
+  if( rc==SQLITE_OK ){
+    rc = nodeRelease(pRtree, pRoot);
+  }else{
+    nodeRelease(pRtree, pRoot);
+  }
 
-/*
-** Value for the first field of every RtreeMatchArg object. The MATCH
-** operator tests that the first field of a blob operand matches this
-** value to avoid operating on invalid blobs (which could cause a segfault).
-*/
-#define RTREE_GEOMETRY_MAGIC 0x891245AB
+  return rc;
+}
 
 /*
-** An instance of this structure (in the form of a BLOB) is returned by
-** the SQL functions that sqlite3_rtree_geometry_callback() and
-** sqlite3_rtree_query_callback() create, and is read as the right-hand
-** operand to the MATCH operator of an R-Tree.
+** Rounding constants for float->double conversion.
 */
-struct RtreeMatchArg {
-  u32 magic;                  /* Always RTREE_GEOMETRY_MAGIC */
-  RtreeGeomCallback cb;       /* Info about the callback functions */
-  int nParam;                 /* Number of parameters to the SQL function */
-  RtreeDValue aParam[1];      /* Values for parameters to the SQL function */
-};
-
-#ifndef MAX
-# define MAX(x,y) ((x) < (y) ? (y) : (x))
-#endif
-#ifndef MIN
-# define MIN(x,y) ((x) > (y) ? (y) : (x))
-#endif
+#define RNDTOWARDS  (1.0 - 1.0/8388608.0)  /* Round towards zero */
+#define RNDAWAY     (1.0 + 1.0/8388608.0)  /* Round away from zero */
 
+#if !defined(SQLITE_RTREE_INT_ONLY)
 /*
-** Functions to deserialize a 16 bit integer, 32 bit real number and
-** 64 bit integer. The deserialized value is returned.
+** Convert an sqlite3_value into an RtreeValue (presumably a float)
+** while taking care to round toward negative or positive, respectively.
 */
-static int readInt16(u8 *p){
-  return (p[0]<<8) + p[1];
-}
-static void readCoord(u8 *p, RtreeCoord *pCoord){
-  pCoord->u = (
-    (((u32)p[0]) << 24) + 
-    (((u32)p[1]) << 16) + 
-    (((u32)p[2]) <<  8) + 
-    (((u32)p[3]) <<  0)
-  );
+static RtreeValue rtreeValueDown(sqlite3_value *v){
+  double d = sqlite3_value_double(v);
+  float f = (float)d;
+  if( f>d ){
+    f = (float)(d*(d<0 ? RNDAWAY : RNDTOWARDS));
+  }
+  return f;
 }
-static i64 readInt64(u8 *p){
-  return (
-    (((i64)p[0]) << 56) + 
-    (((i64)p[1]) << 48) + 
-    (((i64)p[2]) << 40) + 
-    (((i64)p[3]) << 32) + 
-    (((i64)p[4]) << 24) + 
-    (((i64)p[5]) << 16) + 
-    (((i64)p[6]) <<  8) + 
-    (((i64)p[7]) <<  0)
-  );
+static RtreeValue rtreeValueUp(sqlite3_value *v){
+  double d = sqlite3_value_double(v);
+  float f = (float)d;
+  if( f<d ){
+    f = (float)(d*(d<0 ? RNDTOWARDS : RNDAWAY));
+  }
+  return f;
 }
+#endif /* !defined(SQLITE_RTREE_INT_ONLY) */
 
-/*
-** Functions to serialize a 16 bit integer, 32 bit real number and
-** 64 bit integer. The value returned is the number of bytes written
-** to the argument buffer (always 2, 4 and 8 respectively).
-*/
-static int writeInt16(u8 *p, int i){
-  p[0] = (i>> 8)&0xFF;
-  p[1] = (i>> 0)&0xFF;
-  return 2;
-}
-static int writeCoord(u8 *p, RtreeCoord *pCoord){
-  u32 i;
-  assert( sizeof(RtreeCoord)==4 );
-  assert( sizeof(u32)==4 );
-  i = pCoord->u;
-  p[0] = (i>>24)&0xFF;
-  p[1] = (i>>16)&0xFF;
-  p[2] = (i>> 8)&0xFF;
-  p[3] = (i>> 0)&0xFF;
-  return 4;
-}
-static int writeInt64(u8 *p, i64 i){
-  p[0] = (i>>56)&0xFF;
-  p[1] = (i>>48)&0xFF;
-  p[2] = (i>>40)&0xFF;
-  p[3] = (i>>32)&0xFF;
-  p[4] = (i>>24)&0xFF;
-  p[5] = (i>>16)&0xFF;
-  p[6] = (i>> 8)&0xFF;
-  p[7] = (i>> 0)&0xFF;
-  return 8;
-}
 
 /*
-** Increment the reference count of node p.
+** The xUpdate method for rtree module virtual tables.
 */
-static void nodeReference(RtreeNode *p){
-  if( p ){
-    p->nRef++;
-  }
-}
+static int rtreeUpdate(
+  sqlite3_vtab *pVtab, 
+  int nData, 
+  sqlite3_value **azData, 
+  sqlite_int64 *pRowid
+){
+  Rtree *pRtree = (Rtree *)pVtab;
+  int rc = SQLITE_OK;
+  RtreeCell cell;                 /* New cell to insert if nData>1 */
+  int bHaveRowid = 0;             /* Set to 1 after new rowid is determined */
 
-/*
-** Clear the content of node p (set all bytes to 0x00).
-*/
-static void nodeZero(Rtree *pRtree, RtreeNode *p){
-  memset(&p->zData[2], 0, pRtree->iNodeSize-2);
-  p->isDirty = 1;
-}
+  rtreeReference(pRtree);
+  assert(nData>=1);
 
-/*
-** Given a node number iNode, return the corresponding key to use
-** in the Rtree.aHash table.
-*/
-static int nodeHash(i64 iNode){
-  return iNode % HASHSIZE;
-}
+  cell.iRowid = 0;  /* Used only to suppress a compiler warning */
 
-/*
-** Search the node hash table for node iNode. If found, return a pointer
-** to it. Otherwise, return 0.
-*/
-static RtreeNode *nodeHashLookup(Rtree *pRtree, i64 iNode){
-  RtreeNode *p;
-  for(p=pRtree->aHash[nodeHash(iNode)]; p && p->iNode!=iNode; p=p->pNext);
-  return p;
-}
+  /* Constraint handling. A write operation on an r-tree table may return
+  ** SQLITE_CONSTRAINT for two reasons:
+  **
+  **   1. A duplicate rowid value, or
+  **   2. The supplied data violates the "x2>=x1" constraint.
+  **
+  ** In the first case, if the conflict-handling mode is REPLACE, then
+  ** the conflicting row can be removed before proceeding. In the second
+  ** case, SQLITE_CONSTRAINT must be returned regardless of the
+  ** conflict-handling mode specified by the user.
+  */
+  if( nData>1 ){
+    int ii;
 
-/*
-** Add node pNode to the node hash table.
-*/
-static void nodeHashInsert(Rtree *pRtree, RtreeNode *pNode){
-  int iHash;
-  assert( pNode->pNext==0 );
-  iHash = nodeHash(pNode->iNode);
-  pNode->pNext = pRtree->aHash[iHash];
-  pRtree->aHash[iHash] = pNode;
-}
+    /* Populate the cell.aCoord[] array. The first coordinate is azData[3].
+    **
+    ** NB: nData can only be less than nDim*2+3 if the rtree is mis-declared
+    ** with "column" that are interpreted as table constraints.
+    ** Example:  CREATE VIRTUAL TABLE bad USING rtree(x,y,CHECK(y>5));
+    ** This problem was discovered after years of use, so we silently ignore
+    ** these kinds of misdeclared tables to avoid breaking any legacy.
+    */
+    assert( nData<=(pRtree->nDim*2 + 3) );
 
-/*
-** Remove node pNode from the node hash table.
-*/
-static void nodeHashDelete(Rtree *pRtree, RtreeNode *pNode){
-  RtreeNode **pp;
-  if( pNode->iNode!=0 ){
-    pp = &pRtree->aHash[nodeHash(pNode->iNode)];
-    for( ; (*pp)!=pNode; pp = &(*pp)->pNext){ assert(*pp); }
-    *pp = pNode->pNext;
-    pNode->pNext = 0;
+#ifndef SQLITE_RTREE_INT_ONLY
+    if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
+      for(ii=0; ii<nData-4; ii+=2){
+        cell.aCoord[ii].f = rtreeValueDown(azData[ii+3]);
+        cell.aCoord[ii+1].f = rtreeValueUp(azData[ii+4]);
+        if( cell.aCoord[ii].f>cell.aCoord[ii+1].f ){
+          rc = SQLITE_CONSTRAINT;
+          goto constraint;
+        }
+      }
+    }else
+#endif
+    {
+      for(ii=0; ii<nData-4; ii+=2){
+        cell.aCoord[ii].i = sqlite3_value_int(azData[ii+3]);
+        cell.aCoord[ii+1].i = sqlite3_value_int(azData[ii+4]);
+        if( cell.aCoord[ii].i>cell.aCoord[ii+1].i ){
+          rc = SQLITE_CONSTRAINT;
+          goto constraint;
+        }
+      }
+    }
+
+    /* If a rowid value was supplied, check if it is already present in 
+    ** the table. If so, the constraint has failed. */
+    if( sqlite3_value_type(azData[2])!=SQLITE_NULL ){
+      cell.iRowid = sqlite3_value_int64(azData[2]);
+      if( sqlite3_value_type(azData[0])==SQLITE_NULL
+       || sqlite3_value_int64(azData[0])!=cell.iRowid
+      ){
+        int steprc;
+        sqlite3_bind_int64(pRtree->pReadRowid, 1, cell.iRowid);
+        steprc = sqlite3_step(pRtree->pReadRowid);
+        rc = sqlite3_reset(pRtree->pReadRowid);
+        if( SQLITE_ROW==steprc ){
+          if( sqlite3_vtab_on_conflict(pRtree->db)==SQLITE_REPLACE ){
+            rc = rtreeDeleteRowid(pRtree, cell.iRowid);
+          }else{
+            rc = SQLITE_CONSTRAINT;
+            goto constraint;
+          }
+        }
+      }
+      bHaveRowid = 1;
+    }
+  }
+
+  /* If azData[0] is not an SQL NULL value, it is the rowid of a
+  ** record to delete from the r-tree table. The following block does
+  ** just that.
+  */
+  if( sqlite3_value_type(azData[0])!=SQLITE_NULL ){
+    rc = rtreeDeleteRowid(pRtree, sqlite3_value_int64(azData[0]));
+  }
+
+  /* If the azData[] array contains more than one element, elements
+  ** (azData[2]..azData[argc-1]) contain a new record to insert into
+  ** the r-tree structure.
+  */
+  if( rc==SQLITE_OK && nData>1 ){
+    /* Insert the new record into the r-tree */
+    RtreeNode *pLeaf = 0;
+
+    /* Figure out the rowid of the new row. */
+    if( bHaveRowid==0 ){
+      rc = newRowid(pRtree, &cell.iRowid);
+    }
+    *pRowid = cell.iRowid;
+
+    if( rc==SQLITE_OK ){
+      rc = ChooseLeaf(pRtree, &cell, 0, &pLeaf);
+    }
+    if( rc==SQLITE_OK ){
+      int rc2;
+      pRtree->iReinsertHeight = -1;
+      rc = rtreeInsertCell(pRtree, pLeaf, &cell, 0);
+      rc2 = nodeRelease(pRtree, pLeaf);
+      if( rc==SQLITE_OK ){
+        rc = rc2;
+      }
+    }
   }
+
+constraint:
+  rtreeRelease(pRtree);
+  return rc;
 }
 
 /*
-** Allocate and return new r-tree node. Initially, (RtreeNode.iNode==0),
-** indicating that node has not yet been assigned a node number. It is
-** assigned a node number when nodeWrite() is called to write the
-** node contents out to the database.
+** The xRename method for rtree module virtual tables.
 */
-static RtreeNode *nodeNew(Rtree *pRtree, RtreeNode *pParent){
-  RtreeNode *pNode;
-  pNode = (RtreeNode *)sqlite3_malloc(sizeof(RtreeNode) + pRtree->iNodeSize);
-  if( pNode ){
-    memset(pNode, 0, sizeof(RtreeNode) + pRtree->iNodeSize);
-    pNode->zData = (u8 *)&pNode[1];
-    pNode->nRef = 1;
-    pNode->pParent = pParent;
-    pNode->isDirty = 1;
-    nodeReference(pParent);
+static int rtreeRename(sqlite3_vtab *pVtab, const char *zNewName){
+  Rtree *pRtree = (Rtree *)pVtab;
+  int rc = SQLITE_NOMEM;
+  char *zSql = sqlite3_mprintf(
+    "ALTER TABLE %Q.'%q_node'   RENAME TO \"%w_node\";"
+    "ALTER TABLE %Q.'%q_parent' RENAME TO \"%w_parent\";"
+    "ALTER TABLE %Q.'%q_rowid'  RENAME TO \"%w_rowid\";"
+    , pRtree->zDb, pRtree->zName, zNewName 
+    , pRtree->zDb, pRtree->zName, zNewName 
+    , pRtree->zDb, pRtree->zName, zNewName
+  );
+  if( zSql ){
+    rc = sqlite3_exec(pRtree->db, zSql, 0, 0, 0);
+    sqlite3_free(zSql);
   }
-  return pNode;
+  return rc;
 }
 
 /*
-** Obtain a reference to an r-tree node.
+** This function populates the pRtree->nRowEst variable with an estimate
+** of the number of rows in the virtual table. If possible, this is based
+** on sqlite_stat1 data. Otherwise, use RTREE_DEFAULT_ROWEST.
 */
-static int nodeAcquire(
-  Rtree *pRtree,             /* R-tree structure */
-  i64 iNode,                 /* Node number to load */
-  RtreeNode *pParent,        /* Either the parent node or NULL */
-  RtreeNode **ppNode         /* OUT: Acquired node */
-){
+static int rtreeQueryStat1(sqlite3 *db, Rtree *pRtree){
+  const char *zFmt = "SELECT stat FROM %Q.sqlite_stat1 WHERE tbl = '%q_rowid'";
+  char *zSql;
+  sqlite3_stmt *p;
   int rc;
-  int rc2 = SQLITE_OK;
-  RtreeNode *pNode;
+  i64 nRow = 0;
 
-  /* Check if the requested node is already in the hash table. If so,
-  ** increase its reference count and return it.
-  */
-  if( (pNode = nodeHashLookup(pRtree, iNode)) ){
-    assert( !pParent || !pNode->pParent || pNode->pParent==pParent );
-    if( pParent && !pNode->pParent ){
-      nodeReference(pParent);
-      pNode->pParent = pParent;
+  zSql = sqlite3_mprintf(zFmt, pRtree->zDb, pRtree->zName);
+  if( zSql==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    rc = sqlite3_prepare_v2(db, zSql, -1, &p, 0);
+    if( rc==SQLITE_OK ){
+      if( sqlite3_step(p)==SQLITE_ROW ) nRow = sqlite3_column_int64(p, 0);
+      rc = sqlite3_finalize(p);
+    }else if( rc!=SQLITE_NOMEM ){
+      rc = SQLITE_OK;
     }
-    pNode->nRef++;
-    *ppNode = pNode;
-    return SQLITE_OK;
-  }
 
-  sqlite3_bind_int64(pRtree->pReadNode, 1, iNode);
-  rc = sqlite3_step(pRtree->pReadNode);
-  if( rc==SQLITE_ROW ){
-    const u8 *zBlob = sqlite3_column_blob(pRtree->pReadNode, 0);
-    if( pRtree->iNodeSize==sqlite3_column_bytes(pRtree->pReadNode, 0) ){
-      pNode = (RtreeNode *)sqlite3_malloc(sizeof(RtreeNode)+pRtree->iNodeSize);
-      if( !pNode ){
-        rc2 = SQLITE_NOMEM;
+    if( rc==SQLITE_OK ){
+      if( nRow==0 ){
+        pRtree->nRowEst = RTREE_DEFAULT_ROWEST;
       }else{
-        pNode->pParent = pParent;
-        pNode->zData = (u8 *)&pNode[1];
-        pNode->nRef = 1;
-        pNode->iNode = iNode;
-        pNode->isDirty = 0;
-        pNode->pNext = 0;
-        memcpy(pNode->zData, zBlob, pRtree->iNodeSize);
-        nodeReference(pParent);
+        pRtree->nRowEst = MAX(nRow, RTREE_MIN_ROWEST);
       }
     }
+    sqlite3_free(zSql);
   }
-  rc = sqlite3_reset(pRtree->pReadNode);
-  if( rc==SQLITE_OK ) rc = rc2;
 
-  /* If the root node was just loaded, set pRtree->iDepth to the height
-  ** of the r-tree structure. A height of zero means all data is stored on
-  ** the root node. A height of one means the children of the root node
-  ** are the leaves, and so on. If the depth as specified on the root node
-  ** is greater than RTREE_MAX_DEPTH, the r-tree structure must be corrupt.
-  */
-  if( pNode && iNode==1 ){
-    pRtree->iDepth = readInt16(pNode->zData);
-    if( pRtree->iDepth>RTREE_MAX_DEPTH ){
-      rc = SQLITE_CORRUPT_VTAB;
-    }
-  }
+  return rc;
+}
 
-  /* If no error has occurred so far, check if the "number of entries"
-  ** field on the node is too large. If so, set the return code to 
-  ** SQLITE_CORRUPT_VTAB.
-  */
-  if( pNode && rc==SQLITE_OK ){
-    if( NCELL(pNode)>((pRtree->iNodeSize-4)/pRtree->nBytesPerCell) ){
-      rc = SQLITE_CORRUPT_VTAB;
+static sqlite3_module rtreeModule = {
+  0,                          /* iVersion */
+  rtreeCreate,                /* xCreate - create a table */
+  rtreeConnect,               /* xConnect - connect to an existing table */
+  rtreeBestIndex,             /* xBestIndex - Determine search strategy */
+  rtreeDisconnect,            /* xDisconnect - Disconnect from a table */
+  rtreeDestroy,               /* xDestroy - Drop a table */
+  rtreeOpen,                  /* xOpen - open a cursor */
+  rtreeClose,                 /* xClose - close a cursor */
+  rtreeFilter,                /* xFilter - configure scan constraints */
+  rtreeNext,                  /* xNext - advance a cursor */
+  rtreeEof,                   /* xEof */
+  rtreeColumn,                /* xColumn - read data */
+  rtreeRowid,                 /* xRowid - read data */
+  rtreeUpdate,                /* xUpdate - write data */
+  0,                          /* xBegin - begin transaction */
+  0,                          /* xSync - sync transaction */
+  0,                          /* xCommit - commit transaction */
+  0,                          /* xRollback - rollback transaction */
+  0,                          /* xFindFunction - function overloading */
+  rtreeRename,                /* xRename - rename the table */
+  0,                          /* xSavepoint */
+  0,                          /* xRelease */
+  0                           /* xRollbackTo */
+};
+
+static int rtreeSqlInit(
+  Rtree *pRtree, 
+  sqlite3 *db, 
+  const char *zDb, 
+  const char *zPrefix, 
+  int isCreate
+){
+  int rc = SQLITE_OK;
+
+  #define N_STATEMENT 9
+  static const char *azSql[N_STATEMENT] = {
+    /* Read and write the xxx_node table */
+    "SELECT data FROM '%q'.'%q_node' WHERE nodeno = :1",
+    "INSERT OR REPLACE INTO '%q'.'%q_node' VALUES(:1, :2)",
+    "DELETE FROM '%q'.'%q_node' WHERE nodeno = :1",
+
+    /* Read and write the xxx_rowid table */
+    "SELECT nodeno FROM '%q'.'%q_rowid' WHERE rowid = :1",
+    "INSERT OR REPLACE INTO '%q'.'%q_rowid' VALUES(:1, :2)",
+    "DELETE FROM '%q'.'%q_rowid' WHERE rowid = :1",
+
+    /* Read and write the xxx_parent table */
+    "SELECT parentnode FROM '%q'.'%q_parent' WHERE nodeno = :1",
+    "INSERT OR REPLACE INTO '%q'.'%q_parent' VALUES(:1, :2)",
+    "DELETE FROM '%q'.'%q_parent' WHERE nodeno = :1"
+  };
+  sqlite3_stmt **appStmt[N_STATEMENT];
+  int i;
+
+  pRtree->db = db;
+
+  if( isCreate ){
+    char *zCreate = sqlite3_mprintf(
+"CREATE TABLE \"%w\".\"%w_node\"(nodeno INTEGER PRIMARY KEY, data BLOB);"
+"CREATE TABLE \"%w\".\"%w_rowid\"(rowid INTEGER PRIMARY KEY, nodeno INTEGER);"
+"CREATE TABLE \"%w\".\"%w_parent\"(nodeno INTEGER PRIMARY KEY,"
+                                  " parentnode INTEGER);"
+"INSERT INTO '%q'.'%q_node' VALUES(1, zeroblob(%d))",
+      zDb, zPrefix, zDb, zPrefix, zDb, zPrefix, zDb, zPrefix, pRtree->iNodeSize
+    );
+    if( !zCreate ){
+      return SQLITE_NOMEM;
+    }
+    rc = sqlite3_exec(db, zCreate, 0, 0, 0);
+    sqlite3_free(zCreate);
+    if( rc!=SQLITE_OK ){
+      return rc;
     }
   }
 
-  if( rc==SQLITE_OK ){
-    if( pNode!=0 ){
-      nodeHashInsert(pRtree, pNode);
+  appStmt[0] = &pRtree->pReadNode;
+  appStmt[1] = &pRtree->pWriteNode;
+  appStmt[2] = &pRtree->pDeleteNode;
+  appStmt[3] = &pRtree->pReadRowid;
+  appStmt[4] = &pRtree->pWriteRowid;
+  appStmt[5] = &pRtree->pDeleteRowid;
+  appStmt[6] = &pRtree->pReadParent;
+  appStmt[7] = &pRtree->pWriteParent;
+  appStmt[8] = &pRtree->pDeleteParent;
+
+  rc = rtreeQueryStat1(db, pRtree);
+  for(i=0; i<N_STATEMENT && rc==SQLITE_OK; i++){
+    char *zSql = sqlite3_mprintf(azSql[i], zDb, zPrefix);
+    if( zSql ){
+      rc = sqlite3_prepare_v2(db, zSql, -1, appStmt[i], 0); 
     }else{
-      rc = SQLITE_CORRUPT_VTAB;
+      rc = SQLITE_NOMEM;
     }
-    *ppNode = pNode;
-  }else{
-    sqlite3_free(pNode);
-    *ppNode = 0;
+    sqlite3_free(zSql);
   }
 
   return rc;
 }
 
 /*
-** Overwrite cell iCell of node pNode with the contents of pCell.
+** The second argument to this function contains the text of an SQL statement
+** that returns a single integer value. The statement is compiled and executed
+** using database connection db. If successful, the integer value returned
+** is written to *piVal and SQLITE_OK returned. Otherwise, an SQLite error
+** code is returned and the value of *piVal after returning is not defined.
 */
-static void nodeOverwriteCell(
-  Rtree *pRtree,             /* The overall R-Tree */
-  RtreeNode *pNode,          /* The node into which the cell is to be written */
-  RtreeCell *pCell,          /* The cell to write */
-  int iCell                  /* Index into pNode into which pCell is written */
-){
-  int ii;
-  u8 *p = &pNode->zData[4 + pRtree->nBytesPerCell*iCell];
-  p += writeInt64(p, pCell->iRowid);
-  for(ii=0; ii<(pRtree->nDim*2); ii++){
-    p += writeCoord(p, &pCell->aCoord[ii]);
+static int getIntFromStmt(sqlite3 *db, const char *zSql, int *piVal){
+  int rc = SQLITE_NOMEM;
+  if( zSql ){
+    sqlite3_stmt *pStmt = 0;
+    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+    if( rc==SQLITE_OK ){
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        *piVal = sqlite3_column_int(pStmt, 0);
+      }
+      rc = sqlite3_finalize(pStmt);
+    }
   }
-  pNode->isDirty = 1;
+  return rc;
 }
 
 /*
-** Remove the cell with index iCell from node pNode.
+** This function is called from within the xConnect() or xCreate() method to
+** determine the node-size used by the rtree table being created or connected
+** to. If successful, pRtree->iNodeSize is populated and SQLITE_OK returned.
+** Otherwise, an SQLite error code is returned.
+**
+** If this function is being called as part of an xConnect(), then the rtree
+** table already exists. In this case the node-size is determined by inspecting
+** the root node of the tree.
+**
+** Otherwise, for an xCreate(), use 64 bytes less than the database page-size. 
+** This ensures that each node is stored on a single database page. If the 
+** database page-size is so large that more than RTREE_MAXCELLS entries 
+** would fit in a single node, use a smaller node-size.
 */
-static void nodeDeleteCell(Rtree *pRtree, RtreeNode *pNode, int iCell){
-  u8 *pDst = &pNode->zData[4 + pRtree->nBytesPerCell*iCell];
-  u8 *pSrc = &pDst[pRtree->nBytesPerCell];
-  int nByte = (NCELL(pNode) - iCell - 1) * pRtree->nBytesPerCell;
-  memmove(pDst, pSrc, nByte);
-  writeInt16(&pNode->zData[2], NCELL(pNode)-1);
-  pNode->isDirty = 1;
+static int getNodeSize(
+  sqlite3 *db,                    /* Database handle */
+  Rtree *pRtree,                  /* Rtree handle */
+  int isCreate,                   /* True for xCreate, false for xConnect */
+  char **pzErr                    /* OUT: Error message, if any */
+){
+  int rc;
+  char *zSql;
+  if( isCreate ){
+    int iPageSize = 0;
+    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
+    rc = getIntFromStmt(db, zSql, &iPageSize);
+    if( rc==SQLITE_OK ){
+      pRtree->iNodeSize = iPageSize-64;
+      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
+        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
+      }
+    }else{
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
+  }else{
+    zSql = sqlite3_mprintf(
+        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
+        pRtree->zDb, pRtree->zName
+    );
+    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
+    if( rc!=SQLITE_OK ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
+  }
+
+  sqlite3_free(zSql);
+  return rc;
 }
 
-/*
-** Insert the contents of cell pCell into node pNode. If the insert
-** is successful, return SQLITE_OK.
+/* 
+** This function is the implementation of both the xConnect and xCreate
+** methods of the r-tree virtual table.
 **
-** If there is not enough free space in pNode, return SQLITE_FULL.
+**   argv[0]   -> module name
+**   argv[1]   -> database name
+**   argv[2]   -> table name
+**   argv[...] -> column names...
 */
-static int nodeInsertCell(
-  Rtree *pRtree,                /* The overall R-Tree */
-  RtreeNode *pNode,             /* Write new cell into this node */
-  RtreeCell *pCell              /* The cell to be inserted */
+static int rtreeInit(
+  sqlite3 *db,                        /* Database connection */
+  void *pAux,                         /* One of the RTREE_COORD_* constants */
+  int argc, const char *const*argv,   /* Parameters to CREATE TABLE statement */
+  sqlite3_vtab **ppVtab,              /* OUT: New virtual table */
+  char **pzErr,                       /* OUT: Error message, if any */
+  int isCreate                        /* True for xCreate, false for xConnect */
 ){
-  int nCell;                    /* Current number of cells in pNode */
-  int nMaxCell;                 /* Maximum number of cells for pNode */
+  int rc = SQLITE_OK;
+  Rtree *pRtree;
+  int nDb;              /* Length of string argv[1] */
+  int nName;            /* Length of string argv[2] */
+  int eCoordType = (pAux ? RTREE_COORD_INT32 : RTREE_COORD_REAL32);
 
-  nMaxCell = (pRtree->iNodeSize-4)/pRtree->nBytesPerCell;
-  nCell = NCELL(pNode);
+  const char *aErrMsg[] = {
+    0,                                                    /* 0 */
+    "Wrong number of columns for an rtree table",         /* 1 */
+    "Too few columns for an rtree table",                 /* 2 */
+    "Too many columns for an rtree table"                 /* 3 */
+  };
 
-  assert( nCell<=nMaxCell );
-  if( nCell<nMaxCell ){
-    nodeOverwriteCell(pRtree, pNode, pCell, nCell);
-    writeInt16(&pNode->zData[2], nCell+1);
-    pNode->isDirty = 1;
+  int iErr = (argc<6) ? 2 : argc>(RTREE_MAX_DIMENSIONS*2+4) ? 3 : argc%2;
+  if( aErrMsg[iErr] ){
+    *pzErr = sqlite3_mprintf("%s", aErrMsg[iErr]);
+    return SQLITE_ERROR;
   }
 
-  return (nCell==nMaxCell);
-}
+  sqlite3_vtab_config(db, SQLITE_VTAB_CONSTRAINT_SUPPORT, 1);
 
-/*
-** If the node is dirty, write it out to the database.
-*/
-static int nodeWrite(Rtree *pRtree, RtreeNode *pNode){
-  int rc = SQLITE_OK;
-  if( pNode->isDirty ){
-    sqlite3_stmt *p = pRtree->pWriteNode;
-    if( pNode->iNode ){
-      sqlite3_bind_int64(p, 1, pNode->iNode);
-    }else{
-      sqlite3_bind_null(p, 1);
-    }
-    sqlite3_bind_blob(p, 2, pNode->zData, pRtree->iNodeSize, SQLITE_STATIC);
-    sqlite3_step(p);
-    pNode->isDirty = 0;
-    rc = sqlite3_reset(p);
-    if( pNode->iNode==0 && rc==SQLITE_OK ){
-      pNode->iNode = sqlite3_last_insert_rowid(pRtree->db);
-      nodeHashInsert(pRtree, pNode);
-    }
+  /* Allocate the sqlite3_vtab structure */
+  nDb = (int)strlen(argv[1]);
+  nName = (int)strlen(argv[2]);
+  pRtree = (Rtree *)sqlite3_malloc(sizeof(Rtree)+nDb+nName+2);
+  if( !pRtree ){
+    return SQLITE_NOMEM;
   }
-  return rc;
-}
+  memset(pRtree, 0, sizeof(Rtree)+nDb+nName+2);
+  pRtree->nBusy = 1;
+  pRtree->base.pModule = &rtreeModule;
+  pRtree->zDb = (char *)&pRtree[1];
+  pRtree->zName = &pRtree->zDb[nDb+1];
+  pRtree->nDim = (argc-4)/2;
+  pRtree->nBytesPerCell = 8 + pRtree->nDim*4*2;
+  pRtree->eCoordType = eCoordType;
+  memcpy(pRtree->zDb, argv[1], nDb);
+  memcpy(pRtree->zName, argv[2], nName);
 
-/*
-** Release a reference to a node. If the node is dirty and the reference
-** count drops to zero, the node data is written to the database.
-*/
-static int nodeRelease(Rtree *pRtree, RtreeNode *pNode){
-  int rc = SQLITE_OK;
-  if( pNode ){
-    assert( pNode->nRef>0 );
-    pNode->nRef--;
-    if( pNode->nRef==0 ){
-      if( pNode->iNode==1 ){
-        pRtree->iDepth = -1;
+  /* Figure out the node size to use. */
+  rc = getNodeSize(db, pRtree, isCreate, pzErr);
+
+  /* Create/Connect to the underlying relational database schema. If
+  ** that is successful, call sqlite3_declare_vtab() to configure
+  ** the r-tree table schema.
+  */
+  if( rc==SQLITE_OK ){
+    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }else{
+      char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
+      char *zTmp;
+      int ii;
+      for(ii=4; zSql && ii<argc; ii++){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
+        sqlite3_free(zTmp);
       }
-      if( pNode->pParent ){
-        rc = nodeRelease(pRtree, pNode->pParent);
+      if( zSql ){
+        zTmp = zSql;
+        zSql = sqlite3_mprintf("%s);", zTmp);
+        sqlite3_free(zTmp);
       }
-      if( rc==SQLITE_OK ){
-        rc = nodeWrite(pRtree, pNode);
+      if( !zSql ){
+        rc = SQLITE_NOMEM;
+      }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
+        *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
       }
-      nodeHashDelete(pRtree, pNode);
-      sqlite3_free(pNode);
+      sqlite3_free(zSql);
     }
   }
-  return rc;
-}
 
-/*
-** Return the 64-bit integer value associated with cell iCell of
-** node pNode. If pNode is a leaf node, this is a rowid. If it is
-** an internal node, then the 64-bit integer is a child page number.
-*/
-static i64 nodeGetRowid(
-  Rtree *pRtree,       /* The overall R-Tree */
-  RtreeNode *pNode,    /* The node from which to extract the ID */
-  int iCell            /* The cell index from which to extract the ID */
-){
-  assert( iCell<NCELL(pNode) );
-  return readInt64(&pNode->zData[4 + pRtree->nBytesPerCell*iCell]);
+  if( rc==SQLITE_OK ){
+    *ppVtab = (sqlite3_vtab *)pRtree;
+  }else{
+    assert( *ppVtab==0 );
+    assert( pRtree->nBusy==1 );
+    rtreeRelease(pRtree);
+  }
+  return rc;
 }
 
-/*
-** Return coordinate iCoord from cell iCell in node pNode.
-*/
-static void nodeGetCoord(
-  Rtree *pRtree,               /* The overall R-Tree */
-  RtreeNode *pNode,            /* The node from which to extract a coordinate */
-  int iCell,                   /* The index of the cell within the node */
-  int iCoord,                  /* Which coordinate to extract */
-  RtreeCoord *pCoord           /* OUT: Space to write result to */
-){
-  readCoord(&pNode->zData[12 + pRtree->nBytesPerCell*iCell + 4*iCoord], pCoord);
-}
 
 /*
-** Deserialize cell iCell of node pNode. Populate the structure pointed
-** to by pCell with the results.
+** Implementation of a scalar function that decodes r-tree nodes to
+** human readable strings. This can be used for debugging and analysis.
+**
+** The scalar function takes two arguments: (1) the number of dimensions
+** to the rtree (between 1 and 5, inclusive) and (2) a blob of data containing
+** an r-tree node.  For a two-dimensional r-tree structure called "rt", to
+** deserialize all nodes, a statement like:
+**
+**   SELECT rtreenode(2, data) FROM rt_node;
+**
+** The human readable string takes the form of a Tcl list with one
+** entry for each cell in the r-tree node. Each entry is itself a
+** list, containing the 8-byte rowid/pageno followed by the 
+** <num-dimension>*2 coordinates.
 */
-static void nodeGetCell(
-  Rtree *pRtree,               /* The overall R-Tree */
-  RtreeNode *pNode,            /* The node containing the cell to be read */
-  int iCell,                   /* Index of the cell within the node */
-  RtreeCell *pCell             /* OUT: Write the cell contents here */
-){
-  u8 *pData;
-  RtreeCoord *pCoord;
+static void rtreenode(sqlite3_context *ctx, int nArg, sqlite3_value **apArg){
+  char *zText = 0;
+  RtreeNode node;
+  Rtree tree;
   int ii;
-  pCell->iRowid = nodeGetRowid(pRtree, pNode, iCell);
-  pData = pNode->zData + (12 + pRtree->nBytesPerCell*iCell);
-  pCoord = pCell->aCoord;
-  for(ii=0; ii<pRtree->nDim*2; ii++){
-    readCoord(&pData[ii*4], &pCoord[ii]);
-  }
-}
-
-
-/* Forward declaration for the function that does the work of
-** the virtual table module xCreate() and xConnect() methods.
-*/
-static int rtreeInit(
-  sqlite3 *, void *, int, const char *const*, sqlite3_vtab **, char **, int
-);
 
-/* 
-** Rtree virtual table module xCreate method.
-*/
-static int rtreeCreate(
-  sqlite3 *db,
-  void *pAux,
-  int argc, const char *const*argv,
-  sqlite3_vtab **ppVtab,
-  char **pzErr
-){
-  return rtreeInit(db, pAux, argc, argv, ppVtab, pzErr, 1);
-}
+  UNUSED_PARAMETER(nArg);
+  memset(&node, 0, sizeof(RtreeNode));
+  memset(&tree, 0, sizeof(Rtree));
+  tree.nDim = sqlite3_value_int(apArg[0]);
+  tree.nBytesPerCell = 8 + 8 * tree.nDim;
+  node.zData = (u8 *)sqlite3_value_blob(apArg[1]);
 
-/* 
-** Rtree virtual table module xConnect method.
-*/
-static int rtreeConnect(
-  sqlite3 *db,
-  void *pAux,
-  int argc, const char *const*argv,
-  sqlite3_vtab **ppVtab,
-  char **pzErr
-){
-  return rtreeInit(db, pAux, argc, argv, ppVtab, pzErr, 0);
-}
+  for(ii=0; ii<NCELL(&node); ii++){
+    char zCell[512];
+    int nCell = 0;
+    RtreeCell cell;
+    int jj;
 
-/*
-** Increment the r-tree reference count.
-*/
-static void rtreeReference(Rtree *pRtree){
-  pRtree->nBusy++;
-}
+    nodeGetCell(&tree, &node, ii, &cell);
+    sqlite3_snprintf(512-nCell,&zCell[nCell],"%lld", cell.iRowid);
+    nCell = (int)strlen(zCell);
+    for(jj=0; jj<tree.nDim*2; jj++){
+#ifndef SQLITE_RTREE_INT_ONLY
+      sqlite3_snprintf(512-nCell,&zCell[nCell], " %g",
+                       (double)cell.aCoord[jj].f);
+#else
+      sqlite3_snprintf(512-nCell,&zCell[nCell], " %d",
+                       cell.aCoord[jj].i);
+#endif
+      nCell = (int)strlen(zCell);
+    }
 
-/*
-** Decrement the r-tree reference count. When the reference count reaches
-** zero the structure is deleted.
-*/
-static void rtreeRelease(Rtree *pRtree){
-  pRtree->nBusy--;
-  if( pRtree->nBusy==0 ){
-    sqlite3_finalize(pRtree->pReadNode);
-    sqlite3_finalize(pRtree->pWriteNode);
-    sqlite3_finalize(pRtree->pDeleteNode);
-    sqlite3_finalize(pRtree->pReadRowid);
-    sqlite3_finalize(pRtree->pWriteRowid);
-    sqlite3_finalize(pRtree->pDeleteRowid);
-    sqlite3_finalize(pRtree->pReadParent);
-    sqlite3_finalize(pRtree->pWriteParent);
-    sqlite3_finalize(pRtree->pDeleteParent);
-    sqlite3_free(pRtree);
+    if( zText ){
+      char *zTextNew = sqlite3_mprintf("%s {%s}", zText, zCell);
+      sqlite3_free(zText);
+      zText = zTextNew;
+    }else{
+      zText = sqlite3_mprintf("{%s}", zCell);
+    }
   }
+  
+  sqlite3_result_text(ctx, zText, -1, sqlite3_free);
 }
 
-/* 
-** Rtree virtual table module xDisconnect method.
+/* This routine implements an SQL function that returns the "depth" parameter
+** from the front of a blob that is an r-tree node.  For example:
+**
+**     SELECT rtreedepth(data) FROM rt_node WHERE nodeno=1;
+**
+** The depth value is 0 for all nodes other than the root node, and the root
+** node always has nodeno=1, so the example above is the primary use for this
+** routine.  This routine is intended for testing and analysis only.
 */
-static int rtreeDisconnect(sqlite3_vtab *pVtab){
-  rtreeRelease((Rtree *)pVtab);
-  return SQLITE_OK;
+static void rtreedepth(sqlite3_context *ctx, int nArg, sqlite3_value **apArg){
+  UNUSED_PARAMETER(nArg);
+  if( sqlite3_value_type(apArg[0])!=SQLITE_BLOB 
+   || sqlite3_value_bytes(apArg[0])<2
+  ){
+    sqlite3_result_error(ctx, "Invalid argument to rtreedepth()", -1); 
+  }else{
+    u8 *zBlob = (u8 *)sqlite3_value_blob(apArg[0]);
+    sqlite3_result_int(ctx, readInt16(zBlob));
+  }
 }
 
-/* 
-** Rtree virtual table module xDestroy method.
+/*
+** Register the r-tree module with database handle db. This creates the
+** virtual table module "rtree" and the debugging/analysis scalar 
+** function "rtreenode".
 */
-static int rtreeDestroy(sqlite3_vtab *pVtab){
-  Rtree *pRtree = (Rtree *)pVtab;
+SQLITE_PRIVATE int sqlite3RtreeInit(sqlite3 *db){
+  const int utf8 = SQLITE_UTF8;
   int rc;
-  char *zCreate = sqlite3_mprintf(
-    "DROP TABLE '%q'.'%q_node';"
-    "DROP TABLE '%q'.'%q_rowid';"
-    "DROP TABLE '%q'.'%q_parent';",
-    pRtree->zDb, pRtree->zName, 
-    pRtree->zDb, pRtree->zName,
-    pRtree->zDb, pRtree->zName
-  );
-  if( !zCreate ){
-    rc = SQLITE_NOMEM;
-  }else{
-    rc = sqlite3_exec(pRtree->db, zCreate, 0, 0, 0);
-    sqlite3_free(zCreate);
+
+  rc = sqlite3_create_function(db, "rtreenode", 2, utf8, 0, rtreenode, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "rtreedepth", 1, utf8, 0,rtreedepth, 0, 0);
   }
   if( rc==SQLITE_OK ){
-    rtreeRelease(pRtree);
+#ifdef SQLITE_RTREE_INT_ONLY
+    void *c = (void *)RTREE_COORD_INT32;
+#else
+    void *c = (void *)RTREE_COORD_REAL32;
+#endif
+    rc = sqlite3_create_module_v2(db, "rtree", &rtreeModule, c, 0);
+  }
+  if( rc==SQLITE_OK ){
+    void *c = (void *)RTREE_COORD_INT32;
+    rc = sqlite3_create_module_v2(db, "rtree_i32", &rtreeModule, c, 0);
   }
 
   return rc;
 }
 
-/* 
-** Rtree virtual table module xOpen method.
+/*
+** This routine deletes the RtreeGeomCallback object that was attached
+** one of the SQL functions create by sqlite3_rtree_geometry_callback()
+** or sqlite3_rtree_query_callback().  In other words, this routine is the
+** destructor for an RtreeGeomCallback objecct.  This routine is called when
+** the corresponding SQL function is deleted.
 */
-static int rtreeOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
-  int rc = SQLITE_NOMEM;
-  RtreeCursor *pCsr;
+static void rtreeFreeCallback(void *p){
+  RtreeGeomCallback *pInfo = (RtreeGeomCallback*)p;
+  if( pInfo->xDestructor ) pInfo->xDestructor(pInfo->pContext);
+  sqlite3_free(p);
+}
 
-  pCsr = (RtreeCursor *)sqlite3_malloc(sizeof(RtreeCursor));
-  if( pCsr ){
-    memset(pCsr, 0, sizeof(RtreeCursor));
-    pCsr->base.pVtab = pVTab;
-    rc = SQLITE_OK;
+/*
+** This routine frees the BLOB that is returned by geomCallback().
+*/
+static void rtreeMatchArgFree(void *pArg){
+  int i;
+  RtreeMatchArg *p = (RtreeMatchArg*)pArg;
+  for(i=0; i<p->nParam; i++){
+    sqlite3_value_free(p->apSqlParam[i]);
   }
-  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
-
-  return rc;
+  sqlite3_free(p);
 }
 
-
 /*
-** Free the RtreeCursor.aConstraint[] array and its contents.
+** Each call to sqlite3_rtree_geometry_callback() or
+** sqlite3_rtree_query_callback() creates an ordinary SQLite
+** scalar function that is implemented by this routine.
+**
+** All this function does is construct an RtreeMatchArg object that
+** contains the geometry-checking callback routines and a list of
+** parameters to this function, then return that RtreeMatchArg object
+** as a BLOB.
+**
+** The R-Tree MATCH operator will read the returned BLOB, deserialize
+** the RtreeMatchArg object, and use the RtreeMatchArg object to figure
+** out which elements of the R-Tree should be returned by the query.
 */
-static void freeCursorConstraints(RtreeCursor *pCsr){
-  if( pCsr->aConstraint ){
-    int i;                        /* Used to iterate through constraint array */
-    for(i=0; i<pCsr->nConstraint; i++){
-      sqlite3_rtree_query_info *pInfo = pCsr->aConstraint[i].pInfo;
-      if( pInfo ){
-        if( pInfo->xDelUser ) pInfo->xDelUser(pInfo->pUser);
-        sqlite3_free(pInfo);
-      }
+static void geomCallback(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
+  RtreeGeomCallback *pGeomCtx = (RtreeGeomCallback *)sqlite3_user_data(ctx);
+  RtreeMatchArg *pBlob;
+  int nBlob;
+  int memErr = 0;
+
+  nBlob = sizeof(RtreeMatchArg) + (nArg-1)*sizeof(RtreeDValue)
+           + nArg*sizeof(sqlite3_value*);
+  pBlob = (RtreeMatchArg *)sqlite3_malloc(nBlob);
+  if( !pBlob ){
+    sqlite3_result_error_nomem(ctx);
+  }else{
+    int i;
+    pBlob->magic = RTREE_GEOMETRY_MAGIC;
+    pBlob->cb = pGeomCtx[0];
+    pBlob->apSqlParam = (sqlite3_value**)&pBlob->aParam[nArg];
+    pBlob->nParam = nArg;
+    for(i=0; i<nArg; i++){
+      pBlob->apSqlParam[i] = sqlite3_value_dup(aArg[i]);
+      if( pBlob->apSqlParam[i]==0 ) memErr = 1;
+#ifdef SQLITE_RTREE_INT_ONLY
+      pBlob->aParam[i] = sqlite3_value_int64(aArg[i]);
+#else
+      pBlob->aParam[i] = sqlite3_value_double(aArg[i]);
+#endif
+    }
+    if( memErr ){
+      sqlite3_result_error_nomem(ctx);
+      rtreeMatchArgFree(pBlob);
+    }else{
+      sqlite3_result_blob(ctx, pBlob, nBlob, rtreeMatchArgFree);
     }
-    sqlite3_free(pCsr->aConstraint);
-    pCsr->aConstraint = 0;
   }
 }
 
-/* 
-** Rtree virtual table module xClose method.
+/*
+** Register a new geometry function for use with the r-tree MATCH operator.
 */
-static int rtreeClose(sqlite3_vtab_cursor *cur){
-  Rtree *pRtree = (Rtree *)(cur->pVtab);
-  int ii;
-  RtreeCursor *pCsr = (RtreeCursor *)cur;
-  freeCursorConstraints(pCsr);
-  sqlite3_free(pCsr->aPoint);
-  for(ii=0; ii<RTREE_CACHE_SZ; ii++) nodeRelease(pRtree, pCsr->aNode[ii]);
-  sqlite3_free(pCsr);
-  return SQLITE_OK;
+SQLITE_API int SQLITE_STDCALL sqlite3_rtree_geometry_callback(
+  sqlite3 *db,                  /* Register SQL function on this connection */
+  const char *zGeom,            /* Name of the new SQL function */
+  int (*xGeom)(sqlite3_rtree_geometry*,int,RtreeDValue*,int*), /* Callback */
+  void *pContext                /* Extra data associated with the callback */
+){
+  RtreeGeomCallback *pGeomCtx;      /* Context object for new user-function */
+
+  /* Allocate and populate the context object. */
+  pGeomCtx = (RtreeGeomCallback *)sqlite3_malloc(sizeof(RtreeGeomCallback));
+  if( !pGeomCtx ) return SQLITE_NOMEM;
+  pGeomCtx->xGeom = xGeom;
+  pGeomCtx->xQueryFunc = 0;
+  pGeomCtx->xDestructor = 0;
+  pGeomCtx->pContext = pContext;
+  return sqlite3_create_function_v2(db, zGeom, -1, SQLITE_ANY, 
+      (void *)pGeomCtx, geomCallback, 0, 0, rtreeFreeCallback
+  );
 }
 
 /*
-** Rtree virtual table module xEof method.
-**
-** Return non-zero if the cursor does not currently point to a valid 
-** record (i.e if the scan has finished), or zero otherwise.
+** Register a new 2nd-generation geometry function for use with the
+** r-tree MATCH operator.
 */
-static int rtreeEof(sqlite3_vtab_cursor *cur){
-  RtreeCursor *pCsr = (RtreeCursor *)cur;
-  return pCsr->atEOF;
+SQLITE_API int SQLITE_STDCALL sqlite3_rtree_query_callback(
+  sqlite3 *db,                 /* Register SQL function on this connection */
+  const char *zQueryFunc,      /* Name of new SQL function */
+  int (*xQueryFunc)(sqlite3_rtree_query_info*), /* Callback */
+  void *pContext,              /* Extra data passed into the callback */
+  void (*xDestructor)(void*)   /* Destructor for the extra data */
+){
+  RtreeGeomCallback *pGeomCtx;      /* Context object for new user-function */
+
+  /* Allocate and populate the context object. */
+  pGeomCtx = (RtreeGeomCallback *)sqlite3_malloc(sizeof(RtreeGeomCallback));
+  if( !pGeomCtx ) return SQLITE_NOMEM;
+  pGeomCtx->xGeom = 0;
+  pGeomCtx->xQueryFunc = xQueryFunc;
+  pGeomCtx->xDestructor = xDestructor;
+  pGeomCtx->pContext = pContext;
+  return sqlite3_create_function_v2(db, zQueryFunc, -1, SQLITE_ANY, 
+      (void *)pGeomCtx, geomCallback, 0, 0, rtreeFreeCallback
+  );
+}
+
+#if !SQLITE_CORE
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+SQLITE_API int SQLITE_STDCALL sqlite3_rtree_init(
+  sqlite3 *db,
+  char **pzErrMsg,
+  const sqlite3_api_routines *pApi
+){
+  SQLITE_EXTENSION_INIT2(pApi)
+  return sqlite3RtreeInit(db);
 }
+#endif
+
+#endif
 
+/************** End of rtree.c ***********************************************/
+/************** Begin file icu.c *********************************************/
 /*
-** Convert raw bits from the on-disk RTree record into a coordinate value.
-** The on-disk format is big-endian and needs to be converted for little-
-** endian platforms.  The on-disk record stores integer coordinates if
-** eInt is true and it stores 32-bit floating point records if eInt is
-** false.  a[] is the four bytes of the on-disk record to be decoded.
-** Store the results in "r".
+** 2007 May 6
 **
-** There are three versions of this macro, one each for little-endian and
-** big-endian processors and a third generic implementation.  The endian-
-** specific implementations are much faster and are preferred if the
-** processor endianness is known at compile-time.  The SQLITE_BYTEORDER
-** macro is part of sqliteInt.h and hence the endian-specific
-** implementation will only be used if this module is compiled as part
-** of the amalgamation.
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** $Id: icu.c,v 1.7 2007/12/13 21:54:11 drh Exp $
+**
+** This file implements an integration between the ICU library 
+** ("International Components for Unicode", an open-source library 
+** for handling unicode data) and SQLite. The integration uses 
+** ICU to provide the following to SQLite:
+**
+**   * An implementation of the SQL regexp() function (and hence REGEXP
+**     operator) using the ICU uregex_XX() APIs.
+**
+**   * Implementations of the SQL scalar upper() and lower() functions
+**     for case mapping.
+**
+**   * Integration of ICU and SQLite collation sequences.
+**
+**   * An implementation of the LIKE operator that uses ICU to 
+**     provide case-independent matching.
 */
-#if defined(SQLITE_BYTEORDER) && SQLITE_BYTEORDER==1234
-#define RTREE_DECODE_COORD(eInt, a, r) {                        \
-    RtreeCoord c;    /* Coordinate decoded */                   \
-    memcpy(&c.u,a,4);                                           \
-    c.u = ((c.u>>24)&0xff)|((c.u>>8)&0xff00)|                   \
-          ((c.u&0xff)<<24)|((c.u&0xff00)<<8);                   \
-    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
-}
-#elif defined(SQLITE_BYTEORDER) && SQLITE_BYTEORDER==4321
-#define RTREE_DECODE_COORD(eInt, a, r) {                        \
-    RtreeCoord c;    /* Coordinate decoded */                   \
-    memcpy(&c.u,a,4);                                           \
-    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
-}
+
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU)
+
+/* Include ICU headers */
+#include <unicode/utypes.h>
+#include <unicode/uregex.h>
+#include <unicode/ustring.h>
+#include <unicode/ucol.h>
+
+/* #include <assert.h> */
+
+#ifndef SQLITE_CORE
+/*   #include "sqlite3ext.h" */
+  SQLITE_EXTENSION_INIT1
 #else
-#define RTREE_DECODE_COORD(eInt, a, r) {                        \
-    RtreeCoord c;    /* Coordinate decoded */                   \
-    c.u = ((u32)a[0]<<24) + ((u32)a[1]<<16)                     \
-           +((u32)a[2]<<8) + a[3];                              \
-    r = eInt ? (sqlite3_rtree_dbl)c.i : (sqlite3_rtree_dbl)c.f; \
-}
+/*   #include "sqlite3.h" */
 #endif
 
 /*
-** Check the RTree node or entry given by pCellData and p against the MATCH
-** constraint pConstraint.  
+** Maximum length (in bytes) of the pattern in a LIKE or GLOB
+** operator.
 */
-static int rtreeCallbackConstraint(
-  RtreeConstraint *pConstraint,  /* The constraint to test */
-  int eInt,                      /* True if RTree holding integer coordinates */
-  u8 *pCellData,                 /* Raw cell content */
-  RtreeSearchPoint *pSearch,     /* Container of this cell */
-  sqlite3_rtree_dbl *prScore,    /* OUT: score for the cell */
-  int *peWithin                  /* OUT: visibility of the cell */
-){
-  int i;                                                /* Loop counter */
-  sqlite3_rtree_query_info *pInfo = pConstraint->pInfo; /* Callback info */
-  int nCoord = pInfo->nCoord;                           /* No. of coordinates */
-  int rc;                                             /* Callback return code */
-  sqlite3_rtree_dbl aCoord[RTREE_MAX_DIMENSIONS*2];   /* Decoded coordinates */
-
-  assert( pConstraint->op==RTREE_MATCH || pConstraint->op==RTREE_QUERY );
-  assert( nCoord==2 || nCoord==4 || nCoord==6 || nCoord==8 || nCoord==10 );
+#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
+# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
+#endif
 
-  if( pConstraint->op==RTREE_QUERY && pSearch->iLevel==1 ){
-    pInfo->iRowid = readInt64(pCellData);
-  }
-  pCellData += 8;
-  for(i=0; i<nCoord; i++, pCellData += 4){
-    RTREE_DECODE_COORD(eInt, pCellData, aCoord[i]);
-  }
-  if( pConstraint->op==RTREE_MATCH ){
-    rc = pConstraint->u.xGeom((sqlite3_rtree_geometry*)pInfo,
-                              nCoord, aCoord, &i);
-    if( i==0 ) *peWithin = NOT_WITHIN;
-    *prScore = RTREE_ZERO;
-  }else{
-    pInfo->aCoord = aCoord;
-    pInfo->iLevel = pSearch->iLevel - 1;
-    pInfo->rScore = pInfo->rParentScore = pSearch->rScore;
-    pInfo->eWithin = pInfo->eParentWithin = pSearch->eWithin;
-    rc = pConstraint->u.xQueryFunc(pInfo);
-    if( pInfo->eWithin<*peWithin ) *peWithin = pInfo->eWithin;
-    if( pInfo->rScore<*prScore || *prScore<RTREE_ZERO ){
-      *prScore = pInfo->rScore;
-    }
-  }
-  return rc;
+/*
+** Version of sqlite3_free() that is always a function, never a macro.
+*/
+static void xFree(void *p){
+  sqlite3_free(p);
 }
 
-/* 
-** Check the internal RTree node given by pCellData against constraint p.
-** If this constraint cannot be satisfied by any child within the node,
-** set *peWithin to NOT_WITHIN.
+/*
+** Compare two UTF-8 strings for equality where the first string is
+** a "LIKE" expression. Return true (1) if they are the same and 
+** false (0) if they are different.
 */
-static void rtreeNonleafConstraint(
-  RtreeConstraint *p,        /* The constraint to test */
-  int eInt,                  /* True if RTree holds integer coordinates */
-  u8 *pCellData,             /* Raw cell content as appears on disk */
-  int *peWithin              /* Adjust downward, as appropriate */
+static int icuLikeCompare(
+  const uint8_t *zPattern,   /* LIKE pattern */
+  const uint8_t *zString,    /* The UTF-8 string to compare against */
+  const UChar32 uEsc         /* The escape character */
 ){
-  sqlite3_rtree_dbl val;     /* Coordinate value convert to a double */
+  static const int MATCH_ONE = (UChar32)'_';
+  static const int MATCH_ALL = (UChar32)'%';
 
-  /* p->iCoord might point to either a lower or upper bound coordinate
-  ** in a coordinate pair.  But make pCellData point to the lower bound.
-  */
-  pCellData += 8 + 4*(p->iCoord&0xfe);
+  int iPattern = 0;       /* Current byte index in zPattern */
+  int iString = 0;        /* Current byte index in zString */
 
-  assert(p->op==RTREE_LE || p->op==RTREE_LT || p->op==RTREE_GE 
-      || p->op==RTREE_GT || p->op==RTREE_EQ );
-  switch( p->op ){
-    case RTREE_LE:
-    case RTREE_LT:
-    case RTREE_EQ:
-      RTREE_DECODE_COORD(eInt, pCellData, val);
-      /* val now holds the lower bound of the coordinate pair */
-      if( p->u.rValue>=val ) return;
-      if( p->op!=RTREE_EQ ) break;  /* RTREE_LE and RTREE_LT end here */
-      /* Fall through for the RTREE_EQ case */
+  int prevEscape = 0;     /* True if the previous character was uEsc */
 
-    default: /* RTREE_GT or RTREE_GE,  or fallthrough of RTREE_EQ */
-      pCellData += 4;
-      RTREE_DECODE_COORD(eInt, pCellData, val);
-      /* val now holds the upper bound of the coordinate pair */
-      if( p->u.rValue<=val ) return;
+  while( zPattern[iPattern]!=0 ){
+
+    /* Read (and consume) the next character from the input pattern. */
+    UChar32 uPattern;
+    U8_NEXT_UNSAFE(zPattern, iPattern, uPattern);
+
+    /* There are now 4 possibilities:
+    **
+    **     1. uPattern is an unescaped match-all character "%",
+    **     2. uPattern is an unescaped match-one character "_",
+    **     3. uPattern is an unescaped escape character, or
+    **     4. uPattern is to be handled as an ordinary character
+    */
+    if( !prevEscape && uPattern==MATCH_ALL ){
+      /* Case 1. */
+      uint8_t c;
+
+      /* Skip any MATCH_ALL or MATCH_ONE characters that follow a
+      ** MATCH_ALL. For each MATCH_ONE, skip one character in the 
+      ** test string.
+      */
+      while( (c=zPattern[iPattern]) == MATCH_ALL || c == MATCH_ONE ){
+        if( c==MATCH_ONE ){
+          if( zString[iString]==0 ) return 0;
+          U8_FWD_1_UNSAFE(zString, iString);
+        }
+        iPattern++;
+      }
+
+      if( zPattern[iPattern]==0 ) return 1;
+
+      while( zString[iString] ){
+        if( icuLikeCompare(&zPattern[iPattern], &zString[iString], uEsc) ){
+          return 1;
+        }
+        U8_FWD_1_UNSAFE(zString, iString);
+      }
+      return 0;
+
+    }else if( !prevEscape && uPattern==MATCH_ONE ){
+      /* Case 2. */
+      if( zString[iString]==0 ) return 0;
+      U8_FWD_1_UNSAFE(zString, iString);
+
+    }else if( !prevEscape && uPattern==uEsc){
+      /* Case 3. */
+      prevEscape = 1;
+
+    }else{
+      /* Case 4. */
+      UChar32 uString;
+      U8_NEXT_UNSAFE(zString, iString, uString);
+      uString = u_foldCase(uString, U_FOLD_CASE_DEFAULT);
+      uPattern = u_foldCase(uPattern, U_FOLD_CASE_DEFAULT);
+      if( uString!=uPattern ){
+        return 0;
+      }
+      prevEscape = 0;
+    }
   }
-  *peWithin = NOT_WITHIN;
+
+  return zString[iString]==0;
 }
 
 /*
-** Check the leaf RTree cell given by pCellData against constraint p.
-** If this constraint is not satisfied, set *peWithin to NOT_WITHIN.
-** If the constraint is satisfied, leave *peWithin unchanged.
+** Implementation of the like() SQL function.  This function implements
+** the build-in LIKE operator.  The first argument to the function is the
+** pattern and the second argument is the string.  So, the SQL statements:
 **
-** The constraint is of the form:  xN op $val
+**       A LIKE B
 **
-** The op is given by p->op.  The xN is p->iCoord-th coordinate in
-** pCellData.  $val is given by p->u.rValue.
+** is implemented as like(B, A). If there is an escape character E, 
+**
+**       A LIKE B ESCAPE E
+**
+** is mapped to like(B, A, E).
 */
-static void rtreeLeafConstraint(
-  RtreeConstraint *p,        /* The constraint to test */
-  int eInt,                  /* True if RTree holds integer coordinates */
-  u8 *pCellData,             /* Raw cell content as appears on disk */
-  int *peWithin              /* Adjust downward, as appropriate */
+static void icuLikeFunc(
+  sqlite3_context *context, 
+  int argc, 
+  sqlite3_value **argv
 ){
-  RtreeDValue xN;      /* Coordinate value converted to a double */
+  const unsigned char *zA = sqlite3_value_text(argv[0]);
+  const unsigned char *zB = sqlite3_value_text(argv[1]);
+  UChar32 uEsc = 0;
 
-  assert(p->op==RTREE_LE || p->op==RTREE_LT || p->op==RTREE_GE 
-      || p->op==RTREE_GT || p->op==RTREE_EQ );
-  pCellData += 8 + p->iCoord*4;
-  RTREE_DECODE_COORD(eInt, pCellData, xN);
-  switch( p->op ){
-    case RTREE_LE: if( xN <= p->u.rValue ) return;  break;
-    case RTREE_LT: if( xN <  p->u.rValue ) return;  break;
-    case RTREE_GE: if( xN >= p->u.rValue ) return;  break;
-    case RTREE_GT: if( xN >  p->u.rValue ) return;  break;
-    default:       if( xN == p->u.rValue ) return;  break;
+  /* Limit the length of the LIKE or GLOB pattern to avoid problems
+  ** of deep recursion and N*N behavior in patternCompare().
+  */
+  if( sqlite3_value_bytes(argv[0])>SQLITE_MAX_LIKE_PATTERN_LENGTH ){
+    sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
+    return;
   }
-  *peWithin = NOT_WITHIN;
-}
 
-/*
-** One of the cells in node pNode is guaranteed to have a 64-bit 
-** integer value equal to iRowid. Return the index of this cell.
-*/
-static int nodeRowidIndex(
-  Rtree *pRtree, 
-  RtreeNode *pNode, 
-  i64 iRowid,
-  int *piIndex
-){
-  int ii;
-  int nCell = NCELL(pNode);
-  assert( nCell<200 );
-  for(ii=0; ii<nCell; ii++){
-    if( nodeGetRowid(pRtree, pNode, ii)==iRowid ){
-      *piIndex = ii;
-      return SQLITE_OK;
+
+  if( argc==3 ){
+    /* The escape character string must consist of a single UTF-8 character.
+    ** Otherwise, return an error.
+    */
+    int nE= sqlite3_value_bytes(argv[2]);
+    const unsigned char *zE = sqlite3_value_text(argv[2]);
+    int i = 0;
+    if( zE==0 ) return;
+    U8_NEXT(zE, i, nE, uEsc);
+    if( i!=nE){
+      sqlite3_result_error(context, 
+          "ESCAPE expression must be a single character", -1);
+      return;
     }
   }
-  return SQLITE_CORRUPT_VTAB;
-}
 
-/*
-** Return the index of the cell containing a pointer to node pNode
-** in its parent. If pNode is the root node, return -1.
-*/
-static int nodeParentIndex(Rtree *pRtree, RtreeNode *pNode, int *piIndex){
-  RtreeNode *pParent = pNode->pParent;
-  if( pParent ){
-    return nodeRowidIndex(pRtree, pParent, pNode->iNode, piIndex);
+  if( zA && zB ){
+    sqlite3_result_int(context, icuLikeCompare(zA, zB, uEsc));
   }
-  *piIndex = -1;
-  return SQLITE_OK;
 }
 
 /*
-** Compare two search points.  Return negative, zero, or positive if the first
-** is less than, equal to, or greater than the second.
+** This function is called when an ICU function called from within
+** the implementation of an SQL scalar function returns an error.
 **
-** The rScore is the primary key.  Smaller rScore values come first.
-** If the rScore is a tie, then use iLevel as the tie breaker with smaller
-** iLevel values coming first.  In this way, if rScore is the same for all
-** SearchPoints, then iLevel becomes the deciding factor and the result
-** is a depth-first search, which is the desired default behavior.
+** The scalar function context passed as the first argument is 
+** loaded with an error message based on the following two args.
 */
-static int rtreeSearchPointCompare(
-  const RtreeSearchPoint *pA,
-  const RtreeSearchPoint *pB
+static void icuFunctionError(
+  sqlite3_context *pCtx,       /* SQLite scalar function context */
+  const char *zName,           /* Name of ICU function that failed */
+  UErrorCode e                 /* Error code returned by ICU function */
 ){
-  if( pA->rScore<pB->rScore ) return -1;
-  if( pA->rScore>pB->rScore ) return +1;
-  if( pA->iLevel<pB->iLevel ) return -1;
-  if( pA->iLevel>pB->iLevel ) return +1;
-  return 0;
+  char zBuf[128];
+  sqlite3_snprintf(128, zBuf, "ICU error: %s(): %s", zName, u_errorName(e));
+  zBuf[127] = '\0';
+  sqlite3_result_error(pCtx, zBuf, -1);
 }
 
 /*
-** Interchange to search points in a cursor.
+** Function to delete compiled regexp objects. Registered as
+** a destructor function with sqlite3_set_auxdata().
 */
-static void rtreeSearchPointSwap(RtreeCursor *p, int i, int j){
-  RtreeSearchPoint t = p->aPoint[i];
-  assert( i<j );
-  p->aPoint[i] = p->aPoint[j];
-  p->aPoint[j] = t;
-  i++; j++;
-  if( i<RTREE_CACHE_SZ ){
-    if( j>=RTREE_CACHE_SZ ){
-      nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
-      p->aNode[i] = 0;
+static void icuRegexpDelete(void *p){
+  URegularExpression *pExpr = (URegularExpression *)p;
+  uregex_close(pExpr);
+}
+
+/*
+** Implementation of SQLite REGEXP operator. This scalar function takes
+** two arguments. The first is a regular expression pattern to compile
+** the second is a string to match against that pattern. If either 
+** argument is an SQL NULL, then NULL Is returned. Otherwise, the result
+** is 1 if the string matches the pattern, or 0 otherwise.
+**
+** SQLite maps the regexp() function to the regexp() operator such
+** that the following two are equivalent:
+**
+**     zString REGEXP zPattern
+**     regexp(zPattern, zString)
+**
+** Uses the following ICU regexp APIs:
+**
+**     uregex_open()
+**     uregex_matches()
+**     uregex_close()
+*/
+static void icuRegexpFunc(sqlite3_context *p, int nArg, sqlite3_value **apArg){
+  UErrorCode status = U_ZERO_ERROR;
+  URegularExpression *pExpr;
+  UBool res;
+  const UChar *zString = sqlite3_value_text16(apArg[1]);
+
+  (void)nArg;  /* Unused parameter */
+
+  /* If the left hand side of the regexp operator is NULL, 
+  ** then the result is also NULL. 
+  */
+  if( !zString ){
+    return;
+  }
+
+  pExpr = sqlite3_get_auxdata(p, 0);
+  if( !pExpr ){
+    const UChar *zPattern = sqlite3_value_text16(apArg[0]);
+    if( !zPattern ){
+      return;
+    }
+    pExpr = uregex_open(zPattern, -1, 0, 0, &status);
+
+    if( U_SUCCESS(status) ){
+      sqlite3_set_auxdata(p, 0, pExpr, icuRegexpDelete);
     }else{
-      RtreeNode *pTemp = p->aNode[i];
-      p->aNode[i] = p->aNode[j];
-      p->aNode[j] = pTemp;
+      assert(!pExpr);
+      icuFunctionError(p, "uregex_open", status);
+      return;
     }
   }
+
+  /* Configure the text that the regular expression operates on. */
+  uregex_setText(pExpr, zString, -1, &status);
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "uregex_setText", status);
+    return;
+  }
+
+  /* Attempt the match */
+  res = uregex_matches(pExpr, 0, &status);
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "uregex_matches", status);
+    return;
+  }
+
+  /* Set the text that the regular expression operates on to a NULL
+  ** pointer. This is not really necessary, but it is tidier than 
+  ** leaving the regular expression object configured with an invalid
+  ** pointer after this function returns.
+  */
+  uregex_setText(pExpr, 0, 0, &status);
+
+  /* Return 1 or 0. */
+  sqlite3_result_int(p, res ? 1 : 0);
 }
 
 /*
-** Return the search point with the lowest current score.
+** Implementations of scalar functions for case mapping - upper() and 
+** lower(). Function upper() converts its input to upper-case (ABC).
+** Function lower() converts to lower-case (abc).
+**
+** ICU provides two types of case mapping, "general" case mapping and
+** "language specific". Refer to ICU documentation for the differences
+** between the two.
+**
+** To utilise "general" case mapping, the upper() or lower() scalar 
+** functions are invoked with one argument:
+**
+**     upper('ABC') -> 'abc'
+**     lower('abc') -> 'ABC'
+**
+** To access ICU "language specific" case mapping, upper() or lower()
+** should be invoked with two arguments. The second argument is the name
+** of the locale to use. Passing an empty string ("") or SQL NULL value
+** as the second argument is the same as invoking the 1 argument version
+** of upper() or lower().
+**
+**     lower('I', 'en_us') -> 'i'
+**     lower('I', 'tr_tr') -> 'ı' (small dotless i)
+**
+** http://www.icu-project.org/userguide/posix.html#case_mappings
 */
-static RtreeSearchPoint *rtreeSearchPointFirst(RtreeCursor *pCur){
-  return pCur->bPoint ? &pCur->sPoint : pCur->nPoint ? pCur->aPoint : 0;
+static void icuCaseFunc16(sqlite3_context *p, int nArg, sqlite3_value **apArg){
+  const UChar *zInput;
+  UChar *zOutput;
+  int nInput;
+  int nOutput;
+
+  UErrorCode status = U_ZERO_ERROR;
+  const char *zLocale = 0;
+
+  assert(nArg==1 || nArg==2);
+  if( nArg==2 ){
+    zLocale = (const char *)sqlite3_value_text(apArg[1]);
+  }
+
+  zInput = sqlite3_value_text16(apArg[0]);
+  if( !zInput ){
+    return;
+  }
+  nInput = sqlite3_value_bytes16(apArg[0]);
+
+  nOutput = nInput * 2 + 2;
+  zOutput = sqlite3_malloc(nOutput);
+  if( !zOutput ){
+    return;
+  }
+
+  if( sqlite3_user_data(p) ){
+    u_strToUpper(zOutput, nOutput/2, zInput, nInput/2, zLocale, &status);
+  }else{
+    u_strToLower(zOutput, nOutput/2, zInput, nInput/2, zLocale, &status);
+  }
+
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "u_strToLower()/u_strToUpper", status);
+    return;
+  }
+
+  sqlite3_result_text16(p, zOutput, -1, xFree);
 }
 
 /*
-** Get the RtreeNode for the search point with the lowest score.
+** Collation sequence destructor function. The pCtx argument points to
+** a UCollator structure previously allocated using ucol_open().
 */
-static RtreeNode *rtreeNodeOfFirstSearchPoint(RtreeCursor *pCur, int *pRC){
-  sqlite3_int64 id;
-  int ii = 1 - pCur->bPoint;
-  assert( ii==0 || ii==1 );
-  assert( pCur->bPoint || pCur->nPoint );
-  if( pCur->aNode[ii]==0 ){
-    assert( pRC!=0 );
-    id = ii ? pCur->aPoint[0].id : pCur->sPoint.id;
-    *pRC = nodeAcquire(RTREE_OF_CURSOR(pCur), id, 0, &pCur->aNode[ii]);
-  }
-  return pCur->aNode[ii];
+static void icuCollationDel(void *pCtx){
+  UCollator *p = (UCollator *)pCtx;
+  ucol_close(p);
 }
 
 /*
-** Push a new element onto the priority queue
+** Collation sequence comparison function. The pCtx argument points to
+** a UCollator structure previously allocated using ucol_open().
 */
-static RtreeSearchPoint *rtreeEnqueue(
-  RtreeCursor *pCur,    /* The cursor */
-  RtreeDValue rScore,   /* Score for the new search point */
-  u8 iLevel             /* Level for the new search point */
+static int icuCollationColl(
+  void *pCtx,
+  int nLeft,
+  const void *zLeft,
+  int nRight,
+  const void *zRight
 ){
-  int i, j;
-  RtreeSearchPoint *pNew;
-  if( pCur->nPoint>=pCur->nPointAlloc ){
-    int nNew = pCur->nPointAlloc*2 + 8;
-    pNew = sqlite3_realloc(pCur->aPoint, nNew*sizeof(pCur->aPoint[0]));
-    if( pNew==0 ) return 0;
-    pCur->aPoint = pNew;
-    pCur->nPointAlloc = nNew;
-  }
-  i = pCur->nPoint++;
-  pNew = pCur->aPoint + i;
-  pNew->rScore = rScore;
-  pNew->iLevel = iLevel;
-  assert( iLevel<=RTREE_MAX_DEPTH );
-  while( i>0 ){
-    RtreeSearchPoint *pParent;
-    j = (i-1)/2;
-    pParent = pCur->aPoint + j;
-    if( rtreeSearchPointCompare(pNew, pParent)>=0 ) break;
-    rtreeSearchPointSwap(pCur, j, i);
-    i = j;
-    pNew = pParent;
+  UCollationResult res;
+  UCollator *p = (UCollator *)pCtx;
+  res = ucol_strcoll(p, (UChar *)zLeft, nLeft/2, (UChar *)zRight, nRight/2);
+  switch( res ){
+    case UCOL_LESS:    return -1;
+    case UCOL_GREATER: return +1;
+    case UCOL_EQUAL:   return 0;
   }
-  return pNew;
+  assert(!"Unexpected return value from ucol_strcoll()");
+  return 0;
 }
 
 /*
-** Allocate a new RtreeSearchPoint and return a pointer to it.  Return
-** NULL if malloc fails.
+** Implementation of the scalar function icu_load_collation().
+**
+** This scalar function is used to add ICU collation based collation 
+** types to an SQLite database connection. It is intended to be called
+** as follows:
+**
+**     SELECT icu_load_collation(<locale>, <collation-name>);
+**
+** Where <locale> is a string containing an ICU locale identifier (i.e.
+** "en_AU", "tr_TR" etc.) and <collation-name> is the name of the
+** collation sequence to create.
 */
-static RtreeSearchPoint *rtreeSearchPointNew(
-  RtreeCursor *pCur,    /* The cursor */
-  RtreeDValue rScore,   /* Score for the new search point */
-  u8 iLevel             /* Level for the new search point */
+static void icuLoadCollation(
+  sqlite3_context *p, 
+  int nArg, 
+  sqlite3_value **apArg
 ){
-  RtreeSearchPoint *pNew, *pFirst;
-  pFirst = rtreeSearchPointFirst(pCur);
-  pCur->anQueue[iLevel]++;
-  if( pFirst==0
-   || pFirst->rScore>rScore 
-   || (pFirst->rScore==rScore && pFirst->iLevel>iLevel)
-  ){
-    if( pCur->bPoint ){
-      int ii;
-      pNew = rtreeEnqueue(pCur, rScore, iLevel);
-      if( pNew==0 ) return 0;
-      ii = (int)(pNew - pCur->aPoint) + 1;
-      if( ii<RTREE_CACHE_SZ ){
-        assert( pCur->aNode[ii]==0 );
-        pCur->aNode[ii] = pCur->aNode[0];
-       }else{
-        nodeRelease(RTREE_OF_CURSOR(pCur), pCur->aNode[0]);
-      }
-      pCur->aNode[0] = 0;
-      *pNew = pCur->sPoint;
-    }
-    pCur->sPoint.rScore = rScore;
-    pCur->sPoint.iLevel = iLevel;
-    pCur->bPoint = 1;
-    return &pCur->sPoint;
-  }else{
-    return rtreeEnqueue(pCur, rScore, iLevel);
-  }
-}
+  sqlite3 *db = (sqlite3 *)sqlite3_user_data(p);
+  UErrorCode status = U_ZERO_ERROR;
+  const char *zLocale;      /* Locale identifier - (eg. "jp_JP") */
+  const char *zName;        /* SQL Collation sequence name (eg. "japanese") */
+  UCollator *pUCollator;    /* ICU library collation object */
+  int rc;                   /* Return code from sqlite3_create_collation_x() */
 
-#if 0
-/* Tracing routines for the RtreeSearchPoint queue */
-static void tracePoint(RtreeSearchPoint *p, int idx, RtreeCursor *pCur){
-  if( idx<0 ){ printf(" s"); }else{ printf("%2d", idx); }
-  printf(" %d.%05lld.%02d %g %d",
-    p->iLevel, p->id, p->iCell, p->rScore, p->eWithin
-  );
-  idx++;
-  if( idx<RTREE_CACHE_SZ ){
-    printf(" %p\n", pCur->aNode[idx]);
-  }else{
-    printf("\n");
-  }
-}
-static void traceQueue(RtreeCursor *pCur, const char *zPrefix){
-  int ii;
-  printf("=== %9s ", zPrefix);
-  if( pCur->bPoint ){
-    tracePoint(&pCur->sPoint, -1, pCur);
-  }
-  for(ii=0; ii<pCur->nPoint; ii++){
-    if( ii>0 || pCur->bPoint ) printf("              ");
-    tracePoint(&pCur->aPoint[ii], ii, pCur);
+  assert(nArg==2);
+  (void)nArg; /* Unused parameter */
+  zLocale = (const char *)sqlite3_value_text(apArg[0]);
+  zName = (const char *)sqlite3_value_text(apArg[1]);
+
+  if( !zLocale || !zName ){
+    return;
   }
-}
-# define RTREE_QUEUE_TRACE(A,B) traceQueue(A,B)
-#else
-# define RTREE_QUEUE_TRACE(A,B)   /* no-op */
-#endif
 
-/* Remove the search point with the lowest current score.
-*/
-static void rtreeSearchPointPop(RtreeCursor *p){
-  int i, j, k, n;
-  i = 1 - p->bPoint;
-  assert( i==0 || i==1 );
-  if( p->aNode[i] ){
-    nodeRelease(RTREE_OF_CURSOR(p), p->aNode[i]);
-    p->aNode[i] = 0;
+  pUCollator = ucol_open(zLocale, &status);
+  if( !U_SUCCESS(status) ){
+    icuFunctionError(p, "ucol_open", status);
+    return;
   }
-  if( p->bPoint ){
-    p->anQueue[p->sPoint.iLevel]--;
-    p->bPoint = 0;
-  }else if( p->nPoint ){
-    p->anQueue[p->aPoint[0].iLevel]--;
-    n = --p->nPoint;
-    p->aPoint[0] = p->aPoint[n];
-    if( n<RTREE_CACHE_SZ-1 ){
-      p->aNode[1] = p->aNode[n+1];
-      p->aNode[n+1] = 0;
-    }
-    i = 0;
-    while( (j = i*2+1)<n ){
-      k = j+1;
-      if( k<n && rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[j])<0 ){
-        if( rtreeSearchPointCompare(&p->aPoint[k], &p->aPoint[i])<0 ){
-          rtreeSearchPointSwap(p, i, k);
-          i = k;
-        }else{
-          break;
-        }
-      }else{
-        if( rtreeSearchPointCompare(&p->aPoint[j], &p->aPoint[i])<0 ){
-          rtreeSearchPointSwap(p, i, j);
-          i = j;
-        }else{
-          break;
-        }
-      }
-    }
+  assert(p);
+
+  rc = sqlite3_create_collation_v2(db, zName, SQLITE_UTF16, (void *)pUCollator, 
+      icuCollationColl, icuCollationDel
+  );
+  if( rc!=SQLITE_OK ){
+    ucol_close(pUCollator);
+    sqlite3_result_error(p, "Error registering collation function", -1);
   }
 }
 
-
 /*
-** Continue the search on cursor pCur until the front of the queue
-** contains an entry suitable for returning as a result-set row,
-** or until the RtreeSearchPoint queue is empty, indicating that the
-** query has completed.
+** Register the ICU extension functions with database db.
 */
-static int rtreeStepToLeaf(RtreeCursor *pCur){
-  RtreeSearchPoint *p;
-  Rtree *pRtree = RTREE_OF_CURSOR(pCur);
-  RtreeNode *pNode;
-  int eWithin;
-  int rc = SQLITE_OK;
-  int nCell;
-  int nConstraint = pCur->nConstraint;
-  int ii;
-  int eInt;
-  RtreeSearchPoint x;
+SQLITE_PRIVATE int sqlite3IcuInit(sqlite3 *db){
+  struct IcuScalar {
+    const char *zName;                        /* Function name */
+    int nArg;                                 /* Number of arguments */
+    int enc;                                  /* Optimal text encoding */
+    void *pContext;                           /* sqlite3_user_data() context */
+    void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
+  } scalars[] = {
+    {"regexp", 2, SQLITE_ANY,          0, icuRegexpFunc},
 
-  eInt = pRtree->eCoordType==RTREE_COORD_INT32;
-  while( (p = rtreeSearchPointFirst(pCur))!=0 && p->iLevel>0 ){
-    pNode = rtreeNodeOfFirstSearchPoint(pCur, &rc);
-    if( rc ) return rc;
-    nCell = NCELL(pNode);
-    assert( nCell<200 );
-    while( p->iCell<nCell ){
-      sqlite3_rtree_dbl rScore = (sqlite3_rtree_dbl)-1;
-      u8 *pCellData = pNode->zData + (4+pRtree->nBytesPerCell*p->iCell);
-      eWithin = FULLY_WITHIN;
-      for(ii=0; ii<nConstraint; ii++){
-        RtreeConstraint *pConstraint = pCur->aConstraint + ii;
-        if( pConstraint->op>=RTREE_MATCH ){
-          rc = rtreeCallbackConstraint(pConstraint, eInt, pCellData, p,
-                                       &rScore, &eWithin);
-          if( rc ) return rc;
-        }else if( p->iLevel==1 ){
-          rtreeLeafConstraint(pConstraint, eInt, pCellData, &eWithin);
-        }else{
-          rtreeNonleafConstraint(pConstraint, eInt, pCellData, &eWithin);
-        }
-        if( eWithin==NOT_WITHIN ) break;
-      }
-      p->iCell++;
-      if( eWithin==NOT_WITHIN ) continue;
-      x.iLevel = p->iLevel - 1;
-      if( x.iLevel ){
-        x.id = readInt64(pCellData);
-        x.iCell = 0;
-      }else{
-        x.id = p->id;
-        x.iCell = p->iCell - 1;
-      }
-      if( p->iCell>=nCell ){
-        RTREE_QUEUE_TRACE(pCur, "POP-S:");
-        rtreeSearchPointPop(pCur);
-      }
-      if( rScore<RTREE_ZERO ) rScore = RTREE_ZERO;
-      p = rtreeSearchPointNew(pCur, rScore, x.iLevel);
-      if( p==0 ) return SQLITE_NOMEM;
-      p->eWithin = eWithin;
-      p->id = x.id;
-      p->iCell = x.iCell;
-      RTREE_QUEUE_TRACE(pCur, "PUSH-S:");
-      break;
-    }
-    if( p->iCell>=nCell ){
-      RTREE_QUEUE_TRACE(pCur, "POP-Se:");
-      rtreeSearchPointPop(pCur);
-    }
-  }
-  pCur->atEOF = p==0;
-  return SQLITE_OK;
-}
+    {"lower",  1, SQLITE_UTF16,        0, icuCaseFunc16},
+    {"lower",  2, SQLITE_UTF16,        0, icuCaseFunc16},
+    {"upper",  1, SQLITE_UTF16, (void*)1, icuCaseFunc16},
+    {"upper",  2, SQLITE_UTF16, (void*)1, icuCaseFunc16},
 
-/* 
-** Rtree virtual table module xNext method.
-*/
-static int rtreeNext(sqlite3_vtab_cursor *pVtabCursor){
-  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
-  int rc = SQLITE_OK;
+    {"lower",  1, SQLITE_UTF8,         0, icuCaseFunc16},
+    {"lower",  2, SQLITE_UTF8,         0, icuCaseFunc16},
+    {"upper",  1, SQLITE_UTF8,  (void*)1, icuCaseFunc16},
+    {"upper",  2, SQLITE_UTF8,  (void*)1, icuCaseFunc16},
 
-  /* Move to the next entry that matches the configured constraints. */
-  RTREE_QUEUE_TRACE(pCsr, "POP-Nx:");
-  rtreeSearchPointPop(pCsr);
-  rc = rtreeStepToLeaf(pCsr);
-  return rc;
-}
+    {"like",   2, SQLITE_UTF8,         0, icuLikeFunc},
+    {"like",   3, SQLITE_UTF8,         0, icuLikeFunc},
 
-/* 
-** Rtree virtual table module xRowid method.
-*/
-static int rtreeRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *pRowid){
-  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
-  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
-  int rc = SQLITE_OK;
-  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);
-  if( rc==SQLITE_OK && p ){
-    *pRowid = nodeGetRowid(RTREE_OF_CURSOR(pCsr), pNode, p->iCell);
-  }
-  return rc;
-}
+    {"icu_load_collation",  2, SQLITE_UTF8, (void*)db, icuLoadCollation},
+  };
 
-/* 
-** Rtree virtual table module xColumn method.
-*/
-static int rtreeColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
-  Rtree *pRtree = (Rtree *)cur->pVtab;
-  RtreeCursor *pCsr = (RtreeCursor *)cur;
-  RtreeSearchPoint *p = rtreeSearchPointFirst(pCsr);
-  RtreeCoord c;
   int rc = SQLITE_OK;
-  RtreeNode *pNode = rtreeNodeOfFirstSearchPoint(pCsr, &rc);
+  int i;
 
-  if( rc ) return rc;
-  if( p==0 ) return SQLITE_OK;
-  if( i==0 ){
-    sqlite3_result_int64(ctx, nodeGetRowid(pRtree, pNode, p->iCell));
-  }else{
-    if( rc ) return rc;
-    nodeGetCoord(pRtree, pNode, p->iCell, i-1, &c);
-#ifndef SQLITE_RTREE_INT_ONLY
-    if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
-      sqlite3_result_double(ctx, c.f);
-    }else
-#endif
-    {
-      assert( pRtree->eCoordType==RTREE_COORD_INT32 );
-      sqlite3_result_int(ctx, c.i);
-    }
+  for(i=0; rc==SQLITE_OK && i<(int)(sizeof(scalars)/sizeof(scalars[0])); i++){
+    struct IcuScalar *p = &scalars[i];
+    rc = sqlite3_create_function(
+        db, p->zName, p->nArg, p->enc, p->pContext, p->xFunc, 0, 0
+    );
   }
-  return SQLITE_OK;
+
+  return rc;
 }
 
-/* 
-** Use nodeAcquire() to obtain the leaf node containing the record with 
-** rowid iRowid. If successful, set *ppLeaf to point to the node and
-** return SQLITE_OK. If there is no such record in the table, set
-** *ppLeaf to 0 and return SQLITE_OK. If an error occurs, set *ppLeaf
-** to zero and return an SQLite error code.
-*/
-static int findLeafNode(
-  Rtree *pRtree,              /* RTree to search */
-  i64 iRowid,                 /* The rowid searching for */
-  RtreeNode **ppLeaf,         /* Write the node here */
-  sqlite3_int64 *piNode       /* Write the node-id here */
+#if !SQLITE_CORE
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+SQLITE_API int SQLITE_STDCALL sqlite3_icu_init(
+  sqlite3 *db, 
+  char **pzErrMsg,
+  const sqlite3_api_routines *pApi
 ){
-  int rc;
-  *ppLeaf = 0;
-  sqlite3_bind_int64(pRtree->pReadRowid, 1, iRowid);
-  if( sqlite3_step(pRtree->pReadRowid)==SQLITE_ROW ){
-    i64 iNode = sqlite3_column_int64(pRtree->pReadRowid, 0);
-    if( piNode ) *piNode = iNode;
-    rc = nodeAcquire(pRtree, iNode, 0, ppLeaf);
-    sqlite3_reset(pRtree->pReadRowid);
-  }else{
-    rc = sqlite3_reset(pRtree->pReadRowid);
-  }
-  return rc;
+  SQLITE_EXTENSION_INIT2(pApi)
+  return sqlite3IcuInit(db);
 }
+#endif
+
+#endif
 
+/************** End of icu.c *************************************************/
+/************** Begin file fts3_icu.c ****************************************/
 /*
-** This function is called to configure the RtreeConstraint object passed
-** as the second argument for a MATCH constraint. The value passed as the
-** first argument to this function is the right-hand operand to the MATCH
-** operator.
+** 2007 June 22
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file implements a tokenizer for fts3 based on the ICU library.
 */
-static int deserializeGeometry(sqlite3_value *pValue, RtreeConstraint *pCons){
-  RtreeMatchArg *pBlob;              /* BLOB returned by geometry function */
-  sqlite3_rtree_query_info *pInfo;   /* Callback information */
-  int nBlob;                         /* Size of the geometry function blob */
-  int nExpected;                     /* Expected size of the BLOB */
+/* #include "fts3Int.h" */
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
+#ifdef SQLITE_ENABLE_ICU
 
-  /* Check that value is actually a blob. */
-  if( sqlite3_value_type(pValue)!=SQLITE_BLOB ) return SQLITE_ERROR;
+/* #include <assert.h> */
+/* #include <string.h> */
+/* #include "fts3_tokenizer.h" */
 
-  /* Check that the blob is roughly the right size. */
-  nBlob = sqlite3_value_bytes(pValue);
-  if( nBlob<(int)sizeof(RtreeMatchArg) 
-   || ((nBlob-sizeof(RtreeMatchArg))%sizeof(RtreeDValue))!=0
-  ){
-    return SQLITE_ERROR;
-  }
+#include <unicode/ubrk.h>
+/* #include <unicode/ucol.h> */
+/* #include <unicode/ustring.h> */
+#include <unicode/utf16.h>
 
-  pInfo = (sqlite3_rtree_query_info*)sqlite3_malloc( sizeof(*pInfo)+nBlob );
-  if( !pInfo ) return SQLITE_NOMEM;
-  memset(pInfo, 0, sizeof(*pInfo));
-  pBlob = (RtreeMatchArg*)&pInfo[1];
+typedef struct IcuTokenizer IcuTokenizer;
+typedef struct IcuCursor IcuCursor;
 
-  memcpy(pBlob, sqlite3_value_blob(pValue), nBlob);
-  nExpected = (int)(sizeof(RtreeMatchArg) +
-                    (pBlob->nParam-1)*sizeof(RtreeDValue));
-  if( pBlob->magic!=RTREE_GEOMETRY_MAGIC || nBlob!=nExpected ){
-    sqlite3_free(pInfo);
-    return SQLITE_ERROR;
-  }
-  pInfo->pContext = pBlob->cb.pContext;
-  pInfo->nParam = pBlob->nParam;
-  pInfo->aParam = pBlob->aParam;
+struct IcuTokenizer {
+  sqlite3_tokenizer base;
+  char *zLocale;
+};
 
-  if( pBlob->cb.xGeom ){
-    pCons->u.xGeom = pBlob->cb.xGeom;
-  }else{
-    pCons->op = RTREE_QUERY;
-    pCons->u.xQueryFunc = pBlob->cb.xQueryFunc;
-  }
-  pCons->pInfo = pInfo;
-  return SQLITE_OK;
-}
+struct IcuCursor {
+  sqlite3_tokenizer_cursor base;
 
-/* 
-** Rtree virtual table module xFilter method.
+  UBreakIterator *pIter;      /* ICU break-iterator object */
+  int nChar;                  /* Number of UChar elements in pInput */
+  UChar *aChar;               /* Copy of input using utf-16 encoding */
+  int *aOffset;               /* Offsets of each character in utf-8 input */
+
+  int nBuffer;
+  char *zBuffer;
+
+  int iToken;
+};
+
+/*
+** Create a new tokenizer instance.
 */
-static int rtreeFilter(
-  sqlite3_vtab_cursor *pVtabCursor, 
-  int idxNum, const char *idxStr,
-  int argc, sqlite3_value **argv
+static int icuCreate(
+  int argc,                            /* Number of entries in argv[] */
+  const char * const *argv,            /* Tokenizer creation arguments */
+  sqlite3_tokenizer **ppTokenizer      /* OUT: Created tokenizer */
 ){
-  Rtree *pRtree = (Rtree *)pVtabCursor->pVtab;
-  RtreeCursor *pCsr = (RtreeCursor *)pVtabCursor;
-  RtreeNode *pRoot = 0;
-  int ii;
-  int rc = SQLITE_OK;
-  int iCell = 0;
-
-  rtreeReference(pRtree);
+  IcuTokenizer *p;
+  int n = 0;
 
-  /* Reset the cursor to the same state as rtreeOpen() leaves it in. */
-  freeCursorConstraints(pCsr);
-  sqlite3_free(pCsr->aPoint);
-  memset(pCsr, 0, sizeof(RtreeCursor));
-  pCsr->base.pVtab = (sqlite3_vtab*)pRtree;
+  if( argc>0 ){
+    n = strlen(argv[0])+1;
+  }
+  p = (IcuTokenizer *)sqlite3_malloc(sizeof(IcuTokenizer)+n);
+  if( !p ){
+    return SQLITE_NOMEM;
+  }
+  memset(p, 0, sizeof(IcuTokenizer));
 
-  pCsr->iStrategy = idxNum;
-  if( idxNum==1 ){
-    /* Special case - lookup by rowid. */
-    RtreeNode *pLeaf;        /* Leaf on which the required cell resides */
-    RtreeSearchPoint *p;     /* Search point for the the leaf */
-    i64 iRowid = sqlite3_value_int64(argv[0]);
-    i64 iNode = 0;
-    rc = findLeafNode(pRtree, iRowid, &pLeaf, &iNode);
-    if( rc==SQLITE_OK && pLeaf!=0 ){
-      p = rtreeSearchPointNew(pCsr, RTREE_ZERO, 0);
-      assert( p!=0 );  /* Always returns pCsr->sPoint */
-      pCsr->aNode[0] = pLeaf;
-      p->id = iNode;
-      p->eWithin = PARTLY_WITHIN;
-      rc = nodeRowidIndex(pRtree, pLeaf, iRowid, &iCell);
-      p->iCell = iCell;
-      RTREE_QUEUE_TRACE(pCsr, "PUSH-F1:");
-    }else{
-      pCsr->atEOF = 1;
-    }
-  }else{
-    /* Normal case - r-tree scan. Set up the RtreeCursor.aConstraint array 
-    ** with the configured constraints. 
-    */
-    rc = nodeAcquire(pRtree, 1, 0, &pRoot);
-    if( rc==SQLITE_OK && argc>0 ){
-      pCsr->aConstraint = sqlite3_malloc(sizeof(RtreeConstraint)*argc);
-      pCsr->nConstraint = argc;
-      if( !pCsr->aConstraint ){
-        rc = SQLITE_NOMEM;
-      }else{
-        memset(pCsr->aConstraint, 0, sizeof(RtreeConstraint)*argc);
-        memset(pCsr->anQueue, 0, sizeof(u32)*(pRtree->iDepth + 1));
-        assert( (idxStr==0 && argc==0)
-                || (idxStr && (int)strlen(idxStr)==argc*2) );
-        for(ii=0; ii<argc; ii++){
-          RtreeConstraint *p = &pCsr->aConstraint[ii];
-          p->op = idxStr[ii*2];
-          p->iCoord = idxStr[ii*2+1]-'0';
-          if( p->op>=RTREE_MATCH ){
-            /* A MATCH operator. The right-hand-side must be a blob that
-            ** can be cast into an RtreeMatchArg object. One created using
-            ** an sqlite3_rtree_geometry_callback() SQL user function.
-            */
-            rc = deserializeGeometry(argv[ii], p);
-            if( rc!=SQLITE_OK ){
-              break;
-            }
-            p->pInfo->nCoord = pRtree->nDim*2;
-            p->pInfo->anQueue = pCsr->anQueue;
-            p->pInfo->mxLevel = pRtree->iDepth + 1;
-          }else{
-#ifdef SQLITE_RTREE_INT_ONLY
-            p->u.rValue = sqlite3_value_int64(argv[ii]);
-#else
-            p->u.rValue = sqlite3_value_double(argv[ii]);
-#endif
-          }
-        }
-      }
-    }
-    if( rc==SQLITE_OK ){
-      RtreeSearchPoint *pNew;
-      pNew = rtreeSearchPointNew(pCsr, RTREE_ZERO, pRtree->iDepth+1);
-      if( pNew==0 ) return SQLITE_NOMEM;
-      pNew->id = 1;
-      pNew->iCell = 0;
-      pNew->eWithin = PARTLY_WITHIN;
-      assert( pCsr->bPoint==1 );
-      pCsr->aNode[0] = pRoot;
-      pRoot = 0;
-      RTREE_QUEUE_TRACE(pCsr, "PUSH-Fm:");
-      rc = rtreeStepToLeaf(pCsr);
-    }
+  if( n ){
+    p->zLocale = (char *)&p[1];
+    memcpy(p->zLocale, argv[0], n);
   }
 
-  nodeRelease(pRtree, pRoot);
-  rtreeRelease(pRtree);
-  return rc;
+  *ppTokenizer = (sqlite3_tokenizer *)p;
+
+  return SQLITE_OK;
 }
 
 /*
-** Set the pIdxInfo->estimatedRows variable to nRow. Unless this
-** extension is currently being used by a version of SQLite too old to
-** support estimatedRows. In that case this function is a no-op.
+** Destroy a tokenizer
 */
-static void setEstimatedRows(sqlite3_index_info *pIdxInfo, i64 nRow){
-#if SQLITE_VERSION_NUMBER>=3008002
-  if( sqlite3_libversion_number()>=3008002 ){
-    pIdxInfo->estimatedRows = nRow;
-  }
-#endif
+static int icuDestroy(sqlite3_tokenizer *pTokenizer){
+  IcuTokenizer *p = (IcuTokenizer *)pTokenizer;
+  sqlite3_free(p);
+  return SQLITE_OK;
 }
 
 /*
-** Rtree virtual table module xBestIndex method. There are three
-** table scan strategies to choose from (in order from most to 
-** least desirable):
-**
-**   idxNum     idxStr        Strategy
-**   ------------------------------------------------
-**     1        Unused        Direct lookup by rowid.
-**     2        See below     R-tree query or full-table scan.
-**   ------------------------------------------------
-**
-** If strategy 1 is used, then idxStr is not meaningful. If strategy
-** 2 is used, idxStr is formatted to contain 2 bytes for each 
-** constraint used. The first two bytes of idxStr correspond to 
-** the constraint in sqlite3_index_info.aConstraintUsage[] with
-** (argvIndex==1) etc.
-**
-** The first of each pair of bytes in idxStr identifies the constraint
-** operator as follows:
-**
-**   Operator    Byte Value
-**   ----------------------
-**      =        0x41 ('A')
-**     <=        0x42 ('B')
-**      <        0x43 ('C')
-**     >=        0x44 ('D')
-**      >        0x45 ('E')
-**   MATCH       0x46 ('F')
-**   ----------------------
-**
-** The second of each pair of bytes identifies the coordinate column
-** to which the constraint applies. The leftmost coordinate column
-** is 'a', the second from the left 'b' etc.
+** Prepare to begin tokenizing a particular string.  The input
+** string to be tokenized is pInput[0..nBytes-1].  A cursor
+** used to incrementally tokenize this string is returned in 
+** *ppCursor.
 */
-static int rtreeBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
-  Rtree *pRtree = (Rtree*)tab;
-  int rc = SQLITE_OK;
-  int ii;
-  i64 nRow;                       /* Estimated rows returned by this scan */
+static int icuOpen(
+  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
+  const char *zInput,                    /* Input string */
+  int nInput,                            /* Length of zInput in bytes */
+  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
+){
+  IcuTokenizer *p = (IcuTokenizer *)pTokenizer;
+  IcuCursor *pCsr;
 
-  int iIdx = 0;
-  char zIdxStr[RTREE_MAX_DIMENSIONS*8+1];
-  memset(zIdxStr, 0, sizeof(zIdxStr));
+  const int32_t opt = U_FOLD_CASE_DEFAULT;
+  UErrorCode status = U_ZERO_ERROR;
+  int nChar;
 
-  assert( pIdxInfo->idxStr==0 );
-  for(ii=0; ii<pIdxInfo->nConstraint && iIdx<(int)(sizeof(zIdxStr)-1); ii++){
-    struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[ii];
+  UChar32 c;
+  int iInput = 0;
+  int iOut = 0;
 
-    if( p->usable && p->iColumn==0 && p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
-      /* We have an equality constraint on the rowid. Use strategy 1. */
-      int jj;
-      for(jj=0; jj<ii; jj++){
-        pIdxInfo->aConstraintUsage[jj].argvIndex = 0;
-        pIdxInfo->aConstraintUsage[jj].omit = 0;
-      }
-      pIdxInfo->idxNum = 1;
-      pIdxInfo->aConstraintUsage[ii].argvIndex = 1;
-      pIdxInfo->aConstraintUsage[jj].omit = 1;
+  *ppCursor = 0;
 
-      /* This strategy involves a two rowid lookups on an B-Tree structures
-      ** and then a linear search of an R-Tree node. This should be 
-      ** considered almost as quick as a direct rowid lookup (for which 
-      ** sqlite uses an internal cost of 0.0). It is expected to return
-      ** a single row.
-      */ 
-      pIdxInfo->estimatedCost = 30.0;
-      setEstimatedRows(pIdxInfo, 1);
-      return SQLITE_OK;
+  if( zInput==0 ){
+    nInput = 0;
+    zInput = "";
+  }else if( nInput<0 ){
+    nInput = strlen(zInput);
+  }
+  nChar = nInput+1;
+  pCsr = (IcuCursor *)sqlite3_malloc(
+      sizeof(IcuCursor) +                /* IcuCursor */
+      ((nChar+3)&~3) * sizeof(UChar) +   /* IcuCursor.aChar[] */
+      (nChar+1) * sizeof(int)            /* IcuCursor.aOffset[] */
+  );
+  if( !pCsr ){
+    return SQLITE_NOMEM;
+  }
+  memset(pCsr, 0, sizeof(IcuCursor));
+  pCsr->aChar = (UChar *)&pCsr[1];
+  pCsr->aOffset = (int *)&pCsr->aChar[(nChar+3)&~3];
+
+  pCsr->aOffset[iOut] = iInput;
+  U8_NEXT(zInput, iInput, nInput, c); 
+  while( c>0 ){
+    int isError = 0;
+    c = u_foldCase(c, opt);
+    U16_APPEND(pCsr->aChar, iOut, nChar, c, isError);
+    if( isError ){
+      sqlite3_free(pCsr);
+      return SQLITE_ERROR;
     }
+    pCsr->aOffset[iOut] = iInput;
 
-    if( p->usable && (p->iColumn>0 || p->op==SQLITE_INDEX_CONSTRAINT_MATCH) ){
-      u8 op;
-      switch( p->op ){
-        case SQLITE_INDEX_CONSTRAINT_EQ: op = RTREE_EQ; break;
-        case SQLITE_INDEX_CONSTRAINT_GT: op = RTREE_GT; break;
-        case SQLITE_INDEX_CONSTRAINT_LE: op = RTREE_LE; break;
-        case SQLITE_INDEX_CONSTRAINT_LT: op = RTREE_LT; break;
-        case SQLITE_INDEX_CONSTRAINT_GE: op = RTREE_GE; break;
-        default:
-          assert( p->op==SQLITE_INDEX_CONSTRAINT_MATCH );
-          op = RTREE_MATCH; 
-          break;
-      }
-      zIdxStr[iIdx++] = op;
-      zIdxStr[iIdx++] = p->iColumn - 1 + '0';
-      pIdxInfo->aConstraintUsage[ii].argvIndex = (iIdx/2);
-      pIdxInfo->aConstraintUsage[ii].omit = 1;
+    if( iInput<nInput ){
+      U8_NEXT(zInput, iInput, nInput, c);
+    }else{
+      c = 0;
     }
   }
 
-  pIdxInfo->idxNum = 2;
-  pIdxInfo->needToFreeIdxStr = 1;
-  if( iIdx>0 && 0==(pIdxInfo->idxStr = sqlite3_mprintf("%s", zIdxStr)) ){
-    return SQLITE_NOMEM;
+  pCsr->pIter = ubrk_open(UBRK_WORD, p->zLocale, pCsr->aChar, iOut, &status);
+  if( !U_SUCCESS(status) ){
+    sqlite3_free(pCsr);
+    return SQLITE_ERROR;
   }
+  pCsr->nChar = iOut;
 
-  nRow = pRtree->nRowEst / (iIdx + 1);
-  pIdxInfo->estimatedCost = (double)6.0 * (double)nRow;
-  setEstimatedRows(pIdxInfo, nRow);
-
-  return rc;
+  ubrk_first(pCsr->pIter);
+  *ppCursor = (sqlite3_tokenizer_cursor *)pCsr;
+  return SQLITE_OK;
 }
 
 /*
-** Return the N-dimensional volumn of the cell stored in *p.
+** Close a tokenization cursor previously opened by a call to icuOpen().
 */
-static RtreeDValue cellArea(Rtree *pRtree, RtreeCell *p){
-  RtreeDValue area = (RtreeDValue)1;
-  int ii;
-  for(ii=0; ii<(pRtree->nDim*2); ii+=2){
-    area = (area * (DCOORD(p->aCoord[ii+1]) - DCOORD(p->aCoord[ii])));
-  }
-  return area;
+static int icuClose(sqlite3_tokenizer_cursor *pCursor){
+  IcuCursor *pCsr = (IcuCursor *)pCursor;
+  ubrk_close(pCsr->pIter);
+  sqlite3_free(pCsr->zBuffer);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
 }
 
 /*
-** Return the margin length of cell p. The margin length is the sum
-** of the objects size in each dimension.
+** Extract the next token from a tokenization cursor.
 */
-static RtreeDValue cellMargin(Rtree *pRtree, RtreeCell *p){
-  RtreeDValue margin = (RtreeDValue)0;
-  int ii;
-  for(ii=0; ii<(pRtree->nDim*2); ii+=2){
-    margin += (DCOORD(p->aCoord[ii+1]) - DCOORD(p->aCoord[ii]));
-  }
-  return margin;
-}
+static int icuNext(
+  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
+  const char **ppToken,               /* OUT: *ppToken is the token text */
+  int *pnBytes,                       /* OUT: Number of bytes in token */
+  int *piStartOffset,                 /* OUT: Starting offset of token */
+  int *piEndOffset,                   /* OUT: Ending offset of token */
+  int *piPosition                     /* OUT: Position integer of token */
+){
+  IcuCursor *pCsr = (IcuCursor *)pCursor;
 
-/*
-** Store the union of cells p1 and p2 in p1.
-*/
-static void cellUnion(Rtree *pRtree, RtreeCell *p1, RtreeCell *p2){
-  int ii;
-  if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
-    for(ii=0; ii<(pRtree->nDim*2); ii+=2){
-      p1->aCoord[ii].f = MIN(p1->aCoord[ii].f, p2->aCoord[ii].f);
-      p1->aCoord[ii+1].f = MAX(p1->aCoord[ii+1].f, p2->aCoord[ii+1].f);
+  int iStart = 0;
+  int iEnd = 0;
+  int nByte = 0;
+
+  while( iStart==iEnd ){
+    UChar32 c;
+
+    iStart = ubrk_current(pCsr->pIter);
+    iEnd = ubrk_next(pCsr->pIter);
+    if( iEnd==UBRK_DONE ){
+      return SQLITE_DONE;
     }
-  }else{
-    for(ii=0; ii<(pRtree->nDim*2); ii+=2){
-      p1->aCoord[ii].i = MIN(p1->aCoord[ii].i, p2->aCoord[ii].i);
-      p1->aCoord[ii+1].i = MAX(p1->aCoord[ii+1].i, p2->aCoord[ii+1].i);
+
+    while( iStart<iEnd ){
+      int iWhite = iStart;
+      U16_NEXT(pCsr->aChar, iWhite, pCsr->nChar, c);
+      if( u_isspace(c) ){
+        iStart = iWhite;
+      }else{
+        break;
+      }
     }
+    assert(iStart<=iEnd);
   }
-}
 
-/*
-** Return true if the area covered by p2 is a subset of the area covered
-** by p1. False otherwise.
-*/
-static int cellContains(Rtree *pRtree, RtreeCell *p1, RtreeCell *p2){
-  int ii;
-  int isInt = (pRtree->eCoordType==RTREE_COORD_INT32);
-  for(ii=0; ii<(pRtree->nDim*2); ii+=2){
-    RtreeCoord *a1 = &p1->aCoord[ii];
-    RtreeCoord *a2 = &p2->aCoord[ii];
-    if( (!isInt && (a2[0].f<a1[0].f || a2[1].f>a1[1].f)) 
-     || ( isInt && (a2[0].i<a1[0].i || a2[1].i>a1[1].i)) 
-    ){
-      return 0;
+  do {
+    UErrorCode status = U_ZERO_ERROR;
+    if( nByte ){
+      char *zNew = sqlite3_realloc(pCsr->zBuffer, nByte);
+      if( !zNew ){
+        return SQLITE_NOMEM;
+      }
+      pCsr->zBuffer = zNew;
+      pCsr->nBuffer = nByte;
     }
-  }
-  return 1;
+
+    u_strToUTF8(
+        pCsr->zBuffer, pCsr->nBuffer, &nByte,    /* Output vars */
+        &pCsr->aChar[iStart], iEnd-iStart,       /* Input vars */
+        &status                                  /* Output success/failure */
+    );
+  } while( nByte>pCsr->nBuffer );
+
+  *ppToken = pCsr->zBuffer;
+  *pnBytes = nByte;
+  *piStartOffset = pCsr->aOffset[iStart];
+  *piEndOffset = pCsr->aOffset[iEnd];
+  *piPosition = pCsr->iToken++;
+
+  return SQLITE_OK;
 }
 
 /*
-** Return the amount cell p would grow by if it were unioned with pCell.
+** The set of routines that implement the simple tokenizer
 */
-static RtreeDValue cellGrowth(Rtree *pRtree, RtreeCell *p, RtreeCell *pCell){
-  RtreeDValue area;
-  RtreeCell cell;
-  memcpy(&cell, p, sizeof(RtreeCell));
-  area = cellArea(pRtree, &cell);
-  cellUnion(pRtree, &cell, pCell);
-  return (cellArea(pRtree, &cell)-area);
-}
+static const sqlite3_tokenizer_module icuTokenizerModule = {
+  0,                           /* iVersion    */
+  icuCreate,                   /* xCreate     */
+  icuDestroy,                  /* xCreate     */
+  icuOpen,                     /* xOpen       */
+  icuClose,                    /* xClose      */
+  icuNext,                     /* xNext       */
+  0,                           /* xLanguageid */
+};
 
-static RtreeDValue cellOverlap(
-  Rtree *pRtree, 
-  RtreeCell *p, 
-  RtreeCell *aCell, 
-  int nCell
+/*
+** Set *ppModule to point at the implementation of the ICU tokenizer.
+*/
+SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(
+  sqlite3_tokenizer_module const**ppModule
 ){
-  int ii;
-  RtreeDValue overlap = RTREE_ZERO;
-  for(ii=0; ii<nCell; ii++){
-    int jj;
-    RtreeDValue o = (RtreeDValue)1;
-    for(jj=0; jj<(pRtree->nDim*2); jj+=2){
-      RtreeDValue x1, x2;
-      x1 = MAX(DCOORD(p->aCoord[jj]), DCOORD(aCell[ii].aCoord[jj]));
-      x2 = MIN(DCOORD(p->aCoord[jj+1]), DCOORD(aCell[ii].aCoord[jj+1]));
-      if( x2<x1 ){
-        o = (RtreeDValue)0;
-        break;
-      }else{
-        o = o * (x2-x1);
-      }
-    }
-    overlap += o;
-  }
-  return overlap;
+  *ppModule = &icuTokenizerModule;
 }
 
+#endif /* defined(SQLITE_ENABLE_ICU) */
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
 
+/************** End of fts3_icu.c ********************************************/
+/************** Begin file sqlite3rbu.c **************************************/
 /*
-** This function implements the ChooseLeaf algorithm from Gutman[84].
-** ChooseSubTree in r*tree terminology.
+** 2014 August 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+**
+** OVERVIEW 
+**
+**  The RBU extension requires that the RBU update be packaged as an
+**  SQLite database. The tables it expects to find are described in
+**  sqlite3rbu.h.  Essentially, for each table xyz in the target database
+**  that the user wishes to write to, a corresponding data_xyz table is
+**  created in the RBU database and populated with one row for each row to
+**  update, insert or delete from the target table.
+** 
+**  The update proceeds in three stages:
+** 
+**  1) The database is updated. The modified database pages are written
+**     to a *-oal file. A *-oal file is just like a *-wal file, except
+**     that it is named "<database>-oal" instead of "<database>-wal".
+**     Because regular SQLite clients do not look for file named
+**     "<database>-oal", they go on using the original database in
+**     rollback mode while the *-oal file is being generated.
+** 
+**     During this stage RBU does not update the database by writing
+**     directly to the target tables. Instead it creates "imposter"
+**     tables using the SQLITE_TESTCTRL_IMPOSTER interface that it uses
+**     to update each b-tree individually. All updates required by each
+**     b-tree are completed before moving on to the next, and all
+**     updates are done in sorted key order.
+** 
+**  2) The "<database>-oal" file is moved to the equivalent "<database>-wal"
+**     location using a call to rename(2). Before doing this the RBU
+**     module takes an EXCLUSIVE lock on the database file, ensuring
+**     that there are no other active readers.
+** 
+**     Once the EXCLUSIVE lock is released, any other database readers
+**     detect the new *-wal file and read the database in wal mode. At
+**     this point they see the new version of the database - including
+**     the updates made as part of the RBU update.
+** 
+**  3) The new *-wal file is checkpointed. This proceeds in the same way 
+**     as a regular database checkpoint, except that a single frame is
+**     checkpointed each time sqlite3rbu_step() is called. If the RBU
+**     handle is closed before the entire *-wal file is checkpointed,
+**     the checkpoint progress is saved in the RBU database and the
+**     checkpoint can be resumed by another RBU client at some point in
+**     the future.
+**
+** POTENTIAL PROBLEMS
+** 
+**  The rename() call might not be portable. And RBU is not currently
+**  syncing the directory after renaming the file.
+**
+**  When state is saved, any commit to the *-oal file and the commit to
+**  the RBU update database are not atomic. So if the power fails at the
+**  wrong moment they might get out of sync. As the main database will be
+**  committed before the RBU update database this will likely either just
+**  pass unnoticed, or result in SQLITE_CONSTRAINT errors (due to UNIQUE
+**  constraint violations).
+**
+**  If some client does modify the target database mid RBU update, or some
+**  other error occurs, the RBU extension will keep throwing errors. It's
+**  not really clear how to get out of this state. The system could just
+**  by delete the RBU update database and *-oal file and have the device
+**  download the update again and start over.
+**
+**  At present, for an UPDATE, both the new.* and old.* records are
+**  collected in the rbu_xyz table. And for both UPDATEs and DELETEs all
+**  fields are collected.  This means we're probably writing a lot more
+**  data to disk when saving the state of an ongoing update to the RBU
+**  update database than is strictly necessary.
+** 
 */
-static int ChooseLeaf(
-  Rtree *pRtree,               /* Rtree table */
-  RtreeCell *pCell,            /* Cell to insert into rtree */
-  int iHeight,                 /* Height of sub-tree rooted at pCell */
-  RtreeNode **ppLeaf           /* OUT: Selected leaf page */
-){
-  int rc;
-  int ii;
-  RtreeNode *pNode;
-  rc = nodeAcquire(pRtree, 1, 0, &pNode);
 
-  for(ii=0; rc==SQLITE_OK && ii<(pRtree->iDepth-iHeight); ii++){
-    int iCell;
-    sqlite3_int64 iBest = 0;
+/* #include <assert.h> */
+/* #include <string.h> */
+/* #include <stdio.h> */
 
-    RtreeDValue fMinGrowth = RTREE_ZERO;
-    RtreeDValue fMinArea = RTREE_ZERO;
+#if !defined(_WIN32)
+/* #  include <unistd.h> */
+#endif
 
-    int nCell = NCELL(pNode);
-    RtreeCell cell;
-    RtreeNode *pChild;
+/* #include "sqlite3.h" */
 
-    RtreeCell *aCell = 0;
+#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RBU)
+/************** Include sqlite3rbu.h in the middle of sqlite3rbu.c ***********/
+/************** Begin file sqlite3rbu.h **************************************/
+/*
+** 2014 August 30
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains the public interface for the RBU extension. 
+*/
 
-    /* Select the child node which will be enlarged the least if pCell
-    ** is inserted into it. Resolve ties by choosing the entry with
-    ** the smallest area.
-    */
-    for(iCell=0; iCell<nCell; iCell++){
-      int bBest = 0;
-      RtreeDValue growth;
-      RtreeDValue area;
-      nodeGetCell(pRtree, pNode, iCell, &cell);
-      growth = cellGrowth(pRtree, &cell, pCell);
-      area = cellArea(pRtree, &cell);
-      if( iCell==0||growth<fMinGrowth||(growth==fMinGrowth && area<fMinArea) ){
-        bBest = 1;
-      }
-      if( bBest ){
-        fMinGrowth = growth;
-        fMinArea = area;
-        iBest = cell.iRowid;
-      }
-    }
+/*
+** SUMMARY
+**
+** Writing a transaction containing a large number of operations on 
+** b-tree indexes that are collectively larger than the available cache
+** memory can be very inefficient. 
+**
+** The problem is that in order to update a b-tree, the leaf page (at least)
+** containing the entry being inserted or deleted must be modified. If the
+** working set of leaves is larger than the available cache memory, then a 
+** single leaf that is modified more than once as part of the transaction 
+** may be loaded from or written to the persistent media multiple times.
+** Additionally, because the index updates are likely to be applied in
+** random order, access to pages within the database is also likely to be in 
+** random order, which is itself quite inefficient.
+**
+** One way to improve the situation is to sort the operations on each index
+** by index key before applying them to the b-tree. This leads to an IO
+** pattern that resembles a single linear scan through the index b-tree,
+** and all but guarantees each modified leaf page is loaded and stored 
+** exactly once. SQLite uses this trick to improve the performance of
+** CREATE INDEX commands. This extension allows it to be used to improve
+** the performance of large transactions on existing databases.
+**
+** Additionally, this extension allows the work involved in writing the 
+** large transaction to be broken down into sub-transactions performed 
+** sequentially by separate processes. This is useful if the system cannot 
+** guarantee that a single update process will run for long enough to apply 
+** the entire update, for example because the update is being applied on a 
+** mobile device that is frequently rebooted. Even after the writer process 
+** has committed one or more sub-transactions, other database clients continue
+** to read from the original database snapshot. In other words, partially 
+** applied transactions are not visible to other clients. 
+**
+** "RBU" stands for "Resumable Bulk Update". As in a large database update
+** transmitted via a wireless network to a mobile device. A transaction
+** applied using this extension is hence refered to as an "RBU update".
+**
+**
+** LIMITATIONS
+**
+** An "RBU update" transaction is subject to the following limitations:
+**
+**   * The transaction must consist of INSERT, UPDATE and DELETE operations
+**     only.
+**
+**   * INSERT statements may not use any default values.
+**
+**   * UPDATE and DELETE statements must identify their target rows by 
+**     non-NULL PRIMARY KEY values. Rows with NULL values stored in PRIMARY
+**     KEY fields may not be updated or deleted. If the table being written 
+**     has no PRIMARY KEY, affected rows must be identified by rowid.
+**
+**   * UPDATE statements may not modify PRIMARY KEY columns.
+**
+**   * No triggers will be fired.
+**
+**   * No foreign key violations are detected or reported.
+**
+**   * CHECK constraints are not enforced.
+**
+**   * No constraint handling mode except for "OR ROLLBACK" is supported.
+**
+**
+** PREPARATION
+**
+** An "RBU update" is stored as a separate SQLite database. A database
+** containing an RBU update is an "RBU database". For each table in the 
+** target database to be updated, the RBU database should contain a table
+** named "data_<target name>" containing the same set of columns as the
+** target table, and one more - "rbu_control". The data_% table should 
+** have no PRIMARY KEY or UNIQUE constraints, but each column should have
+** the same type as the corresponding column in the target database.
+** The "rbu_control" column should have no type at all. For example, if
+** the target database contains:
+**
+**   CREATE TABLE t1(a INTEGER PRIMARY KEY, b TEXT, c UNIQUE);
+**
+** Then the RBU database should contain:
+**
+**   CREATE TABLE data_t1(a INTEGER, b TEXT, c, rbu_control);
+**
+** The order of the columns in the data_% table does not matter.
+**
+** If the target database table is a virtual table or a table that has no
+** PRIMARY KEY declaration, the data_% table must also contain a column 
+** named "rbu_rowid". This column is mapped to the tables implicit primary 
+** key column - "rowid". Virtual tables for which the "rowid" column does 
+** not function like a primary key value cannot be updated using RBU. For 
+** example, if the target db contains either of the following:
+**
+**   CREATE VIRTUAL TABLE x1 USING fts3(a, b);
+**   CREATE TABLE x1(a, b)
+**
+** then the RBU database should contain:
+**
+**   CREATE TABLE data_x1(a, b, rbu_rowid, rbu_control);
+**
+** All non-hidden columns (i.e. all columns matched by "SELECT *") of the
+** target table must be present in the input table. For virtual tables,
+** hidden columns are optional - they are updated by RBU if present in
+** the input table, or not otherwise. For example, to write to an fts4
+** table with a hidden languageid column such as:
+**
+**   CREATE VIRTUAL TABLE ft1 USING fts4(a, b, languageid='langid');
+**
+** Either of the following input table schemas may be used:
+**
+**   CREATE TABLE data_ft1(a, b, langid, rbu_rowid, rbu_control);
+**   CREATE TABLE data_ft1(a, b, rbu_rowid, rbu_control);
+**
+** For each row to INSERT into the target database as part of the RBU 
+** update, the corresponding data_% table should contain a single record
+** with the "rbu_control" column set to contain integer value 0. The
+** other columns should be set to the values that make up the new record 
+** to insert. 
+**
+** If the target database table has an INTEGER PRIMARY KEY, it is not 
+** possible to insert a NULL value into the IPK column. Attempting to 
+** do so results in an SQLITE_MISMATCH error.
+**
+** For each row to DELETE from the target database as part of the RBU 
+** update, the corresponding data_% table should contain a single record
+** with the "rbu_control" column set to contain integer value 1. The
+** real primary key values of the row to delete should be stored in the
+** corresponding columns of the data_% table. The values stored in the
+** other columns are not used.
+**
+** For each row to UPDATE from the target database as part of the RBU 
+** update, the corresponding data_% table should contain a single record
+** with the "rbu_control" column set to contain a value of type text.
+** The real primary key values identifying the row to update should be 
+** stored in the corresponding columns of the data_% table row, as should
+** the new values of all columns being update. The text value in the 
+** "rbu_control" column must contain the same number of characters as
+** there are columns in the target database table, and must consist entirely
+** of 'x' and '.' characters (or in some special cases 'd' - see below). For 
+** each column that is being updated, the corresponding character is set to
+** 'x'. For those that remain as they are, the corresponding character of the
+** rbu_control value should be set to '.'. For example, given the tables 
+** above, the update statement:
+**
+**   UPDATE t1 SET c = 'usa' WHERE a = 4;
+**
+** is represented by the data_t1 row created by:
+**
+**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..x');
+**
+** Instead of an 'x' character, characters of the rbu_control value specified
+** for UPDATEs may also be set to 'd'. In this case, instead of updating the
+** target table with the value stored in the corresponding data_% column, the
+** user-defined SQL function "rbu_delta()" is invoked and the result stored in
+** the target table column. rbu_delta() is invoked with two arguments - the
+** original value currently stored in the target table column and the 
+** value specified in the data_xxx table.
+**
+** For example, this row:
+**
+**   INSERT INTO data_t1(a, b, c, rbu_control) VALUES(4, NULL, 'usa', '..d');
+**
+** is similar to an UPDATE statement such as: 
+**
+**   UPDATE t1 SET c = rbu_delta(c, 'usa') WHERE a = 4;
+**
+** If the target database table is a virtual table or a table with no PRIMARY
+** KEY, the rbu_control value should not include a character corresponding 
+** to the rbu_rowid value. For example, this:
+**
+**   INSERT INTO data_ft1(a, b, rbu_rowid, rbu_control) 
+**       VALUES(NULL, 'usa', 12, '.x');
+**
+** causes a result similar to:
+**
+**   UPDATE ft1 SET b = 'usa' WHERE rowid = 12;
+**
+** The data_xxx tables themselves should have no PRIMARY KEY declarations.
+** However, RBU is more efficient if reading the rows in from each data_xxx
+** table in "rowid" order is roughly the same as reading them sorted by
+** the PRIMARY KEY of the corresponding target database table. In other 
+** words, rows should be sorted using the destination table PRIMARY KEY 
+** fields before they are inserted into the data_xxx tables.
+**
+** USAGE
+**
+** The API declared below allows an application to apply an RBU update 
+** stored on disk to an existing target database. Essentially, the 
+** application:
+**
+**     1) Opens an RBU handle using the sqlite3rbu_open() function.
+**
+**     2) Registers any required virtual table modules with the database
+**        handle returned by sqlite3rbu_db(). Also, if required, register
+**        the rbu_delta() implementation.
+**
+**     3) Calls the sqlite3rbu_step() function one or more times on
+**        the new handle. Each call to sqlite3rbu_step() performs a single
+**        b-tree operation, so thousands of calls may be required to apply 
+**        a complete update.
+**
+**     4) Calls sqlite3rbu_close() to close the RBU update handle. If
+**        sqlite3rbu_step() has been called enough times to completely
+**        apply the update to the target database, then the RBU database
+**        is marked as fully applied. Otherwise, the state of the RBU 
+**        update application is saved in the RBU database for later 
+**        resumption.
+**
+** See comments below for more detail on APIs.
+**
+** If an update is only partially applied to the target database by the
+** time sqlite3rbu_close() is called, various state information is saved 
+** within the RBU database. This allows subsequent processes to automatically
+** resume the RBU update from where it left off.
+**
+** To remove all RBU extension state information, returning an RBU database 
+** to its original contents, it is sufficient to drop all tables that begin
+** with the prefix "rbu_"
+**
+** DATABASE LOCKING
+**
+** An RBU update may not be applied to a database in WAL mode. Attempting
+** to do so is an error (SQLITE_ERROR).
+**
+** While an RBU handle is open, a SHARED lock may be held on the target
+** database file. This means it is possible for other clients to read the
+** database, but not to write it.
+**
+** If an RBU update is started and then suspended before it is completed,
+** then an external client writes to the database, then attempting to resume
+** the suspended RBU update is also an error (SQLITE_BUSY).
+*/
 
-    sqlite3_free(aCell);
-    rc = nodeAcquire(pRtree, iBest, pNode, &pChild);
-    nodeRelease(pRtree, pNode);
-    pNode = pChild;
-  }
+#ifndef _SQLITE3RBU_H
+#define _SQLITE3RBU_H
 
-  *ppLeaf = pNode;
-  return rc;
-}
+/* #include "sqlite3.h"              ** Required for error code definitions ** */
+
+typedef struct sqlite3rbu sqlite3rbu;
 
 /*
-** A cell with the same content as pCell has just been inserted into
-** the node pNode. This function updates the bounding box cells in
-** all ancestor elements.
+** Open an RBU handle.
+**
+** Argument zTarget is the path to the target database. Argument zRbu is
+** the path to the RBU database. Each call to this function must be matched
+** by a call to sqlite3rbu_close(). When opening the databases, RBU passes
+** the SQLITE_CONFIG_URI flag to sqlite3_open_v2(). So if either zTarget
+** or zRbu begin with "file:", it will be interpreted as an SQLite 
+** database URI, not a regular file name.
+**
+** If the zState argument is passed a NULL value, the RBU extension stores 
+** the current state of the update (how many rows have been updated, which 
+** indexes are yet to be updated etc.) within the RBU database itself. This
+** can be convenient, as it means that the RBU application does not need to
+** organize removing a separate state file after the update is concluded. 
+** Or, if zState is non-NULL, it must be a path to a database file in which 
+** the RBU extension can store the state of the update.
+**
+** When resuming an RBU update, the zState argument must be passed the same
+** value as when the RBU update was started.
+**
+** Once the RBU update is finished, the RBU extension does not 
+** automatically remove any zState database file, even if it created it.
+**
+** By default, RBU uses the default VFS to access the files on disk. To
+** use a VFS other than the default, an SQLite "file:" URI containing a
+** "vfs=..." option may be passed as the zTarget option.
+**
+** IMPORTANT NOTE FOR ZIPVFS USERS: The RBU extension works with all of
+** SQLite's built-in VFSs, including the multiplexor VFS. However it does
+** not work out of the box with zipvfs. Refer to the comment describing
+** the zipvfs_create_vfs() API below for details on using RBU with zipvfs.
 */
-static int AdjustTree(
-  Rtree *pRtree,                    /* Rtree table */
-  RtreeNode *pNode,                 /* Adjust ancestry of this node. */
-  RtreeCell *pCell                  /* This cell was just inserted */
-){
-  RtreeNode *p = pNode;
-  while( p->pParent ){
-    RtreeNode *pParent = p->pParent;
-    RtreeCell cell;
-    int iCell;
-
-    if( nodeParentIndex(pRtree, p, &iCell) ){
-      return SQLITE_CORRUPT_VTAB;
-    }
-
-    nodeGetCell(pRtree, pParent, iCell, &cell);
-    if( !cellContains(pRtree, &cell, pCell) ){
-      cellUnion(pRtree, &cell, pCell);
-      nodeOverwriteCell(pRtree, pParent, &cell, iCell);
-    }
- 
-    p = pParent;
-  }
-  return SQLITE_OK;
-}
+SQLITE_API sqlite3rbu *SQLITE_STDCALL sqlite3rbu_open(
+  const char *zTarget, 
+  const char *zRbu,
+  const char *zState
+);
 
 /*
-** Write mapping (iRowid->iNode) to the <rtree>_rowid table.
+** Internally, each RBU connection uses a separate SQLite database 
+** connection to access the target and rbu update databases. This
+** API allows the application direct access to these database handles.
+**
+** The first argument passed to this function must be a valid, open, RBU
+** handle. The second argument should be passed zero to access the target
+** database handle, or non-zero to access the rbu update database handle.
+** Accessing the underlying database handles may be useful in the
+** following scenarios:
+**
+**   * If any target tables are virtual tables, it may be necessary to
+**     call sqlite3_create_module() on the target database handle to 
+**     register the required virtual table implementations.
+**
+**   * If the data_xxx tables in the RBU source database are virtual 
+**     tables, the application may need to call sqlite3_create_module() on
+**     the rbu update db handle to any required virtual table
+**     implementations.
+**
+**   * If the application uses the "rbu_delta()" feature described above,
+**     it must use sqlite3_create_function() or similar to register the
+**     rbu_delta() implementation with the target database handle.
+**
+** If an error has occurred, either while opening or stepping the RBU object,
+** this function may return NULL. The error code and message may be collected
+** when sqlite3rbu_close() is called.
 */
-static int rowidWrite(Rtree *pRtree, sqlite3_int64 iRowid, sqlite3_int64 iNode){
-  sqlite3_bind_int64(pRtree->pWriteRowid, 1, iRowid);
-  sqlite3_bind_int64(pRtree->pWriteRowid, 2, iNode);
-  sqlite3_step(pRtree->pWriteRowid);
-  return sqlite3_reset(pRtree->pWriteRowid);
-}
+SQLITE_API sqlite3 *SQLITE_STDCALL sqlite3rbu_db(sqlite3rbu*, int bRbu);
 
 /*
-** Write mapping (iNode->iPar) to the <rtree>_parent table.
+** Do some work towards applying the RBU update to the target db. 
+**
+** Return SQLITE_DONE if the update has been completely applied, or 
+** SQLITE_OK if no error occurs but there remains work to do to apply
+** the RBU update. If an error does occur, some other error code is 
+** returned. 
+**
+** Once a call to sqlite3rbu_step() has returned a value other than
+** SQLITE_OK, all subsequent calls on the same RBU handle are no-ops
+** that immediately return the same value.
 */
-static int parentWrite(Rtree *pRtree, sqlite3_int64 iNode, sqlite3_int64 iPar){
-  sqlite3_bind_int64(pRtree->pWriteParent, 1, iNode);
-  sqlite3_bind_int64(pRtree->pWriteParent, 2, iPar);
-  sqlite3_step(pRtree->pWriteParent);
-  return sqlite3_reset(pRtree->pWriteParent);
-}
+SQLITE_API int SQLITE_STDCALL sqlite3rbu_step(sqlite3rbu *pRbu);
 
-static int rtreeInsertCell(Rtree *, RtreeNode *, RtreeCell *, int);
+/*
+** Close an RBU handle. 
+**
+** If the RBU update has been completely applied, mark the RBU database
+** as fully applied. Otherwise, assuming no error has occurred, save the
+** current state of the RBU update appliation to the RBU database.
+**
+** If an error has already occurred as part of an sqlite3rbu_step()
+** or sqlite3rbu_open() call, or if one occurs within this function, an
+** SQLite error code is returned. Additionally, *pzErrmsg may be set to
+** point to a buffer containing a utf-8 formatted English language error
+** message. It is the responsibility of the caller to eventually free any 
+** such buffer using sqlite3_free().
+**
+** Otherwise, if no error occurs, this function returns SQLITE_OK if the
+** update has been partially applied, or SQLITE_DONE if it has been 
+** completely applied.
+*/
+SQLITE_API int SQLITE_STDCALL sqlite3rbu_close(sqlite3rbu *pRbu, char **pzErrmsg);
 
+/*
+** Return the total number of key-value operations (inserts, deletes or 
+** updates) that have been performed on the target database since the
+** current RBU update was started.
+*/
+SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3rbu_progress(sqlite3rbu *pRbu);
 
 /*
-** Arguments aIdx, aDistance and aSpare all point to arrays of size
-** nIdx. The aIdx array contains the set of integers from 0 to 
-** (nIdx-1) in no particular order. This function sorts the values
-** in aIdx according to the indexed values in aDistance. For
-** example, assuming the inputs:
+** Create an RBU VFS named zName that accesses the underlying file-system
+** via existing VFS zParent. Or, if the zParent parameter is passed NULL, 
+** then the new RBU VFS uses the default system VFS to access the file-system.
+** The new object is registered as a non-default VFS with SQLite before 
+** returning.
 **
-**   aIdx      = { 0,   1,   2,   3 }
-**   aDistance = { 5.0, 2.0, 7.0, 6.0 }
+** Part of the RBU implementation uses a custom VFS object. Usually, this
+** object is created and deleted automatically by RBU. 
 **
-** this function sets the aIdx array to contain:
+** The exception is for applications that also use zipvfs. In this case,
+** the custom VFS must be explicitly created by the user before the RBU
+** handle is opened. The RBU VFS should be installed so that the zipvfs
+** VFS uses the RBU VFS, which in turn uses any other VFS layers in use 
+** (for example multiplexor) to access the file-system. For example,
+** to assemble an RBU enabled VFS stack that uses both zipvfs and 
+** multiplexor (error checking omitted):
 **
-**   aIdx      = { 0,   1,   2,   3 }
+**     // Create a VFS named "multiplex" (not the default).
+**     sqlite3_multiplex_initialize(0, 0);
 **
-** The aSpare array is used as temporary working space by the
-** sorting algorithm.
+**     // Create an rbu VFS named "rbu" that uses multiplexor. If the
+**     // second argument were replaced with NULL, the "rbu" VFS would
+**     // access the file-system via the system default VFS, bypassing the
+**     // multiplexor.
+**     sqlite3rbu_create_vfs("rbu", "multiplex");
+**
+**     // Create a zipvfs VFS named "zipvfs" that uses rbu.
+**     zipvfs_create_vfs_v3("zipvfs", "rbu", 0, xCompressorAlgorithmDetector);
+**
+**     // Make zipvfs the default VFS.
+**     sqlite3_vfs_register(sqlite3_vfs_find("zipvfs"), 1);
+**
+** Because the default VFS created above includes a RBU functionality, it
+** may be used by RBU clients. Attempting to use RBU with a zipvfs VFS stack
+** that does not include the RBU layer results in an error.
+**
+** The overhead of adding the "rbu" VFS to the system is negligible for 
+** non-RBU users. There is no harm in an application accessing the 
+** file-system via "rbu" all the time, even if it only uses RBU functionality 
+** occasionally.
 */
-static void SortByDistance(
-  int *aIdx, 
-  int nIdx, 
-  RtreeDValue *aDistance, 
-  int *aSpare
-){
-  if( nIdx>1 ){
-    int iLeft = 0;
-    int iRight = 0;
+SQLITE_API int SQLITE_STDCALL sqlite3rbu_create_vfs(const char *zName, const char *zParent);
 
-    int nLeft = nIdx/2;
-    int nRight = nIdx-nLeft;
-    int *aLeft = aIdx;
-    int *aRight = &aIdx[nLeft];
+/*
+** Deregister and destroy an RBU vfs created by an earlier call to
+** sqlite3rbu_create_vfs().
+**
+** VFS objects are not reference counted. If a VFS object is destroyed
+** before all database handles that use it have been closed, the results
+** are undefined.
+*/
+SQLITE_API void SQLITE_STDCALL sqlite3rbu_destroy_vfs(const char *zName);
 
-    SortByDistance(aLeft, nLeft, aDistance, aSpare);
-    SortByDistance(aRight, nRight, aDistance, aSpare);
+#endif /* _SQLITE3RBU_H */
 
-    memcpy(aSpare, aLeft, sizeof(int)*nLeft);
-    aLeft = aSpare;
+/************** End of sqlite3rbu.h ******************************************/
+/************** Continuing where we left off in sqlite3rbu.c *****************/
 
-    while( iLeft<nLeft || iRight<nRight ){
-      if( iLeft==nLeft ){
-        aIdx[iLeft+iRight] = aRight[iRight];
-        iRight++;
-      }else if( iRight==nRight ){
-        aIdx[iLeft+iRight] = aLeft[iLeft];
-        iLeft++;
-      }else{
-        RtreeDValue fLeft = aDistance[aLeft[iLeft]];
-        RtreeDValue fRight = aDistance[aRight[iRight]];
-        if( fLeft<fRight ){
-          aIdx[iLeft+iRight] = aLeft[iLeft];
-          iLeft++;
-        }else{
-          aIdx[iLeft+iRight] = aRight[iRight];
-          iRight++;
-        }
-      }
-    }
+/* Maximum number of prepared UPDATE statements held by this module */
+#define SQLITE_RBU_UPDATE_CACHESIZE 16
 
-#if 0
-    /* Check that the sort worked */
-    {
-      int jj;
-      for(jj=1; jj<nIdx; jj++){
-        RtreeDValue left = aDistance[aIdx[jj-1]];
-        RtreeDValue right = aDistance[aIdx[jj]];
-        assert( left<=right );
-      }
-    }
+/*
+** Swap two objects of type TYPE.
+*/
+#if !defined(SQLITE_AMALGAMATION)
+# define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
+#endif
+
+/*
+** The rbu_state table is used to save the state of a partially applied
+** update so that it can be resumed later. The table consists of integer
+** keys mapped to values as follows:
+**
+** RBU_STATE_STAGE:
+**   May be set to integer values 1, 2, 4 or 5. As follows:
+**       1: the *-rbu file is currently under construction.
+**       2: the *-rbu file has been constructed, but not yet moved 
+**          to the *-wal path.
+**       4: the checkpoint is underway.
+**       5: the rbu update has been checkpointed.
+**
+** RBU_STATE_TBL:
+**   Only valid if STAGE==1. The target database name of the table 
+**   currently being written.
+**
+** RBU_STATE_IDX:
+**   Only valid if STAGE==1. The target database name of the index 
+**   currently being written, or NULL if the main table is currently being
+**   updated.
+**
+** RBU_STATE_ROW:
+**   Only valid if STAGE==1. Number of rows already processed for the current
+**   table/index.
+**
+** RBU_STATE_PROGRESS:
+**   Trbul number of sqlite3rbu_step() calls made so far as part of this
+**   rbu update.
+**
+** RBU_STATE_CKPT:
+**   Valid if STAGE==4. The 64-bit checksum associated with the wal-index
+**   header created by recovering the *-wal file. This is used to detect
+**   cases when another client appends frames to the *-wal file in the
+**   middle of an incremental checkpoint (an incremental checkpoint cannot
+**   be continued if this happens).
+**
+** RBU_STATE_COOKIE:
+**   Valid if STAGE==1. The current change-counter cookie value in the 
+**   target db file.
+**
+** RBU_STATE_OALSZ:
+**   Valid if STAGE==1. The size in bytes of the *-oal file.
+*/
+#define RBU_STATE_STAGE       1
+#define RBU_STATE_TBL         2
+#define RBU_STATE_IDX         3
+#define RBU_STATE_ROW         4
+#define RBU_STATE_PROGRESS    5
+#define RBU_STATE_CKPT        6
+#define RBU_STATE_COOKIE      7
+#define RBU_STATE_OALSZ       8
+
+#define RBU_STAGE_OAL         1
+#define RBU_STAGE_MOVE        2
+#define RBU_STAGE_CAPTURE     3
+#define RBU_STAGE_CKPT        4
+#define RBU_STAGE_DONE        5
+
+
+#define RBU_CREATE_STATE \
+  "CREATE TABLE IF NOT EXISTS %s.rbu_state(k INTEGER PRIMARY KEY, v)"
+
+typedef struct RbuFrame RbuFrame;
+typedef struct RbuObjIter RbuObjIter;
+typedef struct RbuState RbuState;
+typedef struct rbu_vfs rbu_vfs;
+typedef struct rbu_file rbu_file;
+typedef struct RbuUpdateStmt RbuUpdateStmt;
+
+#if !defined(SQLITE_AMALGAMATION)
+typedef unsigned int u32;
+typedef unsigned char u8;
+typedef sqlite3_int64 i64;
 #endif
-  }
-}
 
 /*
-** Arguments aIdx, aCell and aSpare all point to arrays of size
-** nIdx. The aIdx array contains the set of integers from 0 to 
-** (nIdx-1) in no particular order. This function sorts the values
-** in aIdx according to dimension iDim of the cells in aCell. The
-** minimum value of dimension iDim is considered first, the
-** maximum used to break ties.
-**
-** The aSpare array is used as temporary working space by the
-** sorting algorithm.
+** These values must match the values defined in wal.c for the equivalent
+** locks. These are not magic numbers as they are part of the SQLite file
+** format.
 */
-static void SortByDimension(
-  Rtree *pRtree,
-  int *aIdx, 
-  int nIdx, 
-  int iDim, 
-  RtreeCell *aCell, 
-  int *aSpare
-){
-  if( nIdx>1 ){
+#define WAL_LOCK_WRITE  0
+#define WAL_LOCK_CKPT   1
+#define WAL_LOCK_READ0  3
 
-    int iLeft = 0;
-    int iRight = 0;
+/*
+** A structure to store values read from the rbu_state table in memory.
+*/
+struct RbuState {
+  int eStage;
+  char *zTbl;
+  char *zIdx;
+  i64 iWalCksum;
+  int nRow;
+  i64 nProgress;
+  u32 iCookie;
+  i64 iOalSz;
+};
 
-    int nLeft = nIdx/2;
-    int nRight = nIdx-nLeft;
-    int *aLeft = aIdx;
-    int *aRight = &aIdx[nLeft];
+struct RbuUpdateStmt {
+  char *zMask;                    /* Copy of update mask used with pUpdate */
+  sqlite3_stmt *pUpdate;          /* Last update statement (or NULL) */
+  RbuUpdateStmt *pNext;
+};
 
-    SortByDimension(pRtree, aLeft, nLeft, iDim, aCell, aSpare);
-    SortByDimension(pRtree, aRight, nRight, iDim, aCell, aSpare);
+/*
+** An iterator of this type is used to iterate through all objects in
+** the target database that require updating. For each such table, the
+** iterator visits, in order:
+**
+**     * the table itself, 
+**     * each index of the table (zero or more points to visit), and
+**     * a special "cleanup table" state.
+**
+** abIndexed:
+**   If the table has no indexes on it, abIndexed is set to NULL. Otherwise,
+**   it points to an array of flags nTblCol elements in size. The flag is
+**   set for each column that is either a part of the PK or a part of an
+**   index. Or clear otherwise.
+**   
+*/
+struct RbuObjIter {
+  sqlite3_stmt *pTblIter;         /* Iterate through tables */
+  sqlite3_stmt *pIdxIter;         /* Index iterator */
+  int nTblCol;                    /* Size of azTblCol[] array */
+  char **azTblCol;                /* Array of unquoted target column names */
+  char **azTblType;               /* Array of target column types */
+  int *aiSrcOrder;                /* src table col -> target table col */
+  u8 *abTblPk;                    /* Array of flags, set on target PK columns */
+  u8 *abNotNull;                  /* Array of flags, set on NOT NULL columns */
+  u8 *abIndexed;                  /* Array of flags, set on indexed & PK cols */
+  int eType;                      /* Table type - an RBU_PK_XXX value */
+
+  /* Output variables. zTbl==0 implies EOF. */
+  int bCleanup;                   /* True in "cleanup" state */
+  const char *zTbl;               /* Name of target db table */
+  const char *zIdx;               /* Name of target db index (or null) */
+  int iTnum;                      /* Root page of current object */
+  int iPkTnum;                    /* If eType==EXTERNAL, root of PK index */
+  int bUnique;                    /* Current index is unique */
+
+  /* Statements created by rbuObjIterPrepareAll() */
+  int nCol;                       /* Number of columns in current object */
+  sqlite3_stmt *pSelect;          /* Source data */
+  sqlite3_stmt *pInsert;          /* Statement for INSERT operations */
+  sqlite3_stmt *pDelete;          /* Statement for DELETE ops */
+  sqlite3_stmt *pTmpInsert;       /* Insert into rbu_tmp_$zTbl */
+
+  /* Last UPDATE used (for PK b-tree updates only), or NULL. */
+  RbuUpdateStmt *pRbuUpdate;
+};
 
-    memcpy(aSpare, aLeft, sizeof(int)*nLeft);
-    aLeft = aSpare;
-    while( iLeft<nLeft || iRight<nRight ){
-      RtreeDValue xleft1 = DCOORD(aCell[aLeft[iLeft]].aCoord[iDim*2]);
-      RtreeDValue xleft2 = DCOORD(aCell[aLeft[iLeft]].aCoord[iDim*2+1]);
-      RtreeDValue xright1 = DCOORD(aCell[aRight[iRight]].aCoord[iDim*2]);
-      RtreeDValue xright2 = DCOORD(aCell[aRight[iRight]].aCoord[iDim*2+1]);
-      if( (iLeft!=nLeft) && ((iRight==nRight)
-       || (xleft1<xright1)
-       || (xleft1==xright1 && xleft2<xright2)
-      )){
-        aIdx[iLeft+iRight] = aLeft[iLeft];
-        iLeft++;
-      }else{
-        aIdx[iLeft+iRight] = aRight[iRight];
-        iRight++;
-      }
-    }
+/*
+** Values for RbuObjIter.eType
+**
+**     0: Table does not exist (error)
+**     1: Table has an implicit rowid.
+**     2: Table has an explicit IPK column.
+**     3: Table has an external PK index.
+**     4: Table is WITHOUT ROWID.
+**     5: Table is a virtual table.
+*/
+#define RBU_PK_NOTABLE        0
+#define RBU_PK_NONE           1
+#define RBU_PK_IPK            2
+#define RBU_PK_EXTERNAL       3
+#define RBU_PK_WITHOUT_ROWID  4
+#define RBU_PK_VTAB           5
 
-#if 0
-    /* Check that the sort worked */
-    {
-      int jj;
-      for(jj=1; jj<nIdx; jj++){
-        RtreeDValue xleft1 = aCell[aIdx[jj-1]].aCoord[iDim*2];
-        RtreeDValue xleft2 = aCell[aIdx[jj-1]].aCoord[iDim*2+1];
-        RtreeDValue xright1 = aCell[aIdx[jj]].aCoord[iDim*2];
-        RtreeDValue xright2 = aCell[aIdx[jj]].aCoord[iDim*2+1];
-        assert( xleft1<=xright1 && (xleft1<xright1 || xleft2<=xright2) );
-      }
-    }
-#endif
-  }
-}
 
 /*
-** Implementation of the R*-tree variant of SplitNode from Beckman[1990].
+** Within the RBU_STAGE_OAL stage, each call to sqlite3rbu_step() performs
+** one of the following operations.
 */
-static int splitNodeStartree(
-  Rtree *pRtree,
-  RtreeCell *aCell,
-  int nCell,
-  RtreeNode *pLeft,
-  RtreeNode *pRight,
-  RtreeCell *pBboxLeft,
-  RtreeCell *pBboxRight
-){
-  int **aaSorted;
-  int *aSpare;
-  int ii;
+#define RBU_INSERT     1          /* Insert on a main table b-tree */
+#define RBU_DELETE     2          /* Delete a row from a main table b-tree */
+#define RBU_IDX_DELETE 3          /* Delete a row from an aux. index b-tree */
+#define RBU_IDX_INSERT 4          /* Insert on an aux. index b-tree */
+#define RBU_UPDATE     5          /* Update a row in a main table b-tree */
 
-  int iBestDim = 0;
-  int iBestSplit = 0;
-  RtreeDValue fBestMargin = RTREE_ZERO;
 
-  int nByte = (pRtree->nDim+1)*(sizeof(int*)+nCell*sizeof(int));
+/*
+** A single step of an incremental checkpoint - frame iWalFrame of the wal
+** file should be copied to page iDbPage of the database file.
+*/
+struct RbuFrame {
+  u32 iDbPage;
+  u32 iWalFrame;
+};
 
-  aaSorted = (int **)sqlite3_malloc(nByte);
-  if( !aaSorted ){
-    return SQLITE_NOMEM;
-  }
+/*
+** RBU handle.
+*/
+struct sqlite3rbu {
+  int eStage;                     /* Value of RBU_STATE_STAGE field */
+  sqlite3 *dbMain;                /* target database handle */
+  sqlite3 *dbRbu;                 /* rbu database handle */
+  char *zTarget;                  /* Path to target db */
+  char *zRbu;                     /* Path to rbu db */
+  char *zState;                   /* Path to state db (or NULL if zRbu) */
+  char zStateDb[5];               /* Db name for state ("stat" or "main") */
+  int rc;                         /* Value returned by last rbu_step() call */
+  char *zErrmsg;                  /* Error message if rc!=SQLITE_OK */
+  int nStep;                      /* Rows processed for current object */
+  int nProgress;                  /* Rows processed for all objects */
+  RbuObjIter objiter;             /* Iterator for skipping through tbl/idx */
+  const char *zVfsName;           /* Name of automatically created rbu vfs */
+  rbu_file *pTargetFd;            /* File handle open on target db */
+  i64 iOalSz;
+
+  /* The following state variables are used as part of the incremental
+  ** checkpoint stage (eStage==RBU_STAGE_CKPT). See comments surrounding
+  ** function rbuSetupCheckpoint() for details.  */
+  u32 iMaxFrame;                  /* Largest iWalFrame value in aFrame[] */
+  u32 mLock;
+  int nFrame;                     /* Entries in aFrame[] array */
+  int nFrameAlloc;                /* Allocated size of aFrame[] array */
+  RbuFrame *aFrame;
+  int pgsz;
+  u8 *aBuf;
+  i64 iWalCksum;
+};
 
-  aSpare = &((int *)&aaSorted[pRtree->nDim])[pRtree->nDim*nCell];
-  memset(aaSorted, 0, nByte);
-  for(ii=0; ii<pRtree->nDim; ii++){
-    int jj;
-    aaSorted[ii] = &((int *)&aaSorted[pRtree->nDim])[ii*nCell];
-    for(jj=0; jj<nCell; jj++){
-      aaSorted[ii][jj] = jj;
-    }
-    SortByDimension(pRtree, aaSorted[ii], nCell, ii, aCell, aSpare);
-  }
+/*
+** An rbu VFS is implemented using an instance of this structure.
+*/
+struct rbu_vfs {
+  sqlite3_vfs base;               /* rbu VFS shim methods */
+  sqlite3_vfs *pRealVfs;          /* Underlying VFS */
+  sqlite3_mutex *mutex;           /* Mutex to protect pMain */
+  rbu_file *pMain;                /* Linked list of main db files */
+};
 
-  for(ii=0; ii<pRtree->nDim; ii++){
-    RtreeDValue margin = RTREE_ZERO;
-    RtreeDValue fBestOverlap = RTREE_ZERO;
-    RtreeDValue fBestArea = RTREE_ZERO;
-    int iBestLeft = 0;
-    int nLeft;
+/*
+** Each file opened by an rbu VFS is represented by an instance of
+** the following structure.
+*/
+struct rbu_file {
+  sqlite3_file base;              /* sqlite3_file methods */
+  sqlite3_file *pReal;            /* Underlying file handle */
+  rbu_vfs *pRbuVfs;               /* Pointer to the rbu_vfs object */
+  sqlite3rbu *pRbu;               /* Pointer to rbu object (rbu target only) */
 
-    for(
-      nLeft=RTREE_MINCELLS(pRtree); 
-      nLeft<=(nCell-RTREE_MINCELLS(pRtree)); 
-      nLeft++
-    ){
-      RtreeCell left;
-      RtreeCell right;
-      int kk;
-      RtreeDValue overlap;
-      RtreeDValue area;
+  int openFlags;                  /* Flags this file was opened with */
+  u32 iCookie;                    /* Cookie value for main db files */
+  u8 iWriteVer;                   /* "write-version" value for main db files */
 
-      memcpy(&left, &aCell[aaSorted[ii][0]], sizeof(RtreeCell));
-      memcpy(&right, &aCell[aaSorted[ii][nCell-1]], sizeof(RtreeCell));
-      for(kk=1; kk<(nCell-1); kk++){
-        if( kk<nLeft ){
-          cellUnion(pRtree, &left, &aCell[aaSorted[ii][kk]]);
-        }else{
-          cellUnion(pRtree, &right, &aCell[aaSorted[ii][kk]]);
-        }
-      }
-      margin += cellMargin(pRtree, &left);
-      margin += cellMargin(pRtree, &right);
-      overlap = cellOverlap(pRtree, &left, &right, 1);
-      area = cellArea(pRtree, &left) + cellArea(pRtree, &right);
-      if( (nLeft==RTREE_MINCELLS(pRtree))
-       || (overlap<fBestOverlap)
-       || (overlap==fBestOverlap && area<fBestArea)
-      ){
-        iBestLeft = nLeft;
-        fBestOverlap = overlap;
-        fBestArea = area;
-      }
-    }
+  int nShm;                       /* Number of entries in apShm[] array */
+  char **apShm;                   /* Array of mmap'd *-shm regions */
+  char *zDel;                     /* Delete this when closing file */
 
-    if( ii==0 || margin<fBestMargin ){
-      iBestDim = ii;
-      fBestMargin = margin;
-      iBestSplit = iBestLeft;
-    }
-  }
+  const char *zWal;               /* Wal filename for this main db file */
+  rbu_file *pWalFd;               /* Wal file descriptor for this main db */
+  rbu_file *pMainNext;            /* Next MAIN_DB file */
+};
 
-  memcpy(pBboxLeft, &aCell[aaSorted[iBestDim][0]], sizeof(RtreeCell));
-  memcpy(pBboxRight, &aCell[aaSorted[iBestDim][iBestSplit]], sizeof(RtreeCell));
-  for(ii=0; ii<nCell; ii++){
-    RtreeNode *pTarget = (ii<iBestSplit)?pLeft:pRight;
-    RtreeCell *pBbox = (ii<iBestSplit)?pBboxLeft:pBboxRight;
-    RtreeCell *pCell = &aCell[aaSorted[iBestDim][ii]];
-    nodeInsertCell(pRtree, pTarget, pCell);
-    cellUnion(pRtree, pBbox, pCell);
-  }
 
-  sqlite3_free(aaSorted);
-  return SQLITE_OK;
+/*
+** Prepare the SQL statement in buffer zSql against database handle db.
+** If successful, set *ppStmt to point to the new statement and return
+** SQLITE_OK. 
+**
+** Otherwise, if an error does occur, set *ppStmt to NULL and return
+** an SQLite error code. Additionally, set output variable *pzErrmsg to
+** point to a buffer containing an error message. It is the responsibility
+** of the caller to (eventually) free this buffer using sqlite3_free().
+*/
+static int prepareAndCollectError(
+  sqlite3 *db, 
+  sqlite3_stmt **ppStmt,
+  char **pzErrmsg,
+  const char *zSql
+){
+  int rc = sqlite3_prepare_v2(db, zSql, -1, ppStmt, 0);
+  if( rc!=SQLITE_OK ){
+    *pzErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    *ppStmt = 0;
+  }
+  return rc;
 }
 
+/*
+** Reset the SQL statement passed as the first argument. Return a copy
+** of the value returned by sqlite3_reset().
+**
+** If an error has occurred, then set *pzErrmsg to point to a buffer
+** containing an error message. It is the responsibility of the caller
+** to eventually free this buffer using sqlite3_free().
+*/
+static int resetAndCollectError(sqlite3_stmt *pStmt, char **pzErrmsg){
+  int rc = sqlite3_reset(pStmt);
+  if( rc!=SQLITE_OK ){
+    *pzErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(sqlite3_db_handle(pStmt)));
+  }
+  return rc;
+}
 
-static int updateMapping(
-  Rtree *pRtree, 
-  i64 iRowid, 
-  RtreeNode *pNode, 
-  int iHeight
+/*
+** Unless it is NULL, argument zSql points to a buffer allocated using
+** sqlite3_malloc containing an SQL statement. This function prepares the SQL
+** statement against database db and frees the buffer. If statement 
+** compilation is successful, *ppStmt is set to point to the new statement 
+** handle and SQLITE_OK is returned. 
+**
+** Otherwise, if an error occurs, *ppStmt is set to NULL and an error code
+** returned. In this case, *pzErrmsg may also be set to point to an error
+** message. It is the responsibility of the caller to free this error message
+** buffer using sqlite3_free().
+**
+** If argument zSql is NULL, this function assumes that an OOM has occurred.
+** In this case SQLITE_NOMEM is returned and *ppStmt set to NULL.
+*/
+static int prepareFreeAndCollectError(
+  sqlite3 *db, 
+  sqlite3_stmt **ppStmt,
+  char **pzErrmsg,
+  char *zSql
 ){
-  int (*xSetMapping)(Rtree *, sqlite3_int64, sqlite3_int64);
-  xSetMapping = ((iHeight==0)?rowidWrite:parentWrite);
-  if( iHeight>0 ){
-    RtreeNode *pChild = nodeHashLookup(pRtree, iRowid);
-    if( pChild ){
-      nodeRelease(pRtree, pChild->pParent);
-      nodeReference(pNode);
-      pChild->pParent = pNode;
-    }
+  int rc;
+  assert( *pzErrmsg==0 );
+  if( zSql==0 ){
+    rc = SQLITE_NOMEM;
+    *ppStmt = 0;
+  }else{
+    rc = prepareAndCollectError(db, ppStmt, pzErrmsg, zSql);
+    sqlite3_free(zSql);
   }
-  return xSetMapping(pRtree, iRowid, pNode->iNode);
+  return rc;
 }
 
-static int SplitNode(
-  Rtree *pRtree,
-  RtreeNode *pNode,
-  RtreeCell *pCell,
-  int iHeight
-){
+/*
+** Free the RbuObjIter.azTblCol[] and RbuObjIter.abTblPk[] arrays allocated
+** by an earlier call to rbuObjIterCacheTableInfo().
+*/
+static void rbuObjIterFreeCols(RbuObjIter *pIter){
   int i;
-  int newCellIsRight = 0;
-
-  int rc = SQLITE_OK;
-  int nCell = NCELL(pNode);
-  RtreeCell *aCell;
-  int *aiUsed;
+  for(i=0; i<pIter->nTblCol; i++){
+    sqlite3_free(pIter->azTblCol[i]);
+    sqlite3_free(pIter->azTblType[i]);
+  }
+  sqlite3_free(pIter->azTblCol);
+  pIter->azTblCol = 0;
+  pIter->azTblType = 0;
+  pIter->aiSrcOrder = 0;
+  pIter->abTblPk = 0;
+  pIter->abNotNull = 0;
+  pIter->nTblCol = 0;
+  pIter->eType = 0;               /* Invalid value */
+}
+
+/*
+** Finalize all statements and free all allocations that are specific to
+** the current object (table/index pair).
+*/
+static void rbuObjIterClearStatements(RbuObjIter *pIter){
+  RbuUpdateStmt *pUp;
+
+  sqlite3_finalize(pIter->pSelect);
+  sqlite3_finalize(pIter->pInsert);
+  sqlite3_finalize(pIter->pDelete);
+  sqlite3_finalize(pIter->pTmpInsert);
+  pUp = pIter->pRbuUpdate;
+  while( pUp ){
+    RbuUpdateStmt *pTmp = pUp->pNext;
+    sqlite3_finalize(pUp->pUpdate);
+    sqlite3_free(pUp);
+    pUp = pTmp;
+  }
+  
+  pIter->pSelect = 0;
+  pIter->pInsert = 0;
+  pIter->pDelete = 0;
+  pIter->pRbuUpdate = 0;
+  pIter->pTmpInsert = 0;
+  pIter->nCol = 0;
+}
 
-  RtreeNode *pLeft = 0;
-  RtreeNode *pRight = 0;
+/*
+** Clean up any resources allocated as part of the iterator object passed
+** as the only argument.
+*/
+static void rbuObjIterFinalize(RbuObjIter *pIter){
+  rbuObjIterClearStatements(pIter);
+  sqlite3_finalize(pIter->pTblIter);
+  sqlite3_finalize(pIter->pIdxIter);
+  rbuObjIterFreeCols(pIter);
+  memset(pIter, 0, sizeof(RbuObjIter));
+}
 
-  RtreeCell leftbbox;
-  RtreeCell rightbbox;
+/*
+** Advance the iterator to the next position.
+**
+** If no error occurs, SQLITE_OK is returned and the iterator is left 
+** pointing to the next entry. Otherwise, an error code and message is 
+** left in the RBU handle passed as the first argument. A copy of the 
+** error code is returned.
+*/
+static int rbuObjIterNext(sqlite3rbu *p, RbuObjIter *pIter){
+  int rc = p->rc;
+  if( rc==SQLITE_OK ){
 
-  /* Allocate an array and populate it with a copy of pCell and 
-  ** all cells from node pLeft. Then zero the original node.
-  */
-  aCell = sqlite3_malloc((sizeof(RtreeCell)+sizeof(int))*(nCell+1));
-  if( !aCell ){
-    rc = SQLITE_NOMEM;
-    goto splitnode_out;
-  }
-  aiUsed = (int *)&aCell[nCell+1];
-  memset(aiUsed, 0, sizeof(int)*(nCell+1));
-  for(i=0; i<nCell; i++){
-    nodeGetCell(pRtree, pNode, i, &aCell[i]);
-  }
-  nodeZero(pRtree, pNode);
-  memcpy(&aCell[nCell], pCell, sizeof(RtreeCell));
-  nCell++;
+    /* Free any SQLite statements used while processing the previous object */ 
+    rbuObjIterClearStatements(pIter);
+    if( pIter->zIdx==0 ){
+      rc = sqlite3_exec(p->dbMain,
+          "DROP TRIGGER IF EXISTS temp.rbu_insert_tr;"
+          "DROP TRIGGER IF EXISTS temp.rbu_update1_tr;"
+          "DROP TRIGGER IF EXISTS temp.rbu_update2_tr;"
+          "DROP TRIGGER IF EXISTS temp.rbu_delete_tr;"
+          , 0, 0, &p->zErrmsg
+      );
+    }
 
-  if( pNode->iNode==1 ){
-    pRight = nodeNew(pRtree, pNode);
-    pLeft = nodeNew(pRtree, pNode);
-    pRtree->iDepth++;
-    pNode->isDirty = 1;
-    writeInt16(pNode->zData, pRtree->iDepth);
-  }else{
-    pLeft = pNode;
-    pRight = nodeNew(pRtree, pLeft->pParent);
-    nodeReference(pLeft);
+    if( rc==SQLITE_OK ){
+      if( pIter->bCleanup ){
+        rbuObjIterFreeCols(pIter);
+        pIter->bCleanup = 0;
+        rc = sqlite3_step(pIter->pTblIter);
+        if( rc!=SQLITE_ROW ){
+          rc = resetAndCollectError(pIter->pTblIter, &p->zErrmsg);
+          pIter->zTbl = 0;
+        }else{
+          pIter->zTbl = (const char*)sqlite3_column_text(pIter->pTblIter, 0);
+          rc = pIter->zTbl ? SQLITE_OK : SQLITE_NOMEM;
+        }
+      }else{
+        if( pIter->zIdx==0 ){
+          sqlite3_stmt *pIdx = pIter->pIdxIter;
+          rc = sqlite3_bind_text(pIdx, 1, pIter->zTbl, -1, SQLITE_STATIC);
+        }
+        if( rc==SQLITE_OK ){
+          rc = sqlite3_step(pIter->pIdxIter);
+          if( rc!=SQLITE_ROW ){
+            rc = resetAndCollectError(pIter->pIdxIter, &p->zErrmsg);
+            pIter->bCleanup = 1;
+            pIter->zIdx = 0;
+          }else{
+            pIter->zIdx = (const char*)sqlite3_column_text(pIter->pIdxIter, 0);
+            pIter->iTnum = sqlite3_column_int(pIter->pIdxIter, 1);
+            pIter->bUnique = sqlite3_column_int(pIter->pIdxIter, 2);
+            rc = pIter->zIdx ? SQLITE_OK : SQLITE_NOMEM;
+          }
+        }
+      }
+    }
   }
 
-  if( !pLeft || !pRight ){
-    rc = SQLITE_NOMEM;
-    goto splitnode_out;
+  if( rc!=SQLITE_OK ){
+    rbuObjIterFinalize(pIter);
+    p->rc = rc;
   }
+  return rc;
+}
 
-  memset(pLeft->zData, 0, pRtree->iNodeSize);
-  memset(pRight->zData, 0, pRtree->iNodeSize);
+/*
+** Initialize the iterator structure passed as the second argument.
+**
+** If no error occurs, SQLITE_OK is returned and the iterator is left 
+** pointing to the first entry. Otherwise, an error code and message is 
+** left in the RBU handle passed as the first argument. A copy of the 
+** error code is returned.
+*/
+static int rbuObjIterFirst(sqlite3rbu *p, RbuObjIter *pIter){
+  int rc;
+  memset(pIter, 0, sizeof(RbuObjIter));
 
-  rc = splitNodeStartree(pRtree, aCell, nCell, pLeft, pRight,
-                         &leftbbox, &rightbbox);
-  if( rc!=SQLITE_OK ){
-    goto splitnode_out;
-  }
+  rc = prepareAndCollectError(p->dbRbu, &pIter->pTblIter, &p->zErrmsg, 
+      "SELECT substr(name, 6) FROM sqlite_master "
+      "WHERE type IN ('table', 'view') AND name LIKE 'data_%'"
+  );
 
-  /* Ensure both child nodes have node numbers assigned to them by calling
-  ** nodeWrite(). Node pRight always needs a node number, as it was created
-  ** by nodeNew() above. But node pLeft sometimes already has a node number.
-  ** In this case avoid the all to nodeWrite().
-  */
-  if( SQLITE_OK!=(rc = nodeWrite(pRtree, pRight))
-   || (0==pLeft->iNode && SQLITE_OK!=(rc = nodeWrite(pRtree, pLeft)))
-  ){
-    goto splitnode_out;
+  if( rc==SQLITE_OK ){
+    rc = prepareAndCollectError(p->dbMain, &pIter->pIdxIter, &p->zErrmsg,
+        "SELECT name, rootpage, sql IS NULL OR substr(8, 6)=='UNIQUE' "
+        "  FROM main.sqlite_master "
+        "  WHERE type='index' AND tbl_name = ?"
+    );
   }
 
-  rightbbox.iRowid = pRight->iNode;
-  leftbbox.iRowid = pLeft->iNode;
+  pIter->bCleanup = 1;
+  p->rc = rc;
+  return rbuObjIterNext(p, pIter);
+}
 
-  if( pNode->iNode==1 ){
-    rc = rtreeInsertCell(pRtree, pLeft->pParent, &leftbbox, iHeight+1);
-    if( rc!=SQLITE_OK ){
-      goto splitnode_out;
-    }
+/*
+** This is a wrapper around "sqlite3_mprintf(zFmt, ...)". If an OOM occurs,
+** an error code is stored in the RBU handle passed as the first argument.
+**
+** If an error has already occurred (p->rc is already set to something other
+** than SQLITE_OK), then this function returns NULL without modifying the
+** stored error code. In this case it still calls sqlite3_free() on any 
+** printf() parameters associated with %z conversions.
+*/
+static char *rbuMPrintf(sqlite3rbu *p, const char *zFmt, ...){
+  char *zSql = 0;
+  va_list ap;
+  va_start(ap, zFmt);
+  zSql = sqlite3_vmprintf(zFmt, ap);
+  if( p->rc==SQLITE_OK ){
+    if( zSql==0 ) p->rc = SQLITE_NOMEM;
   }else{
-    RtreeNode *pParent = pLeft->pParent;
-    int iCell;
-    rc = nodeParentIndex(pRtree, pLeft, &iCell);
-    if( rc==SQLITE_OK ){
-      nodeOverwriteCell(pRtree, pParent, &leftbbox, iCell);
-      rc = AdjustTree(pRtree, pParent, &leftbbox);
-    }
-    if( rc!=SQLITE_OK ){
-      goto splitnode_out;
-    }
-  }
-  if( (rc = rtreeInsertCell(pRtree, pRight->pParent, &rightbbox, iHeight+1)) ){
-    goto splitnode_out;
+    sqlite3_free(zSql);
+    zSql = 0;
   }
+  va_end(ap);
+  return zSql;
+}
 
-  for(i=0; i<NCELL(pRight); i++){
-    i64 iRowid = nodeGetRowid(pRtree, pRight, i);
-    rc = updateMapping(pRtree, iRowid, pRight, iHeight);
-    if( iRowid==pCell->iRowid ){
-      newCellIsRight = 1;
-    }
-    if( rc!=SQLITE_OK ){
-      goto splitnode_out;
+/*
+** Argument zFmt is a sqlite3_mprintf() style format string. The trailing
+** arguments are the usual subsitution values. This function performs
+** the printf() style substitutions and executes the result as an SQL
+** statement on the RBU handles database.
+**
+** If an error occurs, an error code and error message is stored in the
+** RBU handle. If an error has already occurred when this function is
+** called, it is a no-op.
+*/
+static int rbuMPrintfExec(sqlite3rbu *p, sqlite3 *db, const char *zFmt, ...){
+  va_list ap;
+  char *zSql;
+  va_start(ap, zFmt);
+  zSql = sqlite3_vmprintf(zFmt, ap);
+  if( p->rc==SQLITE_OK ){
+    if( zSql==0 ){
+      p->rc = SQLITE_NOMEM;
+    }else{
+      p->rc = sqlite3_exec(db, zSql, 0, 0, &p->zErrmsg);
     }
   }
-  if( pNode->iNode==1 ){
-    for(i=0; i<NCELL(pLeft); i++){
-      i64 iRowid = nodeGetRowid(pRtree, pLeft, i);
-      rc = updateMapping(pRtree, iRowid, pLeft, iHeight);
-      if( rc!=SQLITE_OK ){
-        goto splitnode_out;
-      }
+  sqlite3_free(zSql);
+  va_end(ap);
+  return p->rc;
+}
+
+/*
+** Attempt to allocate and return a pointer to a zeroed block of nByte 
+** bytes. 
+**
+** If an error (i.e. an OOM condition) occurs, return NULL and leave an 
+** error code in the rbu handle passed as the first argument. Or, if an 
+** error has already occurred when this function is called, return NULL 
+** immediately without attempting the allocation or modifying the stored
+** error code.
+*/
+static void *rbuMalloc(sqlite3rbu *p, int nByte){
+  void *pRet = 0;
+  if( p->rc==SQLITE_OK ){
+    assert( nByte>0 );
+    pRet = sqlite3_malloc(nByte);
+    if( pRet==0 ){
+      p->rc = SQLITE_NOMEM;
+    }else{
+      memset(pRet, 0, nByte);
     }
-  }else if( newCellIsRight==0 ){
-    rc = updateMapping(pRtree, pCell->iRowid, pLeft, iHeight);
   }
+  return pRet;
+}
 
-  if( rc==SQLITE_OK ){
-    rc = nodeRelease(pRtree, pRight);
-    pRight = 0;
-  }
-  if( rc==SQLITE_OK ){
-    rc = nodeRelease(pRtree, pLeft);
-    pLeft = 0;
-  }
 
-splitnode_out:
-  nodeRelease(pRtree, pRight);
-  nodeRelease(pRtree, pLeft);
-  sqlite3_free(aCell);
-  return rc;
+/*
+** Allocate and zero the pIter->azTblCol[] and abTblPk[] arrays so that
+** there is room for at least nCol elements. If an OOM occurs, store an
+** error code in the RBU handle passed as the first argument.
+*/
+static void rbuAllocateIterArrays(sqlite3rbu *p, RbuObjIter *pIter, int nCol){
+  int nByte = (2*sizeof(char*) + sizeof(int) + 3*sizeof(u8)) * nCol;
+  char **azNew;
+
+  azNew = (char**)rbuMalloc(p, nByte);
+  if( azNew ){
+    pIter->azTblCol = azNew;
+    pIter->azTblType = &azNew[nCol];
+    pIter->aiSrcOrder = (int*)&pIter->azTblType[nCol];
+    pIter->abTblPk = (u8*)&pIter->aiSrcOrder[nCol];
+    pIter->abNotNull = (u8*)&pIter->abTblPk[nCol];
+    pIter->abIndexed = (u8*)&pIter->abNotNull[nCol];
+  }
 }
 
 /*
-** If node pLeaf is not the root of the r-tree and its pParent pointer is 
-** still NULL, load all ancestor nodes of pLeaf into memory and populate
-** the pLeaf->pParent chain all the way up to the root node.
+** The first argument must be a nul-terminated string. This function
+** returns a copy of the string in memory obtained from sqlite3_malloc().
+** It is the responsibility of the caller to eventually free this memory
+** using sqlite3_free().
 **
-** This operation is required when a row is deleted (or updated - an update
-** is implemented as a delete followed by an insert). SQLite provides the
-** rowid of the row to delete, which can be used to find the leaf on which
-** the entry resides (argument pLeaf). Once the leaf is located, this 
-** function is called to determine its ancestry.
+** If an OOM condition is encountered when attempting to allocate memory,
+** output variable (*pRc) is set to SQLITE_NOMEM before returning. Otherwise,
+** if the allocation succeeds, (*pRc) is left unchanged.
 */
-static int fixLeafParent(Rtree *pRtree, RtreeNode *pLeaf){
-  int rc = SQLITE_OK;
-  RtreeNode *pChild = pLeaf;
-  while( rc==SQLITE_OK && pChild->iNode!=1 && pChild->pParent==0 ){
-    int rc2 = SQLITE_OK;          /* sqlite3_reset() return code */
-    sqlite3_bind_int64(pRtree->pReadParent, 1, pChild->iNode);
-    rc = sqlite3_step(pRtree->pReadParent);
-    if( rc==SQLITE_ROW ){
-      RtreeNode *pTest;           /* Used to test for reference loops */
-      i64 iNode;                  /* Node number of parent node */
+static char *rbuStrndup(const char *zStr, int *pRc){
+  char *zRet = 0;
 
-      /* Before setting pChild->pParent, test that we are not creating a
-      ** loop of references (as we would if, say, pChild==pParent). We don't
-      ** want to do this as it leads to a memory leak when trying to delete
-      ** the referenced counted node structures.
-      */
-      iNode = sqlite3_column_int64(pRtree->pReadParent, 0);
-      for(pTest=pLeaf; pTest && pTest->iNode!=iNode; pTest=pTest->pParent);
-      if( !pTest ){
-        rc2 = nodeAcquire(pRtree, iNode, 0, &pChild->pParent);
-      }
+  assert( *pRc==SQLITE_OK );
+  if( zStr ){
+    int nCopy = strlen(zStr) + 1;
+    zRet = (char*)sqlite3_malloc(nCopy);
+    if( zRet ){
+      memcpy(zRet, zStr, nCopy);
+    }else{
+      *pRc = SQLITE_NOMEM;
     }
-    rc = sqlite3_reset(pRtree->pReadParent);
-    if( rc==SQLITE_OK ) rc = rc2;
-    if( rc==SQLITE_OK && !pChild->pParent ) rc = SQLITE_CORRUPT_VTAB;
-    pChild = pChild->pParent;
   }
-  return rc;
-}
-
-static int deleteCell(Rtree *, RtreeNode *, int, int);
-
-static int removeNode(Rtree *pRtree, RtreeNode *pNode, int iHeight){
-  int rc;
-  int rc2;
-  RtreeNode *pParent = 0;
-  int iCell;
 
-  assert( pNode->nRef==1 );
+  return zRet;
+}
 
-  /* Remove the entry in the parent cell. */
-  rc = nodeParentIndex(pRtree, pNode, &iCell);
-  if( rc==SQLITE_OK ){
-    pParent = pNode->pParent;
-    pNode->pParent = 0;
-    rc = deleteCell(pRtree, pParent, iCell, iHeight+1);
-  }
-  rc2 = nodeRelease(pRtree, pParent);
-  if( rc==SQLITE_OK ){
-    rc = rc2;
+/*
+** Finalize the statement passed as the second argument.
+**
+** If the sqlite3_finalize() call indicates that an error occurs, and the
+** rbu handle error code is not already set, set the error code and error
+** message accordingly.
+*/
+static void rbuFinalize(sqlite3rbu *p, sqlite3_stmt *pStmt){
+  sqlite3 *db = sqlite3_db_handle(pStmt);
+  int rc = sqlite3_finalize(pStmt);
+  if( p->rc==SQLITE_OK && rc!=SQLITE_OK ){
+    p->rc = rc;
+    p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+  }
+}
+
+/* Determine the type of a table.
+**
+**   peType is of type (int*), a pointer to an output parameter of type
+**   (int). This call sets the output parameter as follows, depending
+**   on the type of the table specified by parameters dbName and zTbl.
+**
+**     RBU_PK_NOTABLE:       No such table.
+**     RBU_PK_NONE:          Table has an implicit rowid.
+**     RBU_PK_IPK:           Table has an explicit IPK column.
+**     RBU_PK_EXTERNAL:      Table has an external PK index.
+**     RBU_PK_WITHOUT_ROWID: Table is WITHOUT ROWID.
+**     RBU_PK_VTAB:          Table is a virtual table.
+**
+**   Argument *piPk is also of type (int*), and also points to an output
+**   parameter. Unless the table has an external primary key index 
+**   (i.e. unless *peType is set to 3), then *piPk is set to zero. Or,
+**   if the table does have an external primary key index, then *piPk
+**   is set to the root page number of the primary key index before
+**   returning.
+**
+** ALGORITHM:
+**
+**   if( no entry exists in sqlite_master ){
+**     return RBU_PK_NOTABLE
+**   }else if( sql for the entry starts with "CREATE VIRTUAL" ){
+**     return RBU_PK_VTAB
+**   }else if( "PRAGMA index_list()" for the table contains a "pk" index ){
+**     if( the index that is the pk exists in sqlite_master ){
+**       *piPK = rootpage of that index.
+**       return RBU_PK_EXTERNAL
+**     }else{
+**       return RBU_PK_WITHOUT_ROWID
+**     }
+**   }else if( "PRAGMA table_info()" lists one or more "pk" columns ){
+**     return RBU_PK_IPK
+**   }else{
+**     return RBU_PK_NONE
+**   }
+*/
+static void rbuTableType(
+  sqlite3rbu *p,
+  const char *zTab,
+  int *peType,
+  int *piTnum,
+  int *piPk
+){
+  /*
+  ** 0) SELECT count(*) FROM sqlite_master where name=%Q AND IsVirtual(%Q)
+  ** 1) PRAGMA index_list = ?
+  ** 2) SELECT count(*) FROM sqlite_master where name=%Q 
+  ** 3) PRAGMA table_info = ?
+  */
+  sqlite3_stmt *aStmt[4] = {0, 0, 0, 0};
+
+  *peType = RBU_PK_NOTABLE;
+  *piPk = 0;
+
+  assert( p->rc==SQLITE_OK );
+  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[0], &p->zErrmsg, 
+    sqlite3_mprintf(
+          "SELECT (sql LIKE 'create virtual%%'), rootpage"
+          "  FROM sqlite_master"
+          " WHERE name=%Q", zTab
+  ));
+  if( p->rc!=SQLITE_OK || sqlite3_step(aStmt[0])!=SQLITE_ROW ){
+    /* Either an error, or no such table. */
+    goto rbuTableType_end;
   }
-  if( rc!=SQLITE_OK ){
-    return rc;
+  if( sqlite3_column_int(aStmt[0], 0) ){
+    *peType = RBU_PK_VTAB;                     /* virtual table */
+    goto rbuTableType_end;
   }
+  *piTnum = sqlite3_column_int(aStmt[0], 1);
 
-  /* Remove the xxx_node entry. */
-  sqlite3_bind_int64(pRtree->pDeleteNode, 1, pNode->iNode);
-  sqlite3_step(pRtree->pDeleteNode);
-  if( SQLITE_OK!=(rc = sqlite3_reset(pRtree->pDeleteNode)) ){
-    return rc;
+  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[1], &p->zErrmsg, 
+    sqlite3_mprintf("PRAGMA index_list=%Q",zTab)
+  );
+  if( p->rc ) goto rbuTableType_end;
+  while( sqlite3_step(aStmt[1])==SQLITE_ROW ){
+    const u8 *zOrig = sqlite3_column_text(aStmt[1], 3);
+    const u8 *zIdx = sqlite3_column_text(aStmt[1], 1);
+    if( zOrig && zIdx && zOrig[0]=='p' ){
+      p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[2], &p->zErrmsg, 
+          sqlite3_mprintf(
+            "SELECT rootpage FROM sqlite_master WHERE name = %Q", zIdx
+      ));
+      if( p->rc==SQLITE_OK ){
+        if( sqlite3_step(aStmt[2])==SQLITE_ROW ){
+          *piPk = sqlite3_column_int(aStmt[2], 0);
+          *peType = RBU_PK_EXTERNAL;
+        }else{
+          *peType = RBU_PK_WITHOUT_ROWID;
+        }
+      }
+      goto rbuTableType_end;
+    }
   }
 
-  /* Remove the xxx_parent entry. */
-  sqlite3_bind_int64(pRtree->pDeleteParent, 1, pNode->iNode);
-  sqlite3_step(pRtree->pDeleteParent);
-  if( SQLITE_OK!=(rc = sqlite3_reset(pRtree->pDeleteParent)) ){
-    return rc;
+  p->rc = prepareFreeAndCollectError(p->dbMain, &aStmt[3], &p->zErrmsg, 
+    sqlite3_mprintf("PRAGMA table_info=%Q",zTab)
+  );
+  if( p->rc==SQLITE_OK ){
+    while( sqlite3_step(aStmt[3])==SQLITE_ROW ){
+      if( sqlite3_column_int(aStmt[3],5)>0 ){
+        *peType = RBU_PK_IPK;                /* explicit IPK column */
+        goto rbuTableType_end;
+      }
+    }
+    *peType = RBU_PK_NONE;
   }
-  
-  /* Remove the node from the in-memory hash table and link it into
-  ** the Rtree.pDeleted list. Its contents will be re-inserted later on.
-  */
-  nodeHashDelete(pRtree, pNode);
-  pNode->iNode = iHeight;
-  pNode->pNext = pRtree->pDeleted;
-  pNode->nRef++;
-  pRtree->pDeleted = pNode;
 
-  return SQLITE_OK;
+rbuTableType_end: {
+    int i;
+    for(i=0; i<sizeof(aStmt)/sizeof(aStmt[0]); i++){
+      rbuFinalize(p, aStmt[i]);
+    }
+  }
 }
 
-static int fixBoundingBox(Rtree *pRtree, RtreeNode *pNode){
-  RtreeNode *pParent = pNode->pParent;
-  int rc = SQLITE_OK; 
-  if( pParent ){
-    int ii; 
-    int nCell = NCELL(pNode);
-    RtreeCell box;                            /* Bounding box for pNode */
-    nodeGetCell(pRtree, pNode, 0, &box);
-    for(ii=1; ii<nCell; ii++){
-      RtreeCell cell;
-      nodeGetCell(pRtree, pNode, ii, &cell);
-      cellUnion(pRtree, &box, &cell);
-    }
-    box.iRowid = pNode->iNode;
-    rc = nodeParentIndex(pRtree, pNode, &ii);
-    if( rc==SQLITE_OK ){
-      nodeOverwriteCell(pRtree, pParent, &box, ii);
-      rc = fixBoundingBox(pRtree, pParent);
+/*
+** This is a helper function for rbuObjIterCacheTableInfo(). It populates
+** the pIter->abIndexed[] array.
+*/
+static void rbuObjIterCacheIndexedCols(sqlite3rbu *p, RbuObjIter *pIter){
+  sqlite3_stmt *pList = 0;
+  int bIndex = 0;
+
+  if( p->rc==SQLITE_OK ){
+    memcpy(pIter->abIndexed, pIter->abTblPk, sizeof(u8)*pIter->nTblCol);
+    p->rc = prepareFreeAndCollectError(p->dbMain, &pList, &p->zErrmsg,
+        sqlite3_mprintf("PRAGMA main.index_list = %Q", pIter->zTbl)
+    );
+  }
+
+  while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pList) ){
+    const char *zIdx = (const char*)sqlite3_column_text(pList, 1);
+    sqlite3_stmt *pXInfo = 0;
+    if( zIdx==0 ) break;
+    p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
+        sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
+    );
+    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
+      int iCid = sqlite3_column_int(pXInfo, 1);
+      if( iCid>=0 ) pIter->abIndexed[iCid] = 1;
     }
+    rbuFinalize(p, pXInfo);
+    bIndex = 1;
   }
-  return rc;
+
+  rbuFinalize(p, pList);
+  if( bIndex==0 ) pIter->abIndexed = 0;
 }
 
+
 /*
-** Delete the cell at index iCell of node pNode. After removing the
-** cell, adjust the r-tree data structure if required.
+** If they are not already populated, populate the pIter->azTblCol[],
+** pIter->abTblPk[], pIter->nTblCol and pIter->bRowid variables according to
+** the table (not index) that the iterator currently points to.
+**
+** Return SQLITE_OK if successful, or an SQLite error code otherwise. If
+** an error does occur, an error code and error message are also left in 
+** the RBU handle.
 */
-static int deleteCell(Rtree *pRtree, RtreeNode *pNode, int iCell, int iHeight){
-  RtreeNode *pParent;
-  int rc;
+static int rbuObjIterCacheTableInfo(sqlite3rbu *p, RbuObjIter *pIter){
+  if( pIter->azTblCol==0 ){
+    sqlite3_stmt *pStmt = 0;
+    int nCol = 0;
+    int i;                        /* for() loop iterator variable */
+    int bRbuRowid = 0;            /* If input table has column "rbu_rowid" */
+    int iOrder = 0;
+    int iTnum = 0;
+
+    /* Figure out the type of table this step will deal with. */
+    assert( pIter->eType==0 );
+    rbuTableType(p, pIter->zTbl, &pIter->eType, &iTnum, &pIter->iPkTnum);
+    if( p->rc==SQLITE_OK && pIter->eType==RBU_PK_NOTABLE ){
+      p->rc = SQLITE_ERROR;
+      p->zErrmsg = sqlite3_mprintf("no such table: %s", pIter->zTbl);
+    }
+    if( p->rc ) return p->rc;
+    if( pIter->zIdx==0 ) pIter->iTnum = iTnum;
+
+    assert( pIter->eType==RBU_PK_NONE || pIter->eType==RBU_PK_IPK 
+         || pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_WITHOUT_ROWID
+         || pIter->eType==RBU_PK_VTAB
+    );
 
-  if( SQLITE_OK!=(rc = fixLeafParent(pRtree, pNode)) ){
-    return rc;
-  }
+    /* Populate the azTblCol[] and nTblCol variables based on the columns
+    ** of the input table. Ignore any input table columns that begin with
+    ** "rbu_".  */
+    p->rc = prepareFreeAndCollectError(p->dbRbu, &pStmt, &p->zErrmsg, 
+        sqlite3_mprintf("SELECT * FROM 'data_%q'", pIter->zTbl)
+    );
+    if( p->rc==SQLITE_OK ){
+      nCol = sqlite3_column_count(pStmt);
+      rbuAllocateIterArrays(p, pIter, nCol);
+    }
+    for(i=0; p->rc==SQLITE_OK && i<nCol; i++){
+      const char *zName = (const char*)sqlite3_column_name(pStmt, i);
+      if( sqlite3_strnicmp("rbu_", zName, 4) ){
+        char *zCopy = rbuStrndup(zName, &p->rc);
+        pIter->aiSrcOrder[pIter->nTblCol] = pIter->nTblCol;
+        pIter->azTblCol[pIter->nTblCol++] = zCopy;
+      }
+      else if( 0==sqlite3_stricmp("rbu_rowid", zName) ){
+        bRbuRowid = 1;
+      }
+    }
+    sqlite3_finalize(pStmt);
+    pStmt = 0;
 
-  /* Remove the cell from the node. This call just moves bytes around
-  ** the in-memory node image, so it cannot fail.
-  */
-  nodeDeleteCell(pRtree, pNode, iCell);
+    if( p->rc==SQLITE_OK
+     && bRbuRowid!=(pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE)
+    ){
+      p->rc = SQLITE_ERROR;
+      p->zErrmsg = sqlite3_mprintf(
+          "table data_%q %s rbu_rowid column", pIter->zTbl,
+          (bRbuRowid ? "may not have" : "requires")
+      );
+    }
 
-  /* If the node is not the tree root and now has less than the minimum
-  ** number of cells, remove it from the tree. Otherwise, update the
-  ** cell in the parent node so that it tightly contains the updated
-  ** node.
-  */
-  pParent = pNode->pParent;
-  assert( pParent || pNode->iNode==1 );
-  if( pParent ){
-    if( NCELL(pNode)<RTREE_MINCELLS(pRtree) ){
-      rc = removeNode(pRtree, pNode, iHeight);
-    }else{
-      rc = fixBoundingBox(pRtree, pNode);
+    /* Check that all non-HIDDEN columns in the destination table are also
+    ** present in the input table. Populate the abTblPk[], azTblType[] and
+    ** aiTblOrder[] arrays at the same time.  */
+    if( p->rc==SQLITE_OK ){
+      p->rc = prepareFreeAndCollectError(p->dbMain, &pStmt, &p->zErrmsg, 
+          sqlite3_mprintf("PRAGMA table_info(%Q)", pIter->zTbl)
+      );
+    }
+    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      const char *zName = (const char*)sqlite3_column_text(pStmt, 1);
+      if( zName==0 ) break;  /* An OOM - finalize() below returns S_NOMEM */
+      for(i=iOrder; i<pIter->nTblCol; i++){
+        if( 0==strcmp(zName, pIter->azTblCol[i]) ) break;
+      }
+      if( i==pIter->nTblCol ){
+        p->rc = SQLITE_ERROR;
+        p->zErrmsg = sqlite3_mprintf("column missing from data_%q: %s",
+            pIter->zTbl, zName
+        );
+      }else{
+        int iPk = sqlite3_column_int(pStmt, 5);
+        int bNotNull = sqlite3_column_int(pStmt, 3);
+        const char *zType = (const char*)sqlite3_column_text(pStmt, 2);
+
+        if( i!=iOrder ){
+          SWAP(int, pIter->aiSrcOrder[i], pIter->aiSrcOrder[iOrder]);
+          SWAP(char*, pIter->azTblCol[i], pIter->azTblCol[iOrder]);
+        }
+
+        pIter->azTblType[iOrder] = rbuStrndup(zType, &p->rc);
+        pIter->abTblPk[iOrder] = (iPk!=0);
+        pIter->abNotNull[iOrder] = (u8)bNotNull || (iPk!=0);
+        iOrder++;
+      }
     }
+
+    rbuFinalize(p, pStmt);
+    rbuObjIterCacheIndexedCols(p, pIter);
+    assert( pIter->eType!=RBU_PK_VTAB || pIter->abIndexed==0 );
   }
 
-  return rc;
+  return p->rc;
 }
 
-static int Reinsert(
-  Rtree *pRtree, 
-  RtreeNode *pNode, 
-  RtreeCell *pCell, 
-  int iHeight
+/*
+** This function constructs and returns a pointer to a nul-terminated 
+** string containing some SQL clause or list based on one or more of the 
+** column names currently stored in the pIter->azTblCol[] array.
+*/
+static char *rbuObjIterGetCollist(
+  sqlite3rbu *p,                  /* RBU object */
+  RbuObjIter *pIter               /* Object iterator for column names */
 ){
-  int *aOrder;
-  int *aSpare;
-  RtreeCell *aCell;
-  RtreeDValue *aDistance;
-  int nCell;
-  RtreeDValue aCenterCoord[RTREE_MAX_DIMENSIONS];
-  int iDim;
-  int ii;
-  int rc = SQLITE_OK;
-  int n;
-
-  memset(aCenterCoord, 0, sizeof(RtreeDValue)*RTREE_MAX_DIMENSIONS);
+  char *zList = 0;
+  const char *zSep = "";
+  int i;
+  for(i=0; i<pIter->nTblCol; i++){
+    const char *z = pIter->azTblCol[i];
+    zList = rbuMPrintf(p, "%z%s\"%w\"", zList, zSep, z);
+    zSep = ", ";
+  }
+  return zList;
+}
 
-  nCell = NCELL(pNode)+1;
-  n = (nCell+1)&(~1);
+/*
+** This function is used to create a SELECT list (the list of SQL 
+** expressions that follows a SELECT keyword) for a SELECT statement 
+** used to read from an data_xxx or rbu_tmp_xxx table while updating the 
+** index object currently indicated by the iterator object passed as the 
+** second argument. A "PRAGMA index_xinfo = <idxname>" statement is used 
+** to obtain the required information.
+**
+** If the index is of the following form:
+**
+**   CREATE INDEX i1 ON t1(c, b COLLATE nocase);
+**
+** and "t1" is a table with an explicit INTEGER PRIMARY KEY column 
+** "ipk", the returned string is:
+**
+**   "`c` COLLATE 'BINARY', `b` COLLATE 'NOCASE', `ipk` COLLATE 'BINARY'"
+**
+** As well as the returned string, three other malloc'd strings are 
+** returned via output parameters. As follows:
+**
+**   pzImposterCols: ...
+**   pzImposterPk: ...
+**   pzWhere: ...
+*/
+static char *rbuObjIterGetIndexCols(
+  sqlite3rbu *p,                  /* RBU object */
+  RbuObjIter *pIter,              /* Object iterator for column names */
+  char **pzImposterCols,          /* OUT: Columns for imposter table */
+  char **pzImposterPk,            /* OUT: Imposter PK clause */
+  char **pzWhere,                 /* OUT: WHERE clause */
+  int *pnBind                     /* OUT: Trbul number of columns */
+){
+  int rc = p->rc;                 /* Error code */
+  int rc2;                        /* sqlite3_finalize() return code */
+  char *zRet = 0;                 /* String to return */
+  char *zImpCols = 0;             /* String to return via *pzImposterCols */
+  char *zImpPK = 0;               /* String to return via *pzImposterPK */
+  char *zWhere = 0;               /* String to return via *pzWhere */
+  int nBind = 0;                  /* Value to return via *pnBind */
+  const char *zCom = "";          /* Set to ", " later on */
+  const char *zAnd = "";          /* Set to " AND " later on */
+  sqlite3_stmt *pXInfo = 0;       /* PRAGMA index_xinfo = ? */
 
-  /* Allocate the buffers used by this operation. The allocation is
-  ** relinquished before this function returns.
-  */
-  aCell = (RtreeCell *)sqlite3_malloc(n * (
-    sizeof(RtreeCell)     +         /* aCell array */
-    sizeof(int)           +         /* aOrder array */
-    sizeof(int)           +         /* aSpare array */
-    sizeof(RtreeDValue)             /* aDistance array */
-  ));
-  if( !aCell ){
-    return SQLITE_NOMEM;
+  if( rc==SQLITE_OK ){
+    assert( p->zErrmsg==0 );
+    rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
+        sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", pIter->zIdx)
+    );
   }
-  aOrder    = (int *)&aCell[n];
-  aSpare    = (int *)&aOrder[n];
-  aDistance = (RtreeDValue *)&aSpare[n];
 
-  for(ii=0; ii<nCell; ii++){
-    if( ii==(nCell-1) ){
-      memcpy(&aCell[ii], pCell, sizeof(RtreeCell));
+  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
+    int iCid = sqlite3_column_int(pXInfo, 1);
+    int bDesc = sqlite3_column_int(pXInfo, 3);
+    const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
+    const char *zCol;
+    const char *zType;
+
+    if( iCid<0 ){
+      /* An integer primary key. If the table has an explicit IPK, use
+      ** its name. Otherwise, use "rbu_rowid".  */
+      if( pIter->eType==RBU_PK_IPK ){
+        int i;
+        for(i=0; pIter->abTblPk[i]==0; i++);
+        assert( i<pIter->nTblCol );
+        zCol = pIter->azTblCol[i];
+      }else{
+        zCol = "rbu_rowid";
+      }
+      zType = "INTEGER";
     }else{
-      nodeGetCell(pRtree, pNode, ii, &aCell[ii]);
+      zCol = pIter->azTblCol[iCid];
+      zType = pIter->azTblType[iCid];
     }
-    aOrder[ii] = ii;
-    for(iDim=0; iDim<pRtree->nDim; iDim++){
-      aCenterCoord[iDim] += DCOORD(aCell[ii].aCoord[iDim*2]);
-      aCenterCoord[iDim] += DCOORD(aCell[ii].aCoord[iDim*2+1]);
+
+    zRet = sqlite3_mprintf("%z%s\"%w\" COLLATE %Q", zRet, zCom, zCol, zCollate);
+    if( pIter->bUnique==0 || sqlite3_column_int(pXInfo, 5) ){
+      const char *zOrder = (bDesc ? " DESC" : "");
+      zImpPK = sqlite3_mprintf("%z%s\"rbu_imp_%d%w\"%s", 
+          zImpPK, zCom, nBind, zCol, zOrder
+      );
     }
-  }
-  for(iDim=0; iDim<pRtree->nDim; iDim++){
-    aCenterCoord[iDim] = (aCenterCoord[iDim]/(nCell*(RtreeDValue)2));
+    zImpCols = sqlite3_mprintf("%z%s\"rbu_imp_%d%w\" %s COLLATE %Q", 
+        zImpCols, zCom, nBind, zCol, zType, zCollate
+    );
+    zWhere = sqlite3_mprintf(
+        "%z%s\"rbu_imp_%d%w\" IS ?", zWhere, zAnd, nBind, zCol
+    );
+    if( zRet==0 || zImpPK==0 || zImpCols==0 || zWhere==0 ) rc = SQLITE_NOMEM;
+    zCom = ", ";
+    zAnd = " AND ";
+    nBind++;
   }
 
-  for(ii=0; ii<nCell; ii++){
-    aDistance[ii] = RTREE_ZERO;
-    for(iDim=0; iDim<pRtree->nDim; iDim++){
-      RtreeDValue coord = (DCOORD(aCell[ii].aCoord[iDim*2+1]) - 
-                               DCOORD(aCell[ii].aCoord[iDim*2]));
-      aDistance[ii] += (coord-aCenterCoord[iDim])*(coord-aCenterCoord[iDim]);
-    }
+  rc2 = sqlite3_finalize(pXInfo);
+  if( rc==SQLITE_OK ) rc = rc2;
+
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(zRet);
+    sqlite3_free(zImpCols);
+    sqlite3_free(zImpPK);
+    sqlite3_free(zWhere);
+    zRet = 0;
+    zImpCols = 0;
+    zImpPK = 0;
+    zWhere = 0;
+    p->rc = rc;
   }
 
-  SortByDistance(aOrder, nCell, aDistance, aSpare);
-  nodeZero(pRtree, pNode);
+  *pzImposterCols = zImpCols;
+  *pzImposterPk = zImpPK;
+  *pzWhere = zWhere;
+  *pnBind = nBind;
+  return zRet;
+}
 
-  for(ii=0; rc==SQLITE_OK && ii<(nCell-(RTREE_MINCELLS(pRtree)+1)); ii++){
-    RtreeCell *p = &aCell[aOrder[ii]];
-    nodeInsertCell(pRtree, pNode, p);
-    if( p->iRowid==pCell->iRowid ){
-      if( iHeight==0 ){
-        rc = rowidWrite(pRtree, p->iRowid, pNode->iNode);
+/*
+** Assuming the current table columns are "a", "b" and "c", and the zObj
+** paramter is passed "old", return a string of the form:
+**
+**     "old.a, old.b, old.b"
+**
+** With the column names escaped.
+**
+** For tables with implicit rowids - RBU_PK_EXTERNAL and RBU_PK_NONE, append
+** the text ", old._rowid_" to the returned value.
+*/
+static char *rbuObjIterGetOldlist(
+  sqlite3rbu *p, 
+  RbuObjIter *pIter,
+  const char *zObj
+){
+  char *zList = 0;
+  if( p->rc==SQLITE_OK && pIter->abIndexed ){
+    const char *zS = "";
+    int i;
+    for(i=0; i<pIter->nTblCol; i++){
+      if( pIter->abIndexed[i] ){
+        const char *zCol = pIter->azTblCol[i];
+        zList = sqlite3_mprintf("%z%s%s.\"%w\"", zList, zS, zObj, zCol);
       }else{
-        rc = parentWrite(pRtree, p->iRowid, pNode->iNode);
+        zList = sqlite3_mprintf("%z%sNULL", zList, zS);
       }
-    }
-  }
-  if( rc==SQLITE_OK ){
-    rc = fixBoundingBox(pRtree, pNode);
-  }
-  for(; rc==SQLITE_OK && ii<nCell; ii++){
-    /* Find a node to store this cell in. pNode->iNode currently contains
-    ** the height of the sub-tree headed by the cell.
-    */
-    RtreeNode *pInsert;
-    RtreeCell *p = &aCell[aOrder[ii]];
-    rc = ChooseLeaf(pRtree, p, iHeight, &pInsert);
-    if( rc==SQLITE_OK ){
-      int rc2;
-      rc = rtreeInsertCell(pRtree, pInsert, p, iHeight);
-      rc2 = nodeRelease(pRtree, pInsert);
-      if( rc==SQLITE_OK ){
-        rc = rc2;
+      zS = ", ";
+      if( zList==0 ){
+        p->rc = SQLITE_NOMEM;
+        break;
       }
     }
-  }
 
-  sqlite3_free(aCell);
-  return rc;
+    /* For a table with implicit rowids, append "old._rowid_" to the list. */
+    if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
+      zList = rbuMPrintf(p, "%z, %s._rowid_", zList, zObj);
+    }
+  }
+  return zList;
 }
 
 /*
-** Insert cell pCell into node pNode. Node pNode is the head of a 
-** subtree iHeight high (leaf nodes have iHeight==0).
+** Return an expression that can be used in a WHERE clause to match the
+** primary key of the current table. For example, if the table is:
+**
+**   CREATE TABLE t1(a, b, c, PRIMARY KEY(b, c));
+**
+** Return the string:
+**
+**   "b = ?1 AND c = ?2"
 */
-static int rtreeInsertCell(
-  Rtree *pRtree,
-  RtreeNode *pNode,
-  RtreeCell *pCell,
-  int iHeight
+static char *rbuObjIterGetWhere(
+  sqlite3rbu *p, 
+  RbuObjIter *pIter
 ){
-  int rc = SQLITE_OK;
-  if( iHeight>0 ){
-    RtreeNode *pChild = nodeHashLookup(pRtree, pCell->iRowid);
-    if( pChild ){
-      nodeRelease(pRtree, pChild->pParent);
-      nodeReference(pNode);
-      pChild->pParent = pNode;
-    }
-  }
-  if( nodeInsertCell(pRtree, pNode, pCell) ){
-    if( iHeight<=pRtree->iReinsertHeight || pNode->iNode==1){
-      rc = SplitNode(pRtree, pNode, pCell, iHeight);
-    }else{
-      pRtree->iReinsertHeight = iHeight;
-      rc = Reinsert(pRtree, pNode, pCell, iHeight);
+  char *zList = 0;
+  if( pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE ){
+    zList = rbuMPrintf(p, "_rowid_ = ?%d", pIter->nTblCol+1);
+  }else if( pIter->eType==RBU_PK_EXTERNAL ){
+    const char *zSep = "";
+    int i;
+    for(i=0; i<pIter->nTblCol; i++){
+      if( pIter->abTblPk[i] ){
+        zList = rbuMPrintf(p, "%z%sc%d=?%d", zList, zSep, i, i+1);
+        zSep = " AND ";
+      }
     }
+    zList = rbuMPrintf(p, 
+        "_rowid_ = (SELECT id FROM rbu_imposter2 WHERE %z)", zList
+    );
+
   }else{
-    rc = AdjustTree(pRtree, pNode, pCell);
-    if( rc==SQLITE_OK ){
-      if( iHeight==0 ){
-        rc = rowidWrite(pRtree, pCell->iRowid, pNode->iNode);
-      }else{
-        rc = parentWrite(pRtree, pCell->iRowid, pNode->iNode);
+    const char *zSep = "";
+    int i;
+    for(i=0; i<pIter->nTblCol; i++){
+      if( pIter->abTblPk[i] ){
+        const char *zCol = pIter->azTblCol[i];
+        zList = rbuMPrintf(p, "%z%s\"%w\"=?%d", zList, zSep, zCol, i+1);
+        zSep = " AND ";
       }
     }
   }
-  return rc;
+  return zList;
 }
 
-static int reinsertNodeContent(Rtree *pRtree, RtreeNode *pNode){
-  int ii;
-  int rc = SQLITE_OK;
-  int nCell = NCELL(pNode);
+/*
+** The SELECT statement iterating through the keys for the current object
+** (p->objiter.pSelect) currently points to a valid row. However, there
+** is something wrong with the rbu_control value in the rbu_control value
+** stored in the (p->nCol+1)'th column. Set the error code and error message
+** of the RBU handle to something reflecting this.
+*/
+static void rbuBadControlError(sqlite3rbu *p){
+  p->rc = SQLITE_ERROR;
+  p->zErrmsg = sqlite3_mprintf("invalid rbu_control value");
+}
 
-  for(ii=0; rc==SQLITE_OK && ii<nCell; ii++){
-    RtreeNode *pInsert;
-    RtreeCell cell;
-    nodeGetCell(pRtree, pNode, ii, &cell);
 
-    /* Find a node to store this cell in. pNode->iNode currently contains
-    ** the height of the sub-tree headed by the cell.
-    */
-    rc = ChooseLeaf(pRtree, &cell, (int)pNode->iNode, &pInsert);
-    if( rc==SQLITE_OK ){
-      int rc2;
-      rc = rtreeInsertCell(pRtree, pInsert, &cell, (int)pNode->iNode);
-      rc2 = nodeRelease(pRtree, pInsert);
-      if( rc==SQLITE_OK ){
-        rc = rc2;
+/*
+** Return a nul-terminated string containing the comma separated list of
+** assignments that should be included following the "SET" keyword of
+** an UPDATE statement used to update the table object that the iterator
+** passed as the second argument currently points to if the rbu_control
+** column of the data_xxx table entry is set to zMask.
+**
+** The memory for the returned string is obtained from sqlite3_malloc().
+** It is the responsibility of the caller to eventually free it using
+** sqlite3_free(). 
+**
+** If an OOM error is encountered when allocating space for the new
+** string, an error code is left in the rbu handle passed as the first
+** argument and NULL is returned. Or, if an error has already occurred
+** when this function is called, NULL is returned immediately, without
+** attempting the allocation or modifying the stored error code.
+*/
+static char *rbuObjIterGetSetlist(
+  sqlite3rbu *p,
+  RbuObjIter *pIter,
+  const char *zMask
+){
+  char *zList = 0;
+  if( p->rc==SQLITE_OK ){
+    int i;
+
+    if( strlen(zMask)!=pIter->nTblCol ){
+      rbuBadControlError(p);
+    }else{
+      const char *zSep = "";
+      for(i=0; i<pIter->nTblCol; i++){
+        char c = zMask[pIter->aiSrcOrder[i]];
+        if( c=='x' ){
+          zList = rbuMPrintf(p, "%z%s\"%w\"=?%d", 
+              zList, zSep, pIter->azTblCol[i], i+1
+          );
+          zSep = ", ";
+        }
+        if( c=='d' ){
+          zList = rbuMPrintf(p, "%z%s\"%w\"=rbu_delta(\"%w\", ?%d)", 
+              zList, zSep, pIter->azTblCol[i], pIter->azTblCol[i], i+1
+          );
+          zSep = ", ";
+        }
       }
     }
   }
-  return rc;
+  return zList;
 }
 
 /*
-** Select a currently unused rowid for a new r-tree record.
+** Return a nul-terminated string consisting of nByte comma separated
+** "?" expressions. For example, if nByte is 3, return a pointer to
+** a buffer containing the string "?,?,?".
+**
+** The memory for the returned string is obtained from sqlite3_malloc().
+** It is the responsibility of the caller to eventually free it using
+** sqlite3_free(). 
+**
+** If an OOM error is encountered when allocating space for the new
+** string, an error code is left in the rbu handle passed as the first
+** argument and NULL is returned. Or, if an error has already occurred
+** when this function is called, NULL is returned immediately, without
+** attempting the allocation or modifying the stored error code.
 */
-static int newRowid(Rtree *pRtree, i64 *piRowid){
-  int rc;
-  sqlite3_bind_null(pRtree->pWriteRowid, 1);
-  sqlite3_bind_null(pRtree->pWriteRowid, 2);
-  sqlite3_step(pRtree->pWriteRowid);
-  rc = sqlite3_reset(pRtree->pWriteRowid);
-  *piRowid = sqlite3_last_insert_rowid(pRtree->db);
-  return rc;
+static char *rbuObjIterGetBindlist(sqlite3rbu *p, int nBind){
+  char *zRet = 0;
+  int nByte = nBind*2 + 1;
+
+  zRet = (char*)rbuMalloc(p, nByte);
+  if( zRet ){
+    int i;
+    for(i=0; i<nBind; i++){
+      zRet[i*2] = '?';
+      zRet[i*2+1] = (i+1==nBind) ? '\0' : ',';
+    }
+  }
+  return zRet;
 }
 
 /*
-** Remove the entry with rowid=iDelete from the r-tree structure.
+** The iterator currently points to a table (not index) of type 
+** RBU_PK_WITHOUT_ROWID. This function creates the PRIMARY KEY 
+** declaration for the corresponding imposter table. For example,
+** if the iterator points to a table created as:
+**
+**   CREATE TABLE t1(a, b, c, PRIMARY KEY(b, a DESC)) WITHOUT ROWID
+**
+** this function returns:
+**
+**   PRIMARY KEY("b", "a" DESC)
 */
-static int rtreeDeleteRowid(Rtree *pRtree, sqlite3_int64 iDelete){
-  int rc;                         /* Return code */
-  RtreeNode *pLeaf = 0;           /* Leaf node containing record iDelete */
-  int iCell;                      /* Index of iDelete cell in pLeaf */
-  RtreeNode *pRoot;               /* Root node of rtree structure */
-
-
-  /* Obtain a reference to the root node to initialize Rtree.iDepth */
-  rc = nodeAcquire(pRtree, 1, 0, &pRoot);
-
-  /* Obtain a reference to the leaf node that contains the entry 
-  ** about to be deleted. 
-  */
-  if( rc==SQLITE_OK ){
-    rc = findLeafNode(pRtree, iDelete, &pLeaf, 0);
-  }
-
-  /* Delete the cell in question from the leaf node. */
-  if( rc==SQLITE_OK ){
-    int rc2;
-    rc = nodeRowidIndex(pRtree, pLeaf, iDelete, &iCell);
-    if( rc==SQLITE_OK ){
-      rc = deleteCell(pRtree, pLeaf, iCell, 0);
+static char *rbuWithoutRowidPK(sqlite3rbu *p, RbuObjIter *pIter){
+  char *z = 0;
+  assert( pIter->zIdx==0 );
+  if( p->rc==SQLITE_OK ){
+    const char *zSep = "PRIMARY KEY(";
+    sqlite3_stmt *pXList = 0;     /* PRAGMA index_list = (pIter->zTbl) */
+    sqlite3_stmt *pXInfo = 0;     /* PRAGMA index_xinfo = <pk-index> */
+   
+    p->rc = prepareFreeAndCollectError(p->dbMain, &pXList, &p->zErrmsg,
+        sqlite3_mprintf("PRAGMA main.index_list = %Q", pIter->zTbl)
+    );
+    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXList) ){
+      const char *zOrig = (const char*)sqlite3_column_text(pXList,3);
+      if( zOrig && strcmp(zOrig, "pk")==0 ){
+        const char *zIdx = (const char*)sqlite3_column_text(pXList,1);
+        if( zIdx ){
+          p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
+              sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
+          );
+        }
+        break;
+      }
     }
-    rc2 = nodeRelease(pRtree, pLeaf);
-    if( rc==SQLITE_OK ){
-      rc = rc2;
+    rbuFinalize(p, pXList);
+
+    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
+      if( sqlite3_column_int(pXInfo, 5) ){
+        /* int iCid = sqlite3_column_int(pXInfo, 0); */
+        const char *zCol = (const char*)sqlite3_column_text(pXInfo, 2);
+        const char *zDesc = sqlite3_column_int(pXInfo, 3) ? " DESC" : "";
+        z = rbuMPrintf(p, "%z%s\"%w\"%s", z, zSep, zCol, zDesc);
+        zSep = ", ";
+      }
     }
+    z = rbuMPrintf(p, "%z)", z);
+    rbuFinalize(p, pXInfo);
   }
+  return z;
+}
 
-  /* Delete the corresponding entry in the <rtree>_rowid table. */
-  if( rc==SQLITE_OK ){
-    sqlite3_bind_int64(pRtree->pDeleteRowid, 1, iDelete);
-    sqlite3_step(pRtree->pDeleteRowid);
-    rc = sqlite3_reset(pRtree->pDeleteRowid);
-  }
+/*
+** This function creates the second imposter table used when writing to
+** a table b-tree where the table has an external primary key. If the
+** iterator passed as the second argument does not currently point to
+** a table (not index) with an external primary key, this function is a
+** no-op. 
+**
+** Assuming the iterator does point to a table with an external PK, this
+** function creates a WITHOUT ROWID imposter table named "rbu_imposter2"
+** used to access that PK index. For example, if the target table is
+** declared as follows:
+**
+**   CREATE TABLE t1(a, b TEXT, c REAL, PRIMARY KEY(b, c));
+**
+** then the imposter table schema is:
+**
+**   CREATE TABLE rbu_imposter2(c1 TEXT, c2 REAL, id INTEGER) WITHOUT ROWID;
+**
+*/
+static void rbuCreateImposterTable2(sqlite3rbu *p, RbuObjIter *pIter){
+  if( p->rc==SQLITE_OK && pIter->eType==RBU_PK_EXTERNAL ){
+    int tnum = pIter->iPkTnum;    /* Root page of PK index */
+    sqlite3_stmt *pQuery = 0;     /* SELECT name ... WHERE rootpage = $tnum */
+    const char *zIdx = 0;         /* Name of PK index */
+    sqlite3_stmt *pXInfo = 0;     /* PRAGMA main.index_xinfo = $zIdx */
+    const char *zComma = "";
+    char *zCols = 0;              /* Used to build up list of table cols */
+    char *zPk = 0;                /* Used to build up table PK declaration */
 
-  /* Check if the root node now has exactly one child. If so, remove
-  ** it, schedule the contents of the child for reinsertion and 
-  ** reduce the tree height by one.
-  **
-  ** This is equivalent to copying the contents of the child into
-  ** the root node (the operation that Gutman's paper says to perform 
-  ** in this scenario).
-  */
-  if( rc==SQLITE_OK && pRtree->iDepth>0 && NCELL(pRoot)==1 ){
-    int rc2;
-    RtreeNode *pChild;
-    i64 iChild = nodeGetRowid(pRtree, pRoot, 0);
-    rc = nodeAcquire(pRtree, iChild, pRoot, &pChild);
-    if( rc==SQLITE_OK ){
-      rc = removeNode(pRtree, pChild, pRtree->iDepth-1);
+    /* Figure out the name of the primary key index for the current table.
+    ** This is needed for the argument to "PRAGMA index_xinfo". Set
+    ** zIdx to point to a nul-terminated string containing this name. */
+    p->rc = prepareAndCollectError(p->dbMain, &pQuery, &p->zErrmsg, 
+        "SELECT name FROM sqlite_master WHERE rootpage = ?"
+    );
+    if( p->rc==SQLITE_OK ){
+      sqlite3_bind_int(pQuery, 1, tnum);
+      if( SQLITE_ROW==sqlite3_step(pQuery) ){
+        zIdx = (const char*)sqlite3_column_text(pQuery, 0);
+      }
     }
-    rc2 = nodeRelease(pRtree, pChild);
-    if( rc==SQLITE_OK ) rc = rc2;
-    if( rc==SQLITE_OK ){
-      pRtree->iDepth--;
-      writeInt16(pRoot->zData, pRtree->iDepth);
-      pRoot->isDirty = 1;
+    if( zIdx ){
+      p->rc = prepareFreeAndCollectError(p->dbMain, &pXInfo, &p->zErrmsg,
+          sqlite3_mprintf("PRAGMA main.index_xinfo = %Q", zIdx)
+      );
     }
-  }
+    rbuFinalize(p, pQuery);
 
-  /* Re-insert the contents of any underfull nodes removed from the tree. */
-  for(pLeaf=pRtree->pDeleted; pLeaf; pLeaf=pRtree->pDeleted){
-    if( rc==SQLITE_OK ){
-      rc = reinsertNodeContent(pRtree, pLeaf);
+    while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pXInfo) ){
+      int bKey = sqlite3_column_int(pXInfo, 5);
+      if( bKey ){
+        int iCid = sqlite3_column_int(pXInfo, 1);
+        int bDesc = sqlite3_column_int(pXInfo, 3);
+        const char *zCollate = (const char*)sqlite3_column_text(pXInfo, 4);
+        zCols = rbuMPrintf(p, "%z%sc%d %s COLLATE %s", zCols, zComma, 
+            iCid, pIter->azTblType[iCid], zCollate
+        );
+        zPk = rbuMPrintf(p, "%z%sc%d%s", zPk, zComma, iCid, bDesc?" DESC":"");
+        zComma = ", ";
+      }
     }
-    pRtree->pDeleted = pLeaf->pNext;
-    sqlite3_free(pLeaf);
-  }
+    zCols = rbuMPrintf(p, "%z, id INTEGER", zCols);
+    rbuFinalize(p, pXInfo);
 
-  /* Release the reference to the root node. */
-  if( rc==SQLITE_OK ){
-    rc = nodeRelease(pRtree, pRoot);
-  }else{
-    nodeRelease(pRtree, pRoot);
+    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1, tnum);
+    rbuMPrintfExec(p, p->dbMain,
+        "CREATE TABLE rbu_imposter2(%z, PRIMARY KEY(%z)) WITHOUT ROWID", 
+        zCols, zPk
+    );
+    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
   }
-
-  return rc;
 }
 
 /*
-** Rounding constants for float->double conversion.
-*/
-#define RNDTOWARDS  (1.0 - 1.0/8388608.0)  /* Round towards zero */
-#define RNDAWAY     (1.0 + 1.0/8388608.0)  /* Round away from zero */
+** If an error has already occurred when this function is called, it 
+** immediately returns zero (without doing any work). Or, if an error
+** occurs during the execution of this function, it sets the error code
+** in the sqlite3rbu object indicated by the first argument and returns
+** zero.
+**
+** The iterator passed as the second argument is guaranteed to point to
+** a table (not an index) when this function is called. This function
+** attempts to create any imposter table required to write to the main
+** table b-tree of the table before returning. Non-zero is returned if
+** an imposter table are created, or zero otherwise.
+**
+** An imposter table is required in all cases except RBU_PK_VTAB. Only
+** virtual tables are written to directly. The imposter table has the 
+** same schema as the actual target table (less any UNIQUE constraints). 
+** More precisely, the "same schema" means the same columns, types, 
+** collation sequences. For tables that do not have an external PRIMARY
+** KEY, it also means the same PRIMARY KEY declaration.
+*/
+static void rbuCreateImposterTable(sqlite3rbu *p, RbuObjIter *pIter){
+  if( p->rc==SQLITE_OK && pIter->eType!=RBU_PK_VTAB ){
+    int tnum = pIter->iTnum;
+    const char *zComma = "";
+    char *zSql = 0;
+    int iCol;
+    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);
+
+    for(iCol=0; p->rc==SQLITE_OK && iCol<pIter->nTblCol; iCol++){
+      const char *zPk = "";
+      const char *zCol = pIter->azTblCol[iCol];
+      const char *zColl = 0;
+
+      p->rc = sqlite3_table_column_metadata(
+          p->dbMain, "main", pIter->zTbl, zCol, 0, &zColl, 0, 0, 0
+      );
+
+      if( pIter->eType==RBU_PK_IPK && pIter->abTblPk[iCol] ){
+        /* If the target table column is an "INTEGER PRIMARY KEY", add
+        ** "PRIMARY KEY" to the imposter table column declaration. */
+        zPk = "PRIMARY KEY ";
+      }
+      zSql = rbuMPrintf(p, "%z%s\"%w\" %s %sCOLLATE %s%s", 
+          zSql, zComma, zCol, pIter->azTblType[iCol], zPk, zColl,
+          (pIter->abNotNull[iCol] ? " NOT NULL" : "")
+      );
+      zComma = ", ";
+    }
+
+    if( pIter->eType==RBU_PK_WITHOUT_ROWID ){
+      char *zPk = rbuWithoutRowidPK(p, pIter);
+      if( zPk ){
+        zSql = rbuMPrintf(p, "%z, %z", zSql, zPk);
+      }
+    }
+
+    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1, tnum);
+    rbuMPrintfExec(p, p->dbMain, "CREATE TABLE \"rbu_imp_%w\"(%z)%s", 
+        pIter->zTbl, zSql, 
+        (pIter->eType==RBU_PK_WITHOUT_ROWID ? " WITHOUT ROWID" : "")
+    );
+    sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
+  }
+}
 
-#if !defined(SQLITE_RTREE_INT_ONLY)
 /*
-** Convert an sqlite3_value into an RtreeValue (presumably a float)
-** while taking care to round toward negative or positive, respectively.
+** Prepare a statement used to insert rows into the "rbu_tmp_xxx" table.
+** Specifically a statement of the form:
+**
+**     INSERT INTO rbu_tmp_xxx VALUES(?, ?, ? ...);
+**
+** The number of bound variables is equal to the number of columns in
+** the target table, plus one (for the rbu_control column), plus one more 
+** (for the rbu_rowid column) if the target table is an implicit IPK or 
+** virtual table.
 */
-static RtreeValue rtreeValueDown(sqlite3_value *v){
-  double d = sqlite3_value_double(v);
-  float f = (float)d;
-  if( f>d ){
-    f = (float)(d*(d<0 ? RNDAWAY : RNDTOWARDS));
+static void rbuObjIterPrepareTmpInsert(
+  sqlite3rbu *p, 
+  RbuObjIter *pIter,
+  const char *zCollist,
+  const char *zRbuRowid
+){
+  int bRbuRowid = (pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE);
+  char *zBind = rbuObjIterGetBindlist(p, pIter->nTblCol + 1 + bRbuRowid);
+  if( zBind ){
+    assert( pIter->pTmpInsert==0 );
+    p->rc = prepareFreeAndCollectError(
+        p->dbRbu, &pIter->pTmpInsert, &p->zErrmsg, sqlite3_mprintf(
+          "INSERT INTO %s.'rbu_tmp_%q'(rbu_control,%s%s) VALUES(%z)", 
+          p->zStateDb, pIter->zTbl, zCollist, zRbuRowid, zBind
+    ));
   }
-  return f;
 }
-static RtreeValue rtreeValueUp(sqlite3_value *v){
-  double d = sqlite3_value_double(v);
-  float f = (float)d;
-  if( f<d ){
-    f = (float)(d*(d<0 ? RNDTOWARDS : RNDAWAY));
+
+static void rbuTmpInsertFunc(
+  sqlite3_context *pCtx, 
+  int nVal,
+  sqlite3_value **apVal
+){
+  sqlite3rbu *p = sqlite3_user_data(pCtx);
+  int rc = SQLITE_OK;
+  int i;
+
+  for(i=0; rc==SQLITE_OK && i<nVal; i++){
+    rc = sqlite3_bind_value(p->objiter.pTmpInsert, i+1, apVal[i]);
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3_step(p->objiter.pTmpInsert);
+    rc = sqlite3_reset(p->objiter.pTmpInsert);
   }
-  return f;
-}
-#endif /* !defined(SQLITE_RTREE_INT_ONLY) */
 
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error_code(pCtx, rc);
+  }
+}
 
 /*
-** The xUpdate method for rtree module virtual tables.
+** Ensure that the SQLite statement handles required to update the 
+** target database object currently indicated by the iterator passed 
+** as the second argument are available.
 */
-static int rtreeUpdate(
-  sqlite3_vtab *pVtab, 
-  int nData, 
-  sqlite3_value **azData, 
-  sqlite_int64 *pRowid
+static int rbuObjIterPrepareAll(
+  sqlite3rbu *p, 
+  RbuObjIter *pIter,
+  int nOffset                     /* Add "LIMIT -1 OFFSET $nOffset" to SELECT */
 ){
-  Rtree *pRtree = (Rtree *)pVtab;
-  int rc = SQLITE_OK;
-  RtreeCell cell;                 /* New cell to insert if nData>1 */
-  int bHaveRowid = 0;             /* Set to 1 after new rowid is determined */
+  assert( pIter->bCleanup==0 );
+  if( pIter->pSelect==0 && rbuObjIterCacheTableInfo(p, pIter)==SQLITE_OK ){
+    const int tnum = pIter->iTnum;
+    char *zCollist = 0;           /* List of indexed columns */
+    char **pz = &p->zErrmsg;
+    const char *zIdx = pIter->zIdx;
+    char *zLimit = 0;
 
-  rtreeReference(pRtree);
-  assert(nData>=1);
+    if( nOffset ){
+      zLimit = sqlite3_mprintf(" LIMIT -1 OFFSET %d", nOffset);
+      if( !zLimit ) p->rc = SQLITE_NOMEM;
+    }
 
-  cell.iRowid = 0;  /* Used only to suppress a compiler warning */
+    if( zIdx ){
+      const char *zTbl = pIter->zTbl;
+      char *zImposterCols = 0;    /* Columns for imposter table */
+      char *zImposterPK = 0;      /* Primary key declaration for imposter */
+      char *zWhere = 0;           /* WHERE clause on PK columns */
+      char *zBind = 0;
+      int nBind = 0;
 
-  /* Constraint handling. A write operation on an r-tree table may return
-  ** SQLITE_CONSTRAINT for two reasons:
-  **
-  **   1. A duplicate rowid value, or
-  **   2. The supplied data violates the "x2>=x1" constraint.
-  **
-  ** In the first case, if the conflict-handling mode is REPLACE, then
-  ** the conflicting row can be removed before proceeding. In the second
-  ** case, SQLITE_CONSTRAINT must be returned regardless of the
-  ** conflict-handling mode specified by the user.
-  */
-  if( nData>1 ){
-    int ii;
+      assert( pIter->eType!=RBU_PK_VTAB );
+      zCollist = rbuObjIterGetIndexCols(
+          p, pIter, &zImposterCols, &zImposterPK, &zWhere, &nBind
+      );
+      zBind = rbuObjIterGetBindlist(p, nBind);
+
+      /* Create the imposter table used to write to this index. */
+      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 1);
+      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 1,tnum);
+      rbuMPrintfExec(p, p->dbMain,
+          "CREATE TABLE \"rbu_imp_%w\"( %s, PRIMARY KEY( %s ) ) WITHOUT ROWID",
+          zTbl, zImposterCols, zImposterPK
+      );
+      sqlite3_test_control(SQLITE_TESTCTRL_IMPOSTER, p->dbMain, "main", 0, 0);
+
+      /* Create the statement to insert index entries */
+      pIter->nCol = nBind;
+      if( p->rc==SQLITE_OK ){
+        p->rc = prepareFreeAndCollectError(
+            p->dbMain, &pIter->pInsert, &p->zErrmsg,
+          sqlite3_mprintf("INSERT INTO \"rbu_imp_%w\" VALUES(%s)", zTbl, zBind)
+        );
+      }
 
-    /* Populate the cell.aCoord[] array. The first coordinate is azData[3].
-    **
-    ** NB: nData can only be less than nDim*2+3 if the rtree is mis-declared
-    ** with "column" that are interpreted as table constraints.
-    ** Example:  CREATE VIRTUAL TABLE bad USING rtree(x,y,CHECK(y>5));
-    ** This problem was discovered after years of use, so we silently ignore
-    ** these kinds of misdeclared tables to avoid breaking any legacy.
-    */
-    assert( nData<=(pRtree->nDim*2 + 3) );
+      /* And to delete index entries */
+      if( p->rc==SQLITE_OK ){
+        p->rc = prepareFreeAndCollectError(
+            p->dbMain, &pIter->pDelete, &p->zErrmsg,
+          sqlite3_mprintf("DELETE FROM \"rbu_imp_%w\" WHERE %s", zTbl, zWhere)
+        );
+      }
 
-#ifndef SQLITE_RTREE_INT_ONLY
-    if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
-      for(ii=0; ii<nData-4; ii+=2){
-        cell.aCoord[ii].f = rtreeValueDown(azData[ii+3]);
-        cell.aCoord[ii+1].f = rtreeValueUp(azData[ii+4]);
-        if( cell.aCoord[ii].f>cell.aCoord[ii+1].f ){
-          rc = SQLITE_CONSTRAINT;
-          goto constraint;
+      /* Create the SELECT statement to read keys in sorted order */
+      if( p->rc==SQLITE_OK ){
+        char *zSql;
+        if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
+          zSql = sqlite3_mprintf(
+              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' ORDER BY %s%s",
+              zCollist, p->zStateDb, pIter->zTbl,
+              zCollist, zLimit
+          );
+        }else{
+          zSql = sqlite3_mprintf(
+              "SELECT %s, rbu_control FROM 'data_%q' "
+              "WHERE typeof(rbu_control)='integer' AND rbu_control!=1 "
+              "UNION ALL "
+              "SELECT %s, rbu_control FROM %s.'rbu_tmp_%q' "
+              "ORDER BY %s%s",
+              zCollist, pIter->zTbl, 
+              zCollist, p->zStateDb, pIter->zTbl, 
+              zCollist, zLimit
+          );
         }
+        p->rc = prepareFreeAndCollectError(p->dbRbu, &pIter->pSelect, pz, zSql);
       }
-    }else
-#endif
-    {
-      for(ii=0; ii<nData-4; ii+=2){
-        cell.aCoord[ii].i = sqlite3_value_int(azData[ii+3]);
-        cell.aCoord[ii+1].i = sqlite3_value_int(azData[ii+4]);
-        if( cell.aCoord[ii].i>cell.aCoord[ii+1].i ){
-          rc = SQLITE_CONSTRAINT;
-          goto constraint;
-        }
+
+      sqlite3_free(zImposterCols);
+      sqlite3_free(zImposterPK);
+      sqlite3_free(zWhere);
+      sqlite3_free(zBind);
+    }else{
+      int bRbuRowid = (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE);
+      const char *zTbl = pIter->zTbl;       /* Table this step applies to */
+      const char *zWrite;                   /* Imposter table name */
+
+      char *zBindings = rbuObjIterGetBindlist(p, pIter->nTblCol + bRbuRowid);
+      char *zWhere = rbuObjIterGetWhere(p, pIter);
+      char *zOldlist = rbuObjIterGetOldlist(p, pIter, "old");
+      char *zNewlist = rbuObjIterGetOldlist(p, pIter, "new");
+
+      zCollist = rbuObjIterGetCollist(p, pIter);
+      pIter->nCol = pIter->nTblCol;
+
+      /* Create the SELECT statement to read keys from data_xxx */
+      if( p->rc==SQLITE_OK ){
+        p->rc = prepareFreeAndCollectError(p->dbRbu, &pIter->pSelect, pz,
+            sqlite3_mprintf(
+              "SELECT %s, rbu_control%s FROM 'data_%q'%s", 
+              zCollist, (bRbuRowid ? ", rbu_rowid" : ""), zTbl, zLimit
+            )
+        );
       }
-    }
 
-    /* If a rowid value was supplied, check if it is already present in 
-    ** the table. If so, the constraint has failed. */
-    if( sqlite3_value_type(azData[2])!=SQLITE_NULL ){
-      cell.iRowid = sqlite3_value_int64(azData[2]);
-      if( sqlite3_value_type(azData[0])==SQLITE_NULL
-       || sqlite3_value_int64(azData[0])!=cell.iRowid
-      ){
-        int steprc;
-        sqlite3_bind_int64(pRtree->pReadRowid, 1, cell.iRowid);
-        steprc = sqlite3_step(pRtree->pReadRowid);
-        rc = sqlite3_reset(pRtree->pReadRowid);
-        if( SQLITE_ROW==steprc ){
-          if( sqlite3_vtab_on_conflict(pRtree->db)==SQLITE_REPLACE ){
-            rc = rtreeDeleteRowid(pRtree, cell.iRowid);
-          }else{
-            rc = SQLITE_CONSTRAINT;
-            goto constraint;
-          }
-        }
+      /* Create the imposter table or tables (if required). */
+      rbuCreateImposterTable(p, pIter);
+      rbuCreateImposterTable2(p, pIter);
+      zWrite = (pIter->eType==RBU_PK_VTAB ? "" : "rbu_imp_");
+
+      /* Create the INSERT statement to write to the target PK b-tree */
+      if( p->rc==SQLITE_OK ){
+        p->rc = prepareFreeAndCollectError(p->dbMain, &pIter->pInsert, pz,
+            sqlite3_mprintf(
+              "INSERT INTO \"%s%w\"(%s%s) VALUES(%s)", 
+              zWrite, zTbl, zCollist, (bRbuRowid ? ", _rowid_" : ""), zBindings
+            )
+        );
       }
-      bHaveRowid = 1;
-    }
-  }
 
-  /* If azData[0] is not an SQL NULL value, it is the rowid of a
-  ** record to delete from the r-tree table. The following block does
-  ** just that.
-  */
-  if( sqlite3_value_type(azData[0])!=SQLITE_NULL ){
-    rc = rtreeDeleteRowid(pRtree, sqlite3_value_int64(azData[0]));
-  }
+      /* Create the DELETE statement to write to the target PK b-tree */
+      if( p->rc==SQLITE_OK ){
+        p->rc = prepareFreeAndCollectError(p->dbMain, &pIter->pDelete, pz,
+            sqlite3_mprintf(
+              "DELETE FROM \"%s%w\" WHERE %s", zWrite, zTbl, zWhere
+            )
+        );
+      }
 
-  /* If the azData[] array contains more than one element, elements
-  ** (azData[2]..azData[argc-1]) contain a new record to insert into
-  ** the r-tree structure.
-  */
-  if( rc==SQLITE_OK && nData>1 ){
-    /* Insert the new record into the r-tree */
-    RtreeNode *pLeaf = 0;
+      if( pIter->abIndexed ){
+        const char *zRbuRowid = "";
+        if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
+          zRbuRowid = ", rbu_rowid";
+        }
 
-    /* Figure out the rowid of the new row. */
-    if( bHaveRowid==0 ){
-      rc = newRowid(pRtree, &cell.iRowid);
-    }
-    *pRowid = cell.iRowid;
+        /* Create the rbu_tmp_xxx table and the triggers to populate it. */
+        rbuMPrintfExec(p, p->dbRbu,
+            "CREATE TABLE IF NOT EXISTS %s.'rbu_tmp_%q' AS "
+            "SELECT *%s FROM 'data_%q' WHERE 0;"
+            , p->zStateDb
+            , zTbl, (pIter->eType==RBU_PK_EXTERNAL ? ", 0 AS rbu_rowid" : "")
+            , zTbl
+        );
 
-    if( rc==SQLITE_OK ){
-      rc = ChooseLeaf(pRtree, &cell, 0, &pLeaf);
-    }
-    if( rc==SQLITE_OK ){
-      int rc2;
-      pRtree->iReinsertHeight = -1;
-      rc = rtreeInsertCell(pRtree, pLeaf, &cell, 0);
-      rc2 = nodeRelease(pRtree, pLeaf);
-      if( rc==SQLITE_OK ){
-        rc = rc2;
+        rbuMPrintfExec(p, p->dbMain,
+            "CREATE TEMP TRIGGER rbu_delete_tr BEFORE DELETE ON \"%s%w\" "
+            "BEGIN "
+            "  SELECT rbu_tmp_insert(2, %s);"
+            "END;"
+
+            "CREATE TEMP TRIGGER rbu_update1_tr BEFORE UPDATE ON \"%s%w\" "
+            "BEGIN "
+            "  SELECT rbu_tmp_insert(2, %s);"
+            "END;"
+
+            "CREATE TEMP TRIGGER rbu_update2_tr AFTER UPDATE ON \"%s%w\" "
+            "BEGIN "
+            "  SELECT rbu_tmp_insert(3, %s);"
+            "END;",
+            zWrite, zTbl, zOldlist,
+            zWrite, zTbl, zOldlist,
+            zWrite, zTbl, zNewlist
+        );
+
+        if( pIter->eType==RBU_PK_EXTERNAL || pIter->eType==RBU_PK_NONE ){
+          rbuMPrintfExec(p, p->dbMain,
+              "CREATE TEMP TRIGGER rbu_insert_tr AFTER INSERT ON \"%s%w\" "
+              "BEGIN "
+              "  SELECT rbu_tmp_insert(0, %s);"
+              "END;",
+              zWrite, zTbl, zNewlist
+          );
+        }
+
+        rbuObjIterPrepareTmpInsert(p, pIter, zCollist, zRbuRowid);
       }
+
+      sqlite3_free(zWhere);
+      sqlite3_free(zOldlist);
+      sqlite3_free(zNewlist);
+      sqlite3_free(zBindings);
     }
+    sqlite3_free(zCollist);
+    sqlite3_free(zLimit);
   }
-
-constraint:
-  rtreeRelease(pRtree);
-  return rc;
+  
+  return p->rc;
 }
 
 /*
-** The xRename method for rtree module virtual tables.
+** Set output variable *ppStmt to point to an UPDATE statement that may
+** be used to update the imposter table for the main table b-tree of the
+** table object that pIter currently points to, assuming that the 
+** rbu_control column of the data_xyz table contains zMask.
+** 
+** If the zMask string does not specify any columns to update, then this
+** is not an error. Output variable *ppStmt is set to NULL in this case.
 */
-static int rtreeRename(sqlite3_vtab *pVtab, const char *zNewName){
-  Rtree *pRtree = (Rtree *)pVtab;
-  int rc = SQLITE_NOMEM;
-  char *zSql = sqlite3_mprintf(
-    "ALTER TABLE %Q.'%q_node'   RENAME TO \"%w_node\";"
-    "ALTER TABLE %Q.'%q_parent' RENAME TO \"%w_parent\";"
-    "ALTER TABLE %Q.'%q_rowid'  RENAME TO \"%w_rowid\";"
-    , pRtree->zDb, pRtree->zName, zNewName 
-    , pRtree->zDb, pRtree->zName, zNewName 
-    , pRtree->zDb, pRtree->zName, zNewName
-  );
-  if( zSql ){
-    rc = sqlite3_exec(pRtree->db, zSql, 0, 0, 0);
-    sqlite3_free(zSql);
-  }
-  return rc;
-}
+static int rbuGetUpdateStmt(
+  sqlite3rbu *p,                  /* RBU handle */
+  RbuObjIter *pIter,              /* Object iterator */
+  const char *zMask,              /* rbu_control value ('x.x.') */
+  sqlite3_stmt **ppStmt           /* OUT: UPDATE statement handle */
+){
+  RbuUpdateStmt **pp;
+  RbuUpdateStmt *pUp = 0;
+  int nUp = 0;
 
-/*
-** This function populates the pRtree->nRowEst variable with an estimate
-** of the number of rows in the virtual table. If possible, this is based
-** on sqlite_stat1 data. Otherwise, use RTREE_DEFAULT_ROWEST.
-*/
-static int rtreeQueryStat1(sqlite3 *db, Rtree *pRtree){
-  const char *zFmt = "SELECT stat FROM %Q.sqlite_stat1 WHERE tbl = '%q_rowid'";
-  char *zSql;
-  sqlite3_stmt *p;
-  int rc;
-  i64 nRow = 0;
+  /* In case an error occurs */
+  *ppStmt = 0;
 
-  zSql = sqlite3_mprintf(zFmt, pRtree->zDb, pRtree->zName);
-  if( zSql==0 ){
-    rc = SQLITE_NOMEM;
-  }else{
-    rc = sqlite3_prepare_v2(db, zSql, -1, &p, 0);
-    if( rc==SQLITE_OK ){
-      if( sqlite3_step(p)==SQLITE_ROW ) nRow = sqlite3_column_int64(p, 0);
-      rc = sqlite3_finalize(p);
-    }else if( rc!=SQLITE_NOMEM ){
-      rc = SQLITE_OK;
+  /* Search for an existing statement. If one is found, shift it to the front
+  ** of the LRU queue and return immediately. Otherwise, leave nUp pointing
+  ** to the number of statements currently in the cache and pUp to the
+  ** last object in the list.  */
+  for(pp=&pIter->pRbuUpdate; *pp; pp=&((*pp)->pNext)){
+    pUp = *pp;
+    if( strcmp(pUp->zMask, zMask)==0 ){
+      *pp = pUp->pNext;
+      pUp->pNext = pIter->pRbuUpdate;
+      pIter->pRbuUpdate = pUp;
+      *ppStmt = pUp->pUpdate; 
+      return SQLITE_OK;
     }
+    nUp++;
+  }
+  assert( pUp==0 || pUp->pNext==0 );
 
-    if( rc==SQLITE_OK ){
-      if( nRow==0 ){
-        pRtree->nRowEst = RTREE_DEFAULT_ROWEST;
-      }else{
-        pRtree->nRowEst = MAX(nRow, RTREE_MIN_ROWEST);
-      }
-    }
-    sqlite3_free(zSql);
+  if( nUp>=SQLITE_RBU_UPDATE_CACHESIZE ){
+    for(pp=&pIter->pRbuUpdate; *pp!=pUp; pp=&((*pp)->pNext));
+    *pp = 0;
+    sqlite3_finalize(pUp->pUpdate);
+    pUp->pUpdate = 0;
+  }else{
+    pUp = (RbuUpdateStmt*)rbuMalloc(p, sizeof(RbuUpdateStmt)+pIter->nTblCol+1);
   }
 
-  return rc;
-}
+  if( pUp ){
+    char *zWhere = rbuObjIterGetWhere(p, pIter);
+    char *zSet = rbuObjIterGetSetlist(p, pIter, zMask);
+    char *zUpdate = 0;
 
-static sqlite3_module rtreeModule = {
-  0,                          /* iVersion */
-  rtreeCreate,                /* xCreate - create a table */
-  rtreeConnect,               /* xConnect - connect to an existing table */
-  rtreeBestIndex,             /* xBestIndex - Determine search strategy */
-  rtreeDisconnect,            /* xDisconnect - Disconnect from a table */
-  rtreeDestroy,               /* xDestroy - Drop a table */
-  rtreeOpen,                  /* xOpen - open a cursor */
-  rtreeClose,                 /* xClose - close a cursor */
-  rtreeFilter,                /* xFilter - configure scan constraints */
-  rtreeNext,                  /* xNext - advance a cursor */
-  rtreeEof,                   /* xEof */
-  rtreeColumn,                /* xColumn - read data */
-  rtreeRowid,                 /* xRowid - read data */
-  rtreeUpdate,                /* xUpdate - write data */
-  0,                          /* xBegin - begin transaction */
-  0,                          /* xSync - sync transaction */
-  0,                          /* xCommit - commit transaction */
-  0,                          /* xRollback - rollback transaction */
-  0,                          /* xFindFunction - function overloading */
-  rtreeRename,                /* xRename - rename the table */
-  0,                          /* xSavepoint */
-  0,                          /* xRelease */
-  0                           /* xRollbackTo */
-};
+    pUp->zMask = (char*)&pUp[1];
+    memcpy(pUp->zMask, zMask, pIter->nTblCol);
+    pUp->pNext = pIter->pRbuUpdate;
+    pIter->pRbuUpdate = pUp;
 
-static int rtreeSqlInit(
-  Rtree *pRtree, 
-  sqlite3 *db, 
-  const char *zDb, 
-  const char *zPrefix, 
-  int isCreate
-){
-  int rc = SQLITE_OK;
+    if( zSet ){
+      const char *zPrefix = "";
 
-  #define N_STATEMENT 9
-  static const char *azSql[N_STATEMENT] = {
-    /* Read and write the xxx_node table */
-    "SELECT data FROM '%q'.'%q_node' WHERE nodeno = :1",
-    "INSERT OR REPLACE INTO '%q'.'%q_node' VALUES(:1, :2)",
-    "DELETE FROM '%q'.'%q_node' WHERE nodeno = :1",
+      if( pIter->eType!=RBU_PK_VTAB ) zPrefix = "rbu_imp_";
+      zUpdate = sqlite3_mprintf("UPDATE \"%s%w\" SET %s WHERE %s", 
+          zPrefix, pIter->zTbl, zSet, zWhere
+      );
+      p->rc = prepareFreeAndCollectError(
+          p->dbMain, &pUp->pUpdate, &p->zErrmsg, zUpdate
+      );
+      *ppStmt = pUp->pUpdate;
+    }
+    sqlite3_free(zWhere);
+    sqlite3_free(zSet);
+  }
 
-    /* Read and write the xxx_rowid table */
-    "SELECT nodeno FROM '%q'.'%q_rowid' WHERE rowid = :1",
-    "INSERT OR REPLACE INTO '%q'.'%q_rowid' VALUES(:1, :2)",
-    "DELETE FROM '%q'.'%q_rowid' WHERE rowid = :1",
+  return p->rc;
+}
 
-    /* Read and write the xxx_parent table */
-    "SELECT parentnode FROM '%q'.'%q_parent' WHERE nodeno = :1",
-    "INSERT OR REPLACE INTO '%q'.'%q_parent' VALUES(:1, :2)",
-    "DELETE FROM '%q'.'%q_parent' WHERE nodeno = :1"
-  };
-  sqlite3_stmt **appStmt[N_STATEMENT];
-  int i;
+static sqlite3 *rbuOpenDbhandle(sqlite3rbu *p, const char *zName){
+  sqlite3 *db = 0;
+  if( p->rc==SQLITE_OK ){
+    const int flags = SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_URI;
+    p->rc = sqlite3_open_v2(zName, &db, flags, p->zVfsName);
+    if( p->rc ){
+      p->zErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+      sqlite3_close(db);
+      db = 0;
+    }
+  }
+  return db;
+}
 
-  pRtree->db = db;
+/*
+** Open the database handle and attach the RBU database as "rbu". If an
+** error occurs, leave an error code and message in the RBU handle.
+*/
+static void rbuOpenDatabase(sqlite3rbu *p){
+  assert( p->rc==SQLITE_OK );
+  assert( p->dbMain==0 && p->dbRbu==0 );
 
-  if( isCreate ){
-    char *zCreate = sqlite3_mprintf(
-"CREATE TABLE \"%w\".\"%w_node\"(nodeno INTEGER PRIMARY KEY, data BLOB);"
-"CREATE TABLE \"%w\".\"%w_rowid\"(rowid INTEGER PRIMARY KEY, nodeno INTEGER);"
-"CREATE TABLE \"%w\".\"%w_parent\"(nodeno INTEGER PRIMARY KEY,"
-                                  " parentnode INTEGER);"
-"INSERT INTO '%q'.'%q_node' VALUES(1, zeroblob(%d))",
-      zDb, zPrefix, zDb, zPrefix, zDb, zPrefix, zDb, zPrefix, pRtree->iNodeSize
+  p->eStage = 0;
+  p->dbMain = rbuOpenDbhandle(p, p->zTarget);
+  p->dbRbu = rbuOpenDbhandle(p, p->zRbu);
+
+  /* If using separate RBU and state databases, attach the state database to
+  ** the RBU db handle now.  */
+  if( p->zState ){
+    rbuMPrintfExec(p, p->dbRbu, "ATTACH %Q AS stat", p->zState);
+    memcpy(p->zStateDb, "stat", 4);
+  }else{
+    memcpy(p->zStateDb, "main", 4);
+  }
+
+  if( p->rc==SQLITE_OK ){
+    p->rc = sqlite3_create_function(p->dbMain, 
+        "rbu_tmp_insert", -1, SQLITE_UTF8, (void*)p, rbuTmpInsertFunc, 0, 0
     );
-    if( !zCreate ){
-      return SQLITE_NOMEM;
-    }
-    rc = sqlite3_exec(db, zCreate, 0, 0, 0);
-    sqlite3_free(zCreate);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
   }
 
-  appStmt[0] = &pRtree->pReadNode;
-  appStmt[1] = &pRtree->pWriteNode;
-  appStmt[2] = &pRtree->pDeleteNode;
-  appStmt[3] = &pRtree->pReadRowid;
-  appStmt[4] = &pRtree->pWriteRowid;
-  appStmt[5] = &pRtree->pDeleteRowid;
-  appStmt[6] = &pRtree->pReadParent;
-  appStmt[7] = &pRtree->pWriteParent;
-  appStmt[8] = &pRtree->pDeleteParent;
+  if( p->rc==SQLITE_OK ){
+    p->rc = sqlite3_file_control(p->dbMain, "main", SQLITE_FCNTL_RBU, (void*)p);
+  }
+  rbuMPrintfExec(p, p->dbMain, "SELECT * FROM sqlite_master");
 
-  rc = rtreeQueryStat1(db, pRtree);
-  for(i=0; i<N_STATEMENT && rc==SQLITE_OK; i++){
-    char *zSql = sqlite3_mprintf(azSql[i], zDb, zPrefix);
-    if( zSql ){
-      rc = sqlite3_prepare_v2(db, zSql, -1, appStmt[i], 0); 
-    }else{
-      rc = SQLITE_NOMEM;
-    }
-    sqlite3_free(zSql);
+  /* Mark the database file just opened as an RBU target database. If 
+  ** this call returns SQLITE_NOTFOUND, then the RBU vfs is not in use.
+  ** This is an error.  */
+  if( p->rc==SQLITE_OK ){
+    p->rc = sqlite3_file_control(p->dbMain, "main", SQLITE_FCNTL_RBU, (void*)p);
   }
 
-  return rc;
+  if( p->rc==SQLITE_NOTFOUND ){
+    p->rc = SQLITE_ERROR;
+    p->zErrmsg = sqlite3_mprintf("rbu vfs not found");
+  }
 }
 
 /*
-** The second argument to this function contains the text of an SQL statement
-** that returns a single integer value. The statement is compiled and executed
-** using database connection db. If successful, the integer value returned
-** is written to *piVal and SQLITE_OK returned. Otherwise, an SQLite error
-** code is returned and the value of *piVal after returning is not defined.
+** This routine is a copy of the sqlite3FileSuffix3() routine from the core.
+** It is a no-op unless SQLITE_ENABLE_8_3_NAMES is defined.
+**
+** If SQLITE_ENABLE_8_3_NAMES is set at compile-time and if the database
+** filename in zBaseFilename is a URI with the "8_3_names=1" parameter and
+** if filename in z[] has a suffix (a.k.a. "extension") that is longer than
+** three characters, then shorten the suffix on z[] to be the last three
+** characters of the original suffix.
+**
+** If SQLITE_ENABLE_8_3_NAMES is set to 2 at compile-time, then always
+** do the suffix shortening regardless of URI parameter.
+**
+** Examples:
+**
+**     test.db-journal    =>   test.nal
+**     test.db-wal        =>   test.wal
+**     test.db-shm        =>   test.shm
+**     test.db-mj7f3319fa =>   test.9fa
 */
-static int getIntFromStmt(sqlite3 *db, const char *zSql, int *piVal){
-  int rc = SQLITE_NOMEM;
-  if( zSql ){
-    sqlite3_stmt *pStmt = 0;
-    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
-    if( rc==SQLITE_OK ){
-      if( SQLITE_ROW==sqlite3_step(pStmt) ){
-        *piVal = sqlite3_column_int(pStmt, 0);
-      }
-      rc = sqlite3_finalize(pStmt);
+static void rbuFileSuffix3(const char *zBase, char *z){
+#ifdef SQLITE_ENABLE_8_3_NAMES
+#if SQLITE_ENABLE_8_3_NAMES<2
+  if( sqlite3_uri_boolean(zBase, "8_3_names", 0) )
+#endif
+  {
+    int i, sz;
+    sz = sqlite3Strlen30(z);
+    for(i=sz-1; i>0 && z[i]!='/' && z[i]!='.'; i--){}
+    if( z[i]=='.' && ALWAYS(sz>i+4) ) memmove(&z[i+1], &z[sz-3], 4);
+  }
+#endif
+}
+
+/*
+** Return the current wal-index header checksum for the target database 
+** as a 64-bit integer.
+**
+** The checksum is store in the first page of xShmMap memory as an 8-byte 
+** blob starting at byte offset 40.
+*/
+static i64 rbuShmChecksum(sqlite3rbu *p){
+  i64 iRet = 0;
+  if( p->rc==SQLITE_OK ){
+    sqlite3_file *pDb = p->pTargetFd->pReal;
+    u32 volatile *ptr;
+    p->rc = pDb->pMethods->xShmMap(pDb, 0, 32*1024, 0, (void volatile**)&ptr);
+    if( p->rc==SQLITE_OK ){
+      iRet = ((i64)ptr[10] << 32) + ptr[11];
     }
   }
-  return rc;
+  return iRet;
 }
 
 /*
-** This function is called from within the xConnect() or xCreate() method to
-** determine the node-size used by the rtree table being created or connected
-** to. If successful, pRtree->iNodeSize is populated and SQLITE_OK returned.
-** Otherwise, an SQLite error code is returned.
+** This function is called as part of initializing or reinitializing an
+** incremental checkpoint. 
 **
-** If this function is being called as part of an xConnect(), then the rtree
-** table already exists. In this case the node-size is determined by inspecting
-** the root node of the tree.
+** It populates the sqlite3rbu.aFrame[] array with the set of 
+** (wal frame -> db page) copy operations required to checkpoint the 
+** current wal file, and obtains the set of shm locks required to safely 
+** perform the copy operations directly on the file-system.
 **
-** Otherwise, for an xCreate(), use 64 bytes less than the database page-size. 
-** This ensures that each node is stored on a single database page. If the 
-** database page-size is so large that more than RTREE_MAXCELLS entries 
-** would fit in a single node, use a smaller node-size.
+** If argument pState is not NULL, then the incremental checkpoint is
+** being resumed. In this case, if the checksum of the wal-index-header
+** following recovery is not the same as the checksum saved in the RbuState
+** object, then the rbu handle is set to DONE state. This occurs if some
+** other client appends a transaction to the wal file in the middle of
+** an incremental checkpoint.
 */
-static int getNodeSize(
-  sqlite3 *db,                    /* Database handle */
-  Rtree *pRtree,                  /* Rtree handle */
-  int isCreate,                   /* True for xCreate, false for xConnect */
-  char **pzErr                    /* OUT: Error message, if any */
-){
-  int rc;
-  char *zSql;
-  if( isCreate ){
-    int iPageSize = 0;
-    zSql = sqlite3_mprintf("PRAGMA %Q.page_size", pRtree->zDb);
-    rc = getIntFromStmt(db, zSql, &iPageSize);
-    if( rc==SQLITE_OK ){
-      pRtree->iNodeSize = iPageSize-64;
-      if( (4+pRtree->nBytesPerCell*RTREE_MAXCELLS)<pRtree->iNodeSize ){
-        pRtree->iNodeSize = 4+pRtree->nBytesPerCell*RTREE_MAXCELLS;
-      }
-    }else{
-      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
-    }
-  }else{
-    zSql = sqlite3_mprintf(
-        "SELECT length(data) FROM '%q'.'%q_node' WHERE nodeno = 1",
-        pRtree->zDb, pRtree->zName
-    );
-    rc = getIntFromStmt(db, zSql, &pRtree->iNodeSize);
-    if( rc!=SQLITE_OK ){
-      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+static void rbuSetupCheckpoint(sqlite3rbu *p, RbuState *pState){
+
+  /* If pState is NULL, then the wal file may not have been opened and
+  ** recovered. Running a read-statement here to ensure that doing so
+  ** does not interfere with the "capture" process below.  */
+  if( pState==0 ){
+    p->eStage = 0;
+    if( p->rc==SQLITE_OK ){
+      p->rc = sqlite3_exec(p->dbMain, "SELECT * FROM sqlite_master", 0, 0, 0);
     }
   }
 
-  sqlite3_free(zSql);
-  return rc;
+  /* Assuming no error has occurred, run a "restart" checkpoint with the
+  ** sqlite3rbu.eStage variable set to CAPTURE. This turns on the following
+  ** special behaviour in the rbu VFS:
+  **
+  **   * If the exclusive shm WRITER or READ0 lock cannot be obtained,
+  **     the checkpoint fails with SQLITE_BUSY (normally SQLite would
+  **     proceed with running a passive checkpoint instead of failing).
+  **
+  **   * Attempts to read from the *-wal file or write to the database file
+  **     do not perform any IO. Instead, the frame/page combinations that
+  **     would be read/written are recorded in the sqlite3rbu.aFrame[]
+  **     array.
+  **
+  **   * Calls to xShmLock(UNLOCK) to release the exclusive shm WRITER, 
+  **     READ0 and CHECKPOINT locks taken as part of the checkpoint are
+  **     no-ops. These locks will not be released until the connection
+  **     is closed.
+  **
+  **   * Attempting to xSync() the database file causes an SQLITE_INTERNAL 
+  **     error.
+  **
+  ** As a result, unless an error (i.e. OOM or SQLITE_BUSY) occurs, the
+  ** checkpoint below fails with SQLITE_INTERNAL, and leaves the aFrame[]
+  ** array populated with a set of (frame -> page) mappings. Because the 
+  ** WRITER, CHECKPOINT and READ0 locks are still held, it is safe to copy 
+  ** data from the wal file into the database file according to the 
+  ** contents of aFrame[].
+  */
+  if( p->rc==SQLITE_OK ){
+    int rc2;
+    p->eStage = RBU_STAGE_CAPTURE;
+    rc2 = sqlite3_exec(p->dbMain, "PRAGMA main.wal_checkpoint=restart", 0, 0,0);
+    if( rc2!=SQLITE_INTERNAL ) p->rc = rc2;
+  }
+
+  if( p->rc==SQLITE_OK ){
+    p->eStage = RBU_STAGE_CKPT;
+    p->nStep = (pState ? pState->nRow : 0);
+    p->aBuf = rbuMalloc(p, p->pgsz);
+    p->iWalCksum = rbuShmChecksum(p);
+  }
+
+  if( p->rc==SQLITE_OK && pState && pState->iWalCksum!=p->iWalCksum ){
+    p->rc = SQLITE_DONE;
+    p->eStage = RBU_STAGE_DONE;
+  }
 }
 
-/* 
-** This function is the implementation of both the xConnect and xCreate
-** methods of the r-tree virtual table.
-**
-**   argv[0]   -> module name
-**   argv[1]   -> database name
-**   argv[2]   -> table name
-**   argv[...] -> column names...
+/*
+** Called when iAmt bytes are read from offset iOff of the wal file while
+** the rbu object is in capture mode. Record the frame number of the frame
+** being read in the aFrame[] array.
 */
-static int rtreeInit(
-  sqlite3 *db,                        /* Database connection */
-  void *pAux,                         /* One of the RTREE_COORD_* constants */
-  int argc, const char *const*argv,   /* Parameters to CREATE TABLE statement */
-  sqlite3_vtab **ppVtab,              /* OUT: New virtual table */
-  char **pzErr,                       /* OUT: Error message, if any */
-  int isCreate                        /* True for xCreate, false for xConnect */
-){
-  int rc = SQLITE_OK;
-  Rtree *pRtree;
-  int nDb;              /* Length of string argv[1] */
-  int nName;            /* Length of string argv[2] */
-  int eCoordType = (pAux ? RTREE_COORD_INT32 : RTREE_COORD_REAL32);
+static int rbuCaptureWalRead(sqlite3rbu *pRbu, i64 iOff, int iAmt){
+  const u32 mReq = (1<<WAL_LOCK_WRITE)|(1<<WAL_LOCK_CKPT)|(1<<WAL_LOCK_READ0);
+  u32 iFrame;
 
-  const char *aErrMsg[] = {
-    0,                                                    /* 0 */
-    "Wrong number of columns for an rtree table",         /* 1 */
-    "Too few columns for an rtree table",                 /* 2 */
-    "Too many columns for an rtree table"                 /* 3 */
-  };
+  if( pRbu->mLock!=mReq ){
+    pRbu->rc = SQLITE_BUSY;
+    return SQLITE_INTERNAL;
+  }
 
-  int iErr = (argc<6) ? 2 : argc>(RTREE_MAX_DIMENSIONS*2+4) ? 3 : argc%2;
-  if( aErrMsg[iErr] ){
-    *pzErr = sqlite3_mprintf("%s", aErrMsg[iErr]);
-    return SQLITE_ERROR;
+  pRbu->pgsz = iAmt;
+  if( pRbu->nFrame==pRbu->nFrameAlloc ){
+    int nNew = (pRbu->nFrameAlloc ? pRbu->nFrameAlloc : 64) * 2;
+    RbuFrame *aNew;
+    aNew = (RbuFrame*)sqlite3_realloc(pRbu->aFrame, nNew * sizeof(RbuFrame));
+    if( aNew==0 ) return SQLITE_NOMEM;
+    pRbu->aFrame = aNew;
+    pRbu->nFrameAlloc = nNew;
   }
 
-  sqlite3_vtab_config(db, SQLITE_VTAB_CONSTRAINT_SUPPORT, 1);
+  iFrame = (u32)((iOff-32) / (i64)(iAmt+24)) + 1;
+  if( pRbu->iMaxFrame<iFrame ) pRbu->iMaxFrame = iFrame;
+  pRbu->aFrame[pRbu->nFrame].iWalFrame = iFrame;
+  pRbu->aFrame[pRbu->nFrame].iDbPage = 0;
+  pRbu->nFrame++;
+  return SQLITE_OK;
+}
 
-  /* Allocate the sqlite3_vtab structure */
-  nDb = (int)strlen(argv[1]);
-  nName = (int)strlen(argv[2]);
-  pRtree = (Rtree *)sqlite3_malloc(sizeof(Rtree)+nDb+nName+2);
-  if( !pRtree ){
-    return SQLITE_NOMEM;
+/*
+** Called when a page of data is written to offset iOff of the database
+** file while the rbu handle is in capture mode. Record the page number 
+** of the page being written in the aFrame[] array.
+*/
+static int rbuCaptureDbWrite(sqlite3rbu *pRbu, i64 iOff){
+  pRbu->aFrame[pRbu->nFrame-1].iDbPage = (u32)(iOff / pRbu->pgsz) + 1;
+  return SQLITE_OK;
+}
+
+/*
+** This is called as part of an incremental checkpoint operation. Copy
+** a single frame of data from the wal file into the database file, as
+** indicated by the RbuFrame object.
+*/
+static void rbuCheckpointFrame(sqlite3rbu *p, RbuFrame *pFrame){
+  sqlite3_file *pWal = p->pTargetFd->pWalFd->pReal;
+  sqlite3_file *pDb = p->pTargetFd->pReal;
+  i64 iOff;
+
+  assert( p->rc==SQLITE_OK );
+  iOff = (i64)(pFrame->iWalFrame-1) * (p->pgsz + 24) + 32 + 24;
+  p->rc = pWal->pMethods->xRead(pWal, p->aBuf, p->pgsz, iOff);
+  if( p->rc ) return;
+
+  iOff = (i64)(pFrame->iDbPage-1) * p->pgsz;
+  p->rc = pDb->pMethods->xWrite(pDb, p->aBuf, p->pgsz, iOff);
+}
+
+
+/*
+** Take an EXCLUSIVE lock on the database file.
+*/
+static void rbuLockDatabase(sqlite3rbu *p){
+  sqlite3_file *pReal = p->pTargetFd->pReal;
+  assert( p->rc==SQLITE_OK );
+  p->rc = pReal->pMethods->xLock(pReal, SQLITE_LOCK_SHARED);
+  if( p->rc==SQLITE_OK ){
+    p->rc = pReal->pMethods->xLock(pReal, SQLITE_LOCK_EXCLUSIVE);
   }
-  memset(pRtree, 0, sizeof(Rtree)+nDb+nName+2);
-  pRtree->nBusy = 1;
-  pRtree->base.pModule = &rtreeModule;
-  pRtree->zDb = (char *)&pRtree[1];
-  pRtree->zName = &pRtree->zDb[nDb+1];
-  pRtree->nDim = (argc-4)/2;
-  pRtree->nBytesPerCell = 8 + pRtree->nDim*4*2;
-  pRtree->eCoordType = eCoordType;
-  memcpy(pRtree->zDb, argv[1], nDb);
-  memcpy(pRtree->zName, argv[2], nName);
+}
 
-  /* Figure out the node size to use. */
-  rc = getNodeSize(db, pRtree, isCreate, pzErr);
+/*
+** The RBU handle is currently in RBU_STAGE_OAL state, with a SHARED lock
+** on the database file. This proc moves the *-oal file to the *-wal path,
+** then reopens the database file (this time in vanilla, non-oal, WAL mode).
+** If an error occurs, leave an error code and error message in the rbu 
+** handle.
+*/
+static void rbuMoveOalFile(sqlite3rbu *p){
+  const char *zBase = sqlite3_db_filename(p->dbMain, "main");
 
-  /* Create/Connect to the underlying relational database schema. If
-  ** that is successful, call sqlite3_declare_vtab() to configure
-  ** the r-tree table schema.
-  */
-  if( rc==SQLITE_OK ){
-    if( (rc = rtreeSqlInit(pRtree, db, argv[1], argv[2], isCreate)) ){
-      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
-    }else{
-      char *zSql = sqlite3_mprintf("CREATE TABLE x(%s", argv[3]);
-      char *zTmp;
-      int ii;
-      for(ii=4; zSql && ii<argc; ii++){
-        zTmp = zSql;
-        zSql = sqlite3_mprintf("%s, %s", zTmp, argv[ii]);
-        sqlite3_free(zTmp);
-      }
-      if( zSql ){
-        zTmp = zSql;
-        zSql = sqlite3_mprintf("%s);", zTmp);
-        sqlite3_free(zTmp);
-      }
-      if( !zSql ){
-        rc = SQLITE_NOMEM;
-      }else if( SQLITE_OK!=(rc = sqlite3_declare_vtab(db, zSql)) ){
-        *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+  char *zWal = sqlite3_mprintf("%s-wal", zBase);
+  char *zOal = sqlite3_mprintf("%s-oal", zBase);
+
+  assert( p->eStage==RBU_STAGE_MOVE );
+  assert( p->rc==SQLITE_OK && p->zErrmsg==0 );
+  if( zWal==0 || zOal==0 ){
+    p->rc = SQLITE_NOMEM;
+  }else{
+    /* Move the *-oal file to *-wal. At this point connection p->db is
+    ** holding a SHARED lock on the target database file (because it is
+    ** in WAL mode). So no other connection may be writing the db. 
+    **
+    ** In order to ensure that there are no database readers, an EXCLUSIVE
+    ** lock is obtained here before the *-oal is moved to *-wal.
+    */
+    rbuLockDatabase(p);
+    if( p->rc==SQLITE_OK ){
+      rbuFileSuffix3(zBase, zWal);
+      rbuFileSuffix3(zBase, zOal);
+
+      /* Re-open the databases. */
+      rbuObjIterFinalize(&p->objiter);
+      sqlite3_close(p->dbMain);
+      sqlite3_close(p->dbRbu);
+      p->rc = rename(zOal, zWal) ? SQLITE_IOERR : SQLITE_OK;
+      if( p->rc==SQLITE_OK ){
+        p->dbMain = 0;
+        p->dbRbu = 0;
+        rbuOpenDatabase(p);
+        rbuSetupCheckpoint(p, 0);
       }
-      sqlite3_free(zSql);
     }
   }
 
-  if( rc==SQLITE_OK ){
-    *ppVtab = (sqlite3_vtab *)pRtree;
-  }else{
-    assert( *ppVtab==0 );
-    assert( pRtree->nBusy==1 );
-    rtreeRelease(pRtree);
-  }
-  return rc;
+  sqlite3_free(zWal);
+  sqlite3_free(zOal);
 }
 
-
 /*
-** Implementation of a scalar function that decodes r-tree nodes to
-** human readable strings. This can be used for debugging and analysis.
+** The SELECT statement iterating through the keys for the current object
+** (p->objiter.pSelect) currently points to a valid row. This function
+** determines the type of operation requested by this row and returns
+** one of the following values to indicate the result:
 **
-** The scalar function takes two arguments: (1) the number of dimensions
-** to the rtree (between 1 and 5, inclusive) and (2) a blob of data containing
-** an r-tree node.  For a two-dimensional r-tree structure called "rt", to
-** deserialize all nodes, a statement like:
+**     * RBU_INSERT
+**     * RBU_DELETE
+**     * RBU_IDX_DELETE
+**     * RBU_UPDATE
 **
-**   SELECT rtreenode(2, data) FROM rt_node;
+** If RBU_UPDATE is returned, then output variable *pzMask is set to
+** point to the text value indicating the columns to update.
 **
-** The human readable string takes the form of a Tcl list with one
-** entry for each cell in the r-tree node. Each entry is itself a
-** list, containing the 8-byte rowid/pageno followed by the 
-** <num-dimension>*2 coordinates.
+** If the rbu_control field contains an invalid value, an error code and
+** message are left in the RBU handle and zero returned.
 */
-static void rtreenode(sqlite3_context *ctx, int nArg, sqlite3_value **apArg){
-  char *zText = 0;
-  RtreeNode node;
-  Rtree tree;
-  int ii;
+static int rbuStepType(sqlite3rbu *p, const char **pzMask){
+  int iCol = p->objiter.nCol;     /* Index of rbu_control column */
+  int res = 0;                    /* Return value */
 
-  UNUSED_PARAMETER(nArg);
-  memset(&node, 0, sizeof(RtreeNode));
-  memset(&tree, 0, sizeof(Rtree));
-  tree.nDim = sqlite3_value_int(apArg[0]);
-  tree.nBytesPerCell = 8 + 8 * tree.nDim;
-  node.zData = (u8 *)sqlite3_value_blob(apArg[1]);
+  switch( sqlite3_column_type(p->objiter.pSelect, iCol) ){
+    case SQLITE_INTEGER: {
+      int iVal = sqlite3_column_int(p->objiter.pSelect, iCol);
+      if( iVal==0 ){
+        res = RBU_INSERT;
+      }else if( iVal==1 ){
+        res = RBU_DELETE;
+      }else if( iVal==2 ){
+        res = RBU_IDX_DELETE;
+      }else if( iVal==3 ){
+        res = RBU_IDX_INSERT;
+      }
+      break;
+    }
 
-  for(ii=0; ii<NCELL(&node); ii++){
-    char zCell[512];
-    int nCell = 0;
-    RtreeCell cell;
-    int jj;
+    case SQLITE_TEXT: {
+      const unsigned char *z = sqlite3_column_text(p->objiter.pSelect, iCol);
+      if( z==0 ){
+        p->rc = SQLITE_NOMEM;
+      }else{
+        *pzMask = (const char*)z;
+      }
+      res = RBU_UPDATE;
 
-    nodeGetCell(&tree, &node, ii, &cell);
-    sqlite3_snprintf(512-nCell,&zCell[nCell],"%lld", cell.iRowid);
-    nCell = (int)strlen(zCell);
-    for(jj=0; jj<tree.nDim*2; jj++){
-#ifndef SQLITE_RTREE_INT_ONLY
-      sqlite3_snprintf(512-nCell,&zCell[nCell], " %g",
-                       (double)cell.aCoord[jj].f);
-#else
-      sqlite3_snprintf(512-nCell,&zCell[nCell], " %d",
-                       cell.aCoord[jj].i);
-#endif
-      nCell = (int)strlen(zCell);
+      break;
     }
 
-    if( zText ){
-      char *zTextNew = sqlite3_mprintf("%s {%s}", zText, zCell);
-      sqlite3_free(zText);
-      zText = zTextNew;
-    }else{
-      zText = sqlite3_mprintf("{%s}", zCell);
-    }
+    default:
+      break;
   }
-  
-  sqlite3_result_text(ctx, zText, -1, sqlite3_free);
+
+  if( res==0 ){
+    rbuBadControlError(p);
+  }
+  return res;
 }
 
-/* This routine implements an SQL function that returns the "depth" parameter
-** from the front of a blob that is an r-tree node.  For example:
+#ifdef SQLITE_DEBUG
+/*
+** Assert that column iCol of statement pStmt is named zName.
+*/
+static void assertColumnName(sqlite3_stmt *pStmt, int iCol, const char *zName){
+  const char *zCol = sqlite3_column_name(pStmt, iCol);
+  assert( 0==sqlite3_stricmp(zName, zCol) );
+}
+#else
+# define assertColumnName(x,y,z)
+#endif
+
+/*
+** This function does the work for an sqlite3rbu_step() call.
 **
-**     SELECT rtreedepth(data) FROM rt_node WHERE nodeno=1;
+** The object-iterator (p->objiter) currently points to a valid object,
+** and the input cursor (p->objiter.pSelect) currently points to a valid
+** input row. Perform whatever processing is required and return.
 **
-** The depth value is 0 for all nodes other than the root node, and the root
-** node always has nodeno=1, so the example above is the primary use for this
-** routine.  This routine is intended for testing and analysis only.
+** If no  error occurs, SQLITE_OK is returned. Otherwise, an error code
+** and message is left in the RBU handle and a copy of the error code
+** returned.
 */
-static void rtreedepth(sqlite3_context *ctx, int nArg, sqlite3_value **apArg){
-  UNUSED_PARAMETER(nArg);
-  if( sqlite3_value_type(apArg[0])!=SQLITE_BLOB 
-   || sqlite3_value_bytes(apArg[0])<2
-  ){
-    sqlite3_result_error(ctx, "Invalid argument to rtreedepth()", -1); 
-  }else{
-    u8 *zBlob = (u8 *)sqlite3_value_blob(apArg[0]);
-    sqlite3_result_int(ctx, readInt16(zBlob));
+static int rbuStep(sqlite3rbu *p){
+  RbuObjIter *pIter = &p->objiter;
+  const char *zMask = 0;
+  int i;
+  int eType = rbuStepType(p, &zMask);
+
+  if( eType ){
+    assert( eType!=RBU_UPDATE || pIter->zIdx==0 );
+
+    if( pIter->zIdx==0 && eType==RBU_IDX_DELETE ){
+      rbuBadControlError(p);
+    }
+    else if( 
+        eType==RBU_INSERT 
+     || eType==RBU_DELETE
+     || eType==RBU_IDX_DELETE 
+     || eType==RBU_IDX_INSERT
+    ){
+      sqlite3_value *pVal;
+      sqlite3_stmt *pWriter;
+
+      assert( eType!=RBU_UPDATE );
+      assert( eType!=RBU_DELETE || pIter->zIdx==0 );
+
+      if( eType==RBU_IDX_DELETE || eType==RBU_DELETE ){
+        pWriter = pIter->pDelete;
+      }else{
+        pWriter = pIter->pInsert;
+      }
+
+      for(i=0; i<pIter->nCol; i++){
+        /* If this is an INSERT into a table b-tree and the table has an
+        ** explicit INTEGER PRIMARY KEY, check that this is not an attempt
+        ** to write a NULL into the IPK column. That is not permitted.  */
+        if( eType==RBU_INSERT 
+         && pIter->zIdx==0 && pIter->eType==RBU_PK_IPK && pIter->abTblPk[i] 
+         && sqlite3_column_type(pIter->pSelect, i)==SQLITE_NULL
+        ){
+          p->rc = SQLITE_MISMATCH;
+          p->zErrmsg = sqlite3_mprintf("datatype mismatch");
+          goto step_out;
+        }
+
+        if( eType==RBU_DELETE && pIter->abTblPk[i]==0 ){
+          continue;
+        }
+
+        pVal = sqlite3_column_value(pIter->pSelect, i);
+        p->rc = sqlite3_bind_value(pWriter, i+1, pVal);
+        if( p->rc ) goto step_out;
+      }
+      if( pIter->zIdx==0
+       && (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE) 
+      ){
+        /* For a virtual table, or a table with no primary key, the 
+        ** SELECT statement is:
+        **
+        **   SELECT <cols>, rbu_control, rbu_rowid FROM ....
+        **
+        ** Hence column_value(pIter->nCol+1).
+        */
+        assertColumnName(pIter->pSelect, pIter->nCol+1, "rbu_rowid");
+        pVal = sqlite3_column_value(pIter->pSelect, pIter->nCol+1);
+        p->rc = sqlite3_bind_value(pWriter, pIter->nCol+1, pVal);
+      }
+      if( p->rc==SQLITE_OK ){
+        sqlite3_step(pWriter);
+        p->rc = resetAndCollectError(pWriter, &p->zErrmsg);
+      }
+    }else{
+      sqlite3_value *pVal;
+      sqlite3_stmt *pUpdate = 0;
+      assert( eType==RBU_UPDATE );
+      rbuGetUpdateStmt(p, pIter, zMask, &pUpdate);
+      if( pUpdate ){
+        for(i=0; p->rc==SQLITE_OK && i<pIter->nCol; i++){
+          char c = zMask[pIter->aiSrcOrder[i]];
+          pVal = sqlite3_column_value(pIter->pSelect, i);
+          if( pIter->abTblPk[i] || c=='x' || c=='d' ){
+            p->rc = sqlite3_bind_value(pUpdate, i+1, pVal);
+          }
+        }
+        if( p->rc==SQLITE_OK 
+         && (pIter->eType==RBU_PK_VTAB || pIter->eType==RBU_PK_NONE) 
+        ){
+          /* Bind the rbu_rowid value to column _rowid_ */
+          assertColumnName(pIter->pSelect, pIter->nCol+1, "rbu_rowid");
+          pVal = sqlite3_column_value(pIter->pSelect, pIter->nCol+1);
+          p->rc = sqlite3_bind_value(pUpdate, pIter->nCol+1, pVal);
+        }
+        if( p->rc==SQLITE_OK ){
+          sqlite3_step(pUpdate);
+          p->rc = resetAndCollectError(pUpdate, &p->zErrmsg);
+        }
+      }
+    }
   }
+
+ step_out:
+  return p->rc;
 }
 
 /*
-** Register the r-tree module with database handle db. This creates the
-** virtual table module "rtree" and the debugging/analysis scalar 
-** function "rtreenode".
+** Increment the schema cookie of the main database opened by p->dbMain.
 */
-SQLITE_PRIVATE int sqlite3RtreeInit(sqlite3 *db){
-  const int utf8 = SQLITE_UTF8;
-  int rc;
+static void rbuIncrSchemaCookie(sqlite3rbu *p){
+  if( p->rc==SQLITE_OK ){
+    int iCookie = 1000000;
+    sqlite3_stmt *pStmt;
 
-  rc = sqlite3_create_function(db, "rtreenode", 2, utf8, 0, rtreenode, 0, 0);
-  if( rc==SQLITE_OK ){
-    rc = sqlite3_create_function(db, "rtreedepth", 1, utf8, 0,rtreedepth, 0, 0);
-  }
-  if( rc==SQLITE_OK ){
-#ifdef SQLITE_RTREE_INT_ONLY
-    void *c = (void *)RTREE_COORD_INT32;
-#else
-    void *c = (void *)RTREE_COORD_REAL32;
-#endif
-    rc = sqlite3_create_module_v2(db, "rtree", &rtreeModule, c, 0);
-  }
-  if( rc==SQLITE_OK ){
-    void *c = (void *)RTREE_COORD_INT32;
-    rc = sqlite3_create_module_v2(db, "rtree_i32", &rtreeModule, c, 0);
+    p->rc = prepareAndCollectError(p->dbMain, &pStmt, &p->zErrmsg, 
+        "PRAGMA schema_version"
+    );
+    if( p->rc==SQLITE_OK ){
+      /* Coverage: it may be that this sqlite3_step() cannot fail. There
+      ** is already a transaction open, so the prepared statement cannot
+      ** throw an SQLITE_SCHEMA exception. The only database page the
+      ** statement reads is page 1, which is guaranteed to be in the cache.
+      ** And no memory allocations are required.  */
+      if( SQLITE_ROW==sqlite3_step(pStmt) ){
+        iCookie = sqlite3_column_int(pStmt, 0);
+      }
+      rbuFinalize(p, pStmt);
+    }
+    if( p->rc==SQLITE_OK ){
+      rbuMPrintfExec(p, p->dbMain, "PRAGMA schema_version = %d", iCookie+1);
+    }
   }
-
-  return rc;
 }
 
 /*
-** This routine deletes the RtreeGeomCallback object that was attached
-** one of the SQL functions create by sqlite3_rtree_geometry_callback()
-** or sqlite3_rtree_query_callback().  In other words, this routine is the
-** destructor for an RtreeGeomCallback objecct.  This routine is called when
-** the corresponding SQL function is deleted.
+** Update the contents of the rbu_state table within the rbu database. The
+** value stored in the RBU_STATE_STAGE column is eStage. All other values
+** are determined by inspecting the rbu handle passed as the first argument.
 */
-static void rtreeFreeCallback(void *p){
-  RtreeGeomCallback *pInfo = (RtreeGeomCallback*)p;
-  if( pInfo->xDestructor ) pInfo->xDestructor(pInfo->pContext);
-  sqlite3_free(p);
+static void rbuSaveState(sqlite3rbu *p, int eStage){
+  if( p->rc==SQLITE_OK || p->rc==SQLITE_DONE ){
+    sqlite3_stmt *pInsert = 0;
+    int rc;
+
+    assert( p->zErrmsg==0 );
+    rc = prepareFreeAndCollectError(p->dbRbu, &pInsert, &p->zErrmsg, 
+        sqlite3_mprintf(
+          "INSERT OR REPLACE INTO %s.rbu_state(k, v) VALUES "
+          "(%d, %d), "
+          "(%d, %Q), "
+          "(%d, %Q), "
+          "(%d, %d), "
+          "(%d, %d), "
+          "(%d, %lld), "
+          "(%d, %lld), "
+          "(%d, %lld) ",
+          p->zStateDb,
+          RBU_STATE_STAGE, eStage,
+          RBU_STATE_TBL, p->objiter.zTbl, 
+          RBU_STATE_IDX, p->objiter.zIdx, 
+          RBU_STATE_ROW, p->nStep, 
+          RBU_STATE_PROGRESS, p->nProgress,
+          RBU_STATE_CKPT, p->iWalCksum,
+          RBU_STATE_COOKIE, (i64)p->pTargetFd->iCookie,
+          RBU_STATE_OALSZ, p->iOalSz
+      )
+    );
+    assert( pInsert==0 || rc==SQLITE_OK );
+
+    if( rc==SQLITE_OK ){
+      sqlite3_step(pInsert);
+      rc = sqlite3_finalize(pInsert);
+    }
+    if( rc!=SQLITE_OK ) p->rc = rc;
+  }
 }
 
+
 /*
-** Each call to sqlite3_rtree_geometry_callback() or
-** sqlite3_rtree_query_callback() creates an ordinary SQLite
-** scalar function that is implemented by this routine.
-**
-** All this function does is construct an RtreeMatchArg object that
-** contains the geometry-checking callback routines and a list of
-** parameters to this function, then return that RtreeMatchArg object
-** as a BLOB.
-**
-** The R-Tree MATCH operator will read the returned BLOB, deserialize
-** the RtreeMatchArg object, and use the RtreeMatchArg object to figure
-** out which elements of the R-Tree should be returned by the query.
+** Step the RBU object.
 */
-static void geomCallback(sqlite3_context *ctx, int nArg, sqlite3_value **aArg){
-  RtreeGeomCallback *pGeomCtx = (RtreeGeomCallback *)sqlite3_user_data(ctx);
-  RtreeMatchArg *pBlob;
-  int nBlob;
+SQLITE_API int SQLITE_STDCALL sqlite3rbu_step(sqlite3rbu *p){
+  if( p ){
+    switch( p->eStage ){
+      case RBU_STAGE_OAL: {
+        RbuObjIter *pIter = &p->objiter;
+        while( p->rc==SQLITE_OK && pIter->zTbl ){
+
+          if( pIter->bCleanup ){
+            /* Clean up the rbu_tmp_xxx table for the previous table. It 
+            ** cannot be dropped as there are currently active SQL statements.
+            ** But the contents can be deleted.  */
+            if( pIter->abIndexed ){
+              rbuMPrintfExec(p, p->dbRbu, 
+                  "DELETE FROM %s.'rbu_tmp_%q'", p->zStateDb, pIter->zTbl
+              );
+            }
+          }else{
+            rbuObjIterPrepareAll(p, pIter, 0);
+
+            /* Advance to the next row to process. */
+            if( p->rc==SQLITE_OK ){
+              int rc = sqlite3_step(pIter->pSelect);
+              if( rc==SQLITE_ROW ){
+                p->nProgress++;
+                p->nStep++;
+                return rbuStep(p);
+              }
+              p->rc = sqlite3_reset(pIter->pSelect);
+              p->nStep = 0;
+            }
+          }
 
-  nBlob = sizeof(RtreeMatchArg) + (nArg-1)*sizeof(RtreeDValue);
-  pBlob = (RtreeMatchArg *)sqlite3_malloc(nBlob);
-  if( !pBlob ){
-    sqlite3_result_error_nomem(ctx);
-  }else{
-    int i;
-    pBlob->magic = RTREE_GEOMETRY_MAGIC;
-    pBlob->cb = pGeomCtx[0];
-    pBlob->nParam = nArg;
-    for(i=0; i<nArg; i++){
-#ifdef SQLITE_RTREE_INT_ONLY
-      pBlob->aParam[i] = sqlite3_value_int64(aArg[i]);
-#else
-      pBlob->aParam[i] = sqlite3_value_double(aArg[i]);
-#endif
+          rbuObjIterNext(p, pIter);
+        }
+
+        if( p->rc==SQLITE_OK ){
+          assert( pIter->zTbl==0 );
+          rbuSaveState(p, RBU_STAGE_MOVE);
+          rbuIncrSchemaCookie(p);
+          if( p->rc==SQLITE_OK ){
+            p->rc = sqlite3_exec(p->dbMain, "COMMIT", 0, 0, &p->zErrmsg);
+          }
+          if( p->rc==SQLITE_OK ){
+            p->rc = sqlite3_exec(p->dbRbu, "COMMIT", 0, 0, &p->zErrmsg);
+          }
+          p->eStage = RBU_STAGE_MOVE;
+        }
+        break;
+      }
+
+      case RBU_STAGE_MOVE: {
+        if( p->rc==SQLITE_OK ){
+          rbuMoveOalFile(p);
+          p->nProgress++;
+        }
+        break;
+      }
+
+      case RBU_STAGE_CKPT: {
+        if( p->rc==SQLITE_OK ){
+          if( p->nStep>=p->nFrame ){
+            sqlite3_file *pDb = p->pTargetFd->pReal;
+  
+            /* Sync the db file */
+            p->rc = pDb->pMethods->xSync(pDb, SQLITE_SYNC_NORMAL);
+  
+            /* Update nBackfill */
+            if( p->rc==SQLITE_OK ){
+              void volatile *ptr;
+              p->rc = pDb->pMethods->xShmMap(pDb, 0, 32*1024, 0, &ptr);
+              if( p->rc==SQLITE_OK ){
+                ((u32 volatile*)ptr)[24] = p->iMaxFrame;
+              }
+            }
+  
+            if( p->rc==SQLITE_OK ){
+              p->eStage = RBU_STAGE_DONE;
+              p->rc = SQLITE_DONE;
+            }
+          }else{
+            RbuFrame *pFrame = &p->aFrame[p->nStep];
+            rbuCheckpointFrame(p, pFrame);
+            p->nStep++;
+          }
+          p->nProgress++;
+        }
+        break;
+      }
+
+      default:
+        break;
     }
-    sqlite3_result_blob(ctx, pBlob, nBlob, sqlite3_free);
+    return p->rc;
+  }else{
+    return SQLITE_NOMEM;
   }
 }
 
 /*
-** Register a new geometry function for use with the r-tree MATCH operator.
+** Free an RbuState object allocated by rbuLoadState().
 */
-SQLITE_API int SQLITE_STDCALL sqlite3_rtree_geometry_callback(
-  sqlite3 *db,                  /* Register SQL function on this connection */
-  const char *zGeom,            /* Name of the new SQL function */
-  int (*xGeom)(sqlite3_rtree_geometry*,int,RtreeDValue*,int*), /* Callback */
-  void *pContext                /* Extra data associated with the callback */
-){
-  RtreeGeomCallback *pGeomCtx;      /* Context object for new user-function */
-
-  /* Allocate and populate the context object. */
-  pGeomCtx = (RtreeGeomCallback *)sqlite3_malloc(sizeof(RtreeGeomCallback));
-  if( !pGeomCtx ) return SQLITE_NOMEM;
-  pGeomCtx->xGeom = xGeom;
-  pGeomCtx->xQueryFunc = 0;
-  pGeomCtx->xDestructor = 0;
-  pGeomCtx->pContext = pContext;
-  return sqlite3_create_function_v2(db, zGeom, -1, SQLITE_ANY, 
-      (void *)pGeomCtx, geomCallback, 0, 0, rtreeFreeCallback
-  );
+static void rbuFreeState(RbuState *p){
+  if( p ){
+    sqlite3_free(p->zTbl);
+    sqlite3_free(p->zIdx);
+    sqlite3_free(p);
+  }
 }
 
 /*
-** Register a new 2nd-generation geometry function for use with the
-** r-tree MATCH operator.
+** Allocate an RbuState object and load the contents of the rbu_state 
+** table into it. Return a pointer to the new object. It is the 
+** responsibility of the caller to eventually free the object using
+** sqlite3_free().
+**
+** If an error occurs, leave an error code and message in the rbu handle
+** and return NULL.
 */
-SQLITE_API int SQLITE_STDCALL sqlite3_rtree_query_callback(
-  sqlite3 *db,                 /* Register SQL function on this connection */
-  const char *zQueryFunc,      /* Name of new SQL function */
-  int (*xQueryFunc)(sqlite3_rtree_query_info*), /* Callback */
-  void *pContext,              /* Extra data passed into the callback */
-  void (*xDestructor)(void*)   /* Destructor for the extra data */
-){
-  RtreeGeomCallback *pGeomCtx;      /* Context object for new user-function */
+static RbuState *rbuLoadState(sqlite3rbu *p){
+  RbuState *pRet = 0;
+  sqlite3_stmt *pStmt = 0;
+  int rc;
+  int rc2;
 
-  /* Allocate and populate the context object. */
-  pGeomCtx = (RtreeGeomCallback *)sqlite3_malloc(sizeof(RtreeGeomCallback));
-  if( !pGeomCtx ) return SQLITE_NOMEM;
-  pGeomCtx->xGeom = 0;
-  pGeomCtx->xQueryFunc = xQueryFunc;
-  pGeomCtx->xDestructor = xDestructor;
-  pGeomCtx->pContext = pContext;
-  return sqlite3_create_function_v2(db, zQueryFunc, -1, SQLITE_ANY, 
-      (void *)pGeomCtx, geomCallback, 0, 0, rtreeFreeCallback
+  pRet = (RbuState*)rbuMalloc(p, sizeof(RbuState));
+  if( pRet==0 ) return 0;
+
+  rc = prepareFreeAndCollectError(p->dbRbu, &pStmt, &p->zErrmsg, 
+      sqlite3_mprintf("SELECT k, v FROM %s.rbu_state", p->zStateDb)
   );
-}
+  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+    switch( sqlite3_column_int(pStmt, 0) ){
+      case RBU_STATE_STAGE:
+        pRet->eStage = sqlite3_column_int(pStmt, 1);
+        if( pRet->eStage!=RBU_STAGE_OAL
+         && pRet->eStage!=RBU_STAGE_MOVE
+         && pRet->eStage!=RBU_STAGE_CKPT
+        ){
+          p->rc = SQLITE_CORRUPT;
+        }
+        break;
 
-#if !SQLITE_CORE
-#ifdef _WIN32
-__declspec(dllexport)
-#endif
-SQLITE_API int SQLITE_STDCALL sqlite3_rtree_init(
-  sqlite3 *db,
-  char **pzErrMsg,
-  const sqlite3_api_routines *pApi
-){
-  SQLITE_EXTENSION_INIT2(pApi)
-  return sqlite3RtreeInit(db);
+      case RBU_STATE_TBL:
+        pRet->zTbl = rbuStrndup((char*)sqlite3_column_text(pStmt, 1), &rc);
+        break;
+
+      case RBU_STATE_IDX:
+        pRet->zIdx = rbuStrndup((char*)sqlite3_column_text(pStmt, 1), &rc);
+        break;
+
+      case RBU_STATE_ROW:
+        pRet->nRow = sqlite3_column_int(pStmt, 1);
+        break;
+
+      case RBU_STATE_PROGRESS:
+        pRet->nProgress = sqlite3_column_int64(pStmt, 1);
+        break;
+
+      case RBU_STATE_CKPT:
+        pRet->iWalCksum = sqlite3_column_int64(pStmt, 1);
+        break;
+
+      case RBU_STATE_COOKIE:
+        pRet->iCookie = (u32)sqlite3_column_int64(pStmt, 1);
+        break;
+
+      case RBU_STATE_OALSZ:
+        pRet->iOalSz = (u32)sqlite3_column_int64(pStmt, 1);
+        break;
+
+      default:
+        rc = SQLITE_CORRUPT;
+        break;
+    }
+  }
+  rc2 = sqlite3_finalize(pStmt);
+  if( rc==SQLITE_OK ) rc = rc2;
+
+  p->rc = rc;
+  return pRet;
 }
-#endif
 
-#endif
+/*
+** Compare strings z1 and z2, returning 0 if they are identical, or non-zero
+** otherwise. Either or both argument may be NULL. Two NULL values are
+** considered equal, and NULL is considered distinct from all other values.
+*/
+static int rbuStrCompare(const char *z1, const char *z2){
+  if( z1==0 && z2==0 ) return 0;
+  if( z1==0 || z2==0 ) return 1;
+  return (sqlite3_stricmp(z1, z2)!=0);
+}
 
-/************** End of rtree.c ***********************************************/
-/************** Begin file icu.c *********************************************/
 /*
-** 2007 May 6
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** $Id: icu.c,v 1.7 2007/12/13 21:54:11 drh Exp $
-**
-** This file implements an integration between the ICU library 
-** ("International Components for Unicode", an open-source library 
-** for handling unicode data) and SQLite. The integration uses 
-** ICU to provide the following to SQLite:
+** This function is called as part of sqlite3rbu_open() when initializing
+** an rbu handle in OAL stage. If the rbu update has not started (i.e.
+** the rbu_state table was empty) it is a no-op. Otherwise, it arranges
+** things so that the next call to sqlite3rbu_step() continues on from
+** where the previous rbu handle left off.
 **
-**   * An implementation of the SQL regexp() function (and hence REGEXP
-**     operator) using the ICU uregex_XX() APIs.
-**
-**   * Implementations of the SQL scalar upper() and lower() functions
-**     for case mapping.
-**
-**   * Integration of ICU and SQLite collation sequences.
-**
-**   * An implementation of the LIKE operator that uses ICU to 
-**     provide case-independent matching.
+** If an error occurs, an error code and error message are left in the
+** rbu handle passed as the first argument.
 */
+static void rbuSetupOal(sqlite3rbu *p, RbuState *pState){
+  assert( p->rc==SQLITE_OK );
+  if( pState->zTbl ){
+    RbuObjIter *pIter = &p->objiter;
+    int rc = SQLITE_OK;
 
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_ICU)
+    while( rc==SQLITE_OK && pIter->zTbl && (pIter->bCleanup 
+       || rbuStrCompare(pIter->zIdx, pState->zIdx)
+       || rbuStrCompare(pIter->zTbl, pState->zTbl) 
+    )){
+      rc = rbuObjIterNext(p, pIter);
+    }
 
-/* Include ICU headers */
-#include <unicode/utypes.h>
-#include <unicode/uregex.h>
-#include <unicode/ustring.h>
-#include <unicode/ucol.h>
+    if( rc==SQLITE_OK && !pIter->zTbl ){
+      rc = SQLITE_ERROR;
+      p->zErrmsg = sqlite3_mprintf("rbu_state mismatch error");
+    }
 
-/* #include <assert.h> */
+    if( rc==SQLITE_OK ){
+      p->nStep = pState->nRow;
+      rc = rbuObjIterPrepareAll(p, &p->objiter, p->nStep);
+    }
 
-#ifndef SQLITE_CORE
-  SQLITE_EXTENSION_INIT1
-#else
-#endif
+    p->rc = rc;
+  }
+}
 
 /*
-** Maximum length (in bytes) of the pattern in a LIKE or GLOB
-** operator.
+** If there is a "*-oal" file in the file-system corresponding to the
+** target database in the file-system, delete it. If an error occurs,
+** leave an error code and error message in the rbu handle.
 */
-#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
-# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
-#endif
+static void rbuDeleteOalFile(sqlite3rbu *p){
+  char *zOal = sqlite3_mprintf("%s-oal", p->zTarget);
+  assert( p->rc==SQLITE_OK && p->zErrmsg==0 );
+  unlink(zOal);
+  sqlite3_free(zOal);
+}
 
 /*
-** Version of sqlite3_free() that is always a function, never a macro.
+** Allocate a private rbu VFS for the rbu handle passed as the only
+** argument. This VFS will be used unless the call to sqlite3rbu_open()
+** specified a URI with a vfs=? option in place of a target database
+** file name.
 */
-static void xFree(void *p){
-  sqlite3_free(p);
+static void rbuCreateVfs(sqlite3rbu *p){
+  int rnd;
+  char zRnd[64];
+
+  assert( p->rc==SQLITE_OK );
+  sqlite3_randomness(sizeof(int), (void*)&rnd);
+  sqlite3_snprintf(sizeof(zRnd), zRnd, "rbu_vfs_%d", rnd);
+  p->rc = sqlite3rbu_create_vfs(zRnd, 0);
+  if( p->rc==SQLITE_OK ){
+    sqlite3_vfs *pVfs = sqlite3_vfs_find(zRnd);
+    assert( pVfs );
+    p->zVfsName = pVfs->zName;
+  }
 }
 
 /*
-** Compare two UTF-8 strings for equality where the first string is
-** a "LIKE" expression. Return true (1) if they are the same and 
-** false (0) if they are different.
+** Destroy the private VFS created for the rbu handle passed as the only
+** argument by an earlier call to rbuCreateVfs().
 */
-static int icuLikeCompare(
-  const uint8_t *zPattern,   /* LIKE pattern */
-  const uint8_t *zString,    /* The UTF-8 string to compare against */
-  const UChar32 uEsc         /* The escape character */
+static void rbuDeleteVfs(sqlite3rbu *p){
+  if( p->zVfsName ){
+    sqlite3rbu_destroy_vfs(p->zVfsName);
+    p->zVfsName = 0;
+  }
+}
+
+/*
+** Open and return a new RBU handle. 
+*/
+SQLITE_API sqlite3rbu *SQLITE_STDCALL sqlite3rbu_open(
+  const char *zTarget, 
+  const char *zRbu,
+  const char *zState
 ){
-  static const int MATCH_ONE = (UChar32)'_';
-  static const int MATCH_ALL = (UChar32)'%';
+  sqlite3rbu *p;
+  int nTarget = strlen(zTarget);
+  int nRbu = strlen(zRbu);
+  int nState = zState ? strlen(zState) : 0;
 
-  int iPattern = 0;       /* Current byte index in zPattern */
-  int iString = 0;        /* Current byte index in zString */
+  p = (sqlite3rbu*)sqlite3_malloc(sizeof(sqlite3rbu)+nTarget+1+nRbu+1+nState+1);
+  if( p ){
+    RbuState *pState = 0;
 
-  int prevEscape = 0;     /* True if the previous character was uEsc */
+    /* Create the custom VFS. */
+    memset(p, 0, sizeof(sqlite3rbu));
+    rbuCreateVfs(p);
 
-  while( zPattern[iPattern]!=0 ){
+    /* Open the target database */
+    if( p->rc==SQLITE_OK ){
+      p->zTarget = (char*)&p[1];
+      memcpy(p->zTarget, zTarget, nTarget+1);
+      p->zRbu = &p->zTarget[nTarget+1];
+      memcpy(p->zRbu, zRbu, nRbu+1);
+      if( zState ){
+        p->zState = &p->zRbu[nRbu+1];
+        memcpy(p->zState, zState, nState+1);
+      }
+      rbuOpenDatabase(p);
+    }
 
-    /* Read (and consume) the next character from the input pattern. */
-    UChar32 uPattern;
-    U8_NEXT_UNSAFE(zPattern, iPattern, uPattern);
-    assert(uPattern!=0);
+    /* If it has not already been created, create the rbu_state table */
+    rbuMPrintfExec(p, p->dbRbu, RBU_CREATE_STATE, p->zStateDb);
 
-    /* There are now 4 possibilities:
-    **
-    **     1. uPattern is an unescaped match-all character "%",
-    **     2. uPattern is an unescaped match-one character "_",
-    **     3. uPattern is an unescaped escape character, or
-    **     4. uPattern is to be handled as an ordinary character
-    */
-    if( !prevEscape && uPattern==MATCH_ALL ){
-      /* Case 1. */
-      uint8_t c;
+    if( p->rc==SQLITE_OK ){
+      pState = rbuLoadState(p);
+      assert( pState || p->rc!=SQLITE_OK );
+      if( p->rc==SQLITE_OK ){
 
-      /* Skip any MATCH_ALL or MATCH_ONE characters that follow a
-      ** MATCH_ALL. For each MATCH_ONE, skip one character in the 
-      ** test string.
-      */
-      while( (c=zPattern[iPattern]) == MATCH_ALL || c == MATCH_ONE ){
-        if( c==MATCH_ONE ){
-          if( zString[iString]==0 ) return 0;
-          U8_FWD_1_UNSAFE(zString, iString);
+        if( pState->eStage==0 ){ 
+          rbuDeleteOalFile(p);
+          p->eStage = RBU_STAGE_OAL;
+        }else{
+          p->eStage = pState->eStage;
         }
-        iPattern++;
+        p->nProgress = pState->nProgress;
+        p->iOalSz = pState->iOalSz;
       }
+    }
+    assert( p->rc!=SQLITE_OK || p->eStage!=0 );
 
-      if( zPattern[iPattern]==0 ) return 1;
-
-      while( zString[iString] ){
-        if( icuLikeCompare(&zPattern[iPattern], &zString[iString], uEsc) ){
-          return 1;
-        }
-        U8_FWD_1_UNSAFE(zString, iString);
+    if( p->rc==SQLITE_OK && p->pTargetFd->pWalFd ){
+      if( p->eStage==RBU_STAGE_OAL ){
+        p->rc = SQLITE_ERROR;
+        p->zErrmsg = sqlite3_mprintf("cannot update wal mode database");
+      }else if( p->eStage==RBU_STAGE_MOVE ){
+        p->eStage = RBU_STAGE_CKPT;
+        p->nStep = 0;
       }
-      return 0;
-
-    }else if( !prevEscape && uPattern==MATCH_ONE ){
-      /* Case 2. */
-      if( zString[iString]==0 ) return 0;
-      U8_FWD_1_UNSAFE(zString, iString);
-
-    }else if( !prevEscape && uPattern==uEsc){
-      /* Case 3. */
-      prevEscape = 1;
+    }
 
-    }else{
-      /* Case 4. */
-      UChar32 uString;
-      U8_NEXT_UNSAFE(zString, iString, uString);
-      uString = u_foldCase(uString, U_FOLD_CASE_DEFAULT);
-      uPattern = u_foldCase(uPattern, U_FOLD_CASE_DEFAULT);
-      if( uString!=uPattern ){
-        return 0;
-      }
-      prevEscape = 0;
+    if( p->rc==SQLITE_OK
+     && (p->eStage==RBU_STAGE_OAL || p->eStage==RBU_STAGE_MOVE)
+     && pState->eStage!=0 && p->pTargetFd->iCookie!=pState->iCookie
+    ){   
+      /* At this point (pTargetFd->iCookie) contains the value of the
+      ** change-counter cookie (the thing that gets incremented when a 
+      ** transaction is committed in rollback mode) currently stored on 
+      ** page 1 of the database file. */
+      p->rc = SQLITE_BUSY;
+      p->zErrmsg = sqlite3_mprintf("database modified during rbu update");
     }
-  }
 
-  return zString[iString]==0;
-}
+    if( p->rc==SQLITE_OK ){
+      if( p->eStage==RBU_STAGE_OAL ){
 
-/*
-** Implementation of the like() SQL function.  This function implements
-** the build-in LIKE operator.  The first argument to the function is the
-** pattern and the second argument is the string.  So, the SQL statements:
-**
-**       A LIKE B
-**
-** is implemented as like(B, A). If there is an escape character E, 
-**
-**       A LIKE B ESCAPE E
-**
-** is mapped to like(B, A, E).
-*/
-static void icuLikeFunc(
-  sqlite3_context *context, 
-  int argc, 
-  sqlite3_value **argv
-){
-  const unsigned char *zA = sqlite3_value_text(argv[0]);
-  const unsigned char *zB = sqlite3_value_text(argv[1]);
-  UChar32 uEsc = 0;
+        /* Open transactions both databases. The *-oal file is opened or
+        ** created at this point. */
+        p->rc = sqlite3_exec(p->dbMain, "BEGIN IMMEDIATE", 0, 0, &p->zErrmsg);
+        if( p->rc==SQLITE_OK ){
+          p->rc = sqlite3_exec(p->dbRbu, "BEGIN IMMEDIATE", 0, 0, &p->zErrmsg);
+        }
+  
+        /* Point the object iterator at the first object */
+        if( p->rc==SQLITE_OK ){
+          p->rc = rbuObjIterFirst(p, &p->objiter);
+        }
 
-  /* Limit the length of the LIKE or GLOB pattern to avoid problems
-  ** of deep recursion and N*N behavior in patternCompare().
-  */
-  if( sqlite3_value_bytes(argv[0])>SQLITE_MAX_LIKE_PATTERN_LENGTH ){
-    sqlite3_result_error(context, "LIKE or GLOB pattern too complex", -1);
-    return;
-  }
+        /* If the RBU database contains no data_xxx tables, declare the RBU
+        ** update finished.  */
+        if( p->rc==SQLITE_OK && p->objiter.zTbl==0 ){
+          p->rc = SQLITE_DONE;
+        }
 
+        if( p->rc==SQLITE_OK ){
+          rbuSetupOal(p, pState);
+        }
 
-  if( argc==3 ){
-    /* The escape character string must consist of a single UTF-8 character.
-    ** Otherwise, return an error.
-    */
-    int nE= sqlite3_value_bytes(argv[2]);
-    const unsigned char *zE = sqlite3_value_text(argv[2]);
-    int i = 0;
-    if( zE==0 ) return;
-    U8_NEXT(zE, i, nE, uEsc);
-    if( i!=nE){
-      sqlite3_result_error(context, 
-          "ESCAPE expression must be a single character", -1);
-      return;
+      }else if( p->eStage==RBU_STAGE_MOVE ){
+        /* no-op */
+      }else if( p->eStage==RBU_STAGE_CKPT ){
+        rbuSetupCheckpoint(p, pState);
+      }else if( p->eStage==RBU_STAGE_DONE ){
+        p->rc = SQLITE_DONE;
+      }else{
+        p->rc = SQLITE_CORRUPT;
+      }
     }
-  }
 
-  if( zA && zB ){
-    sqlite3_result_int(context, icuLikeCompare(zA, zB, uEsc));
+    rbuFreeState(pState);
   }
+
+  return p;
 }
 
+
 /*
-** This function is called when an ICU function called from within
-** the implementation of an SQL scalar function returns an error.
-**
-** The scalar function context passed as the first argument is 
-** loaded with an error message based on the following two args.
+** Return the database handle used by pRbu.
 */
-static void icuFunctionError(
-  sqlite3_context *pCtx,       /* SQLite scalar function context */
-  const char *zName,           /* Name of ICU function that failed */
-  UErrorCode e                 /* Error code returned by ICU function */
-){
-  char zBuf[128];
-  sqlite3_snprintf(128, zBuf, "ICU error: %s(): %s", zName, u_errorName(e));
-  zBuf[127] = '\0';
-  sqlite3_result_error(pCtx, zBuf, -1);
+SQLITE_API sqlite3 *SQLITE_STDCALL sqlite3rbu_db(sqlite3rbu *pRbu, int bRbu){
+  sqlite3 *db = 0;
+  if( pRbu ){
+    db = (bRbu ? pRbu->dbRbu : pRbu->dbMain);
+  }
+  return db;
 }
 
+
 /*
-** Function to delete compiled regexp objects. Registered as
-** a destructor function with sqlite3_set_auxdata().
+** If the error code currently stored in the RBU handle is SQLITE_CONSTRAINT,
+** then edit any error message string so as to remove all occurrences of
+** the pattern "rbu_imp_[0-9]*".
 */
-static void icuRegexpDelete(void *p){
-  URegularExpression *pExpr = (URegularExpression *)p;
-  uregex_close(pExpr);
+static void rbuEditErrmsg(sqlite3rbu *p){
+  if( p->rc==SQLITE_CONSTRAINT && p->zErrmsg ){
+    int i;
+    int nErrmsg = strlen(p->zErrmsg);
+    for(i=0; i<(nErrmsg-8); i++){
+      if( memcmp(&p->zErrmsg[i], "rbu_imp_", 8)==0 ){
+        int nDel = 8;
+        while( p->zErrmsg[i+nDel]>='0' && p->zErrmsg[i+nDel]<='9' ) nDel++;
+        memmove(&p->zErrmsg[i], &p->zErrmsg[i+nDel], nErrmsg + 1 - i - nDel);
+        nErrmsg -= nDel;
+      }
+    }
+  }
 }
 
 /*
-** Implementation of SQLite REGEXP operator. This scalar function takes
-** two arguments. The first is a regular expression pattern to compile
-** the second is a string to match against that pattern. If either 
-** argument is an SQL NULL, then NULL Is returned. Otherwise, the result
-** is 1 if the string matches the pattern, or 0 otherwise.
-**
-** SQLite maps the regexp() function to the regexp() operator such
-** that the following two are equivalent:
-**
-**     zString REGEXP zPattern
-**     regexp(zPattern, zString)
-**
-** Uses the following ICU regexp APIs:
-**
-**     uregex_open()
-**     uregex_matches()
-**     uregex_close()
+** Close the RBU handle.
 */
-static void icuRegexpFunc(sqlite3_context *p, int nArg, sqlite3_value **apArg){
-  UErrorCode status = U_ZERO_ERROR;
-  URegularExpression *pExpr;
-  UBool res;
-  const UChar *zString = sqlite3_value_text16(apArg[1]);
+SQLITE_API int SQLITE_STDCALL sqlite3rbu_close(sqlite3rbu *p, char **pzErrmsg){
+  int rc;
+  if( p ){
 
-  (void)nArg;  /* Unused parameter */
+    /* Commit the transaction to the *-oal file. */
+    if( p->rc==SQLITE_OK && p->eStage==RBU_STAGE_OAL ){
+      p->rc = sqlite3_exec(p->dbMain, "COMMIT", 0, 0, &p->zErrmsg);
+    }
 
-  /* If the left hand side of the regexp operator is NULL, 
-  ** then the result is also NULL. 
-  */
-  if( !zString ){
-    return;
-  }
+    rbuSaveState(p, p->eStage);
 
-  pExpr = sqlite3_get_auxdata(p, 0);
-  if( !pExpr ){
-    const UChar *zPattern = sqlite3_value_text16(apArg[0]);
-    if( !zPattern ){
-      return;
+    if( p->rc==SQLITE_OK && p->eStage==RBU_STAGE_OAL ){
+      p->rc = sqlite3_exec(p->dbRbu, "COMMIT", 0, 0, &p->zErrmsg);
     }
-    pExpr = uregex_open(zPattern, -1, 0, 0, &status);
 
-    if( U_SUCCESS(status) ){
-      sqlite3_set_auxdata(p, 0, pExpr, icuRegexpDelete);
-    }else{
-      assert(!pExpr);
-      icuFunctionError(p, "uregex_open", status);
-      return;
-    }
-  }
+    /* Close any open statement handles. */
+    rbuObjIterFinalize(&p->objiter);
 
-  /* Configure the text that the regular expression operates on. */
-  uregex_setText(pExpr, zString, -1, &status);
-  if( !U_SUCCESS(status) ){
-    icuFunctionError(p, "uregex_setText", status);
-    return;
-  }
+    /* Close the open database handle and VFS object. */
+    sqlite3_close(p->dbMain);
+    sqlite3_close(p->dbRbu);
+    rbuDeleteVfs(p);
+    sqlite3_free(p->aBuf);
+    sqlite3_free(p->aFrame);
 
-  /* Attempt the match */
-  res = uregex_matches(pExpr, 0, &status);
-  if( !U_SUCCESS(status) ){
-    icuFunctionError(p, "uregex_matches", status);
-    return;
+    rbuEditErrmsg(p);
+    rc = p->rc;
+    *pzErrmsg = p->zErrmsg;
+    sqlite3_free(p);
+  }else{
+    rc = SQLITE_NOMEM;
+    *pzErrmsg = 0;
   }
-
-  /* Set the text that the regular expression operates on to a NULL
-  ** pointer. This is not really necessary, but it is tidier than 
-  ** leaving the regular expression object configured with an invalid
-  ** pointer after this function returns.
-  */
-  uregex_setText(pExpr, 0, 0, &status);
-
-  /* Return 1 or 0. */
-  sqlite3_result_int(p, res ? 1 : 0);
+  return rc;
 }
 
 /*
-** Implementations of scalar functions for case mapping - upper() and 
-** lower(). Function upper() converts its input to upper-case (ABC).
-** Function lower() converts to lower-case (abc).
+** Return the total number of key-value operations (inserts, deletes or 
+** updates) that have been performed on the target database since the
+** current RBU update was started.
+*/
+SQLITE_API sqlite3_int64 SQLITE_STDCALL sqlite3rbu_progress(sqlite3rbu *pRbu){
+  return pRbu->nProgress;
+}
+
+/**************************************************************************
+** Beginning of RBU VFS shim methods. The VFS shim modifies the behaviour
+** of a standard VFS in the following ways:
 **
-** ICU provides two types of case mapping, "general" case mapping and
-** "language specific". Refer to ICU documentation for the differences
-** between the two.
+** 1. Whenever the first page of a main database file is read or 
+**    written, the value of the change-counter cookie is stored in
+**    rbu_file.iCookie. Similarly, the value of the "write-version"
+**    database header field is stored in rbu_file.iWriteVer. This ensures
+**    that the values are always trustworthy within an open transaction.
 **
-** To utilise "general" case mapping, the upper() or lower() scalar 
-** functions are invoked with one argument:
+** 2. Whenever an SQLITE_OPEN_WAL file is opened, the (rbu_file.pWalFd)
+**    member variable of the associated database file descriptor is set
+**    to point to the new file. A mutex protected linked list of all main 
+**    db fds opened using a particular RBU VFS is maintained at 
+**    rbu_vfs.pMain to facilitate this.
 **
-**     upper('ABC') -> 'abc'
-**     lower('abc') -> 'ABC'
+** 3. Using a new file-control "SQLITE_FCNTL_RBU", a main db rbu_file 
+**    object can be marked as the target database of an RBU update. This
+**    turns on the following extra special behaviour:
 **
-** To access ICU "language specific" case mapping, upper() or lower()
-** should be invoked with two arguments. The second argument is the name
-** of the locale to use. Passing an empty string ("") or SQL NULL value
-** as the second argument is the same as invoking the 1 argument version
-** of upper() or lower().
+** 3a. If xAccess() is called to check if there exists a *-wal file 
+**     associated with an RBU target database currently in RBU_STAGE_OAL
+**     stage (preparing the *-oal file), the following special handling
+**     applies:
 **
-**     lower('I', 'en_us') -> 'i'
-**     lower('I', 'tr_tr') -> 'ı' (small dotless i)
+**      * if the *-wal file does exist, return SQLITE_CANTOPEN. An RBU
+**        target database may not be in wal mode already.
 **
-** http://www.icu-project.org/userguide/posix.html#case_mappings
+**      * if the *-wal file does not exist, set the output parameter to
+**        non-zero (to tell SQLite that it does exist) anyway.
+**
+**     Then, when xOpen() is called to open the *-wal file associated with
+**     the RBU target in RBU_STAGE_OAL stage, instead of opening the *-wal
+**     file, the rbu vfs opens the corresponding *-oal file instead. 
+**
+** 3b. The *-shm pages returned by xShmMap() for a target db file in
+**     RBU_STAGE_OAL mode are actually stored in heap memory. This is to
+**     avoid creating a *-shm file on disk. Additionally, xShmLock() calls
+**     are no-ops on target database files in RBU_STAGE_OAL mode. This is
+**     because assert() statements in some VFS implementations fail if 
+**     xShmLock() is called before xShmMap().
+**
+** 3c. If an EXCLUSIVE lock is attempted on a target database file in any
+**     mode except RBU_STAGE_DONE (all work completed and checkpointed), it 
+**     fails with an SQLITE_BUSY error. This is to stop RBU connections
+**     from automatically checkpointing a *-wal (or *-oal) file from within
+**     sqlite3_close().
+**
+** 3d. In RBU_STAGE_CAPTURE mode, all xRead() calls on the wal file, and
+**     all xWrite() calls on the target database file perform no IO. 
+**     Instead the frame and page numbers that would be read and written
+**     are recorded. Additionally, successful attempts to obtain exclusive
+**     xShmLock() WRITER, CHECKPOINTER and READ0 locks on the target 
+**     database file are recorded. xShmLock() calls to unlock the same
+**     locks are no-ops (so that once obtained, these locks are never
+**     relinquished). Finally, calls to xSync() on the target database
+**     file fail with SQLITE_INTERNAL errors.
 */
-static void icuCaseFunc16(sqlite3_context *p, int nArg, sqlite3_value **apArg){
-  const UChar *zInput;
-  UChar *zOutput;
-  int nInput;
-  int nOutput;
-
-  UErrorCode status = U_ZERO_ERROR;
-  const char *zLocale = 0;
-
-  assert(nArg==1 || nArg==2);
-  if( nArg==2 ){
-    zLocale = (const char *)sqlite3_value_text(apArg[1]);
-  }
 
-  zInput = sqlite3_value_text16(apArg[0]);
-  if( !zInput ){
-    return;
+static void rbuUnlockShm(rbu_file *p){
+  if( p->pRbu ){
+    int (*xShmLock)(sqlite3_file*,int,int,int) = p->pReal->pMethods->xShmLock;
+    int i;
+    for(i=0; i<SQLITE_SHM_NLOCK;i++){
+      if( (1<<i) & p->pRbu->mLock ){
+        xShmLock(p->pReal, i, 1, SQLITE_SHM_UNLOCK|SQLITE_SHM_EXCLUSIVE);
+      }
+    }
+    p->pRbu->mLock = 0;
   }
-  nInput = sqlite3_value_bytes16(apArg[0]);
+}
 
-  nOutput = nInput * 2 + 2;
-  zOutput = sqlite3_malloc(nOutput);
-  if( !zOutput ){
-    return;
-  }
+/*
+** Close an rbu file.
+*/
+static int rbuVfsClose(sqlite3_file *pFile){
+  rbu_file *p = (rbu_file*)pFile;
+  int rc;
+  int i;
 
-  if( sqlite3_user_data(p) ){
-    u_strToUpper(zOutput, nOutput/2, zInput, nInput/2, zLocale, &status);
-  }else{
-    u_strToLower(zOutput, nOutput/2, zInput, nInput/2, zLocale, &status);
+  /* Free the contents of the apShm[] array. And the array itself. */
+  for(i=0; i<p->nShm; i++){
+    sqlite3_free(p->apShm[i]);
   }
+  sqlite3_free(p->apShm);
+  p->apShm = 0;
+  sqlite3_free(p->zDel);
 
-  if( !U_SUCCESS(status) ){
-    icuFunctionError(p, "u_strToLower()/u_strToUpper", status);
-    return;
+  if( p->openFlags & SQLITE_OPEN_MAIN_DB ){
+    rbu_file **pp;
+    sqlite3_mutex_enter(p->pRbuVfs->mutex);
+    for(pp=&p->pRbuVfs->pMain; *pp!=p; pp=&((*pp)->pMainNext));
+    *pp = p->pMainNext;
+    sqlite3_mutex_leave(p->pRbuVfs->mutex);
+    rbuUnlockShm(p);
+    p->pReal->pMethods->xShmUnmap(p->pReal, 0);
   }
 
-  sqlite3_result_text16(p, zOutput, -1, xFree);
+  /* Close the underlying file handle */
+  rc = p->pReal->pMethods->xClose(p->pReal);
+  return rc;
 }
 
+
 /*
-** Collation sequence destructor function. The pCtx argument points to
-** a UCollator structure previously allocated using ucol_open().
+** Read and return an unsigned 32-bit big-endian integer from the buffer 
+** passed as the only argument.
 */
-static void icuCollationDel(void *pCtx){
-  UCollator *p = (UCollator *)pCtx;
-  ucol_close(p);
+static u32 rbuGetU32(u8 *aBuf){
+  return ((u32)aBuf[0] << 24)
+       + ((u32)aBuf[1] << 16)
+       + ((u32)aBuf[2] <<  8)
+       + ((u32)aBuf[3]);
 }
 
 /*
-** Collation sequence comparison function. The pCtx argument points to
-** a UCollator structure previously allocated using ucol_open().
+** Read data from an rbuVfs-file.
 */
-static int icuCollationColl(
-  void *pCtx,
-  int nLeft,
-  const void *zLeft,
-  int nRight,
-  const void *zRight
+static int rbuVfsRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
 ){
-  UCollationResult res;
-  UCollator *p = (UCollator *)pCtx;
-  res = ucol_strcoll(p, (UChar *)zLeft, nLeft/2, (UChar *)zRight, nRight/2);
-  switch( res ){
-    case UCOL_LESS:    return -1;
-    case UCOL_GREATER: return +1;
-    case UCOL_EQUAL:   return 0;
+  rbu_file *p = (rbu_file*)pFile;
+  sqlite3rbu *pRbu = p->pRbu;
+  int rc;
+
+  if( pRbu && pRbu->eStage==RBU_STAGE_CAPTURE ){
+    assert( p->openFlags & SQLITE_OPEN_WAL );
+    rc = rbuCaptureWalRead(p->pRbu, iOfst, iAmt);
+  }else{
+    if( pRbu && pRbu->eStage==RBU_STAGE_OAL 
+     && (p->openFlags & SQLITE_OPEN_WAL) 
+     && iOfst>=pRbu->iOalSz 
+    ){
+      rc = SQLITE_OK;
+      memset(zBuf, 0, iAmt);
+    }else{
+      rc = p->pReal->pMethods->xRead(p->pReal, zBuf, iAmt, iOfst);
+    }
+    if( rc==SQLITE_OK && iOfst==0 && (p->openFlags & SQLITE_OPEN_MAIN_DB) ){
+      /* These look like magic numbers. But they are stable, as they are part
+       ** of the definition of the SQLite file format, which may not change. */
+      u8 *pBuf = (u8*)zBuf;
+      p->iCookie = rbuGetU32(&pBuf[24]);
+      p->iWriteVer = pBuf[19];
+    }
   }
-  assert(!"Unexpected return value from ucol_strcoll()");
-  return 0;
+  return rc;
 }
 
 /*
-** Implementation of the scalar function icu_load_collation().
-**
-** This scalar function is used to add ICU collation based collation 
-** types to an SQLite database connection. It is intended to be called
-** as follows:
-**
-**     SELECT icu_load_collation(<locale>, <collation-name>);
-**
-** Where <locale> is a string containing an ICU locale identifier (i.e.
-** "en_AU", "tr_TR" etc.) and <collation-name> is the name of the
-** collation sequence to create.
+** Write data to an rbuVfs-file.
 */
-static void icuLoadCollation(
-  sqlite3_context *p, 
-  int nArg, 
-  sqlite3_value **apArg
+static int rbuVfsWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
 ){
-  sqlite3 *db = (sqlite3 *)sqlite3_user_data(p);
-  UErrorCode status = U_ZERO_ERROR;
-  const char *zLocale;      /* Locale identifier - (eg. "jp_JP") */
-  const char *zName;        /* SQL Collation sequence name (eg. "japanese") */
-  UCollator *pUCollator;    /* ICU library collation object */
-  int rc;                   /* Return code from sqlite3_create_collation_x() */
-
-  assert(nArg==2);
-  zLocale = (const char *)sqlite3_value_text(apArg[0]);
-  zName = (const char *)sqlite3_value_text(apArg[1]);
+  rbu_file *p = (rbu_file*)pFile;
+  sqlite3rbu *pRbu = p->pRbu;
+  int rc;
 
-  if( !zLocale || !zName ){
-    return;
+  if( pRbu && pRbu->eStage==RBU_STAGE_CAPTURE ){
+    assert( p->openFlags & SQLITE_OPEN_MAIN_DB );
+    rc = rbuCaptureDbWrite(p->pRbu, iOfst);
+  }else{
+    if( pRbu && pRbu->eStage==RBU_STAGE_OAL 
+     && (p->openFlags & SQLITE_OPEN_WAL) 
+     && iOfst>=pRbu->iOalSz
+    ){
+      pRbu->iOalSz = iAmt + iOfst;
+    }
+    rc = p->pReal->pMethods->xWrite(p->pReal, zBuf, iAmt, iOfst);
+    if( rc==SQLITE_OK && iOfst==0 && (p->openFlags & SQLITE_OPEN_MAIN_DB) ){
+      /* These look like magic numbers. But they are stable, as they are part
+      ** of the definition of the SQLite file format, which may not change. */
+      u8 *pBuf = (u8*)zBuf;
+      p->iCookie = rbuGetU32(&pBuf[24]);
+      p->iWriteVer = pBuf[19];
+    }
   }
+  return rc;
+}
 
-  pUCollator = ucol_open(zLocale, &status);
-  if( !U_SUCCESS(status) ){
-    icuFunctionError(p, "ucol_open", status);
-    return;
-  }
-  assert(p);
+/*
+** Truncate an rbuVfs-file.
+*/
+static int rbuVfsTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  rbu_file *p = (rbu_file*)pFile;
+  return p->pReal->pMethods->xTruncate(p->pReal, size);
+}
 
-  rc = sqlite3_create_collation_v2(db, zName, SQLITE_UTF16, (void *)pUCollator, 
-      icuCollationColl, icuCollationDel
-  );
-  if( rc!=SQLITE_OK ){
-    ucol_close(pUCollator);
-    sqlite3_result_error(p, "Error registering collation function", -1);
+/*
+** Sync an rbuVfs-file.
+*/
+static int rbuVfsSync(sqlite3_file *pFile, int flags){
+  rbu_file *p = (rbu_file *)pFile;
+  if( p->pRbu && p->pRbu->eStage==RBU_STAGE_CAPTURE ){
+    if( p->openFlags & SQLITE_OPEN_MAIN_DB ){
+      return SQLITE_INTERNAL;
+    }
+    return SQLITE_OK;
   }
+  return p->pReal->pMethods->xSync(p->pReal, flags);
 }
 
 /*
-** Register the ICU extension functions with database db.
+** Return the current file-size of an rbuVfs-file.
 */
-SQLITE_PRIVATE int sqlite3IcuInit(sqlite3 *db){
-  struct IcuScalar {
-    const char *zName;                        /* Function name */
-    int nArg;                                 /* Number of arguments */
-    int enc;                                  /* Optimal text encoding */
-    void *pContext;                           /* sqlite3_user_data() context */
-    void (*xFunc)(sqlite3_context*,int,sqlite3_value**);
-  } scalars[] = {
-    {"regexp", 2, SQLITE_ANY,          0, icuRegexpFunc},
-
-    {"lower",  1, SQLITE_UTF16,        0, icuCaseFunc16},
-    {"lower",  2, SQLITE_UTF16,        0, icuCaseFunc16},
-    {"upper",  1, SQLITE_UTF16, (void*)1, icuCaseFunc16},
-    {"upper",  2, SQLITE_UTF16, (void*)1, icuCaseFunc16},
-
-    {"lower",  1, SQLITE_UTF8,         0, icuCaseFunc16},
-    {"lower",  2, SQLITE_UTF8,         0, icuCaseFunc16},
-    {"upper",  1, SQLITE_UTF8,  (void*)1, icuCaseFunc16},
-    {"upper",  2, SQLITE_UTF8,  (void*)1, icuCaseFunc16},
-
-    {"like",   2, SQLITE_UTF8,         0, icuLikeFunc},
-    {"like",   3, SQLITE_UTF8,         0, icuLikeFunc},
-
-    {"icu_load_collation",  2, SQLITE_UTF8, (void*)db, icuLoadCollation},
-  };
+static int rbuVfsFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  rbu_file *p = (rbu_file *)pFile;
+  return p->pReal->pMethods->xFileSize(p->pReal, pSize);
+}
 
+/*
+** Lock an rbuVfs-file.
+*/
+static int rbuVfsLock(sqlite3_file *pFile, int eLock){
+  rbu_file *p = (rbu_file*)pFile;
+  sqlite3rbu *pRbu = p->pRbu;
   int rc = SQLITE_OK;
-  int i;
 
-  for(i=0; rc==SQLITE_OK && i<(int)(sizeof(scalars)/sizeof(scalars[0])); i++){
-    struct IcuScalar *p = &scalars[i];
-    rc = sqlite3_create_function(
-        db, p->zName, p->nArg, p->enc, p->pContext, p->xFunc, 0, 0
-    );
+  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
+  if( pRbu && eLock==SQLITE_LOCK_EXCLUSIVE && pRbu->eStage!=RBU_STAGE_DONE ){
+    /* Do not allow EXCLUSIVE locks. Preventing SQLite from taking this 
+    ** prevents it from checkpointing the database from sqlite3_close(). */
+    rc = SQLITE_BUSY;
+  }else{
+    rc = p->pReal->pMethods->xLock(p->pReal, eLock);
   }
 
   return rc;
 }
 
-#if !SQLITE_CORE
-#ifdef _WIN32
-__declspec(dllexport)
-#endif
-SQLITE_API int SQLITE_STDCALL sqlite3_icu_init(
-  sqlite3 *db, 
-  char **pzErrMsg,
-  const sqlite3_api_routines *pApi
-){
-  SQLITE_EXTENSION_INIT2(pApi)
-  return sqlite3IcuInit(db);
+/*
+** Unlock an rbuVfs-file.
+*/
+static int rbuVfsUnlock(sqlite3_file *pFile, int eLock){
+  rbu_file *p = (rbu_file *)pFile;
+  return p->pReal->pMethods->xUnlock(p->pReal, eLock);
 }
-#endif
 
-#endif
+/*
+** Check if another file-handle holds a RESERVED lock on an rbuVfs-file.
+*/
+static int rbuVfsCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  rbu_file *p = (rbu_file *)pFile;
+  return p->pReal->pMethods->xCheckReservedLock(p->pReal, pResOut);
+}
 
-/************** End of icu.c *************************************************/
-/************** Begin file fts3_icu.c ****************************************/
 /*
-** 2007 June 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file implements a tokenizer for fts3 based on the ICU library.
+** File control method. For custom operations on an rbuVfs-file.
 */
-#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
-#ifdef SQLITE_ENABLE_ICU
+static int rbuVfsFileControl(sqlite3_file *pFile, int op, void *pArg){
+  rbu_file *p = (rbu_file *)pFile;
+  int (*xControl)(sqlite3_file*,int,void*) = p->pReal->pMethods->xFileControl;
+  int rc;
 
-/* #include <assert.h> */
-/* #include <string.h> */
+  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB)
+       || p->openFlags & (SQLITE_OPEN_TRANSIENT_DB|SQLITE_OPEN_TEMP_JOURNAL)
+  );
+  if( op==SQLITE_FCNTL_RBU ){
+    sqlite3rbu *pRbu = (sqlite3rbu*)pArg;
+
+    /* First try to find another RBU vfs lower down in the vfs stack. If
+    ** one is found, this vfs will operate in pass-through mode. The lower
+    ** level vfs will do the special RBU handling.  */
+    rc = xControl(p->pReal, op, pArg);
+
+    if( rc==SQLITE_NOTFOUND ){
+      /* Now search for a zipvfs instance lower down in the VFS stack. If
+      ** one is found, this is an error.  */
+      void *dummy = 0;
+      rc = xControl(p->pReal, SQLITE_FCNTL_ZIPVFS, &dummy);
+      if( rc==SQLITE_OK ){
+        rc = SQLITE_ERROR;
+        pRbu->zErrmsg = sqlite3_mprintf("rbu/zipvfs setup error");
+      }else if( rc==SQLITE_NOTFOUND ){
+        pRbu->pTargetFd = p;
+        p->pRbu = pRbu;
+        if( p->pWalFd ) p->pWalFd->pRbu = pRbu;
+        rc = SQLITE_OK;
+      }
+    }
+    return rc;
+  }
 
-#include <unicode/ubrk.h>
-/* #include <unicode/ucol.h> */
-/* #include <unicode/ustring.h> */
-#include <unicode/utf16.h>
+  rc = xControl(p->pReal, op, pArg);
+  if( rc==SQLITE_OK && op==SQLITE_FCNTL_VFSNAME ){
+    rbu_vfs *pRbuVfs = p->pRbuVfs;
+    char *zIn = *(char**)pArg;
+    char *zOut = sqlite3_mprintf("rbu(%s)/%z", pRbuVfs->base.zName, zIn);
+    *(char**)pArg = zOut;
+    if( zOut==0 ) rc = SQLITE_NOMEM;
+  }
 
-typedef struct IcuTokenizer IcuTokenizer;
-typedef struct IcuCursor IcuCursor;
+  return rc;
+}
 
-struct IcuTokenizer {
-  sqlite3_tokenizer base;
-  char *zLocale;
-};
+/*
+** Return the sector-size in bytes for an rbuVfs-file.
+*/
+static int rbuVfsSectorSize(sqlite3_file *pFile){
+  rbu_file *p = (rbu_file *)pFile;
+  return p->pReal->pMethods->xSectorSize(p->pReal);
+}
 
-struct IcuCursor {
-  sqlite3_tokenizer_cursor base;
+/*
+** Return the device characteristic flags supported by an rbuVfs-file.
+*/
+static int rbuVfsDeviceCharacteristics(sqlite3_file *pFile){
+  rbu_file *p = (rbu_file *)pFile;
+  return p->pReal->pMethods->xDeviceCharacteristics(p->pReal);
+}
 
-  UBreakIterator *pIter;      /* ICU break-iterator object */
-  int nChar;                  /* Number of UChar elements in pInput */
-  UChar *aChar;               /* Copy of input using utf-16 encoding */
-  int *aOffset;               /* Offsets of each character in utf-8 input */
+/*
+** Take or release a shared-memory lock.
+*/
+static int rbuVfsShmLock(sqlite3_file *pFile, int ofst, int n, int flags){
+  rbu_file *p = (rbu_file*)pFile;
+  sqlite3rbu *pRbu = p->pRbu;
+  int rc = SQLITE_OK;
 
-  int nBuffer;
-  char *zBuffer;
+#ifdef SQLITE_AMALGAMATION
+    assert( WAL_CKPT_LOCK==1 );
+#endif
 
-  int iToken;
-};
+  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
+  if( pRbu && (pRbu->eStage==RBU_STAGE_OAL || pRbu->eStage==RBU_STAGE_MOVE) ){
+    /* Magic number 1 is the WAL_CKPT_LOCK lock. Preventing SQLite from
+    ** taking this lock also prevents any checkpoints from occurring. 
+    ** todo: really, it's not clear why this might occur, as 
+    ** wal_autocheckpoint ought to be turned off.  */
+    if( ofst==WAL_LOCK_CKPT && n==1 ) rc = SQLITE_BUSY;
+  }else{
+    int bCapture = 0;
+    if( n==1 && (flags & SQLITE_SHM_EXCLUSIVE)
+     && pRbu && pRbu->eStage==RBU_STAGE_CAPTURE
+     && (ofst==WAL_LOCK_WRITE || ofst==WAL_LOCK_CKPT || ofst==WAL_LOCK_READ0)
+    ){
+      bCapture = 1;
+    }
+
+    if( bCapture==0 || 0==(flags & SQLITE_SHM_UNLOCK) ){
+      rc = p->pReal->pMethods->xShmLock(p->pReal, ofst, n, flags);
+      if( bCapture && rc==SQLITE_OK ){
+        pRbu->mLock |= (1 << ofst);
+      }
+    }
+  }
+
+  return rc;
+}
 
 /*
-** Create a new tokenizer instance.
+** Obtain a pointer to a mapping of a single 32KiB page of the *-shm file.
 */
-static int icuCreate(
-  int argc,                            /* Number of entries in argv[] */
-  const char * const *argv,            /* Tokenizer creation arguments */
-  sqlite3_tokenizer **ppTokenizer      /* OUT: Created tokenizer */
+static int rbuVfsShmMap(
+  sqlite3_file *pFile, 
+  int iRegion, 
+  int szRegion, 
+  int isWrite, 
+  void volatile **pp
 ){
-  IcuTokenizer *p;
-  int n = 0;
+  rbu_file *p = (rbu_file*)pFile;
+  int rc = SQLITE_OK;
+  int eStage = (p->pRbu ? p->pRbu->eStage : 0);
+
+  /* If not in RBU_STAGE_OAL, allow this call to pass through. Or, if this
+  ** rbu is in the RBU_STAGE_OAL state, use heap memory for *-shm space 
+  ** instead of a file on disk.  */
+  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
+  if( eStage==RBU_STAGE_OAL || eStage==RBU_STAGE_MOVE ){
+    if( iRegion<=p->nShm ){
+      int nByte = (iRegion+1) * sizeof(char*);
+      char **apNew = (char**)sqlite3_realloc(p->apShm, nByte);
+      if( apNew==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        memset(&apNew[p->nShm], 0, sizeof(char*) * (1 + iRegion - p->nShm));
+        p->apShm = apNew;
+        p->nShm = iRegion+1;
+      }
+    }
 
-  if( argc>0 ){
-    n = strlen(argv[0])+1;
-  }
-  p = (IcuTokenizer *)sqlite3_malloc(sizeof(IcuTokenizer)+n);
-  if( !p ){
-    return SQLITE_NOMEM;
-  }
-  memset(p, 0, sizeof(IcuTokenizer));
+    if( rc==SQLITE_OK && p->apShm[iRegion]==0 ){
+      char *pNew = (char*)sqlite3_malloc(szRegion);
+      if( pNew==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        memset(pNew, 0, szRegion);
+        p->apShm[iRegion] = pNew;
+      }
+    }
 
-  if( n ){
-    p->zLocale = (char *)&p[1];
-    memcpy(p->zLocale, argv[0], n);
+    if( rc==SQLITE_OK ){
+      *pp = p->apShm[iRegion];
+    }else{
+      *pp = 0;
+    }
+  }else{
+    assert( p->apShm==0 );
+    rc = p->pReal->pMethods->xShmMap(p->pReal, iRegion, szRegion, isWrite, pp);
   }
 
-  *ppTokenizer = (sqlite3_tokenizer *)p;
-
-  return SQLITE_OK;
+  return rc;
 }
 
 /*
-** Destroy a tokenizer
+** Memory barrier.
 */
-static int icuDestroy(sqlite3_tokenizer *pTokenizer){
-  IcuTokenizer *p = (IcuTokenizer *)pTokenizer;
-  sqlite3_free(p);
-  return SQLITE_OK;
+static void rbuVfsShmBarrier(sqlite3_file *pFile){
+  rbu_file *p = (rbu_file *)pFile;
+  p->pReal->pMethods->xShmBarrier(p->pReal);
 }
 
 /*
-** Prepare to begin tokenizing a particular string.  The input
-** string to be tokenized is pInput[0..nBytes-1].  A cursor
-** used to incrementally tokenize this string is returned in 
-** *ppCursor.
+** The xShmUnmap method.
 */
-static int icuOpen(
-  sqlite3_tokenizer *pTokenizer,         /* The tokenizer */
-  const char *zInput,                    /* Input string */
-  int nInput,                            /* Length of zInput in bytes */
-  sqlite3_tokenizer_cursor **ppCursor    /* OUT: Tokenization cursor */
-){
-  IcuTokenizer *p = (IcuTokenizer *)pTokenizer;
-  IcuCursor *pCsr;
-
-  const int32_t opt = U_FOLD_CASE_DEFAULT;
-  UErrorCode status = U_ZERO_ERROR;
-  int nChar;
-
-  UChar32 c;
-  int iInput = 0;
-  int iOut = 0;
-
-  *ppCursor = 0;
+static int rbuVfsShmUnmap(sqlite3_file *pFile, int delFlag){
+  rbu_file *p = (rbu_file*)pFile;
+  int rc = SQLITE_OK;
+  int eStage = (p->pRbu ? p->pRbu->eStage : 0);
 
-  if( zInput==0 ){
-    nInput = 0;
-    zInput = "";
-  }else if( nInput<0 ){
-    nInput = strlen(zInput);
-  }
-  nChar = nInput+1;
-  pCsr = (IcuCursor *)sqlite3_malloc(
-      sizeof(IcuCursor) +                /* IcuCursor */
-      ((nChar+3)&~3) * sizeof(UChar) +   /* IcuCursor.aChar[] */
-      (nChar+1) * sizeof(int)            /* IcuCursor.aOffset[] */
-  );
-  if( !pCsr ){
-    return SQLITE_NOMEM;
+  assert( p->openFlags & (SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_TEMP_DB) );
+  if( eStage==RBU_STAGE_OAL || eStage==RBU_STAGE_MOVE ){
+    /* no-op */
+  }else{
+    /* Release the checkpointer and writer locks */
+    rbuUnlockShm(p);
+    rc = p->pReal->pMethods->xShmUnmap(p->pReal, delFlag);
   }
-  memset(pCsr, 0, sizeof(IcuCursor));
-  pCsr->aChar = (UChar *)&pCsr[1];
-  pCsr->aOffset = (int *)&pCsr->aChar[(nChar+3)&~3];
+  return rc;
+}
 
-  pCsr->aOffset[iOut] = iInput;
-  U8_NEXT(zInput, iInput, nInput, c); 
-  while( c>0 ){
-    int isError = 0;
-    c = u_foldCase(c, opt);
-    U16_APPEND(pCsr->aChar, iOut, nChar, c, isError);
-    if( isError ){
-      sqlite3_free(pCsr);
-      return SQLITE_ERROR;
-    }
-    pCsr->aOffset[iOut] = iInput;
+/*
+** Given that zWal points to a buffer containing a wal file name passed to 
+** either the xOpen() or xAccess() VFS method, return a pointer to the
+** file-handle opened by the same database connection on the corresponding
+** database file.
+*/
+static rbu_file *rbuFindMaindb(rbu_vfs *pRbuVfs, const char *zWal){
+  rbu_file *pDb;
+  sqlite3_mutex_enter(pRbuVfs->mutex);
+  for(pDb=pRbuVfs->pMain; pDb && pDb->zWal!=zWal; pDb=pDb->pMainNext);
+  sqlite3_mutex_leave(pRbuVfs->mutex);
+  return pDb;
+}
 
-    if( iInput<nInput ){
-      U8_NEXT(zInput, iInput, nInput, c);
-    }else{
-      c = 0;
+/*
+** Open an rbu file handle.
+*/
+static int rbuVfsOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  static sqlite3_io_methods rbuvfs_io_methods = {
+    2,                            /* iVersion */
+    rbuVfsClose,                  /* xClose */
+    rbuVfsRead,                   /* xRead */
+    rbuVfsWrite,                  /* xWrite */
+    rbuVfsTruncate,               /* xTruncate */
+    rbuVfsSync,                   /* xSync */
+    rbuVfsFileSize,               /* xFileSize */
+    rbuVfsLock,                   /* xLock */
+    rbuVfsUnlock,                 /* xUnlock */
+    rbuVfsCheckReservedLock,      /* xCheckReservedLock */
+    rbuVfsFileControl,            /* xFileControl */
+    rbuVfsSectorSize,             /* xSectorSize */
+    rbuVfsDeviceCharacteristics,  /* xDeviceCharacteristics */
+    rbuVfsShmMap,                 /* xShmMap */
+    rbuVfsShmLock,                /* xShmLock */
+    rbuVfsShmBarrier,             /* xShmBarrier */
+    rbuVfsShmUnmap                /* xShmUnmap */
+  };
+  rbu_vfs *pRbuVfs = (rbu_vfs*)pVfs;
+  sqlite3_vfs *pRealVfs = pRbuVfs->pRealVfs;
+  rbu_file *pFd = (rbu_file *)pFile;
+  int rc = SQLITE_OK;
+  const char *zOpen = zName;
+
+  memset(pFd, 0, sizeof(rbu_file));
+  pFd->pReal = (sqlite3_file*)&pFd[1];
+  pFd->pRbuVfs = pRbuVfs;
+  pFd->openFlags = flags;
+  if( zName ){
+    if( flags & SQLITE_OPEN_MAIN_DB ){
+      /* A main database has just been opened. The following block sets
+      ** (pFd->zWal) to point to a buffer owned by SQLite that contains
+      ** the name of the *-wal file this db connection will use. SQLite
+      ** happens to pass a pointer to this buffer when using xAccess()
+      ** or xOpen() to operate on the *-wal file.  */
+      int n = strlen(zName);
+      const char *z = &zName[n];
+      if( flags & SQLITE_OPEN_URI ){
+        int odd = 0;
+        while( 1 ){
+          if( z[0]==0 ){
+            odd = 1 - odd;
+            if( odd && z[1]==0 ) break;
+          }
+          z++;
+        }
+        z += 2;
+      }else{
+        while( *z==0 ) z++;
+      }
+      z += (n + 8 + 1);
+      pFd->zWal = z;
+    }
+    else if( flags & SQLITE_OPEN_WAL ){
+      rbu_file *pDb = rbuFindMaindb(pRbuVfs, zName);
+      if( pDb ){
+        if( pDb->pRbu && pDb->pRbu->eStage==RBU_STAGE_OAL ){
+          /* This call is to open a *-wal file. Intead, open the *-oal. This
+          ** code ensures that the string passed to xOpen() is terminated by a
+          ** pair of '\0' bytes in case the VFS attempts to extract a URI 
+          ** parameter from it.  */
+          int nCopy = strlen(zName);
+          char *zCopy = sqlite3_malloc(nCopy+2);
+          if( zCopy ){
+            memcpy(zCopy, zName, nCopy);
+            zCopy[nCopy-3] = 'o';
+            zCopy[nCopy] = '\0';
+            zCopy[nCopy+1] = '\0';
+            zOpen = (const char*)(pFd->zDel = zCopy);
+          }else{
+            rc = SQLITE_NOMEM;
+          }
+          pFd->pRbu = pDb->pRbu;
+        }
+        pDb->pWalFd = pFd;
+      }
     }
   }
 
-  pCsr->pIter = ubrk_open(UBRK_WORD, p->zLocale, pCsr->aChar, iOut, &status);
-  if( !U_SUCCESS(status) ){
-    sqlite3_free(pCsr);
-    return SQLITE_ERROR;
+  if( rc==SQLITE_OK ){
+    rc = pRealVfs->xOpen(pRealVfs, zOpen, pFd->pReal, flags, pOutFlags);
+  }
+  if( pFd->pReal->pMethods ){
+    /* The xOpen() operation has succeeded. Set the sqlite3_file.pMethods
+    ** pointer and, if the file is a main database file, link it into the
+    ** mutex protected linked list of all such files.  */
+    pFile->pMethods = &rbuvfs_io_methods;
+    if( flags & SQLITE_OPEN_MAIN_DB ){
+      sqlite3_mutex_enter(pRbuVfs->mutex);
+      pFd->pMainNext = pRbuVfs->pMain;
+      pRbuVfs->pMain = pFd;
+      sqlite3_mutex_leave(pRbuVfs->mutex);
+    }
+  }else{
+    sqlite3_free(pFd->zDel);
   }
-  pCsr->nChar = iOut;
 
-  ubrk_first(pCsr->pIter);
-  *ppCursor = (sqlite3_tokenizer_cursor *)pCsr;
-  return SQLITE_OK;
+  return rc;
 }
 
 /*
-** Close a tokenization cursor previously opened by a call to icuOpen().
+** Delete the file located at zPath.
 */
-static int icuClose(sqlite3_tokenizer_cursor *pCursor){
-  IcuCursor *pCsr = (IcuCursor *)pCursor;
-  ubrk_close(pCsr->pIter);
-  sqlite3_free(pCsr->zBuffer);
-  sqlite3_free(pCsr);
-  return SQLITE_OK;
+static int rbuVfsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xDelete(pRealVfs, zPath, dirSync);
 }
 
 /*
-** Extract the next token from a tokenization cursor.
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
 */
-static int icuNext(
-  sqlite3_tokenizer_cursor *pCursor,  /* Cursor returned by simpleOpen */
-  const char **ppToken,               /* OUT: *ppToken is the token text */
-  int *pnBytes,                       /* OUT: Number of bytes in token */
-  int *piStartOffset,                 /* OUT: Starting offset of token */
-  int *piEndOffset,                   /* OUT: Ending offset of token */
-  int *piPosition                     /* OUT: Position integer of token */
+static int rbuVfsAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
 ){
-  IcuCursor *pCsr = (IcuCursor *)pCursor;
-
-  int iStart = 0;
-  int iEnd = 0;
-  int nByte = 0;
-
-  while( iStart==iEnd ){
-    UChar32 c;
+  rbu_vfs *pRbuVfs = (rbu_vfs*)pVfs;
+  sqlite3_vfs *pRealVfs = pRbuVfs->pRealVfs;
+  int rc;
 
-    iStart = ubrk_current(pCsr->pIter);
-    iEnd = ubrk_next(pCsr->pIter);
-    if( iEnd==UBRK_DONE ){
-      return SQLITE_DONE;
-    }
+  rc = pRealVfs->xAccess(pRealVfs, zPath, flags, pResOut);
 
-    while( iStart<iEnd ){
-      int iWhite = iStart;
-      U16_NEXT(pCsr->aChar, iWhite, pCsr->nChar, c);
-      if( u_isspace(c) ){
-        iStart = iWhite;
+  /* If this call is to check if a *-wal file associated with an RBU target
+  ** database connection exists, and the RBU update is in RBU_STAGE_OAL,
+  ** the following special handling is activated:
+  **
+  **   a) if the *-wal file does exist, return SQLITE_CANTOPEN. This
+  **      ensures that the RBU extension never tries to update a database
+  **      in wal mode, even if the first page of the database file has
+  **      been damaged. 
+  **
+  **   b) if the *-wal file does not exist, claim that it does anyway,
+  **      causing SQLite to call xOpen() to open it. This call will also
+  **      be intercepted (see the rbuVfsOpen() function) and the *-oal
+  **      file opened instead.
+  */
+  if( rc==SQLITE_OK && flags==SQLITE_ACCESS_EXISTS ){
+    rbu_file *pDb = rbuFindMaindb(pRbuVfs, zPath);
+    if( pDb && pDb->pRbu && pDb->pRbu->eStage==RBU_STAGE_OAL ){
+      if( *pResOut ){
+        rc = SQLITE_CANTOPEN;
       }else{
-        break;
+        *pResOut = 1;
       }
     }
-    assert(iStart<=iEnd);
   }
 
-  do {
-    UErrorCode status = U_ZERO_ERROR;
-    if( nByte ){
-      char *zNew = sqlite3_realloc(pCsr->zBuffer, nByte);
-      if( !zNew ){
-        return SQLITE_NOMEM;
-      }
-      pCsr->zBuffer = zNew;
-      pCsr->nBuffer = nByte;
-    }
+  return rc;
+}
 
-    u_strToUTF8(
-        pCsr->zBuffer, pCsr->nBuffer, &nByte,    /* Output vars */
-        &pCsr->aChar[iStart], iEnd-iStart,       /* Input vars */
-        &status                                  /* Output success/failure */
-    );
-  } while( nByte>pCsr->nBuffer );
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (DEVSYM_MAX_PATHNAME+1) bytes.
+*/
+static int rbuVfsFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xFullPathname(pRealVfs, zPath, nOut, zOut);
+}
 
-  *ppToken = pCsr->zBuffer;
-  *pnBytes = nByte;
-  *piStartOffset = pCsr->aOffset[iStart];
-  *piEndOffset = pCsr->aOffset[iEnd];
-  *piPosition = pCsr->iToken++;
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *rbuVfsDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xDlOpen(pRealVfs, zPath);
+}
 
-  return SQLITE_OK;
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void rbuVfsDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  pRealVfs->xDlError(pRealVfs, nByte, zErrMsg);
 }
 
 /*
-** The set of routines that implement the simple tokenizer
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
 */
-static const sqlite3_tokenizer_module icuTokenizerModule = {
-  0,                           /* iVersion */
-  icuCreate,                   /* xCreate  */
-  icuDestroy,                  /* xCreate  */
-  icuOpen,                     /* xOpen    */
-  icuClose,                    /* xClose   */
-  icuNext,                     /* xNext    */
-};
+static void (*rbuVfsDlSym(
+  sqlite3_vfs *pVfs, 
+  void *pArg, 
+  const char *zSym
+))(void){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xDlSym(pRealVfs, pArg, zSym);
+}
 
 /*
-** Set *ppModule to point at the implementation of the ICU tokenizer.
+** Close the dynamic library handle pHandle.
 */
-SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(
-  sqlite3_tokenizer_module const**ppModule
-){
-  *ppModule = &icuTokenizerModule;
+static void rbuVfsDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  pRealVfs->xDlClose(pRealVfs, pHandle);
 }
+#endif /* SQLITE_OMIT_LOAD_EXTENSION */
 
-#endif /* defined(SQLITE_ENABLE_ICU) */
-#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int rbuVfsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xRandomness(pRealVfs, nByte, zBufOut);
+}
 
-/************** End of fts3_icu.c ********************************************/
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int rbuVfsSleep(sqlite3_vfs *pVfs, int nMicro){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xSleep(pRealVfs, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int rbuVfsCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  sqlite3_vfs *pRealVfs = ((rbu_vfs*)pVfs)->pRealVfs;
+  return pRealVfs->xCurrentTime(pRealVfs, pTimeOut);
+}
+
+/*
+** No-op.
+*/
+static int rbuVfsGetLastError(sqlite3_vfs *pVfs, int a, char *b){
+  return 0;
+}
+
+/*
+** Deregister and destroy an RBU vfs created by an earlier call to
+** sqlite3rbu_create_vfs().
+*/
+SQLITE_API void SQLITE_STDCALL sqlite3rbu_destroy_vfs(const char *zName){
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(zName);
+  if( pVfs && pVfs->xOpen==rbuVfsOpen ){
+    sqlite3_mutex_free(((rbu_vfs*)pVfs)->mutex);
+    sqlite3_vfs_unregister(pVfs);
+    sqlite3_free(pVfs);
+  }
+}
+
+/*
+** Create an RBU VFS named zName that accesses the underlying file-system
+** via existing VFS zParent. The new object is registered as a non-default
+** VFS with SQLite before returning.
+*/
+SQLITE_API int SQLITE_STDCALL sqlite3rbu_create_vfs(const char *zName, const char *zParent){
+
+  /* Template for VFS */
+  static sqlite3_vfs vfs_template = {
+    1,                            /* iVersion */
+    0,                            /* szOsFile */
+    0,                            /* mxPathname */
+    0,                            /* pNext */
+    0,                            /* zName */
+    0,                            /* pAppData */
+    rbuVfsOpen,                   /* xOpen */
+    rbuVfsDelete,                 /* xDelete */
+    rbuVfsAccess,                 /* xAccess */
+    rbuVfsFullPathname,           /* xFullPathname */
+
+#ifndef SQLITE_OMIT_LOAD_EXTENSION
+    rbuVfsDlOpen,                 /* xDlOpen */
+    rbuVfsDlError,                /* xDlError */
+    rbuVfsDlSym,                  /* xDlSym */
+    rbuVfsDlClose,                /* xDlClose */
+#else
+    0, 0, 0, 0,
+#endif
+
+    rbuVfsRandomness,             /* xRandomness */
+    rbuVfsSleep,                  /* xSleep */
+    rbuVfsCurrentTime,            /* xCurrentTime */
+    rbuVfsGetLastError,           /* xGetLastError */
+    0,                            /* xCurrentTimeInt64 (version 2) */
+    0, 0, 0                       /* Unimplemented version 3 methods */
+  };
+
+  rbu_vfs *pNew = 0;              /* Newly allocated VFS */
+  int nName;
+  int rc = SQLITE_OK;
+
+  int nByte;
+  nName = strlen(zName);
+  nByte = sizeof(rbu_vfs) + nName + 1;
+  pNew = (rbu_vfs*)sqlite3_malloc(nByte);
+  if( pNew==0 ){
+    rc = SQLITE_NOMEM;
+  }else{
+    sqlite3_vfs *pParent;           /* Parent VFS */
+    memset(pNew, 0, nByte);
+    pParent = sqlite3_vfs_find(zParent);
+    if( pParent==0 ){
+      rc = SQLITE_NOTFOUND;
+    }else{
+      char *zSpace;
+      memcpy(&pNew->base, &vfs_template, sizeof(sqlite3_vfs));
+      pNew->base.mxPathname = pParent->mxPathname;
+      pNew->base.szOsFile = sizeof(rbu_file) + pParent->szOsFile;
+      pNew->pRealVfs = pParent;
+      pNew->base.zName = (const char*)(zSpace = (char*)&pNew[1]);
+      memcpy(zSpace, zName, nName);
+
+      /* Allocate the mutex and register the new VFS (not as the default) */
+      pNew->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_RECURSIVE);
+      if( pNew->mutex==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        rc = sqlite3_vfs_register(&pNew->base, 0);
+      }
+    }
+
+    if( rc!=SQLITE_OK ){
+      sqlite3_mutex_free(pNew->mutex);
+      sqlite3_free(pNew);
+    }
+  }
+
+  return rc;
+}
+
+
+/**************************************************************************/
+
+#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_RBU) */
+
+/************** End of sqlite3rbu.c ******************************************/
 /************** Begin file dbstat.c ******************************************/
 /*
 ** 2010 July 12
@@ -155233,6 +160988,7 @@ SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(
 ** for an example implementation.
 */
 
+/* #include "sqliteInt.h"   ** Requires access to internal data structures ** */
 #if (defined(SQLITE_ENABLE_DBSTAT_VTAB) || defined(SQLITE_TEST)) \
     && !defined(SQLITE_OMIT_VIRTUALTABLE)
 
@@ -155835,7 +161591,7 @@ static int statRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
 /*
 ** Invoke this routine to register the "dbstat" virtual table module
 */
-SQLITE_API int SQLITE_STDCALL sqlite3_dbstat_register(sqlite3 *db){
+SQLITE_PRIVATE int sqlite3DbstatRegister(sqlite3 *db){
   static sqlite3_module dbstat_module = {
     0,                            /* iVersion */
     statConnect,                  /* xCreate */
@@ -155860,6 +161616,8 @@ SQLITE_API int SQLITE_STDCALL sqlite3_dbstat_register(sqlite3 *db){
   };
   return sqlite3_create_module(db, "dbstat", &dbstat_module, 0);
 }
+#elif defined(SQLITE_ENABLE_DBSTAT_VTAB)
+SQLITE_PRIVATE int sqlite3DbstatRegister(sqlite3 *db){ return SQLITE_OK; }
 #endif /* SQLITE_ENABLE_DBSTAT_VTAB */
 
 /************** End of dbstat.c **********************************************/
diff --git a/db/sqlite3/src/sqlite3.h b/db/sqlite3/src/sqlite3.h
index 023da28bd7b8a51478bc2be04f720fb79de0a809..d3f272c2b684b12c72322f27ca2d37f683df4b06 100644
--- a/db/sqlite3/src/sqlite3.h
+++ b/db/sqlite3/src/sqlite3.h
@@ -23,7 +23,7 @@
 **
 ** The official C-language API documentation for SQLite is derived
 ** from comments in this file.  This file is the authoritative source
-** on how SQLite interfaces are suppose to operate.
+** on how SQLite interfaces are supposed to operate.
 **
 ** The name of this file under configuration management is "sqlite.h.in".
 ** The makefile makes some minor changes to this file (such as inserting
@@ -111,9 +111,9 @@ extern "C" {
 ** [sqlite3_libversion_number()], [sqlite3_sourceid()],
 ** [sqlite_version()] and [sqlite_source_id()].
 */
-#define SQLITE_VERSION        "3.8.10.1"
-#define SQLITE_VERSION_NUMBER 3008010
-#define SQLITE_SOURCE_ID      "2015-05-09 12:14:55 05b4b1f2a937c06c90db70c09890038f6c98ec40"
+#define SQLITE_VERSION        "3.8.11.1"
+#define SQLITE_VERSION_NUMBER 3008011
+#define SQLITE_SOURCE_ID      "2015-07-29 20:00:57 cf538e2783e468bbc25e7cb2a9ee64d3e0e80b2f"
 
 /*
 ** CAPI3REF: Run-Time Library Version Numbers
@@ -963,6 +963,14 @@ struct sqlite3_io_methods {
 ** circumstances in order to fix a problem with priority inversion.
 ** Applications should <em>not</em> use this file-control.
 **
+** <li>[[SQLITE_FCNTL_ZIPVFS]]
+** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
+** VFS should return SQLITE_NOTFOUND for this opcode.
+**
+** <li>[[SQLITE_FCNTL_RBU]]
+** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
+** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
+** this opcode.  
 ** </ul>
 */
 #define SQLITE_FCNTL_LOCKSTATE               1
@@ -988,6 +996,8 @@ struct sqlite3_io_methods {
 #define SQLITE_FCNTL_COMMIT_PHASETWO        22
 #define SQLITE_FCNTL_WIN32_SET_HANDLE       23
 #define SQLITE_FCNTL_WAL_BLOCK              24
+#define SQLITE_FCNTL_ZIPVFS                 25
+#define SQLITE_FCNTL_RBU                    26
 
 /* deprecated names */
 #define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
@@ -3390,7 +3400,9 @@ SQLITE_API int SQLITE_STDCALL sqlite3_stmt_busy(sqlite3_stmt*);
 ** Some interfaces require a protected sqlite3_value.  Other interfaces
 ** will accept either a protected or an unprotected sqlite3_value.
 ** Every interface that accepts sqlite3_value arguments specifies
-** whether or not it requires a protected sqlite3_value.
+** whether or not it requires a protected sqlite3_value.  The
+** [sqlite3_value_dup()] interface can be used to construct a new 
+** protected sqlite3_value from an unprotected sqlite3_value.
 **
 ** The terms "protected" and "unprotected" refer to whether or not
 ** a mutex is held.  An internal mutex is held for a protected
@@ -3550,6 +3562,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_bind_text64(sqlite3_stmt*, int, const char
                          void(*)(void*), unsigned char encoding);
 SQLITE_API int SQLITE_STDCALL sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
 SQLITE_API int SQLITE_STDCALL sqlite3_bind_zeroblob(sqlite3_stmt*, int, int n);
+SQLITE_API int SQLITE_STDCALL sqlite3_bind_zeroblob64(sqlite3_stmt*, int, sqlite3_uint64);
 
 /*
 ** CAPI3REF: Number Of SQL Parameters
@@ -3893,8 +3906,6 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** KEYWORDS: {column access functions}
 ** METHOD: sqlite3_stmt
 **
-** These routines form the "result set" interface.
-**
 ** ^These routines return information about a single column of the current
 ** result row of a query.  ^In every case the first argument is a pointer
 ** to the [prepared statement] that is being evaluated (the [sqlite3_stmt*]
@@ -3954,13 +3965,14 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** even empty strings, are always zero-terminated.  ^The return
 ** value from sqlite3_column_blob() for a zero-length BLOB is a NULL pointer.
 **
-** ^The object returned by [sqlite3_column_value()] is an
-** [unprotected sqlite3_value] object.  An unprotected sqlite3_value object
-** may only be used with [sqlite3_bind_value()] and [sqlite3_result_value()].
+** <b>Warning:</b> ^The object returned by [sqlite3_column_value()] is an
+** [unprotected sqlite3_value] object.  In a multithreaded environment,
+** an unprotected sqlite3_value object may only be used safely with
+** [sqlite3_bind_value()] and [sqlite3_result_value()].
 ** If the [unprotected sqlite3_value] object returned by
 ** [sqlite3_column_value()] is used in any other way, including calls
 ** to routines like [sqlite3_value_int()], [sqlite3_value_text()],
-** or [sqlite3_value_bytes()], then the behavior is undefined.
+** or [sqlite3_value_bytes()], the behavior is not threadsafe.
 **
 ** These routines attempt to convert the value where appropriate.  ^For
 ** example, if the internal representation is FLOAT and a text result
@@ -3991,12 +4003,6 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** </table>
 ** </blockquote>)^
 **
-** The table above makes reference to standard C library functions atoi()
-** and atof().  SQLite does not really use these functions.  It has its
-** own equivalent internal routines.  The atoi() and atof() names are
-** used in the table for brevity and because they are familiar to most
-** C programmers.
-**
 ** Note that when type conversions occur, pointers returned by prior
 ** calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
 ** sqlite3_column_text16() may be invalidated.
@@ -4021,7 +4027,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** of conversion are done in place when it is possible, but sometimes they
 ** are not possible and in those cases prior pointers are invalidated.
 **
-** The safest and easiest to remember policy is to invoke these routines
+** The safest policy is to invoke these routines
 ** in one of the following ways:
 **
 ** <ul>
@@ -4041,7 +4047,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_data_count(sqlite3_stmt *pStmt);
 ** ^The pointers returned are valid until a type conversion occurs as
 ** described above, or until [sqlite3_step()] or [sqlite3_reset()] or
 ** [sqlite3_finalize()] is called.  ^The memory space used to hold strings
-** and BLOBs is freed automatically.  Do <b>not</b> pass the pointers returned
+** and BLOBs is freed automatically.  Do <em>not</em> pass the pointers returned
 ** from [sqlite3_column_blob()], [sqlite3_column_text()], etc. into
 ** [sqlite3_free()].
 **
@@ -4291,12 +4297,12 @@ SQLITE_API SQLITE_DEPRECATED int SQLITE_STDCALL sqlite3_memory_alarm(void(*)(voi
 #endif
 
 /*
-** CAPI3REF: Obtaining SQL Function Parameter Values
+** CAPI3REF: Obtaining SQL Values
 ** METHOD: sqlite3_value
 **
 ** The C-language implementation of SQL functions and aggregates uses
 ** this set of interface routines to access the parameter values on
-** the function or aggregate.
+** the function or aggregate.  
 **
 ** The xFunc (for scalar functions) or xStep (for aggregates) parameters
 ** to [sqlite3_create_function()] and [sqlite3_create_function16()]
@@ -4349,6 +4355,23 @@ SQLITE_API const void *SQLITE_STDCALL sqlite3_value_text16be(sqlite3_value*);
 SQLITE_API int SQLITE_STDCALL sqlite3_value_type(sqlite3_value*);
 SQLITE_API int SQLITE_STDCALL sqlite3_value_numeric_type(sqlite3_value*);
 
+/*
+** CAPI3REF: Copy And Free SQL Values
+** METHOD: sqlite3_value
+**
+** ^The sqlite3_value_dup(V) interface makes a copy of the [sqlite3_value]
+** object D and returns a pointer to that copy.  ^The [sqlite3_value] returned
+** is a [protected sqlite3_value] object even if the input is not.
+** ^The sqlite3_value_dup(V) interface returns NULL if V is NULL or if a
+** memory allocation fails.
+**
+** ^The sqlite3_value_free(V) interface frees an [sqlite3_value] object
+** previously obtained from [sqlite3_value_dup()].  ^If V is a NULL pointer
+** then sqlite3_value_free(V) is a harmless no-op.
+*/
+SQLITE_API SQLITE_EXPERIMENTAL sqlite3_value *SQLITE_STDCALL sqlite3_value_dup(const sqlite3_value*);
+SQLITE_API SQLITE_EXPERIMENTAL void SQLITE_STDCALL sqlite3_value_free(sqlite3_value*);
+
 /*
 ** CAPI3REF: Obtain Aggregate Function Context
 ** METHOD: sqlite3_context
@@ -4512,9 +4535,9 @@ typedef void (*sqlite3_destructor_type)(void*);
 ** to by the second parameter and which is N bytes long where N is the
 ** third parameter.
 **
-** ^The sqlite3_result_zeroblob() interfaces set the result of
-** the application-defined function to be a BLOB containing all zero
-** bytes and N bytes in size, where N is the value of the 2nd parameter.
+** ^The sqlite3_result_zeroblob(C,N) and sqlite3_result_zeroblob64(C,N)
+** interfaces set the result of the application-defined function to be
+** a BLOB containing all zero bytes and N bytes in size.
 **
 ** ^The sqlite3_result_double() interface sets the result from
 ** an application-defined function to be a floating point value specified
@@ -4596,7 +4619,7 @@ typedef void (*sqlite3_destructor_type)(void*);
 ** from [sqlite3_malloc()] before it returns.
 **
 ** ^The sqlite3_result_value() interface sets the result of
-** the application-defined function to be a copy the
+** the application-defined function to be a copy of the
 ** [unprotected sqlite3_value] object specified by the 2nd parameter.  ^The
 ** sqlite3_result_value() interface makes a copy of the [sqlite3_value]
 ** so that the [sqlite3_value] specified in the parameter may change or
@@ -4629,6 +4652,7 @@ SQLITE_API void SQLITE_STDCALL sqlite3_result_text16le(sqlite3_context*, const v
 SQLITE_API void SQLITE_STDCALL sqlite3_result_text16be(sqlite3_context*, const void*, int,void(*)(void*));
 SQLITE_API void SQLITE_STDCALL sqlite3_result_value(sqlite3_context*, sqlite3_value*);
 SQLITE_API void SQLITE_STDCALL sqlite3_result_zeroblob(sqlite3_context*, int n);
+SQLITE_API int SQLITE_STDCALL sqlite3_result_zeroblob64(sqlite3_context*, sqlite3_uint64 n);
 
 /*
 ** CAPI3REF: Define New Collating Sequences
@@ -5872,7 +5896,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_blob_open(
 **
 ** ^This function sets the database handle error code and message.
 */
-SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_blob_reopen(sqlite3_blob *, sqlite3_int64);
+SQLITE_API int SQLITE_STDCALL sqlite3_blob_reopen(sqlite3_blob *, sqlite3_int64);
 
 /*
 ** CAPI3REF: Close A BLOB Handle
@@ -6269,6 +6293,9 @@ SQLITE_API int SQLITE_STDCALL sqlite3_mutex_notheld(sqlite3_mutex*);
 #define SQLITE_MUTEX_STATIC_APP1      8  /* For use by application */
 #define SQLITE_MUTEX_STATIC_APP2      9  /* For use by application */
 #define SQLITE_MUTEX_STATIC_APP3     10  /* For use by application */
+#define SQLITE_MUTEX_STATIC_VFS1     11  /* For use by built-in VFS */
+#define SQLITE_MUTEX_STATIC_VFS2     12  /* For use by extension VFS */
+#define SQLITE_MUTEX_STATIC_VFS3     13  /* For use by application VFS */
 
 /*
 ** CAPI3REF: Retrieve the mutex for a database connection
@@ -7682,7 +7709,7 @@ SQLITE_API int SQLITE_STDCALL sqlite3_vtab_on_conflict(sqlite3 *);
 **
 ** See also: [sqlite3_stmt_scanstatus_reset()]
 */
-SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_stmt_scanstatus(
+SQLITE_API int SQLITE_STDCALL sqlite3_stmt_scanstatus(
   sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
   int idx,                  /* Index of loop to report on */
   int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
@@ -7698,7 +7725,7 @@ SQLITE_API SQLITE_EXPERIMENTAL int SQLITE_STDCALL sqlite3_stmt_scanstatus(
 ** This API is only available if the library is built with pre-processor
 ** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.
 */
-SQLITE_API SQLITE_EXPERIMENTAL void SQLITE_STDCALL sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);
+SQLITE_API void SQLITE_STDCALL sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);
 
 
 /*
@@ -7813,6 +7840,8 @@ struct sqlite3_rtree_query_info {
   int eParentWithin;                /* Visibility of parent node */
   int eWithin;                      /* OUT: Visiblity */
   sqlite3_rtree_dbl rScore;         /* OUT: Write the score here */
+  /* The following fields are only available in 3.8.11 and later */
+  sqlite3_value **apSqlParam;       /* Original SQL values of parameters */
 };
 
 /*