SQLite Android Bindings

/******************************************************************************
** This file is an amalgamation of many separate C source files from SQLite
** version 3.21.0.  By combining all the individual C code files into this
** version 3.22.0.  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
** of 5% or more are commonly seen when SQLite is compiled as a single
** translation unit.
**
** This file is all you need to compile SQLite.  To use SQLite in other

** been edited in any way since it was last checked in, then the last
** four hexadecimal digits of the hash may be modified.
**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.21.0"
#define SQLITE_VERSION_NUMBER 3021000
#define SQLITE_SOURCE_ID      "2017-10-24 18:55:49 1a584e499906b5c87ec7d43d4abce641fdf017c42125b083109bc77c4de48827"
#define SQLITE_VERSION        "3.22.0"
#define SQLITE_VERSION_NUMBER 3022000
#define SQLITE_SOURCE_ID      "2018-01-22 18:45:57 0c55d179733b46d8d0ba4d88e01a25e10677046ee3da1d5b1581e86726f2171d"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros

** support for additional result codes that provide more detailed information
** about errors. These [extended result codes] are enabled or disabled
** on a per database connection basis using the
** [sqlite3_extended_result_codes()] API.  Or, the extended code for
** the most recent error can be obtained using
** [sqlite3_extended_errcode()].
*/
#define SQLITE_ERROR_MISSING_COLLSEQ   (SQLITE_ERROR | (1<<8))
#define SQLITE_ERROR_RETRY             (SQLITE_ERROR | (2<<8))
#define SQLITE_IOERR_READ              (SQLITE_IOERR | (1<<8))
#define SQLITE_IOERR_SHORT_READ        (SQLITE_IOERR | (2<<8))
#define SQLITE_IOERR_WRITE             (SQLITE_IOERR | (3<<8))
#define SQLITE_IOERR_FSYNC             (SQLITE_IOERR | (4<<8))
#define SQLITE_IOERR_DIR_FSYNC         (SQLITE_IOERR | (5<<8))
#define SQLITE_IOERR_TRUNCATE          (SQLITE_IOERR | (6<<8))
#define SQLITE_IOERR_FSTAT             (SQLITE_IOERR | (7<<8))

#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
#define SQLITE_CANTOPEN_CONVPATH       (SQLITE_CANTOPEN | (4<<8))
#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))
#define SQLITE_READONLY_CANTLOCK       (SQLITE_READONLY | (2<<8))
#define SQLITE_READONLY_ROLLBACK       (SQLITE_READONLY | (3<<8))
#define SQLITE_READONLY_DBMOVED        (SQLITE_READONLY | (4<<8))
#define SQLITE_READONLY_CANTINIT       (SQLITE_READONLY | (5<<8))
#define SQLITE_READONLY_DIRECTORY      (SQLITE_READONLY | (6<<8))
#define SQLITE_ABORT_ROLLBACK          (SQLITE_ABORT | (2<<8))
#define SQLITE_CONSTRAINT_CHECK        (SQLITE_CONSTRAINT | (1<<8))
#define SQLITE_CONSTRAINT_COMMITHOOK   (SQLITE_CONSTRAINT | (2<<8))
#define SQLITE_CONSTRAINT_FOREIGNKEY   (SQLITE_CONSTRAINT | (3<<8))
#define SQLITE_CONSTRAINT_FUNCTION     (SQLITE_CONSTRAINT | (4<<8))
#define SQLITE_CONSTRAINT_NOTNULL      (SQLITE_CONSTRAINT | (5<<8))
#define SQLITE_CONSTRAINT_PRIMARYKEY   (SQLITE_CONSTRAINT | (6<<8))

** CAPI3REF: OS Interface Object
**
** An instance of the sqlite3_vfs object defines the interface between
** the SQLite core and the underlying operating system.  The "vfs"
** in the name of the object stands for "virtual file system".  See
** the [VFS | VFS documentation] for further information.
**
** The VFS interface is sometimes extended by adding new methods onto
** The value of the iVersion field is initially 1 but may be larger in
** future versions of SQLite.  Additional fields may be appended to this
** object when the iVersion value is increased.  Note that the structure
** of the sqlite3_vfs object changes in the transaction between
** SQLite version 3.5.9 and 3.6.0 and yet the iVersion field was not
** the end.  Each time such an extension occurs, the iVersion field
** is incremented.  The iVersion value started out as 1 in
** SQLite [version 3.5.0] on [dateof:3.5.0], then increased to 2
** with SQLite [version 3.7.0] on [dateof:3.7.0], and then increased
** to 3 with SQLite [version 3.7.6] on [dateof:3.7.6].  Additional fields
** may be appended to the sqlite3_vfs object and the iVersion value
** may increase again in future versions of SQLite.
** Note that the structure
** of the sqlite3_vfs object changes in the transition from
** SQLite [version 3.5.9] to [version 3.6.0] on [dateof:3.6.0]
** and yet the iVersion field was not modified.
** modified.
**
** The szOsFile field is the size of the subclassed [sqlite3_file]
** structure used by this VFS.  mxPathname is the maximum length of
** a pathname in this VFS.
**
** Registered sqlite3_vfs objects are kept on a linked list formed by
** the pNext pointer.  The [sqlite3_vfs_register()]

** operation before closing the connection. This option may be used to
** override this behaviour. The first parameter passed to this operation
** is an integer - non-zero to disable checkpoints-on-close, or zero (the
** default) to enable them. The second parameter is a pointer to an integer
** into which is written 0 or 1 to indicate whether checkpoints-on-close
** have been disabled - 0 if they are not disabled, 1 if they are.
** </dd>
**
** <dt>SQLITE_DBCONFIG_ENABLE_QPSG</dt>
** <dd>^(The SQLITE_DBCONFIG_ENABLE_QPSG option activates or deactivates
** the [query planner stability guarantee] (QPSG).  When the QPSG is active,
** a single SQL query statement will always use the same algorithm regardless
** of values of [bound parameters].)^ The QPSG disables some query optimizations
** that look at the values of bound parameters, which can make some queries
** slower.  But the QPSG has the advantage of more predictable behavior.  With
** the QPSG active, SQLite will always use the same query plan in the field as
** was used during testing in the lab.
** </dd>
** <dt>SQLITE_DBCONFIG_TRIGGER_EQP</dt>
** <dd> By default, the output of EXPLAIN QUERY PLAN commands does not 
** include output for any operations performed by trigger programs. This
** option is used to set or clear (the default) a flag that governs this
** behavior. The first parameter passed to this operation is an integer -
** non-zero to enable output for trigger programs, or zero to disable it.
** The second parameter is a pointer to an integer into which is written 
** 0 or 1 to indicate whether output-for-triggers has been disabled - 0 if 
** it is not disabled, 1 if it is.  
**
** </dd>
** </dl>
*/
#define SQLITE_DBCONFIG_MAINDBNAME            1000 /* const char* */
#define SQLITE_DBCONFIG_LOOKASIDE             1001 /* void* int int */
#define SQLITE_DBCONFIG_ENABLE_FKEY           1002 /* int int* */
#define SQLITE_DBCONFIG_ENABLE_TRIGGER        1003 /* int int* */
#define SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER 1004 /* int int* */
#define SQLITE_DBCONFIG_ENABLE_LOAD_EXTENSION 1005 /* int int* */
#define SQLITE_DBCONFIG_NO_CKPT_ON_CLOSE      1006 /* int int* */
#define SQLITE_DBCONFIG_ENABLE_QPSG           1007 /* int int* */

#define SQLITE_DBCONFIG_TRIGGER_EQP           1008 /* int int* */
#define SQLITE_DBCONFIG_MAX                   1008 /* Largest DBCONFIG */

/*
** CAPI3REF: Enable Or Disable Extended Result Codes
** METHOD: sqlite3
**
** ^The sqlite3_extended_result_codes() routine enables or disables the
** [extended result codes] feature of SQLite. ^The extended result

   void(*xProfile)(void*,const char*,sqlite3_uint64), void*);

/*
** CAPI3REF: SQL Trace Event Codes
** KEYWORDS: SQLITE_TRACE
**
** These constants identify classes of events that can be monitored
** using the [sqlite3_trace_v2()] tracing logic.  The third argument
** to [sqlite3_trace_v2()] is an OR-ed combination of one or more of
** using the [sqlite3_trace_v2()] tracing logic.  The M argument
** to [sqlite3_trace_v2(D,M,X,P)] is an OR-ed combination of one or more of
** the following constants.  ^The first argument to the trace callback
** is one of the following constants.
**
** New tracing constants may be added in future releases.
**
** ^A trace callback has four arguments: xCallback(T,C,P,X).
** ^The T argument is one of the integer type codes above.

** <tr><td><b>sqlite3_value_bytes16&nbsp;&nbsp;</b>
** <td>&rarr;&nbsp;&nbsp;<td>Size of UTF-16
** TEXT in bytes
** <tr><td><b>sqlite3_value_type</b><td>&rarr;<td>Default
** datatype of the value
** <tr><td><b>sqlite3_value_numeric_type&nbsp;&nbsp;</b>
** <td>&rarr;&nbsp;&nbsp;<td>Best numeric datatype of the value
** <tr><td><b>sqlite3_value_nochange&nbsp;&nbsp;</b>
** <td>&rarr;&nbsp;&nbsp;<td>True if the column is unchanged in an UPDATE
** against a virtual table.
** </table></blockquote>
**
** <b>Details:</b>
**
** These routines extract type, size, and content information from
** [protected sqlite3_value] objects.  Protected sqlite3_value objects
** are used to pass parameter information into implementation of

** ^(The sqlite3_value_numeric_type() interface attempts to apply
** numeric affinity to the value.  This means that an attempt is
** made to convert the value to an integer or floating point.  If
** such a conversion is possible without loss of information (in other
** words, if the value is a string that looks like a number)
** then the conversion is performed.  Otherwise no conversion occurs.
** The [SQLITE_INTEGER | datatype] after conversion is returned.)^
**
** ^Within the [xUpdate] method of a [virtual table], the
** sqlite3_value_nochange(X) interface returns true if and only if
** the column corresponding to X is unchanged by the UPDATE operation
** that the xUpdate method call was invoked to implement and if
** and the prior [xColumn] method call that was invoked to extracted
** the value for that column returned without setting a result (probably
** because it queried [sqlite3_vtab_nochange()] and found that the column
** was unchanging).  ^Within an [xUpdate] method, any value for which
** sqlite3_value_nochange(X) is true will in all other respects appear
** to be a NULL value.  If sqlite3_value_nochange(X) is invoked anywhere other
** than within an [xUpdate] method call for an UPDATE statement, then
** the return value is arbitrary and meaningless.
**
** Please pay particular attention to the fact that the pointer returned
** from [sqlite3_value_blob()], [sqlite3_value_text()], or
** [sqlite3_value_text16()] can be invalidated by a subsequent call to
** [sqlite3_value_bytes()], [sqlite3_value_bytes16()], [sqlite3_value_text()],
** or [sqlite3_value_text16()].
**

SQLITE_API const void *sqlite3_value_text16(sqlite3_value*);
SQLITE_API const void *sqlite3_value_text16le(sqlite3_value*);
SQLITE_API const void *sqlite3_value_text16be(sqlite3_value*);
SQLITE_API int sqlite3_value_bytes(sqlite3_value*);
SQLITE_API int sqlite3_value_bytes16(sqlite3_value*);
SQLITE_API int sqlite3_value_type(sqlite3_value*);
SQLITE_API int sqlite3_value_numeric_type(sqlite3_value*);
SQLITE_API int sqlite3_value_nochange(sqlite3_value*);

/*
** CAPI3REF: Finding The Subtype Of SQL Values
** METHOD: sqlite3_value
**
** The sqlite3_value_subtype(V) function returns the subtype for
** an [application-defined SQL function] argument V.  The subtype

** ^A NULL pointer can be used in place of "main" to refer to the
** main database file.
** ^The third and fourth parameters to this routine
** are passed directly through to the second and third parameters of
** the xFileControl method.  ^The return value of the xFileControl
** method becomes the return value of this routine.
**
** ^The SQLITE_FCNTL_FILE_POINTER value for the op parameter causes
** ^The [SQLITE_FCNTL_FILE_POINTER] value for the op parameter causes
** a pointer to the underlying [sqlite3_file] object to be written into
** the space pointed to by the 4th parameter.  ^The SQLITE_FCNTL_FILE_POINTER
** the space pointed to by the 4th parameter.  ^The [SQLITE_FCNTL_FILE_POINTER]
** case is a short-circuit path which does not actually invoke the
** underlying sqlite3_io_methods.xFileControl method.
**
** ^If the second parameter (zDbName) does not match the name of any
** open database file, then SQLITE_ERROR is returned.  ^This error
** code is not remembered and will not be recalled by [sqlite3_errcode()]
** or [sqlite3_errmsg()].  The underlying xFileControl method might
** also return SQLITE_ERROR.  There is no way to distinguish between
** an incorrect zDbName and an SQLITE_ERROR return from the underlying
** xFileControl method.
**
** See also: [SQLITE_FCNTL_LOCKSTATE]
** See also: [file control opcodes]
*/
SQLITE_API int sqlite3_file_control(sqlite3*, const char *zDbName, int op, void*);

/*
** CAPI3REF: Testing Interface
**
** ^The sqlite3_test_control() interface is used to read out internal

#define SQLITE_TESTCTRL_ONCE_RESET_THRESHOLD    19
#define SQLITE_TESTCTRL_NEVER_CORRUPT           20
#define SQLITE_TESTCTRL_VDBE_COVERAGE           21
#define SQLITE_TESTCTRL_BYTEORDER               22
#define SQLITE_TESTCTRL_ISINIT                  23
#define SQLITE_TESTCTRL_SORTER_MMAP             24
#define SQLITE_TESTCTRL_IMPOSTER                25
#define SQLITE_TESTCTRL_PARSER_COVERAGE         26
#define SQLITE_TESTCTRL_LAST                    25
#define SQLITE_TESTCTRL_LAST                    26  /* Largest TESTCTRL */

/*
** CAPI3REF: SQLite Runtime Status
**
** ^These interfaces are used to retrieve runtime status information
** about the performance of SQLite, and optionally to reset various
** highwater marks.  ^The first argument is an integer code for

** value returned is one of [SQLITE_ROLLBACK], [SQLITE_IGNORE], [SQLITE_FAIL],
** [SQLITE_ABORT], or [SQLITE_REPLACE], according to the [ON CONFLICT] mode
** of the SQL statement that triggered the call to the [xUpdate] method of the
** [virtual table].
*/
SQLITE_API int sqlite3_vtab_on_conflict(sqlite3 *);

/*
** CAPI3REF: Determine If Virtual Table Column Access Is For UPDATE
**
** If the sqlite3_vtab_nochange(X) routine is called within the [xColumn]
** method of a [virtual table], then it returns true if and only if the
** column is being fetched as part of an UPDATE operation during which the
** column value will not change.  Applications might use this to substitute
** a lighter-weight value to return that the corresponding [xUpdate] method
** understands as a "no-change" value.
**
** If the [xColumn] method calls sqlite3_vtab_nochange() and finds that
** the column is not changed by the UPDATE statement, they the xColumn
** method can optionally return without setting a result, without calling
** any of the [sqlite3_result_int|sqlite3_result_xxxxx() interfaces].
** In that case, [sqlite3_value_nochange(X)] will return true for the
** same column in the [xUpdate] method.
*/
SQLITE_API int sqlite3_vtab_nochange(sqlite3_context*);

/*
** CAPI3REF: Determine The Collation For a Virtual Table Constraint
**
** This function may only be called from within a call to the [xBestIndex]
** method of a [virtual table]. 
**
** The first argument must be the sqlite3_index_info object that is the
** first parameter to the xBestIndex() method. The second argument must be
** an index into the aConstraint[] array belonging to the sqlite3_index_info
** structure passed to xBestIndex. This function returns a pointer to a buffer 
** containing the name of the collation sequence for the corresponding
** constraint.
*/
SQLITE_API SQLITE_EXPERIMENTAL const char *sqlite3_vtab_collation(sqlite3_index_info*,int);

/*
** CAPI3REF: Conflict resolution modes
** KEYWORDS: {conflict resolution mode}
**
** These constants are returned by [sqlite3_vtab_on_conflict()] to
** inform a [virtual table] implementation what the [ON CONFLICT] mode
** is for the SQL statement being evaluated.

** no changes will be recorded in either of these scenarios.
**
** Changes are not recorded for individual rows that have NULL values stored
** in one or more of their PRIMARY KEY columns.
**
** SQLITE_OK is returned if the call completes without error. Or, if an error 
** occurs, an SQLite error code (e.g. SQLITE_NOMEM) is returned.
**
** <h3>Special sqlite_stat1 Handling</h3>
**
** As of SQLite version 3.22.0, the "sqlite_stat1" table is an exception to 
** some of the rules above. In SQLite, the schema of sqlite_stat1 is:
**  <pre>
**  &nbsp;     CREATE TABLE sqlite_stat1(tbl,idx,stat)  
**  </pre>
**
** Even though sqlite_stat1 does not have a PRIMARY KEY, changes are 
** recorded for it as if the PRIMARY KEY is (tbl,idx). Additionally, changes 
** are recorded for rows for which (idx IS NULL) is true. However, for such
** rows a zero-length blob (SQL value X'') is stored in the changeset or
** patchset instead of a NULL value. This allows such changesets to be
** manipulated by legacy implementations of sqlite3changeset_invert(),
** concat() and similar.
**
** The sqlite3changeset_apply() function automatically converts the 
** zero-length blob back to a NULL value when updating the sqlite_stat1
** table. However, if the application calls sqlite3changeset_new(),
** sqlite3changeset_old() or sqlite3changeset_conflict on a changeset 
** iterator directly (including on a changeset iterator passed to a
** conflict-handler callback) then the X'' value is returned. The application
** must translate X'' to NULL itself if required.
**
** Legacy (older than 3.22.0) versions of the sessions module cannot capture
** changes made to the sqlite_stat1 table. Legacy versions of the
** sqlite3changeset_apply() function silently ignore any modifications to the
** sqlite_stat1 table that are part of a changeset or patchset.
*/
SQLITE_API int sqlite3session_attach(
  sqlite3_session *pSession,      /* Session object */
  const char *zTab                /* Table name */
);

/*

typedef struct Bitvec Bitvec;
typedef struct CollSeq CollSeq;
typedef struct Column Column;
typedef struct Db Db;
typedef struct Schema Schema;
typedef struct Expr Expr;
typedef struct ExprList ExprList;
typedef struct ExprSpan ExprSpan;
typedef struct FKey FKey;
typedef struct FuncDestructor FuncDestructor;
typedef struct FuncDef FuncDef;
typedef struct FuncDefHash FuncDefHash;
typedef struct IdList IdList;
typedef struct Index Index;
typedef struct IndexSample IndexSample;

                       int flags, int seekResult);
SQLITE_PRIVATE int sqlite3BtreeFirst(BtCursor*, int *pRes);
SQLITE_PRIVATE int sqlite3BtreeLast(BtCursor*, int *pRes);
SQLITE_PRIVATE int sqlite3BtreeNext(BtCursor*, int flags);
SQLITE_PRIVATE int sqlite3BtreeEof(BtCursor*);
SQLITE_PRIVATE int sqlite3BtreePrevious(BtCursor*, int flags);
SQLITE_PRIVATE i64 sqlite3BtreeIntegerKey(BtCursor*);
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
SQLITE_PRIVATE i64 sqlite3BtreeOffset(BtCursor*);
#endif
SQLITE_PRIVATE int sqlite3BtreePayload(BtCursor*, u32 offset, u32 amt, void*);
SQLITE_PRIVATE const void *sqlite3BtreePayloadFetch(BtCursor*, u32 *pAmt);
SQLITE_PRIVATE u32 sqlite3BtreePayloadSize(BtCursor*);

SQLITE_PRIVATE char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot, int, int*);
SQLITE_PRIVATE struct Pager *sqlite3BtreePager(Btree*);
SQLITE_PRIVATE i64 sqlite3BtreeRowCountEst(BtCursor*);

#define P4_EXPR       (-10) /* P4 is a pointer to an Expr tree */
#define P4_MEM        (-11) /* P4 is a pointer to a Mem*    structure */
#define P4_VTAB       (-12) /* P4 is a pointer to an sqlite3_vtab structure */
#define P4_REAL       (-13) /* P4 is a 64-bit floating point value */
#define P4_INT64      (-14) /* P4 is a 64-bit signed integer */
#define P4_INTARRAY   (-15) /* P4 is a vector of 32-bit integers */
#define P4_FUNCCTX    (-16) /* P4 is a pointer to an sqlite3_context object */
#define P4_DYNBLOB    (-17) /* Pointer to memory from sqliteMalloc() */

/* Error message codes for OP_Halt */
#define P5_ConstraintNotNull 1
#define P5_ConstraintUnique  2
#define P5_ConstraintCheck   3
#define P5_ConstraintFK      4

#define OP_Subtract       89 /* same as TK_MINUS, synopsis: r[P3]=r[P2]-r[P1] */
#define OP_Multiply       90 /* same as TK_STAR, synopsis: r[P3]=r[P1]*r[P2] */
#define OP_Divide         91 /* same as TK_SLASH, synopsis: r[P3]=r[P2]/r[P1] */
#define OP_Remainder      92 /* same as TK_REM, synopsis: r[P3]=r[P2]%r[P1] */
#define OP_Concat         93 /* same as TK_CONCAT, synopsis: r[P3]=r[P2]+r[P1] */
#define OP_Compare        94 /* synopsis: r[P1@P3] <-> r[P2@P3]            */
#define OP_BitNot         95 /* same as TK_BITNOT, synopsis: r[P1]= ~r[P1] */
#define OP_Column         96 /* synopsis: r[P3]=PX                         */
#define OP_Offset         96 /* synopsis: r[P3] = sqlite_offset(P1)        */
#define OP_String8        97 /* same as TK_STRING, synopsis: r[P2]='P4'    */
#define OP_Column         98 /* synopsis: r[P3]=PX                         */
#define OP_Affinity       98 /* synopsis: affinity(r[P1@P2])               */
#define OP_MakeRecord     99 /* synopsis: r[P3]=mkrec(r[P1@P2])            */
#define OP_Count         100 /* synopsis: r[P2]=count()                    */
#define OP_ReadCookie    101
#define OP_SetCookie     102
#define OP_ReopenIdx     103 /* synopsis: root=P2 iDb=P3                   */
#define OP_OpenRead      104 /* synopsis: root=P2 iDb=P3                   */
#define OP_OpenWrite     105 /* synopsis: root=P2 iDb=P3                   */
#define OP_OpenDup       106
#define OP_OpenAutoindex 107 /* synopsis: nColumn=P2                       */
#define OP_OpenEphemeral 108 /* synopsis: nColumn=P2                       */
#define OP_SorterOpen    109
#define OP_SequenceTest  110 /* synopsis: if( cursor[P1].ctr++ ) pc = P2   */
#define OP_OpenPseudo    111 /* synopsis: P3 columns in r[P2]              */
#define OP_Close         112
#define OP_ColumnsUsed   113
#define OP_Sequence      114 /* synopsis: r[P2]=cursor[P1].ctr++           */
#define OP_NewRowid      115 /* synopsis: r[P2]=rowid                      */
#define OP_Insert        116 /* synopsis: intkey=r[P3] data=r[P2]          */
#define OP_InsertInt     117 /* synopsis: intkey=P3 data=r[P2]             */
#define OP_Delete        118
#define OP_ResetCount    119
#define OP_SorterCompare 120 /* synopsis: if key(P1)!=trim(r[P3],P4) goto P2 */
#define OP_SorterData    121 /* synopsis: r[P2]=data                       */
#define OP_RowData       122 /* synopsis: r[P2]=data                       */
#define OP_Rowid         123 /* synopsis: r[P2]=rowid                      */
#define OP_NullRow       124
#define OP_SeekEnd       125
#define OP_SorterInsert  126 /* synopsis: key=r[P2]                        */
#define OP_IdxInsert     127 /* synopsis: key=r[P2]                        */
#define OP_IdxDelete     128 /* synopsis: key=r[P2@P3]                     */
#define OP_DeferredSeek  129 /* synopsis: Move P3 to P1.rowid if needed    */
#define OP_IdxRowid      130 /* synopsis: r[P2]=rowid                      */
#define OP_Affinity       99 /* synopsis: affinity(r[P1@P2])               */
#define OP_MakeRecord    100 /* synopsis: r[P3]=mkrec(r[P1@P2])            */
#define OP_Count         101 /* synopsis: r[P2]=count()                    */
#define OP_ReadCookie    102
#define OP_SetCookie     103
#define OP_ReopenIdx     104 /* synopsis: root=P2 iDb=P3                   */
#define OP_OpenRead      105 /* synopsis: root=P2 iDb=P3                   */
#define OP_OpenWrite     106 /* synopsis: root=P2 iDb=P3                   */
#define OP_OpenDup       107
#define OP_OpenAutoindex 108 /* synopsis: nColumn=P2                       */
#define OP_OpenEphemeral 109 /* synopsis: nColumn=P2                       */
#define OP_SorterOpen    110
#define OP_SequenceTest  111 /* synopsis: if( cursor[P1].ctr++ ) pc = P2   */
#define OP_OpenPseudo    112 /* synopsis: P3 columns in r[P2]              */
#define OP_Close         113
#define OP_ColumnsUsed   114
#define OP_Sequence      115 /* synopsis: r[P2]=cursor[P1].ctr++           */
#define OP_NewRowid      116 /* synopsis: r[P2]=rowid                      */
#define OP_Insert        117 /* synopsis: intkey=r[P3] data=r[P2]          */
#define OP_InsertInt     118 /* synopsis: intkey=P3 data=r[P2]             */
#define OP_Delete        119
#define OP_ResetCount    120
#define OP_SorterCompare 121 /* synopsis: if key(P1)!=trim(r[P3],P4) goto P2 */
#define OP_SorterData    122 /* synopsis: r[P2]=data                       */
#define OP_RowData       123 /* synopsis: r[P2]=data                       */
#define OP_Rowid         124 /* synopsis: r[P2]=rowid                      */
#define OP_NullRow       125
#define OP_SeekEnd       126
#define OP_SorterInsert  127 /* synopsis: key=r[P2]                        */
#define OP_IdxInsert     128 /* synopsis: key=r[P2]                        */
#define OP_IdxDelete     129 /* synopsis: key=r[P2@P3]                     */
#define OP_DeferredSeek  130 /* synopsis: Move P3 to P1.rowid if needed    */
#define OP_IdxRowid      131 /* synopsis: r[P2]=rowid                      */
#define OP_Destroy       131
#define OP_Real          132 /* same as TK_FLOAT, synopsis: r[P2]=P4       */
#define OP_Destroy       133
#define OP_Clear         133
#define OP_ResetSorter   134
#define OP_CreateBtree   135 /* synopsis: r[P2]=root iDb=P1 flags=P3       */
#define OP_SqlExec       136
#define OP_ParseSchema   137
#define OP_LoadAnalysis  138
#define OP_DropTable     139
#define OP_DropIndex     140
#define OP_DropTrigger   141
#define OP_IntegrityCk   142
#define OP_RowSetAdd     143 /* synopsis: rowset(P1)=r[P2]                 */
#define OP_Param         144
#define OP_FkCounter     145 /* synopsis: fkctr[P1]+=P2                    */
#define OP_MemMax        146 /* synopsis: r[P1]=max(r[P1],r[P2])           */
#define OP_OffsetLimit   147 /* synopsis: if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1) */
#define OP_AggStep0      148 /* synopsis: accum=r[P3] step(r[P2@P5])       */
#define OP_AggStep       149 /* synopsis: accum=r[P3] step(r[P2@P5])       */
#define OP_AggFinal      150 /* synopsis: accum=r[P1] N=P2                 */
#define OP_Expire        151
#define OP_TableLock     152 /* synopsis: iDb=P1 root=P2 write=P3          */
#define OP_VBegin        153
#define OP_VCreate       154
#define OP_VDestroy      155
#define OP_VOpen         156
#define OP_VColumn       157 /* synopsis: r[P3]=vcolumn(P2)                */
#define OP_VRename       158
#define OP_Pagecount     159
#define OP_MaxPgcnt      160
#define OP_PureFunc0     161
#define OP_Function0     162 /* synopsis: r[P3]=func(r[P2@P5])             */
#define OP_PureFunc      163
#define OP_Function      164 /* synopsis: r[P3]=func(r[P2@P5])             */
#define OP_CursorHint    165
#define OP_Noop          166
#define OP_Explain       167
#define OP_Clear         134
#define OP_ResetSorter   135
#define OP_CreateBtree   136 /* synopsis: r[P2]=root iDb=P1 flags=P3       */
#define OP_SqlExec       137
#define OP_ParseSchema   138
#define OP_LoadAnalysis  139
#define OP_DropTable     140
#define OP_DropIndex     141
#define OP_DropTrigger   142
#define OP_IntegrityCk   143
#define OP_RowSetAdd     144 /* synopsis: rowset(P1)=r[P2]                 */
#define OP_Param         145
#define OP_FkCounter     146 /* synopsis: fkctr[P1]+=P2                    */
#define OP_MemMax        147 /* synopsis: r[P1]=max(r[P1],r[P2])           */
#define OP_OffsetLimit   148 /* synopsis: if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1) */
#define OP_AggStep0      149 /* synopsis: accum=r[P3] step(r[P2@P5])       */
#define OP_AggStep       150 /* synopsis: accum=r[P3] step(r[P2@P5])       */
#define OP_AggFinal      151 /* synopsis: accum=r[P1] N=P2                 */
#define OP_Expire        152
#define OP_TableLock     153 /* synopsis: iDb=P1 root=P2 write=P3          */
#define OP_VBegin        154
#define OP_VCreate       155
#define OP_VDestroy      156
#define OP_VOpen         157
#define OP_VColumn       158 /* synopsis: r[P3]=vcolumn(P2)                */
#define OP_VRename       159
#define OP_Pagecount     160
#define OP_MaxPgcnt      161
#define OP_PureFunc0     162
#define OP_Function0     163 /* synopsis: r[P3]=func(r[P2@P5])             */
#define OP_PureFunc      164
#define OP_Function      165 /* synopsis: r[P3]=func(r[P2@P5])             */
#define OP_Trace         166
#define OP_CursorHint    167
#define OP_Noop          168
#define OP_Explain       169

/* Properties such as "out2" or "jump" that are specified in
** comments following the "case" for each opcode in the vdbe.c
** are encoded into bitvectors as follows:
*/
#define OPFLG_JUMP        0x01  /* jump:  P2 holds jmp target */
#define OPFLG_IN1         0x02  /* in1:   P1 is an input */

/*  40 */ 0x01, 0x01, 0x23, 0x26, 0x26, 0x0b, 0x01, 0x01,\
/*  48 */ 0x03, 0x03, 0x03, 0x03, 0x0b, 0x0b, 0x0b, 0x0b,\
/*  56 */ 0x0b, 0x0b, 0x01, 0x03, 0x01, 0x01, 0x01, 0x02,\
/*  64 */ 0x02, 0x08, 0x00, 0x10, 0x10, 0x10, 0x10, 0x00,\
/*  72 */ 0x10, 0x10, 0x00, 0x00, 0x10, 0x10, 0x00, 0x00,\
/*  80 */ 0x02, 0x02, 0x02, 0x00, 0x26, 0x26, 0x26, 0x26,\
/*  88 */ 0x26, 0x26, 0x26, 0x26, 0x26, 0x26, 0x00, 0x12,\
/*  96 */ 0x00, 0x10, 0x00, 0x00, 0x10, 0x10, 0x00, 0x00,\
/*  96 */ 0x20, 0x10, 0x00, 0x00, 0x00, 0x10, 0x10, 0x00,\
/* 104 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 112 */ 0x00, 0x00, 0x10, 0x10, 0x00, 0x00, 0x00, 0x00,\
/* 120 */ 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x04, 0x04,\
/* 128 */ 0x00, 0x00, 0x10, 0x10, 0x10, 0x00, 0x00, 0x10,\
/* 136 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x06,\
/* 144 */ 0x10, 0x00, 0x04, 0x1a, 0x00, 0x00, 0x00, 0x00,\
/* 152 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10,\
/* 160 */ 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 112 */ 0x00, 0x00, 0x00, 0x10, 0x10, 0x00, 0x00, 0x00,\
/* 120 */ 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x04,\
/* 128 */ 0x04, 0x00, 0x00, 0x10, 0x10, 0x10, 0x00, 0x00,\
/* 136 */ 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 144 */ 0x06, 0x10, 0x00, 0x04, 0x1a, 0x00, 0x00, 0x00,\
/* 152 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
/* 160 */ 0x10, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,\
}
/* 168 */ 0x00, 0x00,}

/* The sqlite3P2Values() routine is able to run faster if it knows
** the value of the largest JUMP opcode.  The smaller the maximum
** JUMP opcode the better, so the mkopcodeh.tcl script that
** generated this include file strives to group all JUMP opcodes
** together near the beginning of the list.
*/

  unsigned nProgressOps;        /* Number of opcodes for progress callback */
#endif
#ifndef SQLITE_OMIT_VIRTUALTABLE
  int nVTrans;                  /* Allocated size of aVTrans */
  Hash aModule;                 /* populated by sqlite3_create_module() */
  VtabCtx *pVtabCtx;            /* Context for active vtab connect/create */
  VTable **aVTrans;             /* Virtual tables with open transactions */
  VTable *pDisconnect;    /* Disconnect these in next sqlite3_prepare() */
  VTable *pDisconnect;          /* Disconnect these in next sqlite3_prepare() */
#endif
  Hash aFunc;                   /* Hash table of connection functions */
  Hash aCollSeq;                /* All collating sequences */
  BusyHandler busyHandler;      /* Busy callback */
  Db aDbStatic[2];              /* Static space for the 2 default backends */
  Savepoint *pSavepoint;        /* List of active savepoints */
  int busyTimeout;              /* Busy handler timeout, in msec */

#define SQLITE_LoadExtension  0x00010000  /* Enable load_extension */
#define SQLITE_LoadExtFunc    0x00020000  /* Enable load_extension() SQL func */
#define SQLITE_EnableTrigger  0x00040000  /* True to enable triggers */
#define SQLITE_DeferFKs       0x00080000  /* Defer all FK constraints */
#define SQLITE_QueryOnly      0x00100000  /* Disable database changes */
#define SQLITE_CellSizeCk     0x00200000  /* Check btree cell sizes on load */
#define SQLITE_Fts3Tokenizer  0x00400000  /* Enable fts3_tokenizer(2) */
#define SQLITE_EnableQPSG     0x00800000  /* Query Planner Stability Guarantee */
#define SQLITE_EnableQPSG     0x00800000  /* Query Planner Stability Guarantee*/
#define SQLITE_TriggerEQP     0x01000000  /* Show trigger EXPLAIN QUERY PLAN */

/* Flags used only if debugging */
#ifdef SQLITE_DEBUG
#define SQLITE_SqlTrace       0x08000000  /* Debug print SQL as it executes */
#define SQLITE_VdbeListing    0x10000000  /* Debug listings of VDBE programs */
#define SQLITE_VdbeTrace      0x20000000  /* True to trace VDBE execution */
#define SQLITE_VdbeAddopTrace 0x40000000  /* Trace sqlite3VdbeAddOp() calls */
#define SQLITE_VdbeEQP        0x80000000  /* Debug EXPLAIN QUERY PLAN */

#define SQLITE_FUNC_COALESCE 0x0200 /* Built-in coalesce() or ifnull() */
#define SQLITE_FUNC_UNLIKELY 0x0400 /* Built-in unlikely() function */
#define SQLITE_FUNC_CONSTANT 0x0800 /* Constant inputs give a constant output */
#define SQLITE_FUNC_MINMAX   0x1000 /* True for min() and max() aggregates */
#define SQLITE_FUNC_SLOCHNG  0x2000 /* "Slow Change". Value constant during a
                                    ** single query - might change over time */
#define SQLITE_FUNC_AFFINITY 0x4000 /* Built-in affinity() function */
#define SQLITE_FUNC_OFFSET   0x8000 /* Built-in sqlite_offset() function */

/*
** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
** used to create the initializers for the FuncDef structures.
**
**   FUNCTION(zName, nArg, iArg, bNC, xFunc)
**     Used to create a scalar function definition of a function zName

  unsigned idxType:2;      /* 1==UNIQUE, 2==PRIMARY KEY, 0==CREATE INDEX */
  unsigned bUnordered:1;   /* Use this index for == or IN queries only */
  unsigned uniqNotNull:1;  /* True if UNIQUE and NOT NULL for all columns */
  unsigned isResized:1;    /* True if resizeIndexObject() has been called */
  unsigned isCovering:1;   /* True if this is a covering index */
  unsigned noSkipScan:1;   /* Do not try to use skip-scan if true */
  unsigned hasStat1:1;     /* aiRowLogEst values come from sqlite_stat1 */
  unsigned bNoQuery:1;     /* Do not use this index to optimize queries */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  int nSample;             /* Number of elements in aSample[] */
  int nSampleCol;          /* Size of IndexSample.anEq[] and so on */
  tRowcnt *aAvgEq;         /* Average nEq values for keys not in aSample */
  IndexSample *aSample;    /* Samples of the left-most key */
  tRowcnt *aiRowEst;       /* Non-logarithmic stat1 data for this index */
  tRowcnt nRowEst0;        /* Non-logarithmic number of rows in the index */

};

/*
** The following are the meanings of bits in the Expr.flags field.
*/
#define EP_FromJoin  0x000001 /* Originates in ON/USING clause of outer join */
#define EP_Agg       0x000002 /* Contains one or more aggregate functions */
                  /* 0x000004 // available for use */
#define EP_HasFunc   0x000004 /* Contains one or more functions of any kind */
                  /* 0x000008 // available for use */
#define EP_Distinct  0x000010 /* Aggregate function with DISTINCT keyword */
#define EP_VarSelect 0x000020 /* pSelect is correlated, not constant */
#define EP_DblQuoted 0x000040 /* token.z was originally in "..." */
#define EP_InfixFunc 0x000080 /* True for an infix function: LIKE, GLOB, etc */
#define EP_Collate   0x000100 /* Tree contains a TK_COLLATE operator */
#define EP_Generic   0x000200 /* Ignore COLLATE or affinity on this tree */

#define EP_ConstFunc 0x080000 /* A SQLITE_FUNC_CONSTANT or _SLOCHNG function */
#define EP_CanBeNull 0x100000 /* Can be null despite NOT NULL constraint */
#define EP_Subquery  0x200000 /* Tree contains a TK_SELECT operator */
#define EP_Alias     0x400000 /* Is an alias for a result set column */
#define EP_Leaf      0x800000 /* Expr.pLeft, .pRight, .u.pSelect all NULL */

/*
** Combinations of two or more EP_* flags
** The EP_Propagate mask is a set of properties that automatically propagate
** upwards into parent nodes.
*/
#define EP_Propagate (EP_Collate|EP_Subquery) /* Propagate these bits up tree */
#define EP_Propagate (EP_Collate|EP_Subquery|EP_HasFunc)

/*
** These macros can be used to test, set, or clear bits in the
** Expr.flags field.
*/
#define ExprHasProperty(E,P)     (((E)->flags&(P))!=0)
#define ExprHasAllProperty(E,P)  (((E)->flags&(P))==(P))

        u16 iAlias;           /* Index into Parse.aAlias[] for zName */
      } x;
      int iConstExprReg;      /* Register in which Expr value is cached */
    } u;
  } a[1];                  /* One slot for each expression in the list */
};

/*
** An instance of this structure is used by the parser to record both
** the parse tree for an expression and the span of input text for an
** expression.
*/
struct ExprSpan {
  Expr *pExpr;          /* The expression parse tree */
  const char *zStart;   /* First character of input text */
  const char *zEnd;     /* One character past the end of input text */
};

/*
** An instance of this structure can hold a simple list of identifiers,
** such as the list "a,b,c" in the following statements:
**
**      INSERT INTO t(a,b,c) VALUES ...;
**      CREATE INDEX idx ON t(a,b,c);
**      CREATE TRIGGER trig BEFORE UPDATE ON t(a,b,c) ...;

#define NC_PartIdx   0x0002  /* True if resolving a partial index WHERE */
#define NC_IsCheck   0x0004  /* True if resolving names in a CHECK constraint */
#define NC_InAggFunc 0x0008  /* True if analyzing arguments to an agg func */
#define NC_HasAgg    0x0010  /* One or more aggregate functions seen */
#define NC_IdxExpr   0x0020  /* True if resolving columns of CREATE INDEX */
#define NC_VarSelect 0x0040  /* A correlated subquery has been seen */
#define NC_MinMaxAgg 0x1000  /* min/max aggregates seen.  See note above */
#define NC_Complex   0x2000  /* True if a function or subquery seen */

/*
** An instance of the following structure contains all information
** needed to generate code for a single SELECT statement.
**
** nLimit is set to -1 if there is no LIMIT clause.  nOffset is set to 0.
** If there is a LIMIT clause, the parser sets nLimit to the value of the

  Expr *pWhere;          /* The WHERE clause */
  ExprList *pGroupBy;    /* The GROUP BY clause */
  Expr *pHaving;         /* The HAVING clause */
  ExprList *pOrderBy;    /* The ORDER BY clause */
  Select *pPrior;        /* Prior select in a compound select statement */
  Select *pNext;         /* Next select to the left in a compound */
  Expr *pLimit;          /* LIMIT expression. NULL means not used. */
  Expr *pOffset;         /* OFFSET expression. NULL means not used. */
  With *pWith;           /* WITH clause attached to this select. Or NULL. */
};

/*
** Allowed values for Select.selFlags.  The "SF" prefix stands for
** "Select Flag".
**

#define SF_NestedFrom     0x00800  /* Part of a parenthesized FROM clause */
#define SF_MinMaxAgg      0x01000  /* Aggregate containing min() or max() */
#define SF_Recursive      0x02000  /* The recursive part of a recursive CTE */
#define SF_FixedLimit     0x04000  /* nSelectRow set by a constant LIMIT */
#define SF_MaybeConvert   0x08000  /* Need convertCompoundSelectToSubquery() */
#define SF_Converted      0x10000  /* By convertCompoundSelectToSubquery() */
#define SF_IncludeHidden  0x20000  /* Include hidden columns in output */
#define SF_ComplexResult  0x40000  /* Result set contains subquery or function */


/*
** The results of a SELECT can be distributed in several ways, as defined
** by one of the following macros.  The "SRT" prefix means "SELECT Result
** Type".
**

  int nRangeReg;       /* Size of the temporary register block */
  int iRangeReg;       /* First register in temporary register block */
  int nErr;            /* Number of errors seen */
  int nTab;            /* Number of previously allocated VDBE cursors */
  int nMem;            /* Number of memory cells used so far */
  int nOpAlloc;        /* Number of slots allocated for Vdbe.aOp[] */
  int szOpAlloc;       /* Bytes of memory space allocated for Vdbe.aOp[] */
  int iSelfTab;        /* Table for associated with an index on expr, or negative
  int iSelfTab;        /* Table associated with an index on expr, or negative
                       ** of the base register during check-constraint eval */
  int iCacheLevel;     /* ColCache valid when aColCache[].iLevel<=iCacheLevel */
  int iCacheCnt;       /* Counter used to generate aColCache[].lru values */
  int nLabel;          /* Number of labels used */
  int *aLabel;         /* Space to hold the labels */
  ExprList *pConstExpr;/* Constant expressions */
  Token constraintName;/* Name of the constraint currently being parsed */

#define OPFLAG_BULKCSR       0x01    /* OP_Open** used to open bulk cursor */
#define OPFLAG_SEEKEQ        0x02    /* OP_Open** cursor uses EQ seek only */
#define OPFLAG_FORDELETE     0x08    /* OP_Open should use BTREE_FORDELETE */
#define OPFLAG_P2ISREG       0x10    /* P2 to OP_Open** is a register number */
#define OPFLAG_PERMUTE       0x01    /* OP_Compare: use the permutation */
#define OPFLAG_SAVEPOSITION  0x02    /* OP_Delete/Insert: save cursor pos */
#define OPFLAG_AUXDELETE     0x04    /* OP_Delete: index in a DELETE op */
#define OPFLAG_NOCHNG_MAGIC  0x6d    /* OP_MakeRecord: serialtype 10 is ok */

/*
 * Each trigger present in the database schema is stored as an instance of
 * struct Trigger.
 *
 * Pointers to instances of struct Trigger are stored in two ways.
 * 1. In the "trigHash" hash table (part of the sqlite3* that represents the

  u8 orconf;           /* OE_Rollback etc. */
  Trigger *pTrig;      /* The trigger that this step is a part of */
  Select *pSelect;     /* SELECT statement or RHS of INSERT INTO SELECT ... */
  char *zTarget;       /* Target table for DELETE, UPDATE, INSERT */
  Expr *pWhere;        /* The WHERE clause for DELETE or UPDATE steps */
  ExprList *pExprList; /* SET clause for UPDATE. */
  IdList *pIdList;     /* Column names for INSERT */
  char *zSpan;         /* Original SQL text of this command */
  TriggerStep *pNext;  /* Next in the link-list */
  TriggerStep *pLast;  /* Last element in link-list. Valid for 1st elem only */
};

/*
** The following structure contains information used by the sqliteFix...
** routines as they walk the parse tree to make database references

/*
** The SQLITE_*_BKPT macros are substitutes for the error codes with
** the same name but without the _BKPT suffix.  These macros invoke
** routines that report the line-number on which the error originated
** using sqlite3_log().  The routines also provide a convenient place
** to set a debugger breakpoint.
*/
SQLITE_PRIVATE int sqlite3ReportError(int iErr, int lineno, const char *zType);
SQLITE_PRIVATE int sqlite3CorruptError(int);
SQLITE_PRIVATE int sqlite3MisuseError(int);
SQLITE_PRIVATE int sqlite3CantopenError(int);
#define SQLITE_CORRUPT_BKPT sqlite3CorruptError(__LINE__)
#define SQLITE_MISUSE_BKPT sqlite3MisuseError(__LINE__)
#define SQLITE_CANTOPEN_BKPT sqlite3CantopenError(__LINE__)
#ifdef SQLITE_DEBUG

SQLITE_PRIVATE void *sqlite3Malloc(u64);
SQLITE_PRIVATE void *sqlite3MallocZero(u64);
SQLITE_PRIVATE void *sqlite3DbMallocZero(sqlite3*, u64);
SQLITE_PRIVATE void *sqlite3DbMallocRaw(sqlite3*, u64);
SQLITE_PRIVATE void *sqlite3DbMallocRawNN(sqlite3*, u64);
SQLITE_PRIVATE char *sqlite3DbStrDup(sqlite3*,const char*);
SQLITE_PRIVATE char *sqlite3DbStrNDup(sqlite3*,const char*, u64);
SQLITE_PRIVATE char *sqlite3DbSpanDup(sqlite3*,const char*,const char*);
SQLITE_PRIVATE void *sqlite3Realloc(void*, u64);
SQLITE_PRIVATE void *sqlite3DbReallocOrFree(sqlite3 *, void *, u64);
SQLITE_PRIVATE void *sqlite3DbRealloc(sqlite3 *, void *, u64);
SQLITE_PRIVATE void sqlite3DbFree(sqlite3*, void*);
SQLITE_PRIVATE void sqlite3DbFreeNN(sqlite3*, void*);
SQLITE_PRIVATE int sqlite3MallocSize(void*);
SQLITE_PRIVATE int sqlite3DbMallocSize(sqlite3*, void*);

SQLITE_PRIVATE void sqlite3StatusDown(int, int);
SQLITE_PRIVATE void sqlite3StatusHighwater(int, int);
SQLITE_PRIVATE int sqlite3LookasideUsed(sqlite3*,int*);

/* Access to mutexes used by sqlite3_status() */
SQLITE_PRIVATE sqlite3_mutex *sqlite3Pcache1Mutex(void);
SQLITE_PRIVATE sqlite3_mutex *sqlite3MallocMutex(void);

#if defined(SQLITE_ENABLE_MULTITHREADED_CHECKS) && !defined(SQLITE_MUTEX_OMIT)
SQLITE_PRIVATE void sqlite3MutexWarnOnContention(sqlite3_mutex*);
#else
# define sqlite3MutexWarnOnContention(x)
#endif

#ifndef SQLITE_OMIT_FLOATING_POINT
SQLITE_PRIVATE   int sqlite3IsNaN(double);
#else
# define sqlite3IsNaN(X)  0
#endif

SQLITE_PRIVATE Expr *sqlite3ExprFunction(Parse*,ExprList*, Token*);
SQLITE_PRIVATE void sqlite3ExprAssignVarNumber(Parse*, Expr*, u32);
SQLITE_PRIVATE void sqlite3ExprDelete(sqlite3*, Expr*);
SQLITE_PRIVATE ExprList *sqlite3ExprListAppend(Parse*,ExprList*,Expr*);
SQLITE_PRIVATE ExprList *sqlite3ExprListAppendVector(Parse*,ExprList*,IdList*,Expr*);
SQLITE_PRIVATE void sqlite3ExprListSetSortOrder(ExprList*,int);
SQLITE_PRIVATE void sqlite3ExprListSetName(Parse*,ExprList*,Token*,int);
SQLITE_PRIVATE void sqlite3ExprListSetSpan(Parse*,ExprList*,ExprSpan*);
SQLITE_PRIVATE void sqlite3ExprListSetSpan(Parse*,ExprList*,const char*,const char*);
SQLITE_PRIVATE void sqlite3ExprListDelete(sqlite3*, ExprList*);
SQLITE_PRIVATE u32 sqlite3ExprListFlags(const ExprList*);
SQLITE_PRIVATE int sqlite3Init(sqlite3*, char**);
SQLITE_PRIVATE int sqlite3InitCallback(void*, int, char**, char**);
SQLITE_PRIVATE void sqlite3Pragma(Parse*,Token*,Token*,Token*,int);
#ifndef SQLITE_OMIT_VIRTUALTABLE
SQLITE_PRIVATE Module *sqlite3PragmaVtabRegister(sqlite3*,const char *zName);

#else
# define sqlite3ColumnPropertiesFromName(T,C) /* no-op */
#endif
SQLITE_PRIVATE void sqlite3AddColumn(Parse*,Token*,Token*);
SQLITE_PRIVATE void sqlite3AddNotNull(Parse*, int);
SQLITE_PRIVATE void sqlite3AddPrimaryKey(Parse*, ExprList*, int, int, int);
SQLITE_PRIVATE void sqlite3AddCheckConstraint(Parse*, Expr*);
SQLITE_PRIVATE void sqlite3AddDefaultValue(Parse*,ExprSpan*);
SQLITE_PRIVATE void sqlite3AddDefaultValue(Parse*,Expr*,const char*,const char*);
SQLITE_PRIVATE void sqlite3AddCollateType(Parse*, Token*);
SQLITE_PRIVATE void sqlite3EndTable(Parse*,Token*,Token*,u8,Select*);
SQLITE_PRIVATE int sqlite3ParseUri(const char*,const char*,unsigned int*,
                    sqlite3_vfs**,char**,char **);
SQLITE_PRIVATE Btree *sqlite3DbNameToBtree(sqlite3*,const char*);

#ifdef SQLITE_UNTESTABLE

SQLITE_PRIVATE void sqlite3SrcListDelete(sqlite3*, SrcList*);
SQLITE_PRIVATE Index *sqlite3AllocateIndexObject(sqlite3*,i16,int,char**);
SQLITE_PRIVATE void sqlite3CreateIndex(Parse*,Token*,Token*,SrcList*,ExprList*,int,Token*,
                          Expr*, int, int, u8);
SQLITE_PRIVATE void sqlite3DropIndex(Parse*, SrcList*, int);
SQLITE_PRIVATE int sqlite3Select(Parse*, Select*, SelectDest*);
SQLITE_PRIVATE Select *sqlite3SelectNew(Parse*,ExprList*,SrcList*,Expr*,ExprList*,
                         Expr*,ExprList*,u32,Expr*,Expr*);
                         Expr*,ExprList*,u32,Expr*);
SQLITE_PRIVATE void sqlite3SelectDelete(sqlite3*, Select*);
SQLITE_PRIVATE Table *sqlite3SrcListLookup(Parse*, SrcList*);
SQLITE_PRIVATE int sqlite3IsReadOnly(Parse*, Table*, int);
SQLITE_PRIVATE void sqlite3OpenTable(Parse*, int iCur, int iDb, Table*, int);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
SQLITE_PRIVATE Expr *sqlite3LimitWhere(Parse*,SrcList*,Expr*,ExprList*,Expr*,Expr*,char*);
SQLITE_PRIVATE Expr *sqlite3LimitWhere(Parse*,SrcList*,Expr*,ExprList*,Expr*,char*);
#endif
SQLITE_PRIVATE void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
SQLITE_PRIVATE void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
SQLITE_PRIVATE void sqlite3DeleteFrom(Parse*, SrcList*, Expr*, ExprList*, Expr*);
SQLITE_PRIVATE void sqlite3Update(Parse*, SrcList*, ExprList*,Expr*,int,ExprList*,Expr*);
SQLITE_PRIVATE WhereInfo *sqlite3WhereBegin(Parse*,SrcList*,Expr*,ExprList*,ExprList*,u16,int);
SQLITE_PRIVATE void sqlite3WhereEnd(WhereInfo*);
SQLITE_PRIVATE LogEst sqlite3WhereOutputRowCount(WhereInfo*);
SQLITE_PRIVATE int sqlite3WhereIsDistinct(WhereInfo*);
SQLITE_PRIVATE int sqlite3WhereIsOrdered(WhereInfo*);
SQLITE_PRIVATE int sqlite3WhereOrderedInnerLoop(WhereInfo*);
SQLITE_PRIVATE int sqlite3WhereIsSorted(WhereInfo*);

SQLITE_PRIVATE void sqlite3RegisterDateTimeFunctions(void);
SQLITE_PRIVATE void sqlite3RegisterPerConnectionBuiltinFunctions(sqlite3*);
SQLITE_PRIVATE int sqlite3SafetyCheckOk(sqlite3*);
SQLITE_PRIVATE int sqlite3SafetyCheckSickOrOk(sqlite3*);
SQLITE_PRIVATE void sqlite3ChangeCookie(Parse*, int);

#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
SQLITE_PRIVATE void sqlite3MaterializeView(Parse*, Table*, Expr*, int);
SQLITE_PRIVATE void sqlite3MaterializeView(Parse*, Table*, Expr*, ExprList*,Expr*,int);
#endif

#ifndef SQLITE_OMIT_TRIGGER
SQLITE_PRIVATE   void sqlite3BeginTrigger(Parse*, Token*,Token*,int,int,IdList*,SrcList*,
                           Expr*,int, int);
SQLITE_PRIVATE   void sqlite3FinishTrigger(Parse*, TriggerStep*, Token*);
SQLITE_PRIVATE   void sqlite3DropTrigger(Parse*, SrcList*, int);
SQLITE_PRIVATE   void sqlite3DropTriggerPtr(Parse*, Trigger*);
SQLITE_PRIVATE   Trigger *sqlite3TriggersExist(Parse *, Table*, int, ExprList*, int *pMask);
SQLITE_PRIVATE   Trigger *sqlite3TriggerList(Parse *, Table *);
SQLITE_PRIVATE   void sqlite3CodeRowTrigger(Parse*, Trigger *, int, ExprList*, int, Table *,
                            int, int, int);
SQLITE_PRIVATE   void sqlite3CodeRowTriggerDirect(Parse *, Trigger *, Table *, int, int, int);
  void sqliteViewTriggers(Parse*, Table*, Expr*, int, ExprList*);
SQLITE_PRIVATE   void sqlite3DeleteTriggerStep(sqlite3*, TriggerStep*);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerSelectStep(sqlite3*,Select*);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerSelectStep(sqlite3*,Select*,
                                        const char*,const char*);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerInsertStep(sqlite3*,Token*, IdList*,
                                        Select*,u8);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerUpdateStep(sqlite3*,Token*,ExprList*, Expr*, u8);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerDeleteStep(sqlite3*,Token*, Expr*);
                                        Select*,u8,const char*,const char*);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerUpdateStep(sqlite3*,Token*,ExprList*, Expr*, u8,
                                        const char*,const char*);
SQLITE_PRIVATE   TriggerStep *sqlite3TriggerDeleteStep(sqlite3*,Token*, Expr*,
                                        const char*,const char*);
SQLITE_PRIVATE   void sqlite3DeleteTrigger(sqlite3*, Trigger*);
SQLITE_PRIVATE   void sqlite3UnlinkAndDeleteTrigger(sqlite3*,int,const char*);
SQLITE_PRIVATE   u32 sqlite3TriggerColmask(Parse*,Trigger*,ExprList*,int,int,Table*,int);
# define sqlite3ParseToplevel(p) ((p)->pToplevel ? (p)->pToplevel : (p))
# define sqlite3IsToplevel(p) ((p)->pToplevel==0)
#else
# define sqlite3TriggersExist(B,C,D,E,F) 0

  #define sqlite3ConnectionUnlocked(x)
  #define sqlite3ConnectionClosed(x)
#endif

#ifdef SQLITE_DEBUG
SQLITE_PRIVATE   void sqlite3ParserTrace(FILE*, char *);
#endif
#if defined(YYCOVERAGE)
SQLITE_PRIVATE   int sqlite3ParserCoverage(FILE*);
#endif

/*
** If the SQLITE_ENABLE IOTRACE exists then the global variable
** sqlite3IoTrace is a pointer to a printf-like routine used to
** print I/O tracing messages.
*/
#ifdef SQLITE_ENABLE_IOTRACE

/* One or more of the following flags are set to indicate the validOK
** representations of the value stored in the Mem struct.
**
** If the MEM_Null flag is set, then the value is an SQL NULL value.
** For a pointer type created using sqlite3_bind_pointer() or
** sqlite3_result_pointer() the MEM_Term and MEM_Subtype flags are also set.
** If both MEM_Null and MEM_Zero are set, that means that the value is
** an unchanging column value from VColumn.
**
** If the MEM_Str flag is set then Mem.z points at a string representation.
** Usually this is encoded in the same unicode encoding as the main
** database (see below for exceptions). If the MEM_Term flag is also
** set, then the string is nul terminated. The MEM_Int and MEM_Real 
** flags may coexist with the MEM_Str flag.
*/

** dates afterwards, depending on locale.  Beware of this difference.
**
** The conversion algorithms are implemented based on descriptions
** in the following text:
**
**      Jean Meeus
**      Astronomical Algorithms, 2nd Edition, 1998
**      ISBM 0-943396-61-1
**      ISBN 0-943396-61-1
**      Willmann-Bell, Inc
**      Richmond, Virginia (USA)
*/
/* #include "sqliteInt.h" */
/* #include <stdlib.h> */
/* #include <assert.h> */
#include <time.h>

** allocate a mutex while the system is uninitialized.
*/
static SQLITE_WSD int mutexIsInit = 0;
#endif /* SQLITE_DEBUG && !defined(SQLITE_MUTEX_OMIT) */


#ifndef SQLITE_MUTEX_OMIT

#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS
/*
** This block (enclosed by SQLITE_ENABLE_MULTITHREADED_CHECKS) contains
** the implementation of a wrapper around the system default mutex
** implementation (sqlite3DefaultMutex()). 
**
** Most calls are passed directly through to the underlying default
** mutex implementation. Except, if a mutex is configured by calling
** sqlite3MutexWarnOnContention() on it, then if contention is ever
** encountered within xMutexEnter() a warning is emitted via sqlite3_log().
**
** This type of mutex is used as the database handle mutex when testing
** apps that usually use SQLITE_CONFIG_MULTITHREAD mode.
*/

/* 
** Type for all mutexes used when SQLITE_ENABLE_MULTITHREADED_CHECKS
** is defined. Variable CheckMutex.mutex is a pointer to the real mutex
** allocated by the system mutex implementation. Variable iType is usually set
** to the type of mutex requested - SQLITE_MUTEX_RECURSIVE, SQLITE_MUTEX_FAST
** or one of the static mutex identifiers. Or, if this is a recursive mutex
** that has been configured using sqlite3MutexWarnOnContention(), it is
** set to SQLITE_MUTEX_WARNONCONTENTION.
*/
typedef struct CheckMutex CheckMutex;
struct CheckMutex {
  int iType;
  sqlite3_mutex *mutex;
};

#define SQLITE_MUTEX_WARNONCONTENTION  (-1)

/* 
** Pointer to real mutex methods object used by the CheckMutex
** implementation. Set by checkMutexInit(). 
*/
static SQLITE_WSD const sqlite3_mutex_methods *pGlobalMutexMethods;

#ifdef SQLITE_DEBUG
static int checkMutexHeld(sqlite3_mutex *p){
  return pGlobalMutexMethods->xMutexHeld(((CheckMutex*)p)->mutex);
}
static int checkMutexNotheld(sqlite3_mutex *p){
  return pGlobalMutexMethods->xMutexNotheld(((CheckMutex*)p)->mutex);
}
#endif

/*
** Initialize and deinitialize the mutex subsystem.
*/
static int checkMutexInit(void){ 
  pGlobalMutexMethods = sqlite3DefaultMutex();
  return SQLITE_OK; 
}
static int checkMutexEnd(void){ 
  pGlobalMutexMethods = 0;
  return SQLITE_OK; 
}

/*
** Allocate a mutex.
*/
static sqlite3_mutex *checkMutexAlloc(int iType){
  static CheckMutex staticMutexes[] = {
    {2, 0}, {3, 0}, {4, 0}, {5, 0},
    {6, 0}, {7, 0}, {8, 0}, {9, 0},
    {10, 0}, {11, 0}, {12, 0}, {13, 0}
  };
  CheckMutex *p = 0;

  assert( SQLITE_MUTEX_RECURSIVE==1 && SQLITE_MUTEX_FAST==0 );
  if( iType<2 ){
    p = sqlite3MallocZero(sizeof(CheckMutex));
    if( p==0 ) return 0;
    p->iType = iType;
  }else{
#ifdef SQLITE_ENABLE_API_ARMOR
    if( iType-2>=ArraySize(staticMutexes) ){
      (void)SQLITE_MISUSE_BKPT;
      return 0;
    }
#endif
    p = &staticMutexes[iType-2];
  }

  if( p->mutex==0 ){
    p->mutex = pGlobalMutexMethods->xMutexAlloc(iType);
    if( p->mutex==0 ){
      if( iType<2 ){
        sqlite3_free(p);
      }
      p = 0;
    }
  }

  return (sqlite3_mutex*)p;
}

/*
** Free a mutex.
*/
static void checkMutexFree(sqlite3_mutex *p){
  assert( SQLITE_MUTEX_RECURSIVE<2 );
  assert( SQLITE_MUTEX_FAST<2 );
  assert( SQLITE_MUTEX_WARNONCONTENTION<2 );

#if SQLITE_ENABLE_API_ARMOR
  if( ((CheckMutex*)p)->iType<2 )
#endif
  {
    CheckMutex *pCheck = (CheckMutex*)p;
    pGlobalMutexMethods->xMutexFree(pCheck->mutex);
    sqlite3_free(pCheck);
  }
#ifdef SQLITE_ENABLE_API_ARMOR
  else{
    (void)SQLITE_MISUSE_BKPT;
  }
#endif
}

/*
** Enter the mutex.
*/
static void checkMutexEnter(sqlite3_mutex *p){
  CheckMutex *pCheck = (CheckMutex*)p;
  if( pCheck->iType==SQLITE_MUTEX_WARNONCONTENTION ){
    if( SQLITE_OK==pGlobalMutexMethods->xMutexTry(pCheck->mutex) ){
      return;
    }
    sqlite3_log(SQLITE_MISUSE, 
        "illegal multi-threaded access to database connection"
    );
  }
  pGlobalMutexMethods->xMutexEnter(pCheck->mutex);
}

/*
** Enter the mutex (do not block).
*/
static int checkMutexTry(sqlite3_mutex *p){
  CheckMutex *pCheck = (CheckMutex*)p;
  return pGlobalMutexMethods->xMutexTry(pCheck->mutex);
}

/*
** Leave the mutex.
*/
static void checkMutexLeave(sqlite3_mutex *p){
  CheckMutex *pCheck = (CheckMutex*)p;
  pGlobalMutexMethods->xMutexLeave(pCheck->mutex);
}

sqlite3_mutex_methods const *multiThreadedCheckMutex(void){
  static const sqlite3_mutex_methods sMutex = {
    checkMutexInit,
    checkMutexEnd,
    checkMutexAlloc,
    checkMutexFree,
    checkMutexEnter,
    checkMutexTry,
    checkMutexLeave,
#ifdef SQLITE_DEBUG
    checkMutexHeld,
    checkMutexNotheld
#else
    0,
    0
#endif
  };
  return &sMutex;
}

/*
** Mark the SQLITE_MUTEX_RECURSIVE mutex passed as the only argument as
** one on which there should be no contention.
*/
SQLITE_PRIVATE void sqlite3MutexWarnOnContention(sqlite3_mutex *p){
  if( sqlite3GlobalConfig.mutex.xMutexAlloc==checkMutexAlloc ){
    CheckMutex *pCheck = (CheckMutex*)p;
    assert( pCheck->iType==SQLITE_MUTEX_RECURSIVE );
    pCheck->iType = SQLITE_MUTEX_WARNONCONTENTION;
  }
}
#endif   /* ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS */

/*
** Initialize the mutex system.
*/
SQLITE_PRIVATE int sqlite3MutexInit(void){ 
  int rc = SQLITE_OK;
  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
    /* If the xMutexAlloc method has not been set, then the user did not
    ** install a mutex implementation via sqlite3_config() prior to 
    ** sqlite3_initialize() being called. This block copies pointers to
    ** the default implementation into the sqlite3GlobalConfig structure.
    */
    sqlite3_mutex_methods const *pFrom;
    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;

    if( sqlite3GlobalConfig.bCoreMutex ){
#ifdef SQLITE_ENABLE_MULTITHREADED_CHECKS
      pFrom = multiThreadedCheckMutex();
#else
      pFrom = sqlite3DefaultMutex();
#endif
    }else{
      pFrom = sqlite3NoopMutex();
    }
    pTo->xMutexInit = pFrom->xMutexInit;
    pTo->xMutexEnd = pFrom->xMutexEnd;
    pTo->xMutexFree = pFrom->xMutexFree;
    pTo->xMutexEnter = pFrom->xMutexEnter;

SQLITE_API int sqlite3_mutex_notheld(sqlite3_mutex *p){
  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld );
  return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);
}
#endif

#endif /* !defined(SQLITE_MUTEX_OMIT) */


/************** End of mutex.c ***********************************************/
/************** Begin file mutex_noop.c **************************************/
/*
** 2008 October 07
**
** The author disclaims copyright to this source code.  In place of

  zNew = sqlite3DbMallocRawNN(db, n+1);
  if( zNew ){
    memcpy(zNew, z, (size_t)n);
    zNew[n] = 0;
  }
  return zNew;
}

/*
** The text between zStart and zEnd represents a phrase within a larger
** SQL statement.  Make a copy of this phrase in space obtained form
** sqlite3DbMalloc().  Omit leading and trailing whitespace.
*/
SQLITE_PRIVATE char *sqlite3DbSpanDup(sqlite3 *db, const char *zStart, const char *zEnd){
  int n;
  while( sqlite3Isspace(zStart[0]) ) zStart++;
  n = (int)(zEnd - zStart);
  while( ALWAYS(n>0) && sqlite3Isspace(zStart[n-1]) ) n--;
  return sqlite3DbStrNDup(db, zStart, n);
}

/*
** Free any prior content in *pz and replace it with a copy of zNew.
*/
SQLITE_PRIVATE void sqlite3SetString(char **pz, sqlite3 *db, const char *zNew){
  sqlite3DbFree(db, *pz);
  *pz = sqlite3DbStrDup(db, zNew);

  StrAccum acc;
  char zBuf[500];
  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
  va_start(ap,zFormat);
  sqlite3VXPrintf(&acc, zFormat, ap);
  va_end(ap);
  sqlite3StrAccumFinish(&acc);
#ifdef SQLITE_OS_TRACE_PROC
  {
    extern void SQLITE_OS_TRACE_PROC(const char *zBuf, int nBuf);
    SQLITE_OS_TRACE_PROC(zBuf, sizeof(zBuf));
  }
#else
  fprintf(stdout,"%s", zBuf);
  fflush(stdout);
#endif
}
#endif


/*
** variable-argument wrapper around sqlite3VXPrintf().  The bFlags argument
** can contain the bit SQLITE_PRINTF_INTERNAL enable internal formats.

      n = 0;
      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++;
    }
    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++){

      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);
      sqlite3TreeViewExpr(pView, p->pLimit->pLeft, p->pLimit->pRight!=0);
      sqlite3TreeViewPop(pView);
    }
    if( p->pOffset ){
      sqlite3TreeViewItem(pView, "OFFSET", (n--)>0);
      sqlite3TreeViewExpr(pView, p->pOffset, 0);
      if( p->pLimit->pRight ){
        sqlite3TreeViewItem(pView, "OFFSET", (n--)>0);
        sqlite3TreeViewExpr(pView, p->pLimit->pRight, 0);
        sqlite3TreeViewPop(pView);
      }
      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;

  if( pList==0 ){
    sqlite3TreeViewLine(pView, "%s (empty)", zLabel);
  }else{
    int i;
    sqlite3TreeViewLine(pView, "%s", zLabel);
    for(i=0; i<pList->nExpr; i++){
      int j = pList->a[i].u.x.iOrderByCol;
      char *zName = pList->a[i].zName;
      if( j ){
      if( j || zName ){
        sqlite3TreeViewPush(pView, 0);
      }
      if( zName ){
        sqlite3TreeViewLine(pView, "AS %s", zName);
      }
      if( j ){
        sqlite3TreeViewLine(pView, "iOrderByCol=%d", j);
      }
      sqlite3TreeViewExpr(pView, pList->a[i].pExpr, i<pList->nExpr-1);
      if( j || zName ){
      if( j ) sqlite3TreeViewPop(pView);
        sqlite3TreeViewPop(pView);
      }
    }
  }
}
SQLITE_PRIVATE void sqlite3TreeViewExprList(
  TreeView *pView,
  const ExprList *pList,
  u8 moreToFollow,

    return 1;
  }
  a = (unsigned char *)zLeft;
  b = (unsigned char *)zRight;
  while( N-- > 0 && *a!=0 && UpperToLower[*a]==UpperToLower[*b]){ a++; b++; }
  return N<0 ? 0 : UpperToLower[*a] - UpperToLower[*b];
}

/*
** Compute 10 to the E-th power.  Examples:  E==1 results in 10.
** E==2 results in 100.  E==50 results in 1.0e50.
**
** This routine only works for values of E between 1 and 341.
*/
static LONGDOUBLE_TYPE sqlite3Pow10(int E){
#if defined(_MSC_VER)
  static const LONGDOUBLE_TYPE x[] = {
    1.0e+001,
    1.0e+002,
    1.0e+004,
    1.0e+008,
    1.0e+016,
    1.0e+032,
    1.0e+064,
    1.0e+128,
    1.0e+256
  };
  LONGDOUBLE_TYPE r = 1.0;
  int i;
  assert( E>=0 && E<=307 );
  for(i=0; E!=0; i++, E >>=1){
    if( E & 1 ) r *= x[i];
  }
  return r;
#else
  LONGDOUBLE_TYPE x = 10.0;
  LONGDOUBLE_TYPE r = 1.0;
  while(1){
    if( E & 1 ) r *= x;
    E >>= 1;
    if( E==0 ) break;
    x *= x;
  }
  return r; 
#endif
}

/*
** The string z[] is an text representation of a real number.
** Convert this string to a double and write it into *pResult.
**
** The string z[] is length bytes in length (bytes, not characters) and
** uses the encoding enc.  The string is not necessarily zero-terminated.

  }else if( *z=='+' ){
    z+=incr;
  }

  /* copy max significant digits to significand */
  while( z<zEnd && sqlite3Isdigit(*z) && s<((LARGEST_INT64-9)/10) ){
    s = s*10 + (*z - '0');
    z+=incr, nDigits++;
    z+=incr; nDigits++;
  }

  /* skip non-significant significand digits
  ** (increase exponent by d to shift decimal left) */
  while( z<zEnd && sqlite3Isdigit(*z) ) z+=incr, nDigits++, d++;
  while( z<zEnd && sqlite3Isdigit(*z) ){ z+=incr; nDigits++; d++; }
  if( z>=zEnd ) goto do_atof_calc;

  /* if decimal point is present */
  if( *z=='.' ){
    z+=incr;
    /* copy digits from after decimal to significand
    ** (decrease exponent by d to shift decimal right) */
    while( z<zEnd && sqlite3Isdigit(*z) ){
      if( s<((LARGEST_INT64-9)/10) ){
        s = s*10 + (*z - '0');
        d--;
      }
      z+=incr, nDigits++;
      z+=incr; nDigits++;
    }
  }
  if( z>=zEnd ) goto do_atof_calc;

  /* if exponent is present */
  if( *z=='e' || *z=='E' ){
    z+=incr;

    /* adjust the sign of significand */
    s = sign<0 ? -s : s;

    if( e==0 ){                                         /*OPTIMIZATION-IF-TRUE*/
      result = (double)s;
    }else{
      LONGDOUBLE_TYPE scale = 1.0;
      /* attempt to handle extremely small/large numbers better */
      if( e>307 ){                                      /*OPTIMIZATION-IF-TRUE*/
        if( e<342 ){                                    /*OPTIMIZATION-IF-TRUE*/
          while( e%308 ) { scale *= 1.0e+1; e -= 1; }
          LONGDOUBLE_TYPE scale = sqlite3Pow10(e-308);
          if( esign<0 ){
            result = s / scale;
            result /= 1.0e+308;
          }else{
            result = s * scale;
            result *= 1.0e+308;
          }
        }else{ assert( e>=342 );
          if( esign<0 ){
            result = 0.0*s;
          }else{
#ifdef INFINITY
            result = INFINITY*s;
#else
            result = 1e308*1e308*s;  /* Infinity */
#endif
          }
        }
      }else{
        /* 1.0e+22 is the largest power of 10 than can be 
        ** represented exactly. */
        while( e%22 ) { scale *= 1.0e+1; e -= 1; }
        LONGDOUBLE_TYPE scale = sqlite3Pow10(e);
        while( e>0 ) { scale *= 1.0e+22; e -= 22; }
        if( esign<0 ){
          result = s / scale;
        }else{
          result = s * scale;
        }
      }
    }

    /*  89 */ "Subtract"         OpHelp("r[P3]=r[P2]-r[P1]"),
    /*  90 */ "Multiply"         OpHelp("r[P3]=r[P1]*r[P2]"),
    /*  91 */ "Divide"           OpHelp("r[P3]=r[P2]/r[P1]"),
    /*  92 */ "Remainder"        OpHelp("r[P3]=r[P2]%r[P1]"),
    /*  93 */ "Concat"           OpHelp("r[P3]=r[P2]+r[P1]"),
    /*  94 */ "Compare"          OpHelp("r[P1@P3] <-> r[P2@P3]"),
    /*  95 */ "BitNot"           OpHelp("r[P1]= ~r[P1]"),
    /*  96 */ "Column"           OpHelp("r[P3]=PX"),
    /*  96 */ "Offset"           OpHelp("r[P3] = sqlite_offset(P1)"),
    /*  97 */ "String8"          OpHelp("r[P2]='P4'"),
    /*  98 */ "Column"           OpHelp("r[P3]=PX"),
    /*  98 */ "Affinity"         OpHelp("affinity(r[P1@P2])"),
    /*  99 */ "MakeRecord"       OpHelp("r[P3]=mkrec(r[P1@P2])"),
    /* 100 */ "Count"            OpHelp("r[P2]=count()"),
    /* 101 */ "ReadCookie"       OpHelp(""),
    /* 102 */ "SetCookie"        OpHelp(""),
    /* 103 */ "ReopenIdx"        OpHelp("root=P2 iDb=P3"),
    /* 104 */ "OpenRead"         OpHelp("root=P2 iDb=P3"),
    /* 105 */ "OpenWrite"        OpHelp("root=P2 iDb=P3"),
    /* 106 */ "OpenDup"          OpHelp(""),
    /* 107 */ "OpenAutoindex"    OpHelp("nColumn=P2"),
    /* 108 */ "OpenEphemeral"    OpHelp("nColumn=P2"),
    /* 109 */ "SorterOpen"       OpHelp(""),
    /* 110 */ "SequenceTest"     OpHelp("if( cursor[P1].ctr++ ) pc = P2"),
    /* 111 */ "OpenPseudo"       OpHelp("P3 columns in r[P2]"),
    /* 112 */ "Close"            OpHelp(""),
    /* 113 */ "ColumnsUsed"      OpHelp(""),
    /* 114 */ "Sequence"         OpHelp("r[P2]=cursor[P1].ctr++"),
    /* 115 */ "NewRowid"         OpHelp("r[P2]=rowid"),
    /* 116 */ "Insert"           OpHelp("intkey=r[P3] data=r[P2]"),
    /* 117 */ "InsertInt"        OpHelp("intkey=P3 data=r[P2]"),
    /* 118 */ "Delete"           OpHelp(""),
    /* 119 */ "ResetCount"       OpHelp(""),
    /* 120 */ "SorterCompare"    OpHelp("if key(P1)!=trim(r[P3],P4) goto P2"),
    /* 121 */ "SorterData"       OpHelp("r[P2]=data"),
    /* 122 */ "RowData"          OpHelp("r[P2]=data"),
    /* 123 */ "Rowid"            OpHelp("r[P2]=rowid"),
    /* 124 */ "NullRow"          OpHelp(""),
    /* 125 */ "SeekEnd"          OpHelp(""),
    /* 126 */ "SorterInsert"     OpHelp("key=r[P2]"),
    /* 127 */ "IdxInsert"        OpHelp("key=r[P2]"),
    /* 128 */ "IdxDelete"        OpHelp("key=r[P2@P3]"),
    /* 129 */ "DeferredSeek"     OpHelp("Move P3 to P1.rowid if needed"),
    /* 130 */ "IdxRowid"         OpHelp("r[P2]=rowid"),
    /*  99 */ "Affinity"         OpHelp("affinity(r[P1@P2])"),
    /* 100 */ "MakeRecord"       OpHelp("r[P3]=mkrec(r[P1@P2])"),
    /* 101 */ "Count"            OpHelp("r[P2]=count()"),
    /* 102 */ "ReadCookie"       OpHelp(""),
    /* 103 */ "SetCookie"        OpHelp(""),
    /* 104 */ "ReopenIdx"        OpHelp("root=P2 iDb=P3"),
    /* 105 */ "OpenRead"         OpHelp("root=P2 iDb=P3"),
    /* 106 */ "OpenWrite"        OpHelp("root=P2 iDb=P3"),
    /* 107 */ "OpenDup"          OpHelp(""),
    /* 108 */ "OpenAutoindex"    OpHelp("nColumn=P2"),
    /* 109 */ "OpenEphemeral"    OpHelp("nColumn=P2"),
    /* 110 */ "SorterOpen"       OpHelp(""),
    /* 111 */ "SequenceTest"     OpHelp("if( cursor[P1].ctr++ ) pc = P2"),
    /* 112 */ "OpenPseudo"       OpHelp("P3 columns in r[P2]"),
    /* 113 */ "Close"            OpHelp(""),
    /* 114 */ "ColumnsUsed"      OpHelp(""),
    /* 115 */ "Sequence"         OpHelp("r[P2]=cursor[P1].ctr++"),
    /* 116 */ "NewRowid"         OpHelp("r[P2]=rowid"),
    /* 117 */ "Insert"           OpHelp("intkey=r[P3] data=r[P2]"),
    /* 118 */ "InsertInt"        OpHelp("intkey=P3 data=r[P2]"),
    /* 119 */ "Delete"           OpHelp(""),
    /* 120 */ "ResetCount"       OpHelp(""),
    /* 121 */ "SorterCompare"    OpHelp("if key(P1)!=trim(r[P3],P4) goto P2"),
    /* 122 */ "SorterData"       OpHelp("r[P2]=data"),
    /* 123 */ "RowData"          OpHelp("r[P2]=data"),
    /* 124 */ "Rowid"            OpHelp("r[P2]=rowid"),
    /* 125 */ "NullRow"          OpHelp(""),
    /* 126 */ "SeekEnd"          OpHelp(""),
    /* 127 */ "SorterInsert"     OpHelp("key=r[P2]"),
    /* 128 */ "IdxInsert"        OpHelp("key=r[P2]"),
    /* 129 */ "IdxDelete"        OpHelp("key=r[P2@P3]"),
    /* 130 */ "DeferredSeek"     OpHelp("Move P3 to P1.rowid if needed"),
    /* 131 */ "IdxRowid"         OpHelp("r[P2]=rowid"),
    /* 131 */ "Destroy"          OpHelp(""),
    /* 132 */ "Real"             OpHelp("r[P2]=P4"),
    /* 133 */ "Destroy"          OpHelp(""),
    /* 133 */ "Clear"            OpHelp(""),
    /* 134 */ "ResetSorter"      OpHelp(""),
    /* 135 */ "CreateBtree"      OpHelp("r[P2]=root iDb=P1 flags=P3"),
    /* 136 */ "SqlExec"          OpHelp(""),
    /* 137 */ "ParseSchema"      OpHelp(""),
    /* 138 */ "LoadAnalysis"     OpHelp(""),
    /* 139 */ "DropTable"        OpHelp(""),
    /* 140 */ "DropIndex"        OpHelp(""),
    /* 141 */ "DropTrigger"      OpHelp(""),
    /* 142 */ "IntegrityCk"      OpHelp(""),
    /* 143 */ "RowSetAdd"        OpHelp("rowset(P1)=r[P2]"),
    /* 144 */ "Param"            OpHelp(""),
    /* 145 */ "FkCounter"        OpHelp("fkctr[P1]+=P2"),
    /* 146 */ "MemMax"           OpHelp("r[P1]=max(r[P1],r[P2])"),
    /* 147 */ "OffsetLimit"      OpHelp("if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1)"),
    /* 148 */ "AggStep0"         OpHelp("accum=r[P3] step(r[P2@P5])"),
    /* 149 */ "AggStep"          OpHelp("accum=r[P3] step(r[P2@P5])"),
    /* 150 */ "AggFinal"         OpHelp("accum=r[P1] N=P2"),
    /* 151 */ "Expire"           OpHelp(""),
    /* 152 */ "TableLock"        OpHelp("iDb=P1 root=P2 write=P3"),
    /* 153 */ "VBegin"           OpHelp(""),
    /* 154 */ "VCreate"          OpHelp(""),
    /* 155 */ "VDestroy"         OpHelp(""),
    /* 156 */ "VOpen"            OpHelp(""),
    /* 157 */ "VColumn"          OpHelp("r[P3]=vcolumn(P2)"),
    /* 158 */ "VRename"          OpHelp(""),
    /* 159 */ "Pagecount"        OpHelp(""),
    /* 160 */ "MaxPgcnt"         OpHelp(""),
    /* 161 */ "PureFunc0"        OpHelp(""),
    /* 162 */ "Function0"        OpHelp("r[P3]=func(r[P2@P5])"),
    /* 163 */ "PureFunc"         OpHelp(""),
    /* 164 */ "Function"         OpHelp("r[P3]=func(r[P2@P5])"),
    /* 165 */ "CursorHint"       OpHelp(""),
    /* 166 */ "Noop"             OpHelp(""),
    /* 167 */ "Explain"          OpHelp(""),
    /* 134 */ "Clear"            OpHelp(""),
    /* 135 */ "ResetSorter"      OpHelp(""),
    /* 136 */ "CreateBtree"      OpHelp("r[P2]=root iDb=P1 flags=P3"),
    /* 137 */ "SqlExec"          OpHelp(""),
    /* 138 */ "ParseSchema"      OpHelp(""),
    /* 139 */ "LoadAnalysis"     OpHelp(""),
    /* 140 */ "DropTable"        OpHelp(""),
    /* 141 */ "DropIndex"        OpHelp(""),
    /* 142 */ "DropTrigger"      OpHelp(""),
    /* 143 */ "IntegrityCk"      OpHelp(""),
    /* 144 */ "RowSetAdd"        OpHelp("rowset(P1)=r[P2]"),
    /* 145 */ "Param"            OpHelp(""),
    /* 146 */ "FkCounter"        OpHelp("fkctr[P1]+=P2"),
    /* 147 */ "MemMax"           OpHelp("r[P1]=max(r[P1],r[P2])"),
    /* 148 */ "OffsetLimit"      OpHelp("if r[P1]>0 then r[P2]=r[P1]+max(0,r[P3]) else r[P2]=(-1)"),
    /* 149 */ "AggStep0"         OpHelp("accum=r[P3] step(r[P2@P5])"),
    /* 150 */ "AggStep"          OpHelp("accum=r[P3] step(r[P2@P5])"),
    /* 151 */ "AggFinal"         OpHelp("accum=r[P1] N=P2"),
    /* 152 */ "Expire"           OpHelp(""),
    /* 153 */ "TableLock"        OpHelp("iDb=P1 root=P2 write=P3"),
    /* 154 */ "VBegin"           OpHelp(""),
    /* 155 */ "VCreate"          OpHelp(""),
    /* 156 */ "VDestroy"         OpHelp(""),
    /* 157 */ "VOpen"            OpHelp(""),
    /* 158 */ "VColumn"          OpHelp("r[P3]=vcolumn(P2)"),
    /* 159 */ "VRename"          OpHelp(""),
    /* 160 */ "Pagecount"        OpHelp(""),
    /* 161 */ "MaxPgcnt"         OpHelp(""),
    /* 162 */ "PureFunc0"        OpHelp(""),
    /* 163 */ "Function0"        OpHelp("r[P3]=func(r[P2@P5])"),
    /* 164 */ "PureFunc"         OpHelp(""),
    /* 165 */ "Function"         OpHelp("r[P3]=func(r[P2@P5])"),
    /* 166 */ "Trace"            OpHelp(""),
    /* 167 */ "CursorHint"       OpHelp(""),
    /* 168 */ "Noop"             OpHelp(""),
    /* 169 */ "Explain"          OpHelp(""),
  };
  return azName[i];
}
#endif

/************** End of opcodes.c *********************************************/
/************** Begin file os_unix.c *****************************************/

#define osMmap ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[22].pCurrent)

#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
  { "munmap",       (sqlite3_syscall_ptr)munmap,          0 },
#else
  { "munmap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMunmap ((void*(*)(void*,size_t))aSyscall[23].pCurrent)
#define osMunmap ((int(*)(void*,size_t))aSyscall[23].pCurrent)

#if HAVE_MREMAP && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
#else
  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[24].pCurrent)

#if defined(HAVE_LSTAT)
  { "lstat",         (sqlite3_syscall_ptr)lstat,          0 },
#else
  { "lstat",         (sqlite3_syscall_ptr)0,              0 },
#endif
#define osLstat      ((int(*)(const char*,struct stat*))aSyscall[27].pCurrent)

#if defined(__linux__) && defined(SQLITE_ENABLE_BATCH_ATOMIC_WRITE)
  { "ioctl",         (sqlite3_syscall_ptr)ioctl,          0 },
#else
  { "ioctl",         (sqlite3_syscall_ptr)0,              0 },
#endif
#define osIoctl ((int(*)(int,int,...))aSyscall[28].pCurrent)

}; /* End of the overrideable system calls */


/*
** On some systems, calls to fchown() will trigger a message in a security

  if( pFile->sectorSize == 0 ){
    struct statvfs fsInfo;
       
    /* Set defaults for non-supported filesystems */
    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
    pFile->deviceCharacteristics = 0;
    if( fstatvfs(pFile->h, &fsInfo) == -1 ) {
      return pFile->sectorSize;
      return;
    }

    if( !strcmp(fsInfo.f_basetype, "tmp") ) {
      pFile->sectorSize = fsInfo.f_bsize;
      pFile->deviceCharacteristics =
        SQLITE_IOCAP_ATOMIC4K |       /* All ram filesystem writes are atomic */
        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until

  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
  sqlite3_mutex *mutex;      /* Mutex to access this object */
  char *zFilename;           /* Name of the mmapped file */
  int h;                     /* Open file descriptor */
  int szRegion;              /* Size of shared-memory regions */
  u16 nRegion;               /* Size of array apRegion */
  u8 isReadonly;             /* True if read-only */
  u8 isUnlocked;             /* True if no DMS lock held */
  char **apRegion;           /* Array of mapped shared-memory regions */
  int nRef;                  /* Number of unixShm objects pointing to this */
  unixShm *pFirst;           /* All unixShm objects pointing to this */
#ifdef SQLITE_DEBUG
  u8 exclMask;               /* Mask of exclusive locks held */
  u8 sharedMask;             /* Mask of shared locks held */
  u8 nextShmId;              /* Next available unixShm.id value */

){
  unixShmNode *pShmNode; /* Apply locks to this open shared-memory segment */
  struct flock f;        /* The posix advisory locking structure */
  int rc = SQLITE_OK;    /* Result code form fcntl() */

  /* Access to the unixShmNode object is serialized by the caller */
  pShmNode = pFile->pInode->pShmNode;
  assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
  assert( pShmNode->nRef==0 || sqlite3_mutex_held(pShmNode->mutex) );

  /* Shared locks never span more than one byte */
  assert( n==1 || lockType!=F_RDLCK );

  /* Locks are within range */
  assert( n>=1 && n<=SQLITE_SHM_NLOCK );

      robust_close(pFd, p->h, __LINE__);
      p->h = -1;
    }
    p->pInode->pShmNode = 0;
    sqlite3_free(p);
  }
}

/*
** The DMS lock has not yet been taken on shm file pShmNode. Attempt to
** take it now. Return SQLITE_OK if successful, or an SQLite error
** code otherwise.
**
** If the DMS cannot be locked because this is a readonly_shm=1 
** connection and no other process already holds a lock, return
** SQLITE_READONLY_CANTINIT and set pShmNode->isUnlocked=1.
*/
static int unixLockSharedMemory(unixFile *pDbFd, unixShmNode *pShmNode){
  struct flock lock;
  int rc = SQLITE_OK;

  /* Use F_GETLK to determine the locks other processes are holding
  ** on the DMS byte. If it indicates that another process is holding
  ** a SHARED lock, then this process may also take a SHARED lock
  ** and proceed with opening the *-shm file. 
  **
  ** Or, if no other process is holding any lock, then this process
  ** is the first to open it. In this case take an EXCLUSIVE lock on the
  ** DMS byte and truncate the *-shm file to zero bytes in size. Then
  ** downgrade to a SHARED lock on the DMS byte.
  **
  ** If another process is holding an EXCLUSIVE lock on the DMS byte,
  ** return SQLITE_BUSY to the caller (it will try again). An earlier
  ** version of this code attempted the SHARED lock at this point. But
  ** this introduced a subtle race condition: if the process holding
  ** EXCLUSIVE failed just before truncating the *-shm file, then this
  ** process might open and use the *-shm file without truncating it.
  ** And if the *-shm file has been corrupted by a power failure or
  ** system crash, the database itself may also become corrupt.  */
  lock.l_whence = SEEK_SET;
  lock.l_start = UNIX_SHM_DMS;
  lock.l_len = 1;
  lock.l_type = F_WRLCK;
  if( osFcntl(pShmNode->h, F_GETLK, &lock)!=0 ) {
    rc = SQLITE_IOERR_LOCK;
  }else if( lock.l_type==F_UNLCK ){
    if( pShmNode->isReadonly ){
      pShmNode->isUnlocked = 1;
      rc = SQLITE_READONLY_CANTINIT;
    }else{
      rc = unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1);
      if( rc==SQLITE_OK && robust_ftruncate(pShmNode->h, 0) ){
        rc = unixLogError(SQLITE_IOERR_SHMOPEN,"ftruncate",pShmNode->zFilename);
      }
    }
  }else if( lock.l_type==F_WRLCK ){
    rc = SQLITE_BUSY;
  }

  if( rc==SQLITE_OK ){
    assert( lock.l_type==F_UNLCK || lock.l_type==F_RDLCK );
    rc = unixShmSystemLock(pDbFd, F_RDLCK, UNIX_SHM_DMS, 1);
  }
  return rc;
}

/*
** Open a shared-memory area associated with open database file pDbFd.  
** This particular implementation uses mmapped files.
**
** The file used to implement shared-memory is in the same directory
** as the open database file and has the same name as the open database

** that no other processes are able to read or write the database.  In
** that case, we do not really need shared memory.  No shared memory
** file is created.  The shared memory will be simulated with heap memory.
*/
static int unixOpenSharedMemory(unixFile *pDbFd){
  struct unixShm *p = 0;          /* The connection to be opened */
  struct unixShmNode *pShmNode;   /* The underlying mmapped file */
  int rc;                         /* Result code */
  int rc = SQLITE_OK;             /* Result code */
  unixInodeInfo *pInode;          /* The inode of fd */
  char *zShmFilename;             /* Name of the file used for SHM */
  char *zShm;             /* Name of the file used for SHM */
  int nShmFilename;               /* Size of the SHM filename in bytes */

  /* Allocate space for the new unixShm object. */
  p = sqlite3_malloc64( sizeof(*p) );
  if( p==0 ) return SQLITE_NOMEM_BKPT;
  memset(p, 0, sizeof(*p));
  assert( pDbFd->pShm==0 );

#endif
    pShmNode = sqlite3_malloc64( sizeof(*pShmNode) + nShmFilename );
    if( pShmNode==0 ){
      rc = SQLITE_NOMEM_BKPT;
      goto shm_open_err;
    }
    memset(pShmNode, 0, sizeof(*pShmNode)+nShmFilename);
    zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
    zShm = pShmNode->zFilename = (char*)&pShmNode[1];
#ifdef SQLITE_SHM_DIRECTORY
    sqlite3_snprintf(nShmFilename, zShmFilename, 
    sqlite3_snprintf(nShmFilename, zShm, 
                     SQLITE_SHM_DIRECTORY "/sqlite-shm-%x-%x",
                     (u32)sStat.st_ino, (u32)sStat.st_dev);
#else
    sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", zBasePath);
    sqlite3FileSuffix3(pDbFd->zPath, zShmFilename);
    sqlite3_snprintf(nShmFilename, zShm, "%s-shm", zBasePath);
    sqlite3FileSuffix3(pDbFd->zPath, zShm);
#endif
    pShmNode->h = -1;
    pDbFd->pInode->pShmNode = pShmNode;
    pShmNode->pInode = pDbFd->pInode;
    if( sqlite3GlobalConfig.bCoreMutex ){
      pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
      if( pShmNode->mutex==0 ){
        rc = SQLITE_NOMEM_BKPT;
        goto shm_open_err;
      }
    }

    if( pInode->bProcessLock==0 ){
      int openFlags = O_RDWR | O_CREAT;
      if( sqlite3_uri_boolean(pDbFd->zPath, "readonly_shm", 0) ){
      if( 0==sqlite3_uri_boolean(pDbFd->zPath, "readonly_shm", 0) ){
        openFlags = O_RDONLY;
        pShmNode->isReadonly = 1;
        pShmNode->h = robust_open(zShm, O_RDWR|O_CREAT, (sStat.st_mode&0777));
      }
      if( pShmNode->h<0 ){
      pShmNode->h = robust_open(zShmFilename, openFlags, (sStat.st_mode&0777));
      if( pShmNode->h<0 ){
        rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShmFilename);
        goto shm_open_err;
        pShmNode->h = robust_open(zShm, O_RDONLY, (sStat.st_mode&0777));
        if( pShmNode->h<0 ){
          rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShm);
          goto shm_open_err;
        }
        pShmNode->isReadonly = 1;
      }

      /* If this process is running as root, make sure that the SHM file
      ** is owned by the same user that owns the original database.  Otherwise,
      ** the original owner will not be able to connect.
      */
      robustFchown(pShmNode->h, sStat.st_uid, sStat.st_gid);
  

      /* Check to see if another process is holding the dead-man switch.
      ** If not, truncate the file to zero length. 
      */
      rc = SQLITE_OK;
      if( unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
        if( robust_ftruncate(pShmNode->h, 0) ){
          rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename);
      rc = unixLockSharedMemory(pDbFd, pShmNode);
        }
      }
      if( rc==SQLITE_OK ){
        rc = unixShmSystemLock(pDbFd, F_RDLCK, UNIX_SHM_DMS, 1);
      }
      if( rc ) goto shm_open_err;
      if( rc!=SQLITE_OK && rc!=SQLITE_READONLY_CANTINIT ) goto shm_open_err;
    }
  }

  /* Make the new connection a child of the unixShmNode */
  p->pShmNode = pShmNode;
#ifdef SQLITE_DEBUG
  p->id = pShmNode->nextShmId++;

  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex 
  ** mutex.
  */
  sqlite3_mutex_enter(pShmNode->mutex);
  p->pNext = pShmNode->pFirst;
  pShmNode->pFirst = p;
  sqlite3_mutex_leave(pShmNode->mutex);
  return SQLITE_OK;
  return rc;

  /* Jump here on any error */
shm_open_err:
  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
  sqlite3_free(p);
  unixLeaveMutex();
  return rc;

    rc = unixOpenSharedMemory(pDbFd);
    if( rc!=SQLITE_OK ) return rc;
  }

  p = pDbFd->pShm;
  pShmNode = p->pShmNode;
  sqlite3_mutex_enter(pShmNode->mutex);
  if( pShmNode->isUnlocked ){
    rc = unixLockSharedMemory(pDbFd, pShmNode);
    if( rc!=SQLITE_OK ) goto shmpage_out;
    pShmNode->isUnlocked = 0;
  }
  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
  assert( pShmNode->pInode==pDbFd->pInode );
  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );

  /* Minimum number of regions required to be mapped. */
  nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;

  struct statfs fsInfo;
#endif

  /* If creating a master or main-file journal, this function will open
  ** a file-descriptor on the directory too. The first time unixSync()
  ** is called the directory file descriptor will be fsync()ed and close()d.
  */
  int syncDir = (isCreate && (
  int isNewJrnl = (isCreate && (
        eType==SQLITE_OPEN_MASTER_JOURNAL 
     || eType==SQLITE_OPEN_MAIN_JOURNAL 
     || eType==SQLITE_OPEN_WAL
  ));

  /* If argument zPath is a NULL pointer, this function is required to open
  ** a temporary file. Use this buffer to store the file name in.

    /* Database filenames are double-zero terminated if they are not
    ** URIs with parameters.  Hence, they can always be passed into
    ** sqlite3_uri_parameter(). */
    assert( (flags & SQLITE_OPEN_URI) || zName[strlen(zName)+1]==0 );

  }else if( !zName ){
    /* If zName is NULL, the upper layer is requesting a temp file. */
    assert(isDelete && !syncDir);
    assert(isDelete && !isNewJrnl);
    rc = unixGetTempname(pVfs->mxPathname, zTmpname);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    zName = zTmpname;

    /* Generated temporary filenames are always double-zero terminated

      assert( !p->pPreallocatedUnused );
      assert( eType==SQLITE_OPEN_WAL || eType==SQLITE_OPEN_MAIN_JOURNAL );
      return rc;
    }
    fd = robust_open(zName, openFlags, openMode);
    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
    assert( !isExclusive || (openFlags & O_CREAT)!=0 );
    if( fd<0 ){
      if( isNewJrnl && errno==EACCES && osAccess(zName, F_OK) ){
        /* If unable to create a journal because the directory is not
        ** writable, change the error code to indicate that. */
        rc = SQLITE_READONLY_DIRECTORY;
    if( fd<0 && errno!=EISDIR && isReadWrite ){
      /* Failed to open the file for read/write access. Try read-only. */
      flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
      openFlags &= ~(O_RDWR|O_CREAT);
      flags |= SQLITE_OPEN_READONLY;
      openFlags |= O_RDONLY;
      isReadonly = 1;
      fd = robust_open(zName, openFlags, openMode);
    }
      }else if( errno!=EISDIR && isReadWrite ){
        /* Failed to open the file for read/write access. Try read-only. */
        flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
        openFlags &= ~(O_RDWR|O_CREAT);
        flags |= SQLITE_OPEN_READONLY;
        openFlags |= O_RDONLY;
        isReadonly = 1;
        fd = robust_open(zName, openFlags, openMode);
      }
    }
    if( fd<0 ){
      rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zName);
      int rc2 = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zName);
      if( rc==SQLITE_OK ) rc = rc2;
      goto open_finished;
    }

    /* If this process is running as root and if creating a new rollback
    ** journal or WAL file, set the ownership of the journal or WAL to be
    ** the same as the original database.
    */

#endif

  /* Set up appropriate ctrlFlags */
  if( isDelete )                ctrlFlags |= UNIXFILE_DELETE;
  if( isReadonly )              ctrlFlags |= UNIXFILE_RDONLY;
  noLock = eType!=SQLITE_OPEN_MAIN_DB;
  if( noLock )                  ctrlFlags |= UNIXFILE_NOLOCK;
  if( syncDir )                 ctrlFlags |= UNIXFILE_DIRSYNC;
  if( isNewJrnl )               ctrlFlags |= UNIXFILE_DIRSYNC;
  if( flags & SQLITE_OPEN_URI ) ctrlFlags |= UNIXFILE_URI;

#if SQLITE_ENABLE_LOCKING_STYLE
#if SQLITE_PREFER_PROXY_LOCKING
  isAutoProxy = 1;
#endif
  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){

struct winShmNode {
  sqlite3_mutex *mutex;      /* Mutex to access this object */
  char *zFilename;           /* Name of the file */
  winFile hFile;             /* File handle from winOpen */

  int szRegion;              /* Size of shared-memory regions */
  int nRegion;               /* Size of array apRegion */
  u8 isReadonly;             /* True if read-only */
  u8 isUnlocked;             /* True if no DMS lock held */

  struct ShmRegion {
    HANDLE hMap;             /* File handle from CreateFileMapping */
    void *pMap;
  } *aRegion;
  DWORD lastErrno;           /* The Windows errno from the last I/O error */

  int nRef;                  /* Number of winShm objects pointing to this */

  int lockType,         /* WINSHM_UNLCK, WINSHM_RDLCK, or WINSHM_WRLCK */
  int ofst,             /* Offset to first byte to be locked/unlocked */
  int nByte             /* Number of bytes to lock or unlock */
){
  int rc = 0;           /* Result code form Lock/UnlockFileEx() */

  /* Access to the winShmNode object is serialized by the caller */
  assert( sqlite3_mutex_held(pFile->mutex) || pFile->nRef==0 );
  assert( pFile->nRef==0 || sqlite3_mutex_held(pFile->mutex) );

  OSTRACE(("SHM-LOCK file=%p, lock=%d, offset=%d, size=%d\n",
           pFile->hFile.h, lockType, ofst, nByte));

  /* Release/Acquire the system-level lock */
  if( lockType==WINSHM_UNLCK ){
    rc = winUnlockFile(&pFile->hFile.h, ofst, 0, nByte, 0);

      sqlite3_free(p->aRegion);
      sqlite3_free(p);
    }else{
      pp = &p->pNext;
    }
  }
}

/*
** The DMS lock has not yet been taken on shm file pShmNode. Attempt to
** take it now. Return SQLITE_OK if successful, or an SQLite error
** code otherwise.
**
** If the DMS cannot be locked because this is a readonly_shm=1
** connection and no other process already holds a lock, return
** SQLITE_READONLY_CANTINIT and set pShmNode->isUnlocked=1.
*/
static int winLockSharedMemory(winShmNode *pShmNode){
  int rc = winShmSystemLock(pShmNode, WINSHM_WRLCK, WIN_SHM_DMS, 1);

  if( rc==SQLITE_OK ){
    if( pShmNode->isReadonly ){
      pShmNode->isUnlocked = 1;
      winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
      return SQLITE_READONLY_CANTINIT;
    }else if( winTruncate((sqlite3_file*)&pShmNode->hFile, 0) ){
      winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
      return winLogError(SQLITE_IOERR_SHMOPEN, osGetLastError(),
                         "winLockSharedMemory", pShmNode->zFilename);
    }
  }

  if( rc==SQLITE_OK ){
    winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
  }

  return winShmSystemLock(pShmNode, WINSHM_RDLCK, WIN_SHM_DMS, 1);
}

/*
** Open the shared-memory area associated with database file pDbFd.
**
** When opening a new shared-memory file, if no other instances of that
** file are currently open, in this process or in other processes, then
** the file must be truncated to zero length or have its header cleared.
*/
static int winOpenSharedMemory(winFile *pDbFd){
  struct winShm *p;                  /* The connection to be opened */
  struct winShmNode *pShmNode = 0;   /* The underlying mmapped file */
  int rc;                            /* Result code */
  struct winShmNode *pNew;           /* Newly allocated winShmNode */
  winShmNode *pShmNode = 0;          /* The underlying mmapped file */
  int rc = SQLITE_OK;                /* Result code */
  winShmNode *pNew;                  /* Newly allocated winShmNode */
  int nName;                         /* Size of zName in bytes */

  assert( pDbFd->pShm==0 );    /* Not previously opened */

  /* Allocate space for the new sqlite3_shm object.  Also speculatively
  ** allocate space for a new winShmNode and filename.
  */

    ** use FILE_ID_BOTH_DIR_INFO Structure.
    */
    if( sqlite3StrICmp(pShmNode->zFilename, pNew->zFilename)==0 ) break;
  }
  if( pShmNode ){
    sqlite3_free(pNew);
  }else{
    int inFlags = SQLITE_OPEN_WAL;
    int outFlags = 0;

    pShmNode = pNew;
    pNew = 0;
    ((winFile*)(&pShmNode->hFile))->h = INVALID_HANDLE_VALUE;
    pShmNode->pNext = winShmNodeList;
    winShmNodeList = pShmNode;

    if( sqlite3GlobalConfig.bCoreMutex ){
      pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
      if( pShmNode->mutex==0 ){
        rc = SQLITE_IOERR_NOMEM_BKPT;
        goto shm_open_err;
      }
    }

    rc = winOpen(pDbFd->pVfs,
    if( 0==sqlite3_uri_boolean(pDbFd->zPath, "readonly_shm", 0) ){
                 pShmNode->zFilename,             /* Name of the file (UTF-8) */
                 (sqlite3_file*)&pShmNode->hFile,  /* File handle here */
                 SQLITE_OPEN_WAL | SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE,
      inFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE;
                 0);
    if( SQLITE_OK!=rc ){
    }else{
      inFlags |= SQLITE_OPEN_READONLY;
      goto shm_open_err;
    }

    rc = winOpen(pDbFd->pVfs, pShmNode->zFilename,
    /* Check to see if another process is holding the dead-man switch.
    ** If not, truncate the file to zero length.
    */
    if( winShmSystemLock(pShmNode, WINSHM_WRLCK, WIN_SHM_DMS, 1)==SQLITE_OK ){
      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, 0);
      if( rc!=SQLITE_OK ){
        rc = winLogError(SQLITE_IOERR_SHMOPEN, osGetLastError(),
                         "winOpenShm", pDbFd->zPath);
      }
                 (sqlite3_file*)&pShmNode->hFile,
                 inFlags, &outFlags);
    if( rc!=SQLITE_OK ){
      rc = winLogError(rc, osGetLastError(), "winOpenShm",
                       pShmNode->zFilename);
      goto shm_open_err;
    }
    }
    if( rc==SQLITE_OK ){
    if( outFlags==SQLITE_OPEN_READONLY ) pShmNode->isReadonly = 1;
      winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
      rc = winShmSystemLock(pShmNode, WINSHM_RDLCK, WIN_SHM_DMS, 1);
    }
    if( rc ) goto shm_open_err;

    rc = winLockSharedMemory(pShmNode);
    if( rc!=SQLITE_OK && rc!=SQLITE_READONLY_CANTINIT ) goto shm_open_err;
  }

  /* Make the new connection a child of the winShmNode */
  p->pShmNode = pShmNode;
#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
  p->id = pShmNode->nextShmId++;
#endif

  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex
  ** mutex.
  */
  sqlite3_mutex_enter(pShmNode->mutex);
  p->pNext = pShmNode->pFirst;
  pShmNode->pFirst = p;
  sqlite3_mutex_leave(pShmNode->mutex);
  return SQLITE_OK;
  return rc;

  /* Jump here on any error */
shm_open_err:
  winShmSystemLock(pShmNode, WINSHM_UNLCK, WIN_SHM_DMS, 1);
  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
  sqlite3_free(p);
  sqlite3_free(pNew);

  int szRegion,                   /* Size of regions */
  int isWrite,                    /* True to extend file if necessary */
  void volatile **pp              /* OUT: Mapped memory */
){
  winFile *pDbFd = (winFile*)fd;
  winShm *pShm = pDbFd->pShm;
  winShmNode *pShmNode;
  DWORD protect = PAGE_READWRITE;
  DWORD flags = FILE_MAP_WRITE | FILE_MAP_READ;
  int rc = SQLITE_OK;

  if( !pShm ){
    rc = winOpenSharedMemory(pDbFd);
    if( rc!=SQLITE_OK ) return rc;
    pShm = pDbFd->pShm;
  }
  pShmNode = pShm->pShmNode;

  sqlite3_mutex_enter(pShmNode->mutex);
  if( pShmNode->isUnlocked ){
    rc = winLockSharedMemory(pShmNode);
    if( rc!=SQLITE_OK ) goto shmpage_out;
    pShmNode->isUnlocked = 0;
  }
  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );

  if( pShmNode->nRegion<=iRegion ){
    struct ShmRegion *apNew;           /* New aRegion[] array */
    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
    sqlite3_int64 sz;                  /* Current size of wal-index file */

        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])
    );
    if( !apNew ){
      rc = SQLITE_IOERR_NOMEM_BKPT;
      goto shmpage_out;
    }
    pShmNode->aRegion = apNew;

    if( pShmNode->isReadonly ){
      protect = PAGE_READONLY;
      flags = FILE_MAP_READ;
    }

    while( pShmNode->nRegion<=iRegion ){
      HANDLE hMap = NULL;         /* file-mapping handle */
      void *pMap = 0;             /* Mapped memory region */

#if SQLITE_OS_WINRT
      hMap = osCreateFileMappingFromApp(pShmNode->hFile.h,
          NULL, PAGE_READWRITE, nByte, NULL
          NULL, protect, nByte, NULL
      );
#elif defined(SQLITE_WIN32_HAS_WIDE)
      hMap = osCreateFileMappingW(pShmNode->hFile.h,
          NULL, PAGE_READWRITE, 0, nByte, NULL
          NULL, protect, 0, nByte, NULL
      );
#elif defined(SQLITE_WIN32_HAS_ANSI) && SQLITE_WIN32_CREATEFILEMAPPINGA
      hMap = osCreateFileMappingA(pShmNode->hFile.h,
          NULL, PAGE_READWRITE, 0, nByte, NULL
          NULL, protect, 0, nByte, NULL
      );
#endif
      OSTRACE(("SHM-MAP-CREATE pid=%lu, region=%d, size=%d, rc=%s\n",
               osGetCurrentProcessId(), pShmNode->nRegion, nByte,
               hMap ? "ok" : "failed"));
      if( hMap ){
        int iOffset = pShmNode->nRegion*szRegion;
        int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
#if SQLITE_OS_WINRT
        pMap = osMapViewOfFileFromApp(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
        pMap = osMapViewOfFileFromApp(hMap, flags,
            iOffset - iOffsetShift, szRegion + iOffsetShift
        );
#else
        pMap = osMapViewOfFile(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
        pMap = osMapViewOfFile(hMap, flags,
            0, iOffset - iOffsetShift, szRegion + iOffsetShift
        );
#endif
        OSTRACE(("SHM-MAP-MAP pid=%lu, region=%d, offset=%d, size=%d, rc=%s\n",
                 osGetCurrentProcessId(), pShmNode->nRegion, iOffset,
                 szRegion, pMap ? "ok" : "failed"));
      }

    int iOffset = iRegion*szRegion;
    int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
    char *p = (char *)pShmNode->aRegion[iRegion].pMap;
    *pp = (void *)&p[iOffsetShift];
  }else{
    *pp = 0;
  }
  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
  sqlite3_mutex_leave(pShmNode->mutex);
  return rc;
}

#else
# define winShmMap     0
# define winShmLock    0

      h = osCreateFile2((LPCWSTR)zConverted,
                        dwDesiredAccess,
                        dwShareMode,
                        dwCreationDisposition,
                        &extendedParameters);
      if( h!=INVALID_HANDLE_VALUE ) break;
      if( isReadWrite ){
        int isRO = 0;
        int rc2 = winAccess(pVfs, zName, SQLITE_ACCESS_READ, &isRO);
        int rc2, isRO = 0;
        sqlite3BeginBenignMalloc();
        rc2 = winAccess(pVfs, zName, SQLITE_ACCESS_READ, &isRO);
        sqlite3EndBenignMalloc();
        if( rc2==SQLITE_OK && isRO ) break;
      }
    }while( winRetryIoerr(&cnt, &lastErrno) );
#else
    do{
      h = osCreateFileW((LPCWSTR)zConverted,
                        dwDesiredAccess,
                        dwShareMode, NULL,
                        dwCreationDisposition,
                        dwFlagsAndAttributes,
                        NULL);
      if( h!=INVALID_HANDLE_VALUE ) break;
      if( isReadWrite ){
        int isRO = 0;
        int rc2 = winAccess(pVfs, zName, SQLITE_ACCESS_READ, &isRO);
        int rc2, isRO = 0;
        sqlite3BeginBenignMalloc();
        rc2 = winAccess(pVfs, zName, SQLITE_ACCESS_READ, &isRO);
        sqlite3EndBenignMalloc();
        if( rc2==SQLITE_OK && isRO ) break;
      }
    }while( winRetryIoerr(&cnt, &lastErrno) );
#endif
  }
#ifdef SQLITE_WIN32_HAS_ANSI
  else{
    do{
      h = osCreateFileA((LPCSTR)zConverted,
                        dwDesiredAccess,
                        dwShareMode, NULL,
                        dwCreationDisposition,
                        dwFlagsAndAttributes,
                        NULL);
      if( h!=INVALID_HANDLE_VALUE ) break;
      if( isReadWrite ){
        int isRO = 0;
        int rc2 = winAccess(pVfs, zName, SQLITE_ACCESS_READ, &isRO);
        int rc2, isRO = 0;
        sqlite3BeginBenignMalloc();
        rc2 = winAccess(pVfs, zName, SQLITE_ACCESS_READ, &isRO);
        sqlite3EndBenignMalloc();
        if( rc2==SQLITE_OK && isRO ) break;
      }
    }while( winRetryIoerr(&cnt, &lastErrno) );
  }
#endif
  winLogIoerr(cnt, __LINE__);

/*
** Make sure the page is marked as clean. If it isn't clean already,
** make it so.
*/
SQLITE_PRIVATE void sqlite3PcacheMakeClean(PgHdr *p){
  assert( sqlite3PcachePageSanity(p) );
  if( ALWAYS((p->flags & PGHDR_DIRTY)!=0) ){
    assert( (p->flags & PGHDR_CLEAN)==0 );
    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
    p->flags |= PGHDR_CLEAN;
    pcacheTrace(("%p.CLEAN %d\n",p->pCache,p->pgno));
    assert( sqlite3PcachePageSanity(p) );
    if( p->nRef==0 ){
      pcacheUnpin(p);
  assert( (p->flags & PGHDR_DIRTY)!=0 );
  assert( (p->flags & PGHDR_CLEAN)==0 );
  pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
  p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
  p->flags |= PGHDR_CLEAN;
  pcacheTrace(("%p.CLEAN %d\n",p->pCache,p->pgno));
  assert( sqlite3PcachePageSanity(p) );
  if( p->nRef==0 ){
    pcacheUnpin(p);
    }
  }
}

/*
** Make every page in the cache clean.
*/
SQLITE_PRIVATE void sqlite3PcacheCleanAll(PCache *pCache){

    );
    if( rc==SQLITE_OK && pData ){
      if( pPager->eState>PAGER_READER || pPager->tempFile ){
        pPg = sqlite3PagerLookup(pPager, pgno);
      }
      if( pPg==0 ){
        rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
     }else{
      }else{
        sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
      }
      if( pPg ){
        assert( rc==SQLITE_OK );
        *ppPage = pPg;
        return SQLITE_OK;
      }

** WAL-INDEX FORMAT
**
** Conceptually, the wal-index is shared memory, though VFS implementations
** might choose to implement the wal-index using a mmapped file.  Because
** the wal-index is shared memory, SQLite does not support journal_mode=WAL 
** on a network filesystem.  All users of the database must be able to
** share memory.
**
** In the default unix and windows implementation, the wal-index is a mmapped
** file whose name is the database name with a "-shm" suffix added.  For that
** reason, the wal-index is sometimes called the "shm" file.
**
** The wal-index is transient.  After a crash, the wal-index can (and should
** be) reconstructed from the original WAL file.  In fact, the VFS is required
** to either truncate or zero the header of the wal-index when the last
** connection to it closes.  Because the wal-index is transient, it can
** use an architecture-specific format; it does not have to be cross-platform.
** Hence, unlike the database and WAL file formats which store all values

** WALINDEX_MAX_VERSION, then no read-transaction is opened and SQLite
** returns SQLITE_CANTOPEN.
*/
#define WAL_MAX_VERSION      3007000
#define WALINDEX_MAX_VERSION 3007000

/*
** Indices of various locking bytes.   WAL_NREADER is the number
** Index numbers for various locking bytes.   WAL_NREADER is the number
** of available reader locks and should be at least 3.  The default
** is SQLITE_SHM_NLOCK==8 and  WAL_NREADER==5.
**
** Technically, the various VFSes are free to implement these locks however
** they see fit.  However, compatibility is encouraged so that VFSes can
** interoperate.  The standard implemention used on both unix and windows
** is for the index number to indicate a byte offset into the
** WalCkptInfo.aLock[] array in the wal-index header.  In other words, all
** locks are on the shm file.  The WALINDEX_LOCK_OFFSET constant (which
** should be 120) is the location in the shm file for the first locking
** byte.
*/
#define WAL_WRITE_LOCK         0
#define WAL_ALL_BUT_WRITE      1
#define WAL_CKPT_LOCK          1
#define WAL_RECOVER_LOCK       2
#define WAL_READ_LOCK(I)       (3+(I))
#define WAL_NREADER            (SQLITE_SHM_NLOCK-3)

#define WALINDEX_LOCK_OFFSET (sizeof(WalIndexHdr)*2+offsetof(WalCkptInfo,aLock))
#define WALINDEX_HDR_SIZE    (sizeof(WalIndexHdr)*2+sizeof(WalCkptInfo))

/* Size of header before each frame in wal */
#define WAL_FRAME_HDRSIZE 24

/* Size of write ahead log header, including checksum. */
/* #define WAL_HDRSIZE 24 */
#define WAL_HDRSIZE 32

/* WAL magic value. Either this value, or the same value with the least
** significant bit also set (WAL_MAGIC | 0x00000001) is stored in 32-bit
** big-endian format in the first 4 bytes of a WAL file.
**
** If the LSB is set, then the checksums for each frame within the WAL

  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
  u8 writeLock;              /* True if in a write transaction */
  u8 ckptLock;               /* True if holding a checkpoint lock */
  u8 readOnly;               /* WAL_RDWR, WAL_RDONLY, or WAL_SHM_RDONLY */
  u8 truncateOnCommit;       /* True to truncate WAL file on commit */
  u8 syncHeader;             /* Fsync the WAL header if true */
  u8 padToSectorBoundary;    /* Pad transactions out to the next sector */
  u8 bShmUnreliable;         /* SHM content is read-only and unreliable */
  WalIndexHdr hdr;           /* Wal-index header for current transaction */
  u32 minFrame;              /* Ignore wal frames before this one */
  u32 iReCksum;              /* On commit, recalculate checksums from here */
  const char *zWalName;      /* Name of WAL file */
  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
#ifdef SQLITE_DEBUG
  u8 lockError;              /* True if a locking error has occurred */

    sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
)

/*
** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
** numbered from zero.
**
** If the wal-index is currently smaller the iPage pages then the size
** of the wal-index might be increased, but only if it is safe to do
** so.  It is safe to enlarge the wal-index if pWal->writeLock is true
** or pWal->exclusiveMode==WAL_HEAPMEMORY_MODE.
**
** If this call is successful, *ppPage is set to point to the wal-index
** page and SQLITE_OK is returned. If an error (an OOM or VFS error) occurs,
** then an SQLite error code is returned and *ppPage is set to 0.
*/
static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
  int rc = SQLITE_OK;

    if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
      pWal->apWiData[iPage] = (u32 volatile *)sqlite3MallocZero(WALINDEX_PGSZ);
      if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM_BKPT;
    }else{
      rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
          pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
      );
      assert( pWal->apWiData[iPage]!=0 || rc!=SQLITE_OK || pWal->writeLock==0 );
      testcase( pWal->apWiData[iPage]==0 && rc==SQLITE_OK );
      if( rc==SQLITE_READONLY ){
      if( (rc&0xff)==SQLITE_READONLY ){
        pWal->readOnly |= WAL_SHM_RDONLY;
        if( rc==SQLITE_READONLY ){
        rc = SQLITE_OK;
          rc = SQLITE_OK;
        }
      }
    }
  }

  *ppPage = pWal->apWiData[iPage];
  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
  return rc;

** the necessary locks, this routine returns SQLITE_BUSY.
*/
static int walIndexRecover(Wal *pWal){
  int rc;                         /* Return Code */
  i64 nSize;                      /* Size of log file */
  u32 aFrameCksum[2] = {0, 0};
  int iLock;                      /* Lock offset to lock for checkpoint */
  int nLock;                      /* Number of locks to hold */

  /* Obtain an exclusive lock on all byte in the locking range not already
  ** locked by the caller. The caller is guaranteed to have locked the
  ** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
  ** If successful, the same bytes that are locked here are unlocked before
  ** this function returns.
  */
  assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
  assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
  assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
  assert( pWal->writeLock );
  iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
  rc = walLockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
  nLock = SQLITE_SHM_NLOCK - iLock;
  rc = walLockExclusive(pWal, iLock, nLock);
  if( rc==SQLITE_OK ){
    rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
    if( rc!=SQLITE_OK ){
      walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
    }
  }
  if( rc ){
    return rc;
  }

  WALTRACE(("WAL%p: recovery begin...\n", pWal));

  memset(&pWal->hdr, 0, sizeof(WalIndexHdr));

  rc = sqlite3OsFileSize(pWal->pWalFd, &nSize);
  if( rc!=SQLITE_OK ){
    goto recovery_error;

          pWal->hdr.mxFrame, pWal->zWalName
      );
    }
  }

recovery_error:
  WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
  walUnlockExclusive(pWal, iLock, nLock);
  walUnlockExclusive(pWal, iLock, WAL_READ_LOCK(0)-iLock);
  walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
  return rc;
}

/*
** Close an open wal-index.
*/
static void walIndexClose(Wal *pWal, int isDelete){
  if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
  if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE || pWal->bShmUnreliable ){
    int i;
    for(i=0; i<pWal->nWiData; i++){
      sqlite3_free((void *)pWal->apWiData[i]);
      pWal->apWiData[i] = 0;
    }
  }else{
  }
  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
    sqlite3OsShmUnmap(pWal->pDbFd, isDelete);
  }
}

/* 
** Open a connection to the WAL file zWalName. The database file must 
** already be opened on connection pDbFd. The buffer that zWalName points

    testcase( pWal->szPage>=65536 );
  }

  /* The header was successfully read. Return zero. */
  return 0;
}

/*
** This is the value that walTryBeginRead returns when it needs to
** be retried.
*/
#define WAL_RETRY  (-1)

/*
** Read the wal-index header from the wal-index and into pWal->hdr.
** If the wal-header appears to be corrupt, try to reconstruct the
** wal-index from the WAL before returning.
**
** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
** changed by this operation.  If pWal->hdr is unchanged, set *pChanged

  /* Ensure that page 0 of the wal-index (the page that contains the 
  ** wal-index header) is mapped. Return early if an error occurs here.
  */
  assert( pChanged );
  rc = walIndexPage(pWal, 0, &page0);
  if( rc!=SQLITE_OK ){
    assert( rc!=SQLITE_READONLY ); /* READONLY changed to OK in walIndexPage */
    if( rc==SQLITE_READONLY_CANTINIT ){
      /* The SQLITE_READONLY_CANTINIT return means that the shared-memory
      ** was openable but is not writable, and this thread is unable to
      ** confirm that another write-capable connection has the shared-memory
      ** open, and hence the content of the shared-memory is unreliable,
      ** since the shared-memory might be inconsistent with the WAL file
      ** and there is no writer on hand to fix it. */
      assert( page0==0 );
      assert( pWal->writeLock==0 );
      assert( pWal->readOnly & WAL_SHM_RDONLY );
      pWal->bShmUnreliable = 1;
      pWal->exclusiveMode = WAL_HEAPMEMORY_MODE;
      *pChanged = 1;
    }else{
    return rc;
  };
  assert( page0 || pWal->writeLock==0 );
      return rc; /* Any other non-OK return is just an error */
    }
  }else{
    /* page0 can be NULL if the SHM is zero bytes in size and pWal->writeLock
    ** is zero, which prevents the SHM from growing */
    testcase( page0!=0 );
  }
  assert( page0!=0 || pWal->writeLock==0 );

  /* If the first page of the wal-index has been mapped, try to read the
  ** wal-index header immediately, without holding any lock. This usually
  ** works, but may fail if the wal-index header is corrupt or currently 
  ** being modified by another thread or process.
  */
  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);

  /* If the first attempt failed, it might have been due to a race
  ** with a writer.  So get a WRITE lock and try again.
  */
  assert( badHdr==0 || pWal->writeLock==0 );
  if( badHdr ){
    if( pWal->readOnly & WAL_SHM_RDONLY ){
    if( pWal->bShmUnreliable==0 && (pWal->readOnly & WAL_SHM_RDONLY) ){
      if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
        walUnlockShared(pWal, WAL_WRITE_LOCK);
        rc = SQLITE_READONLY_RECOVERY;
      }
    }else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1)) ){
      pWal->writeLock = 1;
      if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){

  /* If the header is read successfully, check the version number to make
  ** sure the wal-index was not constructed with some future format that
  ** this version of SQLite cannot understand.
  */
  if( badHdr==0 && pWal->hdr.iVersion!=WALINDEX_MAX_VERSION ){
    rc = SQLITE_CANTOPEN_BKPT;
  }
  if( pWal->bShmUnreliable ){
    if( rc!=SQLITE_OK ){
      walIndexClose(pWal, 0);
      pWal->bShmUnreliable = 0;
      assert( pWal->nWiData>0 && pWal->apWiData[0]==0 );
      /* walIndexRecover() might have returned SHORT_READ if a concurrent
      ** writer truncated the WAL out from under it.  If that happens, it
      ** indicates that a writer has fixed the SHM file for us, so retry */
      if( rc==SQLITE_IOERR_SHORT_READ ) rc = WAL_RETRY;
    }
    pWal->exclusiveMode = WAL_NORMAL_MODE;
  }

  return rc;
}

/*
** Open a transaction in a connection where the shared-memory is read-only
** and where we cannot verify that there is a separate write-capable connection
** on hand to keep the shared-memory up-to-date with the WAL file.
**
** This can happen, for example, when the shared-memory is implemented by
** memory-mapping a *-shm file, where a prior writer has shut down and
** left the *-shm file on disk, and now the present connection is trying
** to use that database but lacks write permission on the *-shm file.
** Other scenarios are also possible, depending on the VFS implementation.
**
** Precondition:
**
**    The *-wal file has been read and an appropriate wal-index has been
**    constructed in pWal->apWiData[] using heap memory instead of shared
**    memory. 
**
** If this function returns SQLITE_OK, then the read transaction has
** been successfully opened. In this case output variable (*pChanged) 
** is set to true before returning if the caller should discard the
** contents of the page cache before proceeding. Or, if it returns 
** WAL_RETRY, then the heap memory wal-index has been discarded and 
** the caller should retry opening the read transaction from the 
** beginning (including attempting to map the *-shm file). 
**
** If an error occurs, an SQLite error code is returned.
*/
static int walBeginShmUnreliable(Wal *pWal, int *pChanged){
  i64 szWal;                      /* Size of wal file on disk in bytes */
  i64 iOffset;                    /* Current offset when reading wal file */
  u8 aBuf[WAL_HDRSIZE];           /* Buffer to load WAL header into */
  u8 *aFrame = 0;                 /* Malloc'd buffer to load entire frame */
  int szFrame;                    /* Number of bytes in buffer aFrame[] */
  u8 *aData;                      /* Pointer to data part of aFrame buffer */
  volatile void *pDummy;          /* Dummy argument for xShmMap */
  int rc;                         /* Return code */
  u32 aSaveCksum[2];              /* Saved copy of pWal->hdr.aFrameCksum */
** This is the value that walTryBeginRead returns when it needs to
** be retried.
*/
#define WAL_RETRY  (-1)

  assert( pWal->bShmUnreliable );
  assert( pWal->readOnly & WAL_SHM_RDONLY );
  assert( pWal->nWiData>0 && pWal->apWiData[0] );

  /* Take WAL_READ_LOCK(0). This has the effect of preventing any
  ** writers from running a checkpoint, but does not stop them
  ** from running recovery.  */
  rc = walLockShared(pWal, WAL_READ_LOCK(0));
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_BUSY ) rc = WAL_RETRY;
    goto begin_unreliable_shm_out;
  }
  pWal->readLock = 0;

  /* Check to see if a separate writer has attached to the shared-memory area,
  ** thus making the shared-memory "reliable" again.  Do this by invoking
  ** the xShmMap() routine of the VFS and looking to see if the return
  ** is SQLITE_READONLY instead of SQLITE_READONLY_CANTINIT.
  **
  ** If the shared-memory is now "reliable" return WAL_RETRY, which will
  ** cause the heap-memory WAL-index to be discarded and the actual
  ** shared memory to be used in its place.
  **
  ** This step is important because, even though this connection is holding
  ** the WAL_READ_LOCK(0) which prevents a checkpoint, a writer might
  ** have already checkpointed the WAL file and, while the current
  ** is active, wrap the WAL and start overwriting frames that this
  ** process wants to use.
  **
  ** Once sqlite3OsShmMap() has been called for an sqlite3_file and has
  ** returned any SQLITE_READONLY value, it must return only SQLITE_READONLY
  ** or SQLITE_READONLY_CANTINIT or some error for all subsequent invocations,
  ** even if some external agent does a "chmod" to make the shared-memory
  ** writable by us, until sqlite3OsShmUnmap() has been called.
  ** This is a requirement on the VFS implementation.
   */
  rc = sqlite3OsShmMap(pWal->pDbFd, 0, WALINDEX_PGSZ, 0, &pDummy);
  assert( rc!=SQLITE_OK ); /* SQLITE_OK not possible for read-only connection */
  if( rc!=SQLITE_READONLY_CANTINIT ){
    rc = (rc==SQLITE_READONLY ? WAL_RETRY : rc);
    goto begin_unreliable_shm_out;
  }

  /* We reach this point only if the real shared-memory is still unreliable.
  ** Assume the in-memory WAL-index substitute is correct and load it
  ** into pWal->hdr.
  */
  memcpy(&pWal->hdr, (void*)walIndexHdr(pWal), sizeof(WalIndexHdr));

  /* Make sure some writer hasn't come in and changed the WAL file out
  ** from under us, then disconnected, while we were not looking.
  */
  rc = sqlite3OsFileSize(pWal->pWalFd, &szWal);
  if( rc!=SQLITE_OK ){
    goto begin_unreliable_shm_out;
  }
  if( szWal<WAL_HDRSIZE ){
    /* If the wal file is too small to contain a wal-header and the
    ** wal-index header has mxFrame==0, then it must be safe to proceed
    ** reading the database file only. However, the page cache cannot
    ** be trusted, as a read/write connection may have connected, written
    ** the db, run a checkpoint, truncated the wal file and disconnected
    ** since this client's last read transaction.  */
    *pChanged = 1;
    rc = (pWal->hdr.mxFrame==0 ? SQLITE_OK : WAL_RETRY);
    goto begin_unreliable_shm_out;
  }

  /* Check the salt keys at the start of the wal file still match. */
  rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
  if( rc!=SQLITE_OK ){
    goto begin_unreliable_shm_out;
  }
  if( memcmp(&pWal->hdr.aSalt, &aBuf[16], 8) ){
    /* Some writer has wrapped the WAL file while we were not looking.
    ** Return WAL_RETRY which will cause the in-memory WAL-index to be
    ** rebuilt. */
    rc = WAL_RETRY;
    goto begin_unreliable_shm_out;
  }

  /* Allocate a buffer to read frames into */
  szFrame = pWal->hdr.szPage + WAL_FRAME_HDRSIZE;
  aFrame = (u8 *)sqlite3_malloc64(szFrame);
  if( aFrame==0 ){
    rc = SQLITE_NOMEM_BKPT;
    goto begin_unreliable_shm_out;
  }
  aData = &aFrame[WAL_FRAME_HDRSIZE];

  /* Check to see if a complete transaction has been appended to the
  ** wal file since the heap-memory wal-index was created. If so, the
  ** heap-memory wal-index is discarded and WAL_RETRY returned to
  ** the caller.  */
  aSaveCksum[0] = pWal->hdr.aFrameCksum[0];
  aSaveCksum[1] = pWal->hdr.aFrameCksum[1];
  for(iOffset=walFrameOffset(pWal->hdr.mxFrame+1, pWal->hdr.szPage); 
      iOffset+szFrame<=szWal; 
      iOffset+=szFrame
  ){
    u32 pgno;                   /* Database page number for frame */
    u32 nTruncate;              /* dbsize field from frame header */

    /* Read and decode the next log frame. */
    rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
    if( rc!=SQLITE_OK ) break;
    if( !walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame) ) break;

    /* If nTruncate is non-zero, then a complete transaction has been
    ** appended to this wal file. Set rc to WAL_RETRY and break out of
    ** the loop.  */
    if( nTruncate ){
      rc = WAL_RETRY;
      break;
    }
  }
  pWal->hdr.aFrameCksum[0] = aSaveCksum[0];
  pWal->hdr.aFrameCksum[1] = aSaveCksum[1];

 begin_unreliable_shm_out:
  sqlite3_free(aFrame);
  if( rc!=SQLITE_OK ){
    int i;
    for(i=0; i<pWal->nWiData; i++){
      sqlite3_free((void*)pWal->apWiData[i]);
      pWal->apWiData[i] = 0;
    }
    pWal->bShmUnreliable = 0;
    sqlite3WalEndReadTransaction(pWal);
    *pChanged = 1;
  }
  return rc;
}

/*
** Attempt to start a read transaction.  This might fail due to a race or
** other transient condition.  When that happens, it returns WAL_RETRY to
** indicate to the caller that it is safe to retry immediately.
**
** On success return SQLITE_OK.  On a permanent failure (such an
** I/O error or an SQLITE_BUSY because another process is running
** recovery) return a positive error code.
**
** The useWal parameter is true to force the use of the WAL and disable
** the case where the WAL is bypassed because it has been completely
** checkpointed.  If useWal==0 then this routine calls walIndexReadHdr() 
** to make a copy of the wal-index header into pWal->hdr.  If the 
** wal-index header has changed, *pChanged is set to 1 (as an indication 
** to the caller that the local paget cache is obsolete and needs to be 
** to the caller that the local page cache is obsolete and needs to be 
** flushed.)  When useWal==1, the wal-index header is assumed to already
** be loaded and the pChanged parameter is unused.
**
** The caller must set the cnt parameter to the number of prior calls to
** this routine during the current read attempt that returned WAL_RETRY.
** This routine will start taking more aggressive measures to clear the
** race conditions after multiple WAL_RETRY returns, and after an excessive

  int mxI;                        /* Index of largest aReadMark[] value */
  int i;                          /* Loop counter */
  int rc = SQLITE_OK;             /* Return code  */
  u32 mxFrame;                    /* Wal frame to lock to */

  assert( pWal->readLock<0 );     /* Not currently locked */

  /* useWal may only be set for read/write connections */
  assert( (pWal->readOnly & WAL_SHM_RDONLY)==0 || useWal==0 );

  /* Take steps to avoid spinning forever if there is a protocol error.
  **
  ** Circumstances that cause a RETRY should only last for the briefest
  ** instances of time.  No I/O or other system calls are done while the
  ** locks are held, so the locks should not be held for very long. But 
  ** if we are unlucky, another process that is holding a lock might get
  ** paged out or take a page-fault that is time-consuming to resolve, 

      return SQLITE_PROTOCOL;
    }
    if( cnt>=10 ) nDelay = (cnt-9)*(cnt-9)*39;
    sqlite3OsSleep(pWal->pVfs, nDelay);
  }

  if( !useWal ){
    assert( rc==SQLITE_OK );
    if( pWal->bShmUnreliable==0 ){
    rc = walIndexReadHdr(pWal, pChanged);
      rc = walIndexReadHdr(pWal, pChanged);
    }
    if( rc==SQLITE_BUSY ){
      /* If there is not a recovery running in another thread or process
      ** then convert BUSY errors to WAL_RETRY.  If recovery is known to
      ** be running, convert BUSY to BUSY_RECOVERY.  There is a race here
      ** which might cause WAL_RETRY to be returned even if BUSY_RECOVERY
      ** would be technically correct.  But the race is benign since with
      ** WAL_RETRY this routine will be called again and will probably be

      }else if( rc==SQLITE_BUSY ){
        rc = SQLITE_BUSY_RECOVERY;
      }
    }
    if( rc!=SQLITE_OK ){
      return rc;
    }
    else if( pWal->bShmUnreliable ){
      return walBeginShmUnreliable(pWal, pChanged);
  }

    }
  }

  assert( pWal->nWiData>0 );
  assert( pWal->apWiData[0]!=0 );
  pInfo = walCkptInfo(pWal);
  if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame 
  if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame
#ifdef SQLITE_ENABLE_SNAPSHOT
   && (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0
   && (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0)
     || 0==memcmp(&pWal->hdr, pWal->pSnapshot, sizeof(WalIndexHdr)))
#endif
  ){
    /* The WAL has been completely backfilled (or it is empty).
    ** and can be safely ignored.
    */
    rc = walLockShared(pWal, WAL_READ_LOCK(0));
    walShmBarrier(pWal);

      }else if( rc!=SQLITE_BUSY ){
        return rc;
      }
    }
  }
  if( mxI==0 ){
    assert( rc==SQLITE_BUSY || (pWal->readOnly & WAL_SHM_RDONLY)!=0 );
    return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTLOCK;
    return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTINIT;
  }

  rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
  if( rc ){
    return rc==SQLITE_BUSY ? WAL_RETRY : rc;
  }
  /* Now that the read-lock has been obtained, check that neither the

  /* If the "last page" field of the wal-index header snapshot is 0, then
  ** no data will be read from the wal under any circumstances. Return early
  ** in this case as an optimization.  Likewise, if pWal->readLock==0, 
  ** then the WAL is ignored by the reader so return early, as if the 
  ** WAL were empty.
  */
  if( iLast==0 || pWal->readLock==0 ){
  if( iLast==0 || (pWal->readLock==0 && pWal->bShmUnreliable==0) ){
    *piRead = 0;
    return SQLITE_OK;
  }

  /* Search the hash table or tables for an entry matching page number
  ** pgno. Each iteration of the following for() loop searches one
  ** hash table (each hash table indexes up to HASHTABLE_NPAGE frames).

#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
  /* If expensive assert() statements are available, do a linear search
  ** of the wal-index file content. Make sure the results agree with the
  ** result obtained using the hash indexes above.  */
  {
    u32 iRead2 = 0;
    u32 iTest;
    assert( pWal->minFrame>0 );
    for(iTest=iLast; iTest>=pWal->minFrame; iTest--){
    assert( pWal->bShmUnreliable || pWal->minFrame>0 );
    for(iTest=iLast; iTest>=pWal->minFrame && iTest>0; iTest--){
      if( walFramePgno(pWal, iTest)==pgno ){
        iRead2 = iTest;
        break;
      }
    }
    assert( iRead==iRead2 );
  }

  ** locks are taken in this case). Nor should the pager attempt to
  ** upgrade to exclusive-mode following such an error.
  */
  assert( pWal->readLock>=0 || pWal->lockError );
  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );

  if( op==0 ){
    if( pWal->exclusiveMode ){
      pWal->exclusiveMode = 0;
    if( pWal->exclusiveMode!=WAL_NORMAL_MODE ){
      pWal->exclusiveMode = WAL_NORMAL_MODE;
      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){
        pWal->exclusiveMode = 1;
        pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
      }
      rc = pWal->exclusiveMode==0;
      rc = pWal->exclusiveMode==WAL_NORMAL_MODE;
    }else{
      /* Already in locking_mode=NORMAL */
      rc = 0;
    }
  }else if( op>0 ){
    assert( pWal->exclusiveMode==0 );
    assert( pWal->exclusiveMode==WAL_NORMAL_MODE );
    assert( pWal->readLock>=0 );
    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
    pWal->exclusiveMode = 1;
    pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
    rc = 1;
  }else{
    rc = pWal->exclusiveMode==0;
    rc = pWal->exclusiveMode==WAL_NORMAL_MODE;
  }
  return rc;
}

/* 
** Return true if the argument is non-NULL and the WAL module is using
** heap-memory for the wal-index. Otherwise, if the argument is NULL or the

  #define setSharedCacheTableLock(a,b,c) SQLITE_OK
  #define clearAllSharedCacheTableLocks(a)
  #define downgradeAllSharedCacheTableLocks(a)
  #define hasSharedCacheTableLock(a,b,c,d) 1
  #define hasReadConflicts(a, b) 0
#endif

/*
** Implementation of the SQLITE_CORRUPT_PAGE() macro. Takes a single
** (MemPage*) as an argument. The (MemPage*) must not be NULL.
**
** If SQLITE_DEBUG is not defined, then this macro is equivalent to
** SQLITE_CORRUPT_BKPT. Or, if SQLITE_DEBUG is set, then the log message
** normally produced as a side-effect of SQLITE_CORRUPT_BKPT is augmented
** with the page number and filename associated with the (MemPage*).
*/
#ifdef SQLITE_DEBUG
int corruptPageError(int lineno, MemPage *p){
  char *zMsg;
  sqlite3BeginBenignMalloc();
  zMsg = sqlite3_mprintf("database corruption page %d of %s",
      (int)p->pgno, sqlite3PagerFilename(p->pBt->pPager, 0)
  );
  sqlite3EndBenignMalloc();
  if( zMsg ){
    sqlite3ReportError(SQLITE_CORRUPT, lineno, zMsg);
  }
  sqlite3_free(zMsg);
  return SQLITE_CORRUPT_BKPT;
}
# define SQLITE_CORRUPT_PAGE(pMemPage) corruptPageError(__LINE__, pMemPage)
#else
# define SQLITE_CORRUPT_PAGE(pMemPage) SQLITE_CORRUPT_PGNO(pMemPage->pgno)
#endif

#ifndef SQLITE_OMIT_SHARED_CACHE

#ifdef SQLITE_DEBUG
/*
**** This function is only used as part of an assert() statement. ***
**
** Check to see if pBtree holds the required locks to read or write to the 

      if( 0==iFree2 || (data[iFree2]==0 && data[iFree2+1]==0) ){
        u8 *pEnd = &data[cellOffset + nCell*2];
        u8 *pAddr;
        int sz2 = 0;
        int sz = get2byte(&data[iFree+2]);
        int top = get2byte(&data[hdr+5]);
        if( top>=iFree ){
          return SQLITE_CORRUPT_PGNO(pPage->pgno);
          return SQLITE_CORRUPT_PAGE(pPage);
        }
        if( iFree2 ){
          assert( iFree+sz<=iFree2 ); /* Verified by pageFindSlot() */
          sz2 = get2byte(&data[iFree2+2]);
          assert( iFree+sz+sz2+iFree2-(iFree+sz) <= usableSize );
          memmove(&data[iFree+sz+sz2], &data[iFree+sz], iFree2-(iFree+sz));
          sz += sz2;

    pc = get2byte(pAddr);
    testcase( pc==iCellFirst );
    testcase( pc==iCellLast );
    /* These conditions have already been verified in btreeInitPage()
    ** if PRAGMA cell_size_check=ON.
    */
    if( pc<iCellFirst || pc>iCellLast ){
      return SQLITE_CORRUPT_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
    assert( pc>=iCellFirst && pc<=iCellLast );
    size = pPage->xCellSize(pPage, &src[pc]);
    cbrk -= size;
    if( cbrk<iCellFirst || pc+size>usableSize ){
      return SQLITE_CORRUPT_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
    assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
    testcase( cbrk+size==usableSize );
    testcase( pc+size==usableSize );
    put2byte(pAddr, cbrk);
    if( temp==0 ){
      int x;
      if( cbrk==pc ) continue;
      temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
      x = get2byte(&data[hdr+5]);
      memcpy(&temp[x], &data[x], (cbrk+size) - x);
      src = temp;
    }
    memcpy(&data[cbrk], &src[pc], size);
  }
  data[hdr+7] = 0;

 defragment_out:
  if( data[hdr+7]+cbrk-iCellFirst!=pPage->nFree ){
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  assert( cbrk>=iCellFirst );
  put2byte(&data[hdr+5], cbrk);
  data[hdr+1] = 0;
  data[hdr+2] = 0;
  memset(&data[iCellFirst], 0, cbrk-iCellFirst);
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );

    ** 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( (x = size - nByte)>=0 ){
      testcase( x==4 );
      testcase( x==3 );
      if( size+pc > usableSize ){
        *pRc = SQLITE_CORRUPT_PGNO(pPg->pgno);
        *pRc = SQLITE_CORRUPT_PAGE(pPg);
        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]>57 ) return 0;

        /* Remove the slot from the free-list. Update the number of

      return &aData[pc + x];
    }
    iAddr = pc;
    pc = get2byte(&aData[pc]);
    if( pc<iAddr+size ) break;
  }
  if( pc ){
    *pRc = SQLITE_CORRUPT_PGNO(pPg->pgno);
    *pRc = SQLITE_CORRUPT_PAGE(pPg);
  }

  return 0;
}

/*
** Allocate nByte bytes of space from within the B-Tree page passed

  ** integer, so a value of 0 is used in its place. */
  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_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
  }

  /* 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
  ** freelist looking for a free slot big enough to satisfy the request.
  */

  iPtr = hdr + 1;
  if( data[iPtr+1]==0 && data[iPtr]==0 ){
    iFreeBlk = 0;  /* Shortcut for the case when the freelist is empty */
  }else{
    while( (iFreeBlk = get2byte(&data[iPtr]))<iStart ){
      if( iFreeBlk<iPtr+4 ){
        if( iFreeBlk==0 ) break;
        return SQLITE_CORRUPT_PGNO(pPage->pgno);
        return SQLITE_CORRUPT_PAGE(pPage);
      }
      iPtr = iFreeBlk;
    }
    if( iFreeBlk>pPage->pBt->usableSize-4 ){
      return SQLITE_CORRUPT_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
    assert( iFreeBlk>iPtr || iFreeBlk==0 );
  
    /* At this point:
    **    iFreeBlk:   First freeblock after iStart, or zero if none
    **    iPtr:       The address of a pointer to iFreeBlk
    **
    ** Check to see if iFreeBlk should be coalesced onto the end of iStart.
    */
    if( iFreeBlk && iEnd+3>=iFreeBlk ){
      nFrag = iFreeBlk - iEnd;
      if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_PGNO(pPage->pgno);
      if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_PAGE(pPage);
      iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
      if( iEnd > pPage->pBt->usableSize ){
        return SQLITE_CORRUPT_PGNO(pPage->pgno);
        return SQLITE_CORRUPT_PAGE(pPage);
      }
      iSize = iEnd - iStart;
      iFreeBlk = get2byte(&data[iFreeBlk]);
    }
  
    /* If iPtr is another freeblock (that is, if iPtr is not the freelist
    ** pointer in the page header) then check to see if iStart should be
    ** coalesced onto the end of iPtr.
    */
    if( iPtr>hdr+1 ){
      int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
      if( iPtrEnd+3>=iStart ){
        if( iPtrEnd>iStart ) return SQLITE_CORRUPT_PGNO(pPage->pgno);
        if( iPtrEnd>iStart ) return SQLITE_CORRUPT_PAGE(pPage);
        nFrag += iStart - iPtrEnd;
        iSize = iEnd - iPtr;
        iStart = iPtr;
      }
    }
    if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_PGNO(pPage->pgno);
    if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_PAGE(pPage);
    data[hdr+7] -= nFrag;
  }
  x = get2byte(&data[hdr+5]);
  if( iStart<=x ){
    /* The new freeblock is at the beginning of the cell content area,
    ** so just extend the cell content area rather than create another
    ** freelist entry */
    if( iStart<x || iPtr!=hdr+1 ) return SQLITE_CORRUPT_PGNO(pPage->pgno);
    if( iStart<x || iPtr!=hdr+1 ) return SQLITE_CORRUPT_PAGE(pPage);
    put2byte(&data[hdr+1], iFreeBlk);
    put2byte(&data[hdr+5], iEnd);
  }else{
    /* Insert the new freeblock into the freelist */
    put2byte(&data[iPtr], iStart);
  }
  if( pPage->pBt->btsFlags & BTS_FAST_SECURE ){

    pPage->intKeyLeaf = 0;
    pPage->xParseCell = btreeParseCellPtrIndex;
    pPage->maxLocal = pBt->maxLocal;
    pPage->minLocal = pBt->minLocal;
  }else{
    /* EVIDENCE-OF: R-47608-56469 Any other value for the b-tree page type is
    ** an error. */
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  pPage->max1bytePayload = pBt->max1bytePayload;
  return SQLITE_OK;
}

/*
** Initialize the auxiliary information for a disk block.

  pBt = pPage->pBt;
  hdr = pPage->hdrOffset;
  data = pPage->aData;
  /* EVIDENCE-OF: R-28594-02890 The one-byte flag at offset 0 indicating
  ** the b-tree page type. */
  if( decodeFlags(pPage, data[hdr]) ){
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
  pPage->maskPage = (u16)(pBt->pageSize - 1);
  pPage->nOverflow = 0;
  usableSize = pBt->usableSize;
  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. */
  top = get2byteNotZero(&data[hdr+5]);
  /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
  ** number of cells on the page. */
  pPage->nCell = get2byte(&data[hdr+3]);
  if( pPage->nCell>MX_CELL(pBt) ){
    /* To many cells for a single page.  The page must be corrupt */
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  testcase( pPage->nCell==MX_CELL(pBt) );
  /* EVIDENCE-OF: R-24089-57979 If a page contains no cells (which is only
  ** possible for a root page of a table that contains no rows) then the
  ** offset to the cell content area will equal the page size minus the
  ** bytes of reserved space. */
  assert( pPage->nCell>0 || top==usableSize || CORRUPT_DB );

    if( !pPage->leaf ) iCellLast--;
    for(i=0; i<pPage->nCell; i++){
      pc = get2byteAligned(&data[cellOffset+i*2]);
      testcase( pc==iCellFirst );
      testcase( pc==iCellLast );
      if( pc<iCellFirst || pc>iCellLast ){
        return SQLITE_CORRUPT_PGNO(pPage->pgno);
        return SQLITE_CORRUPT_PAGE(pPage);
      }
      sz = pPage->xCellSize(pPage, &data[pc]);
      testcase( pc+sz==usableSize );
      if( pc+sz>usableSize ){
        return SQLITE_CORRUPT_PGNO(pPage->pgno);
        return SQLITE_CORRUPT_PAGE(pPage);
      }
    }
    if( !pPage->leaf ) iCellLast++;
  }  

  /* Compute the total free space on the page
  ** EVIDENCE-OF: R-23588-34450 The two-byte integer at offset 1 gives the
  ** start of the first freeblock on the page, or is zero if there are no
  ** freeblocks. */
  pc = get2byte(&data[hdr+1]);
  nFree = data[hdr+7] + top;  /* Init nFree to non-freeblock free space */
  if( pc>0 ){
    u32 next, size;
    if( pc<iCellFirst ){
      /* EVIDENCE-OF: R-55530-52930 In a well-formed b-tree page, there will
      ** always be at least one cell before the first freeblock.
      */
      return SQLITE_CORRUPT_PGNO(pPage->pgno); 
      return SQLITE_CORRUPT_PAGE(pPage); 
    }
    while( 1 ){
      if( pc>iCellLast ){
        /* Freeblock off the end of the page */
        return SQLITE_CORRUPT_PGNO(pPage->pgno);
        return SQLITE_CORRUPT_PAGE(pPage);
      }
      next = get2byte(&data[pc]);
      size = get2byte(&data[pc+2]);
      nFree = nFree + size;
      if( next<=pc+size+3 ) break;
      pc = next;
    }
    if( next>0 ){
      /* Freeblock not in ascending order */
      return SQLITE_CORRUPT_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
    if( pc+size>(unsigned int)usableSize ){
      /* Last freeblock extends past page end */
      return SQLITE_CORRUPT_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
  }

  /* At this point, nFree contains the sum of the offset to the start
  ** of the cell-content area plus the number of free bytes within
  ** the cell-content area. If this is greater than the usable-size
  ** of the page, then the page must be corrupted. This check also
  ** serves to verify that the offset to the start of the cell-content
  ** area, according to the page header, lies within the page.
  */
  if( nFree>usableSize ){
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  pPage->nFree = (u16)(nFree - iCellFirst);
  pPage->isInit = 1;
  return SQLITE_OK;
}

/*

*/
static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
  if( eType==PTRMAP_OVERFLOW2 ){
    /* The pointer is always the first 4 bytes of the page in this case.  */
    if( get4byte(pPage->aData)!=iFrom ){
      return SQLITE_CORRUPT_PGNO(pPage->pgno);
      return SQLITE_CORRUPT_PAGE(pPage);
    }
    put4byte(pPage->aData, iTo);
  }else{
    int i;
    int nCell;
    int rc;

    rc = pPage->isInit ? SQLITE_OK : 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;
        pPage->xParseCell(pPage, pCell, &info);
        if( info.nLocal<info.nPayload ){
          if( pCell+info.nSize > pPage->aData+pPage->pBt->usableSize ){
            return SQLITE_CORRUPT_PGNO(pPage->pgno);
            return SQLITE_CORRUPT_PAGE(pPage);
          }
          if( iFrom==get4byte(pCell+info.nSize-4) ){
            put4byte(pCell+info.nSize-4, iTo);
            break;
          }
        }
      }else{
        if( get4byte(pCell)==iFrom ){
          put4byte(pCell, iTo);
          break;
        }
      }
    }
  
    if( i==nCell ){
      if( eType!=PTRMAP_BTREE || 
          get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
        return SQLITE_CORRUPT_PGNO(pPage->pgno);
        return SQLITE_CORRUPT_PAGE(pPage);
      }
      put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
    }
  }
  return SQLITE_OK;
}

  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  assert( pCur->curIntKey );
  getCellInfo(pCur);
  return pCur->info.nKey;
}

#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
/*
** Return the offset into the database file for the start of the
** payload to which the cursor is pointing.
*/
SQLITE_PRIVATE i64 sqlite3BtreeOffset(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  getCellInfo(pCur);
  return (i64)pCur->pBt->pageSize*((i64)pCur->pPage->pgno - 1) +
         (i64)(pCur->info.pPayload - pCur->pPage->aData);
}
#endif /* SQLITE_ENABLE_OFFSET_SQL_FUNC */

/*
** Return the number of bytes of payload for the entry that pCur is
** currently pointing to.  For table btrees, this will be the amount
** of data.  For index btrees, this will be the size of the key.
**
** The caller must guarantee that the cursor is pointing to a non-NULL
** valid entry.  In other words, the calling procedure must guarantee

  assert( aPayload > pPage->aData );
  if( (uptr)(aPayload - pPage->aData) > (pBt->usableSize - pCur->info.nLocal) ){
    /* Trying to read or write past the end of the data is an error.  The
    ** conditional above is really:
    **    &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
    ** but is recast into its current form to avoid integer overflow problems
    */
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }

  /* Check if data must be read/written to/from the btree page itself. */
  if( offset<pCur->info.nLocal ){
    int a = amt;
    if( a+offset>pCur->info.nLocal ){
      a = pCur->info.nLocal - offset;

      if( rc ) break;
      iIdx++;
    }
  }

  if( rc==SQLITE_OK && amt>0 ){
    /* Overflow chain ends prematurely */
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  return rc;
}

/*
** Read part of the payload for the row at which that cursor pCur is currently
** pointing.  "amt" bytes will be transferred into pBuf[].  The transfer

  ** Earlier versions of SQLite assumed that this test could not fail
  ** if the root page was already loaded when this function was called (i.e.
  ** if pCur->iPage>=0). But this is not so if the database is corrupted 
  ** in such a way that page pRoot is linked into a second b-tree table 
  ** (or the freelist).  */
  assert( pRoot->intKey==1 || pRoot->intKey==0 );
  if( pRoot->isInit==0 || (pCur->pKeyInfo==0)!=pRoot->intKey ){
    return SQLITE_CORRUPT_PGNO(pCur->pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pCur->pPage);
  }

skip_init:  
  pCur->ix = 0;
  pCur->info.nSize = 0;
  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidNKey|BTCF_ValidOvfl);

    if( xRecordCompare==0 ){
      for(;;){
        i64 nCellKey;
        pCell = findCellPastPtr(pPage, idx);
        if( pPage->intKeyLeaf ){
          while( 0x80 <= *(pCell++) ){
            if( pCell>=pPage->aDataEnd ){
              return SQLITE_CORRUPT_PGNO(pPage->pgno);
              return SQLITE_CORRUPT_PAGE(pPage);
            }
          }
        }
        getVarint(pCell, (u64*)&nCellKey);
        if( nCellKey<intKey ){
          lwr = idx+1;
          if( lwr>upr ){ c = -1; break; }

          pPage->xParseCell(pPage, pCellBody, &pCur->info);
          nCell = (int)pCur->info.nKey;
          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_PGNO(pPage->pgno);
            rc = SQLITE_CORRUPT_PAGE(pPage);
            goto moveto_finish;
          }
          pCellKey = sqlite3Malloc( nCell+18 );
          if( pCellKey==0 ){
            rc = SQLITE_NOMEM_BKPT;
            goto moveto_finish;
          }

  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
  pPage->xParseCell(pPage, pCell, pInfo);
  if( pInfo->nLocal==pInfo->nPayload ){
    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
  }
  if( pCell+pInfo->nSize-1 > pPage->aData+pPage->maskPage ){
    /* Cell extends past end of page */
    return SQLITE_CORRUPT_PGNO(pPage->pgno);
    return SQLITE_CORRUPT_PAGE(pPage);
  }
  ovflPgno = get4byte(pCell + pInfo->nSize - 4);
  pBt = pPage->pBt;
  assert( pBt->usableSize > 4 );
  ovflPageSize = pBt->usableSize - 4;
  nOvfl = (pInfo->nPayload - pInfo->nLocal + ovflPageSize - 1)/ovflPageSize;
  assert( nOvfl>0 || 

  /* Cannot be both MEM_Int and MEM_Real at the same time */
  assert( (p->flags & (MEM_Int|MEM_Real))!=(MEM_Int|MEM_Real) );

  if( p->flags & MEM_Null ){
    /* Cannot be both MEM_Null and some other type */
    assert( (p->flags & (MEM_Int|MEM_Real|MEM_Str|MEM_Blob
                         |MEM_RowSet|MEM_Frame|MEM_Agg|MEM_Zero))==0 );
                         |MEM_RowSet|MEM_Frame|MEM_Agg))==0 );

    /* If MEM_Null is set, then either the value is a pure NULL (the usual
    ** case) or it is a pointer set using sqlite3_bind_pointer() or
    ** sqlite3_result_pointer().  If a pointer, then MEM_Term must also be
    ** set.
    */
    if( (p->flags & (MEM_Term|MEM_Subtype))==(MEM_Term|MEM_Subtype) ){

** This routine calls the finalize method for that function.  The
** result of the aggregate is stored back into pMem.
**
** Return SQLITE_ERROR if the finalizer reports an error.  SQLITE_OK
** otherwise.
*/
SQLITE_PRIVATE int sqlite3VdbeMemFinalize(Mem *pMem, FuncDef *pFunc){
  int rc = SQLITE_OK;
  if( ALWAYS(pFunc && pFunc->xFinalize) ){
    sqlite3_context ctx;
    Mem t;
    assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
    assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
    memset(&ctx, 0, sizeof(ctx));
    memset(&t, 0, sizeof(t));
    t.flags = MEM_Null;
    t.db = pMem->db;
    ctx.pOut = &t;
    ctx.pMem = pMem;
    ctx.pFunc = pFunc;
    pFunc->xFinalize(&ctx); /* IMP: R-24505-23230 */
    assert( (pMem->flags & MEM_Dyn)==0 );
    if( pMem->szMalloc>0 ) sqlite3DbFreeNN(pMem->db, pMem->zMalloc);
    memcpy(pMem, &t, sizeof(t));
    rc = ctx.isError;
  sqlite3_context ctx;
  Mem t;
  assert( pFunc!=0 );
  assert( pFunc->xFinalize!=0 );
  assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
  memset(&ctx, 0, sizeof(ctx));
  memset(&t, 0, sizeof(t));
  t.flags = MEM_Null;
  t.db = pMem->db;
  ctx.pOut = &t;
  ctx.pMem = pMem;
  ctx.pFunc = pFunc;
  pFunc->xFinalize(&ctx); /* IMP: R-24505-23230 */
  assert( (pMem->flags & MEM_Dyn)==0 );
  if( pMem->szMalloc>0 ) sqlite3DbFreeNN(pMem->db, pMem->zMalloc);
  memcpy(pMem, &t, sizeof(t));
  return ctx.isError;
  }
  return rc;
}

/*
** If the memory cell contains a value that must be freed by
** invoking the external callback in Mem.xDel, then this routine
** will free that value.  It also sets Mem.flags to MEM_Null.
**

  sqlite3_value *pVal = 0;
  int negInt = 1;
  const char *zNeg = "";
  int rc = SQLITE_OK;

  assert( pExpr!=0 );
  while( (op = pExpr->op)==TK_UPLUS || op==TK_SPAN ) pExpr = pExpr->pLeft;
#if defined(SQLITE_ENABLE_STAT3_OR_STAT4)
  if( op==TK_REGISTER ) op = pExpr->op2;
#else
  if( NEVER(op==TK_REGISTER) ) op = pExpr->op2;
#endif

  /* Compressed expressions only appear when parsing the DEFAULT clause
  ** on a table column definition, and hence only when pCtx==0.  This
  ** check ensures that an EP_TokenOnly expression is never passed down
  ** into valueFromFunction(). */
  assert( (pExpr->flags & EP_TokenOnly)==0 || pCtx==0 );

  }
#endif

  *ppVal = pVal;
  return rc;

no_mem:
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  if( pCtx==0 || pCtx->pParse->nErr==0 )
#endif
  sqlite3OomFault(db);
    sqlite3OomFault(db);
  sqlite3DbFree(db, zVal);
  assert( *ppVal==0 );
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
  if( pCtx==0 ) sqlite3ValueFree(pVal);
#else
  assert( pCtx==0 ); sqlite3ValueFree(pVal);
#endif

    case P4_FUNCCTX: {
      freeP4FuncCtx(db, (sqlite3_context*)p4);
      break;
    }
    case P4_REAL:
    case P4_INT64:
    case P4_DYNAMIC:
    case P4_DYNBLOB:
    case P4_INTARRAY: {
      sqlite3DbFree(db, p4);
      break;
    }
    case P4_KEYINFO: {
      if( db->pnBytesFreed==0 ) sqlite3KeyInfoUnref((KeyInfo*)p4);
      break;

      sqlite3StrAccumAppend(&x, "]", 1);
      break;
    }
    case P4_SUBPROGRAM: {
      sqlite3XPrintf(&x, "program");
      break;
    }
    case P4_DYNBLOB:
    case P4_ADVANCE: {
      zTemp[0] = 0;
      break;
    }
    case P4_TABLE: {
      sqlite3XPrintf(&x, "%s", pOp->p4.pTab->zName);
      break;

  int nSub = 0;                        /* Number of sub-vdbes seen so far */
  SubProgram **apSub = 0;              /* Array of sub-vdbes */
  Mem *pSub = 0;                       /* Memory cell hold array of subprogs */
  sqlite3 *db = p->db;                 /* The database connection */
  int i;                               /* Loop counter */
  int rc = SQLITE_OK;                  /* Return code */
  Mem *pMem = &p->aMem[1];             /* First Mem of result set */
  int bListSubprogs = (p->explain==1 || (db->flags & SQLITE_TriggerEQP)!=0);
  Op *pOp = 0;

  assert( p->explain );
  assert( p->magic==VDBE_MAGIC_RUN );
  assert( p->rc==SQLITE_OK || p->rc==SQLITE_BUSY || p->rc==SQLITE_NOMEM );

  /* Even though this opcode does not use dynamic strings for
  ** the result, result columns may become dynamic if the user calls
  ** sqlite3_column_text16(), causing a translation to UTF-16 encoding.
  */
  releaseMemArray(pMem, 8);
  p->pResultSet = 0;

  if( p->rc==SQLITE_NOMEM_BKPT ){
  if( p->rc==SQLITE_NOMEM ){
    /* This happens if a malloc() inside a call to sqlite3_column_text() or
    ** sqlite3_column_text16() failed.  */
    sqlite3OomFault(db);
    return SQLITE_ERROR;
  }

  /* When the number of output rows reaches nRow, that means the
  ** listing has finished and sqlite3_step() should return SQLITE_DONE.
  ** nRow is the sum of the number of rows in the main program, plus
  ** the sum of the number of rows in all trigger subprograms encountered
  ** so far.  The nRow value will increase as new trigger subprograms are
  ** encountered, but p->pc will eventually catch up to nRow.
  */
  nRow = p->nOp;
  if( p->explain==1 ){
  if( bListSubprogs ){
    /* The first 8 memory cells are used for the result set.  So we will
    ** commandeer the 9th cell to use as storage for an array of pointers
    ** to trigger subprograms.  The VDBE is guaranteed to have at least 9
    ** cells.  */
    assert( p->nMem>9 );
    pSub = &p->aMem[9];
    if( pSub->flags&MEM_Blob ){
      /* On the first call to sqlite3_step(), pSub will hold a NULL.  It is
      ** initialized to a BLOB by the P4_SUBPROGRAM processing logic below */
      nSub = pSub->n/sizeof(Vdbe*);
      apSub = (SubProgram **)pSub->z;
    }
    for(i=0; i<nSub; i++){
      nRow += apSub[i]->nOp;
    }
  }

  do{
    i = p->pc++;
  }while( i<nRow && p->explain==2 && p->aOp[i].opcode!=OP_Explain );
  if( i>=nRow ){
    p->rc = SQLITE_OK;
    rc = SQLITE_DONE;
    if( i>=nRow ){
      p->rc = SQLITE_OK;
      rc = SQLITE_DONE;
  }else if( db->u1.isInterrupted ){
    p->rc = SQLITE_INTERRUPT;
    rc = SQLITE_ERROR;
    sqlite3VdbeError(p, sqlite3ErrStr(p->rc));
  }else{
      break;
    char *zP4;
    Op *pOp;
    }
    if( i<p->nOp ){
      /* The output line number is small enough that we are still in the
      ** main program. */
      pOp = &p->aOp[i];
    }else{
      /* We are currently listing subprograms.  Figure out which one and
      ** pick up the appropriate opcode. */
      int j;
      i -= p->nOp;
      for(j=0; i>=apSub[j]->nOp; j++){
        i -= apSub[j]->nOp;
      }
      pOp = &apSub[j]->aOp[i];
    }

    /* When an OP_Program opcode is encounter (the only opcode that has
    ** a P4_SUBPROGRAM argument), expand the size of the array of subprograms
    ** kept in p->aMem[9].z to hold the new program - assuming this subprogram
    ** has not already been seen.
    */
    if( bListSubprogs && pOp->p4type==P4_SUBPROGRAM ){
      int nByte = (nSub+1)*sizeof(SubProgram*);
      int j;
      for(j=0; j<nSub; j++){
        if( apSub[j]==pOp->p4.pProgram ) break;
      }
      if( j==nSub ){
        p->rc = sqlite3VdbeMemGrow(pSub, nByte, nSub!=0);
        if( p->rc!=SQLITE_OK ){
          rc = SQLITE_ERROR;
          break;
        }
        apSub = (SubProgram **)pSub->z;
        apSub[nSub++] = pOp->p4.pProgram;
        pSub->flags |= MEM_Blob;
        pSub->n = nSub*sizeof(SubProgram*);
        nRow += pOp->p4.pProgram->nOp;
      }
    }
  }while( p->explain==2 && pOp->opcode!=OP_Explain );

  if( rc==SQLITE_OK ){
    if( db->u1.isInterrupted ){
      p->rc = SQLITE_INTERRUPT;
      rc = SQLITE_ERROR;
      sqlite3VdbeError(p, sqlite3ErrStr(p->rc));
    }else{
      char *zP4;
    if( p->explain==1 ){
      pMem->flags = MEM_Int;
      pMem->u.i = i;                                /* Program counter */
      pMem++;
  
      pMem->flags = MEM_Static|MEM_Str|MEM_Term;
      pMem->z = (char*)sqlite3OpcodeName(pOp->opcode); /* Opcode */
      assert( pMem->z!=0 );
      pMem->n = sqlite3Strlen30(pMem->z);
      pMem->enc = SQLITE_UTF8;
      pMem++;
      if( p->explain==1 ){
        pMem->flags = MEM_Int;
        pMem->u.i = i;                                /* Program counter */
        pMem++;
    
        pMem->flags = MEM_Static|MEM_Str|MEM_Term;
        pMem->z = (char*)sqlite3OpcodeName(pOp->opcode); /* Opcode */
        assert( pMem->z!=0 );
        pMem->n = sqlite3Strlen30(pMem->z);
        pMem->enc = SQLITE_UTF8;
        pMem++;

      /* When an OP_Program opcode is encounter (the only opcode that has
      ** a P4_SUBPROGRAM argument), expand the size of the array of subprograms
      ** kept in p->aMem[9].z to hold the new program - assuming this subprogram
      ** has not already been seen.
      */
      if( pOp->p4type==P4_SUBPROGRAM ){
        int nByte = (nSub+1)*sizeof(SubProgram*);
        int j;
        for(j=0; j<nSub; j++){
          if( apSub[j]==pOp->p4.pProgram ) break;
        }
        if( j==nSub && SQLITE_OK==sqlite3VdbeMemGrow(pSub, nByte, nSub!=0) ){
          apSub = (SubProgram **)pSub->z;
          apSub[nSub++] = pOp->p4.pProgram;
          pSub->flags |= MEM_Blob;
          pSub->n = nSub*sizeof(SubProgram*);
        }
      }
    }
      }

    pMem->flags = MEM_Int;
    pMem->u.i = pOp->p1;                          /* P1 */
    pMem++;
      pMem->flags = MEM_Int;
      pMem->u.i = pOp->p1;                          /* P1 */
      pMem++;

    pMem->flags = MEM_Int;
    pMem->u.i = pOp->p2;                          /* P2 */
    pMem++;
      pMem->flags = MEM_Int;
      pMem->u.i = pOp->p2;                          /* P2 */
      pMem++;

    pMem->flags = MEM_Int;
    pMem->u.i = pOp->p3;                          /* P3 */
    pMem++;
      pMem->flags = MEM_Int;
      pMem->u.i = pOp->p3;                          /* P3 */
      pMem++;

    if( sqlite3VdbeMemClearAndResize(pMem, 100) ){ /* P4 */
      assert( p->db->mallocFailed );
      return SQLITE_ERROR;
    }
    pMem->flags = MEM_Str|MEM_Term;
    zP4 = displayP4(pOp, pMem->z, pMem->szMalloc);
    if( zP4!=pMem->z ){
      pMem->n = 0;
      sqlite3VdbeMemSetStr(pMem, zP4, -1, SQLITE_UTF8, 0);
    }else{
      assert( pMem->z!=0 );
      pMem->n = sqlite3Strlen30(pMem->z);
      pMem->enc = SQLITE_UTF8;
    }
    pMem++;
      if( sqlite3VdbeMemClearAndResize(pMem, 100) ){ /* P4 */
        assert( p->db->mallocFailed );
        return SQLITE_ERROR;
      }
      pMem->flags = MEM_Str|MEM_Term;
      zP4 = displayP4(pOp, pMem->z, pMem->szMalloc);
      if( zP4!=pMem->z ){
        pMem->n = 0;
        sqlite3VdbeMemSetStr(pMem, zP4, -1, SQLITE_UTF8, 0);
      }else{
        assert( pMem->z!=0 );
        pMem->n = sqlite3Strlen30(pMem->z);
        pMem->enc = SQLITE_UTF8;
      }
      pMem++;

    if( p->explain==1 ){
      if( sqlite3VdbeMemClearAndResize(pMem, 4) ){
        assert( p->db->mallocFailed );
        return SQLITE_ERROR;
      }
      pMem->flags = MEM_Str|MEM_Term;
      pMem->n = 2;
      sqlite3_snprintf(3, pMem->z, "%.2x", pOp->p5);   /* P5 */
      pMem->enc = SQLITE_UTF8;
      pMem++;
  
      if( p->explain==1 ){
        if( sqlite3VdbeMemClearAndResize(pMem, 4) ){
          assert( p->db->mallocFailed );
          return SQLITE_ERROR;
        }
        pMem->flags = MEM_Str|MEM_Term;
        pMem->n = 2;
        sqlite3_snprintf(3, pMem->z, "%.2x", pOp->p5);   /* P5 */
        pMem->enc = SQLITE_UTF8;
        pMem++;
    
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
      if( sqlite3VdbeMemClearAndResize(pMem, 500) ){
        assert( p->db->mallocFailed );
        return SQLITE_ERROR;
      }
      pMem->flags = MEM_Str|MEM_Term;
      pMem->n = displayComment(pOp, zP4, pMem->z, 500);
      pMem->enc = SQLITE_UTF8;
        if( sqlite3VdbeMemClearAndResize(pMem, 500) ){
          assert( p->db->mallocFailed );
          return SQLITE_ERROR;
        }
        pMem->flags = MEM_Str|MEM_Term;
        pMem->n = displayComment(pOp, zP4, pMem->z, 500);
        pMem->enc = SQLITE_UTF8;
#else
      pMem->flags = MEM_Null;                       /* Comment */
        pMem->flags = MEM_Null;                       /* Comment */
#endif
    }
      }

    p->nResColumn = 8 - 4*(p->explain-1);
    p->pResultSet = &p->aMem[1];
    p->rc = SQLITE_OK;
    rc = SQLITE_ROW;
      p->nResColumn = 8 - 4*(p->explain-1);
      p->pResultSet = &p->aMem[1];
      p->rc = SQLITE_OK;
      rc = SQLITE_ROW;
    }
  }
  return rc;
}
#endif /* SQLITE_OMIT_EXPLAIN */

#ifdef SQLITE_DEBUG
/*

      };
      Pager *pPager;   /* Pager associated with pBt */
      needXcommit = 1;
      sqlite3BtreeEnter(pBt);
      pPager = sqlite3BtreePager(pBt);
      if( db->aDb[i].safety_level!=PAGER_SYNCHRONOUS_OFF
       && aMJNeeded[sqlite3PagerGetJournalMode(pPager)]
       && sqlite3PagerIsMemdb(pPager)==0
      ){ 
        assert( i!=1 );
        nTrans++;
      }
      rc = sqlite3PagerExclusiveLock(pPager);
      sqlite3BtreeLeave(pBt);
    }

/*
** Delete an entire VDBE.
*/
SQLITE_PRIVATE void sqlite3VdbeDelete(Vdbe *p){
  sqlite3 *db;

  if( NEVER(p==0) ) return;
  assert( p!=0 );
  db = p->db;
  assert( sqlite3_mutex_held(db->mutex) );
  sqlite3VdbeClearObject(db, p);
  if( p->pPrev ){
    p->pPrev->pNext = p->pNext;
  }else{
    assert( db->pVdbe==p );

}
SQLITE_PRIVATE u32 sqlite3VdbeSerialGet(
  const unsigned char *buf,     /* Buffer to deserialize from */
  u32 serial_type,              /* Serial type to deserialize */
  Mem *pMem                     /* Memory cell to write value into */
){
  switch( serial_type ){
    case 10:   /* Reserved for future use */
    case 10: { /* Internal use only: NULL with virtual table
               ** UPDATE no-change flag set */
      pMem->flags = MEM_Null|MEM_Zero;
      pMem->n = 0;
      pMem->u.nZero = 0;
      break;
    }
    case 11:   /* Reserved for future use */
    case 0: {  /* Null */
      /* EVIDENCE-OF: R-24078-09375 Value is a NULL. */
      pMem->flags = MEM_Null;
      break;
    }
    case 1: {

     SQLITE_INTEGER,  /* 0x1c */
     SQLITE_NULL,     /* 0x1d */
     SQLITE_INTEGER,  /* 0x1e */
     SQLITE_NULL,     /* 0x1f */
  };
  return aType[pVal->flags&MEM_AffMask];
}

/* Return true if a parameter to xUpdate represents an unchanged column */
SQLITE_API int sqlite3_value_nochange(sqlite3_value *pVal){
  return (pVal->flags&(MEM_Null|MEM_Zero))==(MEM_Null|MEM_Zero);
}

/* Make a copy of an sqlite3_value object
*/
SQLITE_API sqlite3_value *sqlite3_value_dup(const sqlite3_value *pOrig){
  sqlite3_value *pNew;
  if( pOrig==0 ) return 0;
  pNew = sqlite3_malloc( sizeof(*pNew) );

** sqlite3_create_function16() routines that originally registered the
** application defined function.
*/
SQLITE_API sqlite3 *sqlite3_context_db_handle(sqlite3_context *p){
  assert( p && p->pOut );
  return p->pOut->db;
}

/*
** If this routine is invoked from within an xColumn method of a virtual
** table, then it returns true if and only if the the call is during an
** UPDATE operation and the value of the column will not be modified
** by the UPDATE.
**
** If this routine is called from any context other than within the
** xColumn method of a virtual table, then the return value is meaningless
** and arbitrary.
**
** Virtual table implements might use this routine to optimize their
** performance by substituting a NULL result, or some other light-weight
** value, as a signal to the xUpdate routine that the column is unchanged.
*/
SQLITE_API int sqlite3_vtab_nochange(sqlite3_context *p){
  assert( p );
  return sqlite3_value_nochange(p->pOut);
}

/*
** Return the current time for a statement.  If the current time
** is requested more than once within the same run of a single prepared
** statement, the exact same time is returned for each invocation regardless
** of the amount of time that elapses between invocations.  In other words,
** the time returned is always the time of the first call.

/*
** Print the value of a register for tracing purposes:
*/
static void memTracePrint(Mem *p){
  if( p->flags & MEM_Undefined ){
    printf(" undefined");
  }else if( p->flags & MEM_Null ){
    printf(" NULL");
    printf(p->flags & MEM_Zero ? " NULL-nochng" : " NULL");
  }else if( (p->flags & (MEM_Int|MEM_Str))==(MEM_Int|MEM_Str) ){
    printf(" si:%lld", p->u.i);
  }else if( p->flags & MEM_Int ){
    printf(" i:%lld", p->u.i);
#ifndef SQLITE_OMIT_FLOATING_POINT
  }else if( p->flags & MEM_Real ){
    printf(" r:%g", p->u.r);

  if( p->apCsr[pOp->p1]->nullRow ){
    sqlite3VdbeMemSetNull(aMem + pOp->p3);
    goto jump_to_p2;
  }
  break;
}

#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
/* Opcode: Offset P1 P2 P3 * *
** Synopsis: r[P3] = sqlite_offset(P1)
**
** Store in register r[P3] the byte offset into the database file that is the
** start of the payload for the record at which that cursor P1 is currently
** pointing.
**
** P2 is the column number for the argument to the sqlite_offset() function.
** This opcode does not use P2 itself, but the P2 value is used by the
** code generator.  The P1, P2, and P3 operands to this opcode are the
** as as for OP_Column.
**
** This opcode is only available if SQLite is compiled with the
** -DSQLITE_ENABLE_OFFSET_SQL_FUNC option.
*/
case OP_Offset: {          /* out3 */
  VdbeCursor *pC;    /* The VDBE cursor */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  pOut = &p->aMem[pOp->p3];
  if( NEVER(pC==0) || pC->eCurType!=CURTYPE_BTREE ){
    sqlite3VdbeMemSetNull(pOut);
  }else{
    sqlite3VdbeMemSetInt64(pOut, sqlite3BtreeOffset(pC->uc.pCursor));
  }
  break;
}
#endif /* SQLITE_ENABLE_OFFSET_SQL_FUNC */

/* Opcode: Column P1 P2 P3 P4 P5
** Synopsis: r[P3]=PX
**
** Interpret the data that cursor P1 points to as a structure built using
** the MakeRecord instruction.  (See the MakeRecord opcode for additional
** information about the format of the data.)  Extract the P2-th column
** from this record.  If there are less that (P2+1) 

  /* Loop through the elements that will make up the record to figure
  ** out how much space is required for the new record.
  */
  pRec = pLast;
  do{
    assert( memIsValid(pRec) );
    pRec->uTemp = serial_type = sqlite3VdbeSerialType(pRec, file_format, &len);
    serial_type = sqlite3VdbeSerialType(pRec, file_format, &len);
    if( pRec->flags & MEM_Zero ){
      if( serial_type==0 ){
        /* Values with MEM_Null and MEM_Zero are created by xColumn virtual
        ** table methods that never invoke sqlite3_result_xxxxx() while
        ** computing an unchanging column value in an UPDATE statement.
        ** Give such values a special internal-use-only serial-type of 10
        ** so that they can be passed through to xUpdate and have
        ** a true sqlite3_value_nochange(). */
        assert( pOp->p5==OPFLAG_NOCHNG_MAGIC || CORRUPT_DB );
        serial_type = 10;
      if( nData ){
      }else if( nData ){
        if( sqlite3VdbeMemExpandBlob(pRec) ) goto no_mem;
      }else{
        nZero += pRec->u.nZero;
        len -= pRec->u.nZero;
      }
    }
    nData += len;
    testcase( serial_type==127 );
    testcase( serial_type==128 );
    nHdr += serial_type<=127 ? 1 : sqlite3VarintLen(serial_type);
    pRec->uTemp = serial_type;
    if( pRec==pData0 ) break;
    pRec--;
  }while(1);

  /* EVIDENCE-OF: R-22564-11647 The header begins with a single varint
  ** which determines the total number of bytes in the header. The varint
  ** value is the size of the header in bytes including the size varint

case OP_InsertInt: {
  Mem *pData;       /* MEM cell holding data for the record to be inserted */
  Mem *pKey;        /* MEM cell holding key  for the record */
  VdbeCursor *pC;   /* Cursor to table into which insert is written */
  int seekResult;   /* Result of prior seek or 0 if no USESEEKRESULT flag */
  const char *zDb;  /* database name - used by the update hook */
  Table *pTab;      /* Table structure - used by update and pre-update hooks */
  int op;           /* Opcode for update hook: SQLITE_UPDATE or SQLITE_INSERT */
  BtreePayload x;   /* Payload to be inserted */

  op = 0;
  pData = &aMem[pOp->p2];
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( memIsValid(pData) );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( pC->uc.pCursor!=0 );

  }

  if( pOp->p4type==P4_TABLE && HAS_UPDATE_HOOK(db) ){
    assert( pC->iDb>=0 );
    zDb = db->aDb[pC->iDb].zDbSName;
    pTab = pOp->p4.pTab;
    assert( (pOp->p5 & OPFLAG_ISNOOP) || HasRowid(pTab) );
    op = ((pOp->p5 & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_INSERT);
  }else{
    pTab = 0; /* Not needed.  Silence a compiler warning. */
    pTab = 0;
    zDb = 0;  /* Not needed.  Silence a compiler warning. */
  }

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
  /* Invoke the pre-update hook, if any */
  if( pTab ){
  if( db->xPreUpdateCallback 
    if( db->xPreUpdateCallback && !(pOp->p5 & OPFLAG_ISUPDATE) ){
   && pOp->p4type==P4_TABLE
   && !(pOp->p5 & OPFLAG_ISUPDATE)
  ){
    sqlite3VdbePreUpdateHook(p, pC, SQLITE_INSERT, zDb, pTab, x.nKey, pOp->p2);
      sqlite3VdbePreUpdateHook(p, pC, SQLITE_INSERT, zDb, pTab, x.nKey,pOp->p2);
    }
    if( db->xUpdateCallback==0 || pTab->aCol==0 ){
      /* Prevent post-update hook from running in cases when it should not */
      pTab = 0;
    }
  }
  if( pOp->p5 & OPFLAG_ISNOOP ) break;
#endif

  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
  if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = x.nKey;
  assert( pData->flags & (MEM_Blob|MEM_Str) );

      (pOp->p5 & (OPFLAG_APPEND|OPFLAG_SAVEPOSITION)), seekResult
  );
  pC->deferredMoveto = 0;
  pC->cacheStatus = CACHE_STALE;

  /* Invoke the update-hook if required. */
  if( rc ) goto abort_due_to_error;
  if( pTab ){
  if( db->xUpdateCallback && op ){
    db->xUpdateCallback(db->pUpdateArg, op, zDb, pTab->zName, x.nKey);
    assert( db->xUpdateCallback!=0 );
    assert( pTab->aCol!=0 );
    db->xUpdateCallback(db->pUpdateArg,
           (pOp->p5 & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_INSERT,
           zDb, pTab->zName, x.nKey);
  }
  break;
}

/* Opcode: Delete P1 P2 P3 P4 P5
**
** Delete the record at which the P1 cursor is currently pointing.

  VdbeBranchTaken(res!=0,2);
  if( res ) goto jump_to_p2;
  break;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Opcode: VColumn P1 P2 P3 * *
/* Opcode: VColumn P1 P2 P3 * P5
** Synopsis: r[P3]=vcolumn(P2)
**
** Store the value of the P2-th column of
** the row of the virtual-table that the 
** P1 cursor is pointing to into register P3.
** Store in register P3 the value of the P2-th column of
** the current row of the virtual-table of cursor P1.
**
** If the VColumn opcode is being used to fetch the value of
** an unchanging column during an UPDATE operation, then the P5
** value is 1.  Otherwise, P5 is 0.  The P5 value is returned
** by sqlite3_vtab_nochange() routine can can be used
** by virtual table implementations to return special "no-change"
** marks which can be more efficient, depending on the virtual table.
*/
case OP_VColumn: {
  sqlite3_vtab *pVtab;
  const sqlite3_module *pModule;
  Mem *pDest;
  sqlite3_context sContext;

    break;
  }
  pVtab = pCur->uc.pVCur->pVtab;
  pModule = pVtab->pModule;
  assert( pModule->xColumn );
  memset(&sContext, 0, sizeof(sContext));
  sContext.pOut = pDest;
  if( pOp->p5 ){
    sqlite3VdbeMemSetNull(pDest);
    pDest->flags = MEM_Null|MEM_Zero;
    pDest->u.nZero = 0;
  }else{
  MemSetTypeFlag(pDest, MEM_Null);
    MemSetTypeFlag(pDest, MEM_Null);
  }
  rc = pModule->xColumn(pCur->uc.pVCur, &sContext, pOp->p2);
  sqlite3VtabImportErrmsg(p, pVtab);
  if( sContext.isError ){
    rc = sContext.isError;
  }
  sqlite3VdbeChangeEncoding(pDest, encoding);
  REGISTER_TRACE(pOp->p3, pDest);

  }

  REGISTER_TRACE(pOp->p3, pOut);
  UPDATE_MAX_BLOBSIZE(pOut);
  break;
}


/* Opcode: Trace P1 P2 * P4 *
**
** Write P4 on the statement trace output if statement tracing is
** enabled.
**
** Operand P1 must be 0x7fffffff and P2 must positive.
*/
/* Opcode: Init P1 P2 P3 P4 *
** Synopsis: Start at P2
**
** Programs contain a single instance of this opcode as the very first
** opcode.
**
** If tracing is enabled (by the sqlite3_trace()) interface, then
** the UTF-8 string contained in P4 is emitted on the trace callback.
** Or if P4 is blank, use the string returned by sqlite3_sql().
**
** If P2 is not zero, jump to instruction P2.
**
** Increment the value of P1 so that OP_Once opcodes will jump the
** first time they are evaluated for this run.
**
** If P3 is not zero, then it is an address to jump to if an SQLITE_CORRUPT
** error is encountered.
*/
case OP_Trace:
case OP_Init: {          /* jump */
  char *zTrace;
  int i;

  /* If the P4 argument is not NULL, then it must be an SQL comment string.
  ** The "--" string is broken up to prevent false-positives with srcck1.c.
  **
  ** This assert() provides evidence for:
  ** EVIDENCE-OF: R-50676-09860 The callback can compute the same text that
  ** would have been returned by the legacy sqlite3_trace() interface by
  ** using the X argument when X begins with "--" and invoking
  ** sqlite3_expanded_sql(P) otherwise.
  */
  assert( pOp->p4.z==0 || strncmp(pOp->p4.z, "-" "- ", 3)==0 );

  assert( pOp==p->aOp );  /* Always instruction 0 */
  /* OP_Init is always instruction 0 */
  assert( pOp==p->aOp || pOp->opcode==OP_Trace );

#ifndef SQLITE_OMIT_TRACE
  if( (db->mTrace & (SQLITE_TRACE_STMT|SQLITE_TRACE_LEGACY))!=0
   && !p->doingRerun
   && (zTrace = (pOp->p4.z ? pOp->p4.z : p->zSql))!=0
  ){
#ifndef SQLITE_OMIT_DEPRECATED

  ){
    sqlite3DebugPrintf("SQL-trace: %s\n", zTrace);
  }
#endif /* SQLITE_DEBUG */
#endif /* SQLITE_OMIT_TRACE */
  assert( pOp->p2>0 );
  if( pOp->p1>=sqlite3GlobalConfig.iOnceResetThreshold ){
    if( pOp->opcode==OP_Trace ) break;
    for(i=1; i<p->nOp; i++){
      if( p->aOp[i].opcode==OP_Once ) p->aOp[i].p1 = 0;
    }
    pOp->p1 = 0;
  }
  pOp->p1++;
  p->aCounter[SQLITE_STMTSTATUS_RUN]++;

SQLITE_PRIVATE int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
  if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
  if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
  if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
  if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
  if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
  if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
  if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
  return WRC_Continue;
}

/*
** Walk the parse trees associated with all subqueries in the
** FROM clause of SELECT statement p.  Do not invoke the select
** callback on p, but do invoke it on each FROM clause subquery
** and on any subqueries further down in the tree.  Return 
** WRC_Abort or WRC_Continue;
*/
SQLITE_PRIVATE int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
  SrcList *pSrc;
  int i;
  struct SrcList_item *pItem;

  pSrc = p->pSrc;
  if( ALWAYS(pSrc) ){
    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
      if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){
        return WRC_Abort;
      }
      if( pItem->fg.isTabFunc
       && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg)
      ){
        return WRC_Abort;
  assert( pSrc!=0 );
  for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
    if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){
      return WRC_Abort;
    }
    if( pItem->fg.isTabFunc
     && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg)
    ){
      return WRC_Abort;
      }
    }
  }
  return WRC_Continue;
} 

/*
** Call sqlite3WalkExpr() for every expression in Select statement p.

    ** column in the FROM clause.  This is used by the LIMIT and ORDER BY
    ** clause processing on UPDATE and DELETE statements.
    */
    case TK_ROW: {
      SrcList *pSrcList = pNC->pSrcList;
      struct SrcList_item *pItem;
      assert( pSrcList && pSrcList->nSrc==1 );
      pItem = pSrcList->a; 
      pItem = pSrcList->a;
      assert( HasRowid(pItem->pTab) && pItem->pTab->pSelect==0 );
      pExpr->op = TK_COLUMN;
      pExpr->pTab = pItem->pTab;
      pExpr->iTable = pItem->iCursor;
      pExpr->iColumn = -1;
      pExpr->affinity = SQLITE_AFF_INTEGER;
      break;
    }

    p->selFlags |= SF_Resolved;

    /* Resolve the expressions in the LIMIT and OFFSET clauses. These
    ** are not allowed to refer to any names, so pass an empty NameContext.
    */
    memset(&sNC, 0, sizeof(sNC));
    sNC.pParse = pParse;
    if( sqlite3ResolveExprNames(&sNC, p->pLimit) ||
    if( sqlite3ResolveExprNames(&sNC, p->pLimit) ){
        sqlite3ResolveExprNames(&sNC, p->pOffset) ){
      return WRC_Abort;
    }

    /* If the SF_Converted flags is set, then this Select object was
    ** was created by the convertCompoundSelectToSubquery() function.
    ** In this case the ORDER BY clause (p->pOrderBy) should be resolved
    ** as if it were part of the sub-query, not the parent. This block

  if( p ){
    int i;
    for(i=0; i<p->nExpr; i++){
      heightOfExpr(p->a[i].pExpr, pnHeight);
    }
  }
}
static void heightOfSelect(Select *p, int *pnHeight){
  if( p ){
static void heightOfSelect(Select *pSelect, int *pnHeight){
  Select *p;
  for(p=pSelect; p; p=p->pPrior){
    heightOfExpr(p->pWhere, pnHeight);
    heightOfExpr(p->pHaving, pnHeight);
    heightOfExpr(p->pLimit, pnHeight);
    heightOfExpr(p->pOffset, pnHeight);
    heightOfExprList(p->pEList, pnHeight);
    heightOfExprList(p->pGroupBy, pnHeight);
    heightOfExprList(p->pOrderBy, pnHeight);
    heightOfSelect(p->pPrior, pnHeight);
  }
}

/*
** Set the Expr.nHeight variable in the structure passed as an 
** argument. An expression with no children, Expr.pList or 
** Expr.pSelect member has a height of 1. Any other expression

  assert( pToken );
  pNew = sqlite3ExprAlloc(db, TK_FUNCTION, pToken, 1);
  if( pNew==0 ){
    sqlite3ExprListDelete(db, pList); /* Avoid memory leak when malloc fails */
    return 0;
  }
  pNew->x.pList = pList;
  ExprSetProperty(pNew, EP_HasFunc);
  assert( !ExprHasProperty(pNew, EP_xIsSelect) );
  sqlite3ExprSetHeightAndFlags(pParse, pNew);
  return pNew;
}

/*
** Assign a variable number to an expression that encodes a wildcard

    pNew->pGroupBy = sqlite3ExprListDup(db, p->pGroupBy, flags);
    pNew->pHaving = sqlite3ExprDup(db, p->pHaving, flags);
    pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy, flags);
    pNew->op = p->op;
    pNew->pNext = pNext;
    pNew->pPrior = 0;
    pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
    pNew->pOffset = sqlite3ExprDup(db, p->pOffset, flags);
    pNew->iLimit = 0;
    pNew->iOffset = 0;
    pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
    pNew->addrOpenEphm[0] = -1;
    pNew->addrOpenEphm[1] = -1;
    pNew->nSelectRow = p->nSelectRow;
    pNew->pWith = withDup(db, p->pWith);

** pList might be NULL following an OOM error.  But pSpan should never be
** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
** is set.
*/
SQLITE_PRIVATE void sqlite3ExprListSetSpan(
  Parse *pParse,          /* Parsing context */
  ExprList *pList,        /* List to which to add the span. */
  const char *zStart,     /* Start of the span */
  ExprSpan *pSpan         /* The span to be added */
  const char *zEnd        /* End of the span */
){
  sqlite3 *db = pParse->db;
  assert( pList!=0 || db->mallocFailed!=0 );
  if( pList ){
    struct ExprList_item *pItem = &pList->a[pList->nExpr-1];
    assert( pList->nExpr>0 );
    assert( db->mallocFailed || pItem->pExpr==pSpan->pExpr );
    sqlite3DbFree(db, pItem->zSpan);
    pItem->zSpan = sqlite3DbStrNDup(db, (char*)pSpan->zStart,
    pItem->zSpan = sqlite3DbSpanDup(db, zStart, zEnd);
                                    (int)(pSpan->zEnd - pSpan->zStart));
  }
}

/*
** If the expression list pEList contains more than iLimit elements,
** leave an error message in pParse.
*/

  if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
    return 0; /* No DISTINCT keyword and no aggregate functions */
  }
  assert( p->pGroupBy==0 );              /* Has no GROUP BY clause */
  if( p->pLimit ) return 0;              /* Has no LIMIT clause */
  assert( p->pOffset==0 );               /* No LIMIT means no OFFSET */
  if( p->pWhere ) return 0;              /* Has no WHERE clause */
  pSrc = p->pSrc;
  assert( pSrc!=0 );
  if( pSrc->nSrc!=1 ) return 0;          /* Single term in FROM clause */
  if( pSrc->a[0].pSelect ) return 0;     /* FROM is not a subquery or view */
  pTab = pSrc->a[0].pTab;
  assert( pTab!=0 );

**     SELECT <column1>, <column2>... FROM <table>
**
** If the RHS of the IN operator is a list or a more complex subquery, then
** an ephemeral table might need to be generated from the RHS and then
** pX->iTable made to point to the ephemeral table instead of an
** existing table.
**
** The inFlags parameter must contain exactly one of the bits
** IN_INDEX_MEMBERSHIP or IN_INDEX_LOOP.  If inFlags contains
** IN_INDEX_MEMBERSHIP, then the generated table will be used for a
** fast membership test.  When the IN_INDEX_LOOP bit is set, the
** IN index will be used to loop over all values of the RHS of the
** The inFlags parameter must contain, at a minimum, one of the bits
** IN_INDEX_MEMBERSHIP or IN_INDEX_LOOP but not both.  If inFlags contains
** IN_INDEX_MEMBERSHIP, then the generated table will be used for a fast
** membership test.  When the IN_INDEX_LOOP bit is set, the IN index will
** be used to loop over all values of the RHS of the IN operator.
** IN operator.
**
** When IN_INDEX_LOOP is used (and the b-tree will be used to iterate
** through the set members) then the b-tree must not contain duplicates.
** An epheremal table must be used unless the selected columns are guaranteed
** An epheremal table will be created unless the selected columns are guaranteed
** to be unique - either because it is an INTEGER PRIMARY KEY or due to
** a UNIQUE constraint or index.
**
** When IN_INDEX_MEMBERSHIP is used (and the b-tree will be used 
** for fast set membership tests) then an epheremal table must 
** be used unless <columns> is a single INTEGER PRIMARY KEY column or an 
** index can be found with the specified <columns> as its left-most.

      **
      ** In both cases, the query is augmented with "LIMIT 1".  Any 
      ** preexisting limit is discarded in place of the new LIMIT 1.
      */
      Select *pSel;                         /* SELECT statement to encode */
      SelectDest dest;                      /* How to deal with SELECT result */
      int nReg;                             /* Registers to allocate */
      Expr *pLimit;                         /* New limit expression */

      testcase( pExpr->op==TK_EXISTS );
      testcase( pExpr->op==TK_SELECT );
      assert( pExpr->op==TK_EXISTS || pExpr->op==TK_SELECT );
      assert( ExprHasProperty(pExpr, EP_xIsSelect) );

      pSel = pExpr->x.pSelect;

        sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSDParm, dest.iSDParm+nReg-1);
        VdbeComment((v, "Init subquery result"));
      }else{
        dest.eDest = SRT_Exists;
        sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
        VdbeComment((v, "Init EXISTS result"));
      }
      pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,&sqlite3IntTokens[1], 0);
      if( pSel->pLimit ){
      sqlite3ExprDelete(pParse->db, pSel->pLimit);
      pSel->pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,
                                  &sqlite3IntTokens[1], 0);
        sqlite3ExprDelete(pParse->db, pSel->pLimit->pLeft);
        pSel->pLimit->pLeft = pLimit;
      }else{
        pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
      }
      pSel->iLimit = 0;
      pSel->selFlags &= ~SF_MultiValue;
      if( sqlite3Select(pParse, pSel, &dest) ){
        return 0;
      }
      rReg = dest.iSDParm;
      ExprSetVVAProperty(pExpr, EP_NoReduce);
      break;
    }

        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
      }
#endif
      if( pDef->funcFlags & SQLITE_FUNC_NEEDCOLL ){
        if( !pColl ) pColl = db->pDfltColl; 
        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
      }
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
      if( pDef->funcFlags & SQLITE_FUNC_OFFSET ){
        Expr *pArg = pFarg->a[0].pExpr;
        if( pArg->op==TK_COLUMN ){
          sqlite3VdbeAddOp3(v, OP_Offset, pArg->iTable, pArg->iColumn, target);
        }else{
          sqlite3VdbeAddOp2(v, OP_Null, 0, target);
        }
      }else
#endif
      {
      sqlite3VdbeAddOp4(v, pParse->iSelfTab ? OP_PureFunc0 : OP_Function0,
                        constMask, r1, target, (char*)pDef, P4_FUNCDEF);
      sqlite3VdbeChangeP5(v, (u8)nFarg);
        sqlite3VdbeAddOp4(v, pParse->iSelfTab ? OP_PureFunc0 : OP_Function0,
                          constMask, r1, target, (char*)pDef, P4_FUNCDEF);
        sqlite3VdbeChangeP5(v, (u8)nFarg);
      }
      if( nFarg && constMask==0 ){
        sqlite3ReleaseTempRange(pParse, r1, nFarg);
      }
      return target;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_EXISTS:

      aCreateTbl[i] = 0;
      sqlite3TableLock(pParse, iDb, aRoot[i], 1, zTab);
      if( zWhere ){
        sqlite3NestedParse(pParse,
           "DELETE FROM %Q.%s WHERE %s=%Q",
           pDb->zDbSName, zTab, zWhereType, zWhere
        );
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
      }else if( db->xPreUpdateCallback ){
        sqlite3NestedParse(pParse, "DELETE FROM %Q.%s", pDb->zDbSName, zTab);
#endif
      }else{
        /* The sqlite_stat[134] table already exists.  Delete all rows. */
        sqlite3VdbeAddOp2(v, OP_Clear, aRoot[i], iDb);
      }
    }
  }

  int regRowid = iMem++;       /* Rowid argument passed to stat_push() */
#endif
  int regTemp = iMem++;        /* Temporary use register */
  int regTabname = iMem++;     /* Register containing table name */
  int regIdxname = iMem++;     /* Register containing index name */
  int regStat1 = iMem++;       /* Value for the stat column of sqlite_stat1 */
  int regPrev = iMem;          /* MUST BE LAST (see below) */
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
  Table *pStat1 = 0; 
#endif

  pParse->nMem = MAX(pParse->nMem, iMem);
  v = sqlite3GetVdbe(pParse);
  if( v==0 || NEVER(pTab==0) ){
    return;
  }
  if( pTab->tnum==0 ){

  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
#ifndef SQLITE_OMIT_AUTHORIZATION
  if( sqlite3AuthCheck(pParse, SQLITE_ANALYZE, pTab->zName, 0,
      db->aDb[iDb].zDbSName ) ){
    return;
  }
#endif

#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
  if( db->xPreUpdateCallback ){
    pStat1 = (Table*)sqlite3DbMallocZero(db, sizeof(Table) + 13);
    if( pStat1==0 ) return;
    pStat1->zName = (char*)&pStat1[1];
    memcpy(pStat1->zName, "sqlite_stat1", 13);
    pStat1->nCol = 3;
    pStat1->iPKey = -1;
    sqlite3VdbeAddOp4(pParse->pVdbe, OP_Noop, 0, 0, 0,(char*)pStat1,P4_DYNBLOB);
  }
#endif

  /* Establish a read-lock on the table at the shared-cache level. 
  ** Open a read-only cursor on the table. Also allocate a cursor number
  ** to use for scanning indexes (iIdxCur). No index cursor is opened at
  ** this time though.  */
  sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
  iTabCur = iTab++;

    /* Add the entry to the stat1 table. */
    callStatGet(v, regStat4, STAT_GET_STAT1, regStat1);
    assert( "BBB"[0]==SQLITE_AFF_TEXT );
    sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp, "BBB", 0);
    sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
    sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regTemp, regNewRowid);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
    sqlite3VdbeChangeP4(v, -1, (char*)pStat1, P4_TABLE);
#endif
    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);

    /* Add the entries to the stat3 or stat4 table. */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
    {
      int regEq = regStat1;
      int regLt = regStat1+1;

    jZeroRows = sqlite3VdbeAddOp1(v, OP_IfNot, regStat1); VdbeCoverage(v);
    sqlite3VdbeAddOp2(v, OP_Null, 0, regIdxname);
    assert( "BBB"[0]==SQLITE_AFF_TEXT );
    sqlite3VdbeAddOp4(v, OP_MakeRecord, regTabname, 3, regTemp, "BBB", 0);
    sqlite3VdbeAddOp2(v, OP_NewRowid, iStatCur, regNewRowid);
    sqlite3VdbeAddOp3(v, OP_Insert, iStatCur, regTemp, regNewRowid);
    sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
    sqlite3VdbeChangeP4(v, -1, (char*)pStat1, P4_TABLE);
#endif
    sqlite3VdbeJumpHere(v, jZeroRows);
  }
}


/*
** Generate code that will cause the most recent index analysis to

    }
    if( sqlite3FixExprList(pFix, pSelect->pOrderBy) ){
      return 1;
    }
    if( sqlite3FixExpr(pFix, pSelect->pLimit) ){
      return 1;
    }
    if( sqlite3FixExpr(pFix, pSelect->pOffset) ){
      return 1;
    }
    pSelect = pSelect->pPrior;
  }
  return 0;
}
SQLITE_PRIVATE int sqlite3FixExpr(
  DbFixer *pFix,     /* Context of the fixation */
  Expr *pExpr        /* The expression to be fixed to one database */

**
** Default value expressions must be constant.  Raise an exception if this
** is not the case.
**
** This routine is called by the parser while in the middle of
** parsing a CREATE TABLE statement.
*/
SQLITE_PRIVATE void sqlite3AddDefaultValue(Parse *pParse, ExprSpan *pSpan){
SQLITE_PRIVATE void sqlite3AddDefaultValue(
  Parse *pParse,           /* Parsing context */
  Expr *pExpr,             /* The parsed expression of the default value */
  const char *zStart,      /* Start of the default value text */
  const char *zEnd         /* First character past end of defaut value text */
){
  Table *p;
  Column *pCol;
  sqlite3 *db = pParse->db;
  p = pParse->pNewTable;
  if( p!=0 ){
    pCol = &(p->aCol[p->nCol-1]);
    if( !sqlite3ExprIsConstantOrFunction(pSpan->pExpr, db->init.busy) ){
    if( !sqlite3ExprIsConstantOrFunction(pExpr, db->init.busy) ){
      sqlite3ErrorMsg(pParse, "default value of column [%s] is not constant",
          pCol->zName);
    }else{
      /* A copy of pExpr is used instead of the original, as pExpr contains
      ** tokens that point to volatile memory. The 'span' of the expression
      ** tokens that point to volatile memory.	
      ** is required by pragma table_info.
      */
      Expr x;
      sqlite3ExprDelete(db, pCol->pDflt);
      memset(&x, 0, sizeof(x));
      x.op = TK_SPAN;
      x.u.zToken = sqlite3DbStrNDup(db, (char*)pSpan->zStart,
      x.u.zToken = sqlite3DbSpanDup(db, zStart, zEnd);
                                    (int)(pSpan->zEnd - pSpan->zStart));
      x.pLeft = pSpan->pExpr;
      x.pLeft = pExpr;
      x.flags = EP_Skip;
      pCol->pDflt = sqlite3ExprDup(db, &x, EXPRDUP_REDUCE);
      sqlite3DbFree(db, x.u.zToken);
    }
  }
  sqlite3ExprDelete(db, pSpan->pExpr);
  sqlite3ExprDelete(db, pExpr);
}

/*
** Backwards Compatibility Hack:
** 
** Historical versions of SQLite accepted strings as column names in
** indexes and PRIMARY KEY constraints and in UNIQUE constraints.  Example:

      assert(pParse->nTab==1);
      sqlite3MayAbort(pParse);
      sqlite3VdbeAddOp3(v, OP_OpenWrite, 1, pParse->regRoot, iDb);
      sqlite3VdbeChangeP5(v, OPFLAG_P2ISREG);
      pParse->nTab = 2;
      addrTop = sqlite3VdbeCurrentAddr(v) + 1;
      sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, addrTop);
      sqlite3SelectDestInit(&dest, SRT_Coroutine, regYield);
      sqlite3Select(pParse, pSelect, &dest);
      sqlite3VdbeEndCoroutine(v, 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);
      sqlite3SelectDestInit(&dest, SRT_Coroutine, regYield);
      sqlite3Select(pParse, pSelect, &dest);
      if( pParse->nErr ) return;
      sqlite3VdbeEndCoroutine(v, regYield);
      sqlite3VdbeJumpHere(v, addrTop - 1);
      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);
      sqlite3VdbeGoto(v, addrInsLoop);

  p->pCheck = sqlite3ExprListDup(db, pCNames, EXPRDUP_REDUCE);
  if( db->mallocFailed ) goto create_view_fail;

  /* Locate the end of the CREATE VIEW statement.  Make sEnd point to
  ** the end.
  */
  sEnd = pParse->sLastToken;
  assert( sEnd.z[0]!=0 );
  assert( sEnd.z[0]!=0 || sEnd.n==0 );
  if( sEnd.z[0]!=';' ){
    sEnd.z += sEnd.n;
  }
  sEnd.n = 0;
  n = (int)(sEnd.z - pBegin->z);
  assert( n>0 );
  z = pBegin->z;

  if( !p && (pOn || pUsing) ){
    sqlite3ErrorMsg(pParse, "a JOIN clause is required before %s", 
      (pOn ? "ON" : "USING")
    );
    goto append_from_error;
  }
  p = sqlite3SrcListAppend(db, p, pTable, pDatabase);
  if( p==0 || NEVER(p->nSrc==0) ){
  if( p==0 ){
    goto append_from_error;
  }
  assert( p->nSrc>0 );
  pItem = &p->a[p->nSrc-1];
  assert( pAlias!=0 );
  if( pAlias->n ){
    pItem->zAlias = sqlite3NameFromToken(db, pAlias);
  }
  pItem->pSelect = pSubquery;
  pItem->pOn = pOn;

    for(i=0; i<nCol; i++){
      const char *zColl = pIdx->azColl[i];
      pKey->aColl[i] = zColl==sqlite3StrBINARY ? 0 :
                        sqlite3LocateCollSeq(pParse, zColl);
      pKey->aSortOrder[i] = pIdx->aSortOrder[i];
    }
    if( pParse->nErr ){
      assert( pParse->rc==SQLITE_ERROR_MISSING_COLLSEQ );
      if( pIdx->bNoQuery==0 ){
        /* Deactivate the index because it contains an unknown collating
        ** sequence.  The only way to reactive the index is to reload the
        ** schema.  Adding the missing collating sequence later does not
        ** reactive the index.  The application had the chance to register
        ** the missing index using the collation-needed callback.  For
        ** simplicity, SQLite will not give the application a second chance.
        */
        pIdx->bNoQuery = 1;
        pParse->rc = SQLITE_ERROR_RETRY;
      }
      sqlite3KeyInfoUnref(pKey);
      pKey = 0;
    }
  }
  return pKey;
}

  }
  if( p && !p->xCmp && synthCollSeq(db, p) ){
    p = 0;
  }
  assert( !p || p->xCmp );
  if( p==0 ){
    sqlite3ErrorMsg(pParse, "no such collation sequence: %s", zName);
    pParse->rc = SQLITE_ERROR_MISSING_COLLSEQ;
  }
  return p;
}

/*
** This routine is called on a collation sequence before it is used to
** check that it is defined. An undefined collation sequence exists when

** pWhere argument is an optional WHERE clause that restricts the
** set of rows in the view that are to be added to the ephemeral table.
*/
SQLITE_PRIVATE void sqlite3MaterializeView(
  Parse *pParse,       /* Parsing context */
  Table *pView,        /* View definition */
  Expr *pWhere,        /* Optional WHERE clause to be added */
  ExprList *pOrderBy,  /* Optional ORDER BY clause */
  Expr *pLimit,        /* Optional LIMIT clause */
  int iCur             /* Cursor number for ephemeral table */
){
  SelectDest dest;
  Select *pSel;
  SrcList *pFrom;
  sqlite3 *db = pParse->db;
  int iDb = sqlite3SchemaToIndex(db, pView->pSchema);
  pWhere = sqlite3ExprDup(db, pWhere, 0);
  pFrom = sqlite3SrcListAppend(db, 0, 0, 0);
  if( pFrom ){
    assert( pFrom->nSrc==1 );
    pFrom->a[0].zName = sqlite3DbStrDup(db, pView->zName);
    pFrom->a[0].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zDbSName);
    assert( pFrom->a[0].pOn==0 );
    assert( pFrom->a[0].pUsing==0 );
  }
  pSel = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0, 
                          SF_IncludeHidden, 0, 0);
  pSel = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, pOrderBy, 
                          SF_IncludeHidden, pLimit);
  sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
  sqlite3Select(pParse, pSel, &dest);
  sqlite3SelectDelete(db, pSel);
}
#endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */

#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)

*/
SQLITE_PRIVATE Expr *sqlite3LimitWhere(
  Parse *pParse,               /* The parser context */
  SrcList *pSrc,               /* the FROM clause -- which tables to scan */
  Expr *pWhere,                /* The WHERE clause.  May be null */
  ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
  Expr *pLimit,                /* The LIMIT clause.  May be null */
  Expr *pOffset,               /* The OFFSET clause.  May be null */
  char *zStmtType              /* Either DELETE or UPDATE.  For err msgs. */
){
  sqlite3 *db = pParse->db;
  Expr *pWhereRowid = NULL;    /* WHERE rowid .. */
  Expr *pLhs = NULL;           /* LHS of IN(SELECT...) operator */
  Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
  Expr *pSelectRowid = NULL;   /* SELECT rowid ... */
  ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
  SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
  Select *pSelect = NULL;      /* Complete SELECT tree */
  Table *pTab;

  /* Check that there isn't an ORDER BY without a LIMIT clause.
  */
  if( pOrderBy && (pLimit == 0) ) {
  if( pOrderBy && pLimit==0 ) {
    sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
    goto limit_where_cleanup;
    sqlite3ExprDelete(pParse->db, pWhere);
    sqlite3ExprListDelete(pParse->db, pOrderBy);
    return 0;
  }

  /* We only need to generate a select expression if there
  ** is a limit/offset term to enforce.
  */
  if( pLimit == 0 ) {
    /* if pLimit is null, pOffset will always be null as well. */
    assert( pOffset == 0 );
    return pWhere;
  }

  /* Generate a select expression tree to enforce the limit/offset 
  ** term for the DELETE or UPDATE statement.  For example:
  **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
  ** becomes:
  **   DELETE FROM table_a WHERE rowid IN ( 
  **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
  **   );
  */

  pTab = pSrc->a[0].pTab;
  if( HasRowid(pTab) ){
  pSelectRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0);
  if( pSelectRowid == 0 ) goto limit_where_cleanup;
  pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid);
  if( pEList == 0 ) goto limit_where_cleanup;

    pLhs = sqlite3PExpr(pParse, TK_ROW, 0, 0);
    pEList = sqlite3ExprListAppend(
        pParse, 0, sqlite3PExpr(pParse, TK_ROW, 0, 0)
    );
  }else{
    Index *pPk = sqlite3PrimaryKeyIndex(pTab);
    if( pPk->nKeyCol==1 ){
      const char *zName = pTab->aCol[pPk->aiColumn[0]].zName;
      pLhs = sqlite3Expr(db, TK_ID, zName);
      pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ID, zName));
    }else{
      int i;
      for(i=0; i<pPk->nKeyCol; i++){
        Expr *p = sqlite3Expr(db, TK_ID, pTab->aCol[pPk->aiColumn[i]].zName);
        pEList = sqlite3ExprListAppend(pParse, pEList, p);
      }
      pLhs = sqlite3PExpr(pParse, TK_VECTOR, 0, 0);
      if( pLhs ){
        pLhs->x.pList = sqlite3ExprListDup(db, pEList, 0);
      }
    }
  }

  /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
  ** and the SELECT subtree. */
  pSrc->a[0].pTab = 0;
  pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);
  if( pSelectSrc == 0 ) {
  pSrc->a[0].pTab = pTab;
    sqlite3ExprListDelete(pParse->db, pEList);
    goto limit_where_cleanup;
  }
  pSrc->a[0].pIBIndex = 0;


  /* generate the SELECT expression tree. */
  pSelect = sqlite3SelectNew(pParse,pEList,pSelectSrc,pWhere,0,0,
                             pOrderBy,0,pLimit,pOffset);
  pSelect = sqlite3SelectNew(pParse, pEList, pSelectSrc, pWhere, 0 ,0, 
      pOrderBy,0,pLimit
  if( pSelect == 0 ) return 0;
  );

  /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
  pWhereRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0);
  pInClause = sqlite3PExpr(pParse, TK_IN, pLhs, 0);
  pInClause = pWhereRowid ? sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0) : 0;
  sqlite3PExprAddSelect(pParse, pInClause, pSelect);
  return pInClause;

limit_where_cleanup:
  sqlite3ExprDelete(pParse->db, pWhere);
  sqlite3ExprListDelete(pParse->db, pOrderBy);
  sqlite3ExprDelete(pParse->db, pLimit);
  sqlite3ExprDelete(pParse->db, pOffset);
  return 0;
}
#endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) */
       /*      && !defined(SQLITE_OMIT_SUBQUERY) */

/*
** Generate code for a DELETE FROM statement.
**
**     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
**                 \________/       \________________/
**                  pTabList              pWhere
*/
SQLITE_PRIVATE void sqlite3DeleteFrom(
  Parse *pParse,         /* The parser context */
  SrcList *pTabList,     /* The table from which we should delete things */
  Expr *pWhere           /* The WHERE clause.  May be null */
  Expr *pWhere,          /* The WHERE clause.  May be null */
  ExprList *pOrderBy,    /* ORDER BY clause. May be null */
  Expr *pLimit           /* LIMIT clause. May be null */
){
  Vdbe *v;               /* The virtual database engine */
  Table *pTab;           /* The table from which records will be deleted */
  int i;                 /* Loop counter */
  WhereInfo *pWInfo;     /* Information about the WHERE clause */
  Index *pIdx;           /* For looping over indices of the table */
  int iTabCur;           /* Cursor number for the table */

  memset(&sContext, 0, sizeof(sContext));
  db = pParse->db;
  if( pParse->nErr || db->mallocFailed ){
    goto delete_from_cleanup;
  }
  assert( pTabList->nSrc==1 );


  /* Locate the table which we want to delete.  This table has to be
  ** put in an SrcList structure because some of the subroutines we
  ** will be calling are designed to work with multiple tables and expect
  ** an SrcList* parameter instead of just a Table* parameter.
  */
  pTab = sqlite3SrcListLookup(pParse, pTabList);
  if( pTab==0 )  goto delete_from_cleanup;

  /* Figure out if we have any triggers and if the table being
  ** deleted from is a view
  */
#ifndef SQLITE_OMIT_TRIGGER
  pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
  isView = pTab->pSelect!=0;
  bComplex = pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0);
#else
# define pTrigger 0
# define isView 0
#endif
  bComplex = pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0);
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif

#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
  if( !isView ){
    pWhere = sqlite3LimitWhere(
        pParse, pTabList, pWhere, pOrderBy, pLimit, "DELETE"
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  /* If pTab is really a view, make sure it has been initialized.
  */
  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto delete_from_cleanup;
  }

  sqlite3BeginWriteOperation(pParse, 1, iDb);

  /* If we are trying to delete from a view, realize that view into
  ** an ephemeral table.
  */
#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
  if( isView ){
    sqlite3MaterializeView(pParse, pTab, pWhere, iTabCur);
    sqlite3MaterializeView(pParse, pTab, 
        pWhere, pOrderBy, pLimit, iTabCur
    );
    iDataCur = iIdxCur = iTabCur;
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  /* Resolve the column names in the WHERE clause.
  */
  memset(&sNC, 0, sizeof(sNC));
  sNC.pParse = pParse;

    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
  }

delete_from_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprDelete(db, pWhere);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) 
  sqlite3ExprListDelete(db, pOrderBy);
  sqlite3ExprDelete(db, pLimit);
#endif
  sqlite3DbFree(db, aToOpen);
  return;
}
/* Make sure "isView" and other macros defined above are undefined. Otherwise
** they may interfere with compilation of other functions in this file
** (or in another file, if this file becomes part of the amalgamation).  */
#ifdef isView

  ** the update-hook is not invoked for rows removed by REPLACE, but the 
  ** pre-update-hook is.
  */ 
  if( pTab->pSelect==0 ){
    u8 p5 = 0;
    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);
    sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));
    if( pParse->nested==0 ){
    if( pParse->nested==0 || 0==sqlite3_stricmp(pTab->zName, "sqlite_stat1") ){
      sqlite3VdbeAppendP4(v, (char*)pTab, P4_TABLE);
    }
    if( eMode!=ONEPASS_OFF ){
      sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);
    }
    if( iIdxNoSeek>=0 && iIdxNoSeek!=iDataCur ){
      sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);

      ** that point.
      **
      ** For a case-insensitive search, set variable cx to be the same as
      ** c but in the other case and search the input string for either
      ** c or cx.
      */
      if( c<=0x80 ){
        u32 cx;
        char zStop[3];
        int bMatch;
        if( noCase ){
          cx = sqlite3Toupper(c);
          c = sqlite3Tolower(c);
          zStop[0] = sqlite3Toupper(c);
          zStop[1] = sqlite3Tolower(c);
          zStop[2] = 0;
        }else{
          cx = c;
          zStop[0] = c;
          zStop[1] = 0;
        }
        while( (c2 = *(zString++))!=0 ){
          if( c2!=c && c2!=cx ) continue;
        while(1){
          zString += strcspn((const char*)zString, zStop);
          if( zString[0]==0 ) break;
          zString++;
          bMatch = patternCompare(zPattern,zString,pInfo,matchOther);
          if( bMatch!=SQLITE_NOMATCH ) return bMatch;
        }
      }else{
        int bMatch;
        while( (c2 = Utf8Read(zString))!=0 ){
          if( c2!=c ) continue;

#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
    FUNCTION2(unlikely,          1, 0, 0, noopFunc,  SQLITE_FUNC_UNLIKELY),
    FUNCTION2(likelihood,        2, 0, 0, noopFunc,  SQLITE_FUNC_UNLIKELY),
    FUNCTION2(likely,            1, 0, 0, noopFunc,  SQLITE_FUNC_UNLIKELY),
#ifdef SQLITE_DEBUG
    FUNCTION2(affinity,          1, 0, 0, noopFunc,  SQLITE_FUNC_AFFINITY),
#endif
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
    FUNCTION2(sqlite_offset,     1, 0, 0, noopFunc,  SQLITE_FUNC_OFFSET|
                                                     SQLITE_FUNC_TYPEOF),
#endif
    FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
    FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
    FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
    FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
    FUNCTION(trim,               1, 3, 0, trimFunc         ),
    FUNCTION(trim,               2, 3, 0, trimFunc         ),
    FUNCTION(min,               -1, 0, 1, minmaxFunc       ),

      }
      if( !p ) return;
      iSkip = sqlite3VdbeMakeLabel(v);
      sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); VdbeCoverage(v);
    }

    pParse->disableTriggers = 1;
    sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0);
    sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0, 0, 0);
    pParse->disableTriggers = 0;

    /* If the DELETE has generated immediate foreign key constraint 
    ** violations, halt the VDBE and return an error at this point, before
    ** any modifications to the schema are made. This is because statement
    ** transactions are not able to rollback schema changes.  
    **

      if( pRaise ){
        pRaise->affinity = OE_Abort;
      }
      pSelect = sqlite3SelectNew(pParse, 
          sqlite3ExprListAppend(pParse, 0, pRaise),
          sqlite3SrcListAppend(db, 0, &tFrom, 0),
          pWhere,
          0, 0, 0, 0, 0, 0
          0, 0, 0, 0, 0
      );
      pWhere = 0;
    }

    /* Disable lookaside memory allocation */
    db->lookaside.bDisable++;

        sqlite3VdbeAddOp3(v, OP_Column, srcTab, ipkColumn, regRowid);
      }else if( pSelect ){
        sqlite3VdbeAddOp2(v, OP_Copy, regFromSelect+ipkColumn, regRowid);
      }else{
        VdbeOp *pOp;
        sqlite3ExprCode(pParse, pList->a[ipkColumn].pExpr, regRowid);
        pOp = sqlite3VdbeGetOp(v, -1);
        assert( pOp!=0 );
        if( ALWAYS(pOp) && pOp->opcode==OP_Null && !IsVirtual(pTab) ){
        if( pOp->opcode==OP_Null && !IsVirtual(pTab) ){
          appendFlag = 1;
          pOp->opcode = OP_NewRowid;
          pOp->p1 = iDataCur;
          pOp->p2 = regRowid;
          pOp->p3 = regAutoinc;
        }
      }

         (0==pTab->pFKey && 0==sqlite3FkReferences(pTab)))
    ){
      sqlite3VdbeResolveLabel(v, addrUniqueOk);
      continue;
    }

    /* Check to see if the new index entry will be unique */
    sqlite3ExprCachePush(pParse);
    sqlite3VdbeAddOp4Int(v, OP_NoConflict, iThisCur, addrUniqueOk,
                         regIdx, pIdx->nKeyCol); VdbeCoverage(v);

    /* Generate code to handle collisions */
    regR = (pIdx==pPk) ? regIdx : sqlite3GetTempRange(pParse, nPkField);
    if( isUpdate || onError==OE_Replace ){
      if( HasRowid(pTab) ){

            regR, nPkField, 0, OE_Replace,
            (pIdx==pPk ? ONEPASS_SINGLE : ONEPASS_OFF), iThisCur);
        seenReplace = 1;
        break;
      }
    }
    sqlite3VdbeResolveLabel(v, addrUniqueOk);
    sqlite3ExprCachePop(pParse);
    if( regR!=regIdx ) sqlite3ReleaseTempRange(pParse, regR, nPkField);
  }
  if( ipkTop ){
    sqlite3VdbeGoto(v, ipkTop+1);
    sqlite3VdbeJumpHere(v, ipkBottom);
  }
  

  ** there is no ORDER BY, we will get an error. */
  if( pSelect->pGroupBy ){
    return 0;   /* SELECT may not have a GROUP BY clause */
  }
  if( pSelect->pLimit ){
    return 0;   /* SELECT may not have a LIMIT clause */
  }
  assert( pSelect->pOffset==0 );  /* Must be so if pLimit==0 */
  if( pSelect->pPrior ){
    return 0;   /* SELECT may not be a compound query */
  }
  if( pSelect->selFlags & SF_Distinct ){
    return 0;   /* SELECT may not be DISTINCT */
  }
  pEList = pSelect->pEList;

  int (*prepare_v3)(sqlite3*,const char*,int,unsigned int,
                    sqlite3_stmt**,const char**);
  int (*prepare16_v3)(sqlite3*,const void*,int,unsigned int,
                      sqlite3_stmt**,const void**);
  int (*bind_pointer)(sqlite3_stmt*,int,void*,const char*,void(*)(void*));
  void (*result_pointer)(sqlite3_context*,void*,const char*,void(*)(void*));
  void *(*value_pointer)(sqlite3_value*,const char*);
  int (*vtab_nochange)(sqlite3_context*);
  int (*value_nochange)(sqlite3_value*);
  const char *(*vtab_collation)(sqlite3_index_info*,int);
};

/*
** This is the function signature used for all extension entry points.  It
** is also defined in the file "loadext.c".
*/
typedef int (*sqlite3_loadext_entry)(

#define sqlite3_set_last_insert_rowid  sqlite3_api->set_last_insert_rowid
/* Version 3.20.0 and later */
#define sqlite3_prepare_v3             sqlite3_api->prepare_v3
#define sqlite3_prepare16_v3           sqlite3_api->prepare16_v3
#define sqlite3_bind_pointer           sqlite3_api->bind_pointer
#define sqlite3_result_pointer         sqlite3_api->result_pointer
#define sqlite3_value_pointer          sqlite3_api->value_pointer
/* Version 3.22.0 and later */
#define sqlite3_vtab_nochange          sqlite3_api->vtab_nochange
#define sqlite3_value_nochange         sqltie3_api->value_nochange
#define sqlite3_vtab_collation         sqltie3_api->vtab_collation
#endif /* !defined(SQLITE_CORE) && !defined(SQLITE_OMIT_LOAD_EXTENSION) */

#if !defined(SQLITE_CORE) && !defined(SQLITE_OMIT_LOAD_EXTENSION)
  /* This case when the file really is being compiled as a loadable 
  ** extension */
# define SQLITE_EXTENSION_INIT1     const sqlite3_api_routines *sqlite3_api=0;
# define SQLITE_EXTENSION_INIT2(v)  sqlite3_api=v;

  /* Version 3.18.0 and later */
  sqlite3_set_last_insert_rowid,
  /* Version 3.20.0 and later */
  sqlite3_prepare_v3,
  sqlite3_prepare16_v3,
  sqlite3_bind_pointer,
  sqlite3_result_pointer,
  sqlite3_value_pointer
  sqlite3_value_pointer,
  /* Version 3.22.0 and later */
  sqlite3_vtab_nochange,
  sqlite3_value_nochange,
  sqlite3_vtab_collation
};

/*
** Attempt to load an SQLite extension library contained in the file
** zFile.  The entry point is zProc.  zProc may be 0 in which case a
** default entry point name (sqlite3_extension_init) is used.  Use
** of the default name is recommended.

  zEntry = zProc ? zProc : "sqlite3_extension_init";

  handle = sqlite3OsDlOpen(pVfs, zFile);
#if SQLITE_OS_UNIX || SQLITE_OS_WIN
  for(ii=0; ii<ArraySize(azEndings) && handle==0; ii++){
    char *zAltFile = sqlite3_mprintf("%s.%s", zFile, azEndings[ii]);
    int bExists = 0;
    if( zAltFile==0 ) return SQLITE_NOMEM_BKPT;
    sqlite3OsAccess(pVfs, zAltFile, SQLITE_ACCESS_EXISTS, &bExists);
    handle = sqlite3OsDlOpen(pVfs, zAltFile);
    if( bExists )  handle = sqlite3OsDlOpen(pVfs, zAltFile);
    sqlite3_free(zAltFile);
  }
#endif
  if( handle==0 ){
    if( pzErrMsg ){
      *pzErrMsg = zErrmsg = sqlite3_malloc64(nMsg);
      if( zErrmsg ){

  ** the returned data set are:
  **
  ** cid:        Column id (numbered from left to right, starting at 0)
  ** name:       Column name
  ** type:       Column declaration type.
  ** notnull:    True if 'NOT NULL' is part of column declaration
  ** dflt_value: The default value for the column, if any.
  ** pk:         Non-zero for PK fields.
  */
  case PragTyp_TABLE_INFO: if( zRight ){
    Table *pTab;
    pTab = sqlite3LocateTable(pParse, LOCATE_NOERR, zRight, zDb);
    if( pTab ){
      int i, k;
      int nHidden = 0;

  ** We return -1000000 instead of the more usual -1 simply because using
  ** -1000000 as the incorrect index into db->aDb[] is much 
  ** more likely to cause a segfault than -1 (of course there are assert()
  ** statements too, but it never hurts to play the odds).
  */
  assert( sqlite3_mutex_held(db->mutex) );
  if( pSchema ){
    for(i=0; ALWAYS(i<db->nDb); i++){
    for(i=0; 1; i++){
      assert( i<db->nDb );
      if( db->aDb[i].pSchema==pSchema ){
        break;
      }
    }
    assert( i>=0 && i<db->nDb );
  }
  return i;

    sParse.pTriggerPrg = pT->pNext;
    sqlite3DbFree(db, pT);
  }

end_prepare:

  sqlite3ParserReset(&sParse);
  rc = sqlite3ApiExit(db, rc);
  assert( (rc&db->errMask)==rc );
  return rc;
}
static int sqlite3LockAndPrepare(
  sqlite3 *db,              /* Database handle. */
  const char *zSql,         /* UTF-8 encoded SQL statement. */
  int nBytes,               /* Length of zSql in bytes. */
  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
  Vdbe *pOld,               /* VM being reprepared */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */
){
  int rc;
  int cnt = 0;

#ifdef SQLITE_ENABLE_API_ARMOR
  if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
#endif
  *ppStmt = 0;
  if( !sqlite3SafetyCheckOk(db)||zSql==0 ){
    return SQLITE_MISUSE_BKPT;
  }
  sqlite3_mutex_enter(db->mutex);
  sqlite3BtreeEnterAll(db);
  do{
    /* Make multiple attempts to compile the SQL, until it either succeeds
    ** or encounters a permanent error.  A schema problem after one schema
    ** reset is considered a permanent error. */
  rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
  if( rc==SQLITE_SCHEMA ){
    sqlite3ResetOneSchema(db, -1);
    rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
    assert( rc==SQLITE_OK || *ppStmt==0 );
  }while( rc==SQLITE_ERROR_RETRY
       || (rc==SQLITE_SCHEMA && (sqlite3ResetOneSchema(db,-1), cnt++)==0) );
    sqlite3_finalize(*ppStmt);
    rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
  }
  sqlite3BtreeLeaveAll(db);
  rc = sqlite3ApiExit(db, rc);
  assert( (rc&db->errMask)==rc );
  sqlite3_mutex_leave(db->mutex);
  assert( rc==SQLITE_OK || *ppStmt==0 );
  return rc;
}

/*
** Rerun the compilation of a statement after a schema change.
**
** If the statement is successfully recompiled, return SQLITE_OK. Otherwise,

    sqlite3ExprListDelete(db, p->pEList);
    sqlite3SrcListDelete(db, p->pSrc);
    sqlite3ExprDelete(db, p->pWhere);
    sqlite3ExprListDelete(db, p->pGroupBy);
    sqlite3ExprDelete(db, p->pHaving);
    sqlite3ExprListDelete(db, p->pOrderBy);
    sqlite3ExprDelete(db, p->pLimit);
    sqlite3ExprDelete(db, p->pOffset);
    if( OK_IF_ALWAYS_TRUE(p->pWith) ) sqlite3WithDelete(db, p->pWith);
    if( bFree ) sqlite3DbFreeNN(db, p);
    p = pPrior;
    bFree = 1;
  }
}

  ExprList *pEList,     /* which columns to include in the result */
  SrcList *pSrc,        /* the FROM clause -- which tables to scan */
  Expr *pWhere,         /* the WHERE clause */
  ExprList *pGroupBy,   /* the GROUP BY clause */
  Expr *pHaving,        /* the HAVING clause */
  ExprList *pOrderBy,   /* the ORDER BY clause */
  u32 selFlags,         /* Flag parameters, such as SF_Distinct */
  Expr *pLimit,         /* LIMIT value.  NULL means not used */
  Expr *pLimit          /* LIMIT value.  NULL means not used */
  Expr *pOffset         /* OFFSET value.  NULL means no offset */
){
  Select *pNew;
  Select standin;
  pNew = sqlite3DbMallocRawNN(pParse->db, sizeof(*pNew) );
  if( pNew==0 ){
    assert( pParse->db->mallocFailed );
    pNew = &standin;

  pNew->pWhere = pWhere;
  pNew->pGroupBy = pGroupBy;
  pNew->pHaving = pHaving;
  pNew->pOrderBy = pOrderBy;
  pNew->pPrior = 0;
  pNew->pNext = 0;
  pNew->pLimit = pLimit;
  pNew->pOffset = pOffset;
  pNew->pWith = 0;
  assert( pOffset==0 || pLimit!=0 || pParse->nErr>0
                     || pParse->db->mallocFailed!=0 );
  if( pParse->db->mallocFailed ) {
    clearSelect(pParse->db, pNew, pNew!=&standin);
    pNew = 0;
  }else{
    assert( pNew->pSrc!=0 || pParse->nErr>0 );
  }
  assert( pNew!=&standin );

  char const *zOrigDb = 0;
  char const *zOrigTab = 0;
  char const *zOrigCol = 0;
#endif

  assert( pExpr!=0 );
  assert( pNC->pSrcList!=0 );
  assert( pExpr->op!=TK_AGG_COLUMN );  /* This routine runes before aggregates
                                       ** are processed */
  switch( pExpr->op ){
    case TK_AGG_COLUMN:
    case TK_COLUMN: {
      /* The expression is a column. Locate the table the column is being
      ** extracted from in NameContext.pSrcList. This table may be real
      ** database table or a subquery.
      */
      Table *pTab = 0;            /* Table structure column is extracted from */
      Select *pS = 0;             /* Select the column is extracted from */
      int iCol = pExpr->iColumn;  /* Index of column in pTab */
      testcase( pExpr->op==TK_AGG_COLUMN );
      testcase( pExpr->op==TK_COLUMN );
      while( pNC && !pTab ){
        SrcList *pTabList = pNC->pSrcList;
        for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
        if( j<pTabList->nSrc ){
          pTab = pTabList->a[j].pTab;
          pS = pTabList->a[j].pSelect;
        }else{

    return;
  }
#endif

  if( pParse->colNamesSet || db->mallocFailed ) return;
  /* Column names are determined by the left-most term of a compound select */
  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
  SELECTTRACE(1,pParse,pSelect,("generating column names\n"));
  pTabList = pSelect->pSrc;
  pEList = pSelect->pEList;
  assert( v!=0 );
  assert( pTabList!=0 );
  pParse->colNamesSet = 1;
  fullName = (db->flags & SQLITE_FullColNames)!=0;
  srcName = (db->flags & SQLITE_ShortColNames)!=0 || fullName;

      /* If the column contains an "AS <name>" phrase, use <name> as the name */
    }else{
      Expr *pColExpr = sqlite3ExprSkipCollate(pEList->a[i].pExpr);
      while( pColExpr->op==TK_DOT ){
        pColExpr = pColExpr->pRight;
        assert( pColExpr!=0 );
      }
      if( (pColExpr->op==TK_COLUMN || pColExpr->op==TK_AGG_COLUMN)
       && pColExpr->pTab!=0 
      assert( pColExpr->op!=TK_AGG_COLUMN );
      if( pColExpr->op==TK_COLUMN ){
      ){
        /* For columns use the column name name */
        int iCol = pColExpr->iColumn;
        Table *pTab = pColExpr->pTab;
        assert( pTab!=0 );
        if( iCol<0 ) iCol = pTab->iPKey;
        zName = iCol>=0 ? pTab->aCol[iCol].zName : "rowid";
      }else if( pColExpr->op==TK_ID ){
        assert( !ExprHasProperty(pColExpr, EP_IntValue) );
        zName = pColExpr->u.zToken;
      }else{
        /* Use the original text of the column expression as its name */

  }
  return sqlite3VdbeCreate(pParse);
}


/*
** Compute the iLimit and iOffset fields of the SELECT based on the
** pLimit and pOffset expressions.  pLimit and pOffset hold the expressions
** pLimit expressions.  pLimit->pLeft and pLimit->pRight hold the expressions
** that appear in the original SQL statement after the LIMIT and OFFSET
** keywords.  Or NULL if those keywords are omitted. iLimit and iOffset 
** are the integer memory register numbers for counters used to compute 
** the limit and offset.  If there is no limit and/or offset, then 
** iLimit and iOffset are negative.
**
** This routine changes the values of iLimit and iOffset only if
** a limit or offset is defined by pLimit and pOffset.  iLimit and
** iOffset should have been preset to appropriate default values (zero)
** a limit or offset is defined by pLimit->pLeft and pLimit->pRight.  iLimit
** and iOffset should have been preset to appropriate default values (zero)
** prior to calling this routine.
**
** The iOffset register (if it exists) is initialized to the value
** of the OFFSET.  The iLimit register is initialized to LIMIT.  Register
** iOffset+1 is initialized to LIMIT+OFFSET.
**
** Only if pLimit!=0 or pOffset!=0 do the limit registers get
** Only if pLimit->pLeft!=0 do the limit registers get
** redefined.  The UNION ALL operator uses this property to force
** the reuse of the same limit and offset registers across multiple
** SELECT statements.
*/
static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
  Vdbe *v = 0;
  int iLimit = 0;
  int iOffset;
  int n;
  Expr *pLimit = p->pLimit;

  if( p->iLimit ) return;

  /* 
  ** "LIMIT -1" always shows all rows.  There is some
  ** controversy about what the correct behavior should be.
  ** The current implementation interprets "LIMIT 0" to mean
  ** no rows.
  */
  sqlite3ExprCacheClear(pParse);
  assert( p->pOffset==0 || p->pLimit!=0 );
  if( p->pLimit ){
  if( pLimit ){
    assert( pLimit->op==TK_LIMIT );
    assert( pLimit->pLeft!=0 );
    p->iLimit = iLimit = ++pParse->nMem;
    v = sqlite3GetVdbe(pParse);
    assert( v!=0 );
    if( sqlite3ExprIsInteger(p->pLimit, &n) ){
    if( sqlite3ExprIsInteger(pLimit->pLeft, &n) ){
      sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
      VdbeComment((v, "LIMIT counter"));
      if( n==0 ){
        sqlite3VdbeGoto(v, iBreak);
      }else if( n>=0 && p->nSelectRow>sqlite3LogEst((u64)n) ){
        p->nSelectRow = sqlite3LogEst((u64)n);
        p->selFlags |= SF_FixedLimit;
      }
    }else{
      sqlite3ExprCode(pParse, p->pLimit, iLimit);
      sqlite3ExprCode(pParse, pLimit->pLeft, iLimit);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit); VdbeCoverage(v);
      VdbeComment((v, "LIMIT counter"));
      sqlite3VdbeAddOp2(v, OP_IfNot, iLimit, iBreak); VdbeCoverage(v);
    }
    if( p->pOffset ){
    if( pLimit->pRight ){
      p->iOffset = iOffset = ++pParse->nMem;
      pParse->nMem++;   /* Allocate an extra register for limit+offset */
      sqlite3ExprCode(pParse, p->pOffset, iOffset);
      sqlite3ExprCode(pParse, pLimit->pRight, iOffset);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset); VdbeCoverage(v);
      VdbeComment((v, "OFFSET counter"));
      sqlite3VdbeAddOp3(v, OP_OffsetLimit, iLimit, iOffset+1, iOffset);
      VdbeComment((v, "LIMIT+OFFSET"));
    }
  }
}

  int iQueue;                   /* The Queue table */
  int iDistinct = 0;            /* To ensure unique results if UNION */
  int eDest = SRT_Fifo;         /* How to write to Queue */
  SelectDest destQueue;         /* SelectDest targetting the Queue table */
  int i;                        /* Loop counter */
  int rc;                       /* Result code */
  ExprList *pOrderBy;           /* The ORDER BY clause */
  Expr *pLimit, *pOffset;       /* Saved LIMIT and OFFSET */
  Expr *pLimit;                 /* Saved LIMIT and OFFSET */
  int regLimit, regOffset;      /* Registers used by LIMIT and OFFSET */

  /* Obtain authorization to do a recursive query */
  if( sqlite3AuthCheck(pParse, SQLITE_RECURSIVE, 0, 0, 0) ) return;

  /* Process the LIMIT and OFFSET clauses, if they exist */
  addrBreak = sqlite3VdbeMakeLabel(v);
  p->nSelectRow = 320;  /* 4 billion rows */
  computeLimitRegisters(pParse, p, addrBreak);
  pLimit = p->pLimit;
  pOffset = p->pOffset;
  regLimit = p->iLimit;
  regOffset = p->iOffset;
  p->pLimit = p->pOffset = 0;
  p->pLimit = 0;
  p->iLimit = p->iOffset = 0;
  pOrderBy = p->pOrderBy;

  /* Locate the cursor number of the Current table */
  for(i=0; ALWAYS(i<pSrc->nSrc); i++){
    if( pSrc->a[i].fg.isRecursive ){
      iCurrent = pSrc->a[i].iCursor;

  sqlite3VdbeGoto(v, addrTop);
  sqlite3VdbeResolveLabel(v, addrBreak);

end_of_recursive_query:
  sqlite3ExprListDelete(pParse->db, p->pOrderBy);
  p->pOrderBy = pOrderBy;
  p->pLimit = pLimit;
  p->pOffset = pOffset;
  return;
}
#endif /* SQLITE_OMIT_CTE */

/* Forward references */
static int multiSelectOrderBy(
  Parse *pParse,        /* Parsing context */
  Select *p,            /* The right-most of SELECTs to be coded */
  SelectDest *pDest     /* What to do with query results */
);

/*
** Handle the special case of a compound-select that originates from a
** VALUES clause.  By handling this as a special case, we avoid deep
** recursion, and thus do not need to enforce the SQLITE_LIMIT_COMPOUND_SELECT
** on a VALUES clause.
**
** Because the Select object originates from a VALUES clause:
**   (1) It has no LIMIT or OFFSET
**   (1) There is no LIMIT or OFFSET or else there is a LIMIT of exactly 1
**   (2) All terms are UNION ALL
**   (3) There is no ORDER BY clause
**
** The "LIMIT of exactly 1" case of condition (1) comes about when a VALUES
** clause occurs within scalar expression (ex: "SELECT (VALUES(1),(2),(3))").
** The sqlite3CodeSubselect will have added the LIMIT 1 clause in tht case.
** Since the limit is exactly 1, we only need to evalutes the left-most VALUES.
*/
static int multiSelectValues(
  Parse *pParse,        /* Parsing context */
  Select *p,            /* The right-most of SELECTs to be coded */
  SelectDest *pDest     /* What to do with query results */
){
  Select *pPrior;
  Select *pRightmost = p;
  int nRow = 1;
  int rc = 0;
  assert( p->selFlags & SF_MultiValue );
  do{
    assert( p->selFlags & SF_Values );
    assert( p->op==TK_ALL || (p->op==TK_SELECT && p->pPrior==0) );
    assert( p->pLimit==0 );
    assert( p->pOffset==0 );
    assert( p->pNext==0 || p->pEList->nExpr==p->pNext->pEList->nExpr );
    if( p->pPrior==0 ) break;
    assert( p->pPrior->pNext==p );
    p = p->pPrior;
    nRow++;
  }while(1);
  while( p ){
    pPrior = p->pPrior;
    p->pPrior = 0;
    rc = sqlite3Select(pParse, p, pDest);
    p->pPrior = pPrior;
    if( rc ) break;
    if( rc || pRightmost->pLimit ) break;
    p->nSelectRow = nRow;
    p = p->pNext;
  }
  return rc;
}

/*

    case TK_ALL: {
      int addr = 0;
      int nLimit;
      assert( !pPrior->pLimit );
      pPrior->iLimit = p->iLimit;
      pPrior->iOffset = p->iOffset;
      pPrior->pLimit = p->pLimit;
      pPrior->pOffset = p->pOffset;
      explainSetInteger(iSub1, pParse->iNextSelectId);
      rc = sqlite3Select(pParse, pPrior, &dest);
      p->pLimit = 0;
      p->pOffset = 0;
      if( rc ){
        goto multi_select_end;
      }
      p->pPrior = 0;
      p->iLimit = pPrior->iLimit;
      p->iOffset = pPrior->iOffset;
      if( p->iLimit ){

      explainSetInteger(iSub2, pParse->iNextSelectId);
      rc = sqlite3Select(pParse, p, &dest);
      testcase( rc!=SQLITE_OK );
      pDelete = p->pPrior;
      p->pPrior = pPrior;
      p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
      if( pPrior->pLimit
       && sqlite3ExprIsInteger(pPrior->pLimit, &nLimit)
       && sqlite3ExprIsInteger(pPrior->pLimit->pLeft, &nLimit)
       && nLimit>0 && p->nSelectRow > sqlite3LogEst((u64)nLimit) 
      ){
        p->nSelectRow = sqlite3LogEst((u64)nLimit);
      }
      if( addr ){
        sqlite3VdbeJumpHere(v, addr);
      }
      break;
    }
    case TK_EXCEPT:
    case TK_UNION: {
      int unionTab;    /* Cursor number of the temporary table holding result */
      u8 op = 0;       /* One of the SRT_ operations to apply to self */
      int priorOp;     /* The SRT_ operation to apply to prior selects */
      Expr *pLimit, *pOffset; /* Saved values of p->nLimit and p->nOffset */
      Expr *pLimit;    /* Saved values of p->nLimit  */
      int addr;
      SelectDest uniondest;

      testcase( p->op==TK_EXCEPT );
      testcase( p->op==TK_UNION );
      priorOp = SRT_Union;
      if( dest.eDest==priorOp ){
        /* We can reuse a temporary table generated by a SELECT to our
        ** right.
        */
        assert( p->pLimit==0 );      /* Not allowed on leftward elements */
        assert( p->pOffset==0 );     /* Not allowed on leftward elements */
        unionTab = dest.iSDParm;
      }else{
        /* We will need to create our own temporary table to hold the
        ** intermediate results.
        */
        unionTab = pParse->nTab++;
        assert( p->pOrderBy==0 );

      }else{
        assert( p->op==TK_UNION );
        op = SRT_Union;
      }
      p->pPrior = 0;
      pLimit = p->pLimit;
      p->pLimit = 0;
      pOffset = p->pOffset;
      p->pOffset = 0;
      uniondest.eDest = op;
      explainSetInteger(iSub2, pParse->iNextSelectId);
      rc = sqlite3Select(pParse, p, &uniondest);
      testcase( rc!=SQLITE_OK );
      /* Query flattening in sqlite3Select() might refill p->pOrderBy.
      ** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
      sqlite3ExprListDelete(db, p->pOrderBy);
      pDelete = p->pPrior;
      p->pPrior = pPrior;
      p->pOrderBy = 0;
      if( p->op==TK_UNION ){
        p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
      }
      sqlite3ExprDelete(db, p->pLimit);
      p->pLimit = pLimit;
      p->pOffset = pOffset;
      p->iLimit = 0;
      p->iOffset = 0;

      /* Convert the data in the temporary table into whatever form
      ** it is that we currently need.
      */
      assert( unionTab==dest.iSDParm || dest.eDest!=priorOp );

        sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
      }
      break;
    }
    default: assert( p->op==TK_INTERSECT ); {
      int tab1, tab2;
      int iCont, iBreak, iStart;
      Expr *pLimit, *pOffset;
      Expr *pLimit;
      int addr;
      SelectDest intersectdest;
      int r1;

      /* INTERSECT is different from the others since it requires
      ** two temporary tables.  Hence it has its own case.  Begin
      ** by allocating the tables we will need.

      */
      addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
      assert( p->addrOpenEphm[1] == -1 );
      p->addrOpenEphm[1] = addr;
      p->pPrior = 0;
      pLimit = p->pLimit;
      p->pLimit = 0;
      pOffset = p->pOffset;
      p->pOffset = 0;
      intersectdest.iSDParm = tab2;
      explainSetInteger(iSub2, pParse->iNextSelectId);
      rc = sqlite3Select(pParse, p, &intersectdest);
      testcase( rc!=SQLITE_OK );
      pDelete = p->pPrior;
      p->pPrior = pPrior;
      if( p->nSelectRow>pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
      sqlite3ExprDelete(db, p->pLimit);
      p->pLimit = pLimit;
      p->pOffset = pOffset;

      /* Generate code to take the intersection of the two temporary
      ** tables.
      */
      assert( p->pEList );
      iBreak = sqlite3VdbeMakeLabel(v);
      iCont = sqlite3VdbeMakeLabel(v);

                                  regLimitA);
    sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
  }else{
    regLimitA = regLimitB = 0;
  }
  sqlite3ExprDelete(db, p->pLimit);
  p->pLimit = 0;
  sqlite3ExprDelete(db, p->pOffset);
  p->pOffset = 0;

  regAddrA = ++pParse->nMem;
  regAddrB = ++pParse->nMem;
  regOutA = ++pParse->nMem;
  regOutB = ++pParse->nMem;
  sqlite3SelectDestInit(&destA, SRT_Coroutine, regAddrA);
  sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);

**  (18)  If the sub-query is a compound select, then all terms of the
**        ORDER BY clause of the parent must be simple references to 
**        columns of the sub-query.
**
**  (19)  If the subquery uses LIMIT then the outer query may not
**        have a WHERE clause.
**
**  (**)  Subsumed into (17d3).  Was: If the sub-query is a compound select,
**        then it must not use an ORDER BY clause - Ticket #3773.  Because
**        of (17d3), then only way to have a compound subquery is if it is
**        the only term in the FROM clause of the outer query.  But if the
**        only term in the FROM clause has an ORDER BY, then it will be
**  (20)  If the sub-query is a compound select, then it must not use
**        an ORDER BY clause.  Ticket #3773.  We could relax this constraint
**        somewhat by saying that the terms of the ORDER BY clause must
**        appear as unmodified result columns in the outer query.  But we
**        have other optimizations in mind to deal with that case.
**        implemented as a co-routine and the flattener will never be called.
**
**  (21)  If the subquery uses LIMIT then the outer query may not be
**        DISTINCT.  (See ticket [752e1646fc]).
**
**  (22)  The subquery may not be a recursive CTE.
**
**  (**)  Subsumed into restriction (17d3).  Was: If the outer query is

  assert( pSubSrc );
  /* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
  ** not arbitrary expressions, we allowed some combining of LIMIT and OFFSET
  ** because they could be computed at compile-time.  But when LIMIT and OFFSET
  ** became arbitrary expressions, we were forced to add restrictions (13)
  ** and (14). */
  if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
  if( pSub->pOffset ) return 0;                          /* Restriction (14) */
  if( pSub->pLimit && pSub->pLimit->pRight ) return 0;   /* Restriction (14) */
  if( (p->selFlags & SF_Compound)!=0 && pSub->pLimit ){
    return 0;                                            /* Restriction (15) */
  }
  if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
  if( pSub->selFlags & SF_Distinct ) return 0;           /* Restriction (4)  */
  if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
     return 0;         /* Restrictions (8)(9) */

  /* Restriction (17): If the sub-query is a compound SELECT, then it must
  ** use only the UNION ALL operator. And none of the simple select queries
  ** that make up the compound SELECT are allowed to be aggregate or distinct
  ** queries.
  */
  if( pSub->pPrior ){
    if( pSub->pOrderBy ){
      return 0;  /* Restriction (20) */
    }
    if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
      return 0; /* (17d1), (17d2), or (17d3) */
    }
    for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
      testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
      testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
      assert( pSub->pSrc!=0 );

  ** The only way that the recursive part of a CTE can contain a compound
  ** subquery is for the subquery to be one term of a join.  But if the
  ** subquery is a join, then the flattening has already been stopped by
  ** restriction (17d3)
  */
  assert( (p->selFlags & SF_Recursive)==0 || pSub->pPrior==0 );

  /* Ex-restriction (20):
  ** A compound subquery must be the only term in the FROM clause of the
  ** outer query by restriction (17d3).  But if that term also has an
  ** ORDER BY clause, then the subquery will be implemented by co-routine
  ** and so the flattener will never be invoked.  Hence, it is not possible
  ** for the subquery to be a compound and have an ORDER BY clause.
  */
  assert( pSub->pPrior==0 || pSub->pOrderBy==0 );

  /***** If we reach this point, flattening is permitted. *****/
  SELECTTRACE(1,pParse,p,("flatten %s.%p from term %d\n",
                   pSub->zSelName, pSub, iFrom));

  /* Authorize the subquery */
  pParse->zAuthContext = pSubitem->zName;
  TESTONLY(i =) sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);

  **
  ** We call this the "compound-subquery flattening".
  */
  for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
    Select *pNew;
    ExprList *pOrderBy = p->pOrderBy;
    Expr *pLimit = p->pLimit;
    Expr *pOffset = p->pOffset;
    Select *pPrior = p->pPrior;
    p->pOrderBy = 0;
    p->pSrc = 0;
    p->pPrior = 0;
    p->pLimit = 0;
    p->pOffset = 0;
    pNew = sqlite3SelectDup(db, p, 0);
    sqlite3SelectSetName(pNew, pSub->zSelName);
    p->pOffset = pOffset;
    p->pLimit = pLimit;
    p->pOrderBy = pOrderBy;
    p->pSrc = pSrc;
    p->op = TK_ALL;
    if( pNew==0 ){
      p->pPrior = pPrior;
    }else{

    }
  }
  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:
** The pFunc is the only aggregate function in the query.  Check to see
** if the query is a candidate for the min/max optimization. 
**
**    * the query contains just a single aggregate function,
**    * the aggregate function is either min() or max(), and
** If the query is a candidate for the min/max optimization, then set
** *ppMinMax to be an ORDER BY clause to be used for the optimization
** and return either WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX depending on
** whether pFunc is a min() or max() function.
**    * the argument to the aggregate function is a column value.
**
** If the query is not a candidate for the min/max optimization, return
** If all of the above are true, then WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX
** WHERE_ORDERBY_NORMAL (which must be zero).
** is returned as appropriate. Also, *ppMinMax is set to point to the 
** list of arguments passed to the aggregate before returning.
**
** Or, if the conditions above are not met, *ppMinMax is set to 0 and
** WHERE_ORDERBY_NORMAL is returned.
** This routine must be called after aggregate functions have been
** located but before their arguments have been subjected to aggregate
** analysis.
*/
static u8 minMaxQuery(AggInfo *pAggInfo, ExprList **ppMinMax){
  int eRet = WHERE_ORDERBY_NORMAL;          /* Return value */

static u8 minMaxQuery(sqlite3 *db, Expr *pFunc, ExprList **ppMinMax){
  int eRet = WHERE_ORDERBY_NORMAL;      /* Return value */
  ExprList *pEList = pFunc->x.pList;    /* Arguments to agg function */
  *ppMinMax = 0;
  if( pAggInfo->nFunc==1 ){
    Expr *pExpr = pAggInfo->aFunc[0].pExpr; /* Aggregate function */
    ExprList *pEList = pExpr->x.pList;      /* Arguments to agg function */
  const char *zFunc;                    /* Name of aggregate function pFunc */
  ExprList *pOrderBy;
  u8 sortOrder;

  assert( *ppMinMax==0 );
    assert( pExpr->op==TK_AGG_FUNCTION );
    if( pEList && pEList->nExpr==1 && pEList->a[0].pExpr->op==TK_AGG_COLUMN ){
      const char *zFunc = pExpr->u.zToken;
      if( sqlite3StrICmp(zFunc, "min")==0 ){
        eRet = WHERE_ORDERBY_MIN;
        *ppMinMax = pEList;
      }else if( sqlite3StrICmp(zFunc, "max")==0 ){
        eRet = WHERE_ORDERBY_MAX;
        *ppMinMax = pEList;
      }
    }
  assert( pFunc->op==TK_AGG_FUNCTION );
  if( pEList==0 || pEList->nExpr!=1 ) return eRet;
  zFunc = pFunc->u.zToken;
  if( sqlite3StrICmp(zFunc, "min")==0 ){
    eRet = WHERE_ORDERBY_MIN;
    sortOrder = SQLITE_SO_ASC;
  }else if( sqlite3StrICmp(zFunc, "max")==0 ){
    eRet = WHERE_ORDERBY_MAX;
    sortOrder = SQLITE_SO_DESC;
  }else{
    return eRet;
  }
  }

  assert( *ppMinMax==0 || (*ppMinMax)->nExpr==1 );
  *ppMinMax = pOrderBy = sqlite3ExprListDup(db, pEList, 0);
  assert( pOrderBy!=0 || db->mallocFailed );
  if( pOrderBy ) pOrderBy->a[0].sortOrder = sortOrder;
  return eRet;
}

/*
** The select statement passed as the first argument is an aggregate query.
** The second argument is the associated aggregate-info object. This 
** function tests if the SELECT is of the form:

  p->pWith = 0;
  p->selFlags &= ~SF_Compound;
  assert( (p->selFlags & SF_Converted)==0 );
  p->selFlags |= SF_Converted;
  assert( pNew->pPrior!=0 );
  pNew->pPrior->pNext = pNew;
  pNew->pLimit = 0;
  pNew->pOffset = 0;
  return WRC_Continue;
}

/*
** Check to see if the FROM clause term pFrom has table-valued function
** arguments.  If it does, leave an error message in pParse and return
** non-zero, since pFrom is not allowed to be a table-valued function.

  int i, j, k;
  SrcList *pTabList;
  ExprList *pEList;
  struct SrcList_item *pFrom;
  sqlite3 *db = pParse->db;
  Expr *pE, *pRight, *pExpr;
  u16 selFlags = p->selFlags;
  u32 elistFlags = 0;

  p->selFlags |= SF_Expanded;
  if( db->mallocFailed  ){
    return WRC_Abort;
  }
  assert( p->pSrc!=0 );
  if( NEVER(p->pSrc==0) || (selFlags & SF_Expanded)!=0 ){
  if( (selFlags & SF_Expanded)!=0 ){
    return WRC_Prune;
  }
  pTabList = p->pSrc;
  pEList = p->pEList;
  if( OK_IF_ALWAYS_TRUE(p->pWith) ){
    sqlite3WithPush(pParse, p->pWith, 0);
  }

  */
  for(k=0; k<pEList->nExpr; k++){
    pE = pEList->a[k].pExpr;
    if( pE->op==TK_ASTERISK ) break;
    assert( pE->op!=TK_DOT || pE->pRight!=0 );
    assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
    if( pE->op==TK_DOT && pE->pRight->op==TK_ASTERISK ) break;
    elistFlags |= pE->flags;
  }
  if( k<pEList->nExpr ){
    /*
    ** If we get here it means the result set contains one or more "*"
    ** operators that need to be expanded.  Loop through each expression
    ** in the result set and expand them one by one.
    */
    struct ExprList_item *a = pEList->a;
    ExprList *pNew = 0;
    int flags = pParse->db->flags;
    int longNames = (flags & SQLITE_FullColNames)!=0
                      && (flags & SQLITE_ShortColNames)==0;

    for(k=0; k<pEList->nExpr; k++){
      pE = a[k].pExpr;
      elistFlags |= pE->flags;
      pRight = pE->pRight;
      assert( pE->op!=TK_DOT || pRight!=0 );
      if( pE->op!=TK_ASTERISK
       && (pE->op!=TK_DOT || pRight->op!=TK_ASTERISK)
      ){
        /* This particular expression does not need to be expanded.
        */

          }
        }
      }
    }
    sqlite3ExprListDelete(db, pEList);
    p->pEList = pNew;
  }
  if( p->pEList ){
  if( p->pEList && p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
    sqlite3ErrorMsg(pParse, "too many columns in result set");
    return WRC_Abort;
    if( p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
      sqlite3ErrorMsg(pParse, "too many columns in result set");
      return WRC_Abort;
    }
    if( (elistFlags & (EP_HasFunc|EP_Subquery))!=0 ){
      p->selFlags |= SF_ComplexResult;
    }
  }
  return WRC_Continue;
}

/*
** No-op routine for the parse-tree walker.
**

  Expr *pHaving;         /* The HAVING clause.  May be NULL */
  int rc = 1;            /* Value to return from this function */
  DistinctCtx sDistinct; /* Info on how to code the DISTINCT keyword */
  SortCtx sSort;         /* Info on how to code the ORDER BY clause */
  AggInfo sAggInfo;      /* Information used by aggregate queries */
  int iEnd;              /* Address of the end of the query */
  sqlite3 *db;           /* The database connection */
  ExprList *pMinMaxOrderBy = 0;  /* Added ORDER BY for min/max queries */
  u8 minMaxFlag;                 /* Flag for min/max queries */

#ifndef SQLITE_OMIT_EXPLAIN
  int iRestoreSelectId = pParse->iSelectId;
  pParse->iSelectId = pParse->iNextSelectId++;
#endif

  db = pParse->db;

    ** is not a join.  But if the outer query is not a join, then the subquery
    ** will be implemented as a co-routine and there is no advantage to
    ** flattening in that case.
    */
    if( (pSub->selFlags & SF_Aggregate)!=0 ) continue;
    assert( pSub->pGroupBy==0 );

    /* If the outer query contains a "complex" result set (that is,
    ** if the result set of the outer query uses functions or subqueries)
    /* If the subquery contains an ORDER BY clause and if
    ** and if the subquery contains an ORDER BY clause and if
    ** it will be implemented as a co-routine, then do not flatten.  This
    ** restriction allows SQL constructs like this:
    **
    **  SELECT expensive_function(x)
    **    FROM (SELECT x FROM tab ORDER BY y LIMIT 10);
    **
    ** The expensive_function() is only computed on the 10 rows that
    ** are output, rather than every row of the table.
    **
    ** The requirement that the outer query have a complex result set
    ** means that flattening does occur on simpler SQL constraints without
    ** the expensive_function() like:
    **
    **  SELECT x FROM (SELECT x FROM tab ORDER BY y LIMIT 10);
    */
    if( pSub->pOrderBy!=0
     && i==0
     && (p->selFlags & SF_ComplexResult)!=0
     && (pTabList->nSrc==1
         || (pTabList->a[1].fg.jointype&(JT_LEFT|JT_CROSS))!=0)
    ){
      continue;
    }

    if( flattenSubquery(pParse, p, i, isAgg) ){

        assert( pWhere==p->pWhere );
        havingToWhere(pParse, pGroupBy, pHaving, &p->pWhere);
        pWhere = p->pWhere;
      }
      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
    }
    sAggInfo.nAccumulator = sAggInfo.nColumn;
    if( p->pGroupBy==0 && p->pHaving==0 && sAggInfo.nFunc==1 ){
      minMaxFlag = minMaxQuery(db, sAggInfo.aFunc[0].pExpr, &pMinMaxOrderBy);
    }else{
      minMaxFlag = WHERE_ORDERBY_NORMAL;
    }
    for(i=0; i<sAggInfo.nFunc; i++){
      assert( !ExprHasProperty(sAggInfo.aFunc[i].pExpr, EP_xIsSelect) );
      sNC.ncFlags |= NC_InAggFunc;
      sqlite3ExprAnalyzeAggList(&sNC, sAggInfo.aFunc[i].pExpr->x.pList);
      sNC.ncFlags &= ~NC_InAggFunc;
    }
    sAggInfo.mxReg = pParse->nMem;
    if( db->mallocFailed ) goto select_end;
#if SELECTTRACE_ENABLED
    if( sqlite3SelectTrace & 0x400 ){
      int ii;
      SELECTTRACE(0x400,pParse,p,("After aggregate analysis:\n"));
      sqlite3TreeViewSelect(0, p, 0);
      for(ii=0; ii<sAggInfo.nColumn; ii++){
        sqlite3DebugPrintf("agg-column[%d] iMem=%d\n",
            ii, sAggInfo.aCol[ii].iMem);
        sqlite3TreeViewExpr(0, sAggInfo.aCol[ii].pExpr, 0);
      }
      for(ii=0; ii<sAggInfo.nFunc; ii++){
        sqlite3DebugPrintf("agg-func[%d]: iMem=%d\n",
            ii, sAggInfo.aFunc[ii].iMem);
        sqlite3TreeViewExpr(0, sAggInfo.aFunc[ii].pExpr, 0);
      }
    }
#endif


    /* Processing for aggregates with GROUP BY is very different and
    ** much more complex than aggregates without a GROUP BY.
    */
    if( pGroupBy ){
      KeyInfo *pKeyInfo;  /* Keying information for the group by clause */
      int addr1;          /* A-vs-B comparision jump */

      */
      sqlite3VdbeResolveLabel(v, addrReset);
      resetAccumulator(pParse, &sAggInfo);
      sqlite3VdbeAddOp1(v, OP_Return, regReset);
     
    } /* endif pGroupBy.  Begin aggregate queries without GROUP BY: */
    else {
      ExprList *pDel = 0;
#ifndef SQLITE_OMIT_BTREECOUNT
      Table *pTab;
      if( (pTab = isSimpleCount(p, &sAggInfo))!=0 ){
        /* If isSimpleCount() returns a pointer to a Table structure, then
        ** the SQL statement is of the form:
        **
        **   SELECT count(*) FROM <tbl>

        }
        sqlite3VdbeAddOp2(v, OP_Count, iCsr, sAggInfo.aFunc[0].iMem);
        sqlite3VdbeAddOp1(v, OP_Close, iCsr);
        explainSimpleCount(pParse, pTab, pBest);
      }else
#endif /* SQLITE_OMIT_BTREECOUNT */
      {
        /* Check if the query is of one of the following forms:
        /* This case runs if the aggregate has no GROUP BY clause.  The
        **
        **   SELECT min(x) FROM ...
        **   SELECT max(x) FROM ...
        **
        ** If it is, then ask the code in where.c to attempt to sort results
        ** as if there was an "ORDER ON x" or "ORDER ON x DESC" clause. 
        ** If where.c is able to produce results sorted in this order, then
        ** add vdbe code to break out of the processing loop after the 
        ** processing is much simpler since there is only a single row
        ** first iteration (since the first iteration of the loop is 
        ** guaranteed to operate on the row with the minimum or maximum 
        ** value of x, the only row required).
        **
        ** of output.
        ** A special flag must be passed to sqlite3WhereBegin() to slightly
        ** modify behavior as follows:
        **
        **   + If the query is a "SELECT min(x)", then the loop coded by
        **     where.c should not iterate over any values with a NULL value
        **     for x.
        **
        **   + The optimizer code in where.c (the thing that decides which
        **     index or indices to use) should place a different priority on 
        **     satisfying the 'ORDER BY' clause than it does in other cases.
        **     Refer to code and comments in where.c for details.
        */
        ExprList *pMinMax = 0;
        u8 flag = WHERE_ORDERBY_NORMAL;
        
        assert( p->pGroupBy==0 );
        assert( flag==0 );
        if( p->pHaving==0 ){
          flag = minMaxQuery(&sAggInfo, &pMinMax);
        }
        resetAccumulator(pParse, &sAggInfo);

        assert( flag==0 || (pMinMax!=0 && pMinMax->nExpr==1) );

        /* If this query is a candidate for the min/max optimization, then
        if( flag ){
          pMinMax = sqlite3ExprListDup(db, pMinMax, 0);
          pDel = pMinMax;
        ** minMaxFlag will have been previously set to either
          assert( db->mallocFailed || pMinMax!=0 );
          if( !db->mallocFailed ){
            pMinMax->a[0].sortOrder = flag!=WHERE_ORDERBY_MIN ?1:0;
        ** WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX and pMinMaxOrderBy will
            pMinMax->a[0].pExpr->op = TK_COLUMN;
          }
        }
  
        ** be an appropriate ORDER BY expression for the optimization.
        /* This case runs if the aggregate has no GROUP BY clause.  The
        ** processing is much simpler since there is only a single row
        ** of output.
        */
        assert( minMaxFlag==WHERE_ORDERBY_NORMAL || pMinMaxOrderBy!=0 );
        assert( pMinMaxOrderBy==0 || pMinMaxOrderBy->nExpr==1 );
        resetAccumulator(pParse, &sAggInfo);
        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pMinMax, 0,flag,0);

        pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, pMinMaxOrderBy,
                                   0, minMaxFlag, 0);
        if( pWInfo==0 ){
          sqlite3ExprListDelete(db, pDel);
          goto select_end;
        }
        updateAccumulator(pParse, &sAggInfo);
        assert( pMinMax==0 || pMinMax->nExpr==1 );
        if( sqlite3WhereIsOrdered(pWInfo)>0 ){
          sqlite3VdbeGoto(v, sqlite3WhereBreakLabel(pWInfo));
          VdbeComment((v, "%s() by index",
                (flag==WHERE_ORDERBY_MIN?"min":"max")));
                (minMaxFlag==WHERE_ORDERBY_MIN?"min":"max")));
        }
        sqlite3WhereEnd(pWInfo);
        finalizeAggFunctions(pParse, &sAggInfo);
      }

      sSort.pOrderBy = 0;
      sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
      selectInnerLoop(pParse, p, -1, 0, 0, 
                      pDest, addrEnd, addrEnd);
      sqlite3ExprListDelete(db, pDel);
    }
    sqlite3VdbeResolveLabel(v, addrEnd);
    
  } /* endif aggregate query */

  if( sDistinct.eTnctType==WHERE_DISTINCT_UNORDERED ){
    explainTempTable(pParse, "DISTINCT");

  rc = (pParse->nErr>0);

  /* Control jumps to here if an error is encountered above, or upon
  ** successful coding of the SELECT.
  */
select_end:
  explainSetInteger(pParse->iSelectId, iRestoreSelectId);

  sqlite3ExprListDelete(db, pMinMaxOrderBy);
  sqlite3DbFree(db, sAggInfo.aCol);
  sqlite3DbFree(db, sAggInfo.aFunc);
#if SELECTTRACE_ENABLED
  SELECTTRACE(1,pParse,p,("end processing\n"));
  pParse->nSelectIndent--;
#endif
  return rc;

    TriggerStep * pTmp = pTriggerStep;
    pTriggerStep = pTriggerStep->pNext;

    sqlite3ExprDelete(db, pTmp->pWhere);
    sqlite3ExprListDelete(db, pTmp->pExprList);
    sqlite3SelectDelete(db, pTmp->pSelect);
    sqlite3IdListDelete(db, pTmp->pIdList);
    sqlite3DbFree(db, pTmp->zSpan);

    sqlite3DbFree(db, pTmp);
  }
}

/*
** Given table pTab, return a list of all the triggers attached to 

triggerfinish_cleanup:
  sqlite3DeleteTrigger(db, pTrig);
  assert( !pParse->pNewTrigger );
  sqlite3DeleteTriggerStep(db, pStepList);
}

/*
** Duplicate a range of text from an SQL statement, then convert all
** whitespace characters into ordinary space characters.
*/
static char *triggerSpanDup(sqlite3 *db, const char *zStart, const char *zEnd){
  char *z = sqlite3DbSpanDup(db, zStart, zEnd);
  int i;
  if( z ) for(i=0; z[i]; i++) if( sqlite3Isspace(z[i]) ) z[i] = ' ';
  return z;
}    

/*
** Turn a SELECT statement (that the pSelect parameter points to) into
** a trigger step.  Return a pointer to a TriggerStep structure.
**
** The parser calls this routine when it finds a SELECT statement in
** body of a TRIGGER.  
*/
SQLITE_PRIVATE TriggerStep *sqlite3TriggerSelectStep(sqlite3 *db, Select *pSelect){
SQLITE_PRIVATE TriggerStep *sqlite3TriggerSelectStep(
  sqlite3 *db,                /* Database connection */
  Select *pSelect,            /* The SELECT statement */
  const char *zStart,         /* Start of SQL text */
  const char *zEnd            /* End of SQL text */
){
  TriggerStep *pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep));
  if( pTriggerStep==0 ) {
    sqlite3SelectDelete(db, pSelect);
    return 0;
  }
  pTriggerStep->op = TK_SELECT;
  pTriggerStep->pSelect = pSelect;
  pTriggerStep->orconf = OE_Default;
  pTriggerStep->zSpan = triggerSpanDup(db, zStart, zEnd);
  return pTriggerStep;
}

/*
** Allocate space to hold a new trigger step.  The allocated space
** holds both the TriggerStep object and the TriggerStep.target.z string.
**
** If an OOM error occurs, NULL is returned and db->mallocFailed is set.
*/
static TriggerStep *triggerStepAllocate(
  sqlite3 *db,                /* Database connection */
  u8 op,                      /* Trigger opcode */
  Token *pName                /* The target name */
  Token *pName,               /* The target name */
  const char *zStart,         /* Start of SQL text */
  const char *zEnd            /* End of SQL text */
){
  TriggerStep *pTriggerStep;

  pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep) + pName->n + 1);
  if( pTriggerStep ){
    char *z = (char*)&pTriggerStep[1];
    memcpy(z, pName->z, pName->n);
    sqlite3Dequote(z);
    pTriggerStep->zTarget = z;
    pTriggerStep->op = op;
    pTriggerStep->zSpan = triggerSpanDup(db, zStart, zEnd);
  }
  return pTriggerStep;
}

/*
** Build a trigger step out of an INSERT statement.  Return a pointer
** to the new trigger step.
**
** The parser calls this routine when it sees an INSERT inside the
** body of a trigger.
*/
SQLITE_PRIVATE TriggerStep *sqlite3TriggerInsertStep(
  sqlite3 *db,        /* The database connection */
  Token *pTableName,  /* Name of the table into which we insert */
  IdList *pColumn,    /* List of columns in pTableName to insert into */
  Select *pSelect,    /* A SELECT statement that supplies values */
  u8 orconf           /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
  u8 orconf,          /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
  const char *zStart, /* Start of SQL text */
  const char *zEnd    /* End of SQL text */
){
  TriggerStep *pTriggerStep;

  assert(pSelect != 0 || db->mallocFailed);

  pTriggerStep = triggerStepAllocate(db, TK_INSERT, pTableName);
  pTriggerStep = triggerStepAllocate(db, TK_INSERT, pTableName, zStart, zEnd);
  if( pTriggerStep ){
    pTriggerStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
    pTriggerStep->pIdList = pColumn;
    pTriggerStep->orconf = orconf;
  }else{
    sqlite3IdListDelete(db, pColumn);
  }

** sees an UPDATE statement inside the body of a CREATE TRIGGER.
*/
SQLITE_PRIVATE TriggerStep *sqlite3TriggerUpdateStep(
  sqlite3 *db,         /* The database connection */
  Token *pTableName,   /* Name of the table to be updated */
  ExprList *pEList,    /* The SET clause: list of column and new values */
  Expr *pWhere,        /* The WHERE clause */
  u8 orconf            /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
  u8 orconf,           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
  const char *zStart,  /* Start of SQL text */
  const char *zEnd     /* End of SQL text */
){
  TriggerStep *pTriggerStep;

  pTriggerStep = triggerStepAllocate(db, TK_UPDATE, pTableName);
  pTriggerStep = triggerStepAllocate(db, TK_UPDATE, pTableName, zStart, zEnd);
  if( pTriggerStep ){
    pTriggerStep->pExprList = sqlite3ExprListDup(db, pEList, EXPRDUP_REDUCE);
    pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
    pTriggerStep->orconf = orconf;
  }
  sqlite3ExprListDelete(db, pEList);
  sqlite3ExprDelete(db, pWhere);
  return pTriggerStep;
}

/*
** Construct a trigger step that implements a DELETE statement and return
** a pointer to that trigger step.  The parser calls this routine when it
** sees a DELETE statement inside the body of a CREATE TRIGGER.
*/
SQLITE_PRIVATE TriggerStep *sqlite3TriggerDeleteStep(
  sqlite3 *db,            /* Database connection */
  Token *pTableName,      /* The table from which rows are deleted */
  Expr *pWhere            /* The WHERE clause */
  Expr *pWhere,           /* The WHERE clause */
  const char *zStart,     /* Start of SQL text */
  const char *zEnd        /* End of SQL text */
){
  TriggerStep *pTriggerStep;

  pTriggerStep = triggerStepAllocate(db, TK_DELETE, pTableName);
  pTriggerStep = triggerStepAllocate(db, TK_DELETE, pTableName, zStart, zEnd);
  if( pTriggerStep ){
    pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
    pTriggerStep->orconf = OE_Default;
  }
  sqlite3ExprDelete(db, pWhere);
  return pTriggerStep;
}

    **   END;
    **
    **   INSERT INTO t1 ... ;            -- insert into t2 uses REPLACE policy
    **   INSERT OR IGNORE INTO t1 ... ;  -- insert into t2 uses IGNORE policy
    */
    pParse->eOrconf = (orconf==OE_Default)?pStep->orconf:(u8)orconf;
    assert( pParse->okConstFactor==0 );

#ifndef SQLITE_OMIT_TRACE
    if( pStep->zSpan ){
      sqlite3VdbeAddOp4(v, OP_Trace, 0x7fffffff, 1, 0,
                        sqlite3MPrintf(db, "-- %s", pStep->zSpan),
                        P4_DYNAMIC);
    }
#endif

    switch( pStep->op ){
      case TK_UPDATE: {
        sqlite3Update(pParse, 
          targetSrcList(pParse, pStep),
          sqlite3ExprListDup(db, pStep->pExprList, 0), 
          sqlite3ExprDup(db, pStep->pWhere, 0), 
          pParse->eOrconf
          pParse->eOrconf, 0, 0
        );
        break;
      }
      case TK_INSERT: {
        sqlite3Insert(pParse, 
          targetSrcList(pParse, pStep),
          sqlite3SelectDup(db, pStep->pSelect, 0), 
          sqlite3IdListDup(db, pStep->pIdList), 
          pParse->eOrconf
        );
        break;
      }
      case TK_DELETE: {
        sqlite3DeleteFrom(pParse, 
          targetSrcList(pParse, pStep),
          sqlite3ExprDup(db, pStep->pWhere, 0)
          sqlite3ExprDup(db, pStep->pWhere, 0), 0, 0
        );
        break;
      }
      default: assert( pStep->op==TK_SELECT ); {
        SelectDest sDest;
        Select *pSelect = sqlite3SelectDup(db, pStep->pSelect, 0);
        sqlite3SelectDestInit(&sDest, SRT_Discard, 0);

      (pTrigger->tr_tm==TRIGGER_BEFORE ? "BEFORE" : "AFTER"),
        (pTrigger->op==TK_UPDATE ? "UPDATE" : ""),
        (pTrigger->op==TK_INSERT ? "INSERT" : ""),
        (pTrigger->op==TK_DELETE ? "DELETE" : ""),
      pTab->zName
    ));
#ifndef SQLITE_OMIT_TRACE
    if( pTrigger->zName ){
    sqlite3VdbeChangeP4(v, -1, 
      sqlite3MPrintf(db, "-- TRIGGER %s", pTrigger->zName), P4_DYNAMIC
    );
      sqlite3VdbeChangeP4(v, -1, 
        sqlite3MPrintf(db, "-- TRIGGER %s", pTrigger->zName), P4_DYNAMIC
      );
    }
#endif

    /* If one was specified, code the WHEN clause. If it evaluates to false
    ** (or NULL) the sub-vdbe is immediately halted by jumping to the 
    ** OP_Halt inserted at the end of the program.  */
    if( pTrigger->pWhen ){
      pWhen = sqlite3ExprDup(db, pTrigger->pWhen, 0);

    if( iEndTrigger ){
      sqlite3VdbeResolveLabel(v, iEndTrigger);
    }
    sqlite3VdbeAddOp0(v, OP_Halt);
    VdbeComment((v, "End: %s.%s", pTrigger->zName, onErrorText(orconf)));

    transferParseError(pParse, pSubParse);
    if( db->mallocFailed==0 ){
    if( db->mallocFailed==0 && pParse->nErr==0 ){
      pProgram->aOp = sqlite3VdbeTakeOpArray(v, &pProgram->nOp, &pTop->nMaxArg);
    }
    pProgram->nMem = pSubParse->nMem;
    pProgram->nCsr = pSubParse->nTab;
    pProgram->token = (void *)pTrigger;
    pPrg->aColmask[0] = pSubParse->oldmask;
    pPrg->aColmask[1] = pSubParse->newmask;

*            onError   pTabList      pChanges             pWhere
*/
SQLITE_PRIVATE void sqlite3Update(
  Parse *pParse,         /* The parser context */
  SrcList *pTabList,     /* The table in which we should change things */
  ExprList *pChanges,    /* Things to be changed */
  Expr *pWhere,          /* The WHERE clause.  May be null */
  int onError            /* How to handle constraint errors */
  int onError,           /* How to handle constraint errors */
  ExprList *pOrderBy,    /* ORDER BY clause. May be null */
  Expr *pLimit           /* LIMIT clause. May be null */
){
  int i, j;              /* Loop counters */
  Table *pTab;           /* The table to be updated */
  int addrTop = 0;       /* VDBE instruction address of the start of the loop */
  WhereInfo *pWInfo;     /* Information about the WHERE clause */
  Vdbe *v;               /* The virtual database engine */
  Index *pIdx;           /* For looping over indices */

# define isView 0
# define tmask 0
#endif
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif

#ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
  if( !isView ){
    pWhere = sqlite3LimitWhere(
        pParse, pTabList, pWhere, pOrderBy, pLimit, "UPDATE"
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto update_cleanup;
  }
  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
    goto update_cleanup;
  }

  }

  /* If we are trying to update a view, realize that view into
  ** an ephemeral table.
  */
#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
  if( isView ){
    sqlite3MaterializeView(pParse, pTab, pWhere, iDataCur);
    sqlite3MaterializeView(pParse, pTab, 
        pWhere, pOrderBy, pLimit, iDataCur
    );
    pOrderBy = 0;
    pLimit = 0;
  }
#endif

  /* Resolve the column names in all the expressions in the
  ** WHERE clause.
  */
  if( sqlite3ResolveExprNames(&sNC, pWhere) ){

update_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqlite3DbFree(db, aXRef); /* Also frees aRegIdx[] and aToOpen[] */
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprListDelete(db, pChanges);
  sqlite3ExprDelete(db, pWhere);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) 
  sqlite3ExprListDelete(db, pOrderBy);
  sqlite3ExprDelete(db, pLimit);
#endif
  return;
}
/* Make sure "isView" and other macros defined above are undefined. Otherwise
** they may interfere with compilation of other functions in this file
** (or in another file, if this file becomes part of the amalgamation).  */
#ifdef isView
 #undef isView

  int regRec;                     /* Register in which to assemble record */
  int regRowid;                   /* Register for ephem table rowid */
  int iCsr = pSrc->a[0].iCursor;  /* Cursor used for virtual table scan */
  int aDummy[2];                  /* Unused arg for sqlite3WhereOkOnePass() */
  int bOnePass;                   /* True to use onepass strategy */
  int addr;                       /* Address of OP_OpenEphemeral */

  /* Allocate nArg registers to martial the arguments to VUpdate. Then
  /* Allocate nArg registers in which to gather the arguments for VUpdate. Then
  ** create and open the ephemeral table in which the records created from
  ** these arguments will be temporarily stored. */
  assert( v );
  ephemTab = pParse->nTab++;
  addr= sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, nArg);
  regArg = pParse->nMem + 1;
  pParse->nMem += nArg;
  regRec = ++pParse->nMem;
  regRowid = ++pParse->nMem;

  /* Start scanning the virtual table */
  pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0,0,WHERE_ONEPASS_DESIRED,0);
  if( pWInfo==0 ) return;

  /* Populate the argument registers. */
  for(i=0; i<pTab->nCol; i++){
    if( aXRef[i]>=0 ){
      sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
    }else{
      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
      sqlite3VdbeChangeP5(v, 1); /* Enable sqlite3_vtab_nochange() */
    }
  }
  if( HasRowid(pTab) ){
    sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg);
    if( pRowid ){
      sqlite3ExprCode(pParse, pRowid, regArg+1);
    }else{

    if( sqlite3IsToplevel(pParse) ){
      pParse->isMultiWrite = 0;
    }
  }else{
    /* Create a record from the argument register contents and insert it into
    ** the ephemeral table. */
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regArg, nArg, regRec);
#ifdef SQLITE_DEBUG
    /* Signal an assert() within OP_MakeRecord that it is allowed to
    ** accept no-change records with serial_type 10 */
    sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG_MAGIC);
#endif
    sqlite3VdbeAddOp2(v, OP_NewRowid, ephemTab, regRowid);
    sqlite3VdbeAddOp3(v, OP_Insert, ephemTab, regRec, regRowid);
  }


  if( bOnePass==0 ){
    /* End the virtual table scan */

  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() */
){
  int ret = 0;
#if !defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_STMT_SCANSTATUS)
  if( pParse->explain==2 )
  if( sqlite3ParseToplevel(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. */

** 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 void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
  int nLoop = 0;
  while( ALWAYS(pTerm!=0)
      && (pTerm->wtFlags & TERM_CODED)==0
  assert( pTerm!=0 );
  while( (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];
    assert( pTerm!=0 );
    pTerm->nChild--;
    if( pTerm->nChild!=0 ) break;
    nLoop++;
  }
}

/*

    if( sqlite3CompareAffinity(p, zAff[i])==SQLITE_AFF_BLOB
     || sqlite3ExprNeedsNoAffinityChange(p, zAff[i])
    ){
      zAff[i] = SQLITE_AFF_BLOB;
    }
  }
}


/*
** pX is an expression of the form:  (vector) IN (SELECT ...)
** In other words, it is a vector IN operator with a SELECT clause on the
** LHS.  But not all terms in the vector are indexable and the terms might
** not be in the correct order for indexing.
**
** This routine makes a copy of the input pX expression and then adjusts
** the vector on the LHS with corresponding changes to the SELECT so that
** the vector contains only index terms and those terms are in the correct
** order.  The modified IN expression is returned.  The caller is responsible
** for deleting the returned expression.
**
** Example:
**
**    CREATE TABLE t1(a,b,c,d,e,f);
**    CREATE INDEX t1x1 ON t1(e,c);
**    SELECT * FROM t1 WHERE (a,b,c,d,e) IN (SELECT v,w,x,y,z FROM t2)
**                           \_______________________________________/
**                                     The pX expression
**
** Since only columns e and c can be used with the index, in that order,
** the modified IN expression that is returned will be:
**
**        (e,c) IN (SELECT z,x FROM t2)
**
** The reduced pX is different from the original (obviously) and thus is
** only used for indexing, to improve performance.  The original unaltered
** IN expression must also be run on each output row for correctness.
*/
static Expr *removeUnindexableInClauseTerms(
  Parse *pParse,        /* The parsing context */
  int iEq,              /* Look at loop terms starting here */
  WhereLoop *pLoop,     /* The current loop */
  Expr *pX              /* The IN expression to be reduced */
){
  sqlite3 *db = pParse->db;
  Expr *pNew = sqlite3ExprDup(db, pX, 0);
  if( db->mallocFailed==0 ){
    ExprList *pOrigRhs = pNew->x.pSelect->pEList;  /* Original unmodified RHS */
    ExprList *pOrigLhs = pNew->pLeft->x.pList;     /* Original unmodified LHS */
    ExprList *pRhs = 0;         /* New RHS after modifications */
    ExprList *pLhs = 0;         /* New LHS after mods */
    int i;                      /* Loop counter */
    Select *pSelect;            /* Pointer to the SELECT on the RHS */

    for(i=iEq; i<pLoop->nLTerm; i++){
      if( pLoop->aLTerm[i]->pExpr==pX ){
        int iField = pLoop->aLTerm[i]->iField - 1;
        assert( pOrigRhs->a[iField].pExpr!=0 );
        pRhs = sqlite3ExprListAppend(pParse, pRhs, pOrigRhs->a[iField].pExpr);
        pOrigRhs->a[iField].pExpr = 0;
        assert( pOrigLhs->a[iField].pExpr!=0 );
        pLhs = sqlite3ExprListAppend(pParse, pLhs, pOrigLhs->a[iField].pExpr);
        pOrigLhs->a[iField].pExpr = 0;
      }
    }
    sqlite3ExprListDelete(db, pOrigRhs);
    sqlite3ExprListDelete(db, pOrigLhs);
    pNew->pLeft->x.pList = pLhs;
    pNew->x.pSelect->pEList = pRhs;
    if( pLhs && pLhs->nExpr==1 ){
      /* Take care here not to generate a TK_VECTOR containing only a
      ** single value. Since the parser never creates such a vector, some
      ** of the subroutines do not handle this case.  */
      Expr *p = pLhs->a[0].pExpr;
      pLhs->a[0].pExpr = 0;
      sqlite3ExprDelete(db, pNew->pLeft);
      pNew->pLeft = p;
    }
    pSelect = pNew->x.pSelect;
    if( pSelect->pOrderBy ){
      /* If the SELECT statement has an ORDER BY clause, zero the 
      ** iOrderByCol variables. These are set to non-zero when an 
      ** ORDER BY term exactly matches one of the terms of the 
      ** result-set. Since the result-set of the SELECT statement may
      ** have been modified or reordered, these variables are no longer 
      ** set correctly.  Since setting them is just an optimization, 
      ** it's easiest just to zero them here.  */
      ExprList *pOrderBy = pSelect->pOrderBy;
      for(i=0; i<pOrderBy->nExpr; i++){
        pOrderBy->a[i].u.x.iOrderByCol = 0;
      }
    }

#if 0
    printf("For indexing, change the IN expr:\n");
    sqlite3TreeViewExpr(0, pX, 0);
    printf("Into:\n");
    sqlite3TreeViewExpr(0, pNew, 0);
#endif
  }
  return pNew;
}


/*
** 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 a register, the index

    for(i=0; i<iEq; i++){
      if( pLoop->aLTerm[i] && pLoop->aLTerm[i]->pExpr==pX ){
        disableTerm(pLevel, pTerm);
        return iTarget;
      }
    }
    for(i=iEq;i<pLoop->nLTerm; i++){
      assert( pLoop->aLTerm[i]!=0 );
      if( ALWAYS(pLoop->aLTerm[i]) && pLoop->aLTerm[i]->pExpr==pX ) nEq++;
      if( pLoop->aLTerm[i]->pExpr==pX ) nEq++;
    }

    if( (pX->flags & EP_xIsSelect)==0 || pX->x.pSelect->pEList->nExpr==1 ){
      eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, 0);
    }else{
      Select *pSelect = pX->x.pSelect;
      sqlite3 *db = pParse->db;
      u16 savedDbOptFlags = db->dbOptFlags;
      ExprList *pOrigRhs = pSelect->pEList;
      ExprList *pOrigLhs = pX->pLeft->x.pList;
      ExprList *pRhs = 0;         /* New Select.pEList for RHS */
      ExprList *pLhs = 0;         /* New pX->pLeft vector */

      pX = removeUnindexableInClauseTerms(pParse, iEq, pLoop, pX);
      for(i=iEq;i<pLoop->nLTerm; i++){
        if( pLoop->aLTerm[i]->pExpr==pX ){
          int iField = pLoop->aLTerm[i]->iField - 1;
          Expr *pNewRhs = sqlite3ExprDup(db, pOrigRhs->a[iField].pExpr, 0);
          Expr *pNewLhs = sqlite3ExprDup(db, pOrigLhs->a[iField].pExpr, 0);

          pRhs = sqlite3ExprListAppend(pParse, pRhs, pNewRhs);
          pLhs = sqlite3ExprListAppend(pParse, pLhs, pNewLhs);
        }
      }
      if( !db->mallocFailed ){
        Expr *pLeft = pX->pLeft;

        if( pSelect->pOrderBy ){
          /* If the SELECT statement has an ORDER BY clause, zero the 
          ** iOrderByCol variables. These are set to non-zero when an 
          ** ORDER BY term exactly matches one of the terms of the 
          ** result-set. Since the result-set of the SELECT statement may
          ** have been modified or reordered, these variables are no longer 
          ** set correctly.  Since setting them is just an optimization, 
          ** it's easiest just to zero them here.  */
          ExprList *pOrderBy = pSelect->pOrderBy;
          for(i=0; i<pOrderBy->nExpr; i++){
            pOrderBy->a[i].u.x.iOrderByCol = 0;
          }
        }

        /* Take care here not to generate a TK_VECTOR containing only a
        ** single value. Since the parser never creates such a vector, some
        ** of the subroutines do not handle this case.  */
        if( pLhs->nExpr==1 ){
          pX->pLeft = pLhs->a[0].pExpr;
        }else{
          pLeft->x.pList = pLhs;
          aiMap = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int) * nEq);
        aiMap = (int*)sqlite3DbMallocZero(pParse->db, sizeof(int)*nEq);
          testcase( aiMap==0 );
        }
        pSelect->pEList = pRhs;
        db->dbOptFlags |= SQLITE_QueryFlattener;
        eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0, aiMap);
        db->dbOptFlags = savedDbOptFlags;
        testcase( aiMap!=0 && aiMap[0]!=0 );
        pSelect->pEList = pOrigRhs;
        pLeft->x.pList = pOrigLhs;
        pX->pLeft = pLeft;
        pTerm->pExpr->iTable = pX->iTable;
      }
      sqlite3ExprListDelete(pParse->db, pLhs);
      sqlite3ExprListDelete(pParse->db, pRhs);
      sqlite3ExprDelete(db, pX);
      pX = pTerm->pExpr;
    }

    if( eType==IN_INDEX_INDEX_DESC ){
      testcase( bRev );
      bRev = !bRev;
    }
    iTab = pX->iTable;

      if( sqlite3ExprIsVector(pRight)==0 ){
        disableTerm(pLevel, pRangeEnd);
      }else{
        endEq = 1;
      }
    }else if( bStopAtNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      endEq = 0;
      nConstraint++;
    }
    sqlite3DbFree(db, zStartAff);
    sqlite3DbFree(db, zEndAff);

    /* Top of the loop body */

  Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
  Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
  int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
  int noCase = 0;                  /* uppercase equivalent to lowercase */
  int op;                          /* Top-level operator.  pExpr->op */
  Parse *pParse = pWInfo->pParse;  /* Parsing context */
  sqlite3 *db = pParse->db;        /* Database connection */
  unsigned char eOp2;              /* op2 value for LIKE/REGEXP/GLOB */
  unsigned char eOp2 = 0;          /* op2 value for LIKE/REGEXP/GLOB */
  int nLeft;                       /* Number of elements on left side vector */

  if( db->mallocFailed ){
    return;
  }
  pTerm = &pWC->a[idxTerm];
  pMaskSet = &pWInfo->sMaskSet;

  ** not normally optimized for ordinary tables.  In other words, OP
  ** is one of MATCH, LIKE, GLOB, REGEXP, !=, IS, IS NOT, or NOT NULL.
  ** This information is used by the xBestIndex methods of
  ** virtual tables.  The native query optimizer does not attempt
  ** to do anything with MATCH functions.
  */
  if( pWC->op==TK_AND ){
    Expr *pRight, *pLeft;
    Expr *pRight = 0, *pLeft = 0;
    int res = isAuxiliaryVtabOperator(pExpr, &eOp2, &pLeft, &pRight);
    while( res-- > 0 ){
      int idxNew;
      WhereTerm *pNewTerm;
      Bitmask prereqColumn, prereqExpr;

      prereqExpr = sqlite3WhereExprUsage(pMaskSet, pRight);

** 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".
*/
/* #include "sqliteInt.h" */
/* #include "whereInt.h" */

/*
** Extra information appended to the end of sqlite3_index_info but not
** visible to the xBestIndex function, at least not directly.  The
** sqlite3_vtab_collation() interface knows how to reach it, however.
**
** This object is not an API and can be changed from one release to the
** next.  As long as allocateIndexInfo() and sqlite3_vtab_collation()
** agree on the structure, all will be well.
*/
typedef struct HiddenIndexInfo HiddenIndexInfo;
struct HiddenIndexInfo {
  WhereClause *pWC;   /* The Where clause being analyzed */
  Parse *pParse;      /* The parsing context */
};

/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);

/* Test variable that can be set to enable WHERE tracing */
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
/***/ int sqlite3WhereTrace = 0;

#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,
  Parse *pParse,                  /* The parsing context */
  WhereClause *pWC,               /* The WHERE clause being analyzed */
  Bitmask mUnusable,              /* Ignore terms with these prereqs */
  struct SrcList_item *pSrc,
  ExprList *pOrderBy,
  struct SrcList_item *pSrc,      /* The FROM clause term that is the vtab */
  ExprList *pOrderBy,             /* The ORDER BY clause */
  u16 *pmNoOmit                   /* Mask of terms not to omit */
){
  int i, j;
  int nTerm;
  struct sqlite3_index_constraint *pIdxCons;
  struct sqlite3_index_orderby *pIdxOrderBy;
  struct sqlite3_index_constraint_usage *pUsage;
  struct HiddenIndexInfo *pHidden;
  WhereTerm *pTerm;
  int nOrderBy;
  sqlite3_index_info *pIdxInfo;
  u16 mNoOmit = 0;

  /* Count the number of possible WHERE clause constraints referring
  ** to this virtual table */

    }
  }

  /* Allocate the sqlite3_index_info structure
  */
  pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
                           + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
                           + sizeof(*pIdxOrderBy)*nOrderBy );
                           + sizeof(*pIdxOrderBy)*nOrderBy + sizeof(*pHidden) );
  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.
  */
  pHidden = (struct HiddenIndexInfo*)&pIdxInfo[1];
  pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
  pIdxCons = (struct sqlite3_index_constraint*)&pHidden[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;

  pHidden->pWC = pWC;
  pHidden->pParse = pParse;
  for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    u16 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 );

  sqlite3DbFreeNN(db, p);
}

/*
** Free a WhereInfo structure
*/
static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
  if( ALWAYS(pWInfo) ){
    int i;
    for(i=0; i<pWInfo->nLevel; i++){
      WhereLevel *pLevel = &pWInfo->a[i];
      if( pLevel->pWLoop && (pLevel->pWLoop->wsFlags & WHERE_IN_ABLE) ){
        sqlite3DbFree(db, pLevel->u.in.aInLoop);
      }
    }
    sqlite3WhereClauseClear(&pWInfo->sWC);
    while( pWInfo->pLoops ){
      WhereLoop *p = pWInfo->pLoops;
      pWInfo->pLoops = p->pNextLoop;
      whereLoopDelete(db, p);
    }
    sqlite3DbFreeNN(db, pWInfo);
  int i;
  assert( pWInfo!=0 );
  for(i=0; i<pWInfo->nLevel; i++){
    WhereLevel *pLevel = &pWInfo->a[i];
    if( pLevel->pWLoop && (pLevel->pWLoop->wsFlags & WHERE_IN_ABLE) ){
      sqlite3DbFree(db, pLevel->u.in.aInLoop);
    }
  }
  sqlite3WhereClauseClear(&pWInfo->sWC);
  while( pWInfo->pLoops ){
    WhereLoop *p = pWInfo->pLoops;
    pWInfo->pLoops = p->pNextLoop;
    whereLoopDelete(db, p);
  }
  sqlite3DbFreeNN(db, pWInfo);
  }
}

/*
** Return TRUE if all of the following are true:
**
**   (1)  X has the same or lower cost that Y
**   (2)  X uses fewer WHERE clause terms than Y

                          ** changes "x IN (?)" into "x=?". */
      }
    }else if( eOp & (WO_EQ|WO_IS) ){
      int iCol = pProbe->aiColumn[saved_nEq];
      pNew->wsFlags |= WHERE_COLUMN_EQ;
      assert( saved_nEq==pNew->u.btree.nEq );
      if( iCol==XN_ROWID 
       || (iCol>0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1)
       || (iCol>=0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1)
      ){
        if( iCol>=0 && pProbe->uniqNotNull==0 ){
          pNew->wsFlags |= WHERE_UNQ_WANTED;
        }else{
          pNew->wsFlags |= WHERE_ONEROW;
        }
      }

        pNew->prereq = mPrereq | pTerm->prereqRight;
        rc = whereLoopInsert(pBuilder, pNew);
      }
    }
  }
#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */

  /* Loop over all indices
  */
  for(; rc==SQLITE_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){
  /* Loop over all indices. If there was an INDEXED BY clause, then only 
  ** consider index pProbe.  */
  for(; rc==SQLITE_OK && pProbe; 
      pProbe=(pSrc->pIBIndex ? 0 : pProbe->pNext), iSortIdx++
  ){
    if( pProbe->pPartIdxWhere!=0
     && !whereUsablePartialIndex(pSrc->iCursor, pWC, pProbe->pPartIdxWhere) ){
      testcase( pNew->iTab!=pSrc->iCursor );  /* See ticket [98d973b8f5] */
      continue;  /* Partial index inappropriate for this query */
    }
    if( pProbe->bNoQuery ) continue;
    rSize = pProbe->aiRowLogEst[0];
    pNew->u.btree.nEq = 0;
    pNew->u.btree.nBtm = 0;
    pNew->u.btree.nTop = 0;
    pNew->nSkip = 0;
    pNew->nLTerm = 0;
    pNew->iSortIdx = 0;

      pTab->tabFlags |= TF_StatsUsed;
    }
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
    sqlite3Stat4ProbeFree(pBuilder->pRec);
    pBuilder->nRecValid = 0;
    pBuilder->pRec = 0;
#endif

    /* If there was an INDEXED BY clause, then only that one index is
    ** considered. */
    if( pSrc->pIBIndex ) break;
  }
  return rc;
}

#ifndef SQLITE_OMIT_VIRTUALTABLE

/*

  WHERETRACE(0xffff, ("  bIn=%d prereqIn=%04llx prereqOut=%04llx\n",
                      *pbIn, (sqlite3_uint64)mPrereq,
                      (sqlite3_uint64)(pNew->prereq & ~mPrereq)));

  return rc;
}

/*
** If this function is invoked from within an xBestIndex() callback, it
** returns a pointer to a buffer containing the name of the collation
** sequence associated with element iCons of the sqlite3_index_info.aConstraint
** array. Or, if iCons is out of range or there is no active xBestIndex
** call, return NULL.
*/
SQLITE_API const char *sqlite3_vtab_collation(sqlite3_index_info *pIdxInfo, int iCons){
  HiddenIndexInfo *pHidden = (HiddenIndexInfo*)&pIdxInfo[1];
  const char *zRet = 0;
  if( iCons>=0 && iCons<pIdxInfo->nConstraint ){
    CollSeq *pC = 0;
    int iTerm = pIdxInfo->aConstraint[iCons].iTermOffset;
    Expr *pX = pHidden->pWC->a[iTerm].pExpr;
    if( pX->pLeft ){
      pC = sqlite3BinaryCompareCollSeq(pHidden->pParse, pX->pLeft, pX->pRight);
    }
    zRet = (pC ? pC->zName : "BINARY");
  }
  return zRet;
}

/*
** 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 mPrereq and
** mUnusable are set to 0. Otherwise, mPrereq is a mask of all FROM clause

    }
    sqlite3DebugPrintf("\n");
    for(ii=0; ii<pWInfo->nLevel; ii++){
      whereLoopPrint(pWInfo->a[ii].pWLoop, sWLB.pWC);
    }
  }
#endif

  /* Attempt to omit tables from the join that do not effect the result */
  /* Attempt to omit tables from the join that do not affect the result.
  ** For a table to not affect the result, the following must be true:
  **
  **   1) The query must not be an aggregate.
  **   2) The table must be the RHS of a LEFT JOIN.
  **   3) Either the query must be DISTINCT, or else the ON or USING clause
  **      must contain a constraint that limits the scan of the table to 
  **      at most a single row.
  **   4) The table must not be referenced by any part of the query apart
  **      from its own USING or ON clause.
  **
  ** For example, given:
  **
  **     CREATE TABLE t1(ipk INTEGER PRIMARY KEY, v1);
  **     CREATE TABLE t2(ipk INTEGER PRIMARY KEY, v2);
  **     CREATE TABLE t3(ipk INTEGER PRIMARY KEY, v3);
  **
  ** then table t2 can be omitted from the following:
  **
  **     SELECT v1, v3 FROM t1 
  **       LEFT JOIN t2 USING (t1.ipk=t2.ipk)
  **       LEFT JOIN t3 USING (t1.ipk=t3.ipk)
  **
  ** or from:
  **
  **     SELECT DISTINCT v1, v3 FROM t1 
  **       LEFT JOIN t2
  **       LEFT JOIN t3 USING (t1.ipk=t3.ipk)
  */
  notReady = ~(Bitmask)0;
  if( pWInfo->nLevel>=2
   && pResultSet!=0
   && pResultSet!=0               /* guarantees condition (1) above */
   && OptimizationEnabled(db, SQLITE_OmitNoopJoin)
  ){
    int i;
    Bitmask tabUsed = sqlite3WhereExprListUsage(pMaskSet, pResultSet);
    if( sWLB.pOrderBy ){
      tabUsed |= sqlite3WhereExprListUsage(pMaskSet, sWLB.pOrderBy);
    }
    while( pWInfo->nLevel>=2 ){
    for(i=pWInfo->nLevel-1; i>=1; i--){
      WhereTerm *pTerm, *pEnd;
      struct SrcList_item *pItem;
      pLoop = pWInfo->a[pWInfo->nLevel-1].pWLoop;
      if( (pWInfo->pTabList->a[pLoop->iTab].fg.jointype & JT_LEFT)==0 ) break;
      pLoop = pWInfo->a[i].pWLoop;
      pItem = &pWInfo->pTabList->a[pLoop->iTab];
      if( (pItem->fg.jointype & JT_LEFT)==0 ) continue;
      if( (wctrlFlags & WHERE_WANT_DISTINCT)==0
       && (pLoop->wsFlags & WHERE_ONEROW)==0
      ){
        break;
        continue;
      }
      if( (tabUsed & pLoop->maskSelf)!=0 ) break;
      if( (tabUsed & pLoop->maskSelf)!=0 ) continue;
      pEnd = sWLB.pWC->a + sWLB.pWC->nTerm;
      for(pTerm=sWLB.pWC->a; pTerm<pEnd; pTerm++){
        if( (pTerm->prereqAll & pLoop->maskSelf)!=0
         && !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
        ){
          break;
        }
      }
      if( pTerm<pEnd ) break;
        if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
          if( !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
           || pTerm->pExpr->iRightJoinTable!=pItem->iCursor
          ){
            break;
          }
        }
      }
      if( pTerm<pEnd ) continue;
      WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
      notReady &= ~pLoop->maskSelf;
      for(pTerm=sWLB.pWC->a; pTerm<pEnd; pTerm++){
        if( (pTerm->prereqAll & pLoop->maskSelf)!=0 ){
          pTerm->wtFlags |= TERM_CODED;
        }
      }
      if( i!=pWInfo->nLevel-1 ){
        int nByte = (pWInfo->nLevel-1-i) * sizeof(WhereLevel);
        memmove(&pWInfo->a[i], &pWInfo->a[i+1], nByte);
      }
      pWInfo->nLevel--;
      nTabList--;
    }
  }
  WHERETRACE(0xffff,("*** Optimizer Finished ***\n"));
  pWInfo->pParse->nQueryLoop += pWInfo->nRowOut;

  /* If the caller is an UPDATE or DELETE statement that is requesting
  ** to use a one-pass algorithm, determine if this is appropriate.
  **
  ** A one-pass approach can be used if the caller has requested one
  ** and either (a) the scan visits at most one row or (b) each
  ** of the following are true:
  **
  **   * the caller has indicated that a one-pass approach can be used
  **     with multiple rows (by setting WHERE_ONEPASS_MULTIROW), and
  **   * the table is not a virtual table, and
  **   * either the scan does not use the OR optimization or the caller
  **     is a DELETE operation (WHERE_DUPLICATES_OK is only specified
  **     for DELETE).
  **
  ** The last qualification is because an UPDATE statement uses
  ** WhereInfo.aiCurOnePass[1] to determine whether or not it really can
  ** use a one-pass approach, and this is not set accurately for scans
  ** that use the OR optimization.
  */
  assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 ){
    int wsFlags = pWInfo->a[0].pWLoop->wsFlags;
    int bOnerow = (wsFlags & WHERE_ONEROW)!=0;
    if( bOnerow
     || ((wctrlFlags & WHERE_ONEPASS_MULTIROW)!=0
           && 0==(wsFlags & WHERE_VIRTUALTABLE))
    ){
    if( bOnerow || (
        0!=(wctrlFlags & WHERE_ONEPASS_MULTIROW)
     && 0==(wsFlags & WHERE_VIRTUALTABLE)
     && (0==(wsFlags & WHERE_MULTI_OR) || (wctrlFlags & WHERE_DUPLICATES_OK))
    )){
      pWInfo->eOnePass = bOnerow ? ONEPASS_SINGLE : ONEPASS_MULTI;
      if( HasRowid(pTabList->a[0].pTab) && (wsFlags & WHERE_IDX_ONLY) ){
        if( wctrlFlags & WHERE_ONEPASS_MULTIROW ){
          bFordelete = OPFLAG_FORDELETE;
        }
        pWInfo->a[0].pWLoop->wsFlags = (wsFlags & ~WHERE_IDX_ONLY);
      }