/*

 ** 2001 September 15

 **

 ** The author disclaims copyright to this source code.  In place of

 ** a legal notice, here is a blessing:

 **

 **    May you do good and not evil.

 **    May you find forgiveness for yourself and forgive others.

 **    May you share freely, never taking more than you give.

 **

 *************************************************************************

 ** Internal interface definitions for SQLite.

 **

 ** @(#) $Id$

 */

 #ifndef _SQLITEINT_H_

 #define _SQLITEINT_H_

 #include "sqliteLimit.h"

 #if defined(SQLITE_TCL) || defined(TCLSH)

 # include <tcl.h>

 #endif

 /*

 ** Many people are failing to set -DNDEBUG=1 when compiling SQLite.

 ** Setting NDEBUG makes the code smaller and run faster.  So the following

 ** lines are added to automatically set NDEBUG unless the -DSQLITE_DEBUG=1

 ** option is set.  Thus NDEBUG becomes an opt-in rather than an opt-out

 ** feature.

 */

 #if !defined(NDEBUG) && !defined(SQLITE_DEBUG) 

 # define NDEBUG 1

 #endif

 /*

 ** These #defines should enable >2GB file support on Posix if the

 ** underlying operating system supports it.  If the OS lacks

 ** large file support, or if the OS is windows, these should be no-ops.

 **

 ** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch

 ** on the compiler command line.  This is necessary if you are compiling

 ** on a recent machine (ex: RedHat 7.2) but you want your code to work

 ** on an older machine (ex: RedHat 6.0).  If you compile on RedHat 7.2

 ** without this option, LFS is enable.  But LFS does not exist in the kernel

 ** in RedHat 6.0, so the code won't work.  Hence, for maximum binary

 ** portability you should omit LFS.

 **

 ** Similar is true for MacOS.  LFS is only supported on MacOS 9 and later.

 */

 #ifndef SQLITE_DISABLE_LFS

 # define _LARGE_FILE       1

 # ifndef _FILE_OFFSET_BITS

 #   define _FILE_OFFSET_BITS 64

 # endif

 # define _LARGEFILE_SOURCE 1

 #endif

 #include "sqlite3.h"

 #include "hash.h"

 #include "parse.h"

 #include <stdio.h>

 #include <stdlib.h>

 #include <string.h>

 #include <assert.h>

 #include <stddef.h>

 #define sqlite3_isnan(X)  ((X)!=(X))

 /*

 ** If compiling for a processor that lacks floating point support,

 ** substitute integer for floating-point

 */

 #ifdef SQLITE_OMIT_FLOATING_POINT

 # define double sqlite_int64

 # define LONGDOUBLE_TYPE sqlite_int64

 # ifndef SQLITE_BIG_DBL

 #   define SQLITE_BIG_DBL (0x7fffffffffffffff)

 # endif

 # define SQLITE_OMIT_DATETIME_FUNCS 1

 # define SQLITE_OMIT_TRACE 1

 # undef SQLITE_MIXED_ENDIAN_64BIT_FLOAT

 #endif

 #ifndef SQLITE_BIG_DBL

 # define SQLITE_BIG_DBL (1e99)

 #endif

 /*

 ** OMIT_TEMPDB is set to 1 if SQLITE_OMIT_TEMPDB is defined, or 0

 ** afterward. Having this macro allows us to cause the C compiler 

 ** to omit code used by TEMP tables without messy #ifndef statements.

 */

 #ifdef SQLITE_OMIT_TEMPDB

 #define OMIT_TEMPDB 1

 #else

 #define OMIT_TEMPDB 0

 #endif

 /*

 ** If the following macro is set to 1, then NULL values are considered

 ** distinct when determining whether or not two entries are the same

 ** in a UNIQUE index.  This is the way PostgreSQL, Oracle, DB2, MySQL,

 ** OCELOT, and Firebird all work.  The SQL92 spec explicitly says this

 ** is the way things are suppose to work.

 **

 ** If the following macro is set to 0, the NULLs are indistinct for

 ** a UNIQUE index.  In this mode, you can only have a single NULL entry

 ** for a column declared UNIQUE.  This is the way Informix and SQL Server

 ** work.

 */

 #define NULL_DISTINCT_FOR_UNIQUE 1

 /*

 ** The "file format" number is an integer that is incremented whenever

 ** the VDBE-level file format changes.  The following macros define the

 ** the default file format for new databases and the maximum file format

 ** that the library can read.

 */

 #define SQLITE_MAX_FILE_FORMAT 4

 #ifndef SQLITE_DEFAULT_FILE_FORMAT

 # define SQLITE_DEFAULT_FILE_FORMAT 1

 #endif

 /*

 ** Provide a default value for TEMP_STORE in case it is not specified

 ** on the command-line

 */

 #ifndef TEMP_STORE

 # define TEMP_STORE 1

 #endif

 /*

 ** GCC does not define the offsetof() macro so we'll have to do it

 ** ourselves.

 */

 #ifndef offsetof

 #define offsetof(STRUCTURE,FIELD) ((int)((char*)&((STRUCTURE*)0)->FIELD))

 #endif

 /*

 ** Check to see if this machine uses EBCDIC.  (Yes, believe it or

 ** not, there are still machines out there that use EBCDIC.)

 */

 #if 'A' == '\301'

 # define SQLITE_EBCDIC 1

 #else

 # define SQLITE_ASCII 1

 #endif

 /*

 ** Integers of known sizes.  These typedefs might change for architectures

 ** where the sizes very.  Preprocessor macros are available so that the

 ** types can be conveniently redefined at compile-type.  Like this:

 **

 **         cc '-DUINTPTR_TYPE=long long int' ...

 */

 #ifndef UINT32_TYPE

 # define UINT32_TYPE unsigned int

 #endif

 #ifndef UINT16_TYPE

 # define UINT16_TYPE unsigned short int

 #endif

 #ifndef INT16_TYPE

 # define INT16_TYPE short int

 #endif

 #ifndef UINT8_TYPE

 # define UINT8_TYPE unsigned char

 #endif

 #ifndef INT8_TYPE

 # define INT8_TYPE signed char

 #endif

 #ifndef LONGDOUBLE_TYPE

 # define LONGDOUBLE_TYPE long double

 #endif

 typedef sqlite_int64 i64;          /* 8-byte signed integer */

 typedef sqlite_uint64 u64;         /* 8-byte unsigned integer */

 typedef UINT32_TYPE u32;           /* 4-byte unsigned integer */

 typedef UINT16_TYPE u16;           /* 2-byte unsigned integer */

 typedef INT16_TYPE i16;            /* 2-byte signed integer */

 typedef UINT8_TYPE u8;             /* 1-byte unsigned integer */

 typedef UINT8_TYPE i8;             /* 1-byte signed integer */

 /*

 ** Macros to determine whether the machine is big or little endian,

 ** evaluated at runtime.

 */

 extern const int sqlite3one;

 #if defined(i386) || defined(__i386__) || defined(_M_IX86)

 # define SQLITE_BIGENDIAN    0

 # define SQLITE_LITTLEENDIAN 1

 # define SQLITE_UTF16NATIVE  SQLITE_UTF16LE

 #else

 # define SQLITE_BIGENDIAN    (*(char *)(&sqlite3one)==0)

 # define SQLITE_LITTLEENDIAN (*(char *)(&sqlite3one)==1)

 # define SQLITE_UTF16NATIVE (SQLITE_BIGENDIAN?SQLITE_UTF16BE:SQLITE_UTF16LE)

 #endif

 /*

 ** An instance of the following structure is used to store the busy-handler

 ** callback for a given sqlite handle. 

 **

 ** The sqlite.busyHandler member of the sqlite struct contains the busy

 ** callback for the database handle. Each pager opened via the sqlite

 ** handle is passed a pointer to sqlite.busyHandler. The busy-handler

 ** callback is currently invoked only from within pager.c.

 */

 typedef struct BusyHandler BusyHandler;

 struct BusyHandler {

   int (*xFunc)(void *,int);  /* The busy callback */

   void *pArg;                /* First arg to busy callback */

   int nBusy;                 /* Incremented with each busy call */

 };

 /*

 ** Defer sourcing vdbe.h and btree.h until after the "u8" and 

 ** "BusyHandler typedefs.

 */

 #include "vdbe.h"

 #include "btree.h"

 #include "pager.h"

 #ifdef SQLITE_MEMDEBUG

 /*

 ** The following global variables are used for testing and debugging

 ** only.  They only work if SQLITE_MEMDEBUG is defined.

 */

 extern int sqlite3_nMalloc;      /* Number of sqliteMalloc() calls */

 extern int sqlite3_nFree;        /* Number of sqliteFree() calls */

 extern int sqlite3_iMallocFail;  /* Fail sqliteMalloc() after this many calls */

 extern int sqlite3_iMallocReset; /* Set iMallocFail to this when it reaches 0 */

 extern void *sqlite3_pFirst;         /* Pointer to linked list of allocations */

 extern int sqlite3_nMaxAlloc;        /* High water mark of ThreadData.nAlloc */

 extern int sqlite3_mallocDisallowed; /* assert() in sqlite3Malloc() if set */

 extern int sqlite3_isFail;           /* True if all malloc calls should fail */

 extern const char *sqlite3_zFile;    /* Filename to associate debug info with */

 extern int sqlite3_iLine;            /* Line number for debug info */

 #define ENTER_MALLOC (sqlite3_zFile = __FILE__, sqlite3_iLine = __LINE__)

 #define sqliteMalloc(x)          (ENTER_MALLOC, sqlite3Malloc(x,1))

 #define sqliteMallocRaw(x)       (ENTER_MALLOC, sqlite3MallocRaw(x,1))

 #define sqliteRealloc(x,y)       (ENTER_MALLOC, sqlite3Realloc(x,y))

 #define sqliteStrDup(x)          (ENTER_MALLOC, sqlite3StrDup(x))

 #define sqliteStrNDup(x,y)       (ENTER_MALLOC, sqlite3StrNDup(x,y))

 #define sqliteReallocOrFree(x,y) (ENTER_MALLOC, sqlite3ReallocOrFree(x,y))

 #else

 #define ENTER_MALLOC 0

 #define sqliteMalloc(x)          sqlite3Malloc(x,1)

 #define sqliteMallocRaw(x)       sqlite3MallocRaw(x,1)

 #define sqliteRealloc(x,y)       sqlite3Realloc(x,y)

 #define sqliteStrDup(x)          sqlite3StrDup(x)

 #define sqliteStrNDup(x,y)       sqlite3StrNDup(x,y)

 #define sqliteReallocOrFree(x,y) sqlite3ReallocOrFree(x,y)

 #endif

 /* Variable sqlite3_mallocHasFailed is set to true after a malloc() 

 ** failure occurs. 

 **

 ** The sqlite3MallocFailed() macro returns true if a malloc has failed

 ** in this thread since the last call to sqlite3ApiExit(), or false 

 ** otherwise.

 */

 extern int sqlite3_mallocHasFailed;

 #define sqlite3MallocFailed() (sqlite3_mallocHasFailed && sqlite3OsInMutex(1))

 #define sqliteFree(x)          sqlite3FreeX(x)

 #define sqliteAllocSize(x)     sqlite3AllocSize(x)

 /*

 ** An instance of this structure might be allocated to store information

 ** specific to a single thread.

 */

 struct ThreadData {

   int dummy;               /* So that this structure is never empty */

 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT

   int nSoftHeapLimit;      /* Suggested max mem allocation.  No limit if <0 */

   int nAlloc;              /* Number of bytes currently allocated */

   Pager *pPager;           /* Linked list of all pagers in this thread */

 #endif

 #ifndef SQLITE_OMIT_SHARED_CACHE

   u8 useSharedData;        /* True if shared pagers and schemas are enabled */

   BtShared *pBtree;        /* Linked list of all currently open BTrees */

 #endif

 };

 /*

 ** Name of the master database table.  The master database table

 ** is a special table that holds the names and attributes of all

 ** user tables and indices.

 */

 #define MASTER_NAME       "sqlite_master"

 #define TEMP_MASTER_NAME  "sqlite_temp_master"

 /*

 ** The root-page of the master database table.

 */

 #define MASTER_ROOT       1

 /*

 ** The name of the schema table.

 */

 #define SCHEMA_TABLE(x)  ((!OMIT_TEMPDB)&&(x==1)?TEMP_MASTER_NAME:MASTER_NAME)

 /*

 ** A convenience macro that returns the number of elements in

 ** an array.

 */

 #define ArraySize(X)    (sizeof(X)/sizeof(X[0]))

 /*

 ** Forward references to structures

 */

 typedef struct AggInfo AggInfo;

 typedef struct AuthContext AuthContext;

 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 FKey FKey;

 typedef struct FuncDef FuncDef;

 typedef struct IdList IdList;

 typedef struct Index Index;

 typedef struct KeyClass KeyClass;

 typedef struct KeyInfo KeyInfo;

 typedef struct Module Module;

 typedef struct NameContext NameContext;

 typedef struct Parse Parse;

 typedef struct Select Select;

 typedef struct SrcList SrcList;

 typedef struct ThreadData ThreadData;

 typedef struct Table Table;

 typedef struct TableLock TableLock;

 typedef struct Token Token;

 typedef struct TriggerStack TriggerStack;

 typedef struct TriggerStep TriggerStep;

 typedef struct Trigger Trigger;

 typedef struct WhereInfo WhereInfo;

 typedef struct WhereLevel WhereLevel;

 #include "os.h"

 /*

 ** Each database file to be accessed by the system is an instance

 ** of the following structure.  There are normally two of these structures

 ** in the sqlite.aDb[] array.  aDb[0] is the main database file and

 ** aDb[1] is the database file used to hold temporary tables.  Additional

 ** databases may be attached.

 */

 struct Db {

   char *zName;         /* Name of this database */

   Btree *pBt;          /* The B*Tree structure for this database file */

   u8 inTrans;          /* 0: not writable.  1: Transaction.  2: Checkpoint */

   u8 safety_level;     /* How aggressive at synching data to disk */

   void *pAux;               /* Auxiliary data.  Usually NULL */

   void (*xFreeAux)(void*);  /* Routine to free pAux */

   Schema *pSchema;     /* Pointer to database schema (possibly shared) */

 };

 /*

 ** An instance of the following structure stores a database schema.

 **

 ** If there are no virtual tables configured in this schema, the

 ** Schema.db variable is set to NULL. After the first virtual table

 ** has been added, it is set to point to the database connection 

 ** used to create the connection. Once a virtual table has been

 ** added to the Schema structure and the Schema.db variable populated, 

 ** only that database connection may use the Schema to prepare 

 ** statements.

 */

 struct Schema {

   int schema_cookie;   /* Database schema version number for this file */

   Hash tblHash;        /* All tables indexed by name */

   Hash idxHash;        /* All (named) indices indexed by name */

   Hash trigHash;       /* All triggers indexed by name */

   Hash aFKey;          /* Foreign keys indexed by to-table */

   Table *pSeqTab;      /* The sqlite_sequence table used by AUTOINCREMENT */

   u8 file_format;      /* Schema format version for this file */

   u8 enc;              /* Text encoding used by this database */

   u16 flags;           /* Flags associated with this schema */

   int cache_size;      /* Number of pages to use in the cache */

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   sqlite3 *db;         /* "Owner" connection. See comment above */

 #endif

 };

 /*

 ** These macros can be used to test, set, or clear bits in the 

 ** Db.flags field.

 */

 #define DbHasProperty(D,I,P)     (((D)->aDb[I].pSchema->flags&(P))==(P))

 #define DbHasAnyProperty(D,I,P)  (((D)->aDb[I].pSchema->flags&(P))!=0)

 #define DbSetProperty(D,I,P)     (D)->aDb[I].pSchema->flags|=(P)

 #define DbClearProperty(D,I,P)   (D)->aDb[I].pSchema->flags&=~(P)

 /*

 ** Allowed values for the DB.flags field.

 **

 ** The DB_SchemaLoaded flag is set after the database schema has been

 ** read into internal hash tables.

 **

 ** DB_UnresetViews means that one or more views have column names that

 ** have been filled out.  If the schema changes, these column names might

 ** changes and so the view will need to be reset.

 */

 #define DB_SchemaLoaded    0x0001  /* The schema has been loaded */

 #define DB_UnresetViews    0x0002  /* Some views have defined column names */

 #define DB_Empty           0x0004  /* The file is empty (length 0 bytes) */

 /*

 ** Each database is an instance of the following structure.

 **

 ** The sqlite.lastRowid records the last insert rowid generated by an

 ** insert statement.  Inserts on views do not affect its value.  Each

 ** trigger has its own context, so that lastRowid can be updated inside

 ** triggers as usual.  The previous value will be restored once the trigger

 ** exits.  Upon entering a before or instead of trigger, lastRowid is no

 ** longer (since after version 2.8.12) reset to -1.

 **

 ** The sqlite.nChange does not count changes within triggers and keeps no

 ** context.  It is reset at start of sqlite3_exec.

 ** The sqlite.lsChange represents the number of changes made by the last

 ** insert, update, or delete statement.  It remains constant throughout the

 ** length of a statement and is then updated by OP_SetCounts.  It keeps a

 ** context stack just like lastRowid so that the count of changes

 ** within a trigger is not seen outside the trigger.  Changes to views do not

 ** affect the value of lsChange.

 ** The sqlite.csChange keeps track of the number of current changes (since

 ** the last statement) and is used to update sqlite_lsChange.

 **

 ** The member variables sqlite.errCode, sqlite.zErrMsg and sqlite.zErrMsg16

 ** store the most recent error code and, if applicable, string. The

 ** internal function sqlite3Error() is used to set these variables

 ** consistently.

 */

 struct sqlite3 {

   int nDb;                      /* Number of backends currently in use */

   Db *aDb;                      /* All backends */

   int flags;                    /* Miscellanous flags. See below */

   int errCode;                  /* Most recent error code (SQLITE_*) */

   int errMask;                  /* & result codes with this before returning */

   u8 autoCommit;                /* The auto-commit flag. */

   u8 temp_store;                /* 1: file 2: memory 0: default */

   int nTable;                   /* Number of tables in the database */

   CollSeq *pDfltColl;           /* The default collating sequence (BINARY) */

   i64 lastRowid;                /* ROWID of most recent insert (see above) */

   i64 priorNewRowid;            /* Last randomly generated ROWID */

   int magic;                    /* Magic number for detect library misuse */

   int nChange;                  /* Value returned by sqlite3_changes() */

   int nTotalChange;             /* Value returned by sqlite3_total_changes() */

   struct sqlite3InitInfo {      /* Information used during initialization */

     int iDb;                    /* When back is being initialized */

     int newTnum;                /* Rootpage of table being initialized */

     u8 busy;                    /* TRUE if currently initializing */

   } init;

   int nExtension;               /* Number of loaded extensions */

   void **aExtension;            /* Array of shared libraray handles */

   struct Vdbe *pVdbe;           /* List of active virtual machines */

   int activeVdbeCnt;            /* Number of vdbes currently executing */

   void (*xTrace)(void*,const char*);        /* Trace function */

   void *pTraceArg;                          /* Argument to the trace function */

   void (*xProfile)(void*,const char*,u64);  /* Profiling function */

   void *pProfileArg;                        /* Argument to profile function */

   void *pCommitArg;                 /* Argument to xCommitCallback() */   

   int (*xCommitCallback)(void*);    /* Invoked at every commit. */

   void *pRollbackArg;               /* Argument to xRollbackCallback() */   

   void (*xRollbackCallback)(void*); /* Invoked at every commit. */

   void *pUpdateArg;

   void (*xUpdateCallback)(void*,int, const char*,const char*,sqlite_int64);

   void(*xCollNeeded)(void*,sqlite3*,int eTextRep,const char*);

   void(*xCollNeeded16)(void*,sqlite3*,int eTextRep,const void*);

   void *pCollNeededArg;

   sqlite3_value *pErr;          /* Most recent error message */

   char *zErrMsg;                /* Most recent error message (UTF-8 encoded) */

   char *zErrMsg16;              /* Most recent error message (UTF-16 encoded) */

   union {

     int isInterrupted;          /* True if sqlite3_interrupt has been called */

     double notUsed1;            /* Spacer */

   } u1;

 #ifndef SQLITE_OMIT_AUTHORIZATION

   int (*xAuth)(void*,int,const char*,const char*,const char*,const char*);

                                 /* Access authorization function */

   void *pAuthArg;               /* 1st argument to the access auth function */

 #endif

 #ifndef SQLITE_OMIT_PROGRESS_CALLBACK

   int (*xProgress)(void *);     /* The progress callback */

   void *pProgressArg;           /* Argument to the progress callback */

   int nProgressOps;             /* Number of opcodes for progress callback */

 #endif

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   Hash aModule;                 /* populated by sqlite3_create_module() */

   Table *pVTab;                 /* vtab with active Connect/Create method */

   sqlite3_vtab **aVTrans;       /* Virtual tables with open transactions */

   int nVTrans;                  /* Allocated size of aVTrans */

 #endif

   Hash aFunc;                   /* All functions that can be in SQL exprs */

   Hash aCollSeq;                /* All collating sequences */

   BusyHandler busyHandler;      /* Busy callback */

   int busyTimeout;              /* Busy handler timeout, in msec */

   Db aDbStatic[2];              /* Static space for the 2 default backends */

 #ifdef SQLITE_SSE

   sqlite3_stmt *pFetch;         /* Used by SSE to fetch stored statements */

 #endif

   u8 dfltLockMode;              /* Default locking-mode for attached dbs */

 };

 /*

 ** A macro to discover the encoding of a database.

 */

 #define ENC(db) ((db)->aDb[0].pSchema->enc)

 /*

 ** Possible values for the sqlite.flags and or Db.flags fields.

 **

 ** On sqlite.flags, the SQLITE_InTrans value means that we have

 ** executed a BEGIN.  On Db.flags, SQLITE_InTrans means a statement

 ** transaction is active on that particular database file.

 */

 #define SQLITE_VdbeTrace      0x00000001  /* True to trace VDBE execution */

 #define SQLITE_InTrans        0x00000008  /* True if in a transaction */

 #define SQLITE_InternChanges  0x00000010  /* Uncommitted Hash table changes */

 #define SQLITE_FullColNames   0x00000020  /* Show full column names on SELECT */

 #define SQLITE_ShortColNames  0x00000040  /* Show short columns names */

 #define SQLITE_CountRows      0x00000080  /* Count rows changed by INSERT, */

                                           /*   DELETE, or UPDATE and return */

                                           /*   the count using a callback. */

 #define SQLITE_NullCallback   0x00000100  /* Invoke the callback once if the */

                                           /*   result set is empty */

 #define SQLITE_SqlTrace       0x00000200  /* Debug print SQL as it executes */

 #define SQLITE_VdbeListing    0x00000400  /* Debug listings of VDBE programs */

 #define SQLITE_WriteSchema    0x00000800  /* OK to update SQLITE_MASTER */

 #define SQLITE_NoReadlock     0x00001000  /* Readlocks are omitted when 

                                           ** accessing read-only databases */

 #define SQLITE_IgnoreChecks   0x00002000  /* Do not enforce check constraints */

 #define SQLITE_ReadUncommitted 0x00004000 /* For shared-cache mode */

 #define SQLITE_LegacyFileFmt  0x00008000  /* Create new databases in format 1 */

 #define SQLITE_FullFSync      0x00010000  /* Use full fsync on the backend */

 #define SQLITE_LoadExtension  0x00020000  /* Enable load_extension */

 #define SQLITE_RecoveryMode   0x00040000  /* Ignore schema errors */

 /*

 ** Possible values for the sqlite.magic field.

 ** The numbers are obtained at random and have no special meaning, other

 ** than being distinct from one another.

 */

 #define SQLITE_MAGIC_OPEN     0xa029a697  /* Database is open */

 #define SQLITE_MAGIC_CLOSED   0x9f3c2d33  /* Database is closed */

 #define SQLITE_MAGIC_BUSY     0xf03b7906  /* Database currently in use */

 #define SQLITE_MAGIC_ERROR    0xb5357930  /* An SQLITE_MISUSE error occurred */

 /*

 ** Each SQL function is defined by an instance of the following

 ** structure.  A pointer to this structure is stored in the sqlite.aFunc

 ** hash table.  When multiple functions have the same name, the hash table

 ** points to a linked list of these structures.

 */

 struct FuncDef {

   i16 nArg;            /* Number of arguments.  -1 means unlimited */

   u8 iPrefEnc;         /* Preferred text encoding (SQLITE_UTF8, 16LE, 16BE) */

   u8 needCollSeq;      /* True if sqlite3GetFuncCollSeq() might be called */

   u8 flags;            /* Some combination of SQLITE_FUNC_* */

   void *pUserData;     /* User data parameter */

   FuncDef *pNext;      /* Next function with same name */

   void (*xFunc)(sqlite3_context*,int,sqlite3_value**); /* Regular function */

   void (*xStep)(sqlite3_context*,int,sqlite3_value**); /* Aggregate step */

   void (*xFinalize)(sqlite3_context*);                /* Aggregate finializer */

   char zName[1];       /* SQL name of the function.  MUST BE LAST */

 };

 /*

 ** Each SQLite module (virtual table definition) is defined by an

 ** instance of the following structure, stored in the sqlite3.aModule

 ** hash table.

 */

 struct Module {

   const sqlite3_module *pModule;       /* Callback pointers */

   const char *zName;                   /* Name passed to create_module() */

   void *pAux;                          /* pAux passed to create_module() */

   void (*xDestroy)(void *);            /* Module destructor function */

 };

 /*

 ** Possible values for FuncDef.flags

 */

 #define SQLITE_FUNC_LIKE   0x01  /* Candidate for the LIKE optimization */

 #define SQLITE_FUNC_CASE   0x02  /* Case-sensitive LIKE-type function */

 #define SQLITE_FUNC_EPHEM  0x04  /* Ephermeral.  Delete with VDBE */

 /*

 ** information about each column of an SQL table is held in an instance

 ** of this structure.

 */

 struct Column {

   char *zName;     /* Name of this column */

   Expr *pDflt;     /* Default value of this column */

   char *zType;     /* Data type for this column */

   char *zColl;     /* Collating sequence.  If NULL, use the default */

   u8 notNull;      /* True if there is a NOT NULL constraint */

   u8 isPrimKey;    /* True if this column is part of the PRIMARY KEY */

   char affinity;   /* One of the SQLITE_AFF_... values */

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   u8 isHidden;     /* True if this column is 'hidden' */

 #endif

 };

 /*

 ** A "Collating Sequence" is defined by an instance of the following

 ** structure. Conceptually, a collating sequence consists of a name and

 ** a comparison routine that defines the order of that sequence.

 **

 ** There may two seperate implementations of the collation function, one

 ** that processes text in UTF-8 encoding (CollSeq.xCmp) and another that

 ** processes text encoded in UTF-16 (CollSeq.xCmp16), using the machine

 ** native byte order. When a collation sequence is invoked, SQLite selects

 ** the version that will require the least expensive encoding

 ** translations, if any.

 **

 ** The CollSeq.pUser member variable is an extra parameter that passed in

 ** as the first argument to the UTF-8 comparison function, xCmp.

 ** CollSeq.pUser16 is the equivalent for the UTF-16 comparison function,

 ** xCmp16.

 **

 ** If both CollSeq.xCmp and CollSeq.xCmp16 are NULL, it means that the

 ** collating sequence is undefined.  Indices built on an undefined

 ** collating sequence may not be read or written.

 */

 struct CollSeq {

   char *zName;          /* Name of the collating sequence, UTF-8 encoded */

   u8 enc;               /* Text encoding handled by xCmp() */

   u8 type;              /* One of the SQLITE_COLL_... values below */

   void *pUser;          /* First argument to xCmp() */

   int (*xCmp)(void*,int, const void*, int, const void*);

   void (*xDel)(void*);  /* Destructor for pUser */

 };

 /*

 ** Allowed values of CollSeq flags:

 */

 #define SQLITE_COLL_BINARY  1  /* The default memcmp() collating sequence */

 #define SQLITE_COLL_NOCASE  2  /* The built-in NOCASE collating sequence */

 #define SQLITE_COLL_REVERSE 3  /* The built-in REVERSE collating sequence */

 #define SQLITE_COLL_USER    0  /* Any other user-defined collating sequence */

 /*

 ** A sort order can be either ASC or DESC.

 */

 #define SQLITE_SO_ASC       0  /* Sort in ascending order */

 #define SQLITE_SO_DESC      1  /* Sort in ascending order */

 /*

 ** Column affinity types.

 **

 ** These used to have mnemonic name like 'i' for SQLITE_AFF_INTEGER and

 ** 't' for SQLITE_AFF_TEXT.  But we can save a little space and improve

 ** the speed a little by number the values consecutively.  

 **

 ** But rather than start with 0 or 1, we begin with 'a'.  That way,

 ** when multiple affinity types are concatenated into a string and

 ** used as the P3 operand, they will be more readable.

 **

 ** Note also that the numeric types are grouped together so that testing

 ** for a numeric type is a single comparison.

 */

 #define SQLITE_AFF_TEXT     'a'

 #define SQLITE_AFF_NONE     'b'

 #define SQLITE_AFF_NUMERIC  'c'

 #define SQLITE_AFF_INTEGER  'd'

 #define SQLITE_AFF_REAL     'e'

 #define sqlite3IsNumericAffinity(X)  ((X)>=SQLITE_AFF_NUMERIC)

 /*

 ** Each SQL table is represented in memory by an instance of the

 ** following structure.

 **

 ** Table.zName is the name of the table.  The case of the original

 ** CREATE TABLE statement is stored, but case is not significant for

 ** comparisons.

 **

 ** Table.nCol is the number of columns in this table.  Table.aCol is a

 ** pointer to an array of Column structures, one for each column.

 **

 ** If the table has an INTEGER PRIMARY KEY, then Table.iPKey is the index of

 ** the column that is that key.   Otherwise Table.iPKey is negative.  Note

 ** that the datatype of the PRIMARY KEY must be INTEGER for this field to

 ** be set.  An INTEGER PRIMARY KEY is used as the rowid for each row of

 ** the table.  If a table has no INTEGER PRIMARY KEY, then a random rowid

 ** is generated for each row of the table.  Table.hasPrimKey is true if

 ** the table has any PRIMARY KEY, INTEGER or otherwise.

 **

 ** Table.tnum is the page number for the root BTree page of the table in the

 ** database file.  If Table.iDb is the index of the database table backend

 ** in sqlite.aDb[].  0 is for the main database and 1 is for the file that

 ** holds temporary tables and indices.  If Table.isEphem

 ** is true, then the table is stored in a file that is automatically deleted

 ** when the VDBE cursor to the table is closed.  In this case Table.tnum 

 ** refers VDBE cursor number that holds the table open, not to the root

 ** page number.  Transient tables are used to hold the results of a

 ** sub-query that appears instead of a real table name in the FROM clause 

 ** of a SELECT statement.

 */

 struct Table {

   char *zName;     /* Name of the table */

   int nCol;        /* Number of columns in this table */

   Column *aCol;    /* Information about each column */

   int iPKey;       /* If not less then 0, use aCol[iPKey] as the primary key */

   Index *pIndex;   /* List of SQL indexes on this table. */

   int tnum;        /* Root BTree node for this table (see note above) */

   Select *pSelect; /* NULL for tables.  Points to definition if a view. */

   int nRef;          /* Number of pointers to this Table */

   Trigger *pTrigger; /* List of SQL triggers on this table */

   FKey *pFKey;       /* Linked list of all foreign keys in this table */

   char *zColAff;     /* String defining the affinity of each column */

 #ifndef SQLITE_OMIT_CHECK

   Expr *pCheck;      /* The AND of all CHECK constraints */

 #endif

 #ifndef SQLITE_OMIT_ALTERTABLE

   int addColOffset;  /* Offset in CREATE TABLE statement to add a new column */

 #endif

   u8 readOnly;     /* True if this table should not be written by the user */

   u8 isEphem;      /* True if created using OP_OpenEphermeral */

   u8 hasPrimKey;   /* True if there exists a primary key */

   u8 keyConf;      /* What to do in case of uniqueness conflict on iPKey */

   u8 autoInc;      /* True if the integer primary key is autoincrement */

 #ifndef SQLITE_OMIT_VIRTUALTABLE

   u8 isVirtual;             /* True if this is a virtual table */

   u8 isCommit;              /* True once the CREATE TABLE has been committed */

   Module *pMod;             /* Pointer to the implementation of the module */

   sqlite3_vtab *pVtab;      /* Pointer to the module instance */

   int nModuleArg;           /* Number of arguments to the module */

   char **azModuleArg;       /* Text of all module args. [0] is module name */

 #endif

   Schema *pSchema;

 };

 /*

 ** Test to see whether or not a table is a virtual table.  This is

 ** done as a macro so that it will be optimized out when virtual

 ** table support is omitted from the build.

 */

 #ifndef SQLITE_OMIT_VIRTUALTABLE

 #  define IsVirtual(X)      ((X)->isVirtual)

 #  define IsHiddenColumn(X) ((X)->isHidden)

 #else

 #  define IsVirtual(X)      0

 #  define IsHiddenColumn(X) 0

 #endif

 /*

 ** Each foreign key constraint is an instance of the following structure.

 **

 ** A foreign key is associated with two tables.  The "from" table is

 ** the table that contains the REFERENCES clause that creates the foreign

 ** key.  The "to" table is the table that is named in the REFERENCES clause.

 ** Consider this example:

 **

 **     CREATE TABLE ex1(

 **       a INTEGER PRIMARY KEY,

 **       b INTEGER CONSTRAINT fk1 REFERENCES ex2(x)

 **     );

 **

 ** For foreign key "fk1", the from-table is "ex1" and the to-table is "ex2".

 **

 ** Each REFERENCES clause generates an instance of the following structure

 ** which is attached to the from-table.  The to-table need not exist when

 ** the from-table is created.  The existance of the to-table is not checked

 ** until an attempt is made to insert data into the from-table.

 **

 ** The sqlite.aFKey hash table stores pointers to this structure

 ** given the name of a to-table.  For each to-table, all foreign keys

 ** associated with that table are on a linked list using the FKey.pNextTo

 ** field.

 */

 struct FKey {

   Table *pFrom;     /* The table that constains the REFERENCES clause */

   FKey *pNextFrom;  /* Next foreign key in pFrom */

   char *zTo;        /* Name of table that the key points to */

   FKey *pNextTo;    /* Next foreign key that points to zTo */

   int nCol;         /* Number of columns in this key */

   struct sColMap {  /* Mapping of columns in pFrom to columns in zTo */

     int iFrom;         /* Index of column in pFrom */

     char *zCol;        /* Name of column in zTo.  If 0 use PRIMARY KEY */

   } *aCol;          /* One entry for each of nCol column s */

   u8 isDeferred;    /* True if constraint checking is deferred till COMMIT */

   u8 updateConf;    /* How to resolve conflicts that occur on UPDATE */

   u8 deleteConf;    /* How to resolve conflicts that occur on DELETE */

   u8 insertConf;    /* How to resolve conflicts that occur on INSERT */

 };

 /*

 ** SQLite supports many different ways to resolve a contraint

 ** error.  ROLLBACK processing means that a constraint violation

 ** causes the operation in process to fail and for the current transaction

 ** to be rolled back.  ABORT processing means the operation in process

 ** fails and any prior changes from that one operation are backed out,

 ** but the transaction is not rolled back.  FAIL processing means that

 ** the operation in progress stops and returns an error code.  But prior

 ** changes due to the same operation are not backed out and no rollback

 ** occurs.  IGNORE means that the particular row that caused the constraint

 ** error is not inserted or updated.  Processing continues and no error

 ** is returned.  REPLACE means that preexisting database rows that caused

 ** a UNIQUE constraint violation are removed so that the new insert or

 ** update can proceed.  Processing continues and no error is reported.

 **

 ** RESTRICT, SETNULL, and CASCADE actions apply only to foreign keys.

 ** RESTRICT is the same as ABORT for IMMEDIATE foreign keys and the

 ** same as ROLLBACK for DEFERRED keys.  SETNULL means that the foreign

 ** key is set to NULL.  CASCADE means that a DELETE or UPDATE of the

 ** referenced table row is propagated into the row that holds the

 ** foreign key.

 ** 

 ** The following symbolic values are used to record which type

 ** of action to take.

 */

 #define OE_None     0   /* There is no constraint to check */

 #define OE_Rollback 1   /* Fail the operation and rollback the transaction */

 #define OE_Abort    2   /* Back out changes but do no rollback transaction */

 #define OE_Fail     3   /* Stop the operation but leave all prior changes */

 #define OE_Ignore   4   /* Ignore the error. Do not do the INSERT or UPDATE */

 #define OE_Replace  5   /* Delete existing record, then do INSERT or UPDATE */

 #define OE_Restrict 6   /* OE_Abort for IMMEDIATE, OE_Rollback for DEFERRED */

 #define OE_SetNull  7   /* Set the foreign key value to NULL */

 #define OE_SetDflt  8   /* Set the foreign key value to its default */

 #define OE_Cascade  9   /* Cascade the changes */

 #define OE_Default  99  /* Do whatever the default action is */

 /*

 ** An instance of the following structure is passed as the first

 ** argument to sqlite3VdbeKeyCompare and is used to control the 

 ** comparison of the two index keys.

 **

 ** If the KeyInfo.incrKey value is true and the comparison would

 ** otherwise be equal, then return a result as if the second key

 ** were larger.

 */

 struct KeyInfo {

   u8 enc;             /* Text encoding - one of the TEXT_Utf* values */

   u8 incrKey;         /* Increase 2nd key by epsilon before comparison */

   int nField;         /* Number of entries in aColl[] */

   u8 *aSortOrder;     /* If defined an aSortOrder[i] is true, sort DESC */

   CollSeq *aColl[1];  /* Collating sequence for each term of the key */

 };

 /*

 ** Each SQL index is represented in memory by an

 ** instance of the following structure.

 **

 ** The columns of the table that are to be indexed are described

 ** by the aiColumn[] field of this structure.  For example, suppose

 ** we have the following table and index:

 **

 **     CREATE TABLE Ex1(c1 int, c2 int, c3 text);

 **     CREATE INDEX Ex2 ON Ex1(c3,c1);

 **

 ** In the Table structure describing Ex1, nCol==3 because there are

 ** three columns in the table.  In the Index structure describing

 ** Ex2, nColumn==2 since 2 of the 3 columns of Ex1 are indexed.

 ** The value of aiColumn is {2, 0}.  aiColumn[0]==2 because the 

 ** first column to be indexed (c3) has an index of 2 in Ex1.aCol[].

 ** The second column to be indexed (c1) has an index of 0 in

 ** Ex1.aCol[], hence Ex2.aiColumn[1]==0.

 **

 ** The Index.onError field determines whether or not the indexed columns

 ** must be unique and what to do if they are not.  When Index.onError=OE_None,

 ** it means this is not a unique index.  Otherwise it is a unique index

 ** and the value of Index.onError indicate the which conflict resolution 

 ** algorithm to employ whenever an attempt is made to insert a non-unique

 ** element.

 */

 struct Index {

   char *zName;     /* Name of this index */

   int nColumn;     /* Number of columns in the table used by this index */

   int *aiColumn;   /* Which columns are used by this index.  1st is 0 */

   unsigned *aiRowEst; /* Result of ANALYZE: Est. rows selected by each column */

   Table *pTable;   /* The SQL table being indexed */

   int tnum;        /* Page containing root of this index in database file */

   u8 onError;      /* OE_Abort, OE_Ignore, OE_Replace, or OE_None */

   u8 autoIndex;    /* True if is automatically created (ex: by UNIQUE) */

   char *zColAff;   /* String defining the affinity of each column */

   Index *pNext;    /* The next index associated with the same table */

   Schema *pSchema; /* Schema containing this index */

   u8 *aSortOrder;  /* Array of size Index.nColumn. True==DESC, False==ASC */

   char **azColl;   /* Array of collation sequence names for index */

 };

 /*

 ** Each token coming out of the lexer is an instance of

 ** this structure.  Tokens are also used as part of an expression.

 **

 ** Note if Token.z==0 then Token.dyn and Token.n are undefined and

 ** may contain random values.  Do not make any assuptions about Token.dyn

 ** and Token.n when Token.z==0.

 */

 struct Token {

   const unsigned char *z; /* Text of the token.  Not NULL-terminated! */

   unsigned dyn  : 1;      /* True for malloced memory, false for static */

   unsigned n    : 31;     /* Number of characters in this token */

 };

 /*

 ** An instance of this structure contains information needed to generate

 ** code for a SELECT that contains aggregate functions.

 **

 ** If Expr.op==TK_AGG_COLUMN or TK_AGG_FUNCTION then Expr.pAggInfo is a

 ** pointer to this structure.  The Expr.iColumn field is the index in

 ** AggInfo.aCol[] or AggInfo.aFunc[] of information needed to generate

 ** code for that node.

 **

 ** AggInfo.pGroupBy and AggInfo.aFunc.pExpr point to fields within the

 ** original Select structure that describes the SELECT statement.  These

 ** fields do not need to be freed when deallocating the AggInfo structure.

 */

 struct AggInfo {

   u8 directMode;          /* Direct rendering mode means take data directly

                           ** from source tables rather than from accumulators */

   u8 useSortingIdx;       /* In direct mode, reference the sorting index rather

                           ** than the source table */

   int sortingIdx;         /* Cursor number of the sorting index */

   ExprList *pGroupBy;     /* The group by clause */

   int nSortingColumn;     /* Number of columns in the sorting index */

   struct AggInfo_col {    /* For each column used in source tables */

     Table *pTab;             /* Source table */

     int iTable;              /* Cursor number of the source table */

     int iColumn;             /* Column number within the source table */

     int iSorterColumn;       /* Column number in the sorting index */

     int iMem;                /* Memory location that acts as accumulator */

     Expr *pExpr;             /* The original expression */

   } *aCol;

   int nColumn;            /* Number of used entries in aCol[] */

   int nColumnAlloc;       /* Number of slots allocated for aCol[] */

   int nAccumulator;       /* Number of columns that show through to the output.

                           ** Additional columns are used only as parameters to

                           ** aggregate functions */

   struct AggInfo_func {   /* For each aggregate function */

     Expr *pExpr;             /* Expression encoding the function */

     FuncDef *pFunc;          /* The aggregate function implementation */

     int iMem;                /* Memory location that acts as accumulator */

     int iDistinct;           /* Ephermeral table used to enforce DISTINCT */

   } *aFunc;

   int nFunc;              /* Number of entries in aFunc[] */

   int nFuncAlloc;         /* Number of slots allocated for aFunc[] */

 };

 /*

 ** Each node of an expression in the parse tree is an instance

 ** of this structure.

 **

 ** Expr.op is the opcode.  The integer parser token codes are reused

 ** as opcodes here.  For example, the parser defines TK_GE to be an integer

 ** code representing the ">=" operator.  This same integer code is reused

 ** to represent the greater-than-or-equal-to operator in the expression

 ** tree.

 **

 ** Expr.pRight and Expr.pLeft are subexpressions.  Expr.pList is a list

 ** of argument if the expression is a function.

 **

 ** Expr.token is the operator token for this node.  For some expressions

 ** that have subexpressions, Expr.token can be the complete text that gave

 ** rise to the Expr.  In the latter case, the token is marked as being

 ** a compound token.

 **

 ** An expression of the form ID or ID.ID refers to a column in a table.

 ** For such expressions, Expr.op is set to TK_COLUMN and Expr.iTable is

 ** the integer cursor number of a VDBE cursor pointing to that table and

 ** Expr.iColumn is the column number for the specific column.  If the

 ** expression is used as a result in an aggregate SELECT, then the

 ** value is also stored in the Expr.iAgg column in the aggregate so that

 ** it can be accessed after all aggregates are computed.

 **

 ** If the expression is a function, the Expr.iTable is an integer code

 ** representing which function.  If the expression is an unbound variable

 ** marker (a question mark character '?' in the original SQL) then the

 ** Expr.iTable holds the index number for that variable.

 **

 ** If the expression is a subquery then Expr.iColumn holds an integer

 ** register number containing the result of the subquery.  If the

 ** subquery gives a constant result, then iTable is -1.  If the subquery

 ** gives a different answer at different times during statement processing

 ** then iTable is the address of a subroutine that computes the subquery.

 **

 ** The Expr.pSelect field points to a SELECT statement.  The SELECT might

 ** be the right operand of an IN operator.  Or, if a scalar SELECT appears

 ** in an expression the opcode is TK_SELECT and Expr.pSelect is the only

 ** operand.

 **

 ** If the Expr is of type OP_Column, and the table it is selecting from

 ** is a disk table or the "old.*" pseudo-table, then pTab points to the

 ** corresponding table definition.

 */

 struct Expr {

   u8 op;                 /* Operation performed by this node */

   char affinity;         /* The affinity of the column or 0 if not a column */

   u16 flags;             /* Various flags.  See below */

   CollSeq *pColl;        /* The collation type of the column or 0 */

   Expr *pLeft, *pRight;  /* Left and right subnodes */

   ExprList *pList;       /* A list of expressions used as function arguments

                          ** or in "<expr> IN (<expr-list)" */

   Token token;           /* An operand token */

   Token span;            /* Complete text of the expression */

   int iTable, iColumn;   /* When op==TK_COLUMN, then this expr node means the

                          ** iColumn-th field of the iTable-th table. */

   AggInfo *pAggInfo;     /* Used by TK_AGG_COLUMN and TK_AGG_FUNCTION */

   int iAgg;              /* Which entry in pAggInfo->aCol[] or ->aFunc[] */

   int iRightJoinTable;   /* If EP_FromJoin, the right table of the join */

   Select *pSelect;       /* When the expression is a sub-select.  Also the

                          ** right side of "<expr> IN (<select>)" */

   Table *pTab;           /* Table for OP_Column expressions. */

   Schema *pSchema;

 #if SQLITE_MAX_EXPR_DEPTH>0

   int nHeight;           /* Height of the tree headed by this node */

 #endif

 };

 /*

 ** The following are the meanings of bits in the Expr.flags field.

 */

 #define EP_FromJoin     0x01  /* Originated in ON or USING clause of a join */

 #define EP_Agg          0x02  /* Contains one or more aggregate functions */

 #define EP_Resolved     0x04  /* IDs have been resolved to COLUMNs */

 #define EP_Error        0x08  /* Expression contains one or more errors */

 #define EP_Distinct     0x10  /* Aggregate function with DISTINCT keyword */

 #define EP_VarSelect    0x20  /* pSelect is correlated, not constant */

 #define EP_Dequoted     0x40  /* True if the string has been dequoted */

 #define EP_InfixFunc    0x80  /* True for an infix function: LIKE, GLOB, etc */

 #define EP_ExpCollate  0x100  /* Collating sequence specified explicitly */

 /*

 ** These macros can be used to test, set, or clear bits in the 

 ** Expr.flags field.

 */

 #define ExprHasProperty(E,P)     (((E)->flags&(P))==(P))

 #define ExprHasAnyProperty(E,P)  (((E)->flags&(P))!=0)

 #define ExprSetProperty(E,P)     (E)->flags|=(P)

 #define ExprClearProperty(E,P)   (E)->flags&=~(P)

 /*

 ** A list of expressions.  Each expression may optionally have a

 ** name.  An expr/name combination can be used in several ways, such

 ** as the list of "expr AS ID" fields following a "SELECT" or in the

 ** list of "ID = expr" items in an UPDATE.  A list of expressions can

 ** also be used as the argument to a function, in which case the a.zName

 ** field is not used.

 */

 struct ExprList {

   int nExpr;             /* Number of expressions on the list */

   int nAlloc;            /* Number of entries allocated below */

   int iECursor;          /* VDBE Cursor associated with this ExprList */

   struct ExprList_item {

     Expr *pExpr;           /* The list of expressions */

     char *zName;           /* Token associated with this expression */

     u8 sortOrder;          /* 1 for DESC or 0 for ASC */

     u8 isAgg;              /* True if this is an aggregate like count(*) */

     u8 done;               /* A flag to indicate when processing is finished */

   } *a;                  /* One entry for each expression */

 };

 /*

 ** 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) ...;

 **

 ** The IdList.a.idx field is used when the IdList represents the list of

 ** column names after a table name in an INSERT statement.  In the statement

 **

 **     INSERT INTO t(a,b,c) ...

 **

 ** If "a" is the k-th column of table "t", then IdList.a[0].idx==k.

 */

 struct IdList {

   struct IdList_item {

     char *zName;      /* Name of the identifier */

     int idx;          /* Index in some Table.aCol[] of a column named zName */

   } *a;

   int nId;         /* Number of identifiers on the list */

   int nAlloc;      /* Number of entries allocated for a[] below */

 };

 /*

 ** The bitmask datatype defined below is used for various optimizations.

 **

 ** Changing this from a 64-bit to a 32-bit type limits the number of

 ** tables in a join to 32 instead of 64.  But it also reduces the size

 ** of the library by 738 bytes on ix86.

 */

 typedef u64 Bitmask;

 /*

 ** The following structure describes the FROM clause of a SELECT statement.

 ** Each table or subquery in the FROM clause is a separate element of

 ** the SrcList.a[] array.

 **

 ** With the addition of multiple database support, the following structure

 ** can also be used to describe a particular table such as the table that

 ** is modified by an INSERT, DELETE, or UPDATE statement.  In standard SQL,

 ** such a table must be a simple name: ID.  But in SQLite, the table can

 ** now be identified by a database name, a dot, then the table name: ID.ID.

 **

 ** The jointype starts out showing the join type between the current table

 ** and the next table on the list.  The parser builds the list this way.

 ** But sqlite3SrcListShiftJoinType() later shifts the jointypes so that each

 ** jointype expresses the join between the table and the previous table.

 */

 struct SrcList {

   i16 nSrc;        /* Number of tables or subqueries in the FROM clause */

   i16 nAlloc;      /* Number of entries allocated in a[] below */

   struct SrcList_item {

     char *zDatabase;  /* Name of database holding this table */

     char *zName;      /* Name of the table */

     char *zAlias;     /* The "B" part of a "A AS B" phrase.  zName is the "A" */

     Table *pTab;      /* An SQL table corresponding to zName */

     Select *pSelect;  /* A SELECT statement used in place of a table name */

     u8 isPopulated;   /* Temporary table associated with SELECT is populated */

     u8 jointype;      /* Type of join between this able and the previous */

     int iCursor;      /* The VDBE cursor number used to access this table */

     Expr *pOn;        /* The ON clause of a join */

     IdList *pUsing;   /* The USING clause of a join */

     Bitmask colUsed;  /* Bit N (1<<N) set if column N or pTab is used */

   } a[1];             /* One entry for each identifier on the list */

 };

 /*

 ** Permitted values of the SrcList.a.jointype field

 */

 #define JT_INNER     0x0001    /* Any kind of inner or cross join */

 #define JT_CROSS     0x0002    /* Explicit use of the CROSS keyword */

 #define JT_NATURAL   0x0004    /* True for a "natural" join */

 #define JT_LEFT      0x0008    /* Left outer join */

 #define JT_RIGHT     0x0010    /* Right outer join */

 #define JT_OUTER     0x0020    /* The "OUTER" keyword is present */

 #define JT_ERROR     0x0040    /* unknown or unsupported join type */

 /*

 ** For each nested loop in a WHERE clause implementation, the WhereInfo

 ** structure contains a single instance of this structure.  This structure

 ** is intended to be private the the where.c module and should not be

 ** access or modified by other modules.

 **

 ** The pIdxInfo and pBestIdx fields are used to help pick the best

 ** index on a virtual table.  The pIdxInfo pointer contains indexing

 ** information for the i-th table in the FROM clause before reordering.

 ** All the pIdxInfo pointers are freed by whereInfoFree() in where.c.

 ** The pBestIdx pointer is a copy of pIdxInfo for the i-th table after

 ** FROM clause ordering.  This is a little confusing so I will repeat

 ** it in different words.  WhereInfo.a[i].pIdxInfo is index information 

 ** for WhereInfo.pTabList.a[i].  WhereInfo.a[i].pBestInfo is the

 ** index information for the i-th loop of the join.  pBestInfo is always

 ** either NULL or a copy of some pIdxInfo.  So for cleanup it is 

 ** sufficient to free all of the pIdxInfo pointers.

 ** 

 */

 struct WhereLevel {

   int iFrom;            /* Which entry in the FROM clause */

   int flags;            /* Flags associated with this level */

   int iMem;             /* First memory cell used by this level */

   int iLeftJoin;        /* Memory cell used to implement LEFT OUTER JOIN */

   Index *pIdx;          /* Index used.  NULL if no index */

   int iTabCur;          /* The VDBE cursor used to access the table */

   int iIdxCur;          /* The VDBE cursor used to acesss pIdx */

   int brk;              /* Jump here to break out of the loop */

   int nxt;              /* Jump here to start the next IN combination */

   int cont;             /* Jump here to continue with the next loop cycle */

   int top;              /* First instruction of interior of the loop */

   int op, p1, p2;       /* Opcode used to terminate the loop */

   int nEq;              /* Number of == or IN constraints on this loop */

   int nIn;              /* Number of IN operators constraining this loop */

   struct InLoop {

     int iCur;              /* The VDBE cursor used by this IN operator */

     int topAddr;           /* Top of the IN loop */

   } *aInLoop;           /* Information about each nested IN operator */

   sqlite3_index_info *pBestIdx;  /* Index information for this level */

   /* The following field is really not part of the current level.  But

   ** we need a place to cache index information for each table in the

   ** FROM clause and the WhereLevel structure is a convenient place.

   */

   sqlite3_index_info *pIdxInfo;  /* Index info for n-th source table */

 };

 /*

 ** The WHERE clause processing routine has two halves.  The

 ** first part does the start of the WHERE loop and the second

 ** half does the tail of the WHERE loop.  An instance of

 ** this structure is returned by the first half and passed

 ** into the second half to give some continuity.

 */

 struct WhereInfo {

   Parse *pParse;

   SrcList *pTabList;   /* List of tables in the join */

   int iTop;            /* The very beginning of the WHERE loop */

   int iContinue;       /* Jump here to continue with next record */

   int iBreak;          /* Jump here to break out of the loop */

   int nLevel;          /* Number of nested loop */

   sqlite3_index_info **apInfo;  /* Array of pointers to index info structures */

   WhereLevel a[1];     /* Information about each nest loop in the WHERE */

 };

 /*

 ** A NameContext defines a context in which to resolve table and column

 ** names.  The context consists of a list of tables (the pSrcList) field and

 ** a list of named expression (pEList).  The named expression list may

 ** be NULL.  The pSrc corresponds to the FROM clause of a SELECT or

 ** to the table being operated on by INSERT, UPDATE, or DELETE.  The

 ** pEList corresponds to the result set of a SELECT and is NULL for

 ** other statements.

 **

 ** NameContexts can be nested.  When resolving names, the inner-most 

 ** context is searched first.  If no match is found, the next outer

 ** context is checked.  If there is still no match, the next context

 ** is checked.  This process continues until either a match is found

 ** or all contexts are check.  When a match is found, the nRef member of

 ** the context containing the match is incremented. 

 **

 ** Each subquery gets a new NameContext.  The pNext field points to the

 ** NameContext in the parent query.  Thus the process of scanning the

 ** NameContext list corresponds to searching through successively outer

 ** subqueries looking for a match.

 */

 struct NameContext {

   Parse *pParse;       /* The parser */

   SrcList *pSrcList;   /* One or more tables used to resolve names */

   ExprList *pEList;    /* Optional list of named expressions */

   int nRef;            /* Number of names resolved by this context */

   int nErr;            /* Number of errors encountered while resolving names */

   u8 allowAgg;         /* Aggregate functions allowed here */

   u8 hasAgg;           /* True if aggregates are seen */

   u8 isCheck;          /* True if resolving names in a CHECK constraint */

   int nDepth;          /* Depth of subquery recursion. 1 for no recursion */

   AggInfo *pAggInfo;   /* Information about aggregates at this level */

   NameContext *pNext;  /* Next outer name context.  NULL for outermost */

 };

 /*

 ** 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

 ** limit and nOffset to the value of the offset (or 0 if there is not

 ** offset).  But later on, nLimit and nOffset become the memory locations

 ** in the VDBE that record the limit and offset counters.

 **

 ** addrOpenEphm[] entries contain the address of OP_OpenEphemeral opcodes.

 ** These addresses must be stored so that we can go back and fill in

 ** the P3_KEYINFO and P2 parameters later.  Neither the KeyInfo nor

 ** the number of columns in P2 can be computed at the same time

 ** as the OP_OpenEphm instruction is coded because not

 ** enough information about the compound query is known at that point.

 ** The KeyInfo for addrOpenTran[0] and [1] contains collating sequences

 ** for the result set.  The KeyInfo for addrOpenTran[2] contains collating

 ** sequences for the ORDER BY clause.

 */

 struct Select {

   ExprList *pEList;      /* The fields of the result */

   u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */

   u8 isDistinct;         /* True if the DISTINCT keyword is present */

   u8 isResolved;         /* True once sqlite3SelectResolve() has run. */

   u8 isAgg;              /* True if this is an aggregate query */

   u8 usesEphm;           /* True if uses an OpenEphemeral opcode */

   u8 disallowOrderBy;    /* Do not allow an ORDER BY to be attached if TRUE */

   char affinity;         /* MakeRecord with this affinity for SRT_Set */

   SrcList *pSrc;         /* The FROM clause */

   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 *pRightmost;    /* Right-most select in a compound select statement */

   Expr *pLimit;          /* LIMIT expression. NULL means not used. */

   Expr *pOffset;         /* OFFSET expression. NULL means not used. */

   int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */

   int addrOpenEphm[3];   /* OP_OpenEphem opcodes related to this select */

 };

 /*

 ** The results of a select can be distributed in several ways.

 */

 #define SRT_Union        1  /* Store result as keys in an index */

 #define SRT_Except       2  /* Remove result from a UNION index */

 #define SRT_Discard      3  /* Do not save the results anywhere */

 /* The ORDER BY clause is ignored for all of the above */

 #define IgnorableOrderby(X) (X<=SRT_Discard)

 #define SRT_Callback     4  /* Invoke a callback with each row of result */

 #define SRT_Mem          5  /* Store result in a memory cell */

 #define SRT_Set          6  /* Store non-null results as keys in an index */

 #define SRT_Table        7  /* Store result as data with an automatic rowid */

 #define SRT_EphemTab     8  /* Create transient tab and store like SRT_Table */

 #define SRT_Subroutine   9  /* Call a subroutine to handle results */

 #define SRT_Exists      10  /* Store 1 if the result is not empty */

 /*

 ** An SQL parser context.  A copy of this structure is passed through

 ** the parser and down into all the parser action routine in order to

 ** carry around information that is global to the entire parse.

 **

 ** The structure is divided into two parts.  When the parser and code

 ** generate call themselves recursively, the first part of the structure

 ** is constant but the second part is reset at the beginning and end of

 ** each recursion.

 **

 ** The nTableLock and aTableLock variables are only used if the shared-cache 

 ** feature is enabled (if sqlite3Tsd()->useSharedData is true). They are

 ** used to store the set of table-locks required by the statement being

 ** compiled. Function sqlite3TableLock() is used to add entries to the

 ** list.

 */

 struct Parse {

   sqlite3 *db;         /* The main database structure */

   int rc;              /* Return code from execution */

   char *zErrMsg;       /* An error message */

   Vdbe *pVdbe;         /* An engine for executing database bytecode */

   u8 colNamesSet;      /* TRUE after OP_ColumnName has been issued to pVdbe */

   u8 nameClash;        /* A permanent table name clashes with temp table name */

   u8 checkSchema;      /* Causes schema cookie check after an error */