**     CREATE INDEX
**     DROP INDEX
**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
**
** $Id: build.c,v 1.331 2005/07/21 03:15:00 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** This routine is called when a new SQL statement is beginning to
** be parsed.  Initialize the pParse structure as needed.
................................................................................
  }else{
    tnum = pIndex->tnum;
    sqlite3VdbeAddOp(v, OP_Clear, tnum, pIndex->iDb);
  }
  sqlite3VdbeAddOp(v, OP_Integer, pIndex->iDb, 0);
  sqlite3VdbeOp3(v, OP_OpenWrite, iIdx, tnum,
                    (char*)&pIndex->keyInfo, P3_KEYINFO);
  sqlite3VdbeAddOp(v, OP_Integer, pTab->iDb, 0);
  sqlite3VdbeAddOp(v, OP_OpenRead, iTab, pTab->tnum);
  sqlite3VdbeAddOp(v, OP_SetNumColumns, iTab, pTab->nCol);
  addr1 = sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
  sqlite3GenerateIndexKey(v, pIndex, iTab);
  if( pIndex->onError!=OE_None ){
    int curaddr = sqlite3VdbeCurrentAddr(v);
    int addr2 = curaddr+4;
    sqlite3VdbeChangeP2(v, curaddr-1, addr2);
    sqlite3VdbeAddOp(v, OP_Rowid, iTab, 0);
................................................................................
    sqliteFree(pItem->zDatabase);
    sqliteFree(pItem->zName);
    sqliteFree(pItem->zAlias);
    sqlite3DeleteTable(0, pItem->pTab);
    sqlite3SelectDelete(pItem->pSelect);
    sqlite3ExprDelete(pItem->pOn);
    sqlite3IdListDelete(pItem->pUsing);
    sqlite3WhereIdxListDelete(pItem->pWIdx);
  }
  sqliteFree(pList);
}

/*
** Begin a transaction
*/

**     CREATE INDEX
**     DROP INDEX
**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
**
** $Id: build.c,v 1.332 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** This routine is called when a new SQL statement is beginning to
** be parsed.  Initialize the pParse structure as needed.
................................................................................
  }else{
    tnum = pIndex->tnum;
    sqlite3VdbeAddOp(v, OP_Clear, tnum, pIndex->iDb);
  }
  sqlite3VdbeAddOp(v, OP_Integer, pIndex->iDb, 0);
  sqlite3VdbeOp3(v, OP_OpenWrite, iIdx, tnum,
                    (char*)&pIndex->keyInfo, P3_KEYINFO);
  sqlite3OpenTableForReading(v, iTab, pTab);


  addr1 = sqlite3VdbeAddOp(v, OP_Rewind, iTab, 0);
  sqlite3GenerateIndexKey(v, pIndex, iTab);
  if( pIndex->onError!=OE_None ){
    int curaddr = sqlite3VdbeCurrentAddr(v);
    int addr2 = curaddr+4;
    sqlite3VdbeChangeP2(v, curaddr-1, addr2);
    sqlite3VdbeAddOp(v, OP_Rowid, iTab, 0);
................................................................................
    sqliteFree(pItem->zDatabase);
    sqliteFree(pItem->zName);
    sqliteFree(pItem->zAlias);
    sqlite3DeleteTable(0, pItem->pTab);
    sqlite3SelectDelete(pItem->pSelect);
    sqlite3ExprDelete(pItem->pOn);
    sqlite3IdListDelete(pItem->pUsing);

  }
  sqliteFree(pList);
}

/*
** Begin a transaction
*/

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** in order to generate code for DELETE FROM statements.
**
** $Id: delete.c,v 1.108 2005/07/08 13:08:00 drh Exp $
*/
#include "sqliteInt.h"

/*
** Look up every table that is named in pSrc.  If any table is not found,
** add an error message to pParse->zErrMsg and return NULL.  If all tables
** are found, return a pointer to the last table.
................................................................................
*/
void sqlite3OpenTableForReading(
  Vdbe *v,        /* Generate code into this VDBE */
  int iCur,       /* The cursor number of the table */
  Table *pTab     /* The table to be opened */
){
  sqlite3VdbeAddOp(v, OP_Integer, pTab->iDb, 0);
  sqlite3VdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
  VdbeComment((v, "# %s", pTab->zName));

  sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);
}


/*
** Generate code for a DELETE FROM statement.
**

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** in order to generate code for DELETE FROM statements.
**
** $Id: delete.c,v 1.109 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"

/*
** Look up every table that is named in pSrc.  If any table is not found,
** add an error message to pParse->zErrMsg and return NULL.  If all tables
** are found, return a pointer to the last table.
................................................................................
*/
void sqlite3OpenTableForReading(
  Vdbe *v,        /* Generate code into this VDBE */
  int iCur,       /* The cursor number of the table */
  Table *pTab     /* The table to be opened */
){
  sqlite3VdbeAddOp(v, OP_Integer, pTab->iDb, 0);

  VdbeComment((v, "# %s", pTab->zName));
  sqlite3VdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
  sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);
}


/*
** Generate code for a DELETE FROM statement.
**

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.212 2005/07/21 03:15:00 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**
................................................................................
    pTab = pNewItem->pTab = pOldItem->pTab;
    if( pTab ){
      pTab->nRef++;
    }
    pNewItem->pSelect = sqlite3SelectDup(pOldItem->pSelect);
    pNewItem->pOn = sqlite3ExprDup(pOldItem->pOn);
    pNewItem->pUsing = sqlite3IdListDup(pOldItem->pUsing);
    pNewItem->pWIdx = 0;
    pNewItem->colUsed = pOldItem->colUsed;
  }
  return pNew;
}
IdList *sqlite3IdListDup(IdList *p){
  IdList *pNew;
  int i;
................................................................................
** text z[0..n-1] on the stack.
*/
static void codeInteger(Vdbe *v, const char *z, int n){
  int i;
  if( sqlite3GetInt32(z, &i) ){
    sqlite3VdbeAddOp(v, OP_Integer, i, 0);
  }else if( sqlite3FitsIn64Bits(z) ){
    sqlite3VdbeOp3(v, OP_Integer, 0, 0, z, n);
  }else{
    sqlite3VdbeOp3(v, OP_Real, 0, 0, z, n);
  }
}

/*
** Generate code into the current Vdbe to evaluate the given

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.213 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**
................................................................................
    pTab = pNewItem->pTab = pOldItem->pTab;
    if( pTab ){
      pTab->nRef++;
    }
    pNewItem->pSelect = sqlite3SelectDup(pOldItem->pSelect);
    pNewItem->pOn = sqlite3ExprDup(pOldItem->pOn);
    pNewItem->pUsing = sqlite3IdListDup(pOldItem->pUsing);

    pNewItem->colUsed = pOldItem->colUsed;
  }
  return pNew;
}
IdList *sqlite3IdListDup(IdList *p){
  IdList *pNew;
  int i;
................................................................................
** text z[0..n-1] on the stack.
*/
static void codeInteger(Vdbe *v, const char *z, int n){
  int i;
  if( sqlite3GetInt32(z, &i) ){
    sqlite3VdbeAddOp(v, OP_Integer, i, 0);
  }else if( sqlite3FitsIn64Bits(z) ){
    sqlite3VdbeOp3(v, OP_Int64, 0, 0, z, n);
  }else{
    sqlite3VdbeOp3(v, OP_Real, 0, 0, z, n);
  }
}

/*
** Generate code into the current Vdbe to evaluate the given

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle INSERT statements in SQLite.
**
** $Id: insert.c,v 1.141 2005/07/08 17:13:47 drh Exp $
*/
#include "sqliteInt.h"

/*
** Set P3 of the most recently inserted opcode to a column affinity
** string for index pIdx. A column affinity string has one character
** for each column in the table, according to the affinity of the column:
................................................................................
  int op           /* OP_OpenRead or OP_OpenWrite */
){
  int i;
  Index *pIdx;
  Vdbe *v = sqlite3GetVdbe(pParse);
  assert( v!=0 );
  sqlite3VdbeAddOp(v, OP_Integer, pTab->iDb, 0);
  sqlite3VdbeAddOp(v, op, base, pTab->tnum);
  VdbeComment((v, "# %s", pTab->zName));

  sqlite3VdbeAddOp(v, OP_SetNumColumns, base, pTab->nCol);
  for(i=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    sqlite3VdbeAddOp(v, OP_Integer, pIdx->iDb, 0);

    sqlite3VdbeOp3(v, op, i+base, pIdx->tnum,
                   (char*)&pIdx->keyInfo, P3_KEYINFO);
  }
  if( pParse->nTab<=base+i ){
    pParse->nTab = base+i;
  }
}

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle INSERT statements in SQLite.
**
** $Id: insert.c,v 1.142 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"

/*
** Set P3 of the most recently inserted opcode to a column affinity
** string for index pIdx. A column affinity string has one character
** for each column in the table, according to the affinity of the column:
................................................................................
  int op           /* OP_OpenRead or OP_OpenWrite */
){
  int i;
  Index *pIdx;
  Vdbe *v = sqlite3GetVdbe(pParse);
  assert( v!=0 );
  sqlite3VdbeAddOp(v, OP_Integer, pTab->iDb, 0);

  VdbeComment((v, "# %s", pTab->zName));
  sqlite3VdbeAddOp(v, op, base, pTab->tnum);
  sqlite3VdbeAddOp(v, OP_SetNumColumns, base, pTab->nCol);
  for(i=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    sqlite3VdbeAddOp(v, OP_Integer, pIdx->iDb, 0);
    VdbeComment((v, "# %s", pIdx->zName));
    sqlite3VdbeOp3(v, op, i+base, pIdx->tnum,
                   (char*)&pIdx->keyInfo, P3_KEYINFO);
  }
  if( pParse->nTab<=base+i ){
    pParse->nTab = base+i;
  }
}

**    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: sqliteInt.h,v 1.395 2005/07/21 03:15:00 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it.  If the OS lacks
................................................................................
typedef struct Select Select;
typedef struct SrcList SrcList;
typedef struct Table Table;
typedef struct Token Token;
typedef struct TriggerStack TriggerStack;
typedef struct TriggerStep TriggerStep;
typedef struct Trigger Trigger;
typedef struct WhereIdx WhereIdx;
typedef struct WhereInfo WhereInfo;
typedef struct WhereLevel WhereLevel;

/*
** 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
................................................................................
    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 jointype;      /* Type of join between this table and the next */
    i16 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 */
    WhereIdx *pWIdx;  /* List of structures used by the optimizer */
    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
*/
................................................................................
/*
** 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.
*/
struct WhereLevel {


  int iMem;            /* Memory cell used by this level */

  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 cont;            /* Jump here to continue with the next loop cycle */
  int op, p1, p2;      /* Opcode used to terminate the loop */
  int iLeftJoin;       /* Memory cell used to implement LEFT OUTER JOIN */
  int top;             /* First instruction of interior of the loop */

  int inOp, inP1, inP2;/* Opcode used to implement an IN operator */
  int flags;           /* Flags associated with this level */
};

/*
** 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
................................................................................
void sqlite3AlterFinishAddColumn(Parse *, Token *);
void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
const char *sqlite3TestErrorName(int);
CollSeq *sqlite3GetCollSeq(sqlite3*, CollSeq *, const char *, int);
char sqlite3AffinityType(const Token*);
void sqlite3Analyze(Parse*, Token*, Token*);
int sqlite3InvokeBusyHandler(BusyHandler*);
void sqlite3WhereIdxListDelete(WhereIdx*);

#ifdef SQLITE_SSE
#include "sseInt.h"
#endif

#endif

**    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: sqliteInt.h,v 1.396 2005/07/21 18:23:20 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** These #defines should enable >2GB file support on Posix if the
** underlying operating system supports it.  If the OS lacks
................................................................................
typedef struct Select Select;
typedef struct SrcList SrcList;
typedef struct Table Table;
typedef struct Token Token;
typedef struct TriggerStack TriggerStack;
typedef struct TriggerStep TriggerStep;
typedef struct Trigger Trigger;

typedef struct WhereInfo WhereInfo;
typedef struct WhereLevel WhereLevel;

/*
** 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
................................................................................
    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 jointype;      /* Type of join between this table and the next */
    i16 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
*/
................................................................................
/*
** 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.
*/
struct WhereLevel {
  int iFrom;            /* Which entry in the FROM clause */
  int flags;            /* Flags associated with this level */
  int iMem;             /* 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 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 inOp, inP1, inP2; /* Opcode used to implement an IN operator */

};

/*
** 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
................................................................................
void sqlite3AlterFinishAddColumn(Parse *, Token *);
void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
const char *sqlite3TestErrorName(int);
CollSeq *sqlite3GetCollSeq(sqlite3*, CollSeq *, const char *, int);
char sqlite3AffinityType(const Token*);
void sqlite3Analyze(Parse*, Token*, Token*);
int sqlite3InvokeBusyHandler(BusyHandler*);


#ifdef SQLITE_SSE
#include "sseInt.h"
#endif

#endif

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle UPDATE statements.
**
** $Id: update.c,v 1.109 2005/07/08 13:08:00 drh Exp $
*/
#include "sqliteInt.h"

/*
** The most recently coded instruction was an OP_Column to retrieve column
** 'i' of table pTab. This routine sets the P3 parameter of the 
** OP_Column to the default value, if any.
................................................................................
*/
void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i){
  if( pTab && !pTab->pSelect ){
    sqlite3_value *pValue;
    u8 enc = sqlite3VdbeDb(v)->enc;
    Column *pCol = &pTab->aCol[i];
    sqlite3ValueFromExpr(pCol->pDflt, enc, pCol->affinity, &pValue);

    sqlite3VdbeChangeP3(v, -1, (const char *)pValue, P3_MEM);



  }
}

/*
** Process an UPDATE statement.
**
**   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle UPDATE statements.
**
** $Id: update.c,v 1.110 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"

/*
** The most recently coded instruction was an OP_Column to retrieve column
** 'i' of table pTab. This routine sets the P3 parameter of the 
** OP_Column to the default value, if any.
................................................................................
*/
void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i){
  if( pTab && !pTab->pSelect ){
    sqlite3_value *pValue;
    u8 enc = sqlite3VdbeDb(v)->enc;
    Column *pCol = &pTab->aCol[i];
    sqlite3ValueFromExpr(pCol->pDflt, enc, pCol->affinity, &pValue);
    if( pValue ){
      sqlite3VdbeChangeP3(v, -1, (const char *)pValue, P3_MEM);
    }else{
      VdbeComment((v, "# %s.%s", pTab->zName, pCol->zName));
    }
  }
}

/*
** Process an UPDATE statement.
**
**   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.475 2005/07/09 02:16:03 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
................................................................................
  if( rc==SQLITE_BUSY ){
    p->rc = SQLITE_BUSY;
    return SQLITE_BUSY;
  }
  return p->rc ? SQLITE_ERROR : SQLITE_DONE;
}

/* Opcode: Integer P1 * P3
**
** The integer value P1 is pushed onto the stack.  If P3 is not zero
** then it is assumed to be a string representation of the same integer.
** If P1 is zero and P3 is not zero, then the value is derived from P3.
**
** If the value cannot be represented as a 32-bits then its value
** will be in P3.
*/
case OP_Integer: {
  pTos++;
  if( pOp->p3==0 ){
    pTos->flags = MEM_Int;
    pTos->i = pOp->p1;






  }else{




    pTos->flags = MEM_Str|MEM_Static|MEM_Term;
    pTos->z = pOp->p3;
    pTos->n = strlen(pTos->z);
    pTos->enc = SQLITE_UTF8;
    pTos->i = sqlite3VdbeIntValue(pTos);
    pTos->flags |= MEM_Int;
  }
  break;
}

/* Opcode: Real * * P3
**
** The string value P3 is converted to a real and pushed on to the stack.
*/
................................................................................
**
** If P1 is negative, then the record is stored on the stack rather than in
** a table.  For P1==-1, the top of the stack is used.  For P1==-2, the
** next on the stack is used.  And so forth.  The value pushed is always
** just a pointer into the record which is stored further down on the
** stack.  The column value is not copied. The number of columns in the
** record is stored on the stack just above the record itself.







*/
case OP_Column: {
  u32 payloadSize;   /* Number of bytes in the record */
  int p1 = pOp->p1;  /* P1 value of the opcode */
  int p2 = pOp->p2;  /* column number to retrieve */
  Cursor *pC = 0;    /* The VDBE cursor */
  char *zRec;        /* Pointer to complete record-data */
................................................................................
      pC->cacheValid = 1;
    }
  }

  /* Get the column information. If aOffset[p2] is non-zero, then 
  ** deserialize the value from the record. If aOffset[p2] is zero,
  ** then there are not enough fields in the record to satisfy the
  ** request. The value is NULL in this case.

  */
  if( aOffset[p2] ){
    assert( rc==SQLITE_OK );
    if( zRec ){
      zData = &zRec[aOffset[p2]];
    }else{
      len = sqlite3VdbeSerialTypeLen(aType[p2]);
................................................................................
        goto op_column_out;
      }
      zData = sMem.z;
    }
    sqlite3VdbeSerialGet(zData, aType[p2], pTos);
    pTos->enc = db->enc;
  }else{
    if( pOp->p3 ){
      sqlite3VdbeMemShallowCopy(pTos, (Mem *)(pOp->p3), MEM_Static);
    }else{
      pTos->flags = MEM_Null;
    }
  }

  /* If we dynamically allocated space to hold the data (in the

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.476 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
................................................................................
  if( rc==SQLITE_BUSY ){
    p->rc = SQLITE_BUSY;
    return SQLITE_BUSY;
  }
  return p->rc ? SQLITE_ERROR : SQLITE_DONE;
}

/* Opcode: Integer P1 * *
**
** The 32-bit integer value P1 is pushed onto the stack.





*/
case OP_Integer: {
  pTos++;

  pTos->flags = MEM_Int;
  pTos->i = pOp->p1;
  break;
}

/* Opcode: Int64 * * P3
**
** P3 is a string representation of an integer.  Convert that integer
** to a 64-bit value and push it onto the stack.
*/
case OP_Int64: {
  pTos++;
  assert( pOp->p3!=0 );
  pTos->flags = MEM_Str|MEM_Static|MEM_Term;
  pTos->z = pOp->p3;
  pTos->n = strlen(pTos->z);
  pTos->enc = SQLITE_UTF8;
  pTos->i = sqlite3VdbeIntValue(pTos);
  pTos->flags |= MEM_Int;

  break;
}

/* Opcode: Real * * P3
**
** The string value P3 is converted to a real and pushed on to the stack.
*/
................................................................................
**
** If P1 is negative, then the record is stored on the stack rather than in
** a table.  For P1==-1, the top of the stack is used.  For P1==-2, the
** next on the stack is used.  And so forth.  The value pushed is always
** just a pointer into the record which is stored further down on the
** stack.  The column value is not copied. The number of columns in the
** record is stored on the stack just above the record itself.
**
** If the column contains fewer than P2 fields, then push a NULL.  Or
** if P3 is of type P3_MEM, then push the P3 value.  The P3 value will
** be default value for a column that has been added using the ALTER TABLE
** ADD COLUMN command.  If P3 is an ordinary string, just push a NULL.
** When P3 is a string it is really just a comment describing the value
** to be pushed, not a default value.
*/
case OP_Column: {
  u32 payloadSize;   /* Number of bytes in the record */
  int p1 = pOp->p1;  /* P1 value of the opcode */
  int p2 = pOp->p2;  /* column number to retrieve */
  Cursor *pC = 0;    /* The VDBE cursor */
  char *zRec;        /* Pointer to complete record-data */
................................................................................
      pC->cacheValid = 1;
    }
  }

  /* Get the column information. If aOffset[p2] is non-zero, then 
  ** deserialize the value from the record. If aOffset[p2] is zero,
  ** then there are not enough fields in the record to satisfy the
  ** request.  In this case, set the value NULL or to P3 if P3 is
  ** a pointer to a Mem object.
  */
  if( aOffset[p2] ){
    assert( rc==SQLITE_OK );
    if( zRec ){
      zData = &zRec[aOffset[p2]];
    }else{
      len = sqlite3VdbeSerialTypeLen(aType[p2]);
................................................................................
        goto op_column_out;
      }
      zData = sMem.z;
    }
    sqlite3VdbeSerialGet(zData, aType[p2], pTos);
    pTos->enc = db->enc;
  }else{
    if( pOp->p3type==P3_MEM ){
      sqlite3VdbeMemShallowCopy(pTos, (Mem *)(pOp->p3), MEM_Static);
    }else{
      pTos->flags = MEM_Null;
    }
  }

  /* If we dynamically allocated space to hold the data (in the

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.149 2005/07/21 03:48:20 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8-1)

/*
** Determine the number of elements in an array.
*/
#define ARRAYSIZE(X)  (sizeof(X)/sizeof(X[0]))

/* Forward reference
*/
typedef struct WhereClause WhereClause;

/*
** An instance of the following structure holds information about how well
** a particular index helps in a search.  A list of such structures is
** attached to each SrcList_item of a SrcList.
*/
struct WhereIdx {
  Index *pIdx;      /* The index under consideration */
  Bitmask prereq;   /* Prerequesite FROM clause elements for using this index */
  int nEqTerm;      /* Number of Idx column constrainted by == or IN */
  int nTerm;        /* Total number of Index Columns used */
  int flags;        /* Flags.  See below */
  double rRowEst;   /* Estimated number of rows selected */
  double rScore;    /* Score of this index */
  WhereIdx *pNext;  /* Next WhereIdx on the same FROM clause element */
};

/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause.  Each WHERE
** clause subexpression is separated from the others by an AND operator.
**
** All WhereTerms are collected into a single WhereClause structure.  
** The following identity holds:
................................................................................
**      foreach row1 in t1 do       \    Code generated
**        foreach row2 in t2 do      |-- by sqlite3WhereBegin()
**          foreach row3 in t3 do   /
**            ...
**          end                     \    Code generated
**        end                        |-- by sqlite3WhereEnd()
**      end                         /




**
** There are Btree cursors associated with each table.  t1 uses cursor
** number pTabList->a[0].iCursor.  t2 uses the cursor pTabList->a[1].iCursor.
** And so forth.  This routine generates code to open those VDBE cursors
** and sqlite3WhereEnd() generates the code to close them.
**
** The code that sqlite3WhereBegin() generates leaves the cursors named
................................................................................
  int brk, cont = 0;         /* Addresses used during code generation */
  Bitmask notReady;          /* Cursors that are not yet positioned */
  WhereTerm *pTerm;          /* A single term in the WHERE clause */
  ExprMaskSet maskSet;       /* The expression mask set */
  WhereClause wc;            /* The WHERE clause is divided into these terms */
  struct SrcList_item *pTabItem;  /* A single entry from pTabList */
  WhereLevel *pLevel;             /* A single level in the pWInfo list */


  /* The number of terms in the FROM clause is limited by the number of
  ** bits in a Bitmask 
  */
  if( pTabList->nSrc>sizeof(Bitmask)*8 ){
    sqlite3ErrorMsg(pParse, "at most %d tables in a join",
       sizeof(Bitmask)*8);
    return 0;
  }

  /* Split the WHERE clause into separate subexpressions where each
  ** subexpression is separated by an AND operator.  If the wc.a[]
  ** array fills up, the last entry might point to an expression which
  ** contains additional unfactored AND operators.
  */
  initMaskSet(&maskSet);
  whereClauseInit(&wc, pParse);
  whereSplit(&wc, pWhere);
    
  /* Allocate and initialize the WhereInfo structure that will become the
  ** return value.
................................................................................
  ** expression and either jump over all of the code or fall thru.
  */
  if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstant(pWhere)) ){
    sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
    pWhere = 0;
  }

  /* Analyze all of the subexpressions.



  */
  for(i=0; i<pTabList->nSrc; i++){
    createMask(&maskSet, pTabList->a[i].iCursor);
  }
  for(i=wc.nTerm-1; i>=0; i--){
    exprAnalyze(pTabList, &maskSet, &wc.a[i]);
  }

  /* Chose the best index to use for each table in the FROM clause





  */
  notReady = ~(Bitmask)0;
  pTabItem = pTabList->a;
  pLevel = pWInfo->a;
  for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
    Index *pBest;
    int flags;
















    bestIndex(pParse, &wc, pTabItem, notReady,
              (i==0 && ppOrderBy) ? *ppOrderBy : 0,
              &pBest, &flags);












    if( flags & WHERE_ORDERBY ){
      *ppOrderBy = 0;
    }
    pLevel->flags = flags;
    pLevel->pIdx = pBest;
    if( pBest ){
      pLevel->iIdxCur = pParse->nTab++;
    }else{
      pLevel->iIdxCur = -1;
    }
    notReady &= ~getMask(&maskSet, pTabItem->iCursor);

  }

  /* Open all tables in the pTabList and any indices selected for
  ** searching those tables.
  */
  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
  pLevel = pWInfo->a;
  for(i=0, pTabItem=pTabList->a; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
    Table *pTab;
    Index *pIx;
    int iIdxCur = pLevel->iIdxCur;


    pTab = pTabItem->pTab;
    if( pTab->isTransient || pTab->pSelect ) continue;
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3OpenTableForReading(v, pTabItem->iCursor, pTab);
    }
    pLevel->iTabCur = pTabItem->iCursor;
    if( (pIx = pLevel->pIdx)!=0 ){
      sqlite3VdbeAddOp(v, OP_Integer, pIx->iDb, 0);

      sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
                     (char*)&pIx->keyInfo, P3_KEYINFO);
    }
    if( (pLevel->flags & WHERE_IDX_ONLY)!=0 ){
      sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
    }
    sqlite3CodeVerifySchema(pParse, pTab->iDb);

#ifdef SQLITE_TEST
    /* Record in the query plan information about the current table
    ** and the index used to access it (if any).  If the table itself
    ** is not used, its name is just '{}'.  If no index is used
    ** the index is listed as "{}"
    */
    {
      char *z = pTabItem->zAlias;
      int n;
      if( z==0 ) z = pTab->zName;
      n = strlen(z);
      if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
        if( pLevel->flags & WHERE_IDX_ONLY ){
          strcpy(&sqlite3_query_plan[nQPlan], "{}");
          nQPlan += 2;
        }else{
          strcpy(&sqlite3_query_plan[nQPlan], z);
          nQPlan += n;
        }
        sqlite3_query_plan[nQPlan++] = ' ';
      }
      if( pIx==0 ){
        strcpy(&sqlite3_query_plan[nQPlan], " {}");
        nQPlan += 3;
      }else{
        n = strlen(pIx->zName);
        if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
          strcpy(&sqlite3_query_plan[nQPlan], pIx->zName);
          nQPlan += n;
          sqlite3_query_plan[nQPlan++] = ' ';
        }
      }
    }
#endif
  }
  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);

#ifdef SQLITE_TEST
  /* Terminate the query plan description
  */
  while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
    sqlite3_query_plan[--nQPlan] = 0;
  }
  sqlite3_query_plan[nQPlan] = 0;
  nQPlan = 0;
#endif

  /* Generate the code to do the search


  */
  notReady = ~(Bitmask)0;
  pLevel = pWInfo->a;
  pTabItem = pTabList->a;
  for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
    int j;
    int iCur = pTabItem->iCursor;  /* The VDBE cursor for the table */
    Index *pIdx;       /* The index we will be using */
    int iIdxCur;       /* The VDBE cursor for the index */
    int omitTable;     /* True if we use the index only */




    pIdx = pLevel->pIdx;
    iIdxCur = pLevel->iIdxCur;
    pLevel->inOp = OP_Noop;



    /* Check to see if it is appropriate to omit the use of the table
    ** here and use its index instead.




    */
    omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;



    /* If this is the right table of a LEFT OUTER JOIN, allocate and
    ** initialize a memory cell that records if this table matches any
    ** row of the left table of the join.
    */
    if( i>0 && (pTabList->a[i-1].jointype & JT_LEFT)!=0 ){
      if( !pParse->nMem ) pParse->nMem++;
      pLevel->iLeftJoin = pParse->nMem++;
      sqlite3VdbeAddOp(v, OP_Null, 0, 0);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
      VdbeComment((v, "# init LEFT JOIN no-match flag"));
    }

................................................................................
      **          construct.
      */
      pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
      assert( pTerm!=0 );
      assert( pTerm->pExpr!=0 );
      assert( pTerm->leftCursor==iCur );
      assert( omitTable==0 );
      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
      codeEqualityTerm(pParse, pTerm, brk, pLevel);
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk);
      sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk);
      VdbeComment((v, "pk"));
      pLevel->op = OP_Noop;
    }else if( pLevel->flags & WHERE_COLUMN_EQ ){
      /* Case 2:  There is an index and all terms of the WHERE clause that
      **          refer to the index using the "==" or "IN" operators.
      */
      int start;
      int nColumn;
      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);

      /* For each column of the index, find the term of the WHERE clause that
      ** constraints that column.  If the WHERE clause term is X=expr, then
      ** generate code to evaluate expr and leave the result on the stack */
      for(j=0; 1; j++){
        int k = pIdx->aiColumn[j];
        pTerm = findTerm(&wc, iCur, k, notReady, WO_EQ|WO_IN, pIdx);
................................................................................
        if( pTerm->operator==WO_IN ){
          j++;
          break;
        }
      }
      nColumn = j;
      pLevel->iMem = pParse->nMem++;
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      buildIndexProbe(v, nColumn, brk, pIdx);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);

      /* Generate code (1) to move to the first matching element of the table.
      ** Then generate code (2) that jumps to "brk" after the cursor is past
      ** the last matching element of the table.  The code (1) is executed
      ** once to initialize the search, the code (2) is executed before each
      ** iteration of the scan to see if the scan has finished. */
      if( pLevel->flags & WHERE_REVERSE ){
        /* Scan in reverse order */
        sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, brk);
        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, brk);
        pLevel->op = OP_Prev;
      }else{
        /* Scan in the forward order */
................................................................................
      pLevel->p2 = start;
    }else if( pLevel->flags & WHERE_ROWID_RANGE ){
      /* Case 3:  We have an inequality comparison against the ROWID field.
      */
      int testOp = OP_Noop;
      int start;
      WhereTerm *pStart, *pEnd;
      int bRev = (pLevel->flags & WHERE_REVERSE)!=0;

      assert( omitTable==0 );
      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      if( pLevel->flags & WHERE_BTM_LIMIT ){
        pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
        assert( pStart!=0 );
      }else{
        pStart = 0;
      }
      if( pLevel->flags & WHERE_TOP_LIMIT ){
................................................................................
      */
      int nEqColumn;
      int start;
      int leFlag=0, geFlag=0;
      int testOp;
      int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
      int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;
      int bRev = (pLevel->flags & WHERE_REVERSE)!=0;

      /* Evaluate the equality constraints
      */
      for(j=0; 1; j++){
        int k = pIdx->aiColumn[j];
        pTerm = findTerm(&wc, iCur, k, notReady, WO_EQ, pIdx);
        if( pTerm==0 ) break;
................................................................................
      ** used twice: once to make the termination key and once to make the
      ** start key.
      */
      for(j=0; j<nEqColumn; j++){
        sqlite3VdbeAddOp(v, OP_Dup, nEqColumn-1, 0);
      }

      /* Labels for the beginning and end of the loop
      */
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);

      /* Generate the termination key.  This is the key value that
      ** will end the search.  There is no termination key if there
      ** are no equality terms and no "X<..." term.
      **
      ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
      ** key computed here really ends up being the start key.
      */
................................................................................
      pLevel->op = bRev ? OP_Prev : OP_Next;
      pLevel->p1 = iIdxCur;
      pLevel->p2 = start;
    }else{
      /* Case 5:  There is no usable index.  We must do a complete
      **          scan of the entire table.
      */
      int start;
      int opRewind;

      assert( omitTable==0 );
      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      if( pLevel->flags & WHERE_REVERSE ){
        opRewind = OP_Last;
        pLevel->op = OP_Prev;
      }else{
        opRewind = OP_Rewind;
        pLevel->op = OP_Next;
      }
      sqlite3VdbeAddOp(v, opRewind, iCur, brk);
      start = sqlite3VdbeCurrentAddr(v);
      pLevel->p1 = iCur;
      pLevel->p2 = start;

    }
    notReady &= ~getMask(&maskSet, iCur);

    /* Insert code to test every subexpression that can be completely
    ** computed using the current set of tables.
    */
    for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
................................................................................
      assert( pE!=0 );
      if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
        continue;
      }
      sqlite3ExprIfFalse(pParse, pE, cont, 1);
      pTerm->flags |= TERM_CODED;
    }
    brk = cont;

    /* For a LEFT OUTER JOIN, generate code that will record the fact that
    ** at least one row of the right table has matched the left table.  
    */
    if( pLevel->iLeftJoin ){
      pLevel->top = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp(v, OP_Integer, 1, 0);
................................................................................
  ** is not used, its name is just '{}'.  If no index is used
  ** the index is listed as "{}".  If the primary key is used the
  ** index name is '*'.
  */
  for(i=0; i<pTabList->nSrc; i++){
    char *z;
    int n;
    pTabItem = &pTabList->a[i];
    pLevel = &pWInfo->a[i];

    z = pTabItem->zAlias;
    if( z==0 ) z = pTabItem->pTab->zName;
    n = strlen(z);
    if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
      if( pLevel->flags & WHERE_IDX_ONLY ){
        strcpy(&sqlite3_query_plan[nQPlan], "{}");
        nQPlan += 2;
................................................................................
  while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
    sqlite3_query_plan[--nQPlan] = 0;
  }
  sqlite3_query_plan[nQPlan] = 0;
  nQPlan = 0;
#endif /* SQLITE_TEST // Testing and debugging use only */




  pWInfo->iContinue = cont;
  freeMaskSet(&maskSet);
  whereClauseClear(&wc);
  return pWInfo;
}

/*
................................................................................
** sqlite3WhereBegin() for additional information.
*/
void sqlite3WhereEnd(WhereInfo *pWInfo){
  Vdbe *v = pWInfo->pParse->pVdbe;
  int i;
  WhereLevel *pLevel;
  SrcList *pTabList = pWInfo->pTabList;
  struct SrcList_item *pTabItem;

  /* Generate loop termination code.
  */
  for(i=pTabList->nSrc-1; i>=0; i--){
    pLevel = &pWInfo->a[i];
    sqlite3VdbeResolveLabel(v, pLevel->cont);
    if( pLevel->op!=OP_Noop ){
................................................................................
  }

  /* The "break" point is here, just past the end of the outer loop.
  ** Set it.
  */
  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);

  /* Close all of the cursors that were opend by sqlite3WhereBegin.
  */
  pLevel = pWInfo->a;
  pTabItem = pTabList->a;
  for(i=0; i<pTabList->nSrc; i++, pTabItem++, pLevel++){
    Table *pTab = pTabItem->pTab;
    assert( pTab!=0 );
    if( pTab->isTransient || pTab->pSelect ) continue;
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
    }
    if( pLevel->pIdx!=0 ){
................................................................................
  }

  /* Final cleanup
  */
  sqliteFree(pWInfo);
  return;
}


/*
** Delete a list of WhereIdx structures.
*/
void sqlite3WhereIdxListDelete(WhereIdx *p){
  WhereIdx *pNext;
  while( p ){
    pNext = p->pNext;
    sqliteFree(p);
    p = pNext;
  }
}

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.150 2005/07/21 18:23:20 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

/*
** Determine the number of elements in an array.
*/
#define ARRAYSIZE(X)  (sizeof(X)/sizeof(X[0]))

/* Forward reference
*/
typedef struct WhereClause WhereClause;

















/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause.  Each WHERE
** clause subexpression is separated from the others by an AND operator.
**
** All WhereTerms are collected into a single WhereClause structure.  
** The following identity holds:
................................................................................
**      foreach row1 in t1 do       \    Code generated
**        foreach row2 in t2 do      |-- by sqlite3WhereBegin()
**          foreach row3 in t3 do   /
**            ...
**          end                     \    Code generated
**        end                        |-- by sqlite3WhereEnd()
**      end                         /
**
** Note that the loops might not be nested in the order in which they
** appear in the FROM clause if a different order is better able to make
** use of indices.
**
** There are Btree cursors associated with each table.  t1 uses cursor
** number pTabList->a[0].iCursor.  t2 uses the cursor pTabList->a[1].iCursor.
** And so forth.  This routine generates code to open those VDBE cursors
** and sqlite3WhereEnd() generates the code to close them.
**
** The code that sqlite3WhereBegin() generates leaves the cursors named
................................................................................
  int brk, cont = 0;         /* Addresses used during code generation */
  Bitmask notReady;          /* Cursors that are not yet positioned */
  WhereTerm *pTerm;          /* A single term in the WHERE clause */
  ExprMaskSet maskSet;       /* The expression mask set */
  WhereClause wc;            /* The WHERE clause is divided into these terms */
  struct SrcList_item *pTabItem;  /* A single entry from pTabList */
  WhereLevel *pLevel;             /* A single level in the pWInfo list */
  int iFrom;                      /* First unused FROM clause element */

  /* The number of tables in the FROM clause is limited by the number of
  ** bits in a Bitmask 
  */
  if( pTabList->nSrc>BMS ){
    sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);

    return 0;
  }

  /* Split the WHERE clause into separate subexpressions where each
  ** subexpression is separated by an AND operator.


  */
  initMaskSet(&maskSet);
  whereClauseInit(&wc, pParse);
  whereSplit(&wc, pWhere);
    
  /* Allocate and initialize the WhereInfo structure that will become the
  ** return value.
................................................................................
  ** expression and either jump over all of the code or fall thru.
  */
  if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstant(pWhere)) ){
    sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1);
    pWhere = 0;
  }

  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
  ** add new virtual terms onto the end of the WHERE clause.  We do not
  ** want to analyze these virtual terms, so start analyzing at the end
  ** and work forward so that they added virtual terms are never processed.
  */
  for(i=0; i<pTabList->nSrc; i++){
    createMask(&maskSet, pTabList->a[i].iCursor);
  }
  for(i=wc.nTerm-1; i>=0; i--){
    exprAnalyze(pTabList, &maskSet, &wc.a[i]);
  }

  /* Chose the best index to use for each table in the FROM clause.
  **
  ** This loop fills in the pWInfo->a[].pIdx and pWInfo->a[].flags fields
  ** with information
  ** Reorder tables if necessary in order to choose a good ordering.
  ** However, LEFT JOIN tables cannot be reordered.
  */
  notReady = ~(Bitmask)0;
  pTabItem = pTabList->a;
  pLevel = pWInfo->a;
  for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){


    Index *pIdx;                /* Index for FROM table at pTabItem */
    int flags;                  /* Flags asssociated with pIdx */
    double score;               /* The score for pIdx */
    int j;                      /* For looping over FROM tables */
    Index *pBest = 0;           /* The best index seen so far */
    int bestFlags = 0;          /* Flags associated with pBest */
    double bestScore = -1.0;    /* The score of pBest */
    int bestJ;                  /* The value of j */
    Bitmask m;                  /* Bitmask value for j or bestJ */

    for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
      m = getMask(&maskSet, pTabItem->iCursor);
      if( (m & notReady)==0 ){
        if( j==iFrom ) iFrom++;
        continue;
      }
      score = bestIndex(pParse, &wc, pTabItem, notReady,
                        (j==0 && ppOrderBy) ? *ppOrderBy : 0,
                        &pIdx, &flags);
      if( score>bestScore ){
        bestScore = score;
        pBest = pIdx;
        bestFlags = flags;
        bestJ = j;
      }
      if( (pTabItem->jointype & JT_LEFT)!=0
         || (j>0 && (pTabItem[-1].jointype & JT_LEFT)!=0)
      ){
        break;
      }
    }
    if( bestFlags & WHERE_ORDERBY ){
      *ppOrderBy = 0;
    }
    pLevel->flags = bestFlags;
    pLevel->pIdx = pBest;
    if( pBest ){
      pLevel->iIdxCur = pParse->nTab++;
    }else{
      pLevel->iIdxCur = -1;
    }
    notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor);
    pLevel->iFrom = bestJ;
  }

  /* Open all tables in the pTabList and any indices selected for
  ** searching those tables.
  */
  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
  pLevel = pWInfo->a;
  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    Table *pTab;
    Index *pIx;
    int iIdxCur = pLevel->iIdxCur;

    pTabItem = &pTabList->a[pLevel->iFrom];
    pTab = pTabItem->pTab;
    if( pTab->isTransient || pTab->pSelect ) continue;
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3OpenTableForReading(v, pTabItem->iCursor, pTab);
    }
    pLevel->iTabCur = pTabItem->iCursor;
    if( (pIx = pLevel->pIdx)!=0 ){
      sqlite3VdbeAddOp(v, OP_Integer, pIx->iDb, 0);
      VdbeComment((v, "# %s", pIx->zName));
      sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum,
                     (char*)&pIx->keyInfo, P3_KEYINFO);
    }
    if( (pLevel->flags & WHERE_IDX_ONLY)!=0 ){
      sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
    }
    sqlite3CodeVerifySchema(pParse, pTab->iDb);
  }



































  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);











  /* Generate the code to do the search.  Each iteration of the for
  ** loop below generates code for a single nested loop of the VM
  ** program.
  */
  notReady = ~(Bitmask)0;


  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    int j;
    int iCur = pTabItem->iCursor;  /* The VDBE cursor for the table */
    Index *pIdx;       /* The index we will be using */
    int iIdxCur;       /* The VDBE cursor for the index */
    int omitTable;     /* True if we use the index only */
    int bRev;          /* True if we need to scan in reverse order */

    pTabItem = &pTabList->a[pLevel->iFrom];
    iCur = pTabItem->iCursor;
    pIdx = pLevel->pIdx;
    iIdxCur = pLevel->iIdxCur;
    pLevel->inOp = OP_Noop;
    bRev = (pLevel->flags & WHERE_REVERSE)!=0;
    omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0;



    /* Create labels for the "break" and "continue" instructions
    ** for the current loop.  Jump to brk to break out of a loop.
    ** Jump to cont to go immediately to the next iteration of the
    ** loop.
    */

    brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
    cont = pLevel->cont = sqlite3VdbeMakeLabel(v);

    /* If this is the right table of a LEFT OUTER JOIN, allocate and
    ** initialize a memory cell that records if this table matches any
    ** row of the left table of the join.
    */
    if( pLevel->iFrom>0 && (pTabItem[-1].jointype & JT_LEFT)!=0 ){
      if( !pParse->nMem ) pParse->nMem++;
      pLevel->iLeftJoin = pParse->nMem++;
      sqlite3VdbeAddOp(v, OP_Null, 0, 0);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
      VdbeComment((v, "# init LEFT JOIN no-match flag"));
    }

................................................................................
      **          construct.
      */
      pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0);
      assert( pTerm!=0 );
      assert( pTerm->pExpr!=0 );
      assert( pTerm->leftCursor==iCur );
      assert( omitTable==0 );

      codeEqualityTerm(pParse, pTerm, brk, pLevel);

      sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk);
      sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk);
      VdbeComment((v, "pk"));
      pLevel->op = OP_Noop;
    }else if( pLevel->flags & WHERE_COLUMN_EQ ){
      /* Case 2:  There is an index and all terms of the WHERE clause that
      **          refer to the index using the "==" or "IN" operators.
      */
      int start;
      int nColumn;


      /* For each column of the index, find the term of the WHERE clause that
      ** constraints that column.  If the WHERE clause term is X=expr, then
      ** generate code to evaluate expr and leave the result on the stack */
      for(j=0; 1; j++){
        int k = pIdx->aiColumn[j];
        pTerm = findTerm(&wc, iCur, k, notReady, WO_EQ|WO_IN, pIdx);
................................................................................
        if( pTerm->operator==WO_IN ){
          j++;
          break;
        }
      }
      nColumn = j;
      pLevel->iMem = pParse->nMem++;

      buildIndexProbe(v, nColumn, brk, pIdx);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0);

      /* Generate code (1) to move to the first matching element of the table.
      ** Then generate code (2) that jumps to "brk" after the cursor is past
      ** the last matching element of the table.  The code (1) is executed
      ** once to initialize the search, the code (2) is executed before each
      ** iteration of the scan to see if the scan has finished. */
      if( bRev ){
        /* Scan in reverse order */
        sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, brk);
        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, brk);
        pLevel->op = OP_Prev;
      }else{
        /* Scan in the forward order */
................................................................................
      pLevel->p2 = start;
    }else if( pLevel->flags & WHERE_ROWID_RANGE ){
      /* Case 3:  We have an inequality comparison against the ROWID field.
      */
      int testOp = OP_Noop;
      int start;
      WhereTerm *pStart, *pEnd;


      assert( omitTable==0 );


      if( pLevel->flags & WHERE_BTM_LIMIT ){
        pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0);
        assert( pStart!=0 );
      }else{
        pStart = 0;
      }
      if( pLevel->flags & WHERE_TOP_LIMIT ){
................................................................................
      */
      int nEqColumn;
      int start;
      int leFlag=0, geFlag=0;
      int testOp;
      int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0;
      int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0;


      /* Evaluate the equality constraints
      */
      for(j=0; 1; j++){
        int k = pIdx->aiColumn[j];
        pTerm = findTerm(&wc, iCur, k, notReady, WO_EQ, pIdx);
        if( pTerm==0 ) break;
................................................................................
      ** used twice: once to make the termination key and once to make the
      ** start key.
      */
      for(j=0; j<nEqColumn; j++){
        sqlite3VdbeAddOp(v, OP_Dup, nEqColumn-1, 0);
      }






      /* Generate the termination key.  This is the key value that
      ** will end the search.  There is no termination key if there
      ** are no equality terms and no "X<..." term.
      **
      ** 2002-Dec-04: On a reverse-order scan, the so-called "termination"
      ** key computed here really ends up being the start key.
      */
................................................................................
      pLevel->op = bRev ? OP_Prev : OP_Next;
      pLevel->p1 = iIdxCur;
      pLevel->p2 = start;
    }else{
      /* Case 5:  There is no usable index.  We must do a complete
      **          scan of the entire table.
      */

      int opRewind;

      assert( omitTable==0 );
      if( bRev ){


        opRewind = OP_Last;
        pLevel->op = OP_Prev;
      }else{
        opRewind = OP_Rewind;
        pLevel->op = OP_Next;
      }


      pLevel->p1 = iCur;

      pLevel->p2 = 1 + sqlite3VdbeAddOp(v, opRewind, iCur, brk);
    }
    notReady &= ~getMask(&maskSet, iCur);

    /* Insert code to test every subexpression that can be completely
    ** computed using the current set of tables.
    */
    for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){
................................................................................
      assert( pE!=0 );
      if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
        continue;
      }
      sqlite3ExprIfFalse(pParse, pE, cont, 1);
      pTerm->flags |= TERM_CODED;
    }


    /* For a LEFT OUTER JOIN, generate code that will record the fact that
    ** at least one row of the right table has matched the left table.  
    */
    if( pLevel->iLeftJoin ){
      pLevel->top = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp(v, OP_Integer, 1, 0);
................................................................................
  ** is not used, its name is just '{}'.  If no index is used
  ** the index is listed as "{}".  If the primary key is used the
  ** index name is '*'.
  */
  for(i=0; i<pTabList->nSrc; i++){
    char *z;
    int n;

    pLevel = &pWInfo->a[i];
    pTabItem = &pTabList->a[pLevel->iFrom];
    z = pTabItem->zAlias;
    if( z==0 ) z = pTabItem->pTab->zName;
    n = strlen(z);
    if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
      if( pLevel->flags & WHERE_IDX_ONLY ){
        strcpy(&sqlite3_query_plan[nQPlan], "{}");
        nQPlan += 2;
................................................................................
  while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
    sqlite3_query_plan[--nQPlan] = 0;
  }
  sqlite3_query_plan[nQPlan] = 0;
  nQPlan = 0;
#endif /* SQLITE_TEST // Testing and debugging use only */

  /* Record the continuation address in the WhereInfo structure.  Then
  ** clean up and return.
  */
  pWInfo->iContinue = cont;
  freeMaskSet(&maskSet);
  whereClauseClear(&wc);
  return pWInfo;
}

/*
................................................................................
** sqlite3WhereBegin() for additional information.
*/
void sqlite3WhereEnd(WhereInfo *pWInfo){
  Vdbe *v = pWInfo->pParse->pVdbe;
  int i;
  WhereLevel *pLevel;
  SrcList *pTabList = pWInfo->pTabList;


  /* Generate loop termination code.
  */
  for(i=pTabList->nSrc-1; i>=0; i--){
    pLevel = &pWInfo->a[i];
    sqlite3VdbeResolveLabel(v, pLevel->cont);
    if( pLevel->op!=OP_Noop ){
................................................................................
  }

  /* The "break" point is here, just past the end of the outer loop.
  ** Set it.
  */
  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);

  /* Close all of the cursors that were opened by sqlite3WhereBegin.
  */
  for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
    struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];

    Table *pTab = pTabItem->pTab;
    assert( pTab!=0 );
    if( pTab->isTransient || pTab->pSelect ) continue;
    if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){
      sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0);
    }
    if( pLevel->pIdx!=0 ){
................................................................................
  }

  /* Final cleanup
  */
  sqliteFree(pWInfo);
  return;
}