SQLite

/*
** 2005 July 8
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code associated with the ANALYZE command.
**
** @(#) $Id: analyze.c,v 1.27 2008/01/03 00:01:24 drh Exp $
*/
#ifndef SQLITE_OMIT_ANALYZE
#include "sqliteInt.h"

/*
** This routine generates code that opens the sqlite_stat1 table on cursor
** iStatCur.

  ** by this vdbe program, lock it for writing at the shared-cache level. 
  ** If this vdbe did create the sqlite_stat1 table, then it must have 
  ** already obtained a schema-lock, making the write-lock redundant.
  */
  if( iRootPage>0 ){
    sqlite3TableLock(pParse, iDb, iRootPage, 1, "sqlite_stat1");
  }
  sqlite3VdbeAddOp1(v, OP_Integer, iDb);
  sqlite3VdbeAddOp2(v, OP_OpenWrite, iStatCur, iRootPage);
  sqlite3VdbeAddOp2(v, OP_SetNumColumns, iStatCur, 3);
}

/*
** Generate code to do an analysis of all indices associated with
** a single table.
*/

  iIdxCur = pParse->nTab;
  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);

    /* Open a cursor to the index to be analyzed
    */
    assert( iDb==sqlite3SchemaToIndex(pParse->db, pIdx->pSchema) );
    sqlite3VdbeAddOp1(v, OP_Integer, iDb);
    VdbeComment((v, "%s", pIdx->zName));
    sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIdx->tnum, 0,
        (char *)pKey, P4_KEYINFO_HANDOFF);

    nCol = pIdx->nColumn;
    if( iMem+nCol*2>=pParse->nMem ){
      pParse->nMem = iMem+nCol*2+1;
    }
    sqlite3VdbeAddOp2(v, OP_SetNumColumns, iIdxCur, nCol+1);

    /* Memory cells are used as follows:

**     CREATE INDEX
**     DROP INDEX
**     creating ID lists
**     BEGIN TRANSACTION
**     COMMIT
**     ROLLBACK
**
** $Id: build.c,v 1.453 2008/01/03 00:01:24 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.

/*
** Open the sqlite_master table stored in database number iDb for
** writing. The table is opened using cursor 0.
*/
void sqlite3OpenMasterTable(Parse *p, int iDb){
  Vdbe *v = sqlite3GetVdbe(p);
  sqlite3TableLock(p, iDb, MASTER_ROOT, 1, SCHEMA_TABLE(iDb));
  sqlite3VdbeAddOp1(v, OP_Integer, iDb);
  sqlite3VdbeAddOp2(v, OP_OpenWrite, 0, MASTER_ROOT);
  sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, 5); /* sqlite_master has 5 columns */
}

/*
** The token *pName contains the name of a database (either "main" or
** "temp" or the name of an attached db). This routine returns the
** index of the named database in db->aDb[], or -1 if the named db 

    ** a schema-lock excludes all other database users, the write-lock would
    ** be redundant.
    */
    if( pSelect ){
      SelectDest dest = {SRT_Table, 1, 0};
      Table *pSelTab;
      sqlite3VdbeAddOp1(v, OP_Dup, 0);
      sqlite3VdbeAddOp1(v, OP_Integer, iDb);
      sqlite3VdbeAddOp2(v, OP_OpenWrite, 1, 0);
      pParse->nTab = 2;
      sqlite3Select(pParse, pSelect, &dest, 0, 0, 0, 0);
      sqlite3VdbeAddOp1(v, OP_Close, 1);
      if( pParse->nErr==0 ){
        pSelTab = sqlite3ResultSetOfSelect(pParse, 0, pSelect);
        if( pSelTab==0 ) return;
        assert( p->aCol==0 );

  if( memRootPage>=0 ){
    sqlite3VdbeAddOp1(v, OP_MemLoad, memRootPage);
    tnum = 0;
  }else{
    tnum = pIndex->tnum;
    sqlite3VdbeAddOp2(v, OP_Clear, tnum, iDb);
  }
  sqlite3VdbeAddOp1(v, OP_Integer, iDb);
  pKey = sqlite3IndexKeyinfo(pParse, pIndex);
  sqlite3VdbeAddOp4(v, OP_OpenWrite, iIdx, tnum, 0, 
                    (char *)pKey, P4_KEYINFO_HANDOFF);
  sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
  addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
  sqlite3GenerateIndexKey(v, pIndex, iTab);
  if( pIndex->onError!=OE_None ){
    int curaddr = sqlite3VdbeCurrentAddr(v);
    int addr2 = curaddr+4;

**    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 1.140 2008/01/03 00:01:24 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.

  int opcode      /* OP_OpenRead or OP_OpenWrite */
){
  Vdbe *v;
  if( IsVirtual(pTab) ) return;
  v = sqlite3GetVdbe(p);
  assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
  sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);
  sqlite3VdbeAddOp1(v, OP_Integer, iDb);
  VdbeComment((v, "%s", pTab->zName));
  sqlite3VdbeAddOp2(v, opcode, iCur, pTab->tnum);
  sqlite3VdbeAddOp2(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 1.325 2008/01/03 00:01:24 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** Return the 'affinity' of the expression pExpr if any.
**

          iDb = sqlite3SchemaToIndex(db, pIdx->pSchema);
          sqlite3VdbeUsesBtree(v, iDb);

          sqlite3VdbeAddOp1(v, OP_MemLoad, iMem);
          iAddr = sqlite3VdbeAddOp2(v, OP_If, 0, iMem);
          sqlite3VdbeAddOp2(v, OP_MemInt, 1, iMem);
  
          sqlite3VdbeAddOp1(v, OP_Integer, iDb);
          VdbeComment((v, "%s", pIdx->zName));
          sqlite3VdbeAddOp4(v, OP_OpenRead, iTab, pIdx->tnum, 0,
                               pKey,P4_KEYINFO_HANDOFF);

          eType = IN_INDEX_INDEX;
          sqlite3VdbeAddOp2(v, OP_SetNumColumns, iTab, pIdx->nColumn);

          sqlite3VdbeJumpHere(v, iAddr);
        }
      }
    }

**    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 1.202 2008/01/03 00:01:24 drh Exp $
*/
#include "sqliteInt.h"

/*
** Set P4 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:

*/
static int readsTable(Vdbe *v, int iStartAddr, int iDb, Table *pTab){
  int i;
  int iEnd = sqlite3VdbeCurrentAddr(v);
  for(i=iStartAddr; i<iEnd; i++){
    VdbeOp *pOp = sqlite3VdbeGetOp(v, i);
    assert( pOp!=0 );
    if( pOp->opcode==OP_OpenRead ){
      VdbeOp *pPrior = &pOp[-1];
      int tnum = pOp->p2;
      assert( i>iStartAddr );
      assert( pPrior->opcode==OP_Integer );
      if( pPrior->p1==iDb ){
        Index *pIndex;
        if( tnum==pTab->tnum ){
          return 1;
        }
        for(pIndex=pTab->pIndex; pIndex; pIndex=pIndex->pNext){
          if( tnum==pIndex->tnum ){
            return 1;
          }
        }
      }
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( pOp->opcode==OP_VOpen && pOp->p4.p==(const char*)pTab->pVtab ){
      assert( pOp->p4.p!=0 );
      assert( pOp->p4type==P4_VTAB );

    int iCur = pParse->nTab;
    int addr;
    assert( v );
    addr = sqlite3VdbeCurrentAddr(v);
    memId = pParse->nMem+1;
    pParse->nMem += 2;
    sqlite3OpenTable(pParse, iCur, iDb, pDb->pSchema->pSeqTab, OP_OpenRead);
    sqlite3VdbeAddOp2(v, OP_Rewind, iCur, addr+13);
    sqlite3VdbeAddOp2(v, OP_Column, iCur, 0);
    sqlite3VdbeAddOp4(v, OP_String8, 0, 0, 0, pTab->zName, 0);
    sqlite3VdbeAddOp2(v, OP_Ne, 0x100, addr+12);
    sqlite3VdbeAddOp2(v, OP_Rowid, iCur, 0);
    sqlite3VdbeAddOp2(v, OP_MemStore, memId-1, 1);
    sqlite3VdbeAddOp2(v, OP_Column, iCur, 1);
    sqlite3VdbeAddOp2(v, OP_MemStore, memId, 1);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addr+13);
    sqlite3VdbeAddOp2(v, OP_Next, iCur, addr+4);
    sqlite3VdbeAddOp2(v, OP_Close, iCur, 0);
  }
  return memId;
}

/*
** Update the maximum rowid for an autoincrement calculation.

    Vdbe *v = pParse->pVdbe;
    Db *pDb = &pParse->db->aDb[iDb];
    int addr;
    assert( v );
    addr = sqlite3VdbeCurrentAddr(v);
    sqlite3OpenTable(pParse, iCur, iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
    sqlite3VdbeAddOp2(v, OP_MemLoad, memId-1, 0);
    sqlite3VdbeAddOp2(v, OP_NotNull, -1, addr+7);
    sqlite3VdbeAddOp2(v, OP_Pop, 1, 0);
    sqlite3VdbeAddOp2(v, OP_NewRowid, iCur, 0);
    sqlite3VdbeAddOp4(v, OP_String8, 0, 0, 0, pTab->zName, 0);
    sqlite3VdbeAddOp2(v, OP_MemLoad, memId, 0);
    sqlite3VdbeAddOp2(v, OP_MakeRecord, 2, 0);
    sqlite3VdbeAddOp2(v, OP_Insert, iCur, OPFLAG_APPEND);
    sqlite3VdbeAddOp2(v, OP_Close, iCur, 0);

  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
  v = sqlite3GetVdbe(pParse);
  assert( v!=0 );
  sqlite3OpenTable(pParse, base, iDb, pTab, op);
  for(i=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
    assert( pIdx->pSchema==pTab->pSchema );
    sqlite3VdbeAddOp2(v, OP_Integer, iDb, 0);
    VdbeComment((v, "%s", pIdx->zName));
    sqlite3VdbeAddOp4(v, op, i+base, pIdx->tnum, 0,
                      (char*)pKey, P4_KEYINFO_HANDOFF);

  }
  if( pParse->nTab<=base+i ){
    pParse->nTab = base+i;
  }
}

  for(pDestIdx=pDest->pIndex; pDestIdx; pDestIdx=pDestIdx->pNext){
    for(pSrcIdx=pSrc->pIndex; pSrcIdx; pSrcIdx=pSrcIdx->pNext){
      if( xferCompatibleIndex(pDestIdx, pSrcIdx) ) break;
    }
    assert( pSrcIdx );
    sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
    sqlite3VdbeAddOp2(v, OP_Integer, iDbSrc, 0);
    pKey = sqlite3IndexKeyinfo(pParse, pSrcIdx);
    VdbeComment((v, "%s", pSrcIdx->zName));
    sqlite3VdbeAddOp4(v, OP_OpenRead, iSrc, pSrcIdx->tnum, 0,
                      (char*)pKey, P4_KEYINFO_HANDOFF);
    sqlite3VdbeAddOp2(v, OP_Integer, iDbDest, 0);
    pKey = sqlite3IndexKeyinfo(pParse, pDestIdx);
    VdbeComment((v, "%s", pDestIdx->zName));
    sqlite3VdbeAddOp4(v, OP_OpenWrite, iDest, pDestIdx->tnum, 0,
                      (char*)pKey, P4_KEYINFO_HANDOFF);

    addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iSrc, 0);
    sqlite3VdbeAddOp2(v, OP_RowKey, iSrc, 0);
    sqlite3VdbeAddOp2(v, OP_IdxInsert, iDest, 1);
    sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1+1);
    sqlite3VdbeJumpHere(v, addr1);
  }
  sqlite3VdbeJumpHere(v, emptySrcTest);

**    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 SELECT statements in SQLite.
**
** $Id: select.c,v 1.378 2008/01/03 00:01:25 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.

    ** reused. This is important for statements of the form 
    ** "INSERT INTO x SELECT max() FROM x".
    */
    int iIdx;
    KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
    iIdx = pParse->nTab++;
    assert( pIdx->pSchema==pTab->pSchema );
    sqlite3VdbeAddOp2(v, OP_Integer, iDb, 0);
    sqlite3VdbeAddOp4(v, OP_OpenRead, iIdx, pIdx->tnum, 0,
        (char*)pKey, P4_KEYINFO_HANDOFF);
    if( seekOp==OP_Rewind ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, 0);
      sqlite3VdbeAddOp2(v, OP_MakeRecord, 1, 0);
      seekOp = OP_MoveGt;
    }
    if( pIdx->aSortOrder[0]==SQLITE_SO_DESC ){

**    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 1.149 2008/01/03 00:01:25 drh Exp $
*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Forward declaration */
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */

          break;
        }
      }
    }
    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
      if( openAll || aIdxUsed[i] ){
        KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
        sqlite3VdbeAddOp2(v, OP_Integer, iDb, 0);
        sqlite3VdbeAddOp4(v, OP_OpenWrite, iCur+i+1, pIdx->tnum, 0,
                       (char*)pKey, P4_KEYINFO_HANDOFF);
        assert( pParse->nTab>iCur+i+1 );
      }
    }

  }
  

**
** 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 1.665 2008/01/03 07:09:48 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor

    sqlite3ExpirePreparedStatements(db);
    rc = SQLITE_SCHEMA;
  }
  break;
}

/* Opcode: OpenRead P1 P2 P4
**
** Open a read-only cursor for the database table whose root page is
** P2 in a database file.  The database file is determined by an 
** integer from the top of the stack.  0 means the main database and
** 1 means the database used for temporary tables.  Give the new 
** cursor an identifier of P1.  The P1 values need not be contiguous
** but all P1 values should be small integers.  It is an error for
** P1 to be negative.
**
** If P2==0 then take the root page number from the next of the stack.
**
** There will be a read lock on the database whenever there is an
** open cursor.  If the database was unlocked prior to this instruction
** then a read lock is acquired as part of this instruction.  A read
** lock allows other processes to read the database but prohibits
** any other process from modifying the database.  The read lock is
** released when all cursors are closed.  If this instruction attempts
** to get a read lock but fails, the script terminates with an
** SQLITE_BUSY error code.
**
** The P4 value is a pointer to a KeyInfo structure that defines the
** content and collating sequence of indices.  P4 is NULL for cursors
** that are not pointing to indices.
**
** See also OpenWrite.
*/
/* Opcode: OpenWrite P1 P2 P4
**
** Open a read/write cursor named P1 on the table or index whose root
** page is P2.  If P2==0 then take the root page number from the stack.
**
** The P4 value is a pointer to a KeyInfo structure that defines the
** content and collating sequence of indices.  P4 is NULL for cursors
** that are not pointing to indices.
**
** This instruction works just like OpenRead except that it opens the cursor
** in read/write mode.  For a given table, there can be one or more read-only
** cursors or a single read/write cursor but not both.
**
** See also OpenRead.
*/
case OP_OpenRead:          /* no-push */
case OP_OpenWrite: {       /* no-push */
  int i = pOp->p1;
  int p2 = pOp->p2;

  int wrFlag;
  Btree *pX;
  int iDb;
  Cursor *pCur;
  Db *pDb;
  
  assert( pTos>=p->aStack );
  sqlite3VdbeMemIntegerify(pTos);
  iDb = pTos->u.i;
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos--;
  assert( iDb>=0 && iDb<db->nDb );
  assert( (p->btreeMask & (1<<iDb))!=0 );
  pDb = &db->aDb[iDb];
  pX = pDb->pBt;
  assert( pX!=0 );
  if( pOp->opcode==OP_OpenWrite ){
    wrFlag = 1;

    pCur->pKeyInfo = 0;
    pCur->pIncrKey = &pCur->bogusIncrKey;
  }
  switch( rc ){
    case SQLITE_BUSY: {
      p->pc = pc;
      p->rc = rc = SQLITE_BUSY;
      p->pTos = &pTos[1 + (pOp->p2<=0)]; /* Operands must remain on stack */
      goto vdbe_return;
    }
    case SQLITE_OK: {
      int flags = sqlite3BtreeFlags(pCur->pCursor);
      /* Sanity checking.  Only the lower four bits of the flags byte should
      ** be used.  Bit 3 (mask 0x08) is unpreditable.  The lower 3 bits
      ** (mask 0x07) should be either 5 (intkey+leafdata for tables) or

*************************************************************************
** Header file for the Virtual DataBase Engine (VDBE)
**
** This header defines the interface to the virtual database engine
** or VDBE.  The VDBE implements an abstract machine that runs a
** simple program to access and modify the underlying database.
**
** $Id: vdbe.h,v 1.119 2008/01/03 01:28:59 drh Exp $
*/
#ifndef _SQLITE_VDBE_H_
#define _SQLITE_VDBE_H_
#include <stdio.h>

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines

int sqlite3VdbeAddOp1(Vdbe*,int,int);
int sqlite3VdbeAddOp2(Vdbe*,int,int,int);
int sqlite3VdbeAddOp3(Vdbe*,int,int,int,int);
int sqlite3VdbeAddOp4(Vdbe*,int,int,int,int,const char *zP4,int);
int sqlite3VdbeAddOpList(Vdbe*, int nOp, VdbeOpList const *aOp);
void sqlite3VdbeChangeP1(Vdbe*, int addr, int P1);
void sqlite3VdbeChangeP2(Vdbe*, int addr, int P2);

void sqlite3VdbeJumpHere(Vdbe*, int addr);
void sqlite3VdbeChangeToNoop(Vdbe*, int addr, int N);
void sqlite3VdbeChangeP4(Vdbe*, int addr, const char *zP4, int N);
void sqlite3VdbeUsesBtree(Vdbe*, int);
VdbeOp *sqlite3VdbeGetOp(Vdbe*, int);
int sqlite3VdbeMakeLabel(Vdbe*);
void sqlite3VdbeDelete(Vdbe*);

void sqlite3VdbeChangeP2(Vdbe *p, int addr, int val){
  assert( val>=0 );
  assert( p==0 || p->magic==VDBE_MAGIC_INIT );
  if( p && addr>=0 && p->nOp>addr && p->aOp ){
    p->aOp[addr].p2 = val;
  }
}












/*
** Change the P2 operand of instruction addr so that it points to
** the address of the next instruction to be coded.
*/
void sqlite3VdbeJumpHere(Vdbe *p, int addr){
  sqlite3VdbeChangeP2(p, addr, p->nOp);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code used to implement incremental BLOB I/O.
**
** $Id: vdbeblob.c,v 1.16 2007/08/30 01:19:59 drh Exp $
*/

#include "sqliteInt.h"
#include "vdbeInt.h"

#ifndef SQLITE_OMIT_INCRBLOB

  ** The sqlite3_blob_close() function finalizes the vdbe program,
  ** which closes the b-tree cursor and (possibly) commits the 
  ** transaction.
  */
  static const VdbeOpList openBlob[] = {
    {OP_Transaction, 0, 0, 0},     /* 0: Start a transaction */
    {OP_VerifyCookie, 0, 0, 0},    /* 1: Check the schema cookie */
    {OP_Integer, 0, 0, 0},         /* 2: Database number */

    /* One of the following two instructions is replaced by an
    ** OP_Noop before exection.
    */
    {OP_OpenRead, 0, 0, 0},        /* 3: Open cursor 0 for reading */
    {OP_OpenWrite, 0, 0, 0},       /* 4: Open cursor 0 for read/write */
    {OP_SetNumColumns, 0, 0, 0},   /* 5: Num cols for cursor */

    {OP_Variable, 1, 0, 0},        /* 6: Push the rowid to the stack */
    {OP_NotExists, 0, 10, 0},      /* 7: Seek the cursor */
    {OP_Column, 0, 0, 0},          /* 8  */
    {OP_Callback, 0, 0, 0},        /* 9  */
    {OP_Close, 0, 0, 0},           /* 10 */
    {OP_Halt, 0, 0, 0},            /* 11 */
  };

  Vdbe *v = 0;
  int rc = SQLITE_OK;
  char zErr[128];

  zErr[0] = 0;

      /* Configure the OP_VerifyCookie */
      sqlite3VdbeChangeP1(v, 1, iDb);
      sqlite3VdbeChangeP2(v, 1, pTab->pSchema->schema_cookie);

      /* Make sure a mutex is held on the table to be accessed */
      sqlite3VdbeUsesBtree(v, iDb); 

      /* Configure the db number pushed onto the stack */
      sqlite3VdbeChangeP1(v, 2, iDb);

      /* Remove either the OP_OpenWrite or OpenRead. Set the P2 
      ** parameter of the other to pTab->tnum. 
      */
      sqlite3VdbeChangeToNoop(v, (flags ? 3 : 4), 1);
      sqlite3VdbeChangeP2(v, (flags ? 4 : 3), pTab->tnum);


      /* Configure the OP_SetNumColumns. Configure the cursor to
      ** think that the table has one more column than it really
      ** does. An OP_Column to retrieve this imaginary column will
      ** always return an SQL NULL. This is useful because it means
      ** we can invoke OP_Column to fill in the vdbe cursors type 
      ** and offset cache without causing any IO.
      */
      sqlite3VdbeChangeP2(v, 5, pTab->nCol+1);
      if( !db->mallocFailed ){
        sqlite3VdbeMakeReady(v, 1, 0, 1, 0);
      }
    }
   
    sqlite3BtreeLeaveAll(db);
    rc = sqlite3SafetyOff(db);

** 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 1.268 2008/01/03 00:01:26 drh Exp $
*/
#include "sqliteInt.h"

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

    }else{
      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
    }
    pLevel->iTabCur = pTabItem->iCursor;
    if( (pIx = pLevel->pIdx)!=0 ){
      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
      assert( pIx->pSchema==pTab->pSchema );
      sqlite3VdbeAddOp2(v, OP_Integer, iDb, 0);
      VdbeComment((v, "%s", pIx->zName));
      sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, 0,
                        (char*)pKey, P4_KEYINFO_HANDOFF);

      sqlite3VdbeAddOp2(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1);
    }
    sqlite3CodeVerifySchema(pParse, iDb);
  }
  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);

  /* Generate the code to do the search.  Each iteration of the for