**    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 1.805 2008/12/08 21:37:15 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build
................................................................................
  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 access pIdx */
  int addrBrk;          /* Jump here to break out of the loop */
  int addrNxt;          /* Jump here to start the next IN combination */
  int addrCont;         /* Jump here to continue with the next loop cycle */
  int addrFirst;        /* First instruction of interior of the loop */
  int op, p1, p2, p5;   /* 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 addrInTop;         /* Top of the IN loop */
  } *aInLoop;           /* Information about each nested IN operator */
  sqlite3_index_info *pBestIdx;  /* Index information for this level */

**    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 1.806 2008/12/09 01:32:03 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build
................................................................................
  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 access pIdx */
  int addrBrk;          /* Jump here to break out of the loop */
  int addrNxt;          /* Jump here to start the next IN combination */
  int addrCont;         /* Jump here to continue with the next loop cycle */
  int addrFirst;        /* First instruction of interior of the loop */
  int op, p1, p2;       /* Opcode used to terminate the loop */
  u8 p5;                /* P5 operand of the opcode that terminates 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 addrInTop;         /* Top of the IN loop */
  } *aInLoop;           /* Information about each nested IN operator */
  sqlite3_index_info *pBestIdx;  /* Index information for this level */

**
******************************************************************************
**
** This file contains code that modified the OS layer in order to simulate
** the effect on the database file of an OS crash or power failure.  This
** is used to test the ability of SQLite to recover from those situations.
**
** $Id: test6.c,v 1.39 2008/06/06 11:11:26 danielk1977 Exp $
*/
#if SQLITE_TEST          /* This file is used for testing only */
#include "sqliteInt.h"
#include "tcl.h"

#ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */

................................................................................
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDlOpen(pVfs, zPath);
}
static void cfDlError(sqlite3_vfs *pCfVfs, int nByte, char *zErrMsg){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  pVfs->xDlError(pVfs, nByte, zErrMsg);
}
static void *cfDlSym(sqlite3_vfs *pCfVfs, void *pHandle, const char *zSymbol){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDlSym(pVfs, pHandle, zSymbol);
}
static void cfDlClose(sqlite3_vfs *pCfVfs, void *pHandle){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  pVfs->xDlClose(pVfs, pHandle);
}
static int cfRandomness(sqlite3_vfs *pCfVfs, int nByte, char *zBufOut){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;

**
******************************************************************************
**
** This file contains code that modified the OS layer in order to simulate
** the effect on the database file of an OS crash or power failure.  This
** is used to test the ability of SQLite to recover from those situations.
**
** $Id: test6.c,v 1.40 2008/12/09 01:32:03 drh Exp $
*/
#if SQLITE_TEST          /* This file is used for testing only */
#include "sqliteInt.h"
#include "tcl.h"

#ifndef SQLITE_OMIT_DISKIO  /* This file is a no-op if disk I/O is disabled */

................................................................................
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDlOpen(pVfs, zPath);
}
static void cfDlError(sqlite3_vfs *pCfVfs, int nByte, char *zErrMsg){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  pVfs->xDlError(pVfs, nByte, zErrMsg);
}
static void (*cfDlSym(sqlite3_vfs *pCfVfs, void *pH, const char *zSym))(void){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  return pVfs->xDlSym(pVfs, pH, zSym);
}
static void cfDlClose(sqlite3_vfs *pCfVfs, void *pHandle){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;
  pVfs->xDlClose(pVfs, pHandle);
}
static int cfRandomness(sqlite3_vfs *pCfVfs, int nByte, char *zBufOut){
  sqlite3_vfs *pVfs = (sqlite3_vfs *)pCfVfs->pAppData;

**
******************************************************************************
**
** This file contains code that modified the OS layer in order to simulate
** different device types (by overriding the return values of the 
** xDeviceCharacteristics() and xSectorSize() methods).
**
** $Id: test_devsym.c,v 1.8 2008/09/12 10:22:40 danielk1977 Exp $
*/
#if SQLITE_TEST          /* This file is used for testing only */

#include "sqlite3.h"
#include "sqliteInt.h"

/*
................................................................................
static int devsymOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int devsymDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int devsymAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int devsymFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
#ifndef SQLITE_OMIT_LOAD_EXTENSION
static void *devsymDlOpen(sqlite3_vfs*, const char *zFilename);
static void devsymDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void *devsymDlSym(sqlite3_vfs*,void*, const char *zSymbol);
static void devsymDlClose(sqlite3_vfs*, void*);
#endif /* SQLITE_OMIT_LOAD_EXTENSION */
static int devsymRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int devsymSleep(sqlite3_vfs*, int microseconds);
static int devsymCurrentTime(sqlite3_vfs*, double*);

static sqlite3_vfs devsym_vfs = {
................................................................................
static void devsymDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
  sqlite3OsDlError(g.pVfs, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void *devsymDlSym(sqlite3_vfs *pVfs, void *pHandle, const char *zSymbol){
  return sqlite3OsDlSym(g.pVfs, pHandle, zSymbol);
}

/*
** Close the dynamic library handle pHandle.
*/
static void devsymDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3OsDlClose(g.pVfs, pHandle);

**
******************************************************************************
**
** This file contains code that modified the OS layer in order to simulate
** different device types (by overriding the return values of the 
** xDeviceCharacteristics() and xSectorSize() methods).
**
** $Id: test_devsym.c,v 1.9 2008/12/09 01:32:03 drh Exp $
*/
#if SQLITE_TEST          /* This file is used for testing only */

#include "sqlite3.h"
#include "sqliteInt.h"

/*
................................................................................
static int devsymOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int devsymDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int devsymAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int devsymFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
#ifndef SQLITE_OMIT_LOAD_EXTENSION
static void *devsymDlOpen(sqlite3_vfs*, const char *zFilename);
static void devsymDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void (*devsymDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
static void devsymDlClose(sqlite3_vfs*, void*);
#endif /* SQLITE_OMIT_LOAD_EXTENSION */
static int devsymRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int devsymSleep(sqlite3_vfs*, int microseconds);
static int devsymCurrentTime(sqlite3_vfs*, double*);

static sqlite3_vfs devsym_vfs = {
................................................................................
static void devsymDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
  sqlite3OsDlError(g.pVfs, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*devsymDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
  return sqlite3OsDlSym(g.pVfs, p, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void devsymDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3OsDlClose(g.pVfs, pHandle);

**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** $Id: test_onefile.c,v 1.9 2008/06/26 10:54:12 danielk1977 Exp $
**
** OVERVIEW:
**
**   This file contains some example code demonstrating how the SQLite 
**   vfs feature can be used to have SQLite operate directly on an 
**   embedded media, without using an intermediate file system.
**
................................................................................
*/
static int fsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int fsDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int fsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int fsFullPathname(sqlite3_vfs*, const char *zName, int nOut,char *zOut);
static void *fsDlOpen(sqlite3_vfs*, const char *zFilename);
static void fsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void *fsDlSym(sqlite3_vfs*,void*, const char *zSymbol);
static void fsDlClose(sqlite3_vfs*, void*);
static int fsRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int fsSleep(sqlite3_vfs*, int microseconds);
static int fsCurrentTime(sqlite3_vfs*, double*);


typedef struct fs_vfs_t fs_vfs_t;
................................................................................
  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
  pParent->xDlError(pParent, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void *fsDlSym(sqlite3_vfs *pVfs, void *pHandle, const char *zSymbol){
  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
  return pParent->xDlSym(pParent, pHandle, zSymbol);
}

/*
** Close the dynamic library handle pHandle.
*/
static void fsDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;

**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** $Id: test_onefile.c,v 1.10 2008/12/09 01:32:03 drh Exp $
**
** OVERVIEW:
**
**   This file contains some example code demonstrating how the SQLite 
**   vfs feature can be used to have SQLite operate directly on an 
**   embedded media, without using an intermediate file system.
**
................................................................................
*/
static int fsOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
static int fsDelete(sqlite3_vfs*, const char *zName, int syncDir);
static int fsAccess(sqlite3_vfs*, const char *zName, int flags, int *);
static int fsFullPathname(sqlite3_vfs*, const char *zName, int nOut,char *zOut);
static void *fsDlOpen(sqlite3_vfs*, const char *zFilename);
static void fsDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
static void (*fsDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
static void fsDlClose(sqlite3_vfs*, void*);
static int fsRandomness(sqlite3_vfs*, int nByte, char *zOut);
static int fsSleep(sqlite3_vfs*, int microseconds);
static int fsCurrentTime(sqlite3_vfs*, double*);


typedef struct fs_vfs_t fs_vfs_t;
................................................................................
  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
  pParent->xDlError(pParent, nByte, zErrMsg);
}

/*
** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
*/
static void (*fsDlSym(sqlite3_vfs *pVfs, void *pH, const char *zSym))(void){
  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;
  return pParent->xDlSym(pParent, pH, zSym);
}

/*
** Close the dynamic library handle pHandle.
*/
static void fsDlClose(sqlite3_vfs *pVfs, void *pHandle){
  sqlite3_vfs *pParent = ((fs_vfs_t *)pVfs)->pParent;

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.334 2008/12/08 21:37:16 drh Exp $
*/
#include "sqliteInt.h"

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
................................................................................
** The number of terms in a join is limited by the number of bits
** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
** is only able to process joins with 64 or fewer tables.
*/
typedef struct WhereTerm WhereTerm;
struct WhereTerm {
  Expr *pExpr;            /* Pointer to the subexpression that is this term */
  i16 iParent;            /* Disable pWC->a[iParent] when this term disabled */
  i16 leftCursor;         /* Cursor number of X in "X <op> <expr>" */
  i16 leftColumn;         /* Column number of X in "X <op> <expr>" */
  u16 eOperator;          /* A WO_xx value describing <op> */
  u8 wtFlags;             /* TERM_xxx bit flags.  See below */
  u8 nChild;              /* Number of children that must disable us */
  WhereClause *pWC;       /* The clause this term is part of */
  Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
  Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
};
................................................................................
*/
struct WhereClause {
  Parse *pParse;           /* The parser context */
  ExprMaskSet *pMaskSet;   /* Mapping of table indices to bitmasks */
  int nTerm;               /* Number of terms */
  int nSlot;               /* Number of entries in a[] */
  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
  WhereTerm aStatic[10];   /* Initial static space for a[] */
};

/*
** An instance of the following structure keeps track of a mapping
** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
**
** The VDBE cursor numbers are small integers contained in 
................................................................................
#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
#define WO_MATCH  0x040
#define WO_ISNULL 0x080
#define WO_OR     0x100



/*
** Value for wsFlags returned by bestIndex().  These flags determine which
** search strategies are appropriate.
**
** The least significant 12 bits is reserved as a mask for WO_ values above.
** The WhereLevel.wtFlags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
................................................................................
** This is true even if this routine fails to allocate a new WhereTerm.
**
** WARNING:  This routine might reallocate the space used to store
** WhereTerms.  All pointers to WhereTerms should be invalidated after
** calling this routine.  Such pointers may be reinitialized by referencing
** the pWC->a[] array.
*/
static int whereClauseInsert(WhereClause *pWC, Expr *p, u16 wtFlags){
  WhereTerm *pTerm;
  int idx;
  if( pWC->nTerm>=pWC->nSlot ){
    WhereTerm *pOld = pWC->a;
    sqlite3 *db = pWC->pParse->db;
    pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
    if( pWC->a==0 ){
................................................................................
    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
  }
}

/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static int operatorMask(int op){
  int c;
  assert( allowedOp(op) );
  if( op==TK_IN ){
    c = WO_IN;
  }else if( op==TK_ISNULL ){
    c = WO_ISNULL;
  }else if( op==TK_OR ){
    c = WO_OR;
  }else{

    c = WO_EQ<<(op-TK_EQ);
  }
  assert( op!=TK_ISNULL || c==WO_ISNULL );
  assert( op!=TK_OR || c==WO_OR );
  assert( op!=TK_IN || c==WO_IN );
  assert( op!=TK_EQ || c==WO_EQ );
  assert( op!=TK_LT || c==WO_LT );
  assert( op!=TK_LE || c==WO_LE );
................................................................................
** Return a pointer to the term.  Return 0 if not found.
*/
static WhereTerm *findTerm(
  WhereClause *pWC,     /* The WHERE clause to be searched */
  int iCur,             /* Cursor number of LHS */
  int iColumn,          /* Column number of LHS */
  Bitmask notReady,     /* RHS must not overlap with this mask */
  u16 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){
  WhereTerm *pTerm;
  int k;
  assert( iCur>=0 );

  for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
    if( pTerm->leftCursor==iCur
       && (pTerm->prereqRight & notReady)==0
       && pTerm->leftColumn==iColumn
       && (pTerm->eOperator & op)!=0
    ){
      if( pIdx && pTerm->eOperator!=WO_ISNULL ){
................................................................................

  /* If the sqlite3_index_info structure has not been previously
  ** allocated and initialized for this virtual table, then allocate
  ** and initialize it now
  */
  pIdxInfo = *ppIdxInfo;
  if( pIdxInfo==0 ){
    WhereTerm *pTerm;
    int nTerm;
    WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));

    /* Count the number of possible WHERE clause constraints referring
    ** to this virtual table */
    for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
      if( pTerm->leftCursor != pSrc->iCursor ) continue;
................................................................................
      if( pTerm->leftCursor != pSrc->iCursor ) continue;
      assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
      testcase( pTerm->eOperator==WO_IN );
      testcase( pTerm->eOperator==WO_ISNULL );
      if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
      pIdxCons[j].iColumn = pTerm->leftColumn;
      pIdxCons[j].iTermOffset = i;
      pIdxCons[j].op = pTerm->eOperator;
      /* The direct assignment in the previous line is possible only because
      ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
      ** following asserts verify this fact. */
      assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
      assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
      assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
      assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
................................................................................
  ** each time.
  */
  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
  pUsage = pIdxInfo->aConstraintUsage;
  for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
    j = pIdxCons->iTermOffset;
    pTerm = &pWC->a[j];
    pIdxCons->usable =  (pTerm->prereqRight & notReady)==0;
  }
  memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
  if( pIdxInfo->needToFreeIdxStr ){
    sqlite3_free(pIdxInfo->idxStr);
  }
  pIdxInfo->idxStr = 0;
  pIdxInfo->idxNum = 0;
................................................................................
    }

#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( pLevel->pBestIdx ){
      /* Case 0:  The table is a virtual-table.  Use the VFilter and VNext
      **          to access the data.
      */
      int j;
      int iReg;   /* P3 Value for OP_VFilter */
      sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
      int nConstraint = pBestIdx->nConstraint;
      struct sqlite3_index_constraint_usage *aUsage =
                                                  pBestIdx->aConstraintUsage;
      const struct sqlite3_index_constraint *aConstraint =
                                                  pBestIdx->aConstraint;

      iReg = sqlite3GetTempRange(pParse, nConstraint+2);
      pParse->disableColCache++;
      for(j=1; j<=nConstraint; j++){
        int k;
        for(k=0; k<nConstraint; k++){
          if( aUsage[k].argvIndex==j ){
            int iTerm = aConstraint[k].iTermOffset;
            assert( pParse->disableColCache );
            sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight, iReg+j+1);
            break;
          }
................................................................................
      int regBase;                 /* Base register holding constraint values */
      int r1;                      /* Temp register */
      WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
      WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
      int startEq;                 /* True if range start uses ==, >= or <= */
      int endEq;                   /* True if range end uses ==, >= or <= */
      int start_constraints;       /* Start of range is constrained */
      int k = pIdx->aiColumn[nEq]; /* Column for inequality constraints */
      int nConstraint;             /* Number of constraint terms */
      int op;



      /* Generate code to evaluate all constraint terms using == or IN
      ** and store the values of those terms in an array of registers
      ** starting at regBase.
      */
      regBase = codeAllEqualityTerms(pParse, pLevel, &wc, notReady, 2);
      addrNxt = pLevel->addrNxt;
................................................................................
      /* Check if the index cursor is past the end of the range. */
      op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
      testcase( op==OP_Noop );
      testcase( op==OP_IdxGE );
      testcase( op==OP_IdxLT );
      sqlite3VdbeAddOp4(v, op, iIdxCur, addrNxt, regBase,
                        SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
      sqlite3VdbeChangeP5(v, endEq!=bRev);

      /* If there are inequality constraints, check that the value
      ** of the table column that the inequality contrains is not NULL.
      ** If it is, jump to the next iteration of the loop.
      */
      r1 = sqlite3GetTempReg(pParse);
      testcase( pLevel->wsFlags & WHERE_BTM_LIMIT );

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.335 2008/12/09 01:32:03 drh Exp $
*/
#include "sqliteInt.h"

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
................................................................................
** The number of terms in a join is limited by the number of bits
** in prereqRight and prereqAll.  The default is 64 bits, hence SQLite
** is only able to process joins with 64 or fewer tables.
*/
typedef struct WhereTerm WhereTerm;
struct WhereTerm {
  Expr *pExpr;            /* Pointer to the subexpression that is this term */
  int iParent;            /* Disable pWC->a[iParent] when this term disabled */
  int leftCursor;         /* Cursor number of X in "X <op> <expr>" */
  int leftColumn;         /* Column number of X in "X <op> <expr>" */
  u16 eOperator;          /* A WO_xx value describing <op> */
  u8 wtFlags;             /* TERM_xxx bit flags.  See below */
  u8 nChild;              /* Number of children that must disable us */
  WhereClause *pWC;       /* The clause this term is part of */
  Bitmask prereqRight;    /* Bitmask of tables used by pExpr->pRight */
  Bitmask prereqAll;      /* Bitmask of tables referenced by pExpr */
};
................................................................................
*/
struct WhereClause {
  Parse *pParse;           /* The parser context */
  ExprMaskSet *pMaskSet;   /* Mapping of table indices to bitmasks */
  int nTerm;               /* Number of terms */
  int nSlot;               /* Number of entries in a[] */
  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
  WhereTerm aStatic[4];    /* Initial static space for a[] */
};

/*
** An instance of the following structure keeps track of a mapping
** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
**
** The VDBE cursor numbers are small integers contained in 
................................................................................
#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))
#define WO_MATCH  0x040
#define WO_ISNULL 0x080
#define WO_OR     0x100

#define WO_ALL    0xfff       /* Mask of all possible WO_* values */

/*
** Value for wsFlags returned by bestIndex().  These flags determine which
** search strategies are appropriate.
**
** The least significant 12 bits is reserved as a mask for WO_ values above.
** The WhereLevel.wtFlags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
................................................................................
** This is true even if this routine fails to allocate a new WhereTerm.
**
** WARNING:  This routine might reallocate the space used to store
** WhereTerms.  All pointers to WhereTerms should be invalidated after
** calling this routine.  Such pointers may be reinitialized by referencing
** the pWC->a[] array.
*/
static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
  WhereTerm *pTerm;
  int idx;
  if( pWC->nTerm>=pWC->nSlot ){
    WhereTerm *pOld = pWC->a;
    sqlite3 *db = pWC->pParse->db;
    pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
    if( pWC->a==0 ){
................................................................................
    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
  }
}

/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static u16 operatorMask(int op){
  u16 c;
  assert( allowedOp(op) );
  if( op==TK_IN ){
    c = WO_IN;
  }else if( op==TK_ISNULL ){
    c = WO_ISNULL;
  }else if( op==TK_OR ){
    c = WO_OR;
  }else{
    assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
    c = (u16)(WO_EQ<<(op-TK_EQ));
  }
  assert( op!=TK_ISNULL || c==WO_ISNULL );
  assert( op!=TK_OR || c==WO_OR );
  assert( op!=TK_IN || c==WO_IN );
  assert( op!=TK_EQ || c==WO_EQ );
  assert( op!=TK_LT || c==WO_LT );
  assert( op!=TK_LE || c==WO_LE );
................................................................................
** Return a pointer to the term.  Return 0 if not found.
*/
static WhereTerm *findTerm(
  WhereClause *pWC,     /* The WHERE clause to be searched */
  int iCur,             /* Cursor number of LHS */
  int iColumn,          /* Column number of LHS */
  Bitmask notReady,     /* RHS must not overlap with this mask */
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){
  WhereTerm *pTerm;
  int k;
  assert( iCur>=0 );
  op &= WO_ALL;
  for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
    if( pTerm->leftCursor==iCur
       && (pTerm->prereqRight & notReady)==0
       && pTerm->leftColumn==iColumn
       && (pTerm->eOperator & op)!=0
    ){
      if( pIdx && pTerm->eOperator!=WO_ISNULL ){
................................................................................

  /* If the sqlite3_index_info structure has not been previously
  ** allocated and initialized for this virtual table, then allocate
  ** and initialize it now
  */
  pIdxInfo = *ppIdxInfo;
  if( pIdxInfo==0 ){

    int nTerm;
    WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));

    /* Count the number of possible WHERE clause constraints referring
    ** to this virtual table */
    for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
      if( pTerm->leftCursor != pSrc->iCursor ) continue;
................................................................................
      if( pTerm->leftCursor != pSrc->iCursor ) continue;
      assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
      testcase( pTerm->eOperator==WO_IN );
      testcase( pTerm->eOperator==WO_ISNULL );
      if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
      pIdxCons[j].iColumn = pTerm->leftColumn;
      pIdxCons[j].iTermOffset = i;
      pIdxCons[j].op = (u8)pTerm->eOperator;
      /* The direct assignment in the previous line is possible only because
      ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
      ** following asserts verify this fact. */
      assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
      assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
      assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
      assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
................................................................................
  ** each time.
  */
  pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
  pUsage = pIdxInfo->aConstraintUsage;
  for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
    j = pIdxCons->iTermOffset;
    pTerm = &pWC->a[j];
    pIdxCons->usable =  (pTerm->prereqRight & notReady)==0 ?1:0;
  }
  memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
  if( pIdxInfo->needToFreeIdxStr ){
    sqlite3_free(pIdxInfo->idxStr);
  }
  pIdxInfo->idxStr = 0;
  pIdxInfo->idxNum = 0;
................................................................................
    }

#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( pLevel->pBestIdx ){
      /* Case 0:  The table is a virtual-table.  Use the VFilter and VNext
      **          to access the data.
      */

      int iReg;   /* P3 Value for OP_VFilter */
      sqlite3_index_info *pBestIdx = pLevel->pBestIdx;
      int nConstraint = pBestIdx->nConstraint;
      struct sqlite3_index_constraint_usage *aUsage =
                                                  pBestIdx->aConstraintUsage;
      const struct sqlite3_index_constraint *aConstraint =
                                                  pBestIdx->aConstraint;

      iReg = sqlite3GetTempRange(pParse, nConstraint+2);
      pParse->disableColCache++;
      for(j=1; j<=nConstraint; j++){

        for(k=0; k<nConstraint; k++){
          if( aUsage[k].argvIndex==j ){
            int iTerm = aConstraint[k].iTermOffset;
            assert( pParse->disableColCache );
            sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight, iReg+j+1);
            break;
          }
................................................................................
      int regBase;                 /* Base register holding constraint values */
      int r1;                      /* Temp register */
      WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
      WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
      int startEq;                 /* True if range start uses ==, >= or <= */
      int endEq;                   /* True if range end uses ==, >= or <= */
      int start_constraints;       /* Start of range is constrained */

      int nConstraint;             /* Number of constraint terms */
      int op;

      k = pIdx->aiColumn[nEq];     /* Column for inequality constraints */

      /* Generate code to evaluate all constraint terms using == or IN
      ** and store the values of those terms in an array of registers
      ** starting at regBase.
      */
      regBase = codeAllEqualityTerms(pParse, pLevel, &wc, notReady, 2);
      addrNxt = pLevel->addrNxt;
................................................................................
      /* Check if the index cursor is past the end of the range. */
      op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
      testcase( op==OP_Noop );
      testcase( op==OP_IdxGE );
      testcase( op==OP_IdxLT );
      sqlite3VdbeAddOp4(v, op, iIdxCur, addrNxt, regBase,
                        SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
      sqlite3VdbeChangeP5(v, endEq!=bRev ?1:0);

      /* If there are inequality constraints, check that the value
      ** of the table column that the inequality contrains is not NULL.
      ** If it is, jump to the next iteration of the loop.
      */
      r1 = sqlite3GetTempReg(pParse);
      testcase( pLevel->wsFlags & WHERE_BTM_LIMIT );