SQLite

/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.347 2004/12/18 18:40:27 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 Db Db;
typedef struct AuthContext AuthContext;
typedef struct KeyClass KeyClass;
typedef struct CollSeq CollSeq;
typedef struct KeyInfo KeyInfo;
typedef struct SqlCursor SqlCursor;
typedef struct Fetch Fetch;


/*
** Each database file to be accessed by the system is an instance
** of the following structure.  There are normally two of these structures
** in the sqlite.aDb[] array.  aDb[0] is the main database file and
** aDb[1] is the database file used to hold temporary tables.  Additional
** databases may be attached.

** 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 */

  int iCur;            /* Cursor number used for this index */
  int score;           /* How well this indexed scored */
  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 bRev;            /* Do the scan in the reverse direction */
};

/*
** The WHERE clause processing routine has two halves.  The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop.  An instance of
** this structure is returned by the first half and passed
** into the second half to give some continuity.
*/
struct WhereInfo {
  Parse *pParse;
  SrcList *pTabList;   /* List of tables in the join */

  int iContinue;       /* Jump here to continue with next record */
  int iBreak;          /* Jump here to break out of the loop */
  int nLevel;          /* Number of nested loop */
  WhereLevel a[1];     /* Information about each nest loop in the WHERE */
};

/*

  Token sLastToken;    /* The last token parsed */
  const char *zSql;    /* All SQL text */
  const char *zTail;   /* All SQL text past the last semicolon parsed */
  Table *pNewTable;    /* A table being constructed by CREATE TABLE */
  Trigger *pNewTrigger;     /* Trigger under construct by a CREATE TRIGGER */
  TriggerStack *trigStack;  /* Trigger actions being coded */
  const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
  
};

/*
** An instance of the following structure can be declared on a stack and used
** to save the Parse.zAuthContext value so that it can be restored later.
*/
struct AuthContext {

**
** 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 1.433 2004/12/07 14:06:13 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

case OP_SetNumColumns: {
  assert( (pOp->p1)<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  p->apCsr[pOp->p1]->nField = pOp->p2;
  break;
}

/* Opcode: IdxColumn P1 * *
**
** P1 is a cursor opened on an index. Push the first field from the
** current index key onto the stack.
*/
/* Opcode: Column P1 P2 *
**
** Interpret the data that cursor P1 points to as a structure built using
** the MakeRecord instruction.  (See the MakeRecord opcode for additional
** information about the format of the data.) Push onto the stack the value
** of the P2-th column contained in the data.
**
** If the KeyAsData opcode has previously executed on this cursor, then the
** field might be extracted from the key rather than the data.
**
** 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_IdxColumn:
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 */
  BtCursor *pCrsr;   /* The BTree cursor */

  pTos--;
  break;
}

/* Opcode: IdxRecno P1 * *
**
** Push onto the stack an integer which is the varint located at the
** end of the index key pointed to by cursor P1.  These integer should be
** the record number of the table entry to which this index entry points.
**
** See also: Recno, MakeIdxKey.
*/
case OP_IdxRecno: {
  int i = pOp->p1;
  BtCursor *pCrsr;

** 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 1.122 2004/12/18 18:40:27 drh Exp $
*/
#include "sqliteInt.h"

/*
** 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.

      SWAP(unsigned, pInfo->prereqLeft, pInfo->prereqRight);
      SWAP(short int, pInfo->idxLeft, pInfo->idxRight);
    }
  }      

}

/*
** pOrderBy is an ORDER BY clause from a SELECT statement.  pTab is the
** left-most table in the FROM clause of that same SELECT statement and
** the table has a cursor number of "base".
**
** This routine attempts to find an index for pTab that generates the
** correct record sequence for the given ORDER BY clause.  The return value
** is a pointer to an index that does the job.  NULL is returned if the
** table has no index that will generate the correct sort order.
**
** If there are two or more indices that generate the correct sort order
** and pPreferredIdx is one of those indices, then return pPreferredIdx.
**
** nEqCol is the number of columns of pPreferredIdx that are used as
** equality constraints.  Any index returned must have exactly this same
** set of columns.  The ORDER BY clause only matches index columns beyond the
** the first nEqCol columns.
**
** All terms of the ORDER BY clause must be either ASC or DESC.  The
** *pbRev value is set to 1 if the ORDER BY clause is all DESC and it is
** set to 0 if the ORDER BY clause is all ASC.
**
** TODO:  If earlier terms of an ORDER BY clause match all terms of a
** UNIQUE index, then subsequent terms of the ORDER BY can be ignored.
** This optimization needs to be implemented.
*/
static Index *findSortingIndex(
  Parse *pParse,          /* Parsing context */
  Table *pTab,            /* The table to be sorted */
  int base,               /* Cursor number for pTab */
  ExprList *pOrderBy,     /* The ORDER BY clause */
  Index *pPreferredIdx,   /* Use this index, if possible and not NULL */
  int nEqCol,             /* Number of index columns used with == constraints */
  int *pbRev              /* Set to 1 if ORDER BY is DESC */
){
  int i, j;                    /* Loop counters */
  Index *pMatch;               /* Best matching index so far */
  Index *pIdx;                 /* Current index */
  int sortOrder;               /* Which direction we are sorting */
  sqlite3 *db = pParse->db;

  assert( pOrderBy!=0 );
  assert( pOrderBy->nExpr>0 );
  assert( pPreferredIdx!=0 || nEqCol==0 );
  sortOrder = pOrderBy->a[0].sortOrder;
  for(i=0; i<pOrderBy->nExpr; i++){
    Expr *p;
    if( pOrderBy->a[i].sortOrder!=sortOrder ){
      /* Indices can only be used if all ORDER BY terms are either
      ** DESC or ASC.  Indices cannot be used on a mixture. */
      return 0;
    }
    p = pOrderBy->a[i].pExpr;
    if( p->op!=TK_COLUMN || p->iTable!=base ){
      /* Can not use an index sort on anything that is not a column in the
      ** left-most table of the FROM clause */
      return 0;
    }
  }

  /* If we get this far, it means the ORDER BY clause consists of columns
  ** that are all either ascending or descending and which refer only to
  ** the left-most table of the FROM clause.  Find the index that is best
  ** used for sorting.
  */
  pMatch = 0;
  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    int nExpr = pOrderBy->nExpr;
    if( pIdx->nColumn < nEqCol || pIdx->nColumn < nExpr ) continue;
    for(i=j=0; i<nEqCol; i++){
      CollSeq *pColl = sqlite3ExprCollSeq(pParse, pOrderBy->a[j].pExpr);
      if( !pColl ) pColl = db->pDfltColl;
      if( pPreferredIdx->aiColumn[i]!=pIdx->aiColumn[i] ) break;
      if( pPreferredIdx->keyInfo.aColl[i]!=pIdx->keyInfo.aColl[i] ) break;
      if( j<nExpr && 
          pOrderBy->a[j].pExpr->iColumn==pIdx->aiColumn[i] &&
          pColl==pIdx->keyInfo.aColl[i]
      ){ 
        j++; 
      }
    }
    if( i<nEqCol ) continue;
    for(i=0; i+j<nExpr; i++){
      CollSeq *pColl = sqlite3ExprCollSeq(pParse, pOrderBy->a[i+j].pExpr);
      if( !pColl ) pColl = db->pDfltColl;
      if( pOrderBy->a[i+j].pExpr->iColumn!=pIdx->aiColumn[i+nEqCol] ||
          pColl!=pIdx->keyInfo.aColl[i+nEqCol] ) break;
    }
    if( i+j>=nExpr ){
      pMatch = pIdx;
      if( pIdx==pPreferredIdx ) break;
    }
  }
  *pbRev = sortOrder==SQLITE_SO_DESC;
  return pMatch;
}

/*
** This routine decides if pIdx can be used to satisfy the ORDER BY
** clause.  If it can, it returns 1.  If pIdx cannot satisfy the
** ORDER BY clause, this routine returns 0.
**
** pOrderBy is an ORDER BY clause from a SELECT statement.  pTab is the
** left-most table in the FROM clause of that same SELECT statement and

    if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
      /* Can not use an index sort on anything that is not a column in the
      ** left-most table of the FROM clause */
      return 0;
    }
    pColl = sqlite3ExprCollSeq(pParse, pExpr);
    if( !pColl ) pColl = db->pDfltColl;
    if( pExpr->iColumn!=pIdx->aiColumn[i] && pColl!=pIdx->keyInfo.aColl[i] ){

      if( i<=nEqCol ){
        /* If an index column that is constrained by == fails to match an
        ** ORDER BY term, that is OK.  Just ignore that column of the index
        */
        continue;
      }else{
        /* If an index column fails to match and is not constrained by ==
        ** then the index cannot satisfy the ORDER BY constraint.

    assert( pX->op==TK_EQ );
    sqlite3ExprCode(pParse, pX->pRight);
  }else{
    int iTab = pX->iTable;
    Vdbe *v = pParse->pVdbe;
    sqlite3VdbeAddOp(v, OP_Rewind, iTab, brk);
    sqlite3VdbeAddOp(v, OP_KeyAsData, iTab, 1);
    pLevel->inP2 = sqlite3VdbeAddOp(v, OP_IdxColumn, iTab, 0);
    pLevel->inOp = OP_Next;
    pLevel->inP1 = iTab;
  }
  disableTerm(pLevel, &pTerm->p);
}

/*

){
  int i;                     /* Loop counter */
  WhereInfo *pWInfo;         /* Will become the return value of this function */
  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
  int brk, cont = 0;         /* Addresses used during code generation */
  int nExpr;           /* Number of subexpressions in the WHERE clause */
  Bitmask loopMask;    /* One bit set for each outer loop */
  int haveKey = 0;     /* True if KEY is on the stack */
  ExprInfo *pTerm;     /* A single term in the WHERE clause; ptr to aExpr[] */
  ExprMaskSet maskSet; /* The expression mask set */
  int iDirectEq[BMS];  /* Term of the form ROWID==X for the N-th table */
  int iDirectLt[BMS];  /* Term of the form ROWID<X or ROWID<=X */
  int iDirectGt[BMS];  /* Term of the form ROWID>X or ROWID>=X */
  ExprInfo aExpr[101]; /* The WHERE clause is divided into these terms */



  /* pushKey is only allowed if there is a single table (as in an INSERT or
  ** UPDATE statement)
  */
  assert( pushKey==0 || pTabList->nSrc==1 );

  /* Split the WHERE clause into separate subexpressions where each

  ** doing a second read of the actual database table.
  **
  ** Actually, if there are more than 32 tables in the join, only the
  ** first 32 tables are candidates for indices.  This is (again) due
  ** to the limit of 32 bits in an integer bitmask.
  */
  loopMask = 0;


  for(i=0; i<pTabList->nSrc && i<ARRAYSIZE(iDirectEq); i++){
    int j;
    WhereLevel *pLevel = &pWInfo->a[i];
    int iCur = pTabList->a[i].iCursor;       /* The cursor for this table */
    Bitmask mask = getMask(&maskSet, iCur);  /* Cursor mask for this table */
    Table *pTab = pTabList->a[i].pTab;
    Index *pIdx;
    Index *pBestIdx = 0;
    int bestScore = 0;
    int bestRev = 0;

    /* Check to see if there is an expression that uses only the
    ** ROWID field of this table.  For terms of the form ROWID==expr
    ** set iDirectEq[i] to the index of the term.  For terms of the
    ** form ROWID<expr or ROWID<=expr set iDirectLt[i] to the term index.
    ** For terms like ROWID>expr or ROWID>=expr set iDirectGt[i].
    **
    ** (Added:) Treat ROWID IN expr like ROWID=expr.
    */
    pLevel->iCur = -1;
    iDirectEq[i] = -1;
    iDirectLt[i] = -1;
    iDirectGt[i] = -1;
    for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
      Expr *pX = pTerm->p;
      if( pTerm->idxLeft==iCur && pX->pLeft->iColumn<0
            && (pTerm->prereqRight & loopMask)==pTerm->prereqRight ){

      m = ((Bitmask)1)<<nEq;
      if( m & ltMask ) score+=4;    /* Increase score for a < constraint */
      if( m & gtMask ) score+=8;    /* Increase score for a > constraint */
      if( score==0 && inMask ) score = 16; /* Default score for IN constraint */

      /* Give bonus points if this index can be used for sorting
      */
      if( i==0 && score>0 && ppOrderBy && *ppOrderBy ){
        int base = pTabList->a[0].iCursor;
        if( isSortingIndex(pParse, pIdx, pTab, base, *ppOrderBy, nEq, &bRev) ){
          score += 2;
        }
      }

















      /* If the score for this index is the best we have seen so far, then
      ** save it
      */
      if( score>bestScore ){
        pBestIdx = pIdx;
        bestScore = score;
        bestRev = bRev;
      }
    }
    pLevel->pIdx = pBestIdx;
    pLevel->score = bestScore;
    pLevel->bRev = bestRev;
    loopMask |= mask;
    if( pBestIdx ){
      pLevel->iCur = pParse->nTab++;
    }
  }

  /* Check to see if the ORDER BY clause is or can be satisfied by the
  ** use of an index on the first table.
  */
  if( ppOrderBy && *ppOrderBy && pTabList->nSrc>0 ){
     Index *pSortIdx = 0;     /* Index that satisfies the ORDER BY clause */
     Index *pIdx;             /* Index derived from the WHERE clause */
     Table *pTab;             /* Left-most table in the FROM clause */
     int bRev = 0;            /* True to reverse the output order */
     int iCur;                /* Btree-cursor that will be used by pTab */
     WhereLevel *pLevel0 = &pWInfo->a[0];

     pTab = pTabList->a[0].pTab;
     pIdx = pLevel0->pIdx;
     iCur = pTabList->a[0].iCursor;
     if( pIdx==0 && sortableByRowid(iCur, *ppOrderBy, &bRev) ){
       /* The ORDER BY clause specifies ROWID order, which is what we
       ** were going to be doing anyway...
       */
       *ppOrderBy = 0;
       pLevel0->bRev = bRev;
     }else if( pLevel0->score==16 ){
       /* If there is already an IN index on the left-most table,
       ** it will not give the correct sort order.
       ** So, pretend that no suitable index is found.
       */
     }else if( iDirectEq[0]>=0 || iDirectLt[0]>=0 || iDirectGt[0]>=0 ){
       /* If the left-most column is accessed using its ROWID, then do
       ** not try to sort by index.  But do delete the ORDER BY clause
       ** if it is redundant.
       */
     }else{
       int nEqCol = (pLevel0->score+16)/32;

       pSortIdx = findSortingIndex(pParse, pTab, iCur, 
                                   *ppOrderBy, pIdx, nEqCol, &bRev);
     }
     if( pSortIdx && (pIdx==0 || pIdx==pSortIdx) ){
       if( pIdx==0 ){
         pLevel0->pIdx = pSortIdx;
         pLevel0->iCur = pParse->nTab++;
       }
       pLevel0->bRev = bRev;
       *ppOrderBy = 0;
     }
  }

  /* Open all tables in the pTabList and all indices used by those tables.

  */
  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */

  for(i=0; i<pTabList->nSrc; i++){
    Table *pTab;
    Index *pIx;


    pTab = pTabList->a[i].pTab;
    if( pTab->isTransient || pTab->pSelect ) continue;

    sqlite3OpenTableForReading(v, pTabList->a[i].iCursor, pTab);
    sqlite3CodeVerifySchema(pParse, pTab->iDb);


    if( (pIx = pWInfo->a[i].pIdx)!=0 ){
      sqlite3VdbeAddOp(v, OP_Integer, pIx->iDb, 0);
      sqlite3VdbeOp3(v, OP_OpenRead, pWInfo->a[i].iCur, pIx->tnum,
                     (char*)&pIx->keyInfo, P3_KEYINFO);
    }



  }




  /* Generate the code to do the search
  */
  loopMask = 0;


  for(i=0; i<pTabList->nSrc; i++){
    int j, k;
    int iCur = pTabList->a[i].iCursor;
    Index *pIdx;


    WhereLevel *pLevel = &pWInfo->a[i];









    /* 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_String8, 0, 0);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
      VdbeComment((v, "# init LEFT JOIN no-match flag"));
    }

    pIdx = pLevel->pIdx;
    pLevel->inOp = OP_Noop;
    if( i<ARRAYSIZE(iDirectEq) && (k = iDirectEq[i])>=0 ){
      /* Case 1:  We can directly reference a single row using an
      **          equality comparison against the ROWID field.  Or
      **          we reference multiple rows using a "rowid IN (...)"
      **          construct.
      */
      assert( k<nExpr );
      pTerm = &aExpr[k];
      assert( pTerm->p!=0 );
      assert( pTerm->idxLeft==iCur );

      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
      codeEqualityTerm(pParse, pTerm, brk, pLevel);
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk);
      haveKey = 0;
      sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk);

      pLevel->op = OP_Noop;
    }else if( pIdx!=0 && pLevel->score>0 && (pLevel->score&0x0c)==0 ){
      /* 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 = (pLevel->score+16)/32;
      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);

      /* 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->bRev ){
        /* Scan in reverse order */
        sqlite3VdbeAddOp(v, OP_MoveLe, pLevel->iCur, brk);
        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, OP_IdxLT, pLevel->iCur, brk);
        pLevel->op = OP_Prev;
      }else{
        /* Scan in the forward order */
        sqlite3VdbeAddOp(v, OP_MoveGe, pLevel->iCur, brk);
        start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeOp3(v, OP_IdxGE, pLevel->iCur, brk, "+", P3_STATIC);
        pLevel->op = OP_Next;
      }
      sqlite3VdbeAddOp(v, OP_RowKey, pLevel->iCur, 0);
      sqlite3VdbeAddOp(v, OP_IdxIsNull, nColumn, cont);
      sqlite3VdbeAddOp(v, OP_IdxRecno, pLevel->iCur, 0);
      if( i==pTabList->nSrc-1 && pushKey ){
        haveKey = 1;
      }else{
        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
        haveKey = 0;
      }
      pLevel->p1 = pLevel->iCur;
      pLevel->p2 = start;
    }else if( i<ARRAYSIZE(iDirectLt) && (iDirectLt[i]>=0 || iDirectGt[i]>=0) ){
      /* Case 3:  We have an inequality comparison against the ROWID field.
      */
      int testOp = OP_Noop;
      int start;
      int bRev = pLevel->bRev;


      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      if( bRev ){
        int t = iDirectGt[i];
        iDirectGt[i] = iDirectLt[i];
        iDirectLt[i] = t;
      }

      pLevel->p1 = iCur;
      pLevel->p2 = start;
      if( testOp!=OP_Noop ){
        sqlite3VdbeAddOp(v, OP_Recno, iCur, 0);
        sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, testOp, 0, brk);
      }
      haveKey = 0;
    }else if( pIdx==0 ){
      /* Case 4:  There is no usable index.  We must do a complete
      **          scan of the entire database table.
      */
      int start;
      int opRewind;


      brk = pLevel->brk = sqlite3VdbeMakeLabel(v);
      cont = pLevel->cont = sqlite3VdbeMakeLabel(v);
      if( pLevel->bRev ){
        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;
      haveKey = 0;
    }else{
      /* Case 5: The WHERE clause term that refers to the right-most
      **         column of the index is an inequality.  For example, if
      **         the index is on (x,y,z) and the WHERE clause is of the
      **         form "x=5 AND y<10" then this case is used.  Only the
      **         right-most column can be an inequality - the rest must
      **         use the "==" operator.

      }
      if( testOp!=OP_Noop ){
        int nCol = nEqColumn + ((score & 4)!=0);
        pLevel->iMem = pParse->nMem++;
        buildIndexProbe(v, nCol, brk, pIdx);
        if( pLevel->bRev ){
          int op = leFlag ? OP_MoveLe : OP_MoveLt;
          sqlite3VdbeAddOp(v, op, pLevel->iCur, brk);
        }else{
          sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
        }
      }else if( pLevel->bRev ){
        sqlite3VdbeAddOp(v, OP_Last, pLevel->iCur, brk);
      }

      /* Generate the start key.  This is the key that defines the lower
      ** bound on the search.  There is no start key if there are no
      ** equality terms and if there is no "X>..." term.  In
      ** that case, generate a "Rewind" instruction in place of the
      ** start key search.

        buildIndexProbe(v, nCol, brk, pIdx);
        if( pLevel->bRev ){
          pLevel->iMem = pParse->nMem++;
          sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1);
          testOp = OP_IdxLT;
        }else{
          int op = geFlag ? OP_MoveGe : OP_MoveGt;
          sqlite3VdbeAddOp(v, op, pLevel->iCur, brk);
        }
      }else if( pLevel->bRev ){
        testOp = OP_Noop;
      }else{
        sqlite3VdbeAddOp(v, OP_Rewind, pLevel->iCur, brk);
      }

      /* Generate the the top of the loop.  If there is a termination
      ** key we have to test for that key and abort at the top of the
      ** loop.
      */
      start = sqlite3VdbeCurrentAddr(v);
      if( testOp!=OP_Noop ){
        sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0);
        sqlite3VdbeAddOp(v, testOp, pLevel->iCur, brk);
        if( (leFlag && !pLevel->bRev) || (!geFlag && pLevel->bRev) ){
          sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC);
        }
      }
      sqlite3VdbeAddOp(v, OP_RowKey, pLevel->iCur, 0);
      sqlite3VdbeAddOp(v, OP_IdxIsNull, nEqColumn + ((score&4)!=0), cont);
      sqlite3VdbeAddOp(v, OP_IdxRecno, pLevel->iCur, 0);
      if( i==pTabList->nSrc-1 && pushKey ){
        haveKey = 1;
      }else{
        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
        haveKey = 0;
      }

      /* Record the instruction used to terminate the loop.
      */
      pLevel->op = pLevel->bRev ? OP_Prev : OP_Next;
      pLevel->p1 = pLevel->iCur;
      pLevel->p2 = start;
    }
    loopMask |= getMask(&maskSet, iCur);

    /* Insert code to test every subexpression that can be completely
    ** computed using the current set of tables.
    */
    for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
      if( pTerm->p==0 ) continue;
      if( (pTerm->prereqAll & loopMask)!=pTerm->prereqAll ) continue;
      if( pLevel->iLeftJoin && !ExprHasProperty(pTerm->p,EP_FromJoin) ){
        continue;
      }
      if( haveKey ){
        haveKey = 0;



        sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);

      }
      sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1);
      pTerm->p = 0;
    }
    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);
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iLeftJoin, 1);
      VdbeComment((v, "# record LEFT JOIN hit"));
      for(pTerm=aExpr, j=0; j<nExpr; j++, pTerm++){
        if( pTerm->p==0 ) continue;
        if( (pTerm->prereqAll & loopMask)!=pTerm->prereqAll ) continue;
        if( haveKey ){
          /* Cannot happen.  "haveKey" can only be true if pushKey is true
          ** an pushKey can only be true for DELETE and UPDATE and there are
          ** no outer joins with DELETE and UPDATE.
          */

          haveKey = 0;
          sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
        }
        sqlite3ExprIfFalse(pParse, pTerm->p, cont, 1);
        pTerm->p = 0;
      }
    }
  }









  pWInfo->iContinue = cont;
  if( pushKey && !haveKey ){
    sqlite3VdbeAddOp(v, OP_Recno, pTabList->a[0].iCursor, 0);
  }
  freeMaskSet(&maskSet);
  return pWInfo;
}

/*
** Generate the end of the WHERE loop.  See comments on 
** sqlite3WhereBegin() for additional information.
*/
void sqlite3WhereEnd(WhereInfo *pWInfo){
  Vdbe *v = pWInfo->pParse->pVdbe;
  int i;
  WhereLevel *pLevel;
  SrcList *pTabList = pWInfo->pTabList;




  for(i=pTabList->nSrc-1; i>=0; i--){
    pLevel = &pWInfo->a[i];
    sqlite3VdbeResolveLabel(v, pLevel->cont);
    if( pLevel->op!=OP_Noop ){
      sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2);
    }
    sqlite3VdbeResolveLabel(v, pLevel->brk);
    if( pLevel->inOp!=OP_Noop ){
      sqlite3VdbeAddOp(v, pLevel->inOp, pLevel->inP1, pLevel->inP2);
    }
    if( pLevel->iLeftJoin ){
      int addr;
      addr = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iLeftJoin, 0);
      sqlite3VdbeAddOp(v, OP_NotNull, 1, addr+4 + (pLevel->iCur>=0));
      sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0);
      if( pLevel->iCur>=0 ){
        sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iCur, 0);
      }
      sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top);
    }
  }




  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);





  for(i=0; i<pTabList->nSrc; i++){
    Table *pTab = pTabList->a[i].pTab;
    assert( pTab!=0 );
    if( pTab->isTransient || pTab->pSelect ) continue;
    pLevel = &pWInfo->a[i];
    sqlite3VdbeAddOp(v, OP_Close, pTabList->a[i].iCursor, 0);

    if( pLevel->pIdx!=0 ){
      sqlite3VdbeAddOp(v, OP_Close, pLevel->iCur, 0);
    }
  }





































  sqliteFree(pWInfo);
  return;
}

#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this script is page cache subsystem.
#
# $Id: collate4.test,v 1.5 2004/11/22 19:12:21 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

db collate TEXT text_collate
proc text_collate {a b} {
  return [string compare $a $b]

do_test collate4-2.1.2 {
  execsql {
    CREATE INDEX collate4i1 ON collate4t1(a);
  }
  count {
    SELECT * FROM collate4t2, collate4t1 WHERE a = b;
  }
} {A a A A 7}
do_test collate4-2.1.3 {
  count {
    SELECT * FROM collate4t2, collate4t1 WHERE b = a;
  }
} {A A 19}
do_test collate4-2.1.4 {
  execsql {
    DROP INDEX collate4i1;
    CREATE INDEX collate4i1 ON collate4t1(a COLLATE TEXT);
  }
  count {
    SELECT * FROM collate4t2, collate4t1 WHERE a = b;
  }
} {A a A A 19}
do_test collate4-2.1.5 {
  count {
    SELECT * FROM collate4t2, collate4t1 WHERE b = a;
  }
} {A A 5}
do_test collate4-2.1.6 {
  count {
    SELECT a FROM collate4t1 WHERE a IN (SELECT * FROM collate4t2);
  }
} {a A 10}
do_test collate4-2.1.7 {
  execsql {
    DROP INDEX collate4i1;
    CREATE INDEX collate4i1 ON collate4t1(a);
  }
  count {
    SELECT a FROM collate4t1 WHERE a IN (SELECT * FROM collate4t2);
  }
} {a A 8}
do_test collate4-2.1.8 {
  count {
    SELECT a FROM collate4t1 WHERE a IN ('z', 'a');
  }
} {a A 7}
do_test collate4-2.1.9 {
  execsql {
    DROP INDEX collate4i1;
    CREATE INDEX collate4i1 ON collate4t1(a COLLATE TEXT);
  }
  count {
    SELECT a FROM collate4t1 WHERE a IN ('z', 'a');

  }
} {}
do_test collate4-2.2.1 {
  count {
    SELECT * FROM collate4t2 NATURAL JOIN collate4t1;
  }
} {0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 63}
do_test collate4-2.2.1 {
  execsql {
    CREATE INDEX collate4i1 ON collate4t1(a, b, c);
  }
  count {
    SELECT * FROM collate4t2 NATURAL JOIN collate4t1;
  }
} {0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 45}
do_test collate4-2.2.2 {
  execsql {
    DROP INDEX collate4i1;
    CREATE INDEX collate4i1 ON collate4t1(a, b, c COLLATE text);
  }
  count {
    SELECT * FROM collate4t2 NATURAL JOIN collate4t1;

# 2001 September 15
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing the use of indices in WHERE clases.
#
# $Id: where.test,v 1.25 2004/12/18 18:40:28 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# Build some test data
#
do_test where-1.0 {

do_test where-1.29 {
  count {SELECT w FROM t1 WHERE y==121}
} {10 99}


do_test where-1.30 {
  count {SELECT w FROM t1 WHERE w>97}
} {98 99 100 6}
do_test where-1.31 {
  count {SELECT w FROM t1 WHERE w>=97}
} {97 98 99 100 8}
do_test where-1.33 {
  count {SELECT w FROM t1 WHERE w==97}
} {97 3}
do_test where-1.34 {
  count {SELECT w FROM t1 WHERE w+1==98}
} {97 99}
do_test where-1.35 {
  count {SELECT w FROM t1 WHERE w<3}
} {1 2 4}
do_test where-1.36 {
  count {SELECT w FROM t1 WHERE w<=3}
} {1 2 3 6}
do_test where-1.37 {
  count {SELECT w FROM t1 WHERE w+1<=4 ORDER BY w}
} {1 2 3 199}

do_test where-1.38 {
  count {SELECT (w) FROM t1 WHERE (w)>(97)}
} {98 99 100 6}
do_test where-1.39 {
  count {SELECT (w) FROM t1 WHERE (w)>=(97)}
} {97 98 99 100 8}
do_test where-1.40 {
  count {SELECT (w) FROM t1 WHERE (w)==(97)}
} {97 3}
do_test where-1.41 {
  count {SELECT (w) FROM t1 WHERE ((w)+(1))==(98)}
} {97 99}


# Do the same kind of thing except use a join as the data source.
#

# Lets do a 3-way join.
#
do_test where-3.1 {
  count {
    SELECT A.w, B.p, C.w FROM t1 as A, t2 as B, t1 as C
    WHERE C.w=101-B.p AND B.r=10202-A.y AND A.w=11
  }
} {11 90 11 9}
do_test where-3.2 {
  count {
    SELECT A.w, B.p, C.w FROM t1 as A, t2 as B, t1 as C
    WHERE C.w=101-B.p AND B.r=10202-A.y AND A.w=12
  }
} {12 89 12 9}
do_test where-3.3 {
  count {
    SELECT A.w, B.p, C.w FROM t1 as A, t2 as B, t1 as C
    WHERE A.w=15 AND B.p=C.w AND B.r=10202-A.y
  }
} {15 86 86 9}

# Test to see that the special case of a constant WHERE clause is
# handled.
#
do_test where-4.1 {
  count {
    SELECT * FROM t1 WHERE 0

    SELECT * FROM t3 WHERE b>0 ORDER BY a LIMIT 3
  }
} {1 100 4 2 99 9 3 98 16 sort}
do_test where-6.8 {
  cksort {
    SELECT * FROM t3 WHERE a IN (3,5,7,1,9,4,2) ORDER BY a LIMIT 3
  }
} {1 100 4 2 99 9 3 98 16 nosort}
do_test where-6.9.1 {
  cksort {
    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY a LIMIT 3
  }
} {1 100 4 nosort}
do_test where-6.9.2 {
  cksort {

    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY c,a LIMIT 3
  }
} {1 100 4 sort}
do_test where-6.9.8 {
  cksort {
    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY a DESC, c ASC LIMIT 3
  }
} {1 100 4 sort}
do_test where-6.9.9 {
  cksort {
    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY a ASC, c DESC LIMIT 3
  }
} {1 100 4 sort}
do_test where-6.10 {
  cksort {
    SELECT * FROM t3 WHERE a=1 AND c>0 ORDER BY a LIMIT 3
  }
} {1 100 4 nosort}
do_test where-6.11 {
  cksort {