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Overview
Comment:Fix another problem with the LIKE optimization.
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Timelines: family | ancestors | descendants | both | like-opt-fix
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SHA1: 465bfc72d252f94778248253142faeba78ceea02
User & Date: drh 2015-03-07 20:32:49
Context
2015-03-09
12:11
Always use LIKE optimization range constraints in pairs. Closed-Leaf check-in: 0e02dc94 user: drh tags: like-opt-fix
2015-03-07
20:32
Fix another problem with the LIKE optimization. check-in: 465bfc72 user: drh tags: like-opt-fix
13:56
Fix the LIKE optimization so that it finds BLOB entries in addition to text entries. Ticket [05f43be8fdda9f]. check-in: 74cb0b03 user: drh tags: trunk
Changes
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Changes to src/where.c.

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** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
** scan loop run twice, once for strings and a second time for BLOBs.
** The OP_String opcodes on the second pass convert the upper and lower
** bound string contants to blobs.  This routine makes the necessary changes
** to the OP_String opcodes for that to happen.
*/
static void whereLikeOptimizationStringFixup(Vdbe *v, WhereLevel *pLevel){
  VdbeOp *pOp;




  pOp = sqlite3VdbeGetOp(v, -1);
  if( pLevel->iLikeRepCntr && pOp->opcode==OP_String8 ){
    pOp->p3 = pLevel->iLikeRepCntr;
    pOp->p5 = 1;
  }
}


/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
................................................................................
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
      pRangeStart = pLoop->aLTerm[j++];
      nExtraReg = 1;
    }
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
      pRangeEnd = pLoop->aLTerm[j++];
      nExtraReg = 1;
      if( pRangeStart
       && (pRangeStart->wtFlags & TERM_LIKEOPT)!=0
       && (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0
      ){
        pLevel->iLikeRepCntr = ++pParse->nMem;
        testcase( bRev );
        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
        sqlite3VdbeAddOp2(v, OP_Integer,
                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
                          pLevel->iLikeRepCntr);
................................................................................
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel);
      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
................................................................................
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel);
      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE







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** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
** scan loop run twice, once for strings and a second time for BLOBs.
** The OP_String opcodes on the second pass convert the upper and lower
** bound string contants to blobs.  This routine makes the necessary changes
** to the OP_String opcodes for that to happen.
*/
static void whereLikeOptimizationStringFixup(
  Vdbe *v,                /* prepared statement under construction */
  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
  WhereTerm *pTerm        /* The upper or lower bound just coded */
){
  if( pTerm->wtFlags & TERM_LIKEOPT ){
    VdbeOp *pOp = sqlite3VdbeGetOp(v, -1);
    if( pLevel->iLikeRepCntr && pOp->opcode==OP_String8 ){
      pOp->p3 = pLevel->iLikeRepCntr;
      pOp->p5 = 1;
    }
  }
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
................................................................................
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
      pRangeStart = pLoop->aLTerm[j++];
      nExtraReg = 1;
    }
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
      pRangeEnd = pLoop->aLTerm[j++];
      nExtraReg = 1;

      if( (pRangeStart && (pRangeStart->wtFlags & TERM_LIKEOPT)!=0)
       || (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0
      ){
        pLevel->iLikeRepCntr = ++pParse->nMem;
        testcase( bRev );
        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
        sqlite3VdbeAddOp2(v, OP_Integer,
                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
                          pLevel->iLikeRepCntr);
................................................................................
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
................................................................................
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE