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Improvements to the way the LIKE optimization is implemented, resulting in

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slightly smaller and faster code that is easier to test.

FossilOrigin-Name: 54c63b329288729031f45b7778752552cd90e226
This commit is contained in:
drh
2016-05-02 10:25:42 +00:00
parent 40cf36ff17
commit 44aebff246
6 changed files with 43 additions and 52 deletions
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36
src/wherecode.c
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@@ -560,9 +560,10 @@ static int codeAllEqualityTerms(
#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
/*
** If the most recently coded instruction is a constant range contraint
** that originated from the LIKE optimization, then change the P3 to be
** pLoop->iLikeRepCntr and set P5.
** If the most recently coded instruction is a constant range constraint
** (a string literal) that originated from the LIKE optimization, then
** set P3 and P5 on the OP_String opcode so that the string will be cast
** to a BLOB at appropriate times.
**
** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'". But this requires that the range
@@ -587,8 +588,8 @@ static void whereLikeOptimizationStringFixup(
assert( pOp!=0 );
assert( pOp->opcode==OP_String8
|| pTerm->pWC->pWInfo->pParse->db->mallocFailed );
pOp->p3 = pLevel->iLikeRepCntr;
pOp->p5 = 1;
pOp->p3 = (int)(pLevel->iLikeRepCntr>>1); /* Register holding counter */
pOp->p5 = (u8)(pLevel->iLikeRepCntr&1); /* ASC or DESC */
}
}
#else
@@ -1175,14 +1176,17 @@ Bitmask sqlite3WhereCodeOneLoopStart(
if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
assert( pRangeStart!=0 ); /* LIKE opt constraints */
assert( pRangeStart->wtFlags & TERM_LIKEOPT ); /* occur in pairs */
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);
pLevel->iLikeRepCntr = (u32)++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Integer, 1, (int)pLevel->iLikeRepCntr);
VdbeComment((v, "LIKE loop counter"));
pLevel->addrLikeRep = sqlite3VdbeCurrentAddr(v);
/* iLikeRepCntr actually stores 2x the counter register number. The
** bottom bit indicates whether the search order is ASC or DESC. */
testcase( bRev );
testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
assert( (bRev & ~1)==0 );
pLevel->iLikeRepCntr <<=1;
pLevel->iLikeRepCntr |= bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC);
}
#endif
if( pRangeStart==0
@@ -1696,11 +1700,17 @@ Bitmask sqlite3WhereCodeOneLoopStart(
continue;
}
if( pTerm->wtFlags & TERM_LIKECOND ){
/* If the TERM_LIKECOND flag is set, that means that the range search
** is sufficient to guarantee that the LIKE operator is true, so we
** can skip the call to the like(A,B) function. But this only works
** for strings. So do not skip the call to the function on the pass
** that compares BLOBs. */
#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
continue;
#else
assert( pLevel->iLikeRepCntr>0 );
skipLikeAddr = sqlite3VdbeAddOp1(v, OP_IfNot, pLevel->iLikeRepCntr);
u32 x = pLevel->iLikeRepCntr;
assert( x>0 );
skipLikeAddr = sqlite3VdbeAddOp1(v, (x&1)? OP_IfNot : OP_If, (int)(x>>1));
VdbeCoverage(v);
#endif
}