diff options
Diffstat (limited to 'src/where.c')
| -rw-r--r-- | src/where.c | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/src/where.c b/src/where.c index 25b64bcaa..05dab8fdd 100644 --- a/src/where.c +++ b/src/where.c @@ -5491,6 +5491,28 @@ static int computeMxChoice(WhereInfo *pWInfo, LogEst nRowEst){ } /* +** Two WhereLoop objects, pCandidate and pBaseline, are known to have the +** same cost. Look deep into each to see if pCandidate is even slightly +** better than pBaseline. Return false if it is, if pCandidate is is preferred. +** Return true if pBaseline is preferred or if we cannot tell the difference. +** +** Result Meaning +** -------- ---------------------------------------------------------- +** true We cannot tell the difference in pCandidate and pBaseline +** false pCandidate seems like a better choice than pBaseline +*/ +static SQLITE_NOINLINE int whereLoopIsNoBetter( + const WhereLoop *pCandidate, + const WhereLoop *pBaseline +){ + if( (pCandidate->wsFlags & WHERE_INDEXED)==0 ) return 1; + if( (pBaseline->wsFlags & WHERE_INDEXED)==0 ) return 1; + if( pCandidate->u.btree.pIndex->szIdxRow < + pBaseline->u.btree.pIndex->szIdxRow ) return 0; + return 1; +} + +/* ** Given the list of WhereLoop objects at pWInfo->pLoops, this routine ** attempts to find the lowest cost path that visits each WhereLoop ** once. This path is then loaded into the pWInfo->a[].pWLoop fields. @@ -5728,7 +5750,9 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){ */ if( (pTo->rCost<rCost) || (pTo->rCost==rCost && pTo->nRow<nOut) - || (pTo->rCost==rCost && pTo->nRow==nOut && pTo->rUnsort<=rUnsort) + || (pTo->rCost==rCost && pTo->nRow==nOut && pTo->rUnsort<rUnsort) + || (pTo->rCost==rCost && pTo->nRow==nOut && pTo->rUnsort==rUnsort + && whereLoopIsNoBetter(pWLoop, pTo->aLoop[iLoop]) ) ){ #ifdef WHERETRACE_ENABLED /* 0x4 */ if( sqlite3WhereTrace&0x4 ){ |