diff options
author | drh <> | 2025-01-15 20:23:22 +0000 |
---|---|---|
committer | drh <> | 2025-01-15 20:23:22 +0000 |
commit | d1047faad681aca6c1ceea052f027c91fb75cabe (patch) | |
tree | d77ec101c4bc3b8075811fcf16615ac8bd13daa8 /src | |
parent | 874b5e9fbb22231b283ec5a56921fa9b418c5c8d (diff) | |
download | sqlite-d1047faad681aca6c1ceea052f027c91fb75cabe.tar.gz sqlite-d1047faad681aca6c1ceea052f027c91fb75cabe.zip |
When choosing between two indexes with the same cost, pick the one with the
smaller predicted number of bytes per row.
FossilOrigin-Name: d4bd0d4214551f88f248698fefc821575b722ce5c194d0b3796f572e4704f641
Diffstat (limited to 'src')
-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 ){ |