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Overview
| Comment: | Add comments identifing where the skip-scan option is decided in the query planner, to aid in tuning that decision. No changes to code. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
e9df04cec48bb8b4ea26ec9024a22ea4 |
| User & Date: | drh 2013-11-18 19:32:15 |
Context
|
2013-11-19
| ||
| 00:31 | Fix an requirement mark in a test script so that it matches the typo-corrected requirement. No changes to code. check-in: 072412d5 user: drh tags: trunk | |
|
2013-11-18
| ||
| 19:32 | Add comments identifing where the skip-scan option is decided in the query planner, to aid in tuning that decision. No changes to code. check-in: e9df04ce user: drh tags: trunk | |
| 18:48 | Fix documentation typos. No changes to code. check-in: 7caeb09c user: drh tags: trunk | |
Changes
Changes to src/where.c.
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saved_nSkip = pNew->u.btree.nSkip;
saved_nLTerm = pNew->nLTerm;
saved_wsFlags = pNew->wsFlags;
saved_prereq = pNew->prereq;
saved_nOut = pNew->nOut;
pNew->rSetup = 0;
rLogSize = estLog(sqlite3LogEst(pProbe->aiRowEst[0]));
if( pTerm==0
&& saved_nEq==saved_nSkip
&& saved_nEq+1<pProbe->nKeyCol
&& pProbe->aiRowEst[saved_nEq+1]>50
){
LogEst nIter;
pNew->u.btree.nEq++;
pNew->u.btree.nSkip++;
pNew->aLTerm[pNew->nLTerm++] = 0;
pNew->wsFlags |= WHERE_SKIPSCAN;
nIter = sqlite3LogEst(pProbe->aiRowEst[0]/pProbe->aiRowEst[saved_nEq+1]);
|
> > > > > | |
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saved_nSkip = pNew->u.btree.nSkip; saved_nLTerm = pNew->nLTerm; saved_wsFlags = pNew->wsFlags; saved_prereq = pNew->prereq; saved_nOut = pNew->nOut; pNew->rSetup = 0; rLogSize = estLog(sqlite3LogEst(pProbe->aiRowEst[0])); /* Consider using a skip-scan if there are no WHERE clause constraints ** available for the left-most terms of the index, and if the average ** number of repeats in the left-most terms is at least 50. */ if( pTerm==0 && saved_nEq==saved_nSkip && saved_nEq+1<pProbe->nKeyCol && pProbe->aiRowEst[saved_nEq+1]>50 /* TUNING: Minimum for skip-scan */ ){ LogEst nIter; pNew->u.btree.nEq++; pNew->u.btree.nSkip++; pNew->aLTerm[pNew->nLTerm++] = 0; pNew->wsFlags |= WHERE_SKIPSCAN; nIter = sqlite3LogEst(pProbe->aiRowEst[0]/pProbe->aiRowEst[saved_nEq+1]); |