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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. |
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| 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
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2013-11-19
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| 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 | |
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2013-11-18
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| 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.
3914 3914 saved_nSkip = pNew->u.btree.nSkip; 3915 3915 saved_nLTerm = pNew->nLTerm; 3916 3916 saved_wsFlags = pNew->wsFlags; 3917 3917 saved_prereq = pNew->prereq; 3918 3918 saved_nOut = pNew->nOut; 3919 3919 pNew->rSetup = 0; 3920 3920 rLogSize = estLog(sqlite3LogEst(pProbe->aiRowEst[0])); 3921 + 3922 + /* Consider using a skip-scan if there are no WHERE clause constraints 3923 + ** available for the left-most terms of the index, and if the average 3924 + ** number of repeats in the left-most terms is at least 50. 3925 + */ 3921 3926 if( pTerm==0 3922 3927 && saved_nEq==saved_nSkip 3923 3928 && saved_nEq+1<pProbe->nKeyCol 3924 - && pProbe->aiRowEst[saved_nEq+1]>50 3929 + && pProbe->aiRowEst[saved_nEq+1]>50 /* TUNING: Minimum for skip-scan */ 3925 3930 ){ 3926 3931 LogEst nIter; 3927 3932 pNew->u.btree.nEq++; 3928 3933 pNew->u.btree.nSkip++; 3929 3934 pNew->aLTerm[pNew->nLTerm++] = 0; 3930 3935 pNew->wsFlags |= WHERE_SKIPSCAN; 3931 3936 nIter = sqlite3LogEst(pProbe->aiRowEst[0]/pProbe->aiRowEst[saved_nEq+1]);