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Overview
| Comment: | Fix a problem in the result set size estimation logic of the query planner - a problem introduced by the two previous changes. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | wal |
| Files: | files | file ages | folders |
| SHA1: |
33b1f584ef712625c4df8e2aefe895fa |
| User & Date: | drh 2010-04-15 12:36:07 |
References
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2010-04-15
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| 13:29 | The query planner fix of check-in [33b1f584ef] should have been on the trunk. check-in: f538d759 user: drh tags: trunk | |
Context
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2010-04-15
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| 13:33 | Merge two leaves on the WAL branch. check-in: c9ed66cc user: dan tags: wal | |
| 12:36 | Fix a problem in the result set size estimation logic of the query planner - a problem introduced by the two previous changes. check-in: 33b1f584 user: drh tags: wal | |
| 02:37 | Bring over the recent query planner enhancements from the trunk. check-in: 82969f27 user: drh tags: wal | |
Changes
Changes to src/where.c.
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/* If there are additional constraints on this table that cannot
** be used with the current index, but which might lower the number
** of output rows, adjust the nRow value accordingly. This only
** matters if the current index is the least costly, so do not bother
** with this step if we already know this index will not be chosen.
** Also, never reduce the output row count below 2 using this step.
*/
if( nRow>2 && cost<=pCost->rCost ){
int k;
int nSkipEq = nEq;
int nSkipRange = nBound;
Bitmask thisTab = getMask(pWC->pMaskSet, iCur);
for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
if( (pTerm->prereqAll & notReady)!=thisTab ) continue;
if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
if( nSkipEq ){
/* Ignore the first nEq equality matches since the index
** has already accounted for these */
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> > > > > > > > > | < > | | > > | |
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/* If there are additional constraints on this table that cannot
** be used with the current index, but which might lower the number
** of output rows, adjust the nRow value accordingly. This only
** matters if the current index is the least costly, so do not bother
** with this step if we already know this index will not be chosen.
** Also, never reduce the output row count below 2 using this step.
**
** Do not reduce the output row count if pSrc is the only table that
** is notReady; if notReady is a power of two. This will be the case
** when the main sqlite3WhereBegin() loop is scanning for a table with
** and "optimal" index, and on such a scan the output row count
** reduction is not valid because it does not update the "pCost->used"
** bitmap. The notReady bitmap will also be a power of two when we
** are scanning for the last table in a 64-way join. We are willing
** to bypass this optimization in that corner case.
*/
if( nRow>2 && cost<=pCost->rCost && (notReady & (notReady-1))!=0 ){
int k; /* Loop counter */
int nSkipEq = nEq; /* Number of == constraints to skip */
int nSkipRange = nBound; /* Number of < constraints to skip */
Bitmask thisTab; /* Bitmap for pSrc */
thisTab = getMask(pWC->pMaskSet, iCur);
for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
if( (pTerm->prereqAll & notReady)!=thisTab ) continue;
if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
if( nSkipEq ){
/* Ignore the first nEq equality matches since the index
** has already accounted for these */
|