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Overview
| Comment: | Modify internal function whereLoopAdjustCost() so that it does not prefer a skip-scan over a regular index scan even if the regular scan uses a subset of the WHERE terms used by the skip-scan. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | experimental-costs |
| Files: | files | file ages | folders |
| SHA1: |
88a5758dcce891eb7be15432ebdc9f80 |
| User & Date: | dan 2014-04-28 09:35:31.541 |
Context
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2014-04-28
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| 10:00 | Update test script analyze3.test to account for the fact that SQLite now prefers a full-table scan over a non-covering index scan that visits a large percentage of the table rows. (check-in: 35f46a55d8 user: dan tags: experimental-costs) | |
| 09:35 | Modify internal function whereLoopAdjustCost() so that it does not prefer a skip-scan over a regular index scan even if the regular scan uses a subset of the WHERE terms used by the skip-scan. (check-in: 88a5758dcc user: dan tags: experimental-costs) | |
| 08:49 | Fix an error in estimating of the number of rows visited by a range scan. (check-in: d491de62fc user: dan tags: experimental-costs) | |
Changes
Changes to src/where.c.
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**
** To say "WhereLoop X is a proper subset of Y" means that X uses fewer
** WHERE clause terms than Y and that every WHERE clause term used by X is
** also used by Y.
*/
static void whereLoopAdjustCost(const WhereLoop *p, WhereLoop *pTemplate){
if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
for(; p; p=p->pNextLoop){
if( p->iTab!=pTemplate->iTab ) continue;
if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
if( whereLoopCheaperProperSubset(p, pTemplate) ){
/* Adjust pTemplate cost downward so that it is cheaper than its
** subset p */
pTemplate->rRun = p->rRun;
pTemplate->nOut = p->nOut - 1;
}else if( whereLoopCheaperProperSubset(pTemplate, p) ){
/* Adjust pTemplate cost upward so that it is costlier than p since
| > > | 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 |
**
** To say "WhereLoop X is a proper subset of Y" means that X uses fewer
** WHERE clause terms than Y and that every WHERE clause term used by X is
** also used by Y.
*/
static void whereLoopAdjustCost(const WhereLoop *p, WhereLoop *pTemplate){
if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
if( (pTemplate->wsFlags & WHERE_SKIPSCAN)!=0 ) return;
for(; p; p=p->pNextLoop){
if( p->iTab!=pTemplate->iTab ) continue;
if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
if( (p->wsFlags & WHERE_SKIPSCAN)!=0 ) continue;
if( whereLoopCheaperProperSubset(p, pTemplate) ){
/* Adjust pTemplate cost downward so that it is cheaper than its
** subset p */
pTemplate->rRun = p->rRun;
pTemplate->nOut = p->nOut - 1;
}else if( whereLoopCheaperProperSubset(pTemplate, p) ){
/* Adjust pTemplate cost upward so that it is costlier than p since
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