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Overview
| Comment: | Clean up the proper-subset cost adjustment logic to make it more compact and easier to read and so that full branch test coverage is more easily obtained. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
9a5d38c79d2482a23bcfbc3ff35ca4fa |
| User & Date: | drh 2014-04-18 22:20:31.054 |
Context
|
2014-04-21
| ||
| 13:21 | Avoid discarding an ORDER BY clause in the case where an identical GROUP BY clauses uses an index to group, but not sort, the rows. Fix for [b75a9ca6b0]. (check-in: de9a490f59 user: dan tags: trunk) | |
|
2014-04-18
| ||
| 22:20 | Clean up the proper-subset cost adjustment logic to make it more compact and easier to read and so that full branch test coverage is more easily obtained. (check-in: 9a5d38c79d user: drh tags: trunk) | |
| 00:49 | Add the SQLITE_RUNTIME_BYTEORDER compile-time option to force SQLite to check the processor byte-order at run-time. Add additional compile-time byte order checks for ARM, PPC, and SPARC. (check-in: 2c5363873a user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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whereLoopDelete(db, p);
}
sqlite3DbFree(db, pWInfo);
}
}
/*
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whereLoopDelete(db, p);
}
sqlite3DbFree(db, pWInfo);
}
}
/*
** Return TRUE if both of the following are true:
**
** (1) X has the same or lower cost that Y
** (2) X is a proper subset of Y
**
** By "proper subset" we mean that X uses fewer WHERE clause terms
** than Y and that every WHERE clause term used by X is also used
** by Y.
**
** If X is a proper subset of Y then Y is a better choice and ought
** to have a lower cost. This routine returns TRUE when that cost
** relationship is inverted and needs to be adjusted.
*/
static int whereLoopCheaperProperSubset(
const WhereLoop *pX, /* First WhereLoop to compare */
const WhereLoop *pY /* Compare against this WhereLoop */
){
int i, j;
if( pX->nLTerm >= pY->nLTerm ) return 0; /* X is not a subset of Y */
if( pX->rRun >= pY->rRun ){
if( pX->rRun > pY->rRun ) return 0; /* X costs more than Y */
if( pX->nOut > pY->nOut ) return 0; /* X costs more than Y */
}
for(j=0, i=pX->nLTerm-1; i>=0; i--){
for(j=pY->nLTerm-1; j>=0; j--){
if( pY->aLTerm[j]==pX->aLTerm[i] ) break;
}
if( j<0 ) return 0; /* X not a subset of Y since term X[i] not used by Y */
}
return 1; /* All conditions meet */
}
/*
** Try to adjust the cost of WhereLoop pTemplate upwards or downwards so
** that:
**
** (1) pTemplate costs less than any other WhereLoops that are a proper
|
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** 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;
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** 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
** pTemplate is a proper subset of p */
pTemplate->rRun = p->rRun;
pTemplate->nOut = p->nOut + 1;
}
}
}
/*
|
| ︙ | ︙ |