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Overview
| Comment: | Small tweaks to the query planner to get it to try harder to use an index for sorting and to avoid using automatic indexes on constant terms. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | branch-3.8.3 |
| Files: | files | file ages | folders |
| SHA1: |
2d9de154f8f398d66693a4bc35eef135 |
| User & Date: | drh 2014-06-17 15:13:04 |
Context
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2014-06-17
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| 15:13 | Small tweaks to the query planner to get it to try harder to use an index for sorting and to avoid using automatic indexes on constant terms. (Leaf check-in: 2d9de154 user: drh tags: branch-3.8.3) | |
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2014-02-11
| ||
| 14:52 | Version 3.8.3.1 (check-in: ea3317a4 user: drh tags: release, version-3.8.3.1, branch-3.8.3) | |
Changes
Changes to src/where.c.
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&& !pSrc->isRecursive
){
/* Generate auto-index WhereLoops */
WhereTerm *pTerm;
WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
if( pTerm->prereqRight & pNew->maskSelf ) continue;
if( termCanDriveIndex(pTerm, pSrc, 0) ){
pNew->u.btree.nEq = 1;
pNew->u.btree.nSkip = 0;
pNew->u.btree.pIndex = 0;
pNew->nLTerm = 1;
pNew->aLTerm[0] = pTerm;
/* TUNING: One-time cost for computing the automatic index is
................................................................................
if( pWInfo->pOrderBy==0 || nRowEst==0 ){
aFrom[0].isOrderedValid = 1;
}else{
/* TUNING: Estimated cost of sorting is 48*N*log2(N) where N is the
** number of output rows. The 48 is the expected size of a row to sort.
** FIXME: compute a better estimate of the 48 multiplier based on the
** result set expressions. */
rSortCost = nRowEst + estLog(nRowEst);
WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
}
/* Compute successively longer WherePaths using the previous generation
** of WherePaths as the basis for the next. Keep track of the mxChoice
** best paths at each generation */
for(iLoop=0; iLoop<nLoop; iLoop++){
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>
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&& !pSrc->isRecursive
){
/* Generate auto-index WhereLoops */
WhereTerm *pTerm;
WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
if( pTerm->prereqRight & pNew->maskSelf ) continue;
if( sqlite3ExprIsConstant(pTerm->pExpr->pRight) ) continue;
if( termCanDriveIndex(pTerm, pSrc, 0) ){
pNew->u.btree.nEq = 1;
pNew->u.btree.nSkip = 0;
pNew->u.btree.pIndex = 0;
pNew->nLTerm = 1;
pNew->aLTerm[0] = pTerm;
/* TUNING: One-time cost for computing the automatic index is
................................................................................
if( pWInfo->pOrderBy==0 || nRowEst==0 ){
aFrom[0].isOrderedValid = 1;
}else{
/* TUNING: Estimated cost of sorting is 48*N*log2(N) where N is the
** number of output rows. The 48 is the expected size of a row to sort.
** FIXME: compute a better estimate of the 48 multiplier based on the
** result set expressions. */
rSortCost = nRowEst + estLog(nRowEst) + 10;
WHERETRACE(0x002,("---- sort cost=%-3d\n", rSortCost));
}
/* Compute successively longer WherePaths using the previous generation
** of WherePaths as the basis for the next. Keep track of the mxChoice
** best paths at each generation */
for(iLoop=0; iLoop<nLoop; iLoop++){
|