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Overview
| Comment: | Disable the table selection rule that tried to prevent full table scans from migrating to the outer loop unless they were optimal. The new scaling of outer-loop costs by cost of inner loops obviates the need for that step. And, in fact, that step causes problems with the new inner-loop cost accounting. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | inner-loop-cost |
| Files: | files | file ages | folders |
| SHA1: |
51bfd63b7f9fe53831570ad124c932cb |
| User & Date: | drh 2012-11-09 18:22:26.026 |
Context
|
2012-11-09
| ||
| 18:32 | Take into account the cost of inner loops when selecting which table of a join to use for the next outer loop. (check-in: 3f87f4593b user: drh tags: trunk) | |
| 18:22 | Disable the table selection rule that tried to prevent full table scans from migrating to the outer loop unless they were optimal. The new scaling of outer-loop costs by cost of inner loops obviates the need for that step. And, in fact, that step causes problems with the new inner-loop cost accounting. (Closed-Leaf check-in: 51bfd63b7f user: drh tags: inner-loop-cost) | |
| 17:59 | Try to take into account the cost of inner loops when selecting which table of a join to use for the outer loop. (check-in: 942556342a user: drh tags: inner-loop-cost) | |
Changes
Changes to src/where.c.
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}
}
whereClauseClear(pWInfo->pWC);
sqlite3DbFree(db, pWInfo);
}
}
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}
}
whereClauseClear(pWInfo->pWC);
sqlite3DbFree(db, pWInfo);
}
}
/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
** information needed to terminate the loop. Later, the calling routine
** should invoke sqlite3WhereEnd() with the return value of this function
** in order to complete the WHERE clause processing.
|
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/* Conditions under which this table becomes the best so far:
**
** (1) The table must not depend on other tables that have not
** yet run. (In other words, it must not depend on tables
** in inner loops.)
**
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/* Conditions under which this table becomes the best so far:
**
** (1) The table must not depend on other tables that have not
** yet run. (In other words, it must not depend on tables
** in inner loops.)
**
** (2) (This rule was removed on 2012-11-09. The scaling of the
** cost using the optimal scan cost made this rule obsolete.)
**
** (3) All tables have an INDEXED BY clause or this table lacks an
** INDEXED BY clause or this table uses the specific
** index specified by its INDEXED BY clause. This rule ensures
** that a best-so-far is always selected even if an impossible
** combination of INDEXED BY clauses are given. The error
** will be detected and relayed back to the application later.
** The NEVER() comes about because rule (2) above prevents
** An indexable full-table-scan from reaching rule (3).
**
** (4) The plan cost must be lower than prior plans, where "cost"
** is defined by the compareCost() function above.
*/
if( (sWBI.cost.used&sWBI.notValid)==0 /* (1) */
&& (nUnconstrained==0 || sWBI.pSrc->pIndex==0 /* (3) */
|| NEVER((sWBI.cost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0))
&& (bestJ<0 || compareCost(&sWBI.cost, &bestPlan)) /* (4) */
){
WHERETRACE((" === table %d (%s) is best so far\n"
" cost=%.1f, nRow=%.1f, nOBSat=%d, wsFlags=%08x\n",
j, sWBI.pSrc->pTab->zName,
|
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