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Overview
| Comment: | Do not use the viewscan optimization on a query that has only a single loop, as the cost adjustments can cause problems for outer queries. Proposed fix for the performance regression reported by forum post 64d36440e473516c. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
76152ad2ffe56034f2fd93d9a1ce9358 |
| User & Date: | drh 2023-07-18 21:06:19 |
Context
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2023-07-19
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| 09:52 | Two minor improvements to sum(), one of which was inspired by forum post af5be98dbc. (check-in: a0d3e757 user: drh tags: trunk) | |
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2023-07-18
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| 21:06 | Do not use the viewscan optimization on a query that has only a single loop, as the cost adjustments can cause problems for outer queries. Proposed fix for the performance regression reported by forum post 64d36440e473516c. (check-in: 76152ad2 user: drh tags: trunk) | |
| 20:41 | Improved ".wheretrace" for the VIEWSCAN optimization. (check-in: 27057ea7 user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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5118 5119 5120 5121 5122 5123 5124 |
}else{
rCost = rUnsorted;
rUnsorted -= 2; /* TUNING: Slight bias in favor of no-sort plans */
}
/* TUNING: A full-scan of a VIEW or subquery in the outer loop
** is not so bad. */
| | | 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 |
}else{
rCost = rUnsorted;
rUnsorted -= 2; /* TUNING: Slight bias in favor of no-sort plans */
}
/* TUNING: A full-scan of a VIEW or subquery in the outer loop
** is not so bad. */
if( iLoop==0 && (pWLoop->wsFlags & WHERE_VIEWSCAN)!=0 && nLoop>1 ){
rCost += -10;
nOut += -30;
WHERETRACE(0x80,("VIEWSCAN cost reduction for %c\n",pWLoop->cId));
}
/* Check to see if pWLoop should be added to the set of
** mxChoice best-so-far paths.
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