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Overview
| Comment: | Remove the unexplained extra 3.0 cost factor for the B-tree sorting that is done to implement DISTINCT in the absence of an index to help. |
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| Timelines: | family | ancestors | descendants | both | trunk |
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| SHA1: |
52571991fcfa2629e8a8354e0c9a62e7 |
| User & Date: | drh 2016-02-11 21:55:23 |
Context
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2016-02-11
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| 21:59 | Enhance the MSVC makefile to enable building 'testfixture' fully from source code. check-in: f183e059 user: mistachkin tags: trunk | |
| 21:55 | Remove the unexplained extra 3.0 cost factor for the B-tree sorting that is done to implement DISTINCT in the absence of an index to help. check-in: 52571991 user: drh tags: trunk | |
| 21:53 | Remove the unused fts5BlobCompare() routine. check-in: defc762d user: drh tags: trunk | |
Changes
Changes to src/where.c.
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** ** The (Y/X) term is implemented using stack variable rScale ** below. */ LogEst rScale, rSortCost; assert( nOrderBy>0 && 66==sqlite3LogEst(100) ); rScale = sqlite3LogEst((nOrderBy-nSorted)*100/nOrderBy) - 66; rSortCost = nRow + estLog(nRow) + rScale + 16; /* TUNING: The cost of implementing DISTINCT using a B-TREE is ** similar but with a larger constant of proportionality. ** Multiply by an additional factor of 3.0. */ if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){ rSortCost += 16; } return rSortCost; } /* ** Given the list of WhereLoop objects at pWInfo->pLoops, this routine ** attempts to find the lowest cost path that visits each WhereLoop ** once. This path is then loaded into the pWInfo->a[].pWLoop fields. |
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3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 |
** ** The (Y/X) term is implemented using stack variable rScale ** below. */ LogEst rScale, rSortCost; assert( nOrderBy>0 && 66==sqlite3LogEst(100) ); rScale = sqlite3LogEst((nOrderBy-nSorted)*100/nOrderBy) - 66; rSortCost = nRow + estLog(nRow) + rScale + 16; return rSortCost; } /* ** Given the list of WhereLoop objects at pWInfo->pLoops, this routine ** attempts to find the lowest cost path that visits each WhereLoop ** once. This path is then loaded into the pWInfo->a[].pWLoop fields. |