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Overview
| Comment: | Increase the estimated cost of sorting when sorting wide results sets, to account for the extra storage space and I/O required for the external sort. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | increased-sorting-cost |
| Files: | files | file ages | folders |
| SHA1: |
aa0703e5cef0c61bec965d4c88ee48bb |
| User & Date: | drh 2017-02-16 21:29:53.177 |
Context
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2017-02-17
| ||
| 21:23 | Increase the estimated cost of sorting when sorting wide results sets, to account for the extra storage space and I/O required for the external sort. (Leaf check-in: 38298ef923 user: drh tags: apple-increased-sorting-cost) | |
| 02:07 | Merge fixes from trunk. (Leaf check-in: 662e8ccf7e user: drh tags: increased-sorting-cost) | |
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2017-02-16
| ||
| 21:29 | Increase the estimated cost of sorting when sorting wide results sets, to account for the extra storage space and I/O required for the external sort. (check-in: aa0703e5ce user: drh tags: increased-sorting-cost) | |
| 20:52 | Change the name of WhereInfo.pDistinctSet to pResultSet, since it is now used for more than just DISTINCT processing. (check-in: 9fc5cd505f user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 |
**
** 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 + rScale + 16;
/* Multiple by log(M) where M is the number of output rows.
** Use the LIMIT for M if it is smaller */
if( (pWInfo->wctrlFlags & WHERE_USE_LIMIT)!=0 && pWInfo->iLimit<nRow ){
nRow = pWInfo->iLimit;
}
rSortCost += estLog(nRow);
| > > > > > > > > > > | 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 |
**
** 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 + rScale + 16;
/* For wide sorts (many payload columns) increase the sorting cost
** to account for the additional I/O used by the external sorting
** algorithm when it flushes PMAs to disk.
*/
if( pWInfo->pResultSet
&& pWInfo->pResultSet->nExpr>6
){
rSortCost += sqlite3LogEst(pWInfo->pResultSet->nExpr) - 26;
}
/* Multiple by log(M) where M is the number of output rows.
** Use the LIMIT for M if it is smaller */
if( (pWInfo->wctrlFlags & WHERE_USE_LIMIT)!=0 && pWInfo->iLimit<nRow ){
nRow = pWInfo->iLimit;
}
rSortCost += estLog(nRow);
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| ︙ | ︙ |