Many hyperlinks are disabled.
Use anonymous login
to enable hyperlinks.
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. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | apple-increased-sorting-cost |
| Files: | files | file ages | folders |
| SHA1: |
38298ef923c8dad6860385ac4a20849e |
| User & Date: | drh 2017-02-17 21:23:25.595 |
Context
|
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) | |
|
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) | |
|
2016-11-17
| ||
| 14:02 | When opening the *-shm file for a readonly database, try to open it in read-write mode before falling back to readonly. This is in case some other read/write connection within the same process uses the same file descriptor. (check-in: a07c581e88 user: dan tags: apple-osx) | |
Changes
Changes to src/where.c.
| ︙ | ︙ | |||
3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 |
**
** 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);
| > > > > > > > > > > | 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 |
**
** 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->pDistinctSet
&& pWInfo->pDistinctSet->nExpr>6
){
rSortCost += sqlite3LogEst(pWInfo->pDistinctSet->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);
|
| ︙ | ︙ |