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Changes In Branch apple-increased-sorting-cost Excluding Merge-Ins
This is equivalent to a diff from a07c581e88 to 38298ef923
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2017-02-17
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| 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) | |
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2017-02-16
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| 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) | |
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2016-11-26
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| 20:12 | Update test case for opening SHM files read/write on a read-only connection so that they are only attempted on Darwin with SQLITE_ENABLE_PRESIST_WAL. (check-in: d6a7bf80cf user: drh tags: apple-osx) | |
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2016-11-17
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| 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) | |
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2016-11-04
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| 19:09 | Merge recent trunk changes, including all the fixes that appeared in version 3.15.1. (check-in: 0e5ffd9123 user: drh tags: apple-osx) | |
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 + 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);
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