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Add a small cost penalty to sorting to bias the query planner in favor of

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plans that do not require a final sorting pass.

FossilOrigin-Name: 85b9beb4605eb0cfe2ed063c2a1925186c9e37031f78c875e60a347cce891638
This commit is contained in:
drh
2018-07-28 21:01:55 +00:00
parent 07aded63f4
commit f559ed3400
5 changed files with 16 additions and 12 deletions
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6
src/where.c
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@@ -4056,7 +4056,11 @@ static int wherePathSolver(WhereInfo *pWInfo, LogEst nRowEst){
pWInfo, nRowEst, nOrderBy, isOrdered
);
}
rCost = sqlite3LogEstAdd(rUnsorted, aSortCost[isOrdered]);
/* TUNING: Add a small extra penalty (5) to sorting as an
** extra encouragment to the query planner to select a plan
** where the rows emerge in the correct order without any sorting
** required. */
rCost = sqlite3LogEstAdd(rUnsorted, aSortCost[isOrdered]) + 5;
WHERETRACE(0x002,
("---- sort cost=%-3d (%d/%d) increases cost %3d to %-3d\n",