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Teach the planner to remove SubqueryScan nodes from the plan if they

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aren't doing anything useful (ie, neither selection nor projection).
Also, extend to SubqueryScan the hacks already in place to avoid
unnecessary ExecProject calls when the result would just be the same
tuple the subquery already delivered.  This saves some overhead in
UNION and other set operations, as well as avoiding overhead for
unflatten-able subqueries.  Per example from Sokolov Yura.
This commit is contained in:
Tom Lane
2005-05-22 22:30:20 +00:00
parent c61207b091
commit e2159f3842
13 changed files with 605 additions and 177 deletions
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16
src/backend/executor/execMain.c
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@ -26,7 +26,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.248 2005/05/06 17:24:53 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.249 2005/05/22 22:30:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -353,16 +353,10 @@ ExecCheckRTEPerms(RangeTblEntry *rte)
AclId userid;
/*
* If it's a subquery, recursively examine its rangetable.
*/
if (rte->rtekind == RTE_SUBQUERY)
{
ExecCheckRTPerms(rte->subquery->rtable);
return;
}
/*
* Otherwise, only plain-relation RTEs need to be checked here.
* Only plain-relation RTEs need to be checked here. Subquery RTEs
* are checked by ExecInitSubqueryScan if the subquery is still a
* separate subquery --- if it's been pulled up into our query level
* then the RTEs are in our rangetable and will be checked here.
* Function RTEs are checked by init_fcache when the function is
* prepared for execution. Join and special RTEs need no checks.
*/