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Fix performance problem in fireRIRonSubselect: with nested subqueries,

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fireRIRonSubselect was invoked twice at each subselect, leading to an
exponential amount of wasted effort.
This commit is contained in:
Tom Lane
2000-03-12 18:57:05 +00:00
parent 117fa25ae1
commit ef3386affe
1 changed files with 6 additions and 12 deletions
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18
src/backend/rewrite/rewriteHandler.c
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@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.67 2000/01/27 18:11:37 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.68 2000/03/12 18:57:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -958,10 +958,6 @@ fireRIRonSubselect(Node *node, void *context)
return false;
if (IsA(node, SubLink))
{
/*
* Standard expression_tree_walker will not recurse into subselect,
* but here we must do so.
*/
SubLink *sub = (SubLink *) node;
Query *qry;
@@ -971,14 +967,12 @@ fireRIRonSubselect(Node *node, void *context)
/* Do what we came for */
qry = fireRIRrules((Query *) (sub->subselect));
sub->subselect = (Node *) qry;
/* Must recurse to handle any sub-subselects! */
if (fireRIRonSubselect((Node *) qry, context))
return true;
/* Need not recurse into subselect, because fireRIRrules did it */
return false;
}
if (IsA(node, Query))
{
/* Reach here after recursing down into subselect above... */
/* Reach here when called from fireRIRrules */
Query *qry = (Query *) node;
if (fireRIRonSubselect((Node *) (qry->targetList), context))
@@ -1107,12 +1101,12 @@ fireRIRrules(Query *parsetree)
heap_close(rel, AccessShareLock);
}
if (parsetree->hasSubLinks)
fireRIRonSubselect((Node *) parsetree, NULL);
if (parsetree->hasAggs)
parsetree->qual = modifyAggrefQual(parsetree->qual, parsetree);
if (parsetree->hasSubLinks)
fireRIRonSubselect((Node *) parsetree, NULL);
return parsetree;
}