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Avoid pulling up sublinks from a subselect's targetlist. Works around

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problems that occur if sublink is referenced via a join alias variable.
Perhaps this can be improved later, but a simple and safe fix is needed
for 7.3.1.
This commit is contained in:
Tom Lane 2002-12-05 21:46:37 +00:00
parent fae2f14cdd
commit 993b145d7f
1 changed files with 20 additions and 2 deletions
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22
src/backend/optimizer/plan/planner.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.132 2002/11/29 21:39:11 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.133 2002/12/05 21:46:37 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -357,10 +357,14 @@ pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
* nothing will happen after the first time. We do have to be
* careful to copy everything we pull up, however, or risk
* having chunks of structure multiply linked.
*
* Note: 'false' is correct here even if we are within an outer
* join in the upper query; the lower query starts with a clean
* slate for outer-join semantics.
*/
subquery->jointree = (FromExpr *)
pull_up_subqueries(subquery, (Node *) subquery->jointree,
below_outer_join);
false);
/*
* Now make a modifiable copy of the subquery that we can run
@ -542,6 +546,20 @@ is_simple_subquery(Query *subquery)
if (expression_returns_set((Node *) subquery->targetList))
return false;
/*
* Don't pull up a subquery that has any sublinks in its targetlist,
* either. As of PG 7.3 this creates problems because the pulled-up
* expressions may go into join alias lists, and the sublinks would
* not get fixed because we do flatten_join_alias_vars() too late.
* Eventually we should do a complete flatten_join_alias_vars as the
* first step of preprocess_expression, and then we could probably
* support this. (BUT: it might be a bad idea anyway, due to possibly
* causing multiple evaluations of an expensive sublink.)
*/
if (subquery->hasSubLinks &&
contain_subplans((Node *) subquery->targetList))
return false;
/*
* Hack: don't try to pull up a subquery with an empty jointree.
* query_planner() will correctly generate a Result plan for a