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Copy sub-Query nodes to avoid trouble when same sub-Query is linked to

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multiple times in the parsetree (can happen in COALESCE or BETWEEN
contexts, for example).  This is a pretty grotty solution --- it will
do for now, but perhaps we can do better when we redesign querytrees.
What we need is a consistent policy about whether querytrees should be
considered read-only structures or not ...
This commit is contained in:
Tom Lane 2000-08-06 04:13:22 +00:00
parent 75b61043b0
commit 465a3b0a24
1 changed files with 15 additions and 4 deletions
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19
src/backend/optimizer/plan/subselect.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.39 2000/07/12 02:37:09 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.40 2000/08/06 04:13:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -134,13 +134,24 @@ make_subplan(SubLink *slink)
PlannerQueryLevel++; /* we become child */
/* Check to see if this node was already processed; if so we have
* trouble. Someday should change tree representation so that we can
* cope with multiple links to the same subquery, but for now...
/*
* Check to see if this node was already processed; if so we have
* trouble. We check to see if the linked-to Query appears to have
* been planned already, too.
*/
if (subquery == NULL)
elog(ERROR, "make_subplan: invalid expression structure (SubLink already processed?)");
if (subquery->base_rel_list != NIL)
elog(ERROR, "make_subplan: invalid expression structure (subquery already processed?)");
/*
* Copy the source Query node. This is a quick and dirty kluge to resolve
* the fact that the parser can generate trees with multiple links to the
* same sub-Query node, but the planner wants to scribble on the Query.
* Try to clean this up when we do querytree redesign...
*/
subquery = (Query *) copyObject(subquery);
/*
* For an EXISTS subplan, tell lower-level planner to expect that only
* the first tuple will be retrieved. For ALL and ANY subplans, we