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Commit465a3b0

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Copy sub-Query nodes to avoid trouble when same sub-Query is linked to
multiple times in the parsetree (can happen in COALESCE or BETWEENcontexts, for example). This is a pretty grotty solution --- it willdo for now, but perhaps we can do better when we redesign querytrees.What we need is a consistent policy about whether querytrees should beconsidered read-only structures or not ...
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‎src/backend/optimizer/plan/subselect.c

Lines changed: 15 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.39 2000/07/12 02:37:09 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.40 2000/08/06 04:13:22 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -134,13 +134,24 @@ make_subplan(SubLink *slink)
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PlannerQueryLevel++;/* we become child */
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/* Check to see if this node was already processed; if so we have
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* trouble. Someday should change tree representation so that we can
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* cope with multiple links to the same subquery, but for now...
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/*
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* Check to see if this node was already processed; if so we have
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* trouble. We check to see if the linked-to Query appears to have
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* been planned already, too.
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*/
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if (subquery==NULL)
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elog(ERROR,"make_subplan: invalid expression structure (SubLink already processed?)");
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if (subquery->base_rel_list!=NIL)
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elog(ERROR,"make_subplan: invalid expression structure (subquery already processed?)");
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/*
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* Copy the source Query node. This is a quick and dirty kluge to resolve
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* the fact that the parser can generate trees with multiple links to the
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* same sub-Query node, but the planner wants to scribble on the Query.
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* Try to clean this up when we do querytree redesign...
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*/
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subquery= (Query*)copyObject(subquery);
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/*
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* For an EXISTS subplan, tell lower-level planner to expect that only
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* the first tuple will be retrieved. For ALL and ANY subplans, we

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