From 2a06b3bdfddf3d06575ea1fe662abe1278229f34 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 12 Jun 2001 18:54:22 +0000
Subject: [PATCH] Repair problem with multi-action rules in combination with
any nontrivial manipulation of rtable/jointree by planner. Rewriter was
generating actions that shared rtable/jointree substructure, which caused
havoc when planner got to the later actions that it'd already mucked up.
---
src/backend/rewrite/rewriteHandler.c | 39 ++++++++++++++--------------
1 file changed, 19 insertions(+), 20 deletions(-)
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 2787b9ce553..d78334d83d3 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.93 2001/05/03 17:47:49 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.94 2001/06/12 18:54:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -82,7 +82,7 @@ gatherRewriteMeta(Query *parsetree,
/*
* Adjust rule action and qual to offset its varnos, so that we can
- * merge its rtable into the main parsetree's rtable.
+ * merge its rtable with the main parsetree's rtable.
*
* If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries
* will be in the SELECT part, and we have to modify that rather than
@@ -99,23 +99,19 @@ gatherRewriteMeta(Query *parsetree,
PRS2_OLD_VARNO + rt_length, rt_index, 0);
/*
- * We want the main parsetree's rtable to end up as the concatenation
- * of its original contents plus those of all the relevant rule
- * actions. Also store same into all the rule_action rtables. Some of
- * the entries may be unused after we finish rewriting, but if we
- * tried to clean those out we'd have a much harder job to adjust RT
- * indexes in the query's Vars. It's OK to have unused RT entries,
- * since planner will ignore them.
+ * Generate expanded rtable consisting of main parsetree's rtable
+ * plus rule action's rtable; this becomes the complete rtable for the
+ * rule action. Some of the entries may be unused after we finish
+ * rewriting, but if we tried to clean those out we'd have a much harder
+ * job to adjust RT indexes in the query's Vars. It's OK to have unused
+ * RT entries, since planner will ignore them.
*
- * NOTE KLUGY HACK: we assume the parsetree rtable had at least one entry
- * to begin with (OK enough, else where'd the rule come from?).
- * Because of this, if multiple rules nconc() their rtable additions
- * onto parsetree->rtable, they'll all see the same rtable because
- * they all have the same list head pointer.
+ * NOTE: because planner will destructively alter rtable, we must ensure
+ * that rule action's rtable is separate and shares no substructure with
+ * the main rtable. Hence do a deep copy here.
*/
- parsetree->rtable = nconc(parsetree->rtable,
- sub_action->rtable);
- sub_action->rtable = parsetree->rtable;
+ sub_action->rtable = nconc((List *) copyObject(parsetree->rtable),
+ sub_action->rtable);
/*
* Each rule action's jointree should be the main parsetree's jointree
@@ -128,6 +124,9 @@ gatherRewriteMeta(Query *parsetree,
* data for the quals. We don't want the original rtindex to be
* joined twice, however, so avoid keeping it if the rule action
* mentions it.
+ *
+ * As above, the action's jointree must not share substructure with
+ * the main parsetree's.
*/
if (sub_action->jointree != NULL)
{
@@ -193,13 +192,13 @@ gatherRewriteMeta(Query *parsetree,
* occurrence of the given rt_index as a top-level join item (we do not look
* for it within join items; this is OK because we are only expecting to find
* it as an UPDATE or DELETE target relation, which will be at the top level
- * of the join). Returns modified jointree list --- original list is not
- * changed.
+ * of the join). Returns modified jointree list --- this is a separate copy
+ * sharing no nodes with the original.
*/
static List *
adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
{
- List *newjointree = listCopy(parsetree->jointree->fromlist);
+ List *newjointree = copyObject(parsetree->jointree->fromlist);
List *jjt;
if (removert)
--
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