From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Chris Bitmead <chris(at)bitmead(dot)com> |
Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, pgsql-core(at)postgresql(dot)org, "pgsql-patches(at)postgresql(dot)org" <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: Re: [CORE] Re: MY PATCH |
Date: | 2000-06-10 02:02:45 |
Message-ID: | 21424.960602565@sss.pgh.pa.us |
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Lists: | pgsql-patches |
OK, I see at least one of the problems here.
UPDATE/DELETE with an Append plan have never worked --- not in recent
memory anyway --- because execMain's InitPlan() creates a result
RelationInfo that EndPlan() is expecting to close. But if the top plan
node is an Append then nodeAppend.c scribbles on
estate->es_result_relation_info. This leaves the originally created
RelationInfo unreachable ... which is bad enough, since that means a
leaked rel refcount, but there's worse to come. nodeAppend.c creates
its own set of RelationInfo nodes for the relation(s) it will scan.
At query end, it's left estate->es_result_relation_info pointing at a
random one of these. nodeAppend.c closes *and deletes* all its
RelationInfos. Now estate->es_result_relation_info is pointing at a
closed-and-deleted RelationInfo that EndPlan() will then try to close
again. Oops.
I believe the correct fix is
(a) ExecInitAppend() must incorporate the RelationInfo already
created by InitPlan() into its list of RelationInfos, rather
than creating a second RelationInfo (= extra relcache refcount)
for that relation.
(b) ExecEndAppend() must reset estate->es_result_relation_info to
NULL, so it won't be left pointing to a deleted RelationInfo.
(c) EndPlan() must not examine estate->es_result_relation_info until
after it has called the node-type-specific end routine; otherwise
change (b) will not be able to prevent EndPlan() from doing the
wrong thing.
On it now...
regards, tom lane
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