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Modify the relcache to record the temp status of both local and nonlocal

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temp relations; this is no more expensive than before, now that we have
pg_class.relistemp.  Insert tests into bufmgr.c to prevent attempting
to fetch pages from nonlocal temp relations.  This provides a low-level
defense against bugs-of-omission allowing temp pages to be loaded into shared
buffers, as in the contrib/pgstattuple problem reported by Stuart Bishop.
While at it, tweak a bunch of places to use new relcache tests (instead of
expensive probes into pg_namespace) to detect local or nonlocal temp tables.
This commit is contained in:
Tom Lane
2009-03-31 22:12:48 +00:00
parent 84a059abf7
commit 948d6ec90f
14 changed files with 92 additions and 56 deletions
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20
src/backend/storage/buffer/bufmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.249 2009/03/23 01:52:38 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.250 2009/03/31 22:12:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -122,6 +122,12 @@ PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
if (reln->rd_istemp)
{
/* see comments in ReadBufferExtended */
if (RELATION_IS_OTHER_TEMP(reln))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot access temporary tables of other sessions")));
/* pass it off to localbuf.c */
LocalPrefetchBuffer(reln->rd_smgr, forkNum, blockNum);
}
@ -204,6 +210,16 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
/* Open it at the smgr level if not already done */
RelationOpenSmgr(reln);
/*
* Reject attempts to read non-local temporary relations; we would
* be likely to get wrong data since we have no visibility into the
* owning session's local buffers.
*/
if (RELATION_IS_OTHER_TEMP(reln))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot access temporary tables of other sessions")));
/*
* Read the buffer, and update pgstat counters to reflect a cache
* hit or miss.
@ -220,6 +236,8 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
/*
* ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
* a relcache entry for the relation.
*
* NB: caller is assumed to know what it's doing if isTemp is true.
*/
Buffer
ReadBufferWithoutRelcache(RelFileNode rnode, bool isTemp,