From 948d6ec90fd35d6e1a59d0b1af8d6efd8442f0ad Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 31 Mar 2009 22:12:48 +0000 Subject: Modify the relcache to record the temp status of both local and nonlocal 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. --- src/backend/storage/buffer/bufmgr.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) (limited to 'src/backend/storage/buffer/bufmgr.c') diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 1f6e8d36803..4a7dda3edbb 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -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, -- cgit v1.2.3