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.

1 files changed, 10 insertions, 6 deletions

diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index c39759ee1c9..ae6fcea7e67 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.285 2009/03/31 17:59:56 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.286 2009/03/31 22:12:48 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -829,7 +829,11 @@ RelationBuildDesc(Oid targetRelId, Relation oldrelation)
 	relation->rd_isnailed = false;
 	relation->rd_createSubid = InvalidSubTransactionId;
 	relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
-	relation->rd_istemp = isTempOrToastNamespace(relation->rd_rel->relnamespace);
+	relation->rd_istemp = relation->rd_rel->relistemp;
+	if (relation->rd_istemp)
+		relation->rd_islocaltemp = isTempOrToastNamespace(relation->rd_rel->relnamespace);
+	else
+		relation->rd_islocaltemp = false;
 
 	/*
 	 * initialize the tuple descriptor (relation->rd_att).
@@ -1375,6 +1379,7 @@ formrdesc(const char *relationName, Oid relationReltype,
 	relation->rd_createSubid = InvalidSubTransactionId;
 	relation->rd_newRelfilenodeSubid = InvalidSubTransactionId;
 	relation->rd_istemp = false;
+	relation->rd_islocaltemp = false;
 
 	/*
 	 * initialize relation tuple form
@@ -2355,8 +2360,9 @@ RelationBuildLocalRelation(const char *relname,
 	/* must flag that we have rels created in this transaction */
 	need_eoxact_work = true;
 
-	/* is it a temporary relation? */
+	/* it is temporary if and only if it is in my temp-table namespace */
 	rel->rd_istemp = isTempOrToastNamespace(relnamespace);
+	rel->rd_islocaltemp = rel->rd_istemp;
 
 	/*
 	 * create a new tuple descriptor from the one passed in.  We do this
@@ -2403,9 +2409,7 @@ RelationBuildLocalRelation(const char *relname,
 	 * as the logical ID (OID).
 	 */
 	rel->rd_rel->relisshared = shared_relation;
-
-	/* it is temporary if and only if it is in my temp-table namespace */
-	rel->rd_rel->relistemp = isTempOrToastNamespace(relnamespace);
+	rel->rd_rel->relistemp = rel->rd_istemp;
 
 	RelationGetRelid(rel) = relid;