Fix failure to ignore leftover temp tables after a server crash.

During crash recovery, we remove disk files belonging to temporary tables,
but the system catalog entries for such tables are intentionally not
cleaned up right away.  Instead, the first backend that uses a temp schema
is expected to clean out any leftover objects therein.  This approach
requires that we be careful to ignore leftover temp tables (since any
actual access attempt would fail), *even if their BackendId matches our
session*, if we have not yet established use of the session's corresponding
temp schema.  That worked fine in the past, but was broken by commit
debcec7dc31a992703911a9953e299c8d730c778 which incorrectly removed the
rd_islocaltemp relcache flag.  Put it back, and undo various changes
that substituted tests like "rel->rd_backend == MyBackendId" for use
of a state-aware flag.  Per trouble report from Heikki Linnakangas.

Back-patch to 9.1 where the erroneous change was made.  In the back
branches, be careful to add rd_islocaltemp in a spot in the struct that
was alignment padding before, so as not to break existing add-on code.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
index cd23334a1a5..581fbfd7fa7 100644
--- a/src/backend/utils/adt/dbsize.c
+++ b/src/backend/utils/adt/dbsize.c
@@ -260,6 +260,9 @@ pg_tablespace_size_name(PG_FUNCTION_ARGS)
 
 /*
  * calculate size of (one fork of) a relation
+ *
+ * Note: we can safely apply this to temp tables of other sessions, so there
+ * is no check here or at the call sites for that.
  */
 static int64
 calculate_relation_size(RelFileNode *rfn, BackendId backend, ForkNumber forknum)
@@ -314,7 +317,7 @@ pg_relation_size(PG_FUNCTION_ARGS)
 	 * that makes queries like "SELECT pg_relation_size(oid) FROM pg_class"
 	 * less robust, because while we scan pg_class with an MVCC snapshot,
 	 * someone else might drop the table. It's better to return NULL for
-	 * alread-dropped tables than throw an error and abort the whole query.
+	 * already-dropped tables than throw an error and abort the whole query.
 	 */
 	if (rel == NULL)
 		PG_RETURN_NULL();