Skip other sessions' temp tables in REPACK, CLUSTER, and VACUUM FULL

get_tables_to_repack() and get_all_vacuum_rels() were including other
sessions' temporary tables in their output work list, causing REPACK,
CLUSTER and VACUUM FULL (when executed without a table list) to attempt
to acquire AccessExclusiveLock on them, potentially blocking for an
extended time.  Fix by skipping other-session temp tables early, before
they are added to the list.

This issue is ancient, but there have been no complaints about it that I
know of, so I'm opting for not backpatching at present.

Author: Jim Jones <jim.jones@uni-muenster.de>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
Discussion: https://postgr.es/m/0b555318-2bf2-46df-9377-09629a2a59db@uni-muenster.de

src/backend/commands/repack.c

@@ -2106,6 +2106,8 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt)
 		{
 			RelToCluster *rtc;
 			Form_pg_index index;
+			HeapTuple	classtup;
+			Form_pg_class classForm;
 			MemoryContext oldcxt;
 
 			index = (Form_pg_index) GETSTRUCT(tuple);
@@ -2120,11 +2122,24 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt)
 				continue;
 
 			/* Verify that the table still exists; skip if not */
-			if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(index->indrelid)))
+			classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid));
+			if (!HeapTupleIsValid(classtup))
 			{
 				UnlockRelationOid(index->indrelid, AccessShareLock);
 				continue;
 			}
+			classForm = (Form_pg_class) GETSTRUCT(classtup);
+
+			/* Skip temp relations belonging to other sessions */
+			if (classForm->relpersistence == RELPERSISTENCE_TEMP &&
+				!isTempOrTempToastNamespace(classForm->relnamespace))
+			{
+				ReleaseSysCache(classtup);
+				UnlockRelationOid(index->indrelid, AccessShareLock);
+				continue;
+			}
+
+			ReleaseSysCache(classtup);
 
 			/* noisily skip rels which the user can't process */
 			if (!repack_is_permitted_for_relation(cmd, index->indrelid,
@@ -2180,6 +2195,14 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt)
 				continue;
 			}
 
+			/* Skip temp relations belonging to other sessions */
+			if (class->relpersistence == RELPERSISTENCE_TEMP &&
+				!isTempOrTempToastNamespace(class->relnamespace))
+			{
+				UnlockRelationOid(class->oid, AccessShareLock);
+				continue;
+			}
+
 			/* noisily skip rels which the user can't process */
 			if (!repack_is_permitted_for_relation(cmd, class->oid,
 												  GetUserId()))

src/backend/commands/vacuum.c

@@ -1063,6 +1063,11 @@ get_all_vacuum_rels(MemoryContext vac_context, int options)
 			classForm->relkind != RELKIND_PARTITIONED_TABLE)
 			continue;
 
+		/* Skip temp relations belonging to other sessions */
+		if (classForm->relpersistence == RELPERSISTENCE_TEMP &&
+			!isTempOrTempToastNamespace(classForm->relnamespace))
+			continue;
+
 		/* check permissions of relation */
 		if (!vacuum_is_permitted_for_relation(relid, classForm, options))
 			continue;