Not try locking relations referencing to views (#6430)

Since there can't be such a foreign key already.

This mainly fixes the error that Citus throws
when trying to truncate a distributed view.

Fixes #5990.

src/backend/distributed/utils/resource_lock.c

@@ -1357,7 +1357,11 @@ AcquireDistributedLockOnRelations(List *relationList, LOCKMODE lockMode, uint32
 													 (void *) lockRelationRecord);
 		}
 
-		if ((configs & DIST_LOCK_REFERENCING_TABLES) > 0)
+		char relkind = get_rel_relkind(relationId);
+		bool relationCanBeReferenced = (relkind == RELKIND_RELATION ||
+										relkind == RELKIND_PARTITIONED_TABLE);
+		if (relationCanBeReferenced &&
+			(configs & DIST_LOCK_REFERENCING_TABLES) > 0)
 		{
 			CitusTableCacheEntry *cacheEntry = GetCitusTableCacheEntry(relationId);
 			Assert(cacheEntry != NULL);

src/test/regress/expected/multi_truncate.out

@@ -522,6 +522,18 @@ SELECT truncate_local_data_after_distributing_table('t1');
 (1 row)
 
 ALTER TABLE t1 VALIDATE CONSTRAINT t1_a_check;
+CREATE TABLE tbl(a INT);
+SELECT create_distributed_table('tbl', 'a');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE VIEW vw AS SELECT * FROM tbl;
+-- throws an error because vw is not a table
+TRUNCATE TABLE tbl, vw CASCADE;
+ERROR:  "vw" is not a table
+SET client_min_messages TO ERROR;
 DROP VIEW table_sizes;
 DROP TABLE t1;
 DROP SCHEMA multi_truncate CASCADE;

src/test/regress/sql/multi_truncate.sql

@@ -304,6 +304,15 @@ ALTER TABLE t1 VALIDATE CONSTRAINT t1_a_check;
 SELECT truncate_local_data_after_distributing_table('t1');
 ALTER TABLE t1 VALIDATE CONSTRAINT t1_a_check;
 
+CREATE TABLE tbl(a INT);
+SELECT create_distributed_table('tbl', 'a');
+CREATE VIEW vw AS SELECT * FROM tbl;
+
+-- throws an error because vw is not a table
+TRUNCATE TABLE tbl, vw CASCADE;
+
+SET client_min_messages TO ERROR;
+
 DROP VIEW table_sizes;
 DROP TABLE t1;
 DROP SCHEMA multi_truncate CASCADE;