Clean out column-level pg_init_privs entries when dropping tables.

DeleteInitPrivs did not get the memo about how, when dropping a
whole object (with subid == 0), you should drop entries relating
to its sub-objects too.  This is visible in the test_pg_dump test
case if one drops the extension at the end: the entry for
	GRANT SELECT(col1) ON regress_pg_dump_table TO public;
was still present in pg_init_privs afterwards, although it was
pointing to a dangling table OID.

Noted while fooling with a fix for REASSIGN OWNED for pg_init_privs
entries.  This bug is aboriginal in the pg_init_privs feature
though, and there seems no reason not to back-patch the fix.

src/backend/catalog/dependency.c

@@ -1328,7 +1328,9 @@ deleteOneObject(const ObjectAddress *object, Relation *depRel, int flags)
 	/*
 	 * Delete any comments, security labels, or initial privileges associated
 	 * with this object.  (This is a convenient place to do these things,
-	 * rather than having every object type know to do it.)
+	 * rather than having every object type know to do it.)  As above, all
+	 * these functions must remove records for sub-objects too if the subid is
+	 * zero.
 	 */
 	DeleteComments(object->objectId, object->classId, object->objectSubId);
 	DeleteSecurityLabel(object);
@@ -2887,6 +2889,7 @@ DeleteInitPrivs(const ObjectAddress *object)
 {
 	Relation	relation;
 	ScanKeyData key[3];
+	int			nkeys;
 	SysScanDesc scan;
 	HeapTuple	oldtuple;
 
@@ -2900,13 +2903,19 @@ DeleteInitPrivs(const ObjectAddress *object)
 				Anum_pg_init_privs_classoid,
 				BTEqualStrategyNumber, F_OIDEQ,
 				ObjectIdGetDatum(object->classId));
-	ScanKeyInit(&key[2],
+	if (object->objectSubId != 0)
-				Anum_pg_init_privs_objsubid,
+	{
-				BTEqualStrategyNumber, F_INT4EQ,
+		ScanKeyInit(&key[2],
-				Int32GetDatum(object->objectSubId));
+					Anum_pg_init_privs_objsubid,
+					BTEqualStrategyNumber, F_INT4EQ,
+					Int32GetDatum(object->objectSubId));
+		nkeys = 3;
+	}
+	else
+		nkeys = 2;
 
 	scan = systable_beginscan(relation, InitPrivsObjIndexId, true,
-							  NULL, 3, key);
+							  NULL, nkeys, key);
 
 	while (HeapTupleIsValid(oldtuple = systable_getnext(scan)))
 		CatalogTupleDelete(relation, &oldtuple->t_self);

src/test/modules/test_pg_dump/expected/test_pg_dump.out

@@ -93,3 +93,10 @@ ALTER EXTENSION test_pg_dump DROP SERVER s0;
 ALTER EXTENSION test_pg_dump DROP TABLE test_pg_dump_t1;
 ALTER EXTENSION test_pg_dump DROP TYPE test_pg_dump_e1;
 ALTER EXTENSION test_pg_dump DROP VIEW test_pg_dump_v1;
+DROP EXTENSION test_pg_dump;
+-- shouldn't be anything left in pg_init_privs
+SELECT * FROM pg_init_privs WHERE privtype = 'e';
+ objoid | classoid | objsubid | privtype | initprivs 
+--------+----------+----------+----------+-----------
+(0 rows)
+

src/test/modules/test_pg_dump/sql/test_pg_dump.sql

@@ -106,3 +106,8 @@ ALTER EXTENSION test_pg_dump DROP SERVER s0;
 ALTER EXTENSION test_pg_dump DROP TABLE test_pg_dump_t1;
 ALTER EXTENSION test_pg_dump DROP TYPE test_pg_dump_e1;
 ALTER EXTENSION test_pg_dump DROP VIEW test_pg_dump_v1;
+
+DROP EXTENSION test_pg_dump;
+
+-- shouldn't be anything left in pg_init_privs
+SELECT * FROM pg_init_privs WHERE privtype = 'e';