diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 93ad49e59fd..e9d1c43d903 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -16183,7 +16183,10 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
 		 * CONSTRAINT step, so there's no value in asking for anything weaker.
 		 */
 		if (relid != tab->relid)
+{
+char *relname = get_rel_name(relid); if (relname && strcmp(relname, "atref") == 0) pg_usleep(500000);
 			LockRelationOid(relid, AccessExclusiveLock);
+}
 
 		ATPostAlterTypeParse(oldId, relid, confrelid, InvalidOid,
 							 (char *) lfirst(def_item),
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 5e8e1683db0..d48c3383ea6 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -2772,6 +2772,7 @@ pg_get_expr_worker(text *expr, Oid relid, int prettyFlags)
 		rel = try_relation_open(relid, AccessShareLock);
 		if (rel == NULL)
 			return NULL;
+if (strcmp(RelationGetRelationName(rel), "atref") == 0) pg_usleep(2000000);
 		context = deparse_context_for(RelationGetRelationName(rel), relid);
 	}
 	else
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 20707c186b3..aba2f363945 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -4801,6 +4801,12 @@ drop table attbl, atref;
 /* Test case for bug #18970 */
 create table attbl(a int);
 create table atref(b attbl check ((b).a is not null));
+SELECT pg_sleep(2);
+ pg_sleep 
+----------
+ 
+(1 row)
+
 alter table attbl alter column a type numeric;  -- someday this should work
 ERROR:  cannot alter table "attbl" because column "atref.b" uses its row type
 alter table atref drop constraint atref_b_check;
diff --git a/src/test/regress/expected/domain.out b/src/test/regress/expected/domain.out
index 62a48a523a2..c0b9af6124a 100644
--- a/src/test/regress/expected/domain.out
+++ b/src/test/regress/expected/domain.out
@@ -1412,6 +1412,12 @@ SELECT * FROM information_schema.domains
  regression     | public        | things      | integer   |                          |                        |                       |                      |                    |                   |                  |                |                32 |                       2 |             0 |                    |               |                    |                | regression  | pg_catalog | int4     |               |              |            |                     | 1
 (4 rows)
 
+SELECT pg_sleep(3);
+ pg_sleep 
+----------
+ 
+(1 row)
+
 SELECT * FROM information_schema.check_constraints
   WHERE (constraint_schema, constraint_name)
         IN (SELECT constraint_schema, constraint_name
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 18f3fdac57a..a3bef2c8066 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -3118,6 +3118,7 @@ drop table attbl, atref;
 
 create table attbl(a int);
 create table atref(b attbl check ((b).a is not null));
+SELECT pg_sleep(2);
 alter table attbl alter column a type numeric;  -- someday this should work
 alter table atref drop constraint atref_b_check;
 
diff --git a/src/test/regress/sql/domain.sql b/src/test/regress/sql/domain.sql
index b8f5a639712..58ce83c864f 100644
--- a/src/test/regress/sql/domain.sql
+++ b/src/test/regress/sql/domain.sql
@@ -910,6 +910,7 @@ SELECT * FROM information_schema.domains
   WHERE domain_name IN ('con', 'dom', 'pos_int', 'things')
   ORDER BY domain_name;
 
+SELECT pg_sleep(3);
 SELECT * FROM information_schema.check_constraints
   WHERE (constraint_schema, constraint_name)
         IN (SELECT constraint_schema, constraint_name