3 files changed, 36 insertions, 13 deletions
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 89bc865e287..23364d3c7ec 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12183,12 +12183,11 @@ ATPrepAlterColumnType(List **wqueue,
 				 errmsg("\"%s\" is not a table",
 						RelationGetRelationName(rel))));
 
-	if (tab->relkind == RELKIND_COMPOSITE_TYPE ||
-		tab->relkind == RELKIND_FOREIGN_TABLE)
+	if (!RELKIND_HAS_STORAGE(tab->relkind))
 	{
 		/*
-		 * For composite types and foreign tables, do this check now.  Regular
-		 * tables will check it later when the table is being rewritten.
+		 * For relations without storage, do this check now.  Regular tables
+		 * will check it later when the table is being rewritten.
 		 */
 		find_composite_type_dependencies(rel->rd_rel->reltype, rel, NULL);
 	}
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 24d1c7cd280..16e04756634 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -2061,11 +2061,24 @@ begin;
 create table skip_wal_skip_rewrite_index (c varchar(10) primary key);
 alter table skip_wal_skip_rewrite_index alter c type varchar(20);
 commit;
--- table's row type
-create table tab1 (a int, b text);
-create table tab2 (x int, y tab1);
-alter table tab1 alter column b type varchar; -- fails
-ERROR:  cannot alter table "tab1" because column "tab2.y" uses its row type
+-- We disallow changing table's row type if it's used for storage
+create table at_tab1 (a int, b text);
+create table at_tab2 (x int, y at_tab1);
+alter table at_tab1 alter column b type varchar; -- fails
+ERROR:  cannot alter table "at_tab1" because column "at_tab2.y" uses its row type
+drop table at_tab2;
+-- Use of row type in an expression is defended differently
+create table at_tab2 (x int, y text, check((x,y)::at_tab1 = (1,'42')::at_tab1));
+alter table at_tab1 alter column b type varchar; -- allowed, but ...
+insert into at_tab2 values(1,'42'); -- ... this will fail
+ERROR:  ROW() column has type text instead of type character varying
+drop table at_tab1, at_tab2;
+-- Check it for a partitioned table, too
+create table at_tab1 (a int, b text) partition by list(a);
+create table at_tab2 (x int, y at_tab1);
+alter table at_tab1 alter column b type varchar; -- fails
+ERROR:  cannot alter table "at_tab1" because column "at_tab2.y" uses its row type
+drop table at_tab1, at_tab2;
 -- Alter column type that's part of a partitioned index
 create table at_partitioned (a int, b text) partition by range (a);
 create table at_part_1 partition of at_partitioned for values from (0) to (1000);
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 5fac2585d90..ac894c0602c 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -1420,10 +1420,21 @@ create table skip_wal_skip_rewrite_index (c varchar(10) primary key);
 alter table skip_wal_skip_rewrite_index alter c type varchar(20);
 commit;
 
--- table's row type
-create table tab1 (a int, b text);
-create table tab2 (x int, y tab1);
-alter table tab1 alter column b type varchar; -- fails
+-- We disallow changing table's row type if it's used for storage
+create table at_tab1 (a int, b text);
+create table at_tab2 (x int, y at_tab1);
+alter table at_tab1 alter column b type varchar; -- fails
+drop table at_tab2;
+-- Use of row type in an expression is defended differently
+create table at_tab2 (x int, y text, check((x,y)::at_tab1 = (1,'42')::at_tab1));
+alter table at_tab1 alter column b type varchar; -- allowed, but ...
+insert into at_tab2 values(1,'42'); -- ... this will fail
+drop table at_tab1, at_tab2;
+-- Check it for a partitioned table, too
+create table at_tab1 (a int, b text) partition by list(a);
+create table at_tab2 (x int, y at_tab1);
+alter table at_tab1 alter column b type varchar; -- fails
+drop table at_tab1, at_tab2;
 
 -- Alter column type that's part of a partitioned index
 create table at_partitioned (a int, b text) partition by range (a);