Prevent altering partitioned table's rowtype, if it's used elsewhere.

We disallow altering a column datatype within a regular table,
if the table's rowtype is used as a column type elsewhere,
because we lack code to go around and rewrite the other tables.
This restriction should apply to partitioned tables as well, but it
was not checked because ATRewriteTables and ATPrepAlterColumnType
were not on the same page about who should do it for which relkinds.

Per bug #17351 from Alexander Lakhin.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/17351-6db1870f3f4f612a@postgresql.org

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 89bc865e287ad66086951029f06a75a6d78434a7..23364d3c7ec52d0cd9824dd21735e5f11ac2e8b0 100644 (file)
--- 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 24d1c7cd280beeaed1198cd6fbca4c7489815a9b..16e047566341acb632e356e09c94826cb3590d5b 100644 (file)
--- 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 5fac2585d90e609093a8bd77cc8fb0bfe8722473..ac894c0602c6a31e657a45654c978ef87322e33d 100644 (file)
--- 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);