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 ac17018d111248a964522264270f3c4c966098fd..6b82d32ba15ac2d17addaf4b8933943e62de9be9 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -11317,12 +11317,11 @@ 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, do this check now.  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 d54c7e3ffb3c23aa81611d217c3e35ff979d484c..df9c5ffd9475c11de84f78826085f6737e2df61e 100644 (file)
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -2063,11 +2063,24 @@ 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 42ec7347044dd7591d83c4d988c7d96ebf5ae5cd..4884476c3af423feb3002c5dbafcf8e628d21a54 100644 (file)
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -1424,10 +1424,21 @@ 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);