Tom Lane wrote:
> Thom Brown <thombr...@gmail.com> writes:
>> 2009/11/4 Alvaro Herrera <alvhe...@commandprompt.com>:
>>> KaiGai Kohei wrote:
>>>> I think we should not allow to rename a column with attinhcount > 1.
>
>>> I think we should fix ALTER TABLE to cope with multiple inheritance.
>
>> I'd be interested to see how this should work.
>
> Yeah. I don't think a "fix" is possible, because there is no
> non-astonishing way for it to behave. I think KaiGai is right that
> forbidding the rename is the best solution.
The attached patch forbids rename when the attribute is inherited
from multiple parents.
postgres=# CREATE TABLE t1 (a int, b int);
CREATE TABLE
postgres=# CREATE TABLE t2 (b int, c int);
CREATE TABLE
postgres=# CREATE TABLE t3 (d int) INHERITS (t1, t2);
NOTICE: merging multiple inherited definitions of column "b"
CREATE TABLE
postgres=# SELECT * FROM t3;
a | b | c | d
---+---+---+---
(0 rows)
postgres=# ALTER TABLE t1 RENAME b TO x;
ERROR: cannot rename multiple inherited column "b"
The regression test detected a matter in the misc test.
It tries to rename column "a" of "a_star" table, but it failed due to
the new restriction.
--
-- test the "star" operators a bit more thoroughly -- this time,
-- throw in lots of NULL fields...
--
-- a is the type root
-- b and c inherit from a (one-level single inheritance)
-- d inherits from b and c (two-level multiple inheritance)
-- e inherits from c (two-level single inheritance)
-- f inherits from e (three-level single inheritance)
--
CREATE TABLE a_star (
class char,
a int4
);
CREATE TABLE b_star (
b text
) INHERITS (a_star);
CREATE TABLE c_star (
c name
) INHERITS (a_star);
CREATE TABLE d_star (
d float8
) INHERITS (b_star, c_star);
At the misc test,
--- 242,278 ----
ALTER TABLE c_star* RENAME COLUMN c TO cc;
ALTER TABLE b_star* RENAME COLUMN b TO bb;
ALTER TABLE a_star* RENAME COLUMN a TO aa;
+ ERROR: cannot rename multiple inherited column "a"
SELECT class, aa
FROM a_star* x
WHERE aa ISNULL;
! ERROR: column "aa" does not exist
! LINE 1: SELECT class, aa
!
It seems to me it is a case the regression test to be fixed up.
(We don't have any reasonable way to know whether a certain attribute
has a same source, or not.)
Any comments?
--
OSS Platform Development Division, NEC
KaiGai Kohei <kai...@ak.jp.nec.com>
Index: src/test/regress/sql/inherit.sql
===================================================================
*** src/test/regress/sql/inherit.sql (revision 2388)
--- src/test/regress/sql/inherit.sql (working copy)
*************** CREATE TABLE inh_error1 () INHERITS (t1,
*** 336,338 ****
--- 336,352 ----
CREATE TABLE inh_error2 (LIKE t4 INCLUDING STORAGE) INHERITS (t1);
DROP TABLE t1, t2, t3, t4, t12_storage, t12_comments, t1_inh, t13_inh, t13_like, t_all;
+
+ -- Test for renaming
+ CREATE TABLE t1 (a int, b int);
+ CREATE TABLE t2 (b int, c int);
+ CREATE TABLE t3 (d int) INHERITS(t1, t2);
+ ALTER TABLE t1 RENAME a TO x;
+ ALTER TABLE t1 RENAME b TO y; -- to be failed
+ ALTER TABLE t3 RENAME d TO z;
+ SELECT * FROM t3;
+ DROP TABLE t3;
+ DROP TABLE t2;
+ DROP TABLE t1;
+
+
Index: src/test/regress/expected/inherit.out
===================================================================
*** src/test/regress/expected/inherit.out (revision 2388)
--- src/test/regress/expected/inherit.out (working copy)
*************** NOTICE: merging column "a" with inherit
*** 1057,1059 ****
--- 1057,1076 ----
ERROR: column "a" has a storage parameter conflict
DETAIL: MAIN versus EXTENDED
DROP TABLE t1, t2, t3, t4, t12_storage, t12_comments, t1_inh, t13_inh, t13_like, t_all;
+ -- Test for renaming
+ CREATE TABLE t1 (a int, b int);
+ CREATE TABLE t2 (b int, c int);
+ CREATE TABLE t3 (d int) INHERITS(t1, t2);
+ NOTICE: merging multiple inherited definitions of column "b"
+ ALTER TABLE t1 RENAME a TO x;
+ ALTER TABLE t1 RENAME b TO y; -- to be failed
+ ERROR: cannot rename multiple inherited column "b"
+ ALTER TABLE t3 RENAME d TO z;
+ SELECT * FROM t3;
+ x | b | c | z
+ ---+---+---+---
+ (0 rows)
+
+ DROP TABLE t3;
+ DROP TABLE t2;
+ DROP TABLE t1;
Index: src/backend/commands/tablecmds.c
===================================================================
*** src/backend/commands/tablecmds.c (revision 2388)
--- src/backend/commands/tablecmds.c (working copy)
*************** renameatt(Oid myrelid,
*** 2024,2029 ****
--- 2024,2040 ----
errmsg("cannot rename inherited column \"%s\"",
oldattname)));
+ /*
+ * If the attribute is inherited from multiple parents, forbid
+ * the renaming, because we don't have any reasonable way to keep
+ * integrity in whole of the inheritance relationship.
+ */
+ if (attform->attinhcount > 1)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+ (errmsg("cannot rename multiple inherited column \"%s\"",
+ oldattname))));
+
/* should not already exist */
/* this test is deliberately not attisdropped-aware */
if (SearchSysCacheExists(ATTNAME,
--
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