[BUG?] strange behavior in ALTER TABLE ... RENAME TO on inherited columns

Is it an expected behavior?

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

The t3.d is inherited from t1 and t2. Its attinhcount is 2.

postgres=# ALTER TABLE t1 RENAME b TO x;
ALTER TABLE

It alters name of the column 'b' in the t1 and its child tables ('t3').

postgres=# SELECT * FROM t1;
a | x
---+---
(0 rows)

postgres=# SELECT * FROM t2;
ERROR: could not find inherited attribute "b" of relation "t3"

Because t3.b is also inherited from the t2, but ALTER TABLE does not
care about multiple inherited columns well.

I think we should not allow to rename a column with attinhcount > 1.

Any comments?

Thanks,
--
OSS Platform Development Division, NEC
KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>