[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"
CREATETABLE
 

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@ak.jp.nec.com>