memory leaks? using savepoint

Hi!

When I tested simple query as following, backend process used much memory
and not freed until the backend was finished.
# This is reproduced on PostgreSQL8.3 (PostgreSQL8.3.6 - PostgreSQL8.3.12)

-------
BEGIN;
SAVEPOINT sp0;
INSERT INTO tbl VALUES (1);
RELEASE sp0;
SAVEPOINT sp1;
INSERT INTO tbl VALUES (1);
RELEASE sp1;
(repeats 10k)
ROLLBACK;
SELECT pg_sleep(10000);
-------

I think this caused by following fix.
http://archives.postgresql.org/pgsql-committers/2008-12/msg00100.php
http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c?r1=1.560&r2=1.561)

Should "CopySnapshot()" be performed in MessageContext ?
Attached simple pathch to solve it...

Best regards,
--
NTT OSS Center
Tatsuhito Kasahara
kasahara(dot)tatsuhito(at)oss(dot)ntt(dot)co(dot)jp