hash partitioning

Hi folks,

I'm wondering why the postgres planner is not capable of determining the
correct partition for a simple select for the following partitioning scheme,
in which I'd like to automatically divide rows into four sub-tables, ie, a
simple form of hash partitioning.

Any ideas why this doesn't work, or a work around to make it work? I would
have expected the query plan below to only query the test_1 table.

Regards

David

CREATE TABLE test (

id int not null primary key

);

CREATE TABLE test_0 ( CHECK ( id % 4 = 0) ) INHERITS (test);

CREATE TABLE test_1 ( CHECK ( id % 4 = 1) ) INHERITS (test);

CREATE TABLE test_2 ( CHECK ( id % 4 = 2) ) INHERITS (test);

CREATE TABLE test_3 ( CHECK ( id % 4 = 3) ) INHERITS (test);

CREATE RULE test_0 AS ON INSERT TO test WHERE ( id % 4 = 0 ) DO INSTEAD
INSERT INTO test_0 VALUES ( NEW.id );

CREATE RULE test_1 AS ON INSERT TO test WHERE ( id % 4 = 1 ) DO INSTEAD
INSERT INTO test_1 VALUES ( NEW.id );

CREATE RULE test_2 AS ON INSERT TO test WHERE ( id % 4 = 2 ) DO INSTEAD
INSERT INTO test_2 VALUES ( NEW.id );

CREATE RULE test_3 AS ON INSERT TO test WHERE ( id % 4 = 3 ) DO INSTEAD
INSERT INTO test_3 VALUES ( NEW.id );

insert into test values(1);

explain analyse select * from test;

"Result (cost=0.00..170.00 rows=12000 width=4) (actual time=0.027..0.042
rows=1 loops=1)"

" -> Append (cost=0.00..170.00 rows=12000 width=4) (actual
time=0.020..0.032 rows=1 loops=1)"

" -> Seq Scan on test (cost=0.00..34.00 rows=2400 width=4) (actual
time=0.002..0.002 rows=0 loops=1)"

" -> Seq Scan on test_0 test (cost=0.00..34.00 rows=2400 width=4)
(actual time=0.001..0.001 rows=0 loops=1)"

" -> Seq Scan on test_1 test (cost=0.00..34.00 rows=2400 width=4)
(actual time=0.007..0.009 rows=1 loops=1)"

" -> Seq Scan on test_2 test (cost=0.00..34.00 rows=2400 width=4)
(actual time=0.001..0.001 rows=0 loops=1)"

" -> Seq Scan on test_3 test (cost=0.00..34.00 rows=2400 width=4)
(actual time=0.001..0.001 rows=0 loops=1)"

"Total runtime: 0.115 ms"