Not enough memory for complex join

Hello!

A week ago I reported this, but haven't got any good help. I am trying
to repeat.

Postgres 6.4.2 on Solaris. Query:
SELECT p.subsec_id
FROM positions p, central cn, shops sh, districts d
WHERE cn.pos_id = p.pos_id AND d.city_id = 2
AND cn.shop_id = sh.shop_id AND sh.distr_id = d.distr_id
AND cn.date_i >= current_date - '7 days'::timespan

I am not publishing here my tables, but the structure is obvious. There
is central database, which only knows shop_id, and shop only knows its
district, and district knows city. I want to count distinct p.subsec_id for
one city.
With the query, postgres eats all memory and dies.

I played with the query, and found I can remove (AND d.city_id = 2). The
query executes pretty fast (my database is small). I tried to get
d.city_id:

SELECT p.subsec_id, d.city_id
FROM positions p, central cn, shops sh, districts d
WHERE cn.pos_id = p.pos_id
AND cn.shop_id = sh.shop_id AND sh.distr_id = d.distr_id
AND cn.date_i >= current_date - '7 days'::timespan

but postgres eats all memory and dies :(((

Memory leak? Other bugs?

Oleg.
----
Oleg Broytmann http://members.xoom.com/phd2/ phd2(at)earthling(dot)net
Programmers don't die, they just GOSUB without RETURN.