out of memory problem in CVS

hi,
we are using postgresql to analyze our web log, we got a 6M table,
and while doing the query:

SELECT url,sum(ct) as ctperkw from ctrraw group by url order by ctperkw
desc limit 1000;

the table structure is:

CREATE TABLE ctrRAW
(
cdate date,
ip inet,
kw varchar(128),
prd varchar(6),
pos int,
url varchar(512),
ct int
);

create INDEX ctr_ip_index on ctrraw(ip);

our boxes ia a freebsd 4.1 with 2G emmory, but our postgresql user got
a 512M data sigment ulimit.

and the query run out of memory, the log file attached.

the postgresql was check out from CVS around June 25.
we are going to test in newly checkout CVS tip, but want to report here
first.

regards laser