Re: Hash aggregates blowing out memory

Mike Harding <mvh@ix.netcom.com> writes:
> I've been having problems where a HashAggregate is used because of a bad
> estimate of the distinct number of elements involved.

If you're desperate, there's always enable_hashagg.  Or reduce sort_mem
enough so that even the misestimate looks like it will exceed sort_mem.

In the long run it would be nice if HashAgg could spill to disk.  We
were expecting to see a contribution of code along that line last year
(from the CMU/Berkeley database class) but it never showed up.  The
performance implications might be a bit grim anyway :-(

            regards, tom lane