Re: Speeding up aggregates

"Josh Berkus" <josh@agliodbs.com> writes:
> What have other Postgres users done to speed up aggregates on large
> tables?

FWIW, I've implemented hashed aggregation in CVS tip.  I have not had
the time to try to benchmark it, but I'd be interested if anyone can
run some tests on 7.4devel.  Eliminating the need for a SORT step
should help aggregations over large datasets.

Note that even though there's no SORT, the sort_mem setting is used
to determine the allowable hashtable size, so a too-small sort_mem
might discourage the planner from selecting hashed aggregation.
Use EXPLAIN to see which query plan gets chosen.

            regards, tom lane