On Fri, 2002-12-06 at 14:46, Tom Lane wrote:
> "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.
Hi.
What exactly is "hashed aggregation"?
From Josh Berkus' email with the EXPLAIN data, it still looks like
supporting indexes aren't used, so are you still scanning the table?
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