From: | "Chad Thompson" <chad(at)weblinkservices(dot)com> |
---|---|
To: | "Max Baker" <max(at)warped(dot)org>, "PostgreSQL Performance Mailing List" <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: speeding up COUNT and DISTINCT queries |
Date: | 2003-03-12 22:55:09 |
Message-ID: | 0ca601c2e8ea$6f7783d0$32021aac@chad |
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Lists: | pgsql-performance |
Ive found that group by works faster than distinct.
Try
EXPLAIN ANALYZE select mac from node group by mac;
HTH
Chad
----- Original Message -----
From: "Max Baker" <max(at)warped(dot)org>
To: "PostgreSQL Performance Mailing List" <pgsql-performance(at)postgresql(dot)org>
Sent: Wednesday, March 12, 2003 3:38 PM
Subject: [PERFORM] speeding up COUNT and DISTINCT queries
> I'm looking for a general method to
> speed up DISTINCT and COUNT queries.
>
>
> mydatabase=> EXPLAIN ANALYZE select distinct(mac) from node;
> NOTICE: QUERY PLAN:
>
> Unique (cost=110425.67..110514.57 rows=3556 width=6) (actual
> time=45289.78..45598.62 rows=25334 loops=1)
> -> Sort (cost=110425.67..110425.67 rows=35561 width=6) (actual
> time=45289.77..45411.53 rows=34597 loops=1)
> -> Seq Scan on node (cost=0.00..107737.61 rows=35561
> width=6) (actual time=6.73..44383.57 rows=34597 loops=1)
>
> Total runtime: 45673.19 msec
> ouch.
>
> I run VACCUUM ANALYZE once a day.
>
> Thanks,
> max
>
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