Re: speeding up COUNT and DISTINCT queries

From: Jean-Luc Lachance <jllachan(at)nsd(dot)ca>
To: Max Baker <max(at)warped(dot)org>
Cc: PostgreSQL Performance Mailing List <pgsql-performance(at)postgresql(dot)org>
Subject: Re: speeding up COUNT and DISTINCT queries
Date: 2003-03-12 23:40:36
Message-ID: 3E6FC574.F15D9930@nsd.ca
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Do you have an index on mac?

Max Baker wrote:
>
> 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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