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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 (view raw or flat)
Thread:
Lists: pgsql-performance
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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Subject: Re: speeding up COUNT and DISTINCT queries
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