From: Tom Lane <tgl@sss.pgh.pa.us>
To: arnaulist@andromeiberica.com
Cc: chris smith <dmagick@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Query on postgresql 7.4.2 not using index
Date: Tue, 25 Apr 2006 11:22:59 -0400
Message-ID: <19483.1145978579@sss.pgh.pa.us> (raw)
In-Reply-To: <444E28ED.3090900@andromeiberica.com>
References: <444E240D.3050000@andromeiberica.com>
<3c1395330604250634r6f215ceame157f3dd5f5f4fa3@mail.gmail.com>
<444E28ED.3090900@andromeiberica.com>
Arnau <arnaulist@andromeiberica.com> writes:
> Seq Scan on agenda_users_groups (cost=0.00..53108.45 rows=339675
> width=8) (actual time=916.903..5763.830 rows=367026 loops=1)
> Filter: (group_id = 9::numeric)
> Total runtime: 7259.861 ms
> (3 filas)
> espsm_moviltelevision=# select count(*) from agenda_users_groups ;
> count
> ---------
> 2547556
So the SELECT is fetching nearly 15% of the rows in the table. The
planner is doing *the right thing* to use a seqscan, at least for
this particular group_id value.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, arnaulist@andromeiberica.com, dmagick@gmail.com
Subject: Re: Query on postgresql 7.4.2 not using index
In-Reply-To: <19483.1145978579@sss.pgh.pa.us>
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