Date: Wed, 26 Jun 2013 15:48:04 -0500
From: "ktm@rice.edu" <ktm@rice.edu>
To: Willy-Bas Loos <willybas@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>,
 Scott Marlowe <scott.marlowe@gmail.com>,
 "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: seqscan for 100 out of 3M rows, index present
Message-ID: <20130626204804.GC3264@aart.rice.edu>
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On Wed, Jun 26, 2013 at 10:36:10PM +0200, Willy-Bas Loos wrote:
> On Wed, Jun 26, 2013 at 10:31 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
> 
> >
> > Why is it retrieving 3.1 million, when it only needs 17?
> >
> >
> > that's because of the sequential scan, it reads all the data.
> 
> cheers,
> 
> willy-bas

Well, the two plans timings were pretty close together. Maybe your
cost model is off. Try adjusting the various cost parameters to
favor random I/O more.

Regards,
Ken


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