| From: | "ktm(at)rice(dot)edu" <ktm(at)rice(dot)edu> |
|---|---|
| To: | Willy-Bas Loos <willybas(at)gmail(dot)com> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: seqscan for 100 out of 3M rows, index present |
| Date: | 2013-06-26 20:48:04 |
| Message-ID: | 20130626204804.GC3264@aart.rice.edu |
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| Thread: | |
| Lists: | pgsql-performance |
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(dot)janes(at)gmail(dot)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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