Re: Worse perfomance on 8.2.0 than on 7.4.14 - Mailing list pgsql-performance

From Rolf Østvik
Subject Re: Worse perfomance on 8.2.0 than on 7.4.14
Date
Msg-id 20070101151905.55545.qmail@web26309.mail.ukl.yahoo.com
Whole thread Raw
In response to Re: Worse perfomance on 8.2.0 than on 7.4.14  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-performance
--- Tom Lane <tgl@sss.pgh.pa.us> skrev:

> Rolf =?iso-8859-1?q?=D8stvik?= <rolfostvik@yahoo.no>
> writes:
> > I have a simple query which uses 32ms on 7.4.14
> and 1015ms on 8.2.0.
>
> There's something awfully strange about that 8.2
> plan --- if it knew
> that it'd have to scan all of uut_result_subset
> (which it should have
> known, if the stats were up-to-date),

I can't really see the need for it to do an sequence
scan, but that is me not knowing how things work.

>why did it use
> an indexscan
> rather than a seqscan?  Are you sure you haven't
> tweaked any parameters
> you didn't tell us about, such as setting
> enable_seqscan = off?

I haven't touched enable_seqscan.
It could be that i have forgotton to tell you about a
parameter i have tweaked, but i doubt it.

Best regards
Rolf Østvik

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