From: | Sean Chittenden <sean(at)chittenden(dot)org> |
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To: | Neil Conway <neilc(at)samurai(dot)com> |
Cc: | logan(at)datacurrent(dot)com, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: postgresql meltdown on PlanetMath.org |
Date: | 2003-03-17 06:29:29 |
Message-ID: | 20030317062929.GI23355@perrin.int.nxad.com |
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Thread: | |
Lists: | pgsql-performance |
> >> A "select count(*) FROM tblwordidx" initially took about 1 second to
> >> return a count of 2 million but after a few months it took several
> >> minutes of really hard HDD grinding.
> >
> > That's because there are dead entries in the index that weren't being
> > reused or cleaned up. As I said, this has been fixed.
>
> That's doubtful: "select count(*) FROM foo" won't use an
> index. There are a bunch of other factors (e.g. dead heap tuples,
> changes in the pages cached in the buffer, disk fragmentation, etc.)
> that could effect performance in that situation, however.
*blush* Yeah, jumped the gun on that when I read that queries were
getting slower (churn of an index == slow creaping death for
performance). A SELECT COUNT(*), however, wouldn't be affected by the
index growth problem. Is the COUNT() on a view that uses an index? I
haven't had any real problems with this kind of degredation outside of
indexes. :-/ -sc
--
Sean Chittenden
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