From: Andreas Joseph Krogh <andreak@officenet.no>
Organization: OfficeNet AS
To: Richard Huxton <dev@archonet.com>
Subject: Re: row-attribute in EXPLAIN-output doesn't match count(*)
Date: Thu, 14 Apr 2005 19:21:38 +0200
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References: <200504141838.14705.andreak@officenet.no>
	<425EA496.2030501@archonet.com>
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On Thursday 14 April 2005 19:12, Richard Huxton wrote:
> Andreas Joseph Krogh wrote:
> > Hi everybody, I have table which inly has 298 rows in it, but EXPLAIN
> > ANALYZE shows that PG thinks it has as much as 160057 rows AFAICT from
> > the EXPLAIN-output.
> >
> >
> >  I've just run a "VACUUM FULL VERBOSE" on the whole database, which gave
> > the following output on the relevant table(onp_web_index):
> >
> > INFO:  vacuuming "public.onp_web_index"
> > INFO:  "onp_web_index": found 0 removable, 160057 nonremovable row
> > versions in 206940 pages
> > DETAIL:  159759 dead row versions cannot be removed yet.
>
> A long-lived transaction can still see these row versions, so vacuum
> can't delete them. Until that transaction is committed/rolled back PG
> has to keep the old versions of those rows available, because it might
> be able to see them.
>
> So - do you have an application/client that has had a single transaction
> open for a long time. A very long time unless you update this table a lot.

Hm, it's a web-app, and I don't hold a transaction open for a long time on=
=20
purpose, but I have a line which says "idle in transaction" fromn "ps":

postgres  2754  1646  0 Apr06 ?        00:00:07 postgres: nbe nbeweb 127.0.=
0.1=20
idle in transaction

And by the way, I lied about the PG-version, it's 7.4.5, not 8.0.0

So, what you're suggesting is that a restart of the webapp should make vacu=
um=20
able to delete those dead rows?

=2D-=20
Andreas Joseph Krogh <andreak@officenet.no>
Senior Software Developer / Manager
gpg public_key: http://dev.officenet.no/~andreak/public_key.asc
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