From: Guillaume Cottenceau <gc@mnc.ch>
To: Franck Routier <franck.routier@axege.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Postgresql performance degrading... how to diagnose the root
 cause
References: <5155A33A.4090000@axege.com> <m3hajudzv1.fsf@mnc.ch>
	<5155B3BB.4080209@axege.com>
Date: Sat, 30 Mar 2013 01:02:55 +0100
In-Reply-To: <5155B3BB.4080209@axege.com> (Franck Routier's message of "Fri,
	29 Mar 2013 16:31:07 +0100")
Message-ID: <m3a9pleouo.fsf@mnc.ch>
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Franck Routier <franck.routier 'at' axege.com> writes:

>> http://wiki.postgresql.org/wiki/Show_database_bloat
> How do I interpret the output of this query ? Is 1.1 bloat level on a
> table alarming, or quite ok ?

I am not very used to this, but I'd start by comparing the top
result in your established DB against the top result in your
fresh DB. What does it say? The wiki page says it is a loose
estimate, however, unusually larger tbloat and/or wastedbytes
might be an indication.

Of course, if you can afford it, a good old VACUUM FULL ANALYZE
VERBOSE would tell you how many pages were reclaimed while
rewriting the table. Otherwise, VACUUM VERBOSE on both the
established DB and a backup/restore on a fresh DB also provide a
helpful comparison of how many pages are used for suspected
tables.

-- 
Guillaume Cottenceau


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