From: Michal Taborsky - Internet Mall <michal.taborsky@mall.cz>
To: Markus Schaber <schabi@logix-tt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Identifying bloated tables
Date: Mon, 28 Aug 2006 17:56:08 +0200
Message-ID: <44F31218.6040703@mall.cz> (raw)
In-Reply-To: <44F31088.5040602@logix-tt.com>
References: <44F30022.1000009@mall.cz>
<44F31088.5040602@logix-tt.com>
Markus Schaber napsal(a):
> Hi, Michal,
>
> Michal Taborsky - Internet Mall wrote:
>
>> When using this view, you are interested in tables, which have the
>> "bloat" column higher that say 2.0 (in freshly dump/restored/analyzed
>> database they should all be around 1.0).
>
> I just noticed some columns in pg_catalog with a bloat value <1 and a
> negative "wasted space" - is this due to the pseudo nature of them?
It is more likely due to the fact, that these numbers are just
estimates, based on collected table statistics, so for small or
non-standard tables the statistical error is greater that the actual
value. You are usually not interested in tables, which have wasted space
of 1000kB or -1000kB. Also the database must be ANALYZEd properly for
these numbers to carry any significance.
--
Michal Táborský
IT operations chief
Internet Mall, a.s.
Internet Mall - obchody, které si oblíbíte
<http://www.MALL.cz;
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To: pgsql-performance@postgresql.org
Cc: michal.taborsky@mall.cz, schabi@logix-tt.com
Subject: Re: Identifying bloated tables
In-Reply-To: <44F31218.6040703@mall.cz>
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