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Re: Measuring relation free space

From: Jaime Casanova <jaime(at)2ndquadrant(dot)com>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: Bernd Helmle <mailings(at)oopsware(dot)de>, Greg Smith <greg(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Measuring relation free space
Date: 2012-01-21 00:03:22
Message-ID: CAJKUy5jzVzt1097v2u_Jk0PuLdgSf3p12WOpXBCKPSw=Gach_w@mail.gmail.com (view raw or flat)
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Lists: pgsql-hackers
On Wed, Jan 18, 2012 at 7:01 PM, Noah Misch <noah(at)leadboat(dot)com> wrote:
> On Wed, Jan 18, 2012 at 09:46:20AM -0500, Jaime Casanova wrote:
>>
>> ignoring all non-leaf pages still gives a considerable difference
>> between pgstattuple and relation_free_space()
>
> pgstattuple() counts the single B-tree meta page as always-full, while
> relation_free_space() skips it for all purposes.  For tiny indexes, that can
> shift the percentage dramatically.
>

ok, i will reformulate the question. why is fine ignoring non-leaf
pages but is not fine to ignore the meta page?

-- 
Jaime Casanova         www.2ndQuadrant.com
Professional PostgreSQL: Soporte 24x7 y capacitación

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