Re: Measuring relation free space

Jaime Casanova <jaime@2ndquadrant.com>

From: Jaime Casanova <jaime@2ndquadrant.com>

To: Noah Misch <noah@leadboat.com>

Cc: Bernd Helmle <mailings@oopsware.de>, Greg Smith <greg@2ndquadrant.com>, pgsql-hackers@postgresql.org

Date: 2012-01-21T00:03:22Z

Lists: pgsql-hackers

On Wed, Jan 18, 2012 at 7:01 PM, Noah Misch <noah@leadboat.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