Date: Mon, 26 Mar 2018 17:24:25 +0200
From: hubert depesz lubaczewski <depesz@depesz.com>
Sender: depesz@depesz.com
To: Artem Tomyuk <admin@leboutique.com>
Cc: Keith <keith@keithf4.com>, pgsql-admin <pgsql-admin@postgresql.org>
Subject: Re: how to shrink pg_attribute table in some database
Message-ID: <20180326152425.GA23643@depesz.com>
Reply-To: depesz@depesz.com
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On Mon, Mar 26, 2018 at 05:33:19PM +0300, Artem Tomyuk wrote:
> Can't, it generates huge IO spikes.
> 
> But....
> 
> Few hours ago i manually started vacuum verbose on pg_attribute, now its
> finished and i have some outputs:
> 
> INFO: "pg_attribute": found 554728466 removable, 212058 nonremovable row
> versions in 44550921 out of 49326696 pages DETAIL: 178215 dead row versions
> cannot be removed yet. There were 53479 unused item pointers. 0 pages are
> entirely empty. CPU 1097.53s/1949.50u sec elapsed 6337.86 sec. Query
> returned successfully with no result in 01:47:3626 hours.
> 
> what do you think?
> 
> select count(*) on pg_attribute returns:
> 158340 rows
> 
> So as i understand vacuum full will create new pg_attribute and will wrote
> those amount of "valid" rows, but still it will scan 300GB old table?
> So estimate will be even ~same compering with regular vacuum?

more or less, yes.

the thing is - find and fix whatever is causing this insane churn of
tables/attributes.

Best regards,

depesz