Re: Proposal: Log inability to lock pages during vacuum

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Greg Stark <stark(at)mit(dot)edu>
Cc: Andres Freund <andres(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Proposal: Log inability to lock pages during vacuum
Date: 2014-11-07 13:32:03
Message-ID: 20141107133203.GN1791@alvin.alvh.no-ip.org
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Greg Stark wrote:

> I agree bloat isn't really a threat, but what about the relfrozenxid?
> If we skip even one page we don't get to advance it and retrying could
> eliminate those skipped pages and allow us to avoid a vacuum freeze
> which can be really painful. Of course that only works if you can be
> sure you haven't overflowed and forgotten any skipped pages and if you
> don't find the page still pinned every time until you eventually give
> up on it.

We never advance relfrozenxid nowadays unless it's a whole-table scan;
and once we commit to doing those (vacuum_freeze_table_age is past), we
don't skip pages anymore.

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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