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Re: freezing multixacts

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: freezing multixacts
Date: 2012-02-06 15:57:30
Message-ID: CA+U5nMJudDzPQZ=9tRKvvVZYuWm8UnxO_VNF9=tJYRp=8LeoXA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Feb 2, 2012 at 4:33 AM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:

> However, there are cases where not even that is possible -- consider
> tuple freezing during WAL recovery.  Recovery is going to need to
> replace those multis with other multis, but it cannot create new multis
> itself.  The only solution here appears to be that when multis are
> frozen in the master, replacement multis have to be logged too.  So the
> heap_freeze_tuple Xlog record will have a map of old multi to new.  That
> way, recovery can just determine the new multi to use for any particular
> old multi; since multixact creation is also logged, we're certain that
> the replacement value has already been defined.

Multixacts are ignored during recovery. Why do anything at all?

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

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