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Cc: Ray Stell <stellr@cns.vt.edu>, pgsql-admin <pgsql-admin@postgresql.org>
Subject: Re: could not truncate directory "pg_subtrans": apparent wraparound
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Mikko Partio <mpartio@gmail.com>
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Date: Thu, 20 May 2010 12:53:22 -0400
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Excerpts from Mikko Partio's message of jue may 20 00:39:00 -0400 2010:
> On Wed, May 19, 2010 at 3:21 PM, Ray Stell <stellr@cns.vt.edu> wrote:

> > http://archives.postgresql.org/pgsql-general/2007-06/msg01050.php
> 
> Browsing through that thread I can see that I have similar symptoms:
> 
> $ pg_controldata | grep Multi
> Latest checkpoint's NextMultiXactId:  1
> Latest checkpoint's NextMultiOffset:  0

I don't remember why I insisted talking about multixacts in that thread,
but seeing that both the poster in the 2007 thread and you have problems
with the pg_subtrans directory, not pg_multixact, these "symptoms"
actually mean nothing at all.  pg_subtrans and pg_multixact are
unrelated.

I wonder if there's an off-by-one bug in SimpleLruTruncate, or perhaps
the "cutoffPage" value passed by the caller is bogus once every ten blue
moons ... hmm, it comes from GetOldestXmin ...

Being more explicit in that error message (logging the cutoffPage) would
help figuring out what's going on.
--