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Re: error: could not find pg_class tuple for index 2662

From: daveg <daveg(at)sonic(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: error: could not find pg_class tuple for index 2662
Date: 2011-07-29 22:35:04
Message-ID: 20110729223504.GE15578@sonic.net (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, Jul 29, 2011 at 09:55:46AM -0400, Tom Lane wrote:
> The thing that was bizarre about the one instance in the buildfarm was
> that the error was persistent, ie, once a session had failed all its
> subsequent attempts to access pg_class failed too.  I gather from Dave's
> description that it's working that way for him too.  I can think of ways
> that there might be a transient race condition against a REINDEX, but
> it's very unclear why the failure would persist across multiple
> attempts.  The best idea I can come up with is that the session has
> somehow cached a wrong commit status for the reindexing transaction,
> causing it to believe that both old and new copies of the index's
> pg_class row are dead ... but how could that happen?  The underlying

It is definitely persistant. Once triggered the error occurs for any new
statement until the session exits.

> state in the catalog is not wrong, because no concurrent sessions are
> upset (at least not in the buildfarm case ... Dave, do you see more than
> one session doing this at a time?).

It looks like it happens to multiple sessions so far as one can tell from
the timestamps of the errors:

 timestamp    sessionid     error
 ------------ ------------- ----------------------------------------------
 03:05:37.434 4e26a861.4a6d could not find pg_class tuple for index 2662
 03:05:37.434 4e26a861.4a6f could not find pg_class tuple for index 2662

 03:06:12.041 4e26a731.438e could not find pg_class tuple for index 2662

 03:06:12.042 4e21b6a3.629b could not find pg_class tuple for index 2662
 03:06:12.042 4e26a723.42ec could not find pg_class tuple for index 2662 at character 13


-dg

-- 
David Gould       daveg(at)sonic(dot)net      510 536 1443    510 282 0869
If simplicity worked, the world would be overrun with insects.

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