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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: daveg <daveg(at)sonic(dot)net>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: error: could not find pg_class tuple for index 2662
Date: 2011-07-29 15:27:02
Message-ID: 26224.1311953222@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Jul 29, 2011 at 9:55 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> 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 was thinking more along the lines of a failure while processing a
> sinval message emitted by the REINDEX.  The sinval message doesn't get
> fully processed and therefore we get confused about what the
> relfilenode is for pg_class.  If that happened for any other relation,
> we could recover by scanning pg_class.  But if it happens for pg_class
> or pg_class_oid_index, we're toast, because we can't scan them without
> knowing what relfilenode to open.

Well, no, because the ScanPgRelation call is not failing internally.
It's performing a seqscan of pg_class and not finding a matching tuple.

You could hypothesize about maybe an sinval message got missed leading
us to scan the old (pre-VAC-FULL) copy of pg_class, but that still
wouldn't explain how come we can't find a valid-looking entry for
pg_class_oid_index in it.

Tis a puzzlement.

			regards, tom lane

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