Re: ERROR: could not open relation

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: "Thomas F(dot) O'Connell" <tfo(at)sitening(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PgSQL General <pgsql-general(at)postgresql(dot)org>
Subject: Re: ERROR: could not open relation
Date: 2005-07-14 16:14:03
Message-ID: 20050714161403.GD19232@alvh.no-ip.org
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On Thu, Jul 14, 2005 at 10:49:56AM -0500, Thomas F. O'Connell wrote:

> Does bgwriter operate on temp tables, and could there exist an edge
> condition in which bgwriter might have scheduled a write to disk for
> a file corresponding to a temp table that was removed by sudden
> termination of the session in which the temp table existed such that
> the file was removed?

I suggested that bgwriter may be the culprit, mainly because the log
lines were not preceded by the log_line_prefix as the other lines in the
log. See an extract here: http://rafb.net/paste/results/awxFnY15.html
This may represent a file going away, and a dirty buffer being kept in
memory. How did that happen, I have no clue.

Thomas also mentioned that after the error first appeared, all queries
started failing with the same error message. That does not make any
sense to me; but maybe it could have to do with a corrupt buffer in the
buffer freelist, which every backend tried to write but failed.

I guess the important question to be asking is how did the system get
into that state.

--
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"Uno puede defenderse de los ataques; contra los elogios se esta indefenso"

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