Re: BUG #3883: Autovacuum deadlock with truncate?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Steven Flatt" <steven(dot)flatt(at)gmail(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #3883: Autovacuum deadlock with truncate?
Date: 2008-01-17 18:27:46
Message-ID: 11314.1200594466@sss.pgh.pa.us
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"Steven Flatt" <steven(dot)flatt(at)gmail(dot)com> writes:
> This isn't a postgres deadlock per se, but the end result is that two
> postgres backends are stuck, each waiting on a PGSemaphoreLock that the
> other presumably has. The processes have been stuck for hours.

No, that's not what the backtraces say. The autovac process is trying
to get super-exclusive lock on a buffer (apparently in relation 16783
--- what is that?). There's no evidence in the stack trace that the
TRUNCATE process has any conflicting buffer lock.

What I think might be happening is a three-way deadlock involving these
two and a third process that has the desired buffer lock. Have you got
anything else that seems to be stuck?

regards, tom lane

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