From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andreas Gaab <A.Gaab@scanlab.de>
Cc: pgsql-sql mailing list <pgsql-sql@postgresql.org>
Cc: Hans Joachim Münzer <H.Muenzer@scanlab.de>
Subject: Re: WAL-files restore and nextval('PK')
Date: Mon, 03 May 2010 09:33:21 -0400
Message-ID: <14002.1272893601@sss.pgh.pa.us> (raw)
In-Reply-To: <48DA836F3865C54B8FBF424A3B775AF6010D455863@Exchange-Server>
References: <48DA836F3865C54B8FBF424A3B775AF6010D455863@Exchange-Server>
Andreas Gaab <A.Gaab@scanlab.de> writes:
> after an WAL-restore of our Postgres DB, we observe seemingly wrong values of our sequences.
> We have two postgres server (8.4) with pgpool in replication mode.
> Recently we tested our restore procedure and played our WAL-files into the second server after an old file-system backup was restored.
> Accidently, we aborted the starting server and had to restart it and therefore started WAL-replay again.
> Now we observe, that the newly restored server has higher values in his sequences as the other server.
It's normal for sequence counters to be a few counts higher after a
crash-and-restart than they would have been if no crash had occurred.
This is an intentional design tradeoff to minimize the WAL overhead
associated with assigning a sequence value. If you find it intolerable
for what you're doing, I believe you can prevent it by adjusting the
sequence parameters to prevent any "caching" of values.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, A.Gaab@scanlab.de, H.Muenzer@scanlab.de
Subject: Re: WAL-files restore and nextval('PK')
In-Reply-To: <14002.1272893601@sss.pgh.pa.us>
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