Re: pgsql: Track the current XID wrap limit (or more accurately, the oldest

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)postgresql(dot)org>
Cc: pgsql-committers(at)postgresql(dot)org
Subject: Re: pgsql: Track the current XID wrap limit (or more accurately, the oldest
Date: 2009-08-31 06:48:34
Message-ID: 4A9B7242.3000903@enterprisedb.com
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Tom Lane wrote:
> Log Message:
> -----------
> Track the current XID wrap limit (or more accurately, the oldest unfrozen
> XID) in checkpoint records. This eliminates the need to recompute the value
> from scratch during database startup, which is one of the two remaining
> reasons for the flatfile code to exist.

1. Cluster is close to the stop limit.
2. Autovacuum runs, updates pg_database and advances oldestXid. Phew!
3. Crash.

After recovery, oldestXid is reset to the old value, and you start
getting warnings again. However, everything seems fine in pg_database,
all the databases have been recently vacuumed. Does autovacuum ever run
to fix that? ISTM it won't.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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