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Message-ID: <357fa7590611011115q748ddce9qa6cf570ec2f15348@mail.gmail.com>
Date: Wed, 1 Nov 2006 14:15:29 -0500
From: "Steven Flatt" <steven.flatt@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Database-wide vacuum can take a long time,
	during which tables are not being analyzed
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Here is a potential problem with the auto-vacuum daemon, and I'm wondering
if anyone has considered this.  To avoid transaction ID wraparound, the
auto-vacuum daemon will periodically determine that it needs to do a DB-wide
vacuum, which takes a long time.  On our system, it is on the order of a
couple of weeks.  (The system is very busy and there is a lot of I/O going
on pretty much 24/7).  During this period of time, there is nothing to
automatically analyze any of the tables, leading to further performance
problems.  What are your thoughts on having the DB-wide vacuum running on a
separate thread so that the daemon can concurrently wake up and take care of
analyzing tables?

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<div>Here is a potential problem with the auto-vacuum daemon, and I'm wondering if anyone has considered this.&nbsp; To avoid transaction ID wraparound, the auto-vacuum daemon will periodically determine that it needs to do a DB-wide vacuum, which takes a long time.&nbsp; On our system, it is on the order of a couple of weeks.&nbsp; (The system is very busy and there is a lot of I/O going on pretty much 24/7).&nbsp; During this period of time, there is nothing to automatically analyze any of the tables, leading to further performance problems.&nbsp; What are your thoughts on having the DB-wide vacuum running on a separate thread so that the daemon can concurrently wake up and take care of analyzing tables?
</div>

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