thread-index: Acb+bJobK+Y+lZ+7S6O38WYUcYUJ0w==
Subject: Re: Database-wide vacuum can take a long time,
	duringwhich tables are not being analyzed
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From: "Simon Riggs" <simon@2ndquadrant.com>
To: "Steven Flatt" <steven.flatt@gmail.com>
Cc: <pgsql-performance@postgresql.org>
In-Reply-To: <357fa7590611011115q748ddce9qa6cf570ec2f15348@mail.gmail.com>
References: <357fa7590611011115q748ddce9qa6cf570ec2f15348@mail.gmail.com>
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Date: Thu, 02 Nov 2006 10:49:18 +0000
Message-ID: <1162464559.3587.291.camel@silverbirch.site>
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On Wed, 2006-11-01 at 14:15 -0500, Steven Flatt wrote:
> 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?

Yes, do it.

Every couple of weeks implies a transaction rate of ~~500tps, so I'd be
interested to hear more about your system. 

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com