Date: Thu, 25 Jan 2007 10:22:47 -0600
From: "Jim C. Nasby" <jim@nasby.net>
To: Galy Lee <lee.galy@oss.ntt.co.jp>
Cc: pgsql-hackers@postgresql.org
Subject: Re: [PERFORM] how to plan for vacuum?
Message-ID: <20070125162246.GF64372@nasby.net>
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On Thu, Jan 25, 2007 at 07:52:50PM +0900, Galy Lee wrote:
> It is very hard for any normal user to set this correctly. I think the 
> experience / trial-and-error approach is awful for the user, every DBA 
> need to be an expert of vacuum to keep the system stable. For vacuum is 
> still a big threat to the performance, a more intelligent way is needed.

Agreed.

> So I have proposed the "vacuum in time" feature in previous; just let 
> vacuum know how long can it runs, and then it will minimize the impact 
> in the time span for you. Some argue that it should not have the 
> maintenance window assumption, but the most safely way is to run in the 
> maintenance window.

Most systems I work on don't have a maintenance window. For those that
do, the window is at best once a day, and that's nowhere near often
enough to be vacuuming any database I've run across. I'm not saying they
don't exist, but effort put into restricting vacuums to a maintenance
window would serve very few people. It'd be much better to put effort
into things like piggyback vacuum.
-- 
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)