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Re: Wrong Stats and Poor Performance

From: Greg Stark <gsstark(at)mit(dot)edu>
To: Pallav Kalva <pkalva(at)deg(dot)cc>
Cc: John A Meinel <john(at)arbash-meinel(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: Wrong Stats and Poor Performance
Date: 2004-12-27 20:51:29
Message-ID: 87mzvzbh2m.fsf@stark.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-performance
Pallav Kalva <pkalva(at)deg(dot)cc> writes:

> >> I had a setup a cronjob couple of weeks ago to run vacuum analyze every 3
> >> hours on this table and still my stats are totally wrong. This is affecting
> >> the performance of the queries running on this table very badly.
> >> How can i fix this problem ?  or is this the standard postgres behaviour ?

If you need it there's nothing wrong with running vacuum even more often than
this. As often as every 5 minutes isn't unheard of.

You should also look at raising the fsm settings. You need to run vacuum often
enough that on average not more tuples are updated in the intervening time
than can be kept track of in the fsm settings. So raising the fsm settings
allow you to run vacuum less often without having things bloat.

There's a way to use the output vacuum verbose gives you to find out what fsm
settings you need. But I don't remember which number you should be looking at
there offhand.

-- 
greg


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