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Re: slow query

From: Robert Treat <xzilla(at)users(dot)sourceforge(dot)net>
To: Clarence Gardner <clarence(at)silcom(dot)com>
Cc: Oleg Lebedev <oleg(dot)lebedev(at)waterford(dot)org>,Josh Berkus <josh(at)agliodbs(dot)com>,"pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: slow query
Date: 2003-02-24 18:30:34
Message-ID: 1046111434.1014.165.camel@camel (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, 2003-02-24 at 12:27, Clarence Gardner wrote:
> On 24 Feb 2003, Robert Treat wrote:
> 
> > 
> > If your seeing wildly dramatic improvments from vacuum full, you might
> > want to look into running regular vacuums more often (especially for
> > high turnover tables), increase your max_fsm_relations to 1000, and
> > increasing your max_fsm_pages. 
> 
> I don't know about the settings you mention, but a frequent vacuum
> does not at all obviate a vacuum full. My database is vacuumed every
> night, but a while ago I found that a vacuum full changed a simple
> single-table query from well over 30 seconds to one or two. We now
> do a vacuum full every night.
> 

Actually if you are vacuuming frequently enough, it can (and should*)
obviate a vacuum full. Be aware that frequently enough might mean really
frequent, for instance I have several tables in my database that update
every row within a 15 minute timeframe, so I run a "lazy" vacuum on
these tables every 10 minutes. This allows postgresql to reuse the space
for these tables almost continuously so I never have to vacuum full
them. 

(* this assumes your max_fsm_pages/relations settings are set correctly)

Robert Treat



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