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Re: performance of insert/delete/update

From: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
To: Andrew Sullivan <andrew(at)libertyrms(dot)info>
Cc: PgSQL Performance ML <pgsql-performance(at)postgresql(dot)org>
Subject: Re: performance of insert/delete/update
Date: 2002-11-26 18:46:27
Message-ID: Pine.LNX.4.33.0211261142290.10813-100000@css120.ihs.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
On Tue, 26 Nov 2002, Andrew Sullivan wrote:

> On Tue, Nov 26, 2002 at 11:06:47AM -0700, scott.marlowe wrote:
> > So, the difference in performance was around 4% slower.
> > 
> > I'd hardly consider that a big hit against the database.
> > 
> > Note that in every test I've made up and run, the difference is at most 5% 
> > with vacuumdb -z running continuously in the background.  Big text fields, 
> > lots of math, lots of fks, etc...
> 
> Also, it's important to remember that you may see a considerable
> improvement in efficiency of some queries if you vacuum often, (it's
> partly dependent on the turnover in your database -- if it never
> changes, you don't need to vacuum often).  So a 5% hit in regular
> performance may be worth it over the long haul, if certain queries
> are way cheaper to run.  (That is, while you may get 4% slower
> performance overall, if the really slow queries are much faster, the
> fast queries running slower may well be worth it.  In my case,
> certainly, I think it is.)

Agreed.  We used to run vacuumdb at night only when we were running 7.1, 
and we had a script top detect if it had hung or anything.  I.e. vacuuming 
was still a semi-dangerous activity.  I now have it set to run every hour 
(-z -a switches to vacuumdb).  I'd run it more often but we just don't 
have enough load to warrant it.


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