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Re: index or not

From: Andreas Kretschmer <akretschmer(at)spamfence(dot)net>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: index or not
Date: 2011-12-12 19:26:06
Message-ID: 20111212192606.GA20578@tux (view raw or flat)
Thread:
Lists: pgsql-novice
Jean-Yves F. Barbier <12ukwn(at)gmail(dot)com> wrote:

> On Mon, 12 Dec 2011 19:15:32 +0100
> Andreas Kretschmer <akretschmer(at)spamfence(dot)net> wrote:
> 
> > > I wonder if indexes are relevant or not on a small table?
> > > (250 rows, 10 columns, often retrieved in different order)
> > 
> > Don't ask us, ask EXPLAIN instead! ;-)
> 
> The PB is, it is in dev state and not filled; from what I read
> on the site about indexes, I would say "no" -  so I ask here to
> see if somebody has a return of experience.

As i said: use EXPLAIN. The answer of your question depends on a lot of
details, i can't say if an seq-scan is cheaper or not. (for instance, if
you have SSDs, a index-scan maybe is cheaper than an seq-scan ...)

Create an Index, use explain, if it use a seq-scan you can drop the index.

For such small tables it is hard to guess the plan...


Andreas
-- 
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect.                              (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly."   (unknown)
Kaufbach, Saxony, Germany, Europe.              N 51.05082°, E 13.56889°

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