From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200512171456.jBHEunM07437@candle.pha.pa.us>
Subject: Re: Simple Join
In-Reply-To: <7484.1134600423@sss.pgh.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 17 Dec 2005 09:56:49 -0500 (EST)
CC: Kevin Brown <blargity@gmail.com>, pgsql-performance@postgresql.org
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Tom Lane wrote:
> Kevin Brown <blargity@gmail.com> writes:
> > I'm running 8.1 installed from source on a Debian Sarge server.  I have a 
> > simple query that I believe I've placed the indexes correctly for, and I 
> > still end up with a seq scan.  It makes sense, kinda, but it should be able 
> > to use the index to gather the right values.
> 
> I continue to marvel at how many people think that if it's not using an
> index it must ipso facto be a bad plan ...
> 
> That plan looks perfectly fine to me.  You could try forcing some other
> choices by fooling with the planner enable switches (eg set
> enable_seqscan = off) but I doubt you'll find much improvement.  There
> are too many rows being pulled from ordered_products to make an index
> nestloop a good idea.

We do have an FAQ item:

     4.6) Why are my queries slow?  Why don't they use my indexes?

-- 
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