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From: Guillaume Lelarge <guillaume@lelarge.info>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: postgresql@foo.me.uk, postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Slow query: bitmap scan troubles
Date: Sat, 08 Dec 2012 16:15:42 +0100
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On Tue, 2012-12-04 at 15:42 -0800, Jeff Janes wrote:
> On Tue, Dec 4, 2012 at 10:03 AM,  <postgresql@foo.me.uk> wrote:
> >[...]
> >
> > Is there some nice bit of literature somewhere that explains what sort of
> > costs are associated with the different types of lookup?
> 
> I've heard good things about Greg Smith's book, but I don't know if it
> covers this particular thing.
> 
> Otherwise, I don't know of a good single place which is a tutorial
> rather than a reference (or the code itself)
> 

Greg's book is awesome. It really gives a lot of
informations/tips/whatever on performances. I mostly remember all the
informations about hardware, OS, PostgreSQL configuration, and such. Not
much on the EXPLAIN part.

On the EXPLAIN part, you may have better luck with some slides available
here and there.

Robert Haas gave a talk on the query planner at pgCon 2010. The audio
feed of Robert Haas talk is available with this file:
http://www.pgcon.org/2010/audio/15%20The%20PostgreSQL%20Query%
20Planner.mp3

You can also find the slides on
https://sites.google.com/site/robertmhaas/presentations

You can also read the "Explaining the Postgres Query Optimizer" talk
written by Bruce Momjian. It's available there :
http://momjian.us/main/presentations/internals.html

And finally, you can grab my slides over here:
http://www.dalibo.org/_media/understanding_explain.pdf. You have more
than slides. I tried to put a lot of informations in there.


-- 
Guillaume
http://blog.guillaume.lelarge.info
http://www.dalibo.com



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