Subject: Re: GEQO Benchmark
From: Simon Riggs <simon@2ndquadrant.com>
To: Tarcizio Bini <tarcizioab@c3sl.ufpr.br>
Cc: pgsql-performance@postgresql.org
In-Reply-To: <461a87490805280913ha5bbc90w63db53787ced2adf@mail.gmail.com>
References: <55311.200.17.202.126.1211982648.squirrel@webmail.inf.ufpr.br>
	<27530.1211983350@sss.pgh.pa.us>
	<461a87490805280913ha5bbc90w63db53787ced2adf@mail.gmail.com>
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Date: Wed, 28 May 2008 17:52:40 +0100
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On Wed, 2008-05-28 at 13:13 -0300, Tarcizio Bini wrote:

> Of course, the geqo_threshold can be changed so that the geqo be
> performed in queries that have less than 12 tables. However, we aim to
> test the GEQO algorithm in conditions where the standard algorithm
> (dynamic programming) has a high cost to calculate the query plan.

My understanding is the GEQO cannot arrive at a better plan than the
standard optimizer, so unless you wish to measure planning time there
isn't much to test. What is the quality of the plans it generates? Well
that varies according to the input; sometimes it gets the right plan,
other times it doesn't get close.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support