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Re: Max permutations

From: <ryan.gaffuri_at_cox.net>
Date: Mon, 9 Feb 2004 11:59:20 -0500
Message-Id: <20040209165920.CMHJ19895.lakemtao04.cox.net@smtp.east.cox.net>


isnt there a paper floating around that talks about using 79,999 for some reason? or do i have it mixed up with the cost parameters?

i thought mogens norgaard wrote it?
>
> From: "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk>
> Date: 2004/02/09 Mon AM 10:51:55 EST
> To: <oracle-l_at_freelists.org>
> Subject: Max permutations
>
>
> Has anyone done any recent testing on the
> effect of optimizer_max_permutations.
>
> I recall seeing a note on metalink once said
> the CBO would change the way in which it
> permuted join orders if the parameter was
> set to any value other than 80,000. I'm also
> fairly sure that I ran up a test a few years
> ago that demonstrated this effect.
>
> However, I've just run up a simple test on
> 8.1.7.4 and 9.2.0.4 where the only change
> was the number of join orders examined
> before the optimizer stopped (a few hundred
> for omp = 2000, a couple of thousand for
> omp-80000) - the permutation sequences were
> was identical.
>
>
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> The educated person is not the person
> who can answer the questions, but the
> person who can question the answers -- T. Schick Jr
>
>
> Next public appearances:
> March 2004 Hotsos Symposium - The Burden of Proof
> March 2004 Charlotte NC OUG - CBO Tutorial
> April 2004 Iceland
>
>
> One-day tutorials:
> http://www.jlcomp.demon.co.uk/tutorial.html
>
>
> Three-day seminar:
> see http://www.jlcomp.demon.co.uk/seminar.html
> ____UK___February
> ____UK___June
>
>
> The Co-operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
>
>
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Received on Mon Feb 09 2004 - 10:59:20 CST

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