Re: Extremely irregular query performance

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Jean-Philippe Côté <jean-philippe(dot)cote(at)crt(dot)umontreal(dot)ca>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Extremely irregular query performance
Date: 2006-01-20 16:34:49
Message-ID: 18684.1137774889@sss.pgh.pa.us
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Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> <para>
> ! Genetic query optimization (<acronym>GEQO</acronym>) randomly
> ! tests execution plans. Therefore, when the number of tables
> ! exceeds <varname>geqo</> and genetic query optimization is in use,
> ! the execution plan will change each time the statement is executed.
> </para>

geqo_threshold, please --- geqo is a boolean.

Possibly better wording: Therefore, when the number of tables exceeds
geqo_threshold causing genetic query optimization to be used, the
execution plan is likely to change each time the statement is executed.

regards, tom lane

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