Re: Extremely irregular query performance

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От Bruce Momjian
Тема Re: Extremely irregular query performance
Дата
Msg-id 200601201642.k0KGgBS23410@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: Extremely irregular query performance  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-performance
Done, and paragraph added to 8.1.X.  (7.3 mention retained for 8.1.X.)

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Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.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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