Re: Extremely irregular query performance

От: Bruce Momjian
Тема: Re: Extremely irregular query performance
Дата: ,
Msg-id: 200601201642.k0KGgBS23410@candle.pha.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: Extremely irregular query performance  (Tom Lane)
Список: pgsql-performance

Скрыть дерево обсуждения

Extremely irregular query performance  (Jean-Philippe Côté<>, )
 Re: Extremely irregular query performance  (Tom Lane, )
  Re: Extremely irregular query performance  (Jean-Philippe Côté<>, )
   Re: Extremely irregular query performance  (Mark Lewis, )
   Re: Extremely irregular query performance  (Tom Lane, )
    Re: Extremely irregular query performance  (Simon Riggs, )
     Re: Extremely irregular query performance  (Kenneth Marshall, )
     Re: Extremely irregular query performance  (Bruce Momjian, )
      Re: Extremely irregular query performance  (Tom Lane, )
       Re: Extremely irregular query performance  (Bruce Momjian, )
 Re: Extremely irregular query performance  (Scott Marlowe, )
 Re: Extremely irregular query performance  (Jean-Philippe Cote, )
  Re: Extremely irregular query performance  (Bruce Momjian, )
  Re: Extremely irregular query performance  (Kenneth Marshall, )

Done, and paragraph added to 8.1.X.  (7.3 mention retained for 8.1.X.)

---------------------------------------------------------------------------

Tom Lane wrote:
> Bruce Momjian <> 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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