Re: slow plan for min/max

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От Bruno Wolff III
Тема Re: slow plan for min/max
Дата
Msg-id 20030909193428.GA15389@wolff.to
обсуждение исходный текст
Ответ на Re: slow plan for min/max  (Thomas Swan <tswan@idigx.com>)
Список pgsql-performance
On Tue, Sep 09, 2003 at 14:06:56 -0500,
  Thomas Swan <tswan@idigx.com> wrote:
>
> Would it be possible to rewrite min and max at the parser level into a
> select/subselect  (clause) condition ( repeat condition ) order by
> (clause ) descending/ascending limit 1 and thereby avoiding the
> penalties of altering the default aggregate behavior?  Would it yield
> anything beneficial?

That isn't always going to be the best way to do the calculation. If there
are other aggregates or if the groups are small, doing things the normal
way (and hash aggregates in 7.4 will help) can be faster.

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