Re: LIMIT clause optimization

Поиск
Список
Период
Сортировка
От Felipe Schnack
Тема Re: LIMIT clause optimization
Дата
Msg-id 1041943455.6409.39.camel@desenv1.ritterdosreis.br
обсуждение исходный текст
Ответ на Re: LIMIT clause optimization  (Holger Klawitter <lists@klawitter.de>)
Ответы Re: LIMIT clause optimization  (Bruno Wolff III <bruno@wolff.to>)
Список pgsql-general
  Why? I don't understand. If I create a query and want just the first
row from it, wouldn't speed up things a lot just adding "LIMIT 1" in the
end of the query?

On Tue, 2003-01-07 at 10:44, Holger Klawitter wrote:
> Am Dienstag, 7. Januar 2003 12:47 schrieb Felipe Schnack:
> >   I was wondering... (a newbie starting to understand how to optimize
> > queries)
> >   In which step of query execution the LIMIT clause is executed? I mean
> > I have a query that would return, let's say, 6 rows, but I add a "LIMIT
> > 1" in the end of it.
> >   I would speed up things because I would have less data fetching from
> > the database, right?
>
> Limit kicks in quite late as it has to be done after sorting. And it is not
> recommended to use LIMIT without ORDER BY.
>
> With kind regards / mit freundlichem Gruß
>     Holger Klawitter
> --
> Holger Klawitter                          http://www.klawitter.de
> lists@klawitter.de
--

Felipe Schnack
Analista de Sistemas
felipes@ritterdosreis.br
Cel.: (51)91287530
Linux Counter #281893

Centro Universitário Ritter dos Reis
http://www.ritterdosreis.br
ritter@ritterdosreis.br
Fone/Fax.: (51)32303341


В списке pgsql-general по дате отправления:

Предыдущее
От: Holger Klawitter
Дата:
Сообщение: Re: LIMIT clause optimization
Следующее
От: Alan Gutierrez
Дата:
Сообщение: Re: 7.3 Prepared statements