Re: Question about Generating Possible Plans by the planner/optimizer - Mailing list pgsql-performance

From Steinar H. Gunderson
Subject Re: Question about Generating Possible Plans by the planner/optimizer
Date
Msg-id 20040807011148.GA6617@uio.no
Whole thread Raw
In response to Question about Generating Possible Plans by the planner/optimizer  ("sandra ruiz" <mileruiz@hotmail.com>)
List pgsql-performance
On Fri, Aug 06, 2004 at 07:28:38PM -0500, sandra ruiz wrote:
> in the docummentation about the planer it says:
>
> "It first combines all possible ways of scanning and joining the relations
> that appear in a query"
>
> I would like to know if there's a time limit to do that or if it just scans
> ALL the posibilities until it finishes..no matter the time it takes..

Depends; if you join a lot of tables, it stops doing an exhaustive search and
goes for genetic optimization instead:

  http://www.postgresql.org/docs/7.4/static/geqo.html

/* Steinar */
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Homepage: http://www.sesse.net/

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