Re: Slow left outer join - Mailing list pgsql-general

From Tom Lane
Subject Re: Slow left outer join
Date
Msg-id 963.1164591948@sss.pgh.pa.us
Whole thread Raw
In response to Slow left outer join  (Alexander Staubo <alex@purefiction.net>)
Responses Re: Slow left outer join  (Alexander Staubo <alex@purefiction.net>)
List pgsql-general
Alexander Staubo <alex@purefiction.net> writes:
> select comments.*, users.*
> from comments
> left outer join users on
>    users.id = comments.creator_id
> inner join events_comments on
>    comments.id = events_comments.comment_id
>    and events_comments.event_id = 9244

> The outer join seems unnecessarily slow.

Try flipping the order of the two joins.  PG 8.2 will be smart enough to
do that for itself, but no existing release understands when it's safe
to rearrange outer-join order.

            regards, tom lane

pgsql-general by date:

Previous
From: Richard Broersma Jr
Date:
Subject: Re: Slow left outer join
Next
From: Jim Nasby
Date:
Subject: Re: Question about PG cache selection strategy