Re: OUTER JOIN performance regression remains in 8.3beta4 - Mailing list pgsql-hackers

From Alvaro Herrera
Subject Re: OUTER JOIN performance regression remains in 8.3beta4
Date
Msg-id 20080108212051.GA20485@alvh.no-ip.org
Whole thread Raw
In response to Re: OUTER JOIN performance regression remains in 8.3beta4  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: OUTER JOIN performance regression remains in 8.3beta4
Re: OUTER JOIN performance regression remains in 8.3beta4
List pgsql-hackers
Tom Lane wrote:

> Comparing the behavior of this to my patch for HEAD, I am coming to the
> conclusion that this is actually a *better* planning method than
> removing the redundant join conditions, even when they're truly
> rendundant!  The reason emerges as soon as you look at cases involving
> more than a single join.  If we strip the join condition from just one
> of the joins, then we find that the planner insists on doing that join
> last, whether it's a good idea or not, because clauseful joins are
> always preferred to clauseless joins in the join search logic.

Would it be a good idea to keep removing redundant clauses and rethink
the preference for clauseful joins, going forward?

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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