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Re: postgres 9 query performance

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org, yazan suleiman <yazan(dot)suleiman(at)gmail(dot)com>
Subject: Re: postgres 9 query performance
Date: 2011-01-30 22:35:03
Message-ID: 201101302335.03863.andres@anarazel.de (view raw or flat)
Thread:
Lists: pgsql-performance
On Sunday 30 January 2011 23:18:15 Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > What happens if you change the
> > 
> >     left join event.origin on event.id = origin.eventid
> > 
> > into
> > 
> >     join event.origin on event.id = origin.eventid
> > 
> > ?
> > 
> > The EXISTS() requires that origin is not null anyway. (Not sure why the
> > planner doesn't recognize that though).
> 
> Sloppy thinking in reduce_outer_joins() is why. 
Wow. Nice one, thanks.

Andres

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