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Re: hash semi join caused by "IN (select ...)"

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Clemens Eisserer <linuxhippy(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: hash semi join caused by "IN (select ...)"
Date: 2011-05-16 23:22:48
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Clemens Eisserer <linuxhippy(at)gmail(dot)com> writes:
> I have a quite complex, performance sensitive query in a system with a
> few (7) joins:
> select .... from t1 left join t2 .... WHERE id IN (select ....)

Does it work as expected with one less join?  If so, try increasing
join_collapse_limit ...

			regards, tom lane

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