From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Kellerer <spam_eater@gmx.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: DELETE using an outer join
Date: Thu, 19 Jul 2012 10:52:34 -0400
Message-ID: <21289.1342709554@sss.pgh.pa.us> (raw)
In-Reply-To: <ju8veb$dkn$1@dough.gmane.org>
References: <ju8veb$dkn$1@dough.gmane.org>
Thomas Kellerer <spam_eater@gmx.net> writes:
> Lately I had some queries of the form:
> select t.*
> from some_table t
> where t.id not in (select some_id from some_other_table);
> I could improve the performance of them drastically by changing the NOT NULL into an outer join:
> select t.*
> from some_table t
> left join some_other_table ot on ot.id = t.id
> where ot.id is null;
If you're using a reasonably recent version of PG, replacing the NOT IN
by a NOT EXISTS test should also help.
> Now I was wondering if a DELETE statement could be rewritten with the same "strategy":
Not at the moment. There have been discussions of allowing the same
table name to be respecified in USING, but there are complications.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, spam_eater@gmx.net
Subject: Re: DELETE using an outer join
In-Reply-To: <21289.1342709554@sss.pgh.pa.us>
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