On Fri, Feb 20, 2009 at 3:33 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > =?UTF-8?Q?Grzegorz_Ja=C5=9Bkiewicz?= <gryzman@xxxxxxxxx> writes: >> I mean query like: >> select id from foo where id not in ( select id from bar); >> into: >> select f.id from foo f left join bar b on f.id=b.id where b.id is null; > > Postgres does not do that, because they don't mean the same thing --- > the behavior for NULLs in bar.id is different. yes, the obvious assumption here is that all columns are 'not null'; > 8.4 does understand that NOT EXISTS is an antijoin, though. Yes, I noticed that it actually assumes lesser cost. -- GJ -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
