Received: from magus.postgresql.org ([87.238.57.229]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TLzjs-00066L-5K for pgsql-performance@postgresql.org; Wed, 10 Oct 2012 17:06:32 +0000 Received: from smtp02.smtpout.orange.fr ([80.12.242.124] helo=smtp.smtpout.orange.fr) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TLzjm-0006j9-HT for pgsql-performance@postgresql.org; Wed, 10 Oct 2012 17:06:31 +0000 Received: from axege.com ([82.127.232.162]) by mwinf5d25 with ME id 9V6Q1k00C3WtTCJ03V6QxZ; Wed, 10 Oct 2012 19:06:25 +0200 Received: from localhost (localhost [127.0.0.1]) by axege.com (Postfix) with ESMTP id 5BAAC43DE04 for ; Wed, 10 Oct 2012 19:06:24 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at myhostname="axege.com." Received: from axege.com ([127.0.0.1]) by localhost (axege.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CqziaLLkeDEN for ; Wed, 10 Oct 2012 19:06:23 +0200 (CEST) Received: from [10.0.0.78] (unknown [10.0.0.78]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by axege.com (Postfix) with ESMTPSA id D0FC443DE02 for ; Wed, 10 Oct 2012 19:06:23 +0200 (CEST) Message-ID: <5075AB0F.5030005@axege.com> Date: Wed, 10 Oct 2012 19:06:23 +0200 From: Franck Routier User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20121003 Thunderbird/15.0.1 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Drawbacks of create index where is not null ? Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms050701000608040104040309" X-Pg-Spam-Score: -1.9 (-) X-Archive-Number: 201210/122 X-Sequence-Number: 48081 Ceci est un message signé cryptographiquement au format MIME. --------------ms050701000608040104040309 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Hi, I have pretty large tables, with columns that might never receive any=20 data, or always receive data, based on the customer needs. The index on these columns are really big, even if the column is never=20 used, so I tend to add a "where col is not null" clause on those indexes.= What are the drawbacks of defining my index with a "where col is not=20 null" clause ? 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