X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 2497E9DC845 for ; Wed, 11 Jan 2006 17:13:24 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 89840-03 for ; Wed, 11 Jan 2006 17:13:25 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id A964E9DC839 for ; Wed, 11 Jan 2006 17:13:21 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id k0BLDKgq028233; Wed, 11 Jan 2006 16:13:20 -0500 (EST) To: "Jim C. Nasby" cc: Andrea Arcangeli , pgsql-performance@postgresql.org Subject: Re: NOT LIKE much faster than LIKE? In-reply-to: <20060111210221.GD63175@pervasive.com> References: <20060110014447.GB18474@opteron.random> <20060111184032.GS3902@pervasive.com> <20060111203947.GL15897@opteron.random> <20060111210221.GD63175@pervasive.com> Comments: In-reply-to "Jim C. Nasby" message dated "Wed, 11 Jan 2006 15:02:21 -0600" Date: Wed, 11 Jan 2006 16:13:20 -0500 Message-ID: <28232.1137014000@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.084 required=5 tests=[AWL=0.084] X-Spam-Score: 0.084 X-Spam-Level: X-Archive-Number: 200601/126 X-Sequence-Number: 16604 "Jim C. Nasby" writes: > On Wed, Jan 11, 2006 at 09:39:47PM +0100, Andrea Arcangeli wrote: >> The index only helps the above query with = 0 and not the one with != 0, >> but it seems not needed in practice. > I suspect this is because of a lack of stats for functional indexes. No, it's because != isn't an indexable operator. regards, tom lane