X-Original-To: pgsql-hackers-postgresql.org@postgresql.org Received: from localhost (mx1.hub.org [200.46.208.251]) by postgresql.org (Postfix) with ESMTP id 6D89F9FA68D for ; Tue, 25 Jul 2006 19:17:03 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.208.251]) (amavisd-new, port 10024) with ESMTP id 02365-02 for ; Tue, 25 Jul 2006 19:16:53 -0300 (ADT) 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 B926A9FB1B7 for ; Tue, 25 Jul 2006 19:16:53 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id k6PMGpgR024887; Tue, 25 Jul 2006 18:16:51 -0400 (EDT) To: Ron Mayer cc: pgsql-hackers@postgreSQL.org Subject: Re: On-disk bitmap index patch In-reply-to: <44C692D9.3050406@cheapcomplexdevices.com> References: <200607250104.k6P14St25388@momjian.us> <20060725015805.GA30087@mark.mielke.cc> <5085.1153802202@sss.pgh.pa.us> <44C692D9.3050406@cheapcomplexdevices.com> Comments: In-reply-to Ron Mayer message dated "Tue, 25 Jul 2006 14:53:29 -0700" Date: Tue, 25 Jul 2006 18:16:51 -0400 Message-ID: <24886.1153865811@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0.043 tagged_above=0 required=5 tests=AWL, SPF_HELO_PASS, SPF_PASS X-Spam-Level: X-Archive-Number: 200607/1232 X-Sequence-Number: 87087 Ron Mayer writes: > Tom Lane wrote: >> If you have to hit one tuple out of four, it's pretty much guaranteed >> that you will need to fetch every heap page. > I think it's not uncommon to have data that is more clustered than expected. Sure, if the data is fairly static ... and now that there's a fillfactor option for heaps, you can even tolerate (some low rate of) updates without losing the clusteredness. However, that benefit accrues to all index types not only bitmap. regards, tom lane