From oracle-l-bounce@freelists.org Mon Oct 10 06:11:05 2005 Return-Path: Received: from air891.startdedicated.com (root@localhost) by orafaq.com (8.12.10/8.12.10) with ESMTP id j9ABB5cw009183 for ; Mon, 10 Oct 2005 06:11:05 -0500 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air891.startdedicated.com (8.12.10/8.12.10) with ESMTP id j9ABB2vX009171 for ; Mon, 10 Oct 2005 06:11:02 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 9AB851FA0BA; Mon, 10 Oct 2005 06:10:59 -0500 (EST) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 00602-05; Mon, 10 Oct 2005 06:10:59 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 1C5FD1FA0C6; Mon, 10 Oct 2005 06:10:59 -0500 (EST) X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by Ecartis Subject: RE: Bitmap Index Date: Mon, 10 Oct 2005 13:09:02 +0200 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Bitmap Index Thread-Index: AcXNg88q26KsIc41R1+DrSIbpG0+GwABiDpQ From: "Christian Antognini" To: Cc: X-OriginalArrivalTime: 10 Oct 2005 11:09:02.0255 (UTC) FILETIME=[054603F0:01C5CD8B] X-archive-position: 26621 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: Christian.Antognini@trivadis.com Precedence: normal Reply-To: Christian.Antognini@trivadis.com X-list: oracle-l X-Virus-Scanned: by amavisd-new-20030616-p9 (Debian) at avenirtech.net X-mailscan-MailScanner-Information: Please contact the ISP for more information X-mailscan-MailScanner: Found to be clean X-MailScanner-From: oracle-l-bounce@freelists.org X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on air891.startdedicated.com X-Spam-Level: X-Spam-Status: No, hits=-3.1 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=2.63 Deepak >In my DWH DB I have a table with few million rows. >I have a column in the table having 15 distinct >values. That column is being used in the where >clause of the queries. What I am interested to know >is would it be beneficial to create a bitmap index >on it. As usually it depends... What does "used" mean? (e.g. equality or inequality) Do you have other restrictions in your WHERE clause? Which is the distribution of the 15 values? As already suggested by Shiva list partitioning (or even other types as well...) could be a better solution than indexing. >Is there any specific ratio (distincy values)/(Num of rows) >at which one must consider creating bitmap indexes rather >than b-tree indexes? The choice between bitmap and b-tree indexes is not influenced by something like "(distincy values)/(Num of rows)". It only depends on the application's requirements! HTH Chris New Features Oracle Database 10g Release 2 seminars @ www.trivadis.com Italiano: Lugano (24-Nov) Français: Genève (17-Nov) Deutsch: Hamburg (13-Oct), München (20-Oct), Basel (25-Oct), Frankfurt (27-Oct), Bern (8-Nov), Düsseldorf (23-Nov), Zürich (29-Nov), Stuttgart (13-Dec) -- http://www.freelists.org/webpage/oracle-l