Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id BB3641337990 for ; Thu, 27 Jan 2011 16:44:19 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 84737-01 for ; Thu, 27 Jan 2011 20:44:11 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from hrndva-omtalb.mail.rr.com (hrndva-omtalb.mail.rr.com [71.74.56.122]) by mail.postgresql.org (Postfix) with ESMTP id 051471337B6E for ; Thu, 27 Jan 2011 16:44:10 -0400 (AST) X-Authority-Analysis: v=1.1 cv=+c36koQ5Dcj/1qolKHjtkYAGXvrVJRRiKMp+84F5sLg= c=1 sm=0 a=cYhYf6uZ5ZgA:10 a=8nJEP1OIZ-IA:10 a=RAii6je2cdnAH6ATCOpc6g==:17 a=_Ixf_7qHAAAA:8 a=sn1KrSsk8Ns8hRFSiS8A:9 a=5vvSz4yj2U3xZSCXVLoA:7 a=04WuwVvielBOV4VsXaTzT9LjbWgA:4 a=wPNLvfGTeEIA:10 a=ryAo9hy1-OkA:10 a=6vsjEBoLwlAA:10 a=0tfO7MgyNwYA:10 a=HItZWiErncgA:10 a=RAii6je2cdnAH6ATCOpc6g==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.73.87.196 Received: from [74.73.87.196] ([74.73.87.196:52136] helo=[192.168.1.103]) by hrndva-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 7A/F8-24070-A19D14D4; Thu, 27 Jan 2011 20:44:10 +0000 Message-ID: <4D41D91A.3010308@vmsinfo.com> Date: Thu, 27 Jan 2011 15:44:10 -0500 From: Mladen Gogala User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.13) Gecko/20101207 Lightning/1.0b2 Thunderbird/3.1.7 MIME-Version: 1.0 To: Scott Marlowe CC: Igor Neyman , Tom Lane , David Wilson , Kenneth Marshall , "pgsql-performance@postgresql.org" Subject: Re: Postgres 9.0 has a bias against indexes References: <4D419214.8060003@vmsinfo.com> <20110127154539.GE6475@aart.is.rice.edu> <4D41959B.8020901@vmsinfo.com> <17268.1296146447@sss.pgh.pa.us> <4D41A496.70205@vmsinfo.com> <4D41D62C.40501@vmsinfo.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.9 tagged_above=-10 required=5 tests=BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001 X-Spam-Level: X-Archive-Number: 201101/291 X-Sequence-Number: 42078 On 1/27/2011 3:37 PM, Scott Marlowe wrote: > On Thu, Jan 27, 2011 at 1:31 PM, Mladen Gogala > wrote: >> There is INDEX UNIQUE SCAN PK_EMP. Oracle will use an index. > That's because Oracle has covering indexes. > I am not sure what you mean by "covering indexes" but I hope that for the larger table I have in mind, indexes will be used. For a small table like this, not using an index may actually be a better plan. I cannot compare because my development PostgreSQL cluster is on a much weaker machine than the development Oracle database. I even looked into Wikipedia for the notion of "covering index" and it is defined as an index which contains all the data requested in a query. This is not the case, EMP is not an index-organized table. The only index used was the primary key, also available in the PostgreSQL version of the table. -- Mladen Gogala Sr. Oracle DBA 1500 Broadway New York, NY 10036 (212) 329-5251 www.vmsinfo.com