Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 6B6FB2E36F2 for ; Sun, 13 Jan 2008 16:48:17 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 29363-05 for ; Sun, 13 Jan 2008 16:48:15 -0400 (AST) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 51BAB2E36A9 for ; Sun, 13 Jan 2008 16:48:14 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.1/8.14.1) with ESMTP id m0DKloC0008607; Sun, 13 Jan 2008 15:47:51 -0500 (EST) To: "Julian Scarfe" cc: pgsql-performance@postgresql.org Subject: Re: Inheritance, unique keys and performance In-reply-to: <01fb01c8561a$76d6b4a0$0600a8c0@Wilbur> References: <01a301c85552$24ab6270$0600a8c0@Wilbur> <21684.1200170118@sss.pgh.pa.us> <01b601c855c4$8ed20a60$0600a8c0@Wilbur> <7212.1200250003@sss.pgh.pa.us> <01fb01c8561a$76d6b4a0$0600a8c0@Wilbur> Comments: In-reply-to "Julian Scarfe" message dated "Sun, 13 Jan 2008 19:28:18 +0000" Date: Sun, 13 Jan 2008 15:47:50 -0500 Message-ID: <8606.1200257270@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200801/110 X-Sequence-Number: 28349 "Julian Scarfe" writes: > From: "Tom Lane" >> The >> problem you've got is that you need a nestloop-with-inner-indexscan >> plan type, where the inner side is an Append group (that is, an >> inheritance tree) --- and 8.1 doesn't know how to create such a plan. >> If you can update to 8.2 or later it should get better. > Isn't test 3 (scalar subqueries) also a nestloop-with-inner-indexscan with > an inner Append? No. The subquery is planned separately and sees the upper query's variable as a pseudo-constant Param. In neither query does the planner think that a join is happening. regards, tom lane