Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1ZTfTp-0000Px-5K for pgsql-hackers@arkaria.postgresql.org; Mon, 24 Aug 2015 00:19:17 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84) (envelope-from ) id 1ZTfTo-00008U-Gh for pgsql-hackers@arkaria.postgresql.org; Mon, 24 Aug 2015 00:19:16 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.84) (envelope-from ) id 1ZTfTm-0008UW-8m for pgsql-hackers@postgresql.org; Mon, 24 Aug 2015 00:19:14 +0000 Received: from sss.pgh.pa.us ([66.207.139.130]) by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.84) (envelope-from ) id 1ZTfTi-0005Kj-6M for pgsql-hackers@postgresql.org; Mon, 24 Aug 2015 00:19:12 +0000 Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.4/8.14.4) with ESMTP id t7O0J3Kc005086; Sun, 23 Aug 2015 20:19:03 -0400 From: Tom Lane To: David Rowley cc: Tomas Vondra , PostgreSQL-development Subject: Re: Performance improvement for joins where outer side is unique In-reply-to: References: <20150320.121140.148610378.horiguchi.kyotaro@lab.ntt.co.jp> <27152324.eFKJb4Khb5@dinodell> <8608754a32d1325c2f83ba8b1df71585@xs4all.nl> <55DA1F9F.5040204@2ndquadrant.com> Comments: In-reply-to David Rowley message dated "Mon, 24 Aug 2015 11:35:54 +1200" Date: Sun, 23 Aug 2015 20:19:03 -0400 Message-ID: <5085.1440375543@sss.pgh.pa.us> X-Pg-Spam-Score: -3.1 (---) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-hackers Precedence: bulk Sender: pgsql-hackers-owner@postgresql.org David Rowley writes: > On 24 August 2015 at 07:31, Tomas Vondra > wrote: >> 2) in the explain output, there should probably be a space before the >> '(inner unique)' text, so >> >> Hash Join (inner unique) ... >> >> instead of >> >> Hash Join(inner unique) >> >> but that's just nitpicking at this point. Otherwise the patch seems quite >> solid to me. > The attached fixes these two issues. Please, no. Randomly sticking additional bits of information into Join Type is a good way to render EXPLAIN output permanently unintelligible, not only to humans but to whatever programs are still trying to read the text output format (I think explain.depesz.com still does). It is also not a great idea to put more semantic distance between the text and non-text output representations. I am not exactly convinced that this behavior needs to be visible in EXPLAIN output at all, but if it does, it should be a separate field. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers