Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1gPS9d-0001kk-8S for pgsql-hackers@arkaria.postgresql.org; Wed, 21 Nov 2018 13:02:53 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.89) (envelope-from ) id 1gPS9b-0000As-Pa for pgsql-hackers@arkaria.postgresql.org; Wed, 21 Nov 2018 13:02:51 +0000 Received: from makus.postgresql.org ([2001:4800:3e1:1::229]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1gPS9b-0000Ak-EL for pgsql-hackers@lists.postgresql.org; Wed, 21 Nov 2018 13:02:51 +0000 Received: from mail.postgrespro.ru ([93.174.131.138]) by makus.postgresql.org with esmtp (Exim 4.89) (envelope-from ) id 1gPS9Y-00028s-JQ for pgsql-hackers@postgresql.org; Wed, 21 Nov 2018 13:02:50 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.postgrespro.ru (Postfix) with ESMTP id C660E21CA29B; Wed, 21 Nov 2018 16:02:47 +0300 (MSK) X-Virus-Scanned: Debian amavisd-new at postgrespro.ru X-Spam-Flag: NO X-Spam-Score: 0 X-Spam-Level: X-Spam-Status: No, score=x tagged_above=-99 required=4 WHITELISTED tests=[] autolearn=unavailable Received: from [192.168.27.182] (gw.postgrespro.ru [93.174.131.141]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) by mail.postgrespro.ru (Postfix) with ESMTPSA id 93BD921C70A4; Wed, 21 Nov 2018 16:02:47 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=postgrespro.ru; s=mail; t=1542805367; bh=EldluoyixhR4ZWJp4IZIfVNaaPbjjxk7D4MfuJZjuMQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To; b=iEEZLl/3X9E3/x3wWtGf7ZjdZp6qJnI352hSEKbuEtu9D+YKP3x4vrBObSiLU/rjl cz/Lk4qnAhllHwG36yQuxXr7Wg6JacKzXrENwz1Rwa9kHahyNL2uQIB474slwys+68 SJTTu45n7fi5m1WT6eMcuZ5T2YN+1BiPD3popjOk= Subject: Re: [HACKERS] PoC: full merge join on comparison clause To: Tom Lane Cc: Ashutosh Bapat , pgsql-hackers , Jeff Davis References: <715cb811-4538-9967-a2e3-ca85f2711d80@postgrespro.ru> <636d3f40-be16-78cc-717f-b85e9f1b9362@postgrespro.ru> <20180123163126.GK2416@tamriel.snowman.net> <53625d9e-b608-bd9d-86a2-f560c02aff7f@postgrespro.ru> <513df2b9-b068-6cf4-895e-adb3968547e0@postgrespro.ru> <8c762bb0-1507-5ac1-b408-b942416416bf@postgrespro.ru> <36d18491-579e-e54b-96bb-4cba38c5a544@postgrespro.ru> <1a4bac9a-640d-31b8-fb6f-cc4bf36abbf9@postgrespro.ru> <9de15ac8-10b2-8569-4683-002db913! 1771@postgrespro.ru> <22877.1542592000@sss.pgh.pa.us> From: Alexander Kuzmenkov Message-ID: <5351b58a-99ca-65fe-4bcd-7739bfedae33@postgrespro.ru> Date: Wed, 21 Nov 2018 16:02:47 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <22877.1542592000@sss.pgh.pa.us> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk On 11/19/18 04:46, Tom Lane wrote: > In short, proceeding like the above when we can't find another plan > type for a full join seems like it fixes a far wider variety of cases. > The possibility that maybe we could do some of those cases a bit faster > isn't sufficiently attractive to me to justify also putting in a > mechanism like this patch proposes. We only rarely see complaints at > all about can't-do-a-full-join problems, and I do not think this patch > would fix enough of those complaints to be worthwhile. I agree, the automated UNION substitutions seems to be a better approach. I'll mark this patch as rejected then. -- Alexander Kuzmenkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company