Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eMhOi-0001F5-BO for pgsql-bugs@arkaria.postgresql.org; Wed, 06 Dec 2017 21:38:32 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eMhOh-0003Ip-0n for pgsql-bugs@arkaria.postgresql.org; Wed, 06 Dec 2017 21:38:31 +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_2) (envelope-from ) id 1eMhOg-0003Ib-RI for pgsql-bugs@lists.postgresql.org; Wed, 06 Dec 2017 21:38:30 +0000 Received: from mail-cys01nam02on0056.outbound.protection.outlook.com ([104.47.37.56] helo=NAM02-CY1-obe.outbound.protection.outlook.com) by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.89) (envelope-from ) id 1eMhOc-00009i-T3 for pgsql-bugs@postgresql.org; Wed, 06 Dec 2017 21:38:30 +0000 Received: from MWHPR10CA0022.namprd10.prod.outlook.com (2603:10b6:301::32) by DM3PR10MB0874.namprd10.prod.outlook.com (2a01:111:e400:c461::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.20.282.5; Wed, 6 Dec 2017 21:38:21 +0000 Received: from BL2NAM02FT021.eop-nam02.prod.protection.outlook.com (2a01:111:f400:7e46::204) by MWHPR10CA0022.outlook.office365.com (2603:10b6:301::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.282.5 via Frontend Transport; Wed, 6 Dec 2017 21:38:20 +0000 Authentication-Results: spf=permerror (sender IP is 192.231.134.1) smtp.mailfrom=blackducksoftware.com; 2ndquadrant.com; dkim=none (message not signed) header.d=none;2ndquadrant.com; dmarc=fail action=none header.from=blackducksoftware.com; Received-SPF: PermError (protection.outlook.com: domain of blackducksoftware.com used an invalid SPF mechanism) Received: from ops-mail01.dc2.lan (192.231.134.1) by BL2NAM02FT021.mail.protection.outlook.com (10.152.77.158) with Microsoft SMTP Server id 15.20.282.5 via Frontend Transport; Wed, 6 Dec 2017 21:38:18 +0000 Received: from bds01237.bds-ad.lc (bds01237.bds-ad.lc [10.1.6.127]) by ops-mail01.dc2.lan (Postfix) with ESMTPS id 3B95A43155; Wed, 6 Dec 2017 16:38:18 -0500 (EST) Subject: Re: BUG #14932: SELECT DISTINCT val FROM table gets stuck in an infinite loop To: Andres Freund , Tomas Vondra CC: Tom Lane , Thomas Munro , PostgreSQL Bugs References: <17357.1511841783@sss.pgh.pa.us> <9cd29b81-7ba1-91a2-f491-9014f4ac87e6@blackducksoftware.com> <2a76784c-06cb-46ec-35be-9895d144b839@2ndquadrant.com> <263b03b1-3e1c-49ca-165a-8ac6751419c4@2ndquadrant.com> <20171206193545.3imvbfwjgrmuho3s@alap3.anarazel.de> <790BC80E-D8E5-499B-A1E3-8EE0752B53ED@anarazel.de> <06523583-b9c5-1424-ef0a-1fc8063e9ed7@2ndquadrant.com> <20171206204616.wcect35fuj5gjde2@alap3.anarazel.de> <67e5af9b-f509-7b9e-f7a1-e01112f6c18d@2ndquadrant.com> <20171206211225.zcp2crfr3bssn3xr@alap3.anarazel.de> From: "Todd A. Cook" Message-ID: <21d507d9-9024-33a8-37c8-b472b3dce7df@blackducksoftware.com> Date: Wed, 6 Dec 2017 16:38:18 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171206211225.zcp2crfr3bssn3xr@alap3.anarazel.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-Forefront-Antispam-Report: CIP:192.231.134.1;IPV:CAL;CTRY:;EFV:NLI;SFV:NSPM;SFS:(10009020)(346002)(376002)(2980300002)(448002)(199004)(24454002)(189003)(36756003)(86362001)(5660300001)(31686004)(54906003)(58126008)(53416004)(93886005)(31696002)(53546010)(65826007)(110136005)(47776003)(67846002)(2950100002)(65806001)(229853002)(316002)(8936002)(478600001)(65956001)(83506002)(26826003)(77096006)(85326001)(33646002)(50466002)(356003)(106466001)(2906002)(4326008)(6246003)(23676004)(76176011)(6266002)(53936002)(8676002)(2486003)(81156014)(64126003)(81166006)(305945005)(104016004)(97736004)(230700001)(217873001);DIR:OUT;SFP:1101;SCL:1;SRVR:DM3PR10MB0874;H:ops-mail01.dc2.lan;FPR:;SPF:PermError;PTR:ErrorRetry;A:1;MX:1;LANG:en; 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So >> the hash table may still be perfectly fine for most keys, and only >> slightly slower for the keys in the sequence. > > Meh, we're talking about adversarial attacks here. Hmmmmm... I found this problem when I dropped 10.1 into a test environment to see what would happen. There was no deliberate attempt to break anything. -- todd