Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1a0xer-0005Ri-3a for pgsql-admin@arkaria.postgresql.org; Mon, 23 Nov 2015 20:24:17 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84) (envelope-from ) id 1a0xeq-0005bB-DW for pgsql-admin@arkaria.postgresql.org; Mon, 23 Nov 2015 20:24:16 +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 1a0xep-0005au-UP for pgsql-admin@postgresql.org; Mon, 23 Nov 2015 20:24:15 +0000 Received: from mailout.easymail.ca ([64.68.201.169]) by magus.postgresql.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.84) (envelope-from ) id 1a0xel-0001xk-TW for pgsql-admin@postgresql.org; Mon, 23 Nov 2015 20:24:15 +0000 Received: from localhost (localhost [127.0.0.1]) by mailout.easymail.ca (Postfix) with ESMTP id D4514E88B; Mon, 23 Nov 2015 15:24:08 -0500 (EST) X-Virus-Scanned: Debian amavisd-new at mailout.easymail.ca X-Spam-Flag: NO X-Spam-Score: -3.707 X-Spam-Level: X-Spam-Status: No, score=-3.707 required=5 tests=[ALL_TRUSTED=-1.8, AWL=-0.000, BAYES_00=-2.599, DNS_FROM_AHBL_RHSBL=0.692] Received: from mailout.easymail.ca ([127.0.0.1]) by localhost (easymail-mailout.easydns.vpn [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id TtGaDMIUrfHK; Mon, 23 Nov 2015 15:24:08 -0500 (EST) Received: from [192.168.1.23] (unknown [65.156.52.179]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mailout.easymail.ca (Postfix) with ESMTPSA id 857D6E352; Mon, 23 Nov 2015 15:24:08 -0500 (EST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) Subject: Re: Question on Hot Standby in PostgreSQL From: Scott Ribe In-Reply-To: Date: Mon, 23 Nov 2015 13:24:07 -0700 Cc: "pgsql-admin@postgresql.org" Content-Transfer-Encoding: quoted-printable Message-Id: <88C8194B-0F69-4CEA-9DB4-5A21D156D2DE@elevated-dev.com> References: To: "Williams, Alex" X-Mailer: Apple Mail (2.2104) X-Pg-Spam-Score: -2.6 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-admin Precedence: bulk Sender: pgsql-admin-owner@postgresql.org On Nov 20, 2015, at 12:50 PM, Williams, Alex wrote: >=20 > However, I thought with the use of MVCC, > an active query on the slave (long running, 30 seconds+) can run reading > from row xid versions/snapshot... The problem is that the master could well make changes that would remove ro= ws in that snapshot because the master does not know anything about the row= s that need preserving for the replica's query. That said, IIRC there may be something in 9.4 or 9.5 which provides for the= replica to send that info to the server in order to coordinate things, but= I haven't used that and so cannot offer more. --=20 Scott Ribe scott_ribe@elevated-dev.com http://www.elevated-dev.com/ https://www.linkedin.com/in/scottribe/ (303) 722-0567 voice --=20 Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin