From:
Robert Haas <robertmhaas(at)gmail(dot)com>
To:
Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc:
Markus Wanner <markus(at)bluegap(dot)ch>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, MARK CALLAGHAN <mdcallag(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject:
Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled
synchronous replication.
Date:
2011-03-18 21:18:28
Message-ID:
AANLkTinaE8pKZ5RyVShF8ZwDF2+GGQ1bZ_Y-jfO2rLAK@mail.gmail.com (view raw or flat )
Thread:
2011-03-06 22:51:56 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-06 23:09:53 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-06 23:28:45 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 07:29:48 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 07:48:11 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 07:54:19 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 13:30:34 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 14:02:44 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 14:21:46 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 14:29:04 from Aidan Van Dyk <aidan(at)highrise(dot)ca>
2011-03-07 15:03:10 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 15:13:46 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-07 15:46:52 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 15:51:49 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 16:09:49 from Alvaro Herrera <alvherre(at)commandprompt(dot)com>
2011-03-18 09:27:13 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 13:16:24 from MARK CALLAGHAN <mdcallag(at)gmail(dot)com>
2011-03-18 13:30:56 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 13:40:22 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 14:37:26 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 16:03:03 from MARK CALLAGHAN <mdcallag(at)gmail(dot)com>
2011-03-18 14:19:18 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 14:52:13 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 15:43:38 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 15:47:46 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-18 16:19:31 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 16:33:26 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 16:48:57 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 17:35:46 from Greg Stark <gsstark(at)mit(dot)edu>
2011-03-18 19:17:56 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 19:19:06 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 19:29:50 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 19:34:18 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 19:41:00 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 21:08:11 from Aidan Van Dyk <aidan(at)highrise(dot)ca>
2011-03-18 21:26:00 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-22 20:33:11 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-23 07:27:13 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-23 11:52:22 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-23 12:16:39 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-23 15:24:30 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 21:18:28 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 21:24:03 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 21:30:04 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 21:43:32 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 21:48:33 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 22:47:54 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-19 19:27:04 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-25 12:12:05 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-18 16:27:57 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 19:22:20 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 14:19:56 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 15:52:18 from MARK CALLAGHAN <mdcallag(at)gmail(dot)com>
2011-03-07 15:04:22 from Aidan Van Dyk <aidan(at)highrise(dot)ca>
2011-03-07 14:55:11 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-06 23:28:13 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2011-03-06 23:36:30 from Jaime Casanova <jaime(at)2ndquadrant(dot)com>
2011-03-06 23:38:30 from Jaime Casanova <jaime(at)2ndquadrant(dot)com>
2011-03-06 23:52:49 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 08:27:16 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-07 08:44:52 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-07 09:30:35 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 09:47:20 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-10 21:28:12 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 14:10:03 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-19 01:12:52 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2011-03-23 15:53:30 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-07 09:20:07 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 09:28:25 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-07 11:21:39 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-10 20:04:57 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-11 10:46:03 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-17 17:46:37 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-17 17:56:36 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 06:25:06 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-18 12:25:49 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 14:55:56 from Greg Stark <gsstark(at)mit(dot)edu>
2011-03-18 15:07:23 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 15:40:57 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-25 11:53:15 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-17 17:52:56 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 05:45:44 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-18 07:52:07 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 12:16:08 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-10 20:44:33 from Robert Haas <robertmhaas(at)gmail(dot)com>
Lists:
pgsql-committers pgsql-hackers
On Fri, Mar 18, 2011 at 3:29 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Fri, 2011-03-18 at 20:19 +0100, Markus Wanner wrote:
>> Simon,
>>
>> On 03/18/2011 05:19 PM, Simon Riggs wrote:
>> >>> Simon Riggs<simon(at)2ndQuadrant(dot)com> wrote:
>> >>>> In PostgreSQL other users cannot observe the commit until an
>> >>>> acknowledgement has been received.
>>
>> On other nodes as well? To me that means the standby needs to hold back
>> COMMIT of an ACKed transaction, until receives a re-ACK from the master,
>> that it committed the transaction there. How else could the slave know
>> when to commit its ACKed transactions?
>
> We could do that easily enough, actually, if we wished.
>
> Do we wish?
Seems like it would be nice, but isn't it dreadfully expensive?
Wouldn't you need to prevent the slave from applying the WAL until the
master has released the sync rep waiters? You'd need a whole new
series of messages back and forth.
Since the current solution is intended to support data-loss-free
failover, but NOT to guarantee a consistent view of the world from a
SQL level, I doubt it's worth paying any price for this. Certainly in
the hot_standby=off case it's a nonissue. We might need to think
harder about it when and if someone impements an 'apply' level though,
because this would seem more of a concern in that case (though I
haven't thought through all the details).
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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