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From: Simon Riggs <simon@2ndQuadrant.com>
To: Markus Wanner <markus@bluegap.ch>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: MARK CALLAGHAN <mdcallag@gmail.com>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: Aidan Van Dyk <aidan@highrise.ca>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication.
Date: Fri, 18 Mar 2011 19:29:50 +0000
Message-ID: <1300476590.18619.18115.camel@ebony> (raw)
In-Reply-To: <4D83B02A.5090105@bluegap.ch>
References: <E1PwMns-00047O-UU@gemulon.postgresql.org>
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	<4D74896C.5030402@enterprisedb.com>
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	<4D832B4D020000250003BA98@gw.wicourts.gov>
	<4D837EA2.2070205@enterprisedb.com>
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	<4D83B02A.5090105@bluegap.ch>

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@2ndQuadrant.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?

> > No, only in the case where you choose not to failover to the standby
> > when you crash, which would be a fairly strange choice after the effort
> > to set up the standby. In a correctly configured and operated cluster
> > what I say above is fully correct and needs no addendum.
> 
> If you don't failover, how can the standby be ahead of the master, given
> it takes measures not to be during normal operation?
> 
> Eager to understand... ;-)
> 
> Regards
> 
> Markus

-- 
 Simon Riggs           http://www.2ndQuadrant.com/books/
 PostgreSQL Development, 24x7 Support, Training and Services
 




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  Cc: simon@2ndQuadrant.com, markus@bluegap.ch, heikki.linnakangas@enterprisedb.com, Kevin.Grittner@wicourts.gov, mdcallag@gmail.com, alvherre@commandprompt.com, andrew@dunslane.net, aidan@highrise.ca, pgsql-hackers@postgresql.org
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