| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, MARK CALLAGHAN <mdcallag(at)gmail(dot)com>, Markus Wanner <markus(at)bluegap(dot)ch>, 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 16:19:31 |
| Message-ID: | 1300465171.18619.15193.camel@ebony |
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| Lists: | pgsql-committers pgsql-hackers |
On Fri, 2011-03-18 at 17:47 +0200, Heikki Linnakangas wrote:
> On 18.03.2011 16:52, Kevin Grittner wrote:
> > Simon Riggs<simon(at)2ndQuadrant(dot)com> wrote:
> >
> >> In PostgreSQL other users cannot observe the commit until an
> >> acknowledgement has been received.
> >
> > Really? I hadn't picked up on that. That makes for a lot of
> > complication on crash-and-recovery of a master, but if we can pull
> > it off, that's really cool. If we do that and MySQL doesn't, we
> > definitely don't want to use the same terminology they do, which
> > would imply the same behavior.
>
> To be clear: other users cannot observe the commit until standby
> acknowledges it - unless the master crashes while waiting for the
> acknowledgment. If that happens, the commit will be visible to everyone
> after recovery.
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.
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
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