| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Boszormenyi Zoltan <zb(at)cybertec(dot)at>, Dimitri Fontaine <dfontaine(at)hi-media(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Synchronization levels in SR |
| Date: | 2010-09-08 14:22:46 |
| Message-ID: | 1283955766.7516.1838.camel@ebony |
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| Lists: | pgsql-hackers |
On Wed, 2010-09-08 at 09:50 -0400, Robert Haas wrote:
> So that means we have to make sure that none of the effects of a
> transaction can be seen until WAL is fsync'd on the master AND the
> slave has acked.
Yes, that's right. And I like your example; one for the docs.
There is a slight complexity there: An application might connect to the
standby and see the changes made by the transaction, even though the
master has not yet been notified, but will be in a moment. I don't see
that as an issue though, but worth mentioning cos its just the
"Byzantine Generals" problem.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Training and Services
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