Re: Proposal for 9.1: WAL streaming from WAL buffers

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Proposal for 9.1: WAL streaming from WAL buffers
Date: 2010-06-30 02:06:18
Message-ID: 201006300206.o5U26IO14657@momjian.us
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Simon Riggs wrote:
> On Mon, 2010-06-21 at 18:08 +0900, Fujii Masao wrote:
>
> > The problem is not that the master streams non-fsync'd WAL, but that the
> > standby can replay that. So I'm thinking that we can send non-fsync'd WAL
> > safely if the standby makes the recovery wait until the master has fsync'd
> > WAL. That is, walsender sends not only non-fsync'd WAL but also WAL flush
> > location to walreceiver, and the standby applies only the WAL which the
> > master has already fsync'd. Thought?
>
> Yes, good thought. The patch just applied seems too much.
>
> I had the same thought, though it would mean you'd need to send two xlog
> end locations, one for write, one for fsync. Though not really clear why
> we send the "current end of WAL on the server" anyway, so maybe we can
> just alter that.

Is this a TODO?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ None of us is going to be here forever. +

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