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Re: synchronous_commit and remote_write

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: synchronous_commit and remote_write
Date: 2012-05-09 14:02:23
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On 9 May 2012 13:48, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, May 9, 2012 at 7:29 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> Let me point out that our documentation says nothing about it being
>> written to the kernel --- it just says "has received the commit record
>> of the transaction to memory."
> Maybe remote_receive would be better.  If we're actually writing it
> back to the kernel before acknowledging the commit, that seems like an
> implementation defect more than anything else, since it does not -
> AFAICS - provide any additional, useful guarantee.

It does provide an additional guarantee, but I accept you personally
may not find that useful.

If the docs don't describe it well enough, then we can change the docs.

> Another thing I've been wondering is whether, perhaps, we ought to
> keep synchronous_commit tri-valued: on/local/off, and have a separate
> GUC for synchronous_replication_mode.  It's a bit arbitrary that "on"
> happens to mean remote fsync rather than remote write/receive.

You mean the way it originally was? I would agree.

 Simon Riggs         
 PostgreSQL Development, 24x7 Support, Training & Services

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