Re: Proposal for 9.1: WAL streaming from WAL buffers - Mailing list pgsql-hackers

From Simon Riggs
Subject Re: Proposal for 9.1: WAL streaming from WAL buffers
Date
Msg-id 1277128238.32273.1729.camel@ebony
Whole thread Raw
In response to Re: Proposal for 9.1: WAL streaming from WAL buffers  (Fujii Masao <masao.fujii@gmail.com>)
Responses Re: Proposal for 9.1: WAL streaming from WAL buffers  (Bruce Momjian <bruce@momjian.us>)
List pgsql-hackers
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.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Development, 24x7 Support, Training and Services



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