Re: Change pg_last_xlog_receive_location not to move backwards

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Change pg_last_xlog_receive_location not to move backwards
Date: 2011-02-15 12:41:37
Message-ID: AANLkTik8eizaG3nq+v5aOK9GH-7ZH3YgQA6gLnNjC=9x@mail.gmail.com
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On Tue, Feb 15, 2011 at 12:34 AM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> You suggest that the shared variable Stream tracks the WAL write location,
> after it's set to the replication starting position? I don't think
> that the write
> location needs to be tracked in the shmem because other processes than
> walreceiver don't use it.

Well, my proposal was to expose it, on the theory that it's useful.
As we stream the WAL, we write it, so I think for all intents and
purposes write == stream. But using it to convey the starting
position makes more sense if you call it stream than it does if you
call it write.

> You propose to rename LogstreamResult.Write to .Stream, and
> merge it and receiveStart?

Yeah, or probably change recieveStart to be called Stream. It's
representing the same thing, just in shmem instead of backend-local,
so why name it differently?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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