To: Simon Riggs <simon@2ndQuadrant.com>
cc: List pgsql-patches <pgsql-patches@postgresql.org>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PATCHES] Infrastructure changes for recovery 
In-reply-to: <1221725145.3913.2315.camel@ebony.2ndQuadrant> 
References: <1218109459.4549.423.camel@ebony.2ndQuadrant>
	<1220213074.4371.173.camel@ebony.2ndQuadrant>
	<1905.1220895241@sss.pgh.pa.us>
	<1221080797.3913.768.camel@ebony.2ndQuadrant>
	<15776.1221594318@sss.pgh.pa.us>
	<1221725145.3913.2315.camel@ebony.2ndQuadrant>
Comments: In-reply-to Simon Riggs <simon@2ndQuadrant.com>
	message dated "Thu, 18 Sep 2008 09:05:45 +0100"
Date: Thu, 18 Sep 2008 09:06:36 -0400
Message-ID: <16992.1221743196@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Simon Riggs <simon@2ndQuadrant.com> writes:
> Having some trouble trying to get a clean state change from recovery to
> normal mode.

> Startup needs to be able to write WAL at the end of recovery so it can
> write a ShutdownCheckpoint, yet must not be allowed to write WAL before
> that. Other services are still not fully up yet. So every other process
> apart from Startup musn't write WAL until Startup has fully completed
> its actions, which is sometime later.
> ...
> We *might* solve this by making the final checkpoint that Startup writes
> into an online checkpoint.

Do we really need a checkpoint there at all?  I can't recall right now
if there was a good reason why Vadim made it do that.  I have a feeling
that it might have had to do with an assumption that the recovery
environment was completely distinct from live environment; which is a
statement that's certainly not going to be true in a query-answering
slave.

			regards, tom lane