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Re: [PATCHES] Infrastructure changes for recovery

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: List pgsql-patches <pgsql-patches(at)postgresql(dot)org>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCHES] Infrastructure changes for recovery
Date: 2008-09-18 13:06:36
Message-ID: 16992.1221743196@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Simon Riggs <simon(at)2ndQuadrant(dot)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

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