Subject: Re: New trigger option of pg_standby
From: Simon Riggs <simon@2ndQuadrant.com>
To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: Fujii Masao <masao.fujii@gmail.com>,
	Guillaume Smet <guillaume.smet@gmail.com>,
	Tom Lane <tgl@sss.pgh.pa.us>, Peter Eisentraut <peter_e@gmx.net>,
	Kevin Grittner <Kevin.Grittner@wicourts.gov>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
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Date: Tue, 21 Apr 2009 12:03:56 +0100
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On Mon, 2009-04-20 at 17:47 +0300, Heikki Linnakangas wrote:

> At the end of archive recovery, the server always probes for the 
> timeline by requesting history files until it fails to find one. That 
> probing should remove the trigger file if it hasn't been removed by 
> then. It's a bit coincidental to rely on that, but at least it's simple. 
> The assumption we're making is that the server won't exit recovery 
> before asking restore_command for a file that doesn't exist.

If you really want to simplify this, then we should have a final_command
parameter for a command to be executed at the end of recovery. That
would make the change to pg_standby very simple and allow for a very
simple final_command also. That would make the logic similar to what we
do for aggregates: transition function and final function. 

We could call it restore_cleanup_command or something similar.

I suspect this option will make you consider Fujii-san's patch in a
better light. :-)

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support