Re: New trigger option of pg_standby

Simon Riggs wrote:
> 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.

Hmm, that might indeed be a cleaner interface. However, that throws the
idea of backpatching out of the window, and will make it impossible to
run a PG 8.4 pg_standby against a PG 8.3 server. Do we want to add the
new parameter for 8.4 anyway?

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

No, removing trigger file as soon as a non-existant file is requested
still seems simpler than deleting it whenever a timeline history file is
requested.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com