To: Josh Berkus <josh@agliodbs.com>
cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: PostgreSQL as a local in-memory cache 
In-reply-to: <4C1AA949.7050301@agliodbs.com> 
References: <cb0fb58c-9134-4314-a1d0-08fc39f911a6@40g2000pry.googlegroups.com>
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	<4C1A5B81.8050908@agliodbs.com> <m2typ18ow0.fsf@hi-media.com>
	<4C1AA949.7050301@agliodbs.com>
Comments: In-reply-to Josh Berkus <josh@agliodbs.com>
	message dated "Thu, 17 Jun 2010 16:01:29 -0700"
Date: Thu, 17 Jun 2010 19:25:11 -0400
Message-ID: <28137.1276817111@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Josh Berkus <josh@agliodbs.com> writes:
>> (a) and (d) are probably simple, if by "reprovisioning" you mean
>> "rm -rf $PGDATA; initdb".

> Exactly.  Followed by "scp database_image".  Or heck, just replacing the
> whole VM.

Right, that would work.  I don't think you really need to implement that
inside Postgres.  I would envision having the startup script do it, ie

	rm -rf $PGDATA
	cp -pr prepared-database-image $PGDATA

	# this loop exits when postmaster exits normally
	while ! postmaster ...
	do
		rm -rf $PGDATA
		cp -pr prepared-database-image $PGDATA
	done

Then all you need is a tweak to make the postmaster exit(1) after
a crash instead of trying to launch recovery.

			regards, tom lane