From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200407220354.i6M3smv21365@candle.pha.pa.us>
Subject: Re: [HACKERS] Point in Time Recovery
In-Reply-To: <2654.1090467742@sss.pgh.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 21 Jul 2004 23:54:48 -0400 (EDT)
Cc: Mark Kirkwood <markir@coretech.co.nz>,
	Simon Riggs <simon@2ndquadrant.com>, pgsql-admin@postgresql.org
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Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Agreed, it might not be possible, but your report does point out a
> > limitation in our implementation --- that a shutdown database contains
> > more information than a backup and the archive logs.  That is not
> > intuitive.
> 
> That's only because you are clinging to the broken assumption that
> pg_xlog/ is part of the database, rather than part of the logs.
> Separate that out as a distinct entity, and all gets better.

Imagine this.   I stop the server.  I have a tar backup and a copy of
the archive.  I should be able to take them to another machine and
recover the system to the point I stopped.

You are saying I need a copy of pg_xlog directory too, and I need to
remove pg_xlog after I untar the data directory and put the saved
pg_xlog into there before I recover.

Should we create a server-side function that forces all WAL files to the
archive, including partially written ones.  Maybe that fixes the problem
with people deleting pg_xlog before they untar.  You tell them to run
the function before recovery.  If the system can't be started, the it is
possible the WAL files are no good too, not sure.

-- 
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