Re: restoring wal archive and pg_xlog dir

On Thu, 2005-06-23 at 10:55 -0700, Jeff Frost wrote:
> When reading the docs on recovery.conf, I noticed this:
>
> WAL segments that cannot be found in the archive will be sought in pg_xlog/;
> this allows use of recent un-archived segments. However segments that are
> available from the archive will be used in preference to files in pg_xlog/. The
> system will not overwrite the existing contents of pg_xlog/ when retrieving
> archived files.
>
> If the system will use the files in the archive in preference to the ones in
> pg_xlog, how can this actually happen if it will not overwrite the contents of
> pg_xlog?

That was the bit I thought of. The files are streamed in one by one using a temp filename, so you never run out of space no matter how big the archive of transaction logs. Thats an important feature if a base backup goes bad and you have to go back to n-1 base backup.

> I also noticed that if there is not at least one wal archive available in
> the archive or the pg_xlog dir, the restore errors out and exits. So the
> base backup is really not complete without at least one wal archive
> following it. Is this by design?

That was the bit I didn't. Fix partially implemented and I am to submit
for 8.1, godspeed my typing fingers. There's a simple workaround if you
have a low transaction rate system: load up enough data to trip into the
next xlog.

Best Regards, Simon Riggs