Re: restoring wal archive and pg_xlog dir

Jeff Frost <jeff@frostconsultingllc.com> writes:
> 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?

Segment files pulled from the archive are saved using temporary file
names (and then deleted after being replayed).  For obvious safety
reasons, we try never to overwrite any xlog file in either the archive
or local storage.

> 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?

Certainly.  If you don't have wal data spanning the entire time that the
base backup is being taken, the backup is useless because there's no way
to make it consistent.

            regards, tom lane