Re: On-line backup and point-in-time recovery (PITR)

On Thu, Aug 18, 2005 at 11:01:27PM -0400, Bruce Momjian wrote:
> Enzo D'addario wrote:

> > 2.What happens with any DB inserts, updates, deletes etc that occur
> > between the SELECT pg_start_backup() and the end of the tar?
> > They would be already logged in the WAL files and already applied in the
> > tarball, do they then get duplicated during log replay in the recover
> > process?
>
> No, the recovery is just like crash recovery and everything comes back
> clean, but you do have to recover to a time _after_ the end of the
> backup. If you want to recover to a time during the backup you have to
> use the previous backup and xlog files.

One important detail is that the system is able to detect whether a
change registered in WAL was already applied to the data files or not.
So if it's already applied, it doesn't need to be applied again.

--
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"La naturaleza, tan frágil, tan expuesta a la muerte... y tan viva"