Re: Remove Deprecated Exclusive Backup Mode

On Tue, Feb 26, 2019 at 3:49 PM David Steele <david@pgmasters.net> wrote:
>
> On 2/26/19 6:51 AM, Michael Paquier wrote:
> > On Mon, Feb 25, 2019 at 08:17:27PM +0200, David Steele wrote:
> >> Here's the really obvious bad thing: if users do not update their procedures
> >> and we ignore backup_label.pending on startup then they will end up with a
> >> corrupt database because it will not replay from the correct checkpoint.  If
> >> we error on the presence of backup_label.pending then we are right back to
> >> where we started.
> >
> > Not really.  If we error on backup_label.pending, we can make the
> > difference between a backend which has crashed in the middle of an
> > exclusive backup without replaying anything and a backend which is
> > started based on a base backup, so an operator can take some action to
> > see what's wrong with the server.  If you issue an error, users can
> > also see that their custom backup script is wrong because they forgot
> > to rename the flag after taking a backup of the data folder(s).
>
> The operator still has a decision to make, manually, just as they do
> now.  The wrong decision may mean a corrupt database.

Even in non-exclusive backup mode, the wrong decision may mean
a corrupt database. For example, what if the user may forget to save
the backup_label in the backup taken by using non-exclusive backup
method? So I'm not sure if this is the matter only for an exclusive backup.

Regards,

-- 
Fujii Masao