Re: patch proposal

On Wed, Aug 17, 2016 at 12:06 AM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:

> Greetings,
>
> * Venkata B Nagothi (nag1010(at)gmail(dot)com) wrote:
> > The above said parameters can be configured to pause, shutdown or prevent
> > promotion only after reaching the recovery target point.
> > To clarify, I am referring to a scenario where recovery target point is
> not
> > reached at all ( i mean, half-complete or in-complete recovery) and there
> > are lots of WALs still pending to be replayed - in this situation,
>
> PG doesn't know that there are still WALs to be replayed.
>

PG doesn't know that there are still WALs to be replayed. Since, i have
given an particular recovery target and PG knows the current replay
position,
I would say, it would be good if PG warns and pauses there by saying
recovery target point is not reached.

> It would be nice if PostgreSQL pauses the recovery in-case its not
> complete
> > (because of missing or corrupt WAL), shutdown the cluster and allows the
> > DBA to restart the replay of the remaining WAL Archive files to continue
> > recovery (from where it stopped previously) until the recovery target
> point
> > is reached.
>

Agreed. Reaching end-of-WAL is not an error. It sounds more like a
limitation in certain scenarios.

Reaching the end of WAL isn't an error and I don't believe it makes any
> sense to treat it like it is. You can specify any recovery target point
> you wish, including ones that don't exist, and that's not an error
> either.
>
> I could see supporting an additional "pause" option that means "pause at
> the end of WAL if you don't reach the recovery target point". I'd also
> be happy with a warning being emitted in the log if the recovery target
> point isn't reached before reaching the end of WAL, but I don't think it
> makes sense to change the existing behavior.
>

Agreed. Additional option like "pause" would. As long as there is an option
to ensure following happens if the recovery target is not reached -

a) PG pauses the recovery at the end of the WAL
b) Generates a warning in the log file saying that recovery target point
is not reached (there is a patch being worked upon on by Thom on this)
c) Does not open-up the database exiting from the recovery process by
giving room to resume the replay of WALs

Regards,
Venkata B N

Fujitsu Australia