Re: Updated backup APIs for non-exclusive backups

On Tue, Mar 29, 2016 at 11:39 PM, Magnus Hagander <magnus(at)hagander(dot)net>
wrote:

> On Tue, Mar 29, 2016 at 6:40 PM, Magnus Hagander <magnus(at)hagander(dot)net>
> wrote:
>
>> So - I can definitely see the argument for returning the stop wal
>> *location*. But I'm still not sure what the definition of the time would
>> be? We can't return it before we know what it means...
>>
>
>
> I had a chat with Heikki, and here's another suggestion:
>
> 1. We don't touch the current exclusive backups at all, as previously
> discussed, other than deprecating their use. For backwards compat.
>
> 2. For new backups, we return the contents of pg_control as a bytea from
> pg_stop_backup(). We tell backup programs they are supposed to write this
> out as pg_control.backup, *not* as pg_control.
>
> 3a. On recovery, if it's an exlcusive backup, we do as we did before.
>
> 3b. on recovery, in non-exclusive backups (determined from backup_label),
> we check that pg_control.backup exists *and* that pg_control does *not*
> exist.
>

Currently pg_control has been read before backup_label file, so as per this
proposal do you want to change that? If yes, I think that will make this
patch more invasive with respect to handling of failure modes. Also as
David points out, I also feel that it will raise the bar for usage of this
API.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com