Re: Requiring recovery.signal or standby.signal when recovering with a backup_label

Hi,

On 2023-11-14 09:13:44 +0900, Michael Paquier wrote:
> On Mon, Nov 13, 2023 at 03:41:44PM -0800, Andres Freund wrote:
> > On 2023-11-09 12:16:52 +0900, Michael Paquier wrote:
> >> On Thu, Nov 09, 2023 at 12:04:19PM +0900, Michael Paquier wrote:
> >> > Sure, sorry for the confusion. By "we'd do nothing", I mean precirely
> >> > "to take no specific action related to archive recovery and recovery
> >> > parameters at the end of recovery", meaning that a combination of
> >> > backup_label with no signal file would be the same as crash recovery,
> >> > replaying WAL up to the end of what can be found in pg_wal/, and only
> >> > that.
> >
> > I don't think those are equivalent - in the "backup_label with no signal file"
> > case we start recovery at a different location than the "crash recovery" case
> > does.
>
> It depends on how you see things, and based on my read of the thread
> or the code we've never really put a clear definition what a
> "backup_label with no signal file" should do. The definition I was
> suggesting is to make it work the same way as crash recovery
> internally:
> - use the start LSN from the backup_label.

That's fundamentally different from crash recovery!

> - replay up to the end of local WAL.
> - don't rely on any recovery GUCs.
> - if at the end of recovery replay has not reached the end-of-backup
> record, then fail.

Also different from crash recovery.

It doesn't make sense to me to say "work the same way" when there are such
fundamental differences.

Greetings,

Andres Freund