Re: needless complexity in StartupXLOG

On Mon, Jul 26, 2021 at 4:15 PM Stephen Frost <sfrost@snowman.net> wrote:
> All I was really trying to point out above was that the comment might be
> improved upon, just so someone understands that we aren't doing a
> checkpoint at this particular place, but one will be done later due to
> the promotion.  Maybe I'm being a bit extra with that, but that was my
> thought when reading the code and the use of the promoted flag variable.

Yeah, I agree, it confused me too, at first.

> Yeah ... not to mention that it really is just incredibly dangerous to
> use such an approach for PITR.  For my 2c, I'd rather we figure out a
> way to prevent this than to imply that we support it when we have no way
> of knowing if we actually have replayed far enough to be consistent.
> That isn't to say that using snapshots for database backups isn't
> possible, but it should be done in-between pg_start/stop_backup calls
> which properly grab the returned info from those and store the backup
> label with the snapshot, etc.

My position on that is that I would not particularly recommend the
technique described here, but I would not choose to try to block it
either. That's an argument for another thread, though.

-- 
Robert Haas
EDB: http://www.enterprisedb.com