Re: Remove Deprecated Exclusive Backup Mode

Hi,

On 2019-02-24 14:35:04 -0800, Christophe Pettus wrote:
> > On Feb 24, 2019, at 14:19, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> > You say above that the new interface is unquestionably an improvement
> > and here say that we shouldn't deprecate the old one in favor of it
> > (even though we actually already have... but that's beside the point I'm
> > trying to make here), so what you're advocating for is that we keep an
> > old and known broken interface that we know causes real issues even
> > after we've developed a new and unquestionably better one.
>
> Yes, I am advocating exactly that. The reason that I think we need to
> keep the old one (or, at least, not remove it as soon as 12) is that
> creating an obstacle to upgrades is worse than retaining the old one,
> and it *will* be an obstacle to upgrades (or to using the community
> edition at all).

It sounds to me like you treat this as if having the old method around
had no downsides. But I have seen *numereous* downtimes due to it, and
also corruption triggered by it (people following the hint to remove
backup_label).

> > A lot of them depended on pg_wal being named pg_xlog too, but we seem to
> > have managed reasonably well through that, not to mention all the
> > catalog changes that caused issues for monitoring, etc.
>
> Some of the incompatible catalog changes (in particular, in
> pg_stat_activity) I thought were gratuitous, but we did them, and no
> point in relitigating that now. I'd say that the internal layout of
> PGDATA is fairly weak promise compared to an SQL-level construct,
> especially one as widely used as pg_start_backup().

I don't buy that, because you normally specifically should exclude
pg_xlog/pg_wal from basebackups.

Greetings,

Andres Freund