Re: Standby accepts recovery_target_timeline setting?

Greetings,

* Robert Haas (robertmhaas(at)gmail(dot)com) wrote:
> On Wed, Oct 9, 2019 at 8:42 AM Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> > If anything, what we should be doing here is throwing a WARNING or
> > similar that these settings don't make sense, because we aren't going
> > through recovery, and blank them out. If we want to be really cute, we
> > could have the show return something like: <not in recovery>, or
> > similar, but just returning an invalid value because that's what was in
> > the config file is nonsense. SHOW isn't a view of what's in
> > postgresql.conf, it's telling the user what the current system state is.
>
> SHOW is telling the user the value that is configured in the current
> session, which may or may not be the value configured in
> postgresql.conf, but is the value that was configured somewhere. For
> the most part, it's not trying to tell the user what the current
> system state is, although we have a few weird exceptions that behave
> otherwise.

I don't understand this argument and so it seems pretty likely that
we're just not going to agree here. The idea that the GUC system isn't
something that someone can depend on to find out what the current state
of a variable is is just utter nonsense to me. Yes, we have exceptions
to that, and I don't think they're good ones, but the argument that SHOW
doesn't actually return what the state is and instead returns "this is
what this variable was configured to at some point" does not make any
sense to me.

Thanks,

Stephen