Re: Allow ALTER SYSTEM SET on unrecognized custom GUCs

shihao zhong <zhong950419(at)gmail(dot)com> writes:
> I do like the idea that we should keep the set and the altar system with
> the same behavior. But one thing I am worried about is the typo detected
> here because I usually make that type of mistake myself. I believe we
> should have an extra log to explicitly tell the user this is a `custom
> variable` guc.

I don't think there's any chance of getting away with that. As noted
upthread, a lot of people use placeholder GUCs as a substitute for a
proper session-variable feature. If we ever get real session variables,
we could start to nudge people away from using placeholders; but right
now too many people would complain about the noise of a warning.

> Btw, another aspect I want to better understand is if the superuser session
> called pg_reload_conf with custom variables, does that mean these custom
> variables will override the other active transaction's SET command?

No, a per-session SET will override a value coming from the config file.
That's independent of whether it's a regular or custom GUC.

regards, tom lane