RE: pg_createsubscriber does not check output_plugin_libraries

Dear Jacob,

> > + /*
> > + * Should not happen. (Frontend and backend GUC_LIST_QUOTE parsing
> > + * have to remain compatible for pg_dump at minimum.)
> > + */
>
> I spun for a while on the network compatibility implications of this,
> until I realized that pg_createsubscriber isn't going to work if the
> source server is a different major version (even though it doesn't
> explicitly check the source server's version, AFAICT?).

Your understanding is correct. IIUC, pg_createsubscriber ensures that
1) the major version of the target server is same as the pg_createsubscriber's one, and
2) the target is working as a hot standby of a source.

These points ensure that all source, target and the executable have a same major
versions.

> If that's
> correct, this code should be fine. I haven't reviewed line-by-line,
> but the general approach LGTM.

OK. But the comment can be simpler just like "Should not happen". IIRC pg_dump
command is not used here.

Best regards,
Hayato Kuroda
FUJITSU LIMITED