Re: No discussion of custom variables; no "See also" for set_config, current_setting, pg_settings

PG Doc comments form <noreply(at)postgresql(dot)org> writes:
> A reader of this section
> https://www.postgresql.org/docs/current/sql-set.html of the documentation
> might be forgiven for thinking that Postgres does not support custom
> variables.

They are, in fact, *not* a supported feature. The only intended use
of non-core GUCs was for extensions' parameters. People have abused the
mechanism to create ad-hoc session variables, but we don't encourage it.
The underlying code won't scale to large numbers of variables, there's
no way to declare properties of such a variable in SQL, etc.

There's been an ongoing effort to create a respectable substitute,
but it still hasn't gotten across the finish line [1].

regards, tom lane

[1] https://commitfest.postgresql.org/39/1608/