Re: BUG #18544: Setting local config_parameter to DEFAULT behaves unexpectedly when using period in config name

On Thursday, July 18, 2024, Hayden Sim <haydenwillsim(at)gmail(dot)com> wrote:

> Hi,
>
> I think the most confusing part is the documentation saying:
> """
> DEFAULT can be written to specify resetting the parameter to its
> default value (that is, whatever value it would have had if no SET had
> been executed in the current session).
> """
>
> It would be expected that subsequent calls to `current_setting()` should
> throw an error (without the "t" parameter.) As would have been the case if
> `SET` hadn't ever been executed in the session. This is increasingly
> confusing when a call to `SET LOCAL "foo.bar" TO 'baz';` runs inside a
> transaction, as this will affect behaviour outside of the transaction. As
> can be seen here:
>

I need to review exactly what I changed but my Document NULL patch in the
commitfest does cover this behavior. In short you cannot rely on either
the error or NULL to represent unknown/unset. The system was not designed
to allow settings that were not externally defined to the session to be
used. If externally defined every setting both exists and has a non-null
value.

David J.