Robert Haas <robertmhaas@gmail.com> writes:
>> Another advantage of this approach is that, IIUC, type input functions
>> can't return a NULL value. So 'pg_klass'::regclass could return 0,
>> but not NULL. On the other hand, toregclass('pg_klass') *could*
>> return NULL, which seems conceptually cleaner.
BTW, another arguable advantage of fixing this via new functions is
that users could write equivalent (though no doubt slower) functions
for use in pre-9.4 releases, and thus not need to maintain multiple
versions of app code that relies on this behavior.
regards, tom lane