Re: CREATE CAST question

"Robert Wimmer" <seppwimmer(at)hotmail(dot)com> writes:
> I want to define a schema qualified domain and create a cast to cast a
> string in the new domain.

Casts between domains and their underlying types are hard-wired into the
system: you don't get to muck with the semantics by doing CREATE CAST.

The correct way to do this is to define a constraint on the domain,
along the lines of

create function is_ok_ident(text) returns bool as '
... return true if you like the string ...
' language plpgsql;

create domain ident as text check (is_ok_ident(value));

regards, tom lane