I'm becoming familiar with PostgreSQL's ability to define a data type https://www.postgresql.org/docs/current/sql-createtype.html using
CREATE TYPE syntax.
It appears to me that this type does not allow to compose a type out of relations/tables. In other words, I can do this:
CREATE TYPE compfoo AS (f1 int, f2 text);
but I can't do
CREATE TYPE compfoo AS (f1 relation, f2 relation);
I was wondering if my understanding is correct, and if not, how one could achieve the latter?
I want to indicate that I don't have any particular application for it. I would actually be interested in starting a discussion on an application! I am just trying to expand my understanding of this feature which is often touted as a very powerful feature in the extensible DBMS world.