get metadata about function with table.column%type-argument in postgres

Question

Is it possible to find out if an argument in a function in postgres was defined as

table.column%type foo

or

sometype foo

querying e.g. pg_proc?

Answer 1

The proargtypes column in pg_proc is an array of the types of all the function's arguments. Each type can then be cross-referenced to pg_type.oid.

So if I define a function like this:

steve@steve@[local] =# create function testfunc(pg_proc.proname%type) returns boolean language 'sql' immutable strict as $$ select true $$;
NOTICE:  type reference pg_proc.proname%TYPE converted to name
CREATE FUNCTION

Well, that notice isn't too hopeful.

The pg_proc entry for that function is:

 proname  | proargtypes
----------+-------------
 testfunc | 19

and type 19 is just "name". so it looks like the answer here is "no", I'm afraid.