Re: Permissions for CREATE OPERATOR CLASS

Alvaro Herrera <alvherre@atentus.com> writes:
> I was playing around and got this:

> alvh=> create type my_cash (input = cash_in, output = cash_out, internallength = variable);
> ERROR:  TypeCreate: function cash_out(opaque) does not exist

Yeah, the CREATE TYPE code is now much stricter about the allowed
signatures of the I/O functions.  The input function for a type foo
must be one offoo_in(cstring) returns foofoo_in(opaque) returns foofoo_in(cstring) returns opaquefoo_in(opaque) returns
opaque
while the output must be one offoo_out(foo) returns cstringfoo_out(opaque) returns cstringfoo_out(foo) returns
opaquefoo_out(opaque)returns opaque
 
so unless you use "opaque" you cannot use the same I/O function for
two different types.  (Possibly the error message should complain about
foo_out(foo) not foo_out(opaque).)

If we hear a lot of squawks about that, we can discuss how to weaken
the rules ... but IMHO the entire point here is to introduce some type
safety into the use of I/O functions ...
        regards, tom lane