Find out if a parameter/return field is NULLABLE using Describe

It doesn't seem to be possible to find out if a parameter or result
field is nullable using the Describe protocol.

For example if I have this table and statement:

create table employees (
id serial not null primary key,
name text not null,
email text <-- this field
);

insert into employees (name, email) values ($1, $2);

Then the only information I get back about $2 is that it's a TEXT (OID
= 25), when clearly $1 and $2 are different in that one is nullable
and the other isn't.

Similarly,

select name, email from employees;

This time I get more information about the types, including a modifier
and length, but I can't see whether that lets me find out that one
could be NULL and the other can never be.

So is this possible?

Rich.

--
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
Team Notepad - intranets and extranets for business - http://team-notepad.com