SRF Functions don't want to return empty tuple

Hi

I have a problem with SRF functions on a RedHat 8.0 system with PostgreSQL
7.3.2.

Schema is following :

CREATE TABLE public.agents (
numero_age int4 NOT NULL,
nom_age varchar(30) NOT NULL,
prenom_age varchar(30) NOT NULL,
date_entree_age date NOT NULL,
identite varchar(50),
CONSTRAINT agents_pkey PRIMARY KEY (numero_age)
) WITH OIDS;

INSERT INTO public.agents VALUES (78888, 'PERAVIF', 'JO', '1967-06-18', '')

CREATE FUNCTION public.liste_agents(int4) RETURNS public.agents AS 'SELECT *
FROM agents WHERE numero_age = $1' LANGUAGE 'sql' VOLATILE;

When, I try :

SELECT * FROM liste_agents(78888)

Everything is Ok, I get my agent. But if I try :

SELECT * FROM liste_agents(0) (... or any other numero_age not in the
table...)

I get a error message :

ExecMakeTableFunctionResult: Invalid result from function returning tuple

What's wrong ? I guessed null values returned by the query didn't match
fields declared not null in the table schema, so I create a custom type
(with CREATE TYPE) but it neither doesn't work. Hint (?) : I've activated
Plpython for this Database.

Thanks
Eric GRIMOIS
Concepteur de logiciels
SEI - CPAM du Val d'Oise