Function not return zero record

Hello,

I wrote a simple function who checks in a table an address and returns
the id and coordinates of the corresponding address.

The problem is when I run separately the SQL query, it gives me zero (0)
entry when I submit a new address - it is what I want as result - and
when I run my function, it gives me 1 entry with the same address.

Note: I create a pseudo-type to return the result. Is that my problem?

I run Postgresql 7.4 on i686-pc-cygwin (Windows XP), with PostGIS 1.0.

CREATE TABLE adresses (
id int4 PRIMARY KEY DEFAULT nextval('seq_adresse'),
);

SELECT AddGeometryColumn('greffe1','adresses','geom', 4269, 'POINT', 2);

CREATE TYPE getCache AS (id integer,geocode double precision ARRAY[2]);

CREATE FUNCTION getCache(varchar)
RETURNS getCache AS '

SELECT id, ARRAY[x(geom),y(geom)] FROM adresses where adresse = $1;
' LANGUAGE sql;

Best regards

Sylvain Racine