array aggregate and function array_union like union all in postgresql

CREATE FUNCTION array_union(anyarray, anyarray)
  RETURNS anyarray
  language sql
as $FUNCTION$
    SELECT ARRAY(
        SELECT UNNEST($1)
        UNION ALL
        SELECT UNNEST($2)
    );
$FUNCTION$;


CREATE AGGREGATE array_union (anyarray)
(
sfunc = array_union,
stype = anyarray,
initcond = '{}'
);