CREATE OR REPLACE FUNCTION fu_to_hex (
  p_val numeric
)
RETURNS text AS
$body$
DECLARE
  l_hex TEXT := '';
  l_val NUMERIC(64, 0) := abs($1);
BEGIN
  WHILE l_val > 0 LOOP
    l_hex := concat(
               CASE 
                 WHEN mod(l_val, 16) < 10
                 THEN chr(CAST(mod(l_val, 16) + 48 AS INTEGER))
                 ELSE chr(CAST(mod(l_val, 16) + 55 AS INTEGER)) 
               END, 
               l_hex
             );
    l_val := div(l_val, 16);
  END LOOP;
  IF(l_hex = '')
  THEN
    l_hex := '0';
  END IF;
  RETURN l_hex;
END;
$body$
LANGUAGE 'plpgsql'
IMMUTABLE
RETURNS NULL ON NULL INPUT
SECURITY INVOKER;