CREATE OR REPLACE FUNCTION tuomin() 
   RETURNS VOID 
 AS
 $$
 DECLARE 
    t_row RECORD;
 BEGIN
     FOR t_row in (SELECT * FROM userx) LOOP
         update userx set usr ='xxx'; 
     END LOOP;
 END;
 $$
 LANGUAGE plpgsql;SELECT tuomin() as output;