postgres-update-no-conflit.sql

DO $$
DECLARE r RECORD;
BEGIN
  FOR r IN SELECT * FROM t  LOOP 
    BEGIN          

      UPDATE t SET id = 2 WHERE des = 'foo' AND id = r.id;
      UPDATE t SET des = 'bar2' WHERE id = 2 AND id = r.id;  

      EXCEPTION WHEN unique_violation THEN
        RAISE NOTICE 'Oups .. there was a conflict on % - %',r.id,r.des;
    END;    
    END LOOP;

END$$;