Bug in UPDATE RULE?

I have the following tables:

  CREATE TABLE orders(
    order_id int4 NOT NULL,
    state char DEFAULT 'R',
    whochanged text DEFAULT 'auto');

  CREATE TABLE orders_timeline(
    order_id int4 NOT NULL,
    oldstate char NOT NULL,
    newstate char NOT NULL,
    whochanged text NOT NULL);

I want to track all changes to table orders in orders_timeline.  For
this purpose, I have made the following rules:

  CREATE RULE orders_ins_r AS ON INSERT TO orders
    DO INSERT INTO orders_timeline
    (order_id, oldstate, newstate, whochanged)
    VALUES (CURRENT.order_id, '-', CURRENT.state, CURRENT.whochanged);

  CREATE RULE orders_upd_r AS ON UPDATE TO orders
    DO INSERT INTO orders_timeline
    (order_id, oldstate, newstate, whochanged)
    VALUES (CURRENT.order_id, CURRENT.state, NEW.state, NEW.whochanged);

The first one works, and adds a row (#, '-', 'R', 'auto') when a new
order is inserted into the table:

  > insert into orders (order_id) VALUES (1);
  > select * from orders_timeline;
  order_id|oldstate|newstate|whochanged
  --------+--------+--------+----------
         1|       -|R       |auto
  (1 row)


The second one does not work.  It inserts (#, 'M', 'M', 'auto') when I
update the orders table with the following command:

  > update orders set state = 'M', whochanged = 'pere' where order_id = 1;
  > select * from orders_timeline;
  order_id|oldstate|newstate|whochanged
  --------+--------+--------+----------
         1|-       |R       |auto
         1|M       |M       |pere
  (2 rows)

I was expecting the second line to contain (1, 'R', 'M', 'pere').  It
seems that I don't understand what CURRENT and NEW means in a RULE.

Could someone enlighten me, or tell me how this should be done.

I'm using PostgreSQL 6.3.2 on RedHat Linux 5.1.

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##>  Petter Reinholdtsen <##    | pere@td.org.uit.no
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