update view

I'm trying to update a table through a view and have read up on what
constitutes an 'updatable' view.  I created a simple test case and cannot
get it to update the table through the view.  In the transcript below,
notice that when I update the view, I get 'UPDATE 0' with no error message
or other complaints.  What am I missing?  Does PostgreSQL not support
updating through views?

-- Brian Haney
brian@cybernaut.com

============================ BEGIN SAMPLE ========================

$ psql -f /tmp/viewtest test2
create table peanuts (
  name text,
  age int4,
  height int4,
  weight int4);
CREATE
insert into peanuts values ('Charlie Brown', 50, 24, 75);
INSERT 21228 1
insert into peanuts values ('Snoopy', 21, 18, 25);
INSERT 21229 1
insert into peanuts values ('Lucy van Pelt', 50, 27, 65);
INSERT 21230 1
insert into peanuts values ('Linus van Pelt', 50, 24, 75);
INSERT 21231 1
select * from peanuts;
name          |age|height|weight
--------------+---+------+------
Charlie Brown | 50|    24|    75
Snoopy        | 21|    18|    25
Lucy van Pelt | 50|    27|    65
Linus van Pelt| 50|    24|    75
(4 rows)

create view dogs as select * from peanuts where name = 'Snoopy';
CREATE
select * from dogs;
name  |age|height|weight
------+---+------+------
Snoopy| 21|    18|    25
(1 row)

update dogs set age = 145;
UPDATE 0
select * from dogs;
name  |age|height|weight
------+---+------+------
Snoopy| 21|    18|    25
(1 row)

EOF
$