Re: lack of consequence with domains and types

gj=# create domain dfoo as varchar(20) default 'bollocks' not null;
CREATE DOMAIN
Time: 1680,908 ms

gj=# create table foo( a bigserial not null, b int default
(random()*100)::int not null );
NOTICE: CREATE TABLE will create implicit sequence "foo_a_seq" for
serial column "foo.a"
CREATE TABLE
Time: 899,848 ms

gj=# insert into foo(b) select generate_series(1, 10);
INSERT 0 10
Time: 138,247 ms

gj=# alter table foo add column c dfoo not null;
ALTER TABLE
Time: 351,059 ms

gj=# select * from foo order by random() limit 1;
a | b | c
---+---+----------
3 | 3 | bollocks
(1 row)

Time: 114,236 ms

I _Do_ understand domains very well. Thing is, why the same thing
won't happen if I include that domain in type!!!