alter column type (from timestamp to date) violates not null

Hi!

When change a column type from timestamp to date, the 'infinity' and '-
infinity' values will be NULL. Even if the column has a not null
constraint.
Sorry, if it is a duplicated bug report.

Regards,
psmith

Here is the test procedure:

proba2=# create table a(t timestamp not null);
CREATE TABLE
proba2=# insert into a values ('infinity');
INSERT 0 1
proba2=# SELECT * from a;
t
----------
infinity
(1 sor)

proba2=# alter table a alter t type date;
ALTER TABLE
proba2=# SELECT *, t is null as is_null from a;
t | is_null
---+---------
| t
(1 sor)

proba2=# \d a
Tábla "public.a"
Oszlop | Típus | Módosító
--------+-------+----------
t | date | not null

proba2=# select version();
version
--------------------------------------------------------------------------------------------------------------
PostgreSQL 8.1.0 on i486-pc-linux-gnu, compiled by GCC cc (GCC) 4.0.3
20051023 (prerelease) (Debian 4.0.2-3)
(1 sor)

proba2=# select 'infinity'::timestamp::date is null;
?column?
----------
t
(1 sor)