Cannot alter a column used in a view, need to drop the view first.

issue_with_postgres_views.sql

CREATE TABLE foo(
  some_id SERIAL PRIMARY KEY,
  another INT,
  stuff   VARCHAR(20)
);

CREATE OR REPLACE FUNCTION insert_crap_into_foo() RETURNS INTERVAL AS
$$
DECLARE
  counter INT := 0;
  start TIMESTAMP := timeOfDay();
  stop  TIMESTAMP;
BEGIN
  LOOP
    counter := counter + 1;
    INSERT INTO foo(another) VALUES(counter);
    EXIT WHEN counter > 2000000;
  END LOOP;
  stop := timeOfDay();
  RETURN stop - start;
END
$$
language plpgsql;

SELECT insert_crap_into_foo();

SELECT now() AS creating_view;
CREATE OR REPLACE VIEW bar AS SELECT * FROM foo;
SELECT now() AS view_created;

ALTER TABLE foo ADD more_stuff NUMERIC(10,2);
ALTER TABLE foo DROP more_stuff;
ALTER TABLE foo ALTER COLUMN stuff TYPE VARCHAR(50);
ALTER TABLE foo ALTER COLUMN another TYPE BIGINT; --This gives an error:
--ERROR:  cannot alter type of a column used by a view or rule
--DETAIL:  rule _RETURN on view bar depends on column "another"
--Need to drop the view in the meantime
DROP VIEW bar;
SELECT now() AS dropped;
ALTER TABLE foo ALTER COLUMN another TYPE BIGINT; --now it works
-- but, in a table with millions of rows, this alteration can take some time
-- the view won't exist until the change is done
SELECT now() AS created_again;
CREATE VIEW bar AS SELECT * FROM foo;
SELECT now() AS done;

DROP FUNCTION insert_crap_into_foo();
DROP VIEW bar;
DROP TABLE foo;