Lock a viewe

Hi,
I was wondering if there is a clean view to lock the usage of a view.

Basically during a schema migration, with applications still running a
typical
schema change is:

BEGIN;
ALTER TABLE x ADD COLUMN (a INTEGER);
CREATE OR REPLACE VIEW v_x
AS
SELECT a,b FROM x;
COMMIT;

now the issue is that if an application performs a:

SELECT * from v_x;

between the ALTER and the view redefinition then a deadlock happens.

I'm preventing this issue doing a:

ALTER VIEW v_x ALTER COLUMN b DROP DEFAULT;
(anyway there was no default on the view)
before the ALTER TABLE, that's basically reorders the locks sequence
avoiding the dead lock.

Is there a clean way to achieve it without the "hack"?

GM