How can I rename a field in the model code, e.g. `FooModel`, so that the changes propagate correctly to the database schema?

I would like to rename e.g. `spam` to `beans` in the `FooModel._columns`. But how can I ensure that the same column rename occurs in the database when I update the OpenERP server code?

I can just rename the field in the Python code for the model, of course. But how will Odoo know which field was renamed to what? What if I rename several fields at once? What if I rename one field, delete another, and create another? How can I signal to Odoo which new fields are renames?