In order to add an attribute to each
class in an entire inheritance hierarchy, use the classname of the superclass
and append a `*'. (By default, the attribute will not be added to any of
the subclasses.) This should always be done when adding an attribute to
a superclass. If it is not, queries on the inheritance hierarchy such
as select * from super* s
will not work because the subclasses will be
missing an attribute found in the superclass.
For efficiency reasons, default values for added attributes are not placed in existing instances of a class. That is, existing instances will have NULL values in the new attributes. If non-NULL values are desired, a subsequent update(l) query should be run.
You must own the class in order to change its schema.