def is_nullable(self, field):
        # We need to use DEFAULT_DB_ALIAS here, as QuerySet does not have
        # (nor should it have) knowledge of which connection is going to be
        # used. The proper fix would be to defer all decisions where
        # is_nullable() is needed to the compiler stage, but that is not easy
        # to do currently.
        if ((connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls)
            and field.empty_strings_allowed):
            return True
        else:
            return field.null
A helper to check if the given field should be treated as nullable.
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/db/models/sql/query.py/Query.is_nullable