def deferred_to_columns(self):
        columns = {}
        self.query.deferred_to_data(columns, self.query.deferred_to_columns_cb)
        return columns
Converts the self.deferred_loading data structure to mapping of table
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/db/models/sql/compiler.py/SQLCompiler.deferred_to_columns