@classmethod
def _init_default(cls, dialect, connection, dbapi_connection):
    """Initialize execution context for a ColumnDefault construct."""
    self = cls.__new__(cls)
    self.root_connection = connection
    self._dbapi_connection = dbapi_connection
    self.dialect = connection.dialect
    self.execution_options = connection._execution_options
    self.cursor = self.create_cursor()
    return self
