'Execute a schema.ColumnDefault object.'

def _execute_default(self, default, multiparams, params):

    if (self._has_events or self.engine._has_events):
        for fn in self.dispatch.before_execute:
            (default, multiparams, params) = fn(self, default, multiparams, params)
    try:
        try:
            conn = self.__connection
        except AttributeError:
            conn = self._revalidate_connection()
        dialect = self.dialect
        ctx = dialect.execution_ctx_cls._init_default(dialect, self, conn)
    except Exception as e:
        self._handle_dbapi_exception(e, None, None, None, None)
    ret = ctx._exec_default(default, None)
    if self.should_close_with_result:
        self.close()
    if (self._has_events or self.engine._has_events):
        self.dispatch.after_execute(self, default, multiparams, params, ret)
    return ret
