cursor.py 文件源码

def explain(self) -> MutableMapping:
        """Returns an explain plan record for this cursor.

        .. mongodoc:: explain
        """

        c = self.clone()
        c.__explain = True

        # always use a hard limit for explains
        if c.__limit:
            c.__limit = -abs(self.__limit)

        async for expl in c:
            return expl

        return None