MongoDB嵌套集

在MongoDB中存储嵌套集(如注释树)的最佳实践是什么？

我的意思是,每个评论都可以有父评论和孩子评论(答案).

像这样存储它们:

{
   title: "Hello",
   body: "Please comment me!",
   comments: [
        {
            author: "Peter",
            text: "Hi there",
            answers: [
                  {
                      author: "Peter",
                      text: "Hi there",
                      answers: [
                                 { author: "Ivan", text: "Hi there" },
                                 { author: "Nicholas", text: "Hi there" }
                      ]
                  },
                  { author: "Ivan", text: "Hi there" },
                  { author: "Nicholas", text: "Hi there" },
            ]
        },
        { author: "Ivan", text: "Hi there" },
        { author: "Nicholas", text: "Hi there" },
   ]
}

并不酷,因为我们不能,例如,在没有map/reduce的情况下,请求"所有被Peter评论的帖子".