如何有效地获取 MongoDB/mongoose 帖子的评论？

Question

我有以下 Post 和 Collection 个文件：

// posts
{
    "_id" : ObjectId("56978d8cdbc511a81e7e2ea8"),
    "body" : "Post body 1",
    "created_at" : 1452772748737
},
{
    "_id" : ObjectId("56978d3cdbc655b81e7e2e10"),
    "body" : "Post body 2",
    "created_at" : 1452772759731
}

// comments
{
    "_post" : ObjectId("56978d8cdbc511a81e7e2ea8"),
    "body" : "Comment 1"
},
{
    "_post" : ObjectId("56978d3cdbc655b81e7e2e10"),
    "body" : "Comment 2"
}

我需要查询所有 post 的所有评论，结果如下：

{
    "_id" : ObjectId("56978d8cdbc511a81e7e2ea8"),
    "body" : "Post body 1",
    "created_at" : 1452772748737,
    "comments": [{
        "_post" : ObjectId("56978d8cdbc511a81e7e2ea8"),
        "body" : "Comment 1"
    }]
},
{
    "_id" : ObjectId("56978d3cdbc655b81e7e2e10"),
    "body" : "Post body 2",
    "created_at" : 1452772759731,
    "comments": [{
        "_post" : ObjectId("56978d3cdbc655b81e7e2e10"),
        "body" : "Comment 2"
    }]
}

我的 post 和 collections 架构如下所示：

// post 
var PostSchema = mongoose.Schema({

},{
    strict: "throw",
    collection: "posts"
});

PostSchema.add({
    created_at: {
        type: Number,
        'default': Date.now
    }
});

PostSchema.add({
    title: {
        type: String
    }
});

PostSchema.add({
    body: {
        type: String
    }
});

// comment
var CommentSchema = mongoose.Schema({

},{
    strict: "throw",
    collection: "comments"
});

CommentSchema.add({
    _post: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Post'
    }
});

CommentSchema.add({
    body: {
        type: String
    }
});

获得上述结果的有效方法是什么？

Answer 1

尝试通过mongoose populate and aggregate完成。示例代码如下。

var Post = mongoose.model('Post', PostSchema);
var Comment = mongoose.model('Comment', CommentSchema);

Comment.aggregate([
    {$group: {_id: '$_post', comments: {$push: '$body'}}}
    // ...
    ], function(err, result) {
        if (err)
           // error handling
        Post.populate(result, {path: "_id"}, function(err, ret) {
            if(err)
                console.log(err);
            else
                console.log(ret);
        });
});

如何有效地获取 MongoDB/mongoose 帖子的评论？

How to effectively fetch comments for posts with MongoDB/mongoose?

node.js

mongodb

express

mongoose

async.js