Mongoose - 查询以从多个集合中获取数据

Question

我想在 nodejs 应用程序中获取猫鼬的查询，如下所述。
user.js、comment.js 和 post.js 是我使用的模型文件。

user.js

var mongoose = require('mongoose');  
var Schema = mongoose.Schema;  
var ObjectId = Schema.ObjectId;  

var userSchema = new Schema({  
        nick_name:{type:String},  
        email: {  
            type: String,  
            trim: true,  
            required: '{PATH} is required!',
            index: true,
        },     
    },{ collection: 'user'});

var User = mongoose.model('User', userSchema);
module.exports = User;  

comment.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;

var commentSchema = new Schema({  
         comment: type:String,  
         user_id:{
            type:Schema.Types.ObjectId, ref:'User'
         },  
         is_active :1
},{ collection: 'comment'});

post.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;

var postSchema = new Schema({
        post: type:String,
        user_id:{
           type:Schema.Types.ObjectId, ref:'User'
        },
        is_active :1
},{ collection: 'post'});

想出来如下：

{
 "nick_name":"prakash",
 "email":"prakash@mailinator.com",
 "comments":[
      {
      "comment":"this is a comment text1",
      "is_active":1,
      },
      {
      "comment":"this is a comment text2",
      "is_active":1,
      }
 ],
 "posts":[
      {
      "post":"this is a post text1",
      "is_active":1,
      },
      {
      "post":"this is a post text2",
      "is_active":1,
      },
      {
      "post":"this is a post text3",
      "is_active":1,
      },
 ]
}

依赖项

"express"  => "version": "4.7.4",
"mongoose" => "version": "4.4.5",
"mongodb"  => "version": "2.4.9",
"OS"  => "ubuntu 14.04 lts 32bit",

如果无法查询，请建议我一个合适的猫鼬插件。 但我不想对 user.js 文件及其 userSchema 对象进行任何更改。

Answer 1

当然有可能，你只需要使用填充，让我告诉你如何：

导入您的架构

var mongoose = require('mongoose');
var userSch = require('userSchema');
var postSch = require('postSchema');
var commSch = require('commentSchema');

初始化所有必要的变量

var userModel = mongoose.model('User', userSch);
var postModel = mongoose.model('Post', postSch);
var commModel = mongoose.model('Comment', commSch);

现在，进行查询

postModel.find({}).populate('User')
    .exec(function (error, result) {
        return callback(null, null);
    });

commModel.find({}).populate('User')
    .exec(function (error, result) {
        return callback(null, null);
    }); 

通过这种方式，您可以在您的评论和帖子中获取用户，要在您的用户中获取帖子和 cmets，您必须执行 3 个查询，一个用于用户，一个用于 cmets，一个用于帖子，并混合在一起

Answer 2

Mongo 中没有“连接”。但是您要做的是更改您的用户模式以将评论和发布文档的 ObjectId 存储在您的用户数组中。然后在需要用户数据时使用“填充”。

const userSchema = new Schema({  
    nick_name:{type:String},  
    email: {  
        type: String,  
        trim: true,  
        required: '{PATH} is required!',
        index: true,
    },
    comments: [{ type: Schema.Types.ObjectId, ref:'Comment' }],
    posts: [{ type: Schema.Types.ObjectId, ref:'Post' }]
}, {timestamps: true});

mongoose.model('User', userSchema);

您的查询将如下所示：

User.find()
    .populate('comments posts') // multiple path names in one requires mongoose >= 3.6
    .exec(function(err, usersDocuments) {
        // handle err
        // usersDocuments formatted as desired
    });

Mongoose populate docs

Answer 3

有可能。您应该使用聚合。 它应该工作。 初始化变量

    var mongoose = require('mongoose');
    var userCollection = require('./user');//import user model file
    var resources = {
    nick_name: "$nick_name",
    email: "$email"};

    userCollection.aggregate([{
            $group: resources
        }, {
            $lookup: {
                from: "Comments", // collection to join
                localField: "_id",//field from the input documents
                foreignField: "user_id",//field from the documents of the "from" collection
                as: "comments"// output array field
            }
        }, {
            $lookup: {
                from: "Post", // from collection name
                localField: "_id",
                foreignField: "user_id",
                as: "posts"
            }
        }],function (error, data) {
         return res.json(data);
     //handle error case also
});

Answer 4

您可以考虑在模型用户中使用 cmets 和诸如 docs (https://mongoosejs.com/docs/populate.html#populate-virtuals) 之类的帖子的虚拟填充。并像这样使用： User.find({filter}).populates('virtualComments').populate('virtualPosts')