如何在MongoDB中使用Mongoose从两个集合关系中找到计数

Question

我想显示特定用户(_id: 876896)的列表文件，其点击计数如下:

Sr. No. | File Name | Click Count

下面是我使用的示例模式:

var clicks = mongoose.Schema({
 file_id   : String,
 IP    : String
});
var files = mongoose.Schema({
 filename   : String,
 owner    : {type:mongoose.Schema.ObjectId, ref:'users'},
});

如何有效地做到这一点

Answer 1

您可以分两步完成，首先获取指向您想要的用户的所有文件。然后，获取与所读文件相关的所有点击。mongodb中没有INNER_JOIN

:

     files.find({
           owner: {
              $in: usersIdsArray // [_id, _id...] ids of all users
           },
        }).then((ret = []) => {
            // Here ret is array of files
            if (!ret.length) // There is no files matching the user
            return clicks.find({
                 file_id: {
                     $in: Array.from(ret, x => x._id.toString()),
                     // build an array like [_id, _id, _id...]
                 },
            });
        }).then((ret = []) => {
            // Here you have all clicks items
        });

---

我还建议使用嵌入式模式而不是多个集合:

var clicks = mongoose.Schema({
 file_id: String,
 IP: String
});
var files = mongoose.Schema({
 filename: String,
 owner: {type:mongoose.Schema.ObjectId, ref:'users'},
});

变成:

var files = mongoose.Schema({
   filename: String,
   owner: {type:mongoose.Schema.ObjectId, ref:'users'},
   clicks: [String], // With String your IP
});

MongoDB在大数据方面很好，但在关系方面就不那么好了。