将两个集合与猫鼬的聚合功能NodeJS相结合

问题描述

模型文件：models/artistStatistic.js

var artistSchema = new Schema({
        name: { type: String,},{
        timestamps: true 
});

模型文件：models/artist.js

var artistStatisticSchema = new Schema({
        _artistId: { type: Schema.Types.ObjectId,monthlyListeners: { type: Number,{
        timestamps: true 
});

控制器文件：controllers/artistController.js

var keystone = require('keystone');
const Artist = require('../models/artist');

exports.view = function (req,res) {
    var view = new keystone.View(req,res);
    var locals = res.locals;
    // locals.section is used to set the currently selected
    // item in the header navigation.
    locals.section = 'homepage';
    getAllArtists(function (artistData) {
        view.render('homepage',{ artists: artistData,});
    });
}

getAllArtists = function (artistCallback) {
    console.log("getAllArtists before");
    Artist.aggregate([{
            '$lookup': {
                'from': 'artist_statistics','as': 'statistics','let': { 'id': '$_id' },'pipeline': [{
                    '$match': {
                        '$expr': { '$eq': [ '$$id','$_artistId' ] }
                    }
                },{
                    '$sort': {
                        'createAt': -1
                    }
                },{
                    '$limit': 1
                }]
            }
        },{
            '$unwind': {
                'path': '$statistics'
            }
        }]).cursor({}).exec(function (err,artists) {
        if (err) return console.log(err);

        console.log("getAllArtists exec: ");
        console.log(artists);
        return artistCallback(artists ?? [{name: "Error!!!",statistic: { monthlyListeners: "Error!!!" }}]);
    });
    console.log("getAllArtists after");
}

当没有.cursor（{}）参数时，将出现以下错误。然后，当我添加.cursor（{}）参数时，尽管我发送了请求，但它不会加载页面，也不会运行模型回调函数。

.cursor（{}）参数之前

getAllArtists before
getAllArtists after
Error [MongoError]: The 'cursor' option is required,except for aggregate with the explain argument
    at Function.MongoError.create (/Users/cemil.colak/WebServer/program/statistic/node_modules/mongodb-core/lib/error.js:31:11)
    at /Users/cemil.colak/WebServer/program/statistic/node_modules/mongodb-core/lib/connection/pool.js:485:72
    at authenticateStragglers (/Users/cemil.colak/WebServer/program/statistic/node_modules/mongodb-core/lib/connection/pool.js:431:16)
    at Connection.messageHandler (/Users/cemil.colak/WebServer/program/statistic/node_modules/mongodb-core/lib/connection/pool.js:465:5)
    at Socket.<anonymous> (/Users/cemil.colak/WebServer/program/statistic/node_modules/mongodb-core/lib/connection/connection.js:319:22)
    at Socket.emit (events.js:315:20)
    at addChunk (_stream_readable.js:302:12)
    at readableAddChunk (_stream_readable.js:278:9)
    at Socket.Readable.push (_stream_readable.js:217:10)
    at TCP.onStreamRead (internal/stream_base_commons.js:186:23) {
  ok: 0,errmsg: "The 'cursor' option is required,except for aggregate with the explain argument",code: 9,codeName: 'FailedToParse'
}

.cursor（{}）参数之后

GET /example - - ms
getAllArtists before
getAllArtists after

我想做什么；编写查询，以使 artist_statistic 集合中的数据在从 artist 集合中提取数据时获得每个艺术家的最后一个值。

使用Node JS编写查询时，无法使用MongoDB Compass进行查询

使用 MongoDB Compass

将管道导出为语言

[
  {
    '$lookup': {
      'from': 'artist_statistics','let': {
        'id': '$_id'
      },'pipeline': [
        {
          '$match': {
            '$expr': {
              '$eq': [
                '$$id','$_artistId'
              ]
            }
          }
        },{
          '$sort': {
            'createAt': -1
          }
        },{
          '$limit': 1
        }
      ]
    }
  },{
    '$unwind': {
      'path': '$statistics'
    }
  }
]

解决方法

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