如何解决将两个集合与猫鼬的聚合功能NodeJS相结合
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'
}
}
]
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。