Question

我正在尝试使用Mongoose的Model.populate（）将用户ID转换为用户，在通过聚合和展开获取的文档的子结构中。我猜测我的架构有问题或者可能解开是打破了与子架构的连接。

问题是：当存在有效引用时，不会调用填充回调。如果没有子结构，则调用回调，原始文档不变。

结构：

我有文章，用户可以分别没有或多个ArticleRatings。

我在ArticleRating中使用了两个引用，与文章和评分用户相关。

流程：

该过程实际上是将文章导出为（旧）CSV格式并将结构展平为具有用户特定评级的重复文章行。展开非常适合此操作，并且保留空值可以保留没有评级的文章。

调试：

我已经尝试深入了解Model.populate代码。所有的promises和回调包装器都变得非常复杂，但我可以看到底层的填充调用也没有调用内部回调。我没有使用承诺变种 - 但不是100％肯定我是否应该？（Mongoose docs对回调和承诺之间的用例有点模糊）。

我已经仔细检查了我的架构，尝试将模型显式添加到填充调用中（因为它不需要在架构中）。没有错误或例外，它不会崩溃。

逐步浏览Chrome调试器中的代码就像我期望的那样显示模型：前几篇文章的rating.userId具有有效的ObjectId，但在这种情况下，填充回调根本就没有被叫。接下来的一百篇文章没有＆＃34;等级＆＃34; set，并且可以为所有这些调用可靠地调用回调。

所以我猜测我做错了什么导致Model.populate走上一条没有正确错误的路径？

注意：我知道我可以重写代码以使用聚合$ lookup或其他嵌入结构而不是外部引用，但我是在功能拼图的最后一部分，并希望将其作为 - 是

这是简化的架构：

const ArticleRatingSchema = new Schema({
    articleId: {type: Schema.Types.ObjectId, ref:'Article'},
    userId: {type: Schema.Types.ObjectId, ref:'User'},                          
    rating: String,                                                                                                             
    comment: String,                                                                                                        
});

const ArticleSchema = new Schema({
    title: String,
    rating: ArticleRatingSchema,
});

这是查找

    // Find all articles relating to this project, and their ratings.
    // Unwind does the duplicate per-user, and preserve keeps un-rated articles.
    articleModel.aggregate([
            {$match: {projectId: projectId}},
            {$lookup:{from:'articleratings', localField:'_id', foreignField:'articleId', as:'rating' }},
            {$unwind: {path:'$rating', preserveNullAndEmptyArrays:true}}
        ], (err, models) =>
    {
        if (!err) {

            models.map((article) => {

                articleModel.populate(article, {path:'rating.userId', model:'User'}, (err, article)=> {
                    // Process the article...
                    // this callback only gets called where there is NO rating in the article.
                });

            });
        }

Answer 1

我意识到这是因为我在同步map（）循环中处理集合，并且两种情况必须不同，因为不匹配的populate是同步回调，而匹配的替换稍后回调。

如果我在回调中使用console.log（），我发现在已经格式化和下载CSV之后，最后处理了四个匹配的案例。

所以答案是：填充IS被调用，但异步。

我需要重新设计map（）循环以适应通常的异步模式。

Answer 2

我个人对您认为在聚合管道中使用$lookup然后想要.populate()结果感到困惑。因为要求使用.populate()实质上意味着正在向服务器发出其他查询，以便模拟联接＆＃34;。

因此，$lookup实际上是＆＃34;加入服务器＆＃34;那么你真的应该只使用$lookup。

您可以使用.populate()，我会显示一些代码，以表明可以完成。但这里真的很多余，因为你可以在服务器上完成所有的工作。

所以我最好的＆＃34;近似＆＃34;您似乎拥有的结构是：

<强>制品

{
        "_id" : ObjectId("5962104312246235cdcceb16"),
        "title" : "New News",
        "ratings" : [ ],
        "__v" : 0
}

<强> articleratings

{
        "_id" : ObjectId("5962104312246235cdcceb17"),
        "articleId" : ObjectId("5962104312246235cdcceb16"),
        "userId" : ObjectId("5962104312246235cdcceb13"),
        "rating" : "5",
        "comment" : "Great!",
        "__v" : 0
}
{
        "_id" : ObjectId("5962104312246235cdcceb18"),
        "articleId" : ObjectId("5962104312246235cdcceb16"),
        "userId" : ObjectId("5962104312246235cdcceb14"),
        "rating" : "3",
        "comment" : "Okay I guess ;)",
        "__v" : 0
}
{
        "_id" : ObjectId("5962104312246235cdcceb19"),
        "articleId" : ObjectId("5962104312246235cdcceb16"),
        "userId" : ObjectId("5962104312246235cdcceb15"),
        "rating" : "1",
        "comment" : "Hated it :<",
        "__v" : 0
}

用户

{ "_id" : ObjectId("5962104312246235cdcceb13"), "name" : "Bill", "email" : "bill@example.com", "__v" : 0 } { "_id" : ObjectId("5962104312246235cdcceb14"), "name" : "Fred", "email" : "fred@example.com", "__v" : 0 } { "_id" : ObjectId("5962104312246235cdcceb15"), "name" : "Ted", "email" : "ted@example.com", "__v" : 0 }

然后是汇总声明：

Article.aggregate( [ { "$lookup": { "from": ArticleRating.collection.name, "localField": "_id", "foreignField": "articleId", "as": "ratings" }}, { "$unwind": "$ratings" }, { "$lookup": { "from": User.collection.name, "localField": "ratings.userId", "foreignField": "_id", "as": "ratings.userId", }}, { "$unwind": "$ratings.userId" }, { "$group": { "_id": "$_id", "title": { "$first": "$title" }, "ratings": { "$push": "$ratings" } }} ], (err,articles) => { if (err) callback(err); log(articles); callback(); } )

结果：

{ "_id": "5962126f3ef2fb35efeefd94", "title": "New News", "ratings": [ { "_id": "5962126f3ef2fb35efeefd95", "articleId": "5962126f3ef2fb35efeefd94", "userId": { "_id": "5962126f3ef2fb35efeefd91", "name": "Bill", "email": "bill@example.com", "__v": 0 }, "rating": "5", "comment": "Great!", "__v": 0 }, { "_id": "5962126f3ef2fb35efeefd96", "articleId": "5962126f3ef2fb35efeefd94", "userId": { "_id": "5962126f3ef2fb35efeefd92", "name": "Fred", "email": "fred@example.com", "__v": 0 }, "rating": "3", "comment": "Okay I guess ;)", "__v": 0 }, { "_id": "5962126f3ef2fb35efeefd97", "articleId": "5962126f3ef2fb35efeefd94", "userId": { "_id": "5962126f3ef2fb35efeefd93", "name": "Ted", "email": "ted@example.com", "__v": 0 }, "rating": "1", "comment": "Hated it :<", "__v": 0 } ] }

对于＆＃34;填充＆＃34;没有意义的地方引用＆＃34; articleId＆＃34;关于＆＃34;评级＆＃34;他们自己。但我们确实已经填充了＃34; ＆＃34;评级＆＃34;到文章和＆＃34;用户＆＃34;对于每个评级。

示例清单

使用.populate()（在$lookup之后）和您正在尝试的方式同时显示两种方式，并且只使用普通$lookup。

方法同时使用＆＃34;普通承诺＆＃34;并与async.map交替使用：

const async = require('async'), mongoose = require('mongoose'), Schema = mongoose.Schema; mongoose.Promise = global.Promise; mongoose.set('debug',true); mongoose.connect('mongodb://localhost/publication'); const userSchema = new Schema({ name: String, email: String }); const User = mongoose.model('User', userSchema); const articleRatingSchema = new Schema({ articleId: {type: Schema.Types.ObjectId, ref:'Article'}, userId: {type: Schema.Types.ObjectId, ref:'User'}, rating: String, comment: String, }); const articleSchema = new Schema({ title: String, ratings: [articleRatingSchema] }) const Article = mongoose.model('Article', articleSchema); const ArticleRating = mongoose.model('ArticleRating', articleRatingSchema); function log(data) { console.log(JSON.stringify(data,undefined,2)) } const userData = [ { name: 'Bill', rating: 5, comment: 'Great!' }, { name: 'Fred', rating: 3, comment: 'Okay I guess ;)' }, { name: 'Ted', rating: 1, comment: 'Hated it :<' } ]; async.series( [ // Clean data (callback) => async.each(mongoose.models,(model,callback) => model.remove({},callback),callback), // Insert data (callback) => async.waterfall( [ // User and article (callback) => async.parallel( { "users": (callback) => User.create( ["Bill", "Fred", "Ted"].map( name => ({ name, email: `${name.toLowerCase()}@example.com` }) ), callback ), "article": (callback) => Article.create({ title: "New News" },callback) }, callback ), // Article Ratings (data,callback) => ArticleRating.create( data.users.map( u => ({ articleId: data.article._id, userId: u._id, rating: userData.find( ud => ud.name === u.name ).rating, comment: userData.find( ud => ud.name === u.name ).comment })), callback ) ], callback ), // $lookup and populate async.map (callback) => Article.aggregate( [ { "$lookup": { "from": ArticleRating.collection.name, "localField": "_id", "foreignField": "articleId", "as": "ratings" }} ], (err,articles) => { if (err) callback(err); async.map( articles.map( a => new Article(a) ), (article,callback) => async.map( article.ratings, (rating,callback) => ArticleRating.populate(rating,{ path: 'userId' },callback), (err,ratings) => { if (err) callback(err); article.ratings = ratings callback(null,article) } ), (err,articles) => { if (err) callback(err); log(articles); callback(); } ) } ), // $look and populate Promise (callback) => Article.aggregate( [ { "$lookup": { "from": ArticleRating.collection.name, "localField": "_id", "foreignField": "articleId", "as": "ratings" }} ] ) .then(articles => Promise.all( articles.map( a => new Article(a) ).map(article => new Promise((resolve,reject) => { Promise.all( article.ratings.map( rating => ArticleRating.populate(rating,{ path: 'userId' }) ) ).then(ratings => { article.ratings = ratings; resolve(article); }).catch(reject) }) ) ) ) .then(articles => { log(articles); callback(); }) .catch(err => callback(err)), // Plain $lookup (callback) => Article.aggregate( [ { "$lookup": { "from": ArticleRating.collection.name, "localField": "_id", "foreignField": "articleId", "as": "ratings" }}, { "$unwind": "$ratings" }, { "$lookup": { "from": User.collection.name, "localField": "ratings.userId", "foreignField": "_id", "as": "ratings.userId", }}, { "$unwind": "$ratings.userId" }, { "$group": { "_id": "$_id", "title": { "$first": "$title" }, "ratings": { "$push": "$ratings" } }} ], (err,articles) => { if (err) callback(err); log(articles); callback(); } ) ], (err) => { if (err) throw err; mongoose.disconnect(); } );

完整输出

Mongoose: users.remove({}, {}) Mongoose: articles.remove({}, {}) Mongoose: articleratings.remove({}, {}) Mongoose: users.insert({ name: 'Bill', email: 'bill@example.com', _id: ObjectId("596219ff6f73ed36d868ed40"), __v: 0 }) Mongoose: users.insert({ name: 'Fred', email: 'fred@example.com', _id: ObjectId("596219ff6f73ed36d868ed41"), __v: 0 }) Mongoose: users.insert({ name: 'Ted', email: 'ted@example.com', _id: ObjectId("596219ff6f73ed36d868ed42"), __v: 0 }) Mongoose: articles.insert({ title: 'New News', _id: ObjectId("596219ff6f73ed36d868ed43"), ratings: [], __v: 0 }) Mongoose: articleratings.insert({ articleId: ObjectId("596219ff6f73ed36d868ed43"), userId: ObjectId("596219ff6f73ed36d868ed40"), rating: '5', comment: 'Great!', _id: ObjectId("596219ff6f73ed36d868ed44"), __v: 0 }) Mongoose: articleratings.insert({ articleId: ObjectId("596219ff6f73ed36d868ed43"), userId: ObjectId("596219ff6f73ed36d868ed41"), rating: '3', comment: 'Okay I guess ;)', _id: ObjectId("596219ff6f73ed36d868ed45"), __v: 0 }) Mongoose: articleratings.insert({ articleId: ObjectId("596219ff6f73ed36d868ed43"), userId: ObjectId("596219ff6f73ed36d868ed42"), rating: '1', comment: 'Hated it :<', _id: ObjectId("596219ff6f73ed36d868ed46"), __v: 0 }) Mongoose: articles.aggregate([ { '$lookup': { from: 'articleratings', localField: '_id', foreignField: 'articleId', as: 'ratings' } } ], {}) Mongoose: users.find({ _id: { '$in': [ ObjectId("596219ff6f73ed36d868ed40") ] } }, { fields: {} }) Mongoose: users.find({ _id: { '$in': [ ObjectId("596219ff6f73ed36d868ed41") ] } }, { fields: {} }) Mongoose: users.find({ _id: { '$in': [ ObjectId("596219ff6f73ed36d868ed42") ] } }, { fields: {} }) [ { "_id": "596219ff6f73ed36d868ed43", "title": "New News", "__v": 0, "ratings": [ { "_id": "596219ff6f73ed36d868ed44", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed40", "name": "Bill", "email": "bill@example.com", "__v": 0 }, "rating": "5", "comment": "Great!", "__v": 0 }, { "_id": "596219ff6f73ed36d868ed45", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed41", "name": "Fred", "email": "fred@example.com", "__v": 0 }, "rating": "3", "comment": "Okay I guess ;)", "__v": 0 }, { "_id": "596219ff6f73ed36d868ed46", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed42", "name": "Ted", "email": "ted@example.com", "__v": 0 }, "rating": "1", "comment": "Hated it :<", "__v": 0 } ] } ] Mongoose: articles.aggregate([ { '$lookup': { from: 'articleratings', localField: '_id', foreignField: 'articleId', as: 'ratings' } } ], {}) Mongoose: users.find({ _id: { '$in': [ ObjectId("596219ff6f73ed36d868ed40") ] } }, { fields: {} }) Mongoose: users.find({ _id: { '$in': [ ObjectId("596219ff6f73ed36d868ed41") ] } }, { fields: {} }) Mongoose: users.find({ _id: { '$in': [ ObjectId("596219ff6f73ed36d868ed42") ] } }, { fields: {} }) [ { "_id": "596219ff6f73ed36d868ed43", "title": "New News", "__v": 0, "ratings": [ { "_id": "596219ff6f73ed36d868ed44", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed40", "name": "Bill", "email": "bill@example.com", "__v": 0 }, "rating": "5", "comment": "Great!", "__v": 0 }, { "_id": "596219ff6f73ed36d868ed45", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed41", "name": "Fred", "email": "fred@example.com", "__v": 0 }, "rating": "3", "comment": "Okay I guess ;)", "__v": 0 }, { "_id": "596219ff6f73ed36d868ed46", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed42", "name": "Ted", "email": "ted@example.com", "__v": 0 }, "rating": "1", "comment": "Hated it :<", "__v": 0 } ] } ] Mongoose: articles.aggregate([ { '$lookup': { from: 'articleratings', localField: '_id', foreignField: 'articleId', as: 'ratings' } }, { '$unwind': '$ratings' }, { '$lookup': { from: 'users', localField: 'ratings.userId', foreignField: '_id', as: 'ratings.userId' } }, { '$unwind': '$ratings.userId' }, { '$group': { _id: '$_id', title: { '$first': '$title' }, ratings: { '$push': '$ratings' } } } ], {}) [ { "_id": "596219ff6f73ed36d868ed43", "title": "New News", "ratings": [ { "_id": "596219ff6f73ed36d868ed44", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed40", "name": "Bill", "email": "bill@example.com", "__v": 0 }, "rating": "5", "comment": "Great!", "__v": 0 }, { "_id": "596219ff6f73ed36d868ed45", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed41", "name": "Fred", "email": "fred@example.com", "__v": 0 }, "rating": "3", "comment": "Okay I guess ;)", "__v": 0 }, { "_id": "596219ff6f73ed36d868ed46", "articleId": "596219ff6f73ed36d868ed43", "userId": { "_id": "596219ff6f73ed36d868ed42", "name": "Ted", "email": "ted@example.com", "__v": 0 }, "rating": "1", "comment": "Hated it :<", "__v": 0 } ] } ]

当引用

2 个答案:

示例清单