Блог

Как бы я ни старался, коллекция книг продолжает выводить повторяющиеся значения для одной коллекции в базе данных в зависимости от количества ее подкатегорий. Если общая длина подкатегорий равна трем для конкретной книги, книги выводят три массива для одной коллекции. Ниже длина подкатегорий равна трем, и в книгах выводится три дубликата одного значения. Я бы хотел, чтобы коллекция книг отображала только одно значение, как оно есть в базе данных, а не дубликаты одного значения из базы данных

Пожалуйста, помогите мне в этом

Вывод Кодов

 books: Array(3)
0: {_id: '6158beb4c6ac564594e409e1', user: {…}, title: 'Amazon announces Astro the home robot', content: '<p>The company said it can be remote-controlled wh… hundreds of thousands of players.</p><p><br></p>', description: 'Amazon is launching Astro, its first household robot, powered by its Alexa smart home technology', …}
1: {_id: '6158beb4c6ac564594e409e1', user: {…}, title: 'Amazon announces Astro the home robot', content: '<p>The company said it can be remote-controlled wh… hundreds of thousands of players.</p><p><br></p>', description: 'Amazon is launching Astro, its first household robot, powered by its Alexa smart home technology', …}
2: {_id: '6158beb4c6ac564594e409e1', user: {…}, title: 'Amazon announces Astro the home robot', content: '<p>The company said it can be remote-controlled wh… hundreds of thousands of players.</p><p><br></p>', description: 'Amazon is launching Astro, its first household robot, powered by its Alexa smart home technology', …}
count: 3
name: "technology"

subCategories: Array(3)
0: {_id: '615782c9ef37913ce4b240e1', subCategories: Array(0), user: {…}, name: 'Django', category_root: '615746f2963a3032bc6812e0', …}
1: {_id: '61577ebcef37913ce4b240ba', subCategories: Array(0), user: {…}, name: 'Java', category_root: '615746f2963a3032bc6812e0', …}
2: {_id: '6157550cef37913ce4b24085', subCategorifes: Array(0), user: {…}, name: 'Python', category_root: '615746f2963a3032bc6812e0', …}
 

Модель

 user: { type: mongoose.Types.ObjectId, ref: 'user' },
    title: {
        type: String,
        require: true,
        trim: true,
        minLength: 10,
        maxLength: 50
    },
    content: {
        type: String,
        require: true,
        minLength: 2000
    },
    description: {
        type: String,
        require: true,
        trim: true,
        minLength: 50,
        maxLength: 200
    },
    thumbnail: {
        type: String,
        require: true
    },
    category: { type: mongoose.Types.ObjectId, ref: 'category' },
    subCategories: { type: mongoose.Types.ObjectId, ref: 'category' }
 

Ниже приведен используемый агрегатный метод

 await books.aggregate([
            //User
            {
                $match: { 
                    subCategories: { $exists: false },
                    category: { $exists: true },
                    category_root: { $exists: false },
                    sub_user: { $exists: false }
                }
            }, 
            {
                $lookup:{
                    from: "users",
                    let: { user_id: "$user" },
                    pipeline: [
                        { $match: { $expr: { $eq: ["$_id", "$user_id"] } } },
                        { $project: { password: 0 } }
                    ],
                    as: "user"
                }
            },
            // array -> object
            { $unwind: { path: "$user", preserveNullAndEmptyArrays: true } },
            // Category
            {
                $lookup: {
                     from: "categories",
                     "localField": "category",
                     "foreignField": "_id",
                     "as": "category"
                }
            },
            // array -> object
            { $unwind: { path: "$category", preserveNullAndEmptyArrays: true } }, 
            // SubCategories Category 
            {
                $lookup: {
                    from: "categories",
                    "let": { sub_id: "$category.subCategories" },
                    "pipeline": [
                        { $match: { $expr: { $in: ["$_id", {$ifNull:["$sub_id",[]]}] } } },
                        {
                            $lookup: { 
                                "from" : "users",
                                "let": { user_id: "$user" },
                                "pipeline": [
                                    { $match: { $expr: { $eq: ["$_id", "$user_id"] } } },
                                    { $project: { name: 1, avatar: 1 } }
                                ],
                                "as": "user" 
                             }
                        },
                        {  $unwind: "$user" },
                        {
                            $lookup: { 
                                "from" : "users",
                                "let": { user_id: "$sub_user" },
                                "pipeline": [
                                    { $match: { $expr: { $eq: ["$_id", "$user_id"] } } },
                                    { $project: { name: 1, avatar: 1 } }
                                ],
                                "as": "sub_user" 
                             }
                        },
                        {  $unwind: "$sub_user" }
                    ],
                    "as": "subCategories" 
                }
            },
            {  $unwind: { path: "$subCategories", preserveNullAndEmptyArrays: true }},
            // Sorting
            { $sort: { "createdAt": -1 } },
            //Group by category
            {
                $group: {
                    _id: "$category._id",
                    name: { $first: "$category.name" },
                    books: { $push: "$ROOT" },
                    subCategories: { $addToSet: "$subCategories" },
                    count: { $sum: 1 }
                }
            },
            //Pagination for books
            {
                $project: {
                    books: {
                        $slice: ['$books', 0, 4]
                    },
                    subCategories: 1,
                    count: 1,
                    name: 1
                }
            }
        ])