如何使用Node.JS和Mongoose將數據從MongoDB獲取到簡單數組？

Question

假設這是我的MongoDB模式：

    var shopSchema = new mongoose.Schema({
        nameShop: String,
        products: [
            {
                type: mongoose.Schema.Types.ObjectId,
                ref: 'Product'
            }]
    });

    var productSchema = new mongoose.Schema({
        nameProduct: String,
        fruits: [
            {
                type: mongoose.Schema.Types.ObjectId,
                ref: 'Fruit'
            }
        ]
    });

    var fruitSchema = new mongoose.Schema({
        nameFruit: String,
        price: Number
    });

module.exports = {
    Shop: mongoose.model('Shop', shopSchema),
    Product: mongoose.model('Product', productSchema),
    Fruit: mongoose.model('Fruit', fruitSchema)
}

我知道我可以通過這種方式獲取數據，但是該代碼的結果是一個“丑陋”的數組

var Schema = require('../model/schema');
    Schema.Shop.find({}).populate({
        path: 'products',
        model: 'Product',
        populate: {
            path: 'fruits',
            model: 'Fruit'
        }
    }).exec(callback);

是否有可能以這種方式從該架構中獲取數據，從而獲得良好的數組？ 例如：

var MyArray = [
                  { nameShop: "Tesco", nameProduct: "New", nameFruit: "Apple", price: 10 },
                  { nameShop: "Tesco", nameProduct: "New", nameFruit: "Pinapple", price: 4 },
                  { nameShop: "Eko", nameProduct: "Old", nameFruit: "Kiwi", price: 8 },
                  { nameShop: "Makro", nameProduct: "Fresh", nameFruit: "Pear", price: 7 },
                  { nameShop: "Carefour", nameProduct: "New", nameFruit: "Orange", price: 6 }
              ];

Answer 1

您可以使用聚合框架路由，該路由具有通過$unwind運算符使陣列變平的功能。 這將為應用展開的列表數據字段的每個元素生成一條新記錄。 它基本上使數據變平。

拼合數據后，您將需要$lookup運算符在products字段中將“ join”到products集合。 對嵌套水果模式重復該過程。

讓我們看一個示例（未經測試）以更好地理解這一點

var Schema = require('../model/schema');
Schema.Shop.aggregate([
    { "$unwind": "$products" },
    {
        "$lookup": {
            "from": "products",
            "localField": "products",
            "foreignField": "_id",
            "as": "product"
        }
    },
    { "$unwind": "$product" },
    { "$unwind": "$product.fruits" },
    {
        "$lookup": {
            "from": "fruits",
            "localField": "product.fruits",
            "foreignField": "_id",
            "as": "fruits"
        }
    },  
    {
        "$project": {
            "nameShop": 1,
            "nameProduct": "$product.nameProduct",
            "nameFruit": "$fruits.nameFruit",
            "price": "$fruits.price",
        }
    }
]).exec(function (err, result){
    if (err) throw err;
    console.log(result);
})

免責聲明 ：上面是未經測試的代碼，它僅通過以下幾個假設為指導：您正在使用支持$lookup運算符的最新MongoDB和mongoose版本在測試環境中運行代碼，並且可以執行相同的聚合在mongo shell中查詢。