Mongodb 用其他集合中的文档替换嵌套文档数组中的值

如果你真想这么做，一个 Select 是:

db.Shops.aggregate([
  {$lookup: {
      from: "Products",
      localField: "countries.cities.districts.products",
      foreignField: "uid",
      as: "res"
  }},
  {$project: {
      countriesA: {
        $map: {
          input: "$countries",
          as: "country",
          in: {
            $mergeObjects: [
              "$$country",
              {
                cities: {
                  $map: {
                    input: "$$country.cities",
                    as: "city",
                    in: {
                      $mergeObjects: [
                        "$$city",
                        {
                          districts: {
                            $map: {
                              input: "$$city.districts",
                              as: "district",
                              in: {
                                $mergeObjects: [
                                  "$$district",
                                  {
                                    products: {
                                      $map: {
                                        input: "$$district.products",
                                        in: {
                                          $arrayElemAt: [
                                            "$res",
                                            {
                                              $indexOfArray: [
                                                "$res.uid",
                                                "$$this"
                                              ]
                                            }
                                          ]
                                        }
                                      }
                                    }
                                  }
                                ]
                              }
                            }
                          }
                        }
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
])

看看它在mongoDB playground号公路上是如何工作的

But:个

我会考虑将 struct 更改 for each store 、国家、城市和地区的文档，其中只有产品是一个array.就像这样:

{
    "_id": ObjectId("5a934e000102030405000000"),
    "name": "Shop A",
    "countryName": "Germany",
    "cityName": "Berlin",
    "districtName": "First District",
    "products": [1, 2, 3]
}

其中可以使用查询:

db.Shops.aggregate([
  {$lookup: {
      from: "Products",
      localField: "products",
      foreignField: "uid",
      as: "res"
  }},
  {$set: {
      products: {$map: {
          input: "$products",
          in: {$arrayElemAt: ["$res", {$indexOfArray: ["$res.uid", "$$this"]}]}
      }},
      res: "$$REMOVE"
  }}
])