如何在 NodeJS 的 MongoDB 驱动程序中加入嵌套数组？

Question

我正在使用 MongoDB shell 版本 v3.6.3。我有两个集合 1. 用户 2. 业务我在下面给出了示例数据。

user
********
_id : 1
username : "joyjeba2"
mobile_number : 9840347197,
profile_url :"http://localhost:3001/user/1599214209351_dp1.jpg"
saved_products :[1,2]

Business
*****
_id:1
name : "businessname1"
location :"location",
contact_number:123456,
Products : [
{   "name": "product",
    "tags": [
        "shoes",
        "slippers"
    ],
    "description": "its a simple description",
    "lower_price": 20,
    "higher_price": 30,
    "min_order": 20,
    "units": "count",
    "media_urls": [
        "http://localhost:3001/product/1586703106075_DP1.jpg"
    ],
    "_id": 1
}
{   "name": "product",
    "tags": [
        "shoes",
        "slippers"
    ],
    "description": "its a simple description",
    "lower_price": 20,
    "higher_price": 30,
    "min_order": 20,
    "units": "count",
    "media_urls": [
        "http://localhost:3001/product/1586703106075_DP1.jpg"
    ],
    "_id": 2
},  
]

现在我想从用户集合中的 saved_products 连接到业务集合中的产品。

预期结果是：

_id : 1
username : "joyjeba2"
mobile_number : 9840347197,
profile_url :"http://localhost:3001/user/1599214209351_dp1.jpg"
saved_product : [
{   "name": "product",
    "tags": [
        "shoes",
        "slippers"
    ],
    "description": "its a simple description",
    "lower_price": 20,
    "higher_price": 30,
    "min_order": 20,
    "units": "count",
    "media_urls": [
        "http://localhost:3001/product/1586703106075_DP1.jpg"
    ],
    "_id": 1
    "_business_id":1,   
    "business_name" : "businessname1"
    "location" :"location"
}
{   "name": "product",
    "tags": [
        "shoes",
        "slippers"
    ],
    "description": "its a simple description",
    "lower_price": 20,
    "higher_price": 30,
    "min_order": 20,
    "units": "count",
    "media_urls": [
        "http://localhost:3001/product/1586703106075_DP1.jpg"
    ],
    "_id": 2,
    "_business_id":1,   
    "business_name" : "businessname1"
    "location" :"location"
},  
],

当产品是单独的集合时（在查找和展开的帮助下），我能够做到这一点。但是这里的产品作为嵌套文档位于业务集合中。我怎样才能做到这一点。请帮帮我。

Answer 1

你可以试试，

$lookup 使用管道，在 let

saved_products

$unwind解构Products数组
$match 产品编号
$mergeObjects合并业务字段和产品字段
$replaceRoot 替换根中的合并对象

db.user.aggregate([
  {
    $lookup: {
      from: "business",
      let: { saved_products: "$saved_products" },
      pipeline: [
        { $unwind: "$Products" },
        { $match: { $expr: { $in: ["$Products._id", "$$saved_products"] } } },
        {
          $replaceRoot: {
            newRoot: {
              $mergeObjects: [
                "$Products",
                {
                  _business_id: "$_id",
                  business_name: "$name",
                  location: "$location"
                }
              ]
            }
          }
        }
      ],
      as: "saved_products"
    }
  }
])

Playground

如何在 NodeJS 的 MongoDB 驱动程序中加入嵌套数组？

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