node.js - MongoDB 使用聚合根据条件从嵌套数组中删除对象

Question

我有一个嵌套数组，我必须根据使用聚合的条件删除一个对象

这是我从 mongodb 得到的 JSON

{
  "_id":  "633d275ceb34a28755974032",
  "name": "free",
  "products": [
    {
      "title": "Product 1",
      "phone": [
        {
          "title": "Best Phone 1 ",
          "video": {
            "Location": "https://video.mp4"
          },
          "freePreview": true
        }
      ]
    },
    {
      "title": "Product 2",
      "phone": [
        {
          "title": "Best Phone 2",
          "video": {
            "Location": "https://video.mp4"
          },
          "freePreview": false
        }
      ]
    }
    
  ] 
}

但是我需要这样的数据

{
  "_id":  "633d275ceb34a28755974032",
  "name": "free",
  "products": [
    {
      "title": "Product 1",
      "phone": [
        {
          "title": "Best Phone 1 ",
          "video": {
            "Location": "https://video.mp4"
          },
          "freePreview": true
        }
      ]
    },
    {
      "title": "Product 2",
      "phone": [
        {
          "title": "Best Phone 2",
          "freePreview": false
        }
      ]
    }
    
  ] 
}

由于 freePreview 为 false，此数据 “video object” 已从 phone 数组中移除，

Based upon the freePreview condition , help me to remove the video object

Answer 1

你需要使用双 $map运算符遍历数组数组并使用 $cond与 $$REMOVE 一起有条件地删除值:

db.collection.aggregate([
    {
        $addFields: {
            products: {
                $map: {
                    input: "$products",
                    as: "p",
                    in: {
                        title: "$$p.title",
                        phone: {
                            $map: {
                                input: "$$p.phone",
                                in: {
                                    title: "$$this.title",
                                    freePreview: "$$this.freePreview",
                                    video: {
                                        $cond: {
                                            if: {
                                                $eq: [
                                                    false,
                                                    "$$this.freePreview"
                                                ]
                                            },
                                            then: "$$REMOVE",
                                            else: "$$this.video"
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
])

Mongo Playground

Here's一个类似的例子。