在 mongodb 中过滤数组 [英] Filter arrays in mongodb

问题描述

我有一个集合，其中每个文档包含 2 个文档数组，如下所示.

I have a collection where each document contains 2 arrays of documents as below.

{
  all_users:[
    {
      id:1,
      name:"A"
    },
    {
      id:2,
      name:"B"
    },
    {
      id:3,
      name:"C"
    }
  ]
  selected_users:[
    {
     id:1,
      name:"A"
    },
    {
      id:2,
      name:"B"
    }
  ]
}

是否可以通过添加字段 selected 并根据用户名称是否存在于 selected_users 中的文档中为其分配值来合并 2 个数组代码>数组如下.

Is it possible to merge the 2 arrays by adding a field selected and assigning a value to it based on whether the name of the user is present in a document in the selected_users array as follows.

{
  all_users:[
    {
      id:1,
      name:"A",
      selected:"yes"
    },
    {
      id:2,
      name:"B",
      selected:"yes"
    },
    {
      id:3,
      name:"C",
      selected:"no"
    }
  ]
}

我想通过 id 或 name 进行检查，因为文档可能包含其他字段.我不知道如何实现这一点.

I want to check by id or name since the documents may contain additional fields. I can't figure out how to achieve this.

推荐答案

• $map 迭代 all_users 数组的循环
• $cond 检查条件，如果 id 在选定用户 id 中，则返回yes"；否则否"在 selected 字段
• $mergeObject 将当前用户对象与上面的 selected 字段合并
• $map to iterate loop of all_users array
• $cond check condition if id is in selected users id then return "yes" otherwise "no" in selected field
• $mergeObject to merge current user object with above selected field

db.collection.aggregate([
  {
    $project: {
      all_users: {
        $map: {
          input: "$all_users",
          in: {
            $mergeObjects: [
              "$$this",
              {
                selected: {
                  $cond: [
                    { $in: ["$$this.id", "$selected_users.id"] },
                    "yes",
                    "no"
                  ]
                }
              }
            ]
          }
        }
      }
    }
  }
])

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