查询元素，如果它们的对象数组具有重复元素的属性

Question

通过收集包含以下文档：

{
    "_id" : "1",
    "Name" : "Name1",
    "Children" : [ 
        {
            "_id" : "1",
            "Name" : "Name1",
            "Type" : "One"
        }, 
        {
            "_id" : "2",
            "Name" : "Name2",
            "Type" : "One"
        }, 
        {
            "_id" : "5",
            "Name" : "Name5",
            "Type" : "Two"
        },
    ]
},
{
    "_id" : "2",
    "Name" : "Name2",
    "Children" : [ 
        {
            "_id" : "3",
            "Name" : "Name3",
            "Type" : "One"
        }, 
                {
            "_id" : "4",
            "Name" : "Name4",
            "Type" : "Two"
        }, 
    ]
},
{
    "_id" : "3",
    "Name" : "Name3",
    "Children" : [ 
        {
            "_id" : "7",
            "Name" : "Name7",
            "Type" : "Two"
        }, 
                {
            "_id" : "6",
            "Name" : "Name6",
            "Type" : "Two"
        }, 
    ]
}

我只想在 Children 包含具有重复 Type 属性的对象时查询文档。例如对象 1 具有三个对象的 Children，其属性 Type 出现两次（一、一、二）。对象 3 有两个 Children 对象，它们都有 Type = Two。对象 2 具有所有唯一的 Children（一、二）。因此查询将匹配对象 1 和 3。

Answer 1

这可能会对您有所帮助.. 这背后的想法，我们将有孩子总数并在删除重复项后进行比较。如果两个计数都不匹配，那么我们将其作为文档获取

• $reduce 统计孩子的总数并将有一个重复的孩子 (dupChildren)
• $unwind 解构数组
• $project 删除不需要的数据。由于我们需要匹配$type，所以我们删除dupChildren中的其他人
• $group 重构数组以删除重复的type，
• $size 统计dupChildren 数组
• $match 如果 totalChildren 和 count 都相等，则消除
• $project 删除不需要的字段

这是脚本

db.collection.aggregate([
  {
    $addFields: {
      totalChildren: {
        $reduce: {
          input: "$Children",
          initialValue: 0,
          in: {
            $add: [ "$$value", 1 ]
          }
        }
      },
      dupChildren: "$Children"
    }
  },
  {
    $unwind: "$dupChildren"
  },
  {
    $project: {
      "dupChildren._id": 0,
      "dupChildren.Name": 0
    }
  },
  {
    $group: {
      _id: "$_id",
      Name: { $first: "$Name" },
      Children: { $first: "$Children" },
      totalChildren: { $first: "$totalChildren" },
      dupChildren: { $addToSet: "$dupChildren" }
    }
  },
  {
    $addFields: {
      count: { $size: "$dupChildren" }
    }
  },
  {
    $match: {
      $expr: {
        $ne: [ "$totalChildren", "$count" ]
      }
    }
  },
  {
    $project: {
      dupChildren: 0,
      count: 0,
      totalChildren: 0
    }
  }
])

工作Mongo playground