嵌套查找和过滤

Question

我有以下收藏

用户

[
{
  id : 'acd-1234',
  name : 'some name',
  profile_id : 1,
  is_graduate: true, 
  children: [
    { class: 'User', id: 'abcd-123'},
    { class: 'User', id: 'bcd-33'}
  ]
},
{
  id: 'abcd-123',
  name : 'jhon',
  profile_id : 2
  is_graduate: true, 
},
{
  id: 'bcd-123',
  name : 'jhon due',
  profile_id : 3,
  is_graduate: false 
}
] 

个人资料

[
  {
    id: 1,
    address: 'some address'  
  },
  {
    id: 2,
    address: 'some other address'  
  },
  {
    id: 3,
    address: 'some other other address'  
  }

]

我需要的最终输出是（父母只有研究生）

[
  {
    id: 'acd-1234',
    name: 'some name',
    is_graduate: true, 
    profile : {
       id: 1,
       address: "some address"
    },
    children: [
       {
         id: "abcd-123",
         name: "jhon",
         is_graduate: true, 
         profile: {
           id: 2,
           address: "some other address" 
         }
       }
    ] 
  }
]

我真正陷入困境的地方是

1. 进行嵌套查找。显示所有孩子的个人资料
2. 对孩子应用过滤

来自 mongo 的以下错误不允许我使用带有 localField 的管道 $lookup with 'pipeline' may not specify 'localField' or 'foreignField'

Answer 1

试试这个：

db.users.aggregate([
    {
        $lookup: {
            from: "profile",
            let: { id: "$profile_id" },
            pipeline: [
                {
                    $match: {
                        $expr: { $eq: ["$id", "$$id"] }
                    }
                }
            ],
            as: "profile"
        }
    },
    { $unwind: "$profile" },
    {
        $lookup: {
            from: "users",
            let: {
                id: { $ifNull: ["$children.id", []] }
            },
            pipeline: [
                {
                    $match: {
                        $expr: { $in: ["$id", "$$id"] }
                    }
                },
                {
                    $lookup: {
                        from: "profile",
                        localField: "profile_id",
                        foreignField: "id",
                        as: "profile"
                    }
                },
                { $unwind: "$profile" }
            ],
            as: "children"
        }
    }
]);

如果您只想显示非空children，则在最后一个$lookup 之后添加$match 阶段：

{
    $match: {
        $expr: {
            $gt: [{ $size: "$children" }, 0]
        }
    }
}