按猫鼬中的孙子属性过滤

Posted 2023-03-11

【中文标题】按猫鼬中的孙子属性过滤

【英文标题】：Filtering By Grandchild property in mongoose

【发布时间】：2021-12-23 02:36:21

【问题描述】：

我对猫鼬很陌生，我想知道是否可以根据孙子属性进行过滤。我到处寻找，但我无法根据我正在尝试做的事情找到类似的问题。这是场景：

想象一下我有一个这样的数据库：

db=
  "parents": [
    
      "_id": ObjectId("5a834e000102030405000000"),
      "child": ObjectId("5a934e000102030405000000")
    ,
    
      "_id": ObjectId("5a834e000102030405000001"),
      "child": ObjectId("5a934e000102030405000001")
    ,
    
      "_id": ObjectId("5a834e000102030405000002"),
      "child": ObjectId("5a934e000102030405000002")
    ,
    
  ],
  "children": [
    
      "_id": ObjectId("5a934e000102030405000000"),
      "grandchild": ObjectId("5a734e000102030405000000")
    ,
    
      "_id": ObjectId("5a934e000102030405000001"),
      "grandchild": ObjectId("5a734e000102030405000001")
    ,
    
      "_id": ObjectId("5a934e000102030405000002"),
      "grandchild": ObjectId("5a734e000102030405000002")
    
  ],
  "grandchildren": [
    
      "_id": ObjectId("5a734e000102030405000000"),
      "name": "grandchild1"
    ,
    
      "_id": ObjectId("5a734e000102030405000001"),
      "name": "grandchild2"
    ,
    
      "_id": ObjectId("5a734e000102030405000002"),
      "name": "grandchild3"
    
  ]

我想返回所有有孙子名字为“grandchild1”的父母。

类似的东西

$match: 
      "child.grandchild.name": "grandchild1"
    

所以结果中只会返回这个父级--

[
  "_id": ObjectId("5a834e000102030405000000"),
  "child": ObjectId("5a934e000102030405000000")
,]

【参考方案1】：

我在任何人反应之前就找到了答案……

https://mongoplayground.net/p/w1kw58PzCyk

db.parents.aggregate([
  
    $lookup: 
      from: "children",
      localField: "child",
      foreignField: "_id",
      as: "child",
      
    
  ,
  
    $addFields: 
      child: 
        $arrayElemAt: [
          "$child",
          0
        ]
      
    
  ,
  
    "$lookup": 
      from: "grandchildren",
      localField: "child.grandchild",
      foreignField: "_id",
      as: "grandchild",
      
    
  ,
  
    $addFields: 
      grandchild: 
        $arrayElemAt: [
          "$grandchild",
          0
        ]
      
    
  ,
  
    $match: 
      "grandchild.name": "grandchild1"
    
  
])