MongoDB两层嵌套数组文档的条件式更新实现求助

仅在满足以下三个条件时，将匹配的spotsAvailable字段替换为{ userId: ObjectId(), name: "wendy" }：

• 文档_id = 636c2c6dcb82e7ae6aac0960
• weights.weight = 0
• weights.spotsAvailable.userId = "empty"

示例文档 #

{
  "_id": {
    "$oid": "636c2c6dcb82e7ae6aac0960"
  },
  "name": "onmygowd",
  "createdBy": {
    "$oid": "636c1778f1d09191074f9690"
  },
  "description": "It's gonnam be a good one",
  "date": {
    "$date": {
      "$numberLong": "1667913330000"
    }
  },
  "location": {
    "type": "Point",
    "coordinates": [
      0,
      0
    ]
  },
  "weights": [
    {
      "spotsAvailable": [
        {
          "name": "empty",
          "userId": "empty"
        },
        {
          "name": "John",
          "userId": {
            "$oid": "636c1778f1d09191074f9690"
          }
        }
      ],
      "weight": 0
    },
    {
      "spotsAvailable": [
        {
          "name": "empty",
          "userId": "empty"
        },
        {
          "name": "John",
          "userId": {
            "$oid": "636c1778f1d09191074f9690"
          }
        }
      ],
      "weight": 123
    }
  ],
  "eventApplicants": [
    {
      "userId": {
        "$oid": "636c1778f1d09191074f9690"
      },
      "name": "wallace",
      "weight": 123.1
    }
  ]
}

失败的尝试 #

1

db.events.updateOne({ _id: ObjectId('636c2c6dcb82e7ae6aac0960'), "weights.weight": 0 },
            { $set: { "weights.spotsAvailable.$[el2]":  { "name": "George", "userId": ObjectId('636c1778f1d09191074f9690') } } },
            { arrayFilters: [{"el2.userId": "empty"}] })

---

**2** ```javascript db.events.updateOne(db.events.findOne({_id: ObjectId('636c2c6dcb82e7ae6aac0960'), "weights.weight": 0, "weights.spotsAvailable.userId": "empty"}, {$set: {"weights.$[el].spotsAvailable": {"name": "George", "userId": ObjectId('636c1778f1d09191074f9690')}}}, {arrayFilters:[{"el.spotsAvailable.userId": "empty"}] }) ```

---

**3** ```javascript db.events.updateOne({ _id: ObjectId('636c2c6dcb82e7ae6aac0960'), "weights.weight": 0 }, { $set: { "weights.$[el].spotsAvailable.$[el2]": { "name": "George", "userId": ObjectId('636c1778f1d09191074f9690') } } }, { arrayFilters: [{"el.el2.userId": "empty"}] }) ```

正确实现方法 #

你的三次尝试存在以下问题：

1. 第一次未定位到weights数组中weight=0的具体元素，直接操作weights.spotsAvailable导致路径错误。
2. 第二次错误将db.events.findOne()作为updateOne的查询参数，updateOne第一个参数必须是查询文档而非查询结果。
3. 第三次arrayFilters条件写法错误，el.el2.userId不是正确的嵌套数组过滤语法，需为两个数组过滤器指定独立匹配条件。

正确的更新语句如下：

db.events.updateOne(
  { 
    _id: ObjectId('636c2c6dcb82e7ae6aac0960'),
    "weights.weight": 0
  },
  {
    $set: {
      "weights.$[weightEl].spotsAvailable.$[spotEl]": { 
        "userId": ObjectId(), 
        "name": "wendy" 
      }
    }
  },
  {
    arrayFilters: [
      { "weightEl.weight": 0 },
      { "spotEl.userId": "empty" }
    ]
  }
)

代码解释 #

• 查询条件：匹配指定_id的文档，且文档weights数组存在weight=0的元素。
• $set操作：通过$[weightEl]定位weights数组中符合条件的元素，再用$[spotEl]定位该元素下spotsAvailable数组中匹配的子元素，完成替换。
• arrayFilters：
  • { "weightEl.weight": 0 }：筛选weights数组中weight等于0的元素，对应路径中的$[weightEl]。
  • { "spotEl.userId": "empty" }：筛选spotsAvailable数组中userId为"empty"的元素，对应路径中的$[spotEl]。

内容的提问来源于stack exchange，提问作者Wayne