如何通过参考文档查询获取随机文档

Question

我有 3 个收藏（用户、信用和状态）。每个用户都有 1 个信用数据和许多状态数据，如下所示：

用户文档

[
  {
  "_id": ObjectId("669fbce1704d41e9040cbb41"),
  "Name": "First User"
  },
  {
  "_id": ObjectId("669fbce1704d41e9040cbb42"),
  "Name": "Second User"
  },
  {
  "_id": ObjectId("669fbce1704d41e9040cbb43"),
  "Name": "Third User"
  }
]

信用文件

[
  {
  "_id": ObjectId("669fbce1704d41e9040cbb44"),
  "userId": ObjectId("669fbce1704d41e9040cbb41"),
  "credit": 100
  },
  {
  "_id": ObjectId("669fbce1704d41e9040cbb45"),
  "userId": ObjectId("669fbce1704d41e9040cbb42"),
  "credit": 10
  },
  {
  "_id": ObjectId("669fbce1704d41e9040cbb46"),
  "userId": ObjectId("669fbce1704d41e9040cbb43"),
  "credit": 100
  }
]

状态文件

[
  {
    "_id": ObjectId("669fbce1704d41e9040cbb47"),
    "userId": ObjectId("669fbce1704d41e9040cbb41"),
    "status": "First User Status",
    "useCredit": 1
  },
  {
    "_id": ObjectId("669fbce1704d41e9040cbb48"),
    "userId": ObjectId("669fbce1704d41e9040cbb42"),
    "status": "Second User Status",
    "useCredit": 20
  },
  {
    "_id": ObjectId("669fbce1704d41e9040cbb49"),
    "userId": ObjectId("669fbce1704d41e9040cbb42"),
    "status": "Second User Status",
    "useCredit": 10
  },
  {
    "_id": ObjectId("669fbce1704d41e9040cbb4a"),
    "userId": ObjectId("669fbce1704d41e9040cbb43"),
    "status": "Third User Status",
    "useCredit": 3
  },
  {
    "_id": ObjectId("669fbdac704d41e9040cbb4c"),
    "userId": ObjectId("669fbce1704d41e9040cbb43"),
    "status": "Third User Status",
    "useCredit": 4
  },
  {
    "_id": ObjectId("669fbdac704d41e9040cbb4d"),
    "userId": ObjectId("669fbce1704d41e9040cbb43"),
    "status": "Third User Status",
    "useCredit": 2
  },
  {
    "_id": ObjectId("669fbdac704d41e9040cbb50"),
    "userId": ObjectId("669fbce1704d41e9040cbb43"),
    "status": "Third User Status",
    "useCredit": 2
  }
]

我想获得随机状态：

1. Status 的 userId 与用户“_id”不相等
2. 用户信用等于或大于状态的useCredit

示例：

如果第一个用户进行查询，他将从状态文档中获取一个随机数据，除了“_id：669fbce1704d41e9040cbb47”（因为自己的状态）和“_id：669fbce1704d41e9040cbb48”（因为信用不够）。

我正在考虑使用聚合，但我不知道该怎么做..

Answer 1

这应该达到目的

db.Status.aggregate([
  {
    $match: {
      userId: { $ne: ObjectId("123") } // Replace "123" with the current user's _id
    }
  },
  {
    $lookup: {
      from: "Credit",
      localField: "userId",
      foreignField: "userId",
      as: "creditInfo"
    }
  },
  {
    $unwind: "$creditInfo"
  },
  {
    $match: {
      $expr: {
        $gte: ["$creditInfo.credit", "$useCredit"]
      }
    }
  },
  {
    $sample: { size: 1 }
  }
]);