node api 使用 mongoose 获取子文档

Question

我的 MongoDB 存储具有以下结构的文档：

{
    "application_detail":{},
    "curl_detail":{
        "Curl1":{
            "key1":"value1",
            "key2":"value2"
        },
        "Curl2":{
            "key1":"value1",
            "key2":"value2"        
        },
        "Curl3":{
            "key1":"value1",
            "key2":"value2"
        },
        "Curl4":{
            "key1":"value1",
            "key2":"value2"
        },
        /*total number of curls are unknown*/
    }
}

如何使用 express 和curl_detail从 mongoDB 中获取 curl_detail 下存在的所有卷发的key1 ？

预期输出：

{
    "curl_detail": {
        "Curl1": {
            "key1": "value1"
        },
        "Curl2": {
            "key1": "value1"
        },
        "Curl3": {
            "key1": "value1"
        },
        "Curl4": {
            "key1": "value1"
        }
    }
}

注意：卷发总数未知。

Answer 1

我想建议你改变数据结构

"curl_detail": {
    "Curl1": {
        "key1": "value1",
        "key2": "value2"
    },
    "Curl2": {
        "key1": "value1",
        "key2": "value2"
    }
}

到

"curl_detail": [{
        "key1": "value1",
        "key2": "value2"
    },
    {
        "key1": "value1",
        "key2": "value2"
    }
]

将数据结构存储在数组中可以让您以更简单的方式找到一些数据。 此外，不需要具有Curl1 、 Curl2等属性的对象。

对于新的数据结构，已经有一些答案和解释：

1) Mongo 查找父键未知的值

2）当父键未知时按值查询MongoDB

3） MongoDB：在具有未知键的对象中查找给定字段值的文档

更新

如果无法更改数据结构，请参阅此解决方案（使用$arrayToObject / $objectToArray $arrayToObject来确定嵌套键的名称，例如“Curl1”的技巧）：

db.collection.aggregate([{
        $addFields: {
            curl_detail: {
                $arrayToObject: {
                    $map: {
                        input: {
                            $objectToArray: "$curl_detail"
                        },
                        as: "details",
                        in: {
                            k: "$$details.k",
                            v: {
                                key1: "$$details.v.key1"
                            }
                        }
                    }
                }
            }
        }
    },
    {
        $project: {
            _id: 0,
            curl_detail: 1
        }
    }
])

这将输出以下内容：

[
  {
    "curl_detail": {
      "Curl1": {
        "key1": "value1"
      },
      "Curl2": {
        "key1": "value1"
      },
      "Curl3": {
        "key1": "value1"
      },
      "Curl4": {
        "key1": "value1"
      }
    }
  }
]

您可以通过Mongo Playground查看

Answer 2

您可以对要查找的查询使用投影：

collection.find({}, {"curl_detail":1}, (findError, results) => {
  if(findError) { 
    //handle the error
    return;
  }
  // here is the expected result
  console.log();
});

Answer 3

如果此结果也适用于您：

[
  {
    "curl_detail": {
      "Curl1": "value1",
      "Curl2": "value1",
      "Curl3": "value1",
      "Curl4": "value1"
    }
  }
]

您可以使用使用下面的聚集$ objectToArray和$ arrayToObject

db.collection.aggregate([
  {
    $addFields: {
      curl_detail: {
        $map: {
          "input": {
            "$objectToArray": "$curl_detail"
          },
          "as": "el",
          "in": {
            "k": "$$el.k",
            "v": "$$el.v.key1",

          }
        }
      }
    }
  },
  {
    $project: {
      _id: 0,
      curl_detail: {
        $arrayToObject: "$curl_detail"
      }
    }
  }
])

操场

您可以像这样将这种聚合与猫鼬一起使用，假设您的模型是 MyModel：

MyModel.aggregate([
  {
    $addFields: {
      curl_detail: {
        $map: {
          input: {
            $objectToArray: '$curl_detail'
          },
          as: 'el',
          in: {
            k: '$$el.k',
            v: '$$el.v.key1'
          }
        }
      }
    }
  },
  {
    $project: {
      _id: 0,
      curl_detail: {
        $arrayToObject: '$curl_detail'
      }
    }
  }
]).then(res => {
  console.log(res);
});