I did check on multiple platforms for the solution, however did not get the answer. Here is my problem:
I have a nested Mongo Document of the format:

{
    _id: "xxxx",
    "Type": <value>,
    "Data" : {
        "1": {                        <<< this key might differ for diff documents
            "00": {                   <<< this key might differ for diff documents
                 "cont": "India"
            },
            "05": {
                 "cont": "India"
            },
            ....
         }
         "32": {
            "41": {
                 "cont": "India"
            },
            "44": {
                 "cont": "India"
            },
            ....
        }
    }
}

I want to rename the key cont to country in all the documents in the collection, however as mentioned above the key 1, 00, 32 might differ for different documents hence I could not reach to a solution for this. Is there something like:

db.collection.updateMany({Type: "abc"}, { $rename: { "Data.*.*.cont": "Data.*.*.country" }})

because the key cont resides at the third level after the key Data

Can someone please help me out here?
Thanks!

CodePudding user response：

Using dynamic value as field name is generally considered as an anti-pattern. Nevertheless, you can still use $objectToArray to convert the nested objects into k-v tuples and manipulate them. Then converted it back using $arrayToObject

db.collection.update({},
[
  {
    "$addFields": {
      "arr": {
        // first conversion
        "$objectToArray": "$Data"
      }
    }
  },
  {
    "$addFields": {
      "arr": {
        // second conversion
        "$map": {
          "input": "$arr",
          "as": "a",
          "in": {
            k: "$$a.k",
            v: {
              "$objectToArray": "$$a.v"
            }
          }
        }
      }
    }
  },
  {
    "$addFields": {
      "arr": {
        "$map": {
          "input": "$arr",
          "as": "a",
          "in": {
            k: "$$a.k",
            v: {
              "$map": {
                "input": "$$a.v",
                "as": "a2",
                "in": {
                  k: "$$a2.k",
                  // rename the field `country`
                  v: {
                    country: "$$a2.v.cont"
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  {
    "$addFields": {
      "arr": {
        "$map": {
          "input": "$arr",
          "as": "a",
          "in": {
            k: "$$a.k",
            v: {
              // 1st backward conversion
              "$arrayToObject": "$$a.v"
            }
          }
        }
      }
    }
  },
  {
    "$project": {
      _id: 1,
      Type: 1,
      "Data": {
        // 2nd backward conversion
        "$arrayToObject": "$arr"
      }
    }
  }
])

Here is the Mongo playground for your reference.