mongodb find largest key inside an item in mongodb

Question

I have a mongodb collection that has the following schema

{
  _id: ,
  data: {
       1: {
          values: ...
       },
       3: {
           values: ...
       }
       2: {
          values: ...
       }
   }
}

and I wanted to know if it would be possible to sort the items inside the data object or pick the highest values using core mongodb instead of retrieving them and sorting using javascript.

Answer 1

Please read @NeilLunn's comments to the question first

The "possible" yet "impractical" pipeline could be like following:

db.collection.aggregate([
    {$project: {
        data: { $objectToArray: "$data" }
    }}, 
    {$unwind: "$data"},
    {$sort: {_id:1, "data.k":-1}},
    {$group: {_id:"$_id", data:{$first:"$data"}}},
    {$group: {_id:"$_id", data:{$push:"$data"}}},
    {$project: {
        _id: 1,
        data: { $arrayToObject: "$data" }            
    }}
])