Finding top N entries from the Array

Question

My collection is structured like this:

{
    \"_id\": 1,
    \"Trips\": [
        {
            \"EndID\": 5,
            \"Tripcount\": 12
        },
        {
         


        

Answer 1

Basically you need to sort the array elements ($unwind/$sort/$group) and then you can do your $sort for the top values and $limit the results.

Finally you $slice for the "top N" in the documents in the array.

db.eplat1.aggregate([
  { "$unwind": "$Trips" },
  { "$sort": { "_id": 1, "Tips.TripCount": -1 } },
  { "$group": {
    "_id": "$_id",
    "Trips": { "$push": "$Trips" },
    "maxTrip": { "$max": "$Trips.TripCount" }
  }},
  { "$sort": { "maxTrip": -1 } },
  { "$limit": 50 },
  { "$addFields": { "Trips": { "$slice": [ "$Trips", 0 , 2 ] } } }
])