Groep en som volgens het positiepercentage MongoDb Aggregation

Je kunt onderstaande aggregatie proberen in 3.4 pijplijn.

Wijs gewichten toe op basis van de positie van het element.

$switch case om verschillende gewichten te geven op basis van de grootte van de array.

db.col.aggregate([{"$addFields":{
  "myArray":{
    "$switch":{
      "branches":[{
        "case":{"$gt":[{"$size":"$myArray"},2]},
        "then":{"$concatArrays":[
            [{"value":{"$arrayElemAt":["$myArray.value",0]},"weight":{"$divide":[2,5]}}],
            {"$map":{
              "input":{"$slice":["$myArray",1,{"$subtract":[{"$size":"$myArray"},2]}]},
              "as":"val",
              "in":{"value":"$$val.value","weight":{"$divide": [{"$divide":[1,5]},{"$subtract":[{"$size":"$myArray"},2]} ]}}
            }},
            [{"value":{"$arrayElemAt":["$myArray.value",-1]},"weight":{"$divide":[2,5]}}]
          ]}
       },
       {
        "case":{"$eq":[{"$size":"$myArray"},2]},
        "then":{"$concatArrays":[
          [{"value":{"$arrayElemAt":["$myArray.value",0]},"weight":{"$divide":[1,2]}}],
          [{"value":{"$arrayElemAt":["$myArray.value",-1]},"weight":{"$divide":[1,2]}}]
        ]}
       }],
    "default":{"$concatArrays":[
      [{"value":{"$arrayElemAt":["$myArray.value",0]},"weight":1}],
    ]}}
  }
}},
{"$unwind":"$myArray"},
{"$group":{
  "_id":"$myArray.value",
  "linear_total":{"$sum":{"$multiply":["$myArray.weight","$total"]}}
}},
{"$sort":{"_id":1}}])