Group by field and calculate average value for another field

[zaartix (Алексей)]

Mapping:

player_id: int
stat_date: date
some_param: int

I need to calculate average value for "some_param" for all player_id used row with max "stat_date" in case of several rows with same player_id.

So i need average value for last date for all players

This snippet it not working because of "Aggregator [average_val] of type [avg] cannot accept sub-aggregations"

get test/test/_search
{
  "size":0,
  "aggs": {
    "average_val":{
      "avg": {
        "field": "some_param"
      },
      "aggs": {
        "by_player": {
          "terms": { "field" : "player_id" },
          "aggs" : {
              "by_date" : { 
                "max" : { "field" : "stat_date" } 
              }
          }
        }
      }
    }
  }
}

Simpliest way is use simple avg

get test/test/_search
{
  "size":0,
  "aggs": {
    "averages": {
      "avg": {
        "field": "some_param"
      }
    }
  }
}

But i need to calc avg player "some_param" only for last stat dates.