Nested Aggregation in Nest Elastic Search

Question

In my Elastic document i have CityId,RootId,RootName,Price.Now i have to find top 7 roots in a city with following conditions.

Name and id of root which has minimum price in a City.
top 7 roots:- roots those have max number of entry in a City.

for Example :-

CityId RootId RootName Price
11      1       ABC      90
11      1       ABC      100
11      2       DEF      80
11      2       DEF      90
11      2       DEF      60

answer for CityId =11:-

RootId RootName Price
2       DEF      60
1       ABC      90

Answer 1

I am not aware of the syntax of the Nest. Adding a working example in JSON format.

Index Mapping:

{
  "mappings":{
    "properties":{
      "listItems":{
        "type":"nested"
      }
    }
  }
}

Index Data:

{
    "RootId": 2,
    "CityId": 11,
    "RootName": "DEF",
    "listItems": [
        {
            "Price": 60
        },
        {
            "Price": 90
        },
        {
            "Price": 80
        }
    ]
}
{
    "RootId": 1,
    "CityId": 11,
    "RootName": "ABC",
    "listItems": [
        {
            "Price": 100
        },
        {
            "Price": 90
        }
    ]
}

Search Query:

{
    "size": 0,
    "aggs": {
        "id_terms": {
            "terms": {
                "field": "RootId"
            },
            
            "aggs": {
                "nested_entries": {
                    "nested": {
                        "path": "listItems"
                    },
                    "aggs": {
                        "min_position": {
                            "min": {
                                "field": "listItems.Price"
                            }
                        }
                    }
                }
            }
        }
    }
}

Search Result:

"aggregations": {
    "id_terms": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": 1,
          "doc_count": 1,
          "nested_entries": {
            "doc_count": 2,
            "min_position": {
              "value": 90.0
            }
          }
        },
        {
          "key": 2,
          "doc_count": 1,
          "nested_entries": {
            "doc_count": 3,
            "min_position": {
              "value": 60.0
            }
          }
        }
      ]
    }
  }