Elasticsearch group by having (aggs)

Elastic Stack Elasticsearch
1

I have following query.

POST test/_search?size=0
{
   "size": 0,
      "aggs": {
        "group_by_RequestID": {
          "terms": {
            "field": "RequestID"
          },
           "aggs": {
               "total_hits": {
                    "top_hits": {
                       "_source": {
                            "include": [
                                "_none"
                            ]
                        }
                }
            }
      }
    }
  }
}

Response:-

"aggregations": {
    "group_by_RequestID": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "20160209 132857.249_5420_1_DEN1100",
          "doc_count": 2,
          "total_hits": {
            "hits": {
              "total": 2,
              "max_score": 1,
              "hits": [
                {
                  "_index": "test",
                  "_type": "logs",
                  "_id": "20160209 132857.249_5420_1_DEN1100_Request",
                  "_score": 1,
                  "_source": {}
                },
                {
                  "_index": "test",
                  "_type": "logs",
                  "_id": "20160209 132857.249_5420_1_DEN1100_Response",
                  "_score": 1,
                  "_source": {}
                }
              ]
            }
          }
        },
        {
          "key": "20160209 132857.249_5420_1_SFO",
          "doc_count": 1,
          "total_hits": {
            "hits": {
              "total": 1,
              "max_score": 1,
              "hits": [
                {
                  "_index": "test",
                  "_type": "logs",
                  "_id": "20160209 132857.249_5420_1_SFO_Request",
                  "_score": 1,
                  "_source": {}
                }
              ]
            }
          }

For each key I have Request and Response. my result should be the key where I don't have Response, so output should be "20160209 132857.249_5420_1_SFO"

Also How can i get the number of key is missing Response.

Thanks