GET /my-index-000001/_search
{
  "query": {
    "match": {
      "message": "GET /search"
    }
  },
  "collapse": {
    "field": "user.id",                      
      "inner_hits": [
      {
        "name": "largest_responses",         
        "size": 3,
        "sort": [ "http.response.bytes" ]
      },
      {
        "name": "most_recent",               
        "size": 3,
        "sort": [ { "@timestamp": "asc" } ]
      }
    ]
  },
  "sort": [ "http.response.bytes" ]
}