Single query to find document with largest value for some field

Question

I've got a collection of documents that have unique numeric run ids, and I want to find the document with the highest run id.

I can do that two queries.

Firstly, I can find the highest run id:

{
    "size": 0,
    "aggregations": {
      "latest_run_id": {
        "aggregations": {
          "latest_run_id": {
            "max": {"field": "run_id"}
          }
        }
      }
    }
}

Secondly, I can find the document with that run id:

{
    "filter": {
        {"term": {"run_id": latest_run_id}}
    }
}

Is there a way I can do this with a single query?

Answer 1

You can accomplish this by combining "sort" and "size":

`{
  "filter" : {
    "match_all" : { }
  },
  "sort": [
    {
      "run_id": {
        "order": "desc"
      }
    }
  ],
  "size": 1
}`

This will return the record with the highest run_id

Answer 2

It is possible to retrieve entire document holding max value using top hits aggregation

{
    "size": 0,
    "aggs":{
        "doc_with_max_run_id": {
            "top_hits": {
                "sort": [
                    {
                        "latest_run_id": {
                            "order": "desc"
                        }
                    }
                ],
                "size": 1
            }
        }
    }
}

Also by modifying 'size' aggregation parameter it is possible to retrieve n-top documents.