Elasticsearch max of field combined with a unique field

Question

I have an index with two fields:

• name: uuid
• version: long

I now only want to count the documents (on a very large index [1 million+ entries]) where the version of the name is the highest. For e.g. a query on an index with the following documents:

{name="a", version=1} 
{name="a", version=2}
{name="a", version=3}
{name="b", version=1}

... would return:

count=2

Is this somehow possible? I can not find a solution for this particular problem.

Answer 1

You are effectively describing a count of distinct names, which you can do with a cardinality aggregation.

Request:

GET test1/_search
{
    "aggs" : {
        "distinct_count" : {
            "cardinality" : {
                "field" : "name.keyword"
            }
        }
    },
    "size": 0
}

Response:

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 4,
    "max_score" : 0.0,
    "hits" : [ ]
  },
  "aggregations" : {
    "distinct_count" : {
      "value" : 2
    }
  }
}