Query all unique values of a field with Elasticsearch

Question

How do I search for all unique values of a given field with Elasticsearch?

I have such a kind of query like select full_name from authors

Answer 1

For Elasticsearch 1.0 and later, you can leverage terms aggregation to do this,

query DSL:

{
  "aggs": {
    "NAME": {
      "terms": {
        "field": "",
        "size": 10
      }
    }
  }
}

A real example:

{
  "aggs": {
    "full_name": {
      "terms": {
        "field": "authors",
        "size": 0
      }
    }
  }
}

Then you can get all unique values of authors field. size=0 means not limit the number of terms(this requires es to be 1.1.0 or later).

Response:

{
    ...

    "aggregations" : {
        "full_name" : {
            "buckets" : [
                {
                    "key" : "Ken",
                    "doc_count" : 10
                },
                {
                    "key" : "Jim Gray",
                    "doc_count" : 10
                },
            ]
        }
    }
}

see Elasticsearch terms aggregations.