Request.json

PUT t
{
  "mappings": {
    "t": {
      "properties": {
        "bool": {
          "type": "boolean"
        }
      }
    }
  }
}

PUT t/t/1
{"bool":true}

PUT t/t/2
{"bool":false}

GET t/_search
{
  "_source": "bool",
  "script_fields": {
    "bool": {
      "script": "doc['bool'].value ? 'true' : 'false'"
    }
  },
  "aggs": {
    "bool": {
      "meta": {
        "is_boolean": true
      },
      "terms": {
        "field": "bool"
      }
    }
  }
}

Result.json

{
  "took": 6,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 2,
    "max_score": 1,
    "hits": [
      {
        "_index": "t",
        "_type": "t",
        "_id": "2",
        "_score": 1,
        "_source": {
          "bool": false
        },
        "fields": {
          "bool": [
            "false"
          ]
        }
      },
      {
        "_index": "t",
        "_type": "t",
        "_id": "1",
        "_score": 1,
        "_source": {
          "bool": true
        },
        "fields": {
          "bool": [
            "true"
          ]
        }
      }
    ]
  },
  "aggregations": {
    "bool": {
      "meta": {
        "is_boolean": true
      },
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": 0,
          "key_as_string": "false",
          "doc_count": 1
        },
        {
          "key": 1,
          "key_as_string": "true",
          "doc_count": 1
        }
      ]
    }
  }
}