Compute terms agg on non analyzed terms.

aggs-not-analyzed.sense

DELETE test
PUT test
{
  "mappings": {
    "test": {
      "properties": {
        "deviceId": {
          "type": "string",
          "index": "not_analyzed"
        },
        "basics": {
          "properties": {
            "sex": {
              "type": "string",
              "index": "not_analyzed"
            },
            "device": {
              "type": "string",
              "index": "not_analyzed"
            }
          }
        }
      }
    }
  }
}

PUT /test/test/1
{
  "basics": {
    "sex": "m",
    "device": "LGE LG-P768"
  },
  "deviceId": "1"
}

PUT /test/test/2
{
  "basics": {
    "sex": "m",
    "device": "Samsung SHW-M250S"
  },
  "deviceId": "2"
}

GET /test/test/_search?search_type=count
{
  "aggregations": {
    "popular_devices": {
      "terms": {
        "field": "device"
      }
    }
  }
}