@Override public String toString() {
    return "HiveDruidSplit{" + druidQuery + ", " + (hosts == null ? "empty hosts" : Arrays.toString(hosts)) + "}";
  }
Druid split. Its purpose is to trigger query execution in Druid.
druid-handler/src/java/org/apache/hadoop/hive/druid/io/HiveDruidSplit.java