public ConcurrentHashMap<String, ListOrderedMap<Long, Long>> getTopKEvents() {
    return topKEvents;
  }
Gets the top K costliest event per event type.
@return A HashMap with key as the event type and a Map as values, which has the event id as key and time taken
as values.
ql/src/java/org/apache/hadoop/hive/ql/exec/repl/ReplStatsTracker.java