presto-main/src/main/java/io/prestosql/execution/executor/TaskExecutor.java/RunningSplitInfo/compareTo
class RunningSplitInfo:        @Override
        public int compareTo(RunningSplitInfo o)
        {
            return ComparisonChain.start()
                    .compare(startTime, o.getStartTime())
                    .compare(threadId, o.getThreadId())
                    .result();
        }