presto-main/src/main/java/io/prestosql/execution/executor/TaskExecutor.java/TaskExecutor/toString
class TaskExecutor:    @Override
    public synchronized String toString()
    {
        return toStringHelper(this)
                .add("runnerThreads", runnerThreads)
                .add("allSplits", allSplits.size())
                .add("intermediateSplits", intermediateSplits.size())
                .add("waitingSplits", waitingSplits.size())
                .add("runningSplits", runningSplits.size())
                .add("blockedSplits", blockedSplits.size())
                .toString();
    }