presto-main/src/main/java/io/prestosql/execution/executor/MultilevelSplitQueue.java/MultilevelSplitQueue/size
class MultilevelSplitQueue:    public int size()
    {
        lock.lock();
        try {
            int total = 0;
            for (PriorityQueue<PrioritizedSplitRunner> level : levelWaitingSplits) {
                total += level.size();
            }
            return total;
        }
        finally {
            lock.unlock();
        }
    }