presto-main/src/main/java/io/prestosql/execution/buffer/BroadcastOutputBuffer.java/BroadcastOutputBuffer/enqueue
class BroadcastOutputBuffer:    @Override
    public void enqueue(int partitionNumber, List<SerializedPage> pages)
    {
        checkState(partitionNumber == 0, "Expected partition number to be zero");
        enqueue(pages);
    }