presto-main/src/main/java/io/prestosql/execution/buffer/LazyOutputBuffer.java/LazyOutputBuffer/enqueue
class LazyOutputBuffer:    @Override
    public void enqueue(int partition, List<SerializedPage> pages)
    {
        OutputBuffer outputBuffer;
        synchronized (this) {
            checkState(delegate != null, "Buffer has not been initialized");
            outputBuffer = delegate;
        }
        outputBuffer.enqueue(partition, pages);
    }