presto-main/src/main/java/io/prestosql/execution/buffer/PartitionedOutputBuffer.java/PartitionedOutputBuffer/enqueue
class PartitionedOutputBuffer:    @Override
    public void enqueue(List<SerializedPage> pages)
    {
        checkState(partitions.size() == 1, "Expected exactly one partition");
        enqueue(0, pages);
    }