    * @Param row_index The row of the table to compute the hash value for
    * @Param num_columns_to_hash The number of columns in the row to hash. If 0, hashes all columns
    * @tparam hash_function The hash function that is used for each element in the row
-   * @tparam dummy Used only to be able to resolve the result_type from the hash_function.
-                   The actual type of dummy doesn't matter.
    * 
    * @Returns The hash value of the row
    */


    // If num_columns_to_hash is zero, hash all columns
    if(0 == num_columns_to_hash)
      num_columns_to_hash = this->num_columns;

    for(size_type i = 0; i < num_columns_to_hash; ++i)
    {

    : num_columns(num_cols), host_columns(gdf_columns)
  {

    assert(num_cols > 0);
    assert(nullptr != host_columns[0]);
    column_length = host_columns[0]->size;

    if(column_length > 0)
    {
      assert(nullptr != host_columns[0]->data);
    }

    // Copy the pointers to the column's data and types to the device 
    // as contiguous arrays
