Function hashjoin::data_gen_fn

pub(crate) fn data_gen_fn<T>(
    description: ArgDataSet, 
    inner_rel_tuples: Option<usize>, 
    outer_rel_tuples: Option<usize>, 
    data_distribution: DataDistribution, 
    selectivity: Option<u32>
) -> (usize, usize, JoinDataGenFn<T>) where
    T: Copy + Send + KeyAttribute + FromPrimitive,