Function get_inner_join_columns

ciphercore-base/src/evaluators/join.rs:246–276

Computes the inner join of given sets.

(join_input: &JoinInput)

// Computes the inner join of given sets.
fn get_inner_join_columns(join_input: &JoinInput) -> Result<ColumnsMap> {
    let mut result_columns = ColumnsMap::init_result_columns(join_input)?;

    // Check row by row that the content of the key columns of the first set intersects with the second set
    for row_ind0 in 0..join_input.number_of_rows_set_0() {
        // If the null column entry is zero or there are empty entries, just insert a zero row
        if join_input.row_has_empty_entries(row_ind0) {
            result_columns.append_zero_row();
            continue;
        }
        // Merge the key columns of the first set
        let row_key = join_input
            .set0
            .get_flattened_row(row_ind0, &join_input.key_headers0);
        // Check that the row key of the first set is contained in the second set
        if join_input.key_data_hashmap1.contains_key(&row_key) {
            // Add the columns of the first set first
            for (header0, _) in join_input.headers_types0 {
                result_columns.copy_entry_from_column(header0, header0, &join_input.set0, row_ind0);
            }
            // Extract the corresponding row of the second set
            let row_ind1 = join_input.key_data_hashmap1[&row_key];
            for header1 in &join_input.nonkey_headers1 {
                result_columns.copy_entry_from_column(header1, header1, &join_input.set1, row_ind1);
            }
        } else {
            result_columns.append_zero_row();
        }
    }
    Ok(result_columns)
}

// Preprocessed input of join algorithms.
// Note that it contains a hashmap of the rows of the second set hashed by their key columns, which simplifies computation of the set intersection