Function get_left_join_columns

ciphercore-base/src/evaluators/join.rs:314–356

Computes the left join of given sets. These sets and necessary precomputations should be contained in the join input.

(join_input: &JoinInput)

// Computes the left join of given sets.
// These sets and necessary precomputations should be contained in the join input.
fn get_left_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 one.
    // If yes, append the row of the first set with the columns of the second one.
    // If no, append it with zeros.
    for row_ind0 in 0..join_input.number_of_rows_set_0() {
        // If the null column entry is zero, just insert a zero row
        if join_input.set0.null_column[row_ind0] == 0 {
            result_columns.append_zero_row();
            continue;
        }
        // Add the columns of the first set first
        for (header0, _) in join_input.headers_types0.iter() {
            result_columns.copy_entry_from_column(header0, header0, &join_input.set0, row_ind0);
        }
        // If there are empty entries in the key columns, append the current row with zeros
        if join_input.row_has_empty_entries(row_ind0) {
            for header1 in &join_input.nonkey_headers1 {
                result_columns.append_zero_entry(header1);
            }
            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) {
            // Extract the corresponding row of the second set and attach to the row of the first 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 {
            // Append the current row with zeros
            for header1 in &join_input.nonkey_headers1 {
                result_columns.append_zero_entry(header1);
            }
        }
    }
    Ok(result_columns)
}

// Computes the union join of given sets.
// These sets and necessary precomputations should be contained in the join input.