Function apply_join_operation

crates/gitql-engine/src/engine_join.rs:16–145

(
    env: &mut Environment,
    all_rows: &mut Vec<Row>,
    joins: &Vec<Join>,
    tables_selections: &Vec<TableSelection>,
    selected_rows_per_table: &mut HashMap<String, Vec<Row>>,
    hidden_se

#[inline(always)]
pub(crate) fn apply_join_operation(
    env: &mut Environment,
    all_rows: &mut Vec<Row>,
    joins: &Vec<Join>,
    tables_selections: &Vec<TableSelection>,
    selected_rows_per_table: &mut HashMap<String, Vec<Row>>,
    hidden_selection_per_table: &HashMap<String, usize>,
    titles: &[String],
) -> Result<(), String> {
    // If no join, just merge them, can be optimized to append only the first value in the map
    if joins.is_empty() {
        for table_selection in tables_selections {
            let table_rows = selected_rows_per_table
                .get_mut(&table_selection.table_name)
                .unwrap();
            all_rows.append(table_rows);
        }
        return Ok(());
    }

    let mut current_tables_rows: Vec<Row> = vec![];
    let mut all_rows_hidden_count = 0;

    // Apply join operator depend on the join type
    for join in joins {
        let mut current_join_rows: Vec<Row> = vec![];

        let left_rows: &Vec<Row>;
        let left_hidden_count: usize;

        let right_rows: &Vec<Row>;
        let right_hidden_count: usize;

        match &join.operand {
            JoinOperand::OuterAndInner(outer, inner) => {
                left_hidden_count = *hidden_selection_per_table.get(outer).unwrap_or(&0);
                right_hidden_count = *hidden_selection_per_table.get(inner).unwrap_or(&0);
                all_rows_hidden_count += left_hidden_count + right_hidden_count;

                left_rows = selected_rows_per_table.get(outer).unwrap();
                right_rows = selected_rows_per_table.get(inner).unwrap();
            }

            JoinOperand::Inner(inner) => {
                left_hidden_count = all_rows_hidden_count;
                right_hidden_count = *hidden_selection_per_table.get(inner).unwrap_or(&0);
                all_rows_hidden_count += right_hidden_count;

                left_rows = &current_tables_rows;
                right_rows = selected_rows_per_table.get(inner).unwrap();
            }
        }

        // Don't apply CROSS JOIN if left or right rows are empty
        if join.kind == JoinKind::Cross && (left_rows.is_empty() || right_rows.is_empty()) {
            continue;
        }