Rustでデータベースを設計しよう3(update, delete)

### column名とvalueを指定してupdate

    fn update_value_by_column_condition(
        &mut self,
        where_column: &str,
        where_value: &Value,
        set_column: &str,
        new_value: Value,
    ) -> Result<usize, String> {
        let where_index = self.columns.columns.iter().position(|c| c.name == where_column)
            .ok_or_else(|| format!("Column '{}' not found", where_column))?;

        let set_index = self.columns.columns.iter().position(|c| c.name == set_column)
            .ok_or_else(|| format!("Column '{}' not found", set_column))?;

        let expected_type = &self.columns.columns[set_index].constraint;
        if !type_matches(&new_value, expected_type) {
            return Err(format!(
                "Type mismatch: column '{}' expects {:?}, got {:?}",
                set_column, expected_type, new_value
            ));
        }

        let mut updated = 0;
        for row in self.rows.iter_mut() {
            if let Some(v) = row.get(where_index) {
                if v == where_value {
                    row[set_index] = new_value.clone();
                    updated += 1;
                }
            }
        }

        Ok(updated)
    }

    let result = table.insert_row(vec![
        Value::Integer(2),
        Value::Text("Bob".to_string()),
        Value::Integer(25),
    ]);
    println!("{:?}", table);

    let _ = table.update_value_by_column_condition(
        "id",
        &Value::Integer(2),
        "name",
        Value::Text("Carol".to_string()),
    );

    let matching_rows = table.find_rows_by_column_value("id", &Value::Integer(2));

    for row in matching_rows {
        println!("Matched row: {:?}", row);
    }

Matched row: [Integer(2), Text(“Carol”), Integer(25)]

### delete

    fn delete_rows_by_column_value(
        &mut self,
        column_name: &str,
        target: &Value,
    ) -> Result<usize, String> {
        let col_index = self
            .columns
            .columns
            .iter()
            .position(|col| col.name == column_name)
            .ok_or_else(|| format!("Column '{}' not found", column_name))?;

        let original_len = self.rows.len();

        self.rows.retain(|row| row.get(col_index) != Some(target));

        Ok(original_len - self.rows.len())
    }

    let matching_rows = table.find_rows_by_column_value("id", &Value::Integer(2));

    for row in matching_rows {
        println!("Matched row: {:?}", row);
    }

    let _ = table.delete_rows_by_column_value("id", &Value::Integer(2));
    println!("{:?}", table);

Matched row: [Integer(2), Text(“Carol”), Integer(25)]
Table { name: “users”, columns: Columns { columns: [Column { name: “id”, constraint: Integer }, Column { name: “name”, constraint: Text }, Column { name: “age”, constraint: Integer }] }, rows: [[Integer(1), Text(“Alice”), Integer(30)]] }

これで、一通りcreate, insert, select, update, deleteまではできた。
ここから改善していく。