Function compare_columns

src/expr/src/relation.rs:3835–3874

Compare `left` and `right` using `order`. If that doesn't produce a strict ordering, call `tiebreaker`.

(
    order: &[ColumnOrder],
    left: &[Datum],
    right: &[Datum],
    tiebreaker: F,
)

/// Compare `left` and `right` using `order`. If that doesn't produce a strict
/// ordering, call `tiebreaker`.
pub fn compare_columns<F>(
    order: &[ColumnOrder],
    left: &[Datum],
    right: &[Datum],
    tiebreaker: F,
) -> Ordering
where
    F: Fn() -> Ordering,
{
    for order in order {
        let cmp = match (&left[order.column], &right[order.column]) {
            (Datum::Null, Datum::Null) => Ordering::Equal,
            (Datum::Null, _) => {
                if order.nulls_last {
                    Ordering::Greater
                } else {
                    Ordering::Less
                }
            }
            (_, Datum::Null) => {
                if order.nulls_last {
                    Ordering::Less
                } else {
                    Ordering::Greater
                }
            }
            (lval, rval) => {
                if order.desc {
                    rval.cmp(lval)
                } else {
                    lval.cmp(rval)
                }
            }
        };
        if cmp != Ordering::Equal {
            return cmp;
        }
    }
    tiebreaker()
}

/// Describe a window frame, e.g. `RANGE UNBOUNDED PRECEDING` or
/// `ROWS BETWEEN 5 PRECEDING AND CURRENT ROW`.