Method regularize_order_bys

datafusion/expr/src/window_frame.rs:249–272

Regularizes the ORDER BY clause of the window frame.

(&self, order_by: &mut Vec<Sort>)

    /// Regularizes the ORDER BY clause of the window frame.
    pub fn regularize_order_bys(&self, order_by: &mut Vec<Sort>) -> Result<()> {
        match self.units {
            // Normally, RANGE frames require an ORDER BY clause with exactly
            // one column. However, an ORDER BY clause may be absent or have
            // more than one column when the start/end bounds are UNBOUNDED or
            // CURRENT ROW.
            WindowFrameUnits::Range if self.free_range() && order_by.is_empty() => {
                // If an ORDER BY clause is absent, it is equivalent to an
                // ORDER BY clause with constant value as sort key. If an
                // ORDER BY clause is present but has more than one column,
                // it is unchanged. Note that this follows PostgreSQL behavior.
                order_by.push(lit(1u64).sort(true, false));
            }
            WindowFrameUnits::Range if self.free_range() => {}
            WindowFrameUnits::Range if order_by.len() != 1 => {
                return plan_err!("RANGE requires exactly one ORDER BY column");
            }
            WindowFrameUnits::Groups if order_by.is_empty() => {
                return plan_err!("GROUPS requires an ORDER BY clause");
            }
            _ => {}
        }
        Ok(())
    }

    /// Returns whether the window frame can accept multiple ORDER BY expressions.
    pub fn can_accept_multi_orderby(&self) -> bool {