Method valid_index

datafusion/functions-window/src/nth_value.rs:477–515

(&self, array: &ArrayRef, range: &Range<usize>)

impl NthValueEvaluator {
    fn valid_index(&self, array: &ArrayRef, range: &Range<usize>) -> Option<usize> {
        let n_range = range.end - range.start;
        if self.ignore_nulls {
            // Calculate valid indices, inside the window frame boundaries.
            let slice = array.slice(range.start, n_range);
            if let Some(nulls) = slice.nulls()
                && nulls.null_count() > 0
            {
                return self.valid_index_with_nulls(nulls, range.start);
            }
        }
        // Either no nulls, or nulls are regarded as valid rows
        match self.state.kind {
            NthValueKind::First => Some(range.start),
            NthValueKind::Last => Some(range.end - 1),
            NthValueKind::Nth => match self.n.cmp(&0) {
                Ordering::Greater => {
                    // SQL indices are not 0-based.
                    let index = (self.n as usize) - 1;
                    if index >= n_range {
                        // Outside the range, return NULL:
                        None
                    } else {
                        Some(range.start + index)
                    }
                }
                Ordering::Less => {
                    let reverse_index = (-self.n) as usize;
                    if n_range < reverse_index {
                        // Outside the range, return NULL:
                        None
                    } else {
                        Some(range.end - reverse_index)
                    }
                }
                Ordering::Equal => None,
            },
        }
    }

    fn valid_index_with_nulls(&self, nulls: &NullBuffer, offset: usize) -> Option<usize> {
        match self.state.kind {