Function compute_sort_order

nodedb/src/engine/timeseries/projection.rs:29–50

Sort indices for a projection. Returns a permutation vector: `result[i]` is the original row index that should appear at position `i` in the sorted output.

(
    drain: &ColumnarDrainResult,
    sort_columns: &[usize],
    ascending: &[bool],
)

/// Returns a permutation vector: `result[i]` is the original row index
/// that should appear at position `i` in the sorted output.
pub fn compute_sort_order(
    drain: &ColumnarDrainResult,
    sort_columns: &[usize],
    ascending: &[bool],
) -> Vec<usize> {
    let row_count = drain.row_count as usize;
    let mut indices: Vec<usize> = (0..row_count).collect();

    indices.sort_by(|&a, &b| {
        for (i, &col_idx) in sort_columns.iter().enumerate() {
            let asc = ascending.get(i).copied().unwrap_or(true);
            let ord = compare_column_values(&drain.columns[col_idx], a, b);
            let ord = if asc { ord } else { ord.reverse() };
            if ord != std::cmp::Ordering::Equal {
                return ord;
            }
        }
        std::cmp::Ordering::Equal
    });

    indices
}

/// Apply a permutation to reorder column data.
pub fn apply_permutation(data: &ColumnData, perm: &[usize]) -> ColumnData {