Function apply_lead

nodedb-query/src/window/offset.rs:59–76

(
    rows: &mut [(String, serde_json::Value)],
    indices: &[usize],
    spec: &WindowFuncSpec,
)

}

pub(super) fn apply_lead(
    rows: &mut [(String, serde_json::Value)],
    indices: &[usize],
    spec: &WindowFuncSpec,
) {
    let field = col_arg(spec, 0);
    let offset = usize_arg(spec, 1, 1);
    let default = default_arg(spec, 2);

    for (pos, &i) in indices.iter().enumerate() {
        let val = if pos + offset < indices.len() {
            get_field(&rows[indices[pos + offset]].1, field)
        } else {
            default.clone()
        };
        set_window_col(&mut rows[i].1, &spec.alias, val);
    }
}

/// PostgreSQL `nth_value(expr, n)` — value of `expr` at the n'th row of the
/// window frame, NULL if the frame doesn't yet contain n rows. Default frame