use Duration;
/// A ring query: find all vectors whose Euclidean distance to `query`
/// lies within `[d - lambda, d + lambda]`.
///
/// Internally, ringdb uses squared L2 distances to avoid computing square
/// roots. The ring bounds become:
///
/// ```text
/// lower_sq = max(0, d - lambda)²
/// upper_sq = (d + lambda)²
/// ```
/// Result of a ring query.