Function expand_blind

nodedb-vector/src/navix/traversal.rs:401–439

(
    index: &HnswIndex,
    query: &[f32],
    neighbors_1hop: &[u32],
    allowed: &RoaringBitmap,
    ef: usize,
    metric: nodedb_types::vector_distance::DistanceMetric,
    visited: &mut HashSet

/// adding to heaps only IDs that are in `allowed`.
#[allow(clippy::too_many_arguments)]
fn expand_blind(
    index: &HnswIndex,
    query: &[f32],
    neighbors_1hop: &[u32],
    allowed: &RoaringBitmap,
    ef: usize,
    metric: nodedb_types::vector_distance::DistanceMetric,
    visited: &mut HashSet<u32>,
    candidates: &mut BinaryHeap<Reverse<Candidate>>,
    results: &mut BinaryHeap<Candidate>,
) {
    for &nb1 in neighbors_1hop {
        // Mark 1-hop as visited so we do not double-score them later,
        // but do not score them — that is the Blind heuristic.
        visited.insert(nb1);

        for &nb2 in index.neighbors_at(nb1, 0) {
            if !visited.insert(nb2) {
                continue;
            }
            if index.is_deleted(nb2) {
                continue;
            }
            if !allowed.contains(nb2) {
                continue;
            }
            let d = dist(index, query, nb2, metric);
            let nb2_cand = Candidate { dist: d, id: nb2 };
            let worst_dist = results.peek().map_or(f32::INFINITY, |w| w.dist);
            if d < worst_dist || results.len() < ef {
                candidates.push(Reverse(nb2_cand));
            }
            results.push(nb2_cand);
            if results.len() > ef {
                results.pop();
            }
        }
    }
}

/// Inline helper: distance from query to a stored node using the given metric.
#[inline]