Function refine 

pub fn refine(
    idx: &VolumeIndex,
    q: &CompiledQuery,
    opt: &QueryOptions,
    prev_ids: &[EntryId],
) -> (SearchResult, SearchMetrics)

Incremental refinement: when the previous query’s result provably contains the next one’s (subsume.rs) and the index generation is unchanged, filter the cached ids with a complete per-entry evaluation instead of sweeping pools and walking the whole permutation. prev_ids are already in the requested order, so the filtered subsequence is the answer — O(previous hits) instead of O(index).