Function compare_coverage_rows_causal 

pub fn compare_coverage_rows_causal(
    left: &CatalogCoverageRow,
    right: &CatalogCoverageRow,
) -> Ordering

Orders coverage rows causally. data_version is a monotonic ordering token derived from the writer’s base snapshot, not a snapshot handle; rows written before versioning existed carry None and order as version 0, which is correct because every versioned row postdates them. Ties (including compacted rows sharing one version) fall back to the creation timestamp, keeping the order total and transitive on mixed catalogs.