Function mz_storage_controller::collection_mgmt::partially_truncate_status_history

pub(crate) async fn partially_truncate_status_history<T, K>(
    id: GlobalId,
    introspection_type: IntrospectionType,
    write_handle: &mut WriteHandle<SourceData, (), T, Diff>,
    status_history_desc: StatusHistoryDesc<K>,
    now: NowFn,
    storage_collections: &Arc<dyn StorageCollections<Timestamp = T> + Send + Sync>,
    txns_read: &TxnsRead<T>,
    persist: &Arc<PersistClientCache>,
) -> BTreeMap<K, Row>
where
    T: Codec64 + From<EpochMillis> + TimestampManipulation,
    K: Clone + Debug + Ord + Send + Sync,

Effectively truncates the status history shard based on its retention policy.

NOTE: The history collections are really append-only collections, but every-now-and-then we want to retract old updates so that the collection does not grow unboundedly. Crucially, these are not incremental collections, they are not derived from a state at some time t and we cannot maintain a desired state for them.

Returns a map with latest unpacked row per key.