Function spawn_series_index_tasks 

pub(crate) fn spawn_series_index_tasks(
    worker_id: u32,
    store: ObjectStore,
    regions: Arc<RegionMap>,
    state: Arc<SeriesIndexTaskState>,
    receiver: Receiver<SeriesIndexCommand>,
    bucket_width: Duration,
    purger: IndexFilePurger,
    purge_receiver: UnboundedReceiver<PurgeRequest>,
    disk_usage: Arc<AtomicU64>,
    max_size: u64,
    interval: Duration,
    time_provider: Arc<dyn TimeProvider>,
    enable_range_index: bool,
) -> JoinHandle<()>

Starts both tasks on the compaction runtime, detaching purge and returning the maintenance handle.