Struct PresenceFilter 

pub struct PresenceFilter<Src: BlockMetadata, Dst: BlockMetadata> { /* private fields */ }

G1→G2 filter: skip blocks already present in destination tier.

Uses BlockRegistry::check_presence to determine if a block exists in the destination tier without acquiring a full block reference. This is efficient because it only checks the registry metadata.

Duplicate Prevention

When a PendingTracker is configured, this filter also checks for blocks that are currently in-flight through the pipeline. This prevents duplicate transfers when overlapping sequences are enqueued at roughly the same time.

Performance

This policy is fully synchronous and returns Either::Left(Ready), avoiding any heap allocation per evaluation.

Example

let tracker = Arc::new(PendingTracker::new());
let filter = PresenceFilter::<G1, G2>::new(registry.clone())
    .with_pending_tracker(tracker);
// Blocks already in G2 OR in-flight will be filtered out

Implementations

impl<Src: BlockMetadata, Dst: BlockMetadata> PresenceFilter<Src, Dst>

pub fn new(registry: Arc<BlockRegistry>) -> Self

Create a new presence filter without pending tracking.

pub fn with_pending_tracker(self, tracker: Arc<PendingTracker>) -> Self

Add a pending tracker for duplicate prevention.

When set, blocks that are currently in-flight (passed policy but not yet registered in destination) will be filtered out.

pub fn pending_tracker(&self) -> Option<&Arc<PendingTracker>>

Get a reference to the pending tracker if configured.

Trait Implementations

impl<Src: BlockMetadata, Dst: BlockMetadata> OffloadPolicy<Src> for PresenceFilter<Src, Dst>

fn name(&self) -> &str

Unique name for this policy (for logging/debugging).

fn evaluate<'a>(&'a self, ctx: &'a EvalContext<Src>) -> PolicyFuture<'a>

Evaluate whether a block should be offloaded.

fn evaluate_batch<'a>( &'a self, contexts: &'a [EvalContext<Src>], ) -> PolicyBatchFuture<'a>

Batch evaluate multiple blocks.