Struct HybridBackend 

pub struct HybridBackend { /* private fields */ }

Hybrid vector backend combining HNSW (hot) + DiskANN (cold).

Data flow

• Insert: vector goes to DiskANN (always) and HNSW (if under hot capacity).
• Search: query both tiers, fuse ranks via Reciprocal Rank Fusion (RRF; WEFT-661), deduplicate by numeric ID.
• Promotion: access counts are tracked per ID. When a cold-only vector exceeds promotion_threshold accesses, it is copied into the hot tier.
• Eviction: when HNSW exceeds hot_capacity, the LRU entry is evicted (it remains in DiskANN).

Implementations

impl HybridBackend

pub fn new( hnsw_config: HnswServiceConfig, diskann_config: DiskAnnConfig, hybrid_config: HybridConfig, ) -> Self

Create a new hybrid backend.

pub fn with_defaults() -> Self

Create with all-default configurations.

pub fn config(&self) -> &HybridConfig

Borrow the hybrid configuration.

pub fn hot_len(&self) -> usize

Return the number of vectors in the hot tier.

pub fn cold_len(&self) -> usize

Return the number of vectors in the cold tier.

Trait Implementations

impl Debug for HybridBackend

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl VectorBackend for HybridBackend

fn insert( &self, id: u64, key: &str, vector: &[f32], metadata: Value, ) -> VectorResult<()>

Insert a vector with the given numeric ID, string key, and metadata.

fn search(&self, query: &[f32], k: usize) -> Vec<SearchResult>

Search for the k nearest vectors to query.

fn len(&self) -> usize

Return the number of vectors currently stored.

fn contains(&self, id: u64) -> bool

Check whether a vector with the given ID exists.

fn remove(&self, id: u64) -> bool

Remove a vector by ID. Returns true if it was present.

fn flush(&self) -> VectorResult<()>

Persist any in-memory state to durable storage.

fn backend_name(&self) -> &str

Return a human-readable name for this backend (e.g. “hnsw”, “diskann”, “hybrid”).

fn current_epoch(&self) -> u64

Return the current monotonic epoch.

fn insert_with_epoch( &self, id: u64, key: &str, vector: &[f32], metadata: Value, parent_epoch: u64, ) -> VectorResult<()>

Insert a vector only if the store’s current epoch matches parent_epoch. If the epoch has advanced past parent_epoch, the call is rejected with VectorError::EpochConflict.

fn soft_delete(&self, id: u64) -> bool

Mark a vector as tombstoned instead of physically removing it.

fn compact(&self, older_than_epoch: u64) -> usize

Physically remove tombstones whose deletion epoch is older than older_than_epoch. Returns the number of entries purged.

fn tombstone_count(&self) -> usize

Return the number of tombstoned (soft-deleted) entries.

fn max_vectors(&self) -> Option<usize>

Return the configured maximum number of vectors, or None if unbounded.

fn set_max_vectors(&self, limit: Option<usize>)

Set the maximum number of vectors. Pass None for unbounded.

fn is_empty(&self) -> bool

Return true if the store contains no vectors.