Struct DegreeCache 

pub struct DegreeCache { /* private fields */ }

Pre-computed out-degree for every node slot across all relationship types.

Built lazily on first call to Engine::top_k_by_degree or Engine::out_degree by scanning:

1. CSR forward files (checkpointed edges) — contribution per slot from offsets.
2. Delta log records (uncheckpointed edges) — each DeltaRecord.src increments the source slot’s count.

Keyed by the lower-32-bit slot extracted from NodeId.0 (i.e. node_id & 0xFFFF_FFFF).

Lookup is O(1). Engine::top_k_by_degree uses this cache to answer “top-k highest-degree nodes of label L” in O(N log k) where N is the label’s node count (HWM), rather than O(N × E) full edge scans.

Queries that never call top_k_by_degree (e.g. point lookups, scans, hop traversals) pay zero cost: no CSR iteration, no delta-log reads.

Implementations

impl DegreeCache

pub fn out_degree(&self, slot: u64) -> u32

Return the total out-degree for slot across all relationship types.

Returns 0 for slots that have no outgoing edges.

Trait Implementations

impl Debug for DegreeCache

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

Formats the value using the given formatter.

impl Default for DegreeCache

fn default() -> DegreeCache

Returns the “default value” for a type.