Struct HeatAwareLeaderModel 

pub struct HeatAwareLeaderModel;

Heat-aware cost model: combines cardinality, access heat, and observed join selectivity into a fixed composite score formula. Higher score = more expensive to iterate over → demote from the leader (slot 0). The model picks argmin(score) as leader, gated by the same effective_wcoj_var_ordering_threshold as the leader-cardinality model.

Composite score formula:

score(rel) = cardinality(rel)
           * (1.0 + 4.0 * heat(rel))
           * Σ_{e ∈ edges(rel)} 1.0 / max(0.01, observed_sel_or_one(e))

• cardinality from StatsManager::get_relation_stats(rel).cardinality.
• heat from RelationStats.heat: f32 (EMA written by record_access at node_dispatch.rs:26).
• observed_sel_or_one(e) from StatsManager::get_join_selectivity(rel_a, rel_b) (join-result feedback via record_join_result, EMA-smoothed). Key-validation: only consume a cached JoinSelectivity when its (left_keys, right_keys) match the candidate edge keys after StatsManager::canonical_join_key swap. On mismatch, default to 1.0 (no observed filter assumption).

Heat weight 4.0: with default threshold 0.5, gate fires when min/default ≤ 0.5. With cards equal + heat = h on the hot rel, ratio = 1 / (1 + 4h). For 1 + 4h ≥ 2.0 → h ≥ 0.25 (~3 record_access calls).

Implementations

impl HeatAwareLeaderModel

pub const HEAT_WEIGHT: f32 = 4.0

Heat weight used by the composite score formula.

pub const NO_OBSERVED_SEL: f64 = 1.0

Default selectivity for an edge with no observed JoinSelectivity record (or with mismatched keys).

pub const SEL_FLOOR: f64 = 0.01

Floor used in 1/max(0.01, sel) to avoid divide-by-zero on tightly observed edges.

Trait Implementations

impl Clone for HeatAwareLeaderModel

fn clone(&self) -> HeatAwareLeaderModel

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for HeatAwareLeaderModel

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

Formats the value using the given formatter.

impl Default for HeatAwareLeaderModel

fn default() -> HeatAwareLeaderModel

Returns the “default value” for a type.

impl WcojVariableOrderingModel for HeatAwareLeaderModel

fn pick_triangle_leader( &self, rel_ids: [RelId; 3], stats: &StatsManager, config: &CompilerConfig, ) -> Option<u8>

Pick a leader for the triangle WCOJ shape.

fn pick_4cycle_leader( &self, rel_ids: [RelId; 4], stats: &StatsManager, config: &CompilerConfig, ) -> Option<u8>

Pick a leader for the 4-cycle WCOJ shape.

impl Copy for HeatAwareLeaderModel