Module query_stats 

Persistent runtime statistics for online cost-model adaptation.

Each query through the optimizer reports a QueryObservation capturing the family it dispatched to, the wall-clock latency, and the observed recall (if measurable). QueryStats aggregates these observations into per-family running averages and produces recommended_weights that the cost model uses to correct systematic over/underestimates.

Persistence uses serde_json so the file is grep-able for operators; atomic writes go through a temporary .tmp sibling and a rename.

Structs

FamilyStats

Per-family aggregate running statistics.

QueryObservation

Single query observation reported back by the dispatcher after execution.

QueryStats

Aggregated statistics across all index families.