Struct RuntimeFeedbackStore 

pub struct RuntimeFeedbackStore { /* private fields */ }

Persistent store of historical query execution statistics.

Keeps at most max_history entries per query hash.

Implementations

impl RuntimeFeedbackStore

pub fn new(max_history: usize) -> Self

Create a new store that retains up to max_history records per query.

pub fn record(&mut self, stats: QueryStats)

Record a new execution statistics entry.

If the per-query history is already at capacity the oldest entry is dropped before the new one is appended.

pub fn get_stats(&self, query_hash: u64) -> &[QueryStats]

Return the recorded history for a query, or an empty slice when none exists.

pub fn estimate_selectivity(&self, pattern: &str) -> f64

Estimate the selectivity of a triple-pattern string from historical data.

Averages the per-pattern selectivity across all historical entries that contain an observation for pattern. Returns 0.1 as a default when no data is available.

pub fn estimate_cardinality(&self, pattern: &str, base_estimate: usize) -> usize

Estimate cardinality for a pattern given a base estimate.

Adjusts base_estimate using the average observed selectivity. Falls back to base_estimate when no historical data exists (since default selectivity 0.1 / 0.1 = ratio 1.0).

pub fn best_join_order(&self, query_hash: u64) -> Option<Vec<String>>

Return the join order associated with the lowest average execution time for a given query hash, or None when no history exists.

pub fn prune_old(&mut self, max_age_ms: u64)

Remove all statistics entries where execution_time_ms >= max_age_ms.

Entries with execution time below max_age_ms are retained. Empty query buckets are also removed.

pub fn stats_count(&self) -> usize

Total number of statistics entries across all queries.

pub fn query_count(&self) -> usize

Number of distinct query hashes for which history has been recorded.

Trait Implementations

impl Default for RuntimeFeedbackStore

fn default() -> Self

Returns the “default value” for a type.