Trait StatsSource 

pub trait StatsSource {
    // Required methods
    fn relation_cardinality(&self, rel_id: RelId) -> Option<u64>;
    fn column_ndv(&self, rel_id: RelId, col_idx: usize) -> Option<u64>;
    fn join_selectivity(
        &self,
        left_rel: RelId,
        right_rel: RelId,
        left_col: usize,
        right_col: usize,
    ) -> Option<f64>;
    fn prefix_degree(&self, rel_id: RelId, col_idx: usize) -> Option<(f64, f64)>;
    fn key_heat(&self, rel_id: RelId, col_idx: usize) -> Option<(f64, f64)>;
}

Relation-level statistics required by the full-variable WCOJ planner.

The trait intentionally reads the existing xlog-stats snapshot surface instead of introducing a planner-private stats accumulator. Implementations should return None for missing or unseeded observations so planning can decline incomplete stats without panicking.

Required Methods

fn relation_cardinality(&self, rel_id: RelId) -> Option<u64>

Returns the relation cardinality if it is known and nonzero.

fn column_ndv(&self, rel_id: RelId, col_idx: usize) -> Option<u64>

Returns the distinct-value estimate for a relation column.

fn join_selectivity( &self, left_rel: RelId, right_rel: RelId, left_col: usize, right_col: usize, ) -> Option<f64>

Returns the observed selectivity between two relation columns.

fn prefix_degree(&self, rel_id: RelId, col_idx: usize) -> Option<(f64, f64)>

Returns average and maximum prefix degree for a relation column.

fn key_heat(&self, rel_id: RelId, col_idx: usize) -> Option<(f64, f64)>

Returns heat and skew factor for a relation column.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl StatsSource for StatsSnapshot

fn relation_cardinality(&self, rel_id: RelId) -> Option<u64>

fn column_ndv(&self, rel_id: RelId, col_idx: usize) -> Option<u64>

fn join_selectivity( &self, left_rel: RelId, right_rel: RelId, left_col: usize, right_col: usize, ) -> Option<f64>

fn prefix_degree(&self, rel_id: RelId, col_idx: usize) -> Option<(f64, f64)>

fn key_heat(&self, rel_id: RelId, col_idx: usize) -> Option<(f64, f64)>

Implementors