Struct IndexStatistics 

pub struct IndexStatistics {
    pub spo_lookup_cost: f64,
    pub pos_lookup_cost: f64,
    pub osp_lookup_cost: f64,
    pub has_osp_index: bool,
}

Cost estimates for different index access patterns.

RDF stores typically have multiple indexes (SPO, POS, OSP). This tracks how expensive each one is to use, so the optimizer can pick the cheapest.

Fields

spo_lookup_cost: f64

Average cost of SPO index lookup (subject first).

pos_lookup_cost: f64

Average cost of POS index lookup (predicate first).

osp_lookup_cost: f64

Average cost of OSP index lookup (object first).

has_osp_index: bool

Whether OSP index is available.

Implementations

impl IndexStatistics

pub fn new() -> Self

Creates default index statistics.

pub fn estimate_pattern_cost( &self, subject_bound: bool, predicate_bound: bool, object_bound: bool, ) -> f64

Estimates the cost of executing a triple pattern.

Trait Implementations

impl Clone for IndexStatistics

fn clone(&self) -> IndexStatistics

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for IndexStatistics

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

Formats the value using the given formatter.

impl Default for IndexStatistics

fn default() -> IndexStatistics

Returns the “default value” for a type.