Struct RdfStatistics 

pub struct RdfStatistics {
    pub total_triples: u64,
    pub subject_count: u64,
    pub predicate_count: u64,
    pub object_count: u64,
    pub predicates: HashMap<String, PredicateStatistics>,
    pub subject_histogram: Option<Histogram>,
    pub object_histogram: Option<Histogram>,
    pub index_stats: IndexStatistics,
}

Statistics for an RDF triple store.

Fields

total_triples: u64

Total number of triples.

subject_count: u64

Number of unique subjects.

predicate_count: u64

Number of unique predicates.

object_count: u64

Number of unique objects.

predicates: HashMap<String, PredicateStatistics>

Per-predicate statistics.

subject_histogram: Option<Histogram>

Subject frequency histogram (for join selectivity).

object_histogram: Option<Histogram>

Object frequency histogram.

index_stats: IndexStatistics

Index access pattern statistics (for cost model).

Implementations

impl RdfStatistics

pub fn new() -> Self

Creates new empty RDF statistics.

pub fn update_from_counts( &mut self, total_triples: u64, subject_count: u64, predicate_count: u64, object_count: u64, )

Updates statistics from an RDF store.

pub fn update_predicate(&mut self, predicate: &str, stats: PredicateStatistics)

Adds or updates predicate statistics.

pub fn get_predicate(&self, predicate: &str) -> Option<&PredicateStatistics>

Gets predicate statistics.

pub fn estimate_triple_pattern_cardinality( &self, subject_bound: bool, predicate_bound: Option<&str>, object_bound: bool, ) -> f64

Estimates cardinality for a triple pattern.

Arguments

• subject_bound - Whether the subject is a constant
• predicate_bound - Whether the predicate is a constant (and its value if so)
• object_bound - Whether the object is a constant

pub fn estimate_join_selectivity( &self, var_position1: TriplePosition, var_position2: TriplePosition, ) -> f64

Estimates join selectivity between two patterns sharing a variable.

pub fn estimate_filter_selectivity(&self, predicate_iri: Option<&str>) -> f64

Estimates the cardinality after a FILTER operation.

Trait Implementations

impl Clone for RdfStatistics

fn clone(&self) -> RdfStatistics

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for RdfStatistics

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

Formats the value using the given formatter.

impl Default for RdfStatistics

fn default() -> RdfStatistics

Returns the “default value” for a type.