Struct Histogram 

pub struct Histogram { /* private fields */ }

An equi-depth histogram.

Each bucket contains approximately the same number of rows.

Implementations

impl Histogram

pub fn new(buckets: Vec<HistogramBucket>) -> Self

Creates a new histogram with the given buckets.

pub fn build(sorted_values: &[Value], num_buckets: usize) -> Self

Creates an equi-depth histogram from sorted values.

Arguments

• sorted_values - Values sorted in ascending order.
• num_buckets - Target number of buckets.

pub fn bucket_count(&self) -> usize

Returns the number of buckets.

pub fn buckets(&self) -> &[HistogramBucket]

Returns the buckets.

pub fn total_rows(&self) -> u64

Returns the total row count.

pub fn total_distinct(&self) -> u64

Returns the total distinct count.

pub fn estimate_equality_selectivity(&self, value: &Value) -> f64

Estimates the selectivity of an equality predicate.

Returns the estimated fraction of rows that match the value.

pub fn estimate_range_selectivity( &self, lower: Option<&Value>, upper: Option<&Value>, lower_inclusive: bool, upper_inclusive: bool, ) -> f64

Estimates the selectivity of a range predicate.

Arguments

• lower - Lower bound (None for unbounded).
• upper - Upper bound (None for unbounded).
• lower_inclusive - Whether lower bound is inclusive.
• upper_inclusive - Whether upper bound is inclusive.

pub fn estimate_less_than_selectivity( &self, value: &Value, inclusive: bool, ) -> f64

Estimates the selectivity of a less-than predicate.

pub fn estimate_greater_than_selectivity( &self, value: &Value, inclusive: bool, ) -> f64

Estimates the selectivity of a greater-than predicate.

Trait Implementations

impl Clone for Histogram

fn clone(&self) -> Histogram

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Histogram

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

Formats the value using the given formatter.