Struct Relation 

pub struct Relation {
    pub name: String,
    pub arity: usize,
    pub estimated_rows: u64,
    pub bound_columns: BTreeSet<usize>,
}

A relation (predicate) with arity and estimated cardinality.

Fields

name: String

Name of the relation / predicate.

arity: usize

Number of columns (arity).

estimated_rows: u64

Estimated number of rows (tuples).

bound_columns: BTreeSet<usize>

Which columns have known bindings (constants / previously bound variables).

Implementations

impl Relation

pub fn new(name: impl Into<String>, arity: usize, estimated_rows: u64) -> Self

Create a new relation with no bound columns.

pub fn with_binding(self, col: usize) -> Self

Mark a column as bound and return self (builder pattern).

pub fn selectivity(&self) -> f64

Fraction of columns that are bound. Returns 0.0 when arity is 0.

Trait Implementations

impl Clone for Relation

fn clone(&self) -> Relation

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Relation

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

Formats the value using the given formatter.