Enum CandidateCount 

pub enum CandidateCount {
    Exact(usize),
    AtLeast(usize),
}

What the counting probe learned about the candidate set.

The distinction is the point: SQLite has no histograms and sqlite_stat1 carries average rows-per-key, which estimates an equality predicate and not multi-hop reachability. So the count is measured, by running the traversal under a cap — and a probe that hits its cap has not measured anything except that the set is too big to care about the exact size.

Variants

Exact(usize)

The traversal returned this many ids, below the cap.

AtLeast(usize)

The probe hit its cap. The true count is at least this.

Implementations

impl CandidateCount

pub fn lower_bound(self) -> usize

The number to compute with. For a capped probe this understates the true count, which is the safe direction: it makes PreFilterCTE look cheaper than it is, and PreFilterCTE is the exact strategy.

pub fn is_capped(self) -> bool

Trait Implementations

impl Clone for CandidateCount

fn clone(&self) -> CandidateCount

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CandidateCount

impl Debug for CandidateCount

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

Formats the value using the given formatter.

impl Eq for CandidateCount

impl PartialEq for CandidateCount

fn eq(&self, other: &CandidateCount) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for CandidateCount