Enum DistanceMetric 

pub enum DistanceMetric {
    L2,
    Cosine,
    Dot,
}

Distance metric used by the HNSW index. Must match what the surrounding vec_distance_* SQL function would compute on the same pair of vectors — otherwise the index probe and the brute-force fallback would disagree on which rows are “nearest”. See src/sql/executor.rs’s vec_distance_l2 / _cosine / _dot for the canonical implementations.

Variants

L2

Cosine

Dot

Implementations

impl DistanceMetric

pub fn from_sql_name(name: &str) -> Option<Self>

Parses the metric name from the CREATE INDEX … WITH (metric = '<name>') clause. Case-insensitive. Returns None for unknown values; the parser surfaces that as a user-visible error so a typo doesn’t silently fall back to L2.

pub fn sql_name(self) -> &'static str

The canonical SQL-surface name for this metric. Used when synthesizing CREATE INDEX SQL back into sqlrite_master.

pub fn matching_distance_fn(self) -> &'static str

The vec_distance_* SQL function whose result this metric orders by. The optimizer’s HNSW shortcut only fires when the query’s ORDER BY expression names this exact function.

pub fn compute(self, a: &[f32], b: &[f32]) -> f32

Computes the configured distance between two equal-dimension vectors. Returns f32::INFINITY for the cosine/zero-magnitude edge case; HNSW treats infinity as “worst possible candidate” and will prefer any finite alternative, which matches the SQL-level behaviour where vec_distance_cosine errors but the optimizer’s fallback path simply skips the offending row.

Trait Implementations

impl Clone for DistanceMetric

fn clone(&self) -> DistanceMetric

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for DistanceMetric

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

Formats the value using the given formatter.

impl PartialEq for DistanceMetric

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for DistanceMetric

impl Eq for DistanceMetric

impl StructuralPartialEq for DistanceMetric