Enum FusionStrategy 

pub enum FusionStrategy {
    Rrf {
        k: usize,
    },
    Weighted {
        weights: Vec<f64>,
    },
    Union,
    VectorOnly,
    KeywordOnly,
}

Fusion strategy for combining ranked result lists.

See module-level docs for algorithm details.

Variants

Rrf

Reciprocal Rank Fusion (default, recommended).

Uses only ranks, making it robust to different score distributions. Formula: score(d) = Σ 1/(k + rank_i(d))

Fields

k: usize

Smoothing constant. Higher values reduce impact of rank differences. Default: 60 (standard in literature).

Weighted

Weighted linear combination of scores.

Requires score normalization for different score scales (e.g., vector similarity 0-1 vs BM25 0-∞).

Weights are normalized to sum to 1.0 internally.

Fields

weights: Vec<f64>

Weights for each source (will be normalized).

Union

Take union with max score per ID.

Useful when you want the best score from any source.

VectorOnly

Skip BM25 entirely — return only vector (HNSW) results.

Use when keyword search degrades quality (short queries, code search). The result list is the raw HNSW output with no fusion step.

KeywordOnly

Skip HNSW entirely — return only BM25 keyword results.

Use for exact-match retrieval (medication names, identifiers, slugs). The result list is the raw BM25 output with no fusion step.

Implementations

impl FusionStrategy

pub fn rrf() -> FusionStrategy

Create an RRF strategy with default k=60.

pub fn rrf_with_k(k: usize) -> FusionStrategy

Create an RRF strategy with custom k value.

pub fn weighted(weights: Vec<f64>) -> FusionStrategy

Create a weighted strategy with given weights.

pub fn union() -> FusionStrategy

Create a union strategy.

Trait Implementations

impl Clone for FusionStrategy

fn clone(&self) -> FusionStrategy

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FusionStrategy

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

Formats the value using the given formatter.

impl Default for FusionStrategy

fn default() -> FusionStrategy

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for FusionStrategy

fn deserialize<__D>( __deserializer: __D, ) -> Result<FusionStrategy, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for FusionStrategy

fn eq(&self, other: &FusionStrategy) -> 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 Serialize for FusionStrategy

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for FusionStrategy