Struct MetadataStore

pub struct MetadataStore {
    entries: Vec<HashMap<String, String>>,
    inverted: HashMap<String, HashMap<String, RoaringBitmap>>,
}

Dense metadata store with inverted index for O(1) pre-filtering.

Two data structures:

• entries: node_id → metadata map (for retrieval)
• inverted: key → value → RoaringBitmap of node_ids (for filtering)

The inverted index supports exact-match pre-filtering during HNSW traversal, replacing the O(4k) post-filter with O(1) bitmap lookups.

Fields

entries: Vec<HashMap<String, String>>

node_id → metadata. Empty HashMap for nodes without metadata.

inverted: HashMap<String, HashMap<String, RoaringBitmap>>

Inverted index: key → value → bitmap of matching node_ids. Only populated for exact string values (not numeric ranges).

Implementations

impl MetadataStore

pub fn new() -> Self

Create an empty store.

pub fn push(&mut self, metadata: HashMap<String, String>)

Register metadata for a new node (must be called in order).

pub fn push_empty(&mut self)

Register an empty metadata entry.

pub fn get(&self, node_id: u32) -> &HashMap<String, String>

Get metadata for a node.

pub fn matches(&self, node_id: u32, filter: &MetadataFilter) -> bool

Check if a node passes a metadata filter.

pub fn build_filter_bitmap(&self, filter: &MetadataFilter) -> RoaringBitmap

Build a RoaringBitmap of node_ids matching the metadata filter.

For Equals predicates: uses the inverted index for O(1) lookup. For other predicates (Gte, Lte, Contains, Exists): falls back to scanning entries.

Multiple predicates are AND-combined (intersection).

pub fn filter_results( &self, results: &[(u32, f32)], filter: &MetadataFilter, ) -> Vec<(u32, f32)>

Filter a list of (node_id, score) results by metadata.

pub fn len(&self) -> usize

Number of entries.

pub fn is_empty(&self) -> bool

Whether empty.

Trait Implementations

impl Clone for MetadataStore

fn clone(&self) -> MetadataStore

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for MetadataStore

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

Formats the value using the given formatter.

impl Default for MetadataStore

fn default() -> MetadataStore

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for MetadataStore

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for MetadataStore

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

where __S: Serializer,

Serialize this value into the given Serde serializer.