Trait FtsBackend 

pub trait FtsBackend {
    type Error: Display;

    // Required methods
    fn read_postings(
        &self,
        collection: &str,
        term: &str,
    ) -> Result<Vec<Posting>, Self::Error>;
    fn write_postings(
        &self,
        collection: &str,
        term: &str,
        postings: &[Posting],
    ) -> Result<(), Self::Error>;
    fn remove_postings(
        &self,
        collection: &str,
        term: &str,
    ) -> Result<(), Self::Error>;
    fn read_doc_length(
        &self,
        collection: &str,
        doc_id: &str,
    ) -> Result<Option<u32>, Self::Error>;
    fn write_doc_length(
        &self,
        collection: &str,
        doc_id: &str,
        length: u32,
    ) -> Result<(), Self::Error>;
    fn remove_doc_length(
        &self,
        collection: &str,
        doc_id: &str,
    ) -> Result<(), Self::Error>;
    fn collection_terms(
        &self,
        collection: &str,
    ) -> Result<Vec<String>, Self::Error>;
    fn collection_stats(
        &self,
        collection: &str,
    ) -> Result<(u32, u64), Self::Error>;
    fn increment_stats(
        &self,
        collection: &str,
        doc_len: u32,
    ) -> Result<(), Self::Error>;
    fn decrement_stats(
        &self,
        collection: &str,
        doc_len: u32,
    ) -> Result<(), Self::Error>;
    fn read_meta(&self, key: &str) -> Result<Option<Vec<u8>>, Self::Error>;
    fn write_meta(&self, key: &str, value: &[u8]) -> Result<(), Self::Error>;
    fn write_segment(&self, key: &str, data: &[u8]) -> Result<(), Self::Error>;
    fn read_segment(&self, key: &str) -> Result<Option<Vec<u8>>, Self::Error>;
    fn list_segments(
        &self,
        collection: &str,
    ) -> Result<Vec<String>, Self::Error>;
    fn remove_segment(&self, key: &str) -> Result<(), Self::Error>;
    fn purge_collection(&self, collection: &str) -> Result<usize, Self::Error>;
}

Storage backend abstraction for the full-text search engine.

Origin implements this with redb (persistent). Lite implements with in-memory HashMap. All scoring, BMW, compression, and analysis logic works identically over any backend.

Write methods take &self (not &mut self) because:

• Redb provides transactional isolation internally — concurrent writes are safe through redb’s MVCC.
• MemoryBackend uses interior mutability (RefCell) to match the same trait signature, keeping the trait uniform.

Required Associated Types

type Error: Display

Error type for backend operations.

Required Methods

fn read_postings( &self, collection: &str, term: &str, ) -> Result<Vec<Posting>, Self::Error>

Read the posting list for a term in a collection.

fn write_postings( &self, collection: &str, term: &str, postings: &[Posting], ) -> Result<(), Self::Error>

Write/replace the posting list for a term in a collection.

fn remove_postings( &self, collection: &str, term: &str, ) -> Result<(), Self::Error>

Remove a term’s posting list entirely.

fn read_doc_length( &self, collection: &str, doc_id: &str, ) -> Result<Option<u32>, Self::Error>

Read the document length (token count) for a document.

fn write_doc_length( &self, collection: &str, doc_id: &str, length: u32, ) -> Result<(), Self::Error>

Write/replace the document length for a document.

fn remove_doc_length( &self, collection: &str, doc_id: &str, ) -> Result<(), Self::Error>

Remove a document’s length entry.

fn collection_terms(&self, collection: &str) -> Result<Vec<String>, Self::Error>

Get all term keys for a collection (for fuzzy matching). Returns terms without the collection prefix.

fn collection_stats(&self, collection: &str) -> Result<(u32, u64), Self::Error>

Get total document count and sum of all document lengths for a collection. Returns (doc_count, total_token_sum).

Implementations should maintain these incrementally for O(1) lookup.

fn increment_stats( &self, collection: &str, doc_len: u32, ) -> Result<(), Self::Error>

Increment collection stats after indexing a document. doc_len is the number of tokens in the newly indexed document.

fn decrement_stats( &self, collection: &str, doc_len: u32, ) -> Result<(), Self::Error>

Decrement collection stats after removing a document. doc_len is the token count of the removed document.

fn read_meta(&self, key: &str) -> Result<Option<Vec<u8>>, Self::Error>

Read a metadata blob by key (e.g., “docmap:{collection}”, “fieldnorms:{collection}”).

fn write_meta(&self, key: &str, value: &[u8]) -> Result<(), Self::Error>

Write a metadata blob by key.

fn write_segment(&self, key: &str, data: &[u8]) -> Result<(), Self::Error>

Write a segment blob. Key format: “{collection}:seg:{segment_id}”.

fn read_segment(&self, key: &str) -> Result<Option<Vec<u8>>, Self::Error>

Read a segment blob. Returns None if not found.

fn list_segments(&self, collection: &str) -> Result<Vec<String>, Self::Error>

List all segment keys for a collection (prefix “{collection}:seg:”).

fn remove_segment(&self, key: &str) -> Result<(), Self::Error>

Remove a segment blob.

fn purge_collection(&self, collection: &str) -> Result<usize, Self::Error>

Remove all entries for a collection prefix. Returns count of removed entries.

Implementors

impl FtsBackend for MemoryBackend

type Error = MemoryError