# Package org.apache.lucene.backward_codecs.lucene90

Lucene 9.0 file format.

- Class Summary
  Class | Description
  --- | ---
  Lucene90Codec | Implements the Lucene 9.0 index format
  Lucene90HnswGraphBuilder | Builder for HNSW graph.
  Lucene90HnswVectorsFormat | Lucene 9.0 vector format, which encodes numeric vector values and an optional associated graph connecting the documents having values.
  Lucene90HnswVectorsReader | Reads vectors from the index segments along with index data structures supporting KNN search.
  Lucene90NeighborArray | NeighborArray encodes the neighbors of a node and their mutual scores in the HNSW graph as a pair of growable arrays.
  Lucene90OnHeapHnswGraph | An `HnswGraph` where all nodes and connections are held in memory.

- Enum Summary
  Enum | Description
  --- | ---
  Lucene90Codec.Mode | Configuration option for the codec.