Package org.apache.lucene.codecs.lucene99

# Class Lucene99HnswScalarQuantizedVectorsFormat

java.lang.Object
org.apache.lucene.codecs.KnnVectorsFormat
org.apache.lucene.codecs.lucene99.Lucene99HnswScalarQuantizedVectorsFormat

All Implemented Interfaces:
  `NamedSPILoader.NamedSPI`

public class Lucene99HnswScalarQuantizedVectorsFormat extends KnnVectorsFormat
Lucene 9.9 vector format, which encodes numeric vector values into an associated graph connecting the documents having values. The graph is used to power HNSW search. The format consists of two files, and uses `Lucene99ScalarQuantizedVectorsFormat` to store the actual vectors: For details on graph storage and file extensions, see `Lucene99HnswVectorsFormat`.

WARNING: This API is experimental and might change in incompatible ways in the next release.

## Field Summary

Fields
Modifier and Type
Field
Description
`static final String`
`NAME`

### Fields inherited from class org.apache.lucene.codecs.KnnVectorsFormat

`DEFAULT_MAX_DIMENSIONS, EMPTY`

## Constructor Summary

Constructors
Constructor
Description
`Lucene99HnswScalarQuantizedVectorsFormat()`
Constructs a format using default graph construction parameters with 7 bit quantization
`Lucene99HnswScalarQuantizedVectorsFormat(int maxConn, int beamWidth)`
Constructs a format using the given graph construction parameters with 7 bit quantization
`Lucene99HnswScalarQuantizedVectorsFormat(int maxConn, int beamWidth, int numMergeWorkers, int bits, boolean compress, Float confidenceInterval, ExecutorService mergeExec)`
Constructs a format using the given graph construction parameters and scalar quantization.

## Method Summary

Modifier and Type
Method
Description
`KnnVectorsReader`
`fieldsReader(SegmentReadState state)`
Returns a `KnnVectorsReader` to read the vectors from the index.
`KnnVectorsWriter`
`fieldsWriter(SegmentWriteState state)`
Returns a `KnnVectorsWriter` to write the vectors to the index.
`int`
`getMaxDimensions(String fieldName)`
Returns the maximum number of vector dimensions supported by this codec for the given field name
`String`
`toString()`

### Methods inherited from class org.apache.lucene.codecs.KnnVectorsFormat

`availableKnnVectorsFormats, forName, getName, reloadKnnVectorsFormat`

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

## Field Details

### NAME

public static final String NAME

See Also:
  - Constant Field Values

## Constructor Details

### Lucene99HnswScalarQuantizedVectorsFormat

public Lucene99HnswScalarQuantizedVectorsFormat()
Constructs a format using default graph construction parameters with 7 bit quantization

### Lucene99HnswScalarQuantizedVectorsFormat

public Lucene99HnswScalarQuantizedVectorsFormat(int maxConn, int beamWidth)
Constructs a format using the given graph construction parameters with 7 bit quantization

Parameters:
  `maxConn` - the maximum number of connections to a node in the HNSW graph
  `beamWidth` - the size of the queue maintained during graph construction.

### Lucene99HnswScalarQuantizedVectorsFormat

public Lucene99HnswScalarQuantizedVectorsFormat(int maxConn, int beamWidth, int numMergeWorkers, int bits, boolean compress, Float confidenceInterval, ExecutorService mergeExec)
Constructs a format using the given graph construction parameters and scalar quantization.

Parameters:
  `maxConn` - the maximum number of connections to a node in the HNSW graph
  `beamWidth` - the size of the queue maintained during graph construction.
  `numMergeWorkers` - number of workers (threads) that will be used when doing merge. If larger than 1, a non-null `ExecutorService` must be passed as mergeExec
  `bits` - the number of bits to use for scalar quantization (must be 4 or 7)
  `compress` - whether to compress the quantized vectors by another 50% when bits=4. If `true`, pairs of (4 bit quantized) dimensions are packed into a single byte. This must be `false` when bits=7. This provides a trade-off of 50% reduction in hot vector memory usage during searching, at some decode speed penalty.
  `confidenceInterval` - the confidenceInterval for scalar quantizing the vectors, when `null` it is calculated based on the vector field dimensions. When `0`, the quantiles are dynamically determined by sampling many confidence intervals and determining the most accurate pair.
  `mergeExec` - the `ExecutorService` that will be used by ALL vector writers that are generated by this format to do the merge

## Method Details

### fieldsWriter

public KnnVectorsWriter fieldsWriter(SegmentWriteState state) throws IOException
Description copied from class: `KnnVectorsFormat`
Returns a `KnnVectorsWriter` to write the vectors to the index.

Specified by:
  `fieldsWriter` in class `KnnVectorsFormat`
Throws:
  `IOException`

### fieldsReader

public KnnVectorsReader fieldsReader(SegmentReadState state) throws IOException
Description copied from class: `KnnVectorsFormat`
Returns a `KnnVectorsReader` to read the vectors from the index.

Specified by:
  `fieldsReader` in class `KnnVectorsFormat`
Throws:
  `IOException`

### getMaxDimensions

public int getMaxDimensions(String fieldName)
Description copied from class: `KnnVectorsFormat`
Returns the maximum number of vector dimensions supported by this codec for the given field name

Codecs implement this method to specify the maximum number of dimensions they support.

Specified by:
  `getMaxDimensions` in class `KnnVectorsFormat`
Parameters:
  `fieldName` - the field name
Returns:
  the maximum number of vector dimensions.

### toString

public String toString()

Overrides:
  `toString` in class `Object`