KnnFloatVectorQuery (Lucene 10.5.0 core API)
Description: declaration: package: org.apache.lucene.search, class: KnnFloatVectorQuery

Package org.apache.lucene.search

# Class KnnFloatVectorQuery

java.lang.Object
org.apache.lucene.search.Query
org.apache.lucene.search.KnnFloatVectorQuery

public class KnnFloatVectorQuery extends Query
Uses `KnnVectorsReader.search(String, float[], KnnCollector, AcceptDocs)` to perform nearest neighbour search.

This query also allows for performing a kNN search subject to a filter. In this case, it first executes the filter for each leaf, then chooses a strategy dynamically:

- If the filter cost is less than k, just execute an exact search
- Otherwise run a kNN search subject to the filter
- If the kNN search visits too many vectors without completing, stop and run an exact search

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected final String`
  `field`
  `protected final Query`
  `filter`
  `protected final int`
  `k`
  `protected final KnnSearchStrategy`
  `searchStrategy`
  `protected final float[]`
  `target`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `KnnFloatVectorQuery(String field, float[] target, int k)`
  Find the `k` nearest documents to the target vector according to the vectors in the given field.
  `KnnFloatVectorQuery(String field, float[] target, int k, Query filter)`
  Find the `k` nearest documents to the target vector according to the vectors in the given field.
  `KnnFloatVectorQuery(String field, float[] target, int k, Query filter, KnnSearchStrategy searchStrategy)`
  Find the `k` nearest documents to the target vector according to the vectors in the given field.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected TopDocs`
  `approximateSearch(LeafReaderContext context, AcceptDocs acceptDocs, int visitedLimit, KnnCollectorManager knnCollectorManager)`
  `boolean`
  `equals(Object o)`
  Override and implement query instance equivalence properly in a subclass.
  `protected TopDocs`
  `exactSearch(LeafReaderContext context, DocIdSetIterator acceptIterator, QueryTimeout queryTimeout)`
  `String`
  `getField()`
  `Query`
  `getFilter()`
  `int`
  `getK()`
  `protected KnnCollectorManager`
  `getKnnCollectorManager(int k, IndexSearcher searcher)`
  `KnnSearchStrategy`
  `getSearchStrategy()`
  `float[]`
  `getTargetCopy()`
  `int`
  `hashCode()`
  Override and implement query hash code properly in a subclass.
  `protected TopDocs`
  `mergeLeafResults(TopDocs[] perLeafResults)`
  Merges all segment-level kNN results to get the index-level kNN results.
  `Query`
  `rewrite(IndexSearcher indexSearcher)`
  Expert: called to re-write queries into primitive queries.
  `protected TopDocs`
  `searchLeaf(LeafReaderContext ctx, Weight filterWeight, TimeLimitingKnnCollectorManager timeLimitingKnnCollectorManager)`
  `String`
  `toString(String field)`
  Prints a query to a string, with `field` assumed to be the default field and omitted.
  `void`
  `visit(QueryVisitor visitor)`
  Recurse through the query tree, visiting any child queries.

  ### Methods inherited from class org.apache.lucene.search.Query

  `classHash, createWeight, sameClassAs, toString`

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

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

- ## Field Details

  - ### target

    protected final float[] target

  - ### field

    protected final String field

  - ### k

    protected final int k

  - ### filter

    protected final Query filter

  - ### searchStrategy

    protected final KnnSearchStrategy searchStrategy

- ## Constructor Details

  - ### KnnFloatVectorQuery

    public KnnFloatVectorQuery(String field, float[] target, int k)
    Find the `k` nearest documents to the target vector according to the vectors in the given field. `target` vector.
    Parameters:
      `field` - a field that has been indexed as a `KnnFloatVectorField`.
      `target` - the target of the search
      `k` - the number of documents to find
    Throws:
      `IllegalArgumentException` - if `k` is less than 1

  - ### KnnFloatVectorQuery

    public KnnFloatVectorQuery(String field, float[] target, int k, Query filter)
    Find the `k` nearest documents to the target vector according to the vectors in the given field. `target` vector.
    Parameters:
      `field` - a field that has been indexed as a `KnnFloatVectorField`.
      `target` - the target of the search
      `k` - the number of documents to find
      `filter` - a filter applied before the vector search
    Throws:
      `IllegalArgumentException` - if `k` is less than 1

  - ### KnnFloatVectorQuery

    public KnnFloatVectorQuery(String field, float[] target, int k, Query filter, KnnSearchStrategy searchStrategy)
    Find the `k` nearest documents to the target vector according to the vectors in the given field. `target` vector.
    Parameters:
      `field` - a field that has been indexed as a `KnnFloatVectorField`.
      `target` - the target of the search
      `k` - the number of documents to find
      `filter` - a filter applied before the vector search
      `searchStrategy` - the search strategy to use. If null, the default strategy will be used. The underlying format may not support all strategies and is free to ignore the requested strategy.
    WARNING: This API is experimental and might change in incompatible ways in the next release.

- ## Method Details

  - ### approximateSearch

    protected TopDocs approximateSearch(LeafReaderContext context, AcceptDocs acceptDocs, int visitedLimit, KnnCollectorManager knnCollectorManager) throws IOException
    Throws:
      `IOException`

  - ### toString

    public String toString(String field)
    Description copied from class: `Query`
    Prints a query to a string, with `field` assumed to be the default field and omitted.
    Specified by:
      `toString` in class `Query`

  - ### equals

    public boolean equals(Object o)
    Description copied from class: `Query`
    Override and implement query instance equivalence properly in a subclass. This is required so that `QueryCache` works properly.

    Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical to those of the other instance. Utility methods are provided for certain repetitive code.

    See Also:
      - `Query.sameClassAs(Object)`
      - `Query.classHash()`

  - ### hashCode

    public int hashCode()
    Description copied from class: `Query`
    Override and implement query hash code properly in a subclass. This is required so that `QueryCache` works properly.
    See Also:
      - `Query.equals(Object)`

  - ### getTargetCopy

    public float[] getTargetCopy()
    Returns:
      the target query vector of the search. Each vector element is a float.

  - ### rewrite

    public Query rewrite(IndexSearcher indexSearcher) throws IOException
    Description copied from class: `Query`
    Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.

    Callers are expected to call `rewrite` multiple times if necessary, until the rewritten query is the same as the original query.

    The rewrite process may be able to make use of IndexSearcher's executor and be executed in parallel if the executor is provided.

    Overrides:
      `rewrite` in class `Query`
    Throws:
      `IOException`
    See Also:
      - `IndexSearcher.rewrite(Query)`

  - ### searchLeaf

    protected TopDocs searchLeaf(LeafReaderContext ctx, Weight filterWeight, TimeLimitingKnnCollectorManager timeLimitingKnnCollectorManager) throws IOException
    Throws:
      `IOException`

  - ### getKnnCollectorManager

    protected KnnCollectorManager getKnnCollectorManager(int k, IndexSearcher searcher)

  - ### exactSearch

    protected TopDocs exactSearch(LeafReaderContext context, DocIdSetIterator acceptIterator, QueryTimeout queryTimeout) throws IOException
    Throws:
      `IOException`

  - ### mergeLeafResults

    protected TopDocs mergeLeafResults(TopDocs[] perLeafResults)
    Merges all segment-level kNN results to get the index-level kNN results.

    The default implementation delegates to `TopDocs.merge(int, TopDocs[])` to find the overall top `k`, which requires input results to be sorted.

    This method is useful for reading and / or modifying the final results as needed.

    Parameters:
      `perLeafResults` - array of segment-level kNN results.
    Returns:
      index-level kNN results (no constraint on their ordering).
    WARNING: This API is experimental and might change in incompatible ways in the next release.

  - ### visit

    public void visit(QueryVisitor visitor)
    Description copied from class: `Query`
    Recurse through the query tree, visiting any child queries.
    Specified by:
      `visit` in class `Query`
    Parameters:
      `visitor` - a QueryVisitor to be called by each query in the tree

  - ### getField

    public String getField()
    Returns:
      the knn vector field where the knn vector search happens.

  - ### getK

    public int getK()
    Returns:
      the max number of results the KnnVector search returns.

  - ### getFilter

    public Query getFilter()
    Returns:
      the filter that is executed before the KnnVector search happens. Only the results accepted by this filter are returned by the KnnVector search.

  - ### getSearchStrategy

    public KnnSearchStrategy getSearchStrategy()