Class KnnVectorQuery

  • @Deprecated
    public class KnnVectorQuery
    extends KnnFloatVectorQuery
    Uses, float[], KnnCollector, Bits) 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 Detail

      • field

        protected final String field
      • k

        protected final int k
    • Constructor Detail

      • KnnVectorQuery

        public KnnVectorQuery​(String field,
                              float[] target,
                              int k)
      • KnnVectorQuery

        public KnnVectorQuery​(String field,
                              float[] target,
                              int k,
                              Query filter)
    • Method Detail

      • 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.

        However, if any of the intermediary queries do not satisfy the new API, parallel rewrite is not possible for any subsequent sub-queries. To take advantage of this API, the entire query tree must override this method.

        rewrite in class Query
        See Also:
      • 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.

        perLeafResults - array of segment-level kNN results.
        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
        visitor - a QueryVisitor to be called by each query in the tree
      • getField

        public String getField()
        the knn vector field where the knn vector search happens.
      • getK

        public int getK()
        the max number of results the KnnVector search returns.
      • getFilter

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