Class BM25FQuery

  • All Implemented Interfaces:
    Accountable

    public final class BM25FQuery
    extends Query
    implements Accountable
    A Query that treats multiple fields as a single stream and scores terms as if you had indexed them as a single term in a single field. For scoring purposes this query implements the BM25F's simple formula described in: http://www.staff.city.ac.uk/~sb317/papers/foundations_bm25_review.pdf The per-field similarity is ignored but to be compatible each field must use a Similarity at index time that encodes norms the same way as SimilarityBase.computeNorm(org.apache.lucene.index.FieldInvertState).
    • Field Detail

      • BASE_RAM_BYTES

        private static final long BASE_RAM_BYTES
      • fieldTerms

        private final Term[] fieldTerms
      • ramBytesUsed

        private final long ramBytesUsed
    • Method Detail

      • getTerms

        public java.util.List<Term> getTerms()
      • toString

        public java.lang.String toString​(java.lang.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
      • 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.
        Specified by:
        hashCode in class Query
        See Also:
        Query.equals(Object)
      • equals

        public boolean equals​(java.lang.Object other)
        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 that other instance. Utility methods are provided for certain repetitive code.
        Specified by:
        equals in class Query
        See Also:
        Query.sameClassAs(Object), Query.classHash()
      • ramBytesUsed

        public long ramBytesUsed()
        Description copied from interface: Accountable
        Return the memory usage of this object in bytes. Negative values are illegal.
        Specified by:
        ramBytesUsed in interface Accountable
      • rewrite

        public Query rewrite​(IndexReader reader)
                      throws java.io.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.
        Overrides:
        rewrite in class Query
        Throws:
        java.io.IOException
      • visit

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

        private BooleanQuery rewriteToBoolean()
      • createWeight

        public Weight createWeight​(IndexSearcher searcher,
                                   ScoreMode scoreMode,
                                   float boost)
                            throws java.io.IOException
        Description copied from class: Query
        Expert: Constructs an appropriate Weight implementation for this query.

        Only implemented by primitive queries, which re-write to themselves.

        Overrides:
        createWeight in class Query
        scoreMode - How the produced scorers will be consumed.
        boost - The boost that is propagated by the parent queries.
        Throws:
        java.io.IOException