Class CombinedFieldQuery

java.lang.Object
org.apache.lucene.search.Query
org.apache.lucene.sandbox.search.CombinedFieldQuery
All Implemented Interfaces:
Accountable

public final class CombinedFieldQuery 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.

The query works as follows:

  1. Given a list of fields and weights, it pretends there is a synthetic combined field where all terms have been indexed. It computes new term and collection statistics for this combined field.
  2. It uses a disjunction iterator and IndexSearcher.getSimilarity() to score documents.

In order for a similarity to be compatible, Similarity.computeNorm(org.apache.lucene.index.FieldInvertState) must be additive: the norm of the combined field is the sum of norms for each individual field. The norms must also be encoded using SmallFloat.intToByte4(int). These requirements hold for all similarities that compute norms the same way as SimilarityBase.computeNorm(org.apache.lucene.index.FieldInvertState), which includes BM25Similarity and DFRSimilarity. Per-field similarities are not supported.

The query also requires that either all fields or no fields have norms enabled. Having only some fields with norms enabled can result in errors.

The scoring is based on BM25F's simple formula described in: http://www.staff.city.ac.uk/~sb317/papers/foundations_bm25_review.pdf. This query implements the same approach but allows other similarities besides BM25Similarity.

  • Field Details

  • Constructor Details

  • Method Details

    • getTerms

      public List<Term> getTerms()
    • 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.

      Specified by:
      equals in class Query
      See Also:
    • 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:
    • 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(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.

      Overrides:
      rewrite in class Query
      Throws:
      IOException
      See Also:
    • 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
    • rewriteToBoolean

      private BooleanQuery rewriteToBoolean()
    • createWeight

      public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws 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
      Parameters:
      scoreMode - How the produced scorers will be consumed.
      boost - The boost that is propagated by the parent queries.
      Throws:
      IOException
    • validateConsistentNorms

      private void validateConsistentNorms(IndexReader reader)