Package org.apache.lucene.search

Class BlendedTermQuery

  • public final class BlendedTermQuery
extends Query
    A Query that blends index statistics across multiple terms. This is particularly useful when several terms should produce identical scores, regardless of their index statistics.

    For instance imagine that you are resolving synonyms at search time, all terms should produce identical scores instead of the default behavior, which tends to give higher scores to rare terms.

    An other useful use-case is cross-field search: imagine that you would like to search for john on two fields: first_name and last_name. You might not want to give a higher weight to matches on the field where john is rarer, in which case BlendedTermQuery would help as well.

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

    • Method Detail

      • equals

        public boolean equals​(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 to those of the other instance. Utility methods are provided for certain repetitive code.

        Specified by:
        equals in class Query
        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.
        Specified by:
        hashCode in class Query
        See Also:
        Query.equals(Object)

      • 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

      • rewrite

        public final 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:
        IndexSearcher.rewrite(Query)

      • 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