Class Query

    • Constructor Detail

      • Query

        public Query()
    • Method Detail

      • toString

        public abstract String toString​(String field)
        Prints a query to a string, with field assumed to be the default field and omitted.
      • toString

        public final String toString()
        Prints a query to a string.
        toString in class Object
      • createWeight

        public Weight createWeight​(IndexSearcher searcher,
                                   ScoreMode scoreMode,
                                   float boost)
                            throws IOException
        Expert: Constructs an appropriate Weight implementation for this query.

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

        scoreMode - How the produced scorers will be consumed.
        boost - The boost that is propagated by the parent queries.
      • rewrite

        public Query rewrite​(IndexSearcher indexSearcher)
                      throws IOException
        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.

        See Also:
      • visit

        public abstract void visit​(QueryVisitor visitor)
        Recurse through the query tree, visiting any child queries.
        visitor - a QueryVisitor to be called by each query in the tree
      • equals

        public abstract boolean equals​(Object obj)
        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.

        equals in class Object
        See Also:
        sameClassAs(Object), classHash()
      • hashCode

        public abstract int hashCode()
        Override and implement query hash code properly in a subclass. This is required so that QueryCache works properly.
        hashCode in class Object
        See Also:
      • sameClassAs

        protected final boolean sameClassAs​(Object other)
        Utility method to check whether other is not null and is exactly of the same class as this object's class.

        When this method is used in an implementation of equals(Object), consider using classHash() in the implementation of hashCode() to differentiate different class.

      • classHash

        protected final int classHash()
        Provides a constant integer for a given class, derived from the name of the class. The rationale for not using just Object.hashCode() is that classes may be assigned different hash codes for each execution and we want hashes to be possibly consistent to facilitate debugging.