Package org.apache.lucene.search

Class BoostQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.BoostQuery

public final class BoostQuery
extends Query

A Query wrapper that allows to give a boost to the wrapped query. Boost values that are less than one will give less importance to this query compared to other ones while values that are greater than one will give more importance to the scores returned by this query.

More complex boosts can be applied by using FunctionScoreQuery in the lucene-queries module

Constructor Summary

Constructors

Constructor	Description
BoostQuery(Query query, float boost)	Sole constructor: wrap query in such a way that the produced scores will be boosted by boost.

Method Summary

Modifier and Type	Method	Description
Weight	createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost)	Expert: Constructs an appropriate Weight implementation for this query.
boolean	equals(Object other)	Override and implement query instance equivalence properly in a subclass.
float	getBoost()	Return the applied boost.
Query	getQuery()	Return the wrapped Query.
int	hashCode()	Override and implement query hash code properly in a subclass.
Query	rewrite(IndexSearcher indexSearcher)	Expert: called to re-write queries into primitive queries.
String	toString(String field)	Prints a query to a string, with field assumed to be the default field and omitted.
void	visit(QueryVisitor visitor)	Recurse through the query tree, visiting any child queries.

Methods inherited from class org.apache.lucene.search.Query

classHash, rewrite, sameClassAs, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Details

BoostQuery

public BoostQuery(Query query,
 float boost)

Sole constructor: wrap query in such a way that the produced scores will be boosted by boost.

Method Details

getQuery

public Query getQuery()

Return the wrapped Query.

getBoost

public float getBoost()

Return the applied boost.

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)

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:

• 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

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

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