org.apache.lucene.queries.function

Class FunctionScoreQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.queries.function.FunctionScoreQuery

public final class FunctionScoreQuery
extends Query

A query that wraps another query, and uses a DoubleValuesSource to replace or modify the wrapped query's score If the DoubleValuesSource doesn't return a value for a particular document, then that document will be given a score of 0.

Constructor Summary

Constructors

Constructor and Description
FunctionScoreQuery(Query in, DoubleValuesSource source) Create a new FunctionScoreQuery

Method Summary

Modifier and Type	Method and Description
static FunctionScoreQuery	boostByQuery(Query in, Query boostMatch, float boostValue) Returns a FunctionScoreQuery where the scores of a wrapped query are multiplied by a boost factor if the document being scored also matches a separate boosting query.
static FunctionScoreQuery	boostByValue(Query in, DoubleValuesSource boost) Returns a FunctionScoreQuery where the scores of a wrapped query are multiplied by the value of a DoubleValuesSource.
Weight	createWeight(IndexSearcher searcher, boolean needsScores, float boost) Expert: Constructs an appropriate Weight implementation for this query.
boolean	equals(java.lang.Object o) Override and implement query instance equivalence properly in a subclass.
Query	getWrappedQuery()
int	hashCode() Override and implement query hash code properly in a subclass.
Query	rewrite(IndexReader reader) Expert: called to re-write queries into primitive queries.
java.lang.String	toString(java.lang.String field) Prints a query to a string, with field assumed to be the default field and omitted.

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

classHash, sameClassAs, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

FunctionScoreQuery

public FunctionScoreQuery(Query in,
                          DoubleValuesSource source)

Create a new FunctionScoreQuery

Parameters:

in - the query to wrap

source - a source of scores

Method Detail

getWrappedQuery

public Query getWrappedQuery()

Returns:

the wrapped Query

boostByValue

public static FunctionScoreQuery boostByValue(Query in,
                                              DoubleValuesSource boost)

Returns a FunctionScoreQuery where the scores of a wrapped query are multiplied by the value of a DoubleValuesSource. If the source has no value for a particular document, the score for that document is preserved as-is.

Parameters:

in - the query to boost

boost - a DoubleValuesSource containing the boost values

boostByQuery

public static FunctionScoreQuery boostByQuery(Query in,
                                              Query boostMatch,
                                              float boostValue)

Returns a FunctionScoreQuery where the scores of a wrapped query are multiplied by a boost factor if the document being scored also matches a separate boosting query. Documents that do not match the boosting query have their scores preserved. This may be used to 'demote' documents that match the boosting query, by passing in a boostValue between 0 and 1.

Parameters:

in - the query to boost

boostMatch - the boosting query

boostValue - the amount to boost documents which match the boosting query

createWeight

public Weight createWeight(IndexSearcher searcher,
                           boolean needsScores,
                           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

needsScores - True if document scores (Scorer.score()) are needed.

boost - The boost that is propagated by the parent queries.

Throws:

java.io.IOException

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

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

equals

public boolean equals(java.lang.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 that 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)