org.apache.lucene.search

Class FilteredQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.FilteredQuery

All Implemented Interfaces:

Cloneable

public class FilteredQuery
extends Query

A query that applies a filter to the results of another query.

Note: the bits are retrieved from the filter each time this query is used in a search - use a CachingWrapperFilter to avoid regenerating the bits every time.

Since:

1.4

See Also:

CachingWrapperQuery

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FilteredQuery.FilterStrategy Abstract class that defines how the filter (DocIdSet) applied during document collection.
static class	FilteredQuery.RandomAccessFilterStrategy A FilteredQuery.FilterStrategy that conditionally uses a random access filter if the given DocIdSet supports random access (returns a non-null value from DocIdSet.bits()) and FilteredQuery.RandomAccessFilterStrategy.useRandomAccess(Bits, long) returns true.

Field Summary

Fields

Modifier and Type	Field and Description
static FilteredQuery.FilterStrategy	LEAP_FROG_FILTER_FIRST_STRATEGY A filter strategy that uses a "leap-frog" approach (also called "zig-zag join").
static FilteredQuery.FilterStrategy	LEAP_FROG_QUERY_FIRST_STRATEGY A filter strategy that uses a "leap-frog" approach (also called "zig-zag join").
static FilteredQuery.FilterStrategy	QUERY_FIRST_FILTER_STRATEGY A filter strategy that advances the Query or rather its Scorer first and consults the filter DocIdSet for each matched document.
static FilteredQuery.FilterStrategy	RANDOM_ACCESS_FILTER_STRATEGY A FilteredQuery.FilterStrategy that conditionally uses a random access filter if the given DocIdSet supports random access (returns a non-null value from DocIdSet.bits()) and FilteredQuery.RandomAccessFilterStrategy.useRandomAccess(Bits, long) returns true.

Constructor Summary

Constructors

Constructor and Description
FilteredQuery(Query query, Filter filter) Constructs a new query which applies a filter to the results of the original query.
FilteredQuery(Query query, Filter filter, FilteredQuery.FilterStrategy strategy) Expert: Constructs a new query which applies a filter to the results of the original query.

Method Summary

Methods

Modifier and Type	Method and Description
Weight	createWeight(IndexSearcher searcher, boolean needsScores) Returns a Weight that applies the filter to the enclosed query's Weight.
boolean	equals(Object o) Returns true iff o is equal to this.
void	extractTerms(Set<Term> terms) Expert: adds all terms occurring in this query to the terms set.
Filter	getFilter() Returns this FilteredQuery's filter
FilteredQuery.FilterStrategy	getFilterStrategy() Returns this FilteredQuery's FilteredQuery.FilterStrategy
Query	getQuery() Returns this FilteredQuery's (unfiltered) Query
int	hashCode() Returns a hash code value for this object.
Query	rewrite(IndexReader reader) Expert: called to re-write queries into primitive queries.
String	toString(String s) Prints a user-readable version of this query.

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

clone, getBoost, setBoost, toString

Methods inherited from class java.lang.Object

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

Field Detail

RANDOM_ACCESS_FILTER_STRATEGY

public static final FilteredQuery.FilterStrategy RANDOM_ACCESS_FILTER_STRATEGY

A FilteredQuery.FilterStrategy that conditionally uses a random access filter if the given DocIdSet supports random access (returns a non-null value from DocIdSet.bits()) and FilteredQuery.RandomAccessFilterStrategy.useRandomAccess(Bits, long) returns true. Otherwise this strategy falls back to a "zig-zag join" ( LEAP_FROG_FILTER_FIRST_STRATEGY) strategy.

Note: this strategy is the default strategy in FilteredQuery

LEAP_FROG_FILTER_FIRST_STRATEGY

public static final FilteredQuery.FilterStrategy LEAP_FROG_FILTER_FIRST_STRATEGY

A filter strategy that uses a "leap-frog" approach (also called "zig-zag join"). The scorer and the filter take turns trying to advance to each other's next matching document, often jumping past the target document. When both land on the same document, it's collected.

Note: This strategy uses the filter to lead the iteration.

LEAP_FROG_QUERY_FIRST_STRATEGY

public static final FilteredQuery.FilterStrategy LEAP_FROG_QUERY_FIRST_STRATEGY

A filter strategy that uses a "leap-frog" approach (also called "zig-zag join"). The scorer and the filter take turns trying to advance to each other's next matching document, often jumping past the target document. When both land on the same document, it's collected.

Note: This strategy uses the query to lead the iteration.

QUERY_FIRST_FILTER_STRATEGY

public static final FilteredQuery.FilterStrategy QUERY_FIRST_FILTER_STRATEGY

A filter strategy that advances the Query or rather its Scorer first and consults the filter DocIdSet for each matched document.

Note: this strategy requires a DocIdSet.bits() to return a non-null value. Otherwise this strategy falls back to LEAP_FROG_QUERY_FIRST_STRATEGY

Use this strategy if the filter computation is more expensive than document scoring or if the filter has a linear running time to compute the next matching doc like exact geo distances.

Constructor Detail

FilteredQuery

public FilteredQuery(Query query,
             Filter filter)

Constructs a new query which applies a filter to the results of the original query. Filter.getDocIdSet(org.apache.lucene.index.LeafReaderContext, org.apache.lucene.util.Bits) will be called every time this query is used in a search.

Parameters:

query - Query to be filtered, cannot be null.

filter - Filter to apply to query results, cannot be null.

FilteredQuery

public FilteredQuery(Query query,
             Filter filter,
             FilteredQuery.FilterStrategy strategy)

Expert: Constructs a new query which applies a filter to the results of the original query. Filter.getDocIdSet(org.apache.lucene.index.LeafReaderContext, org.apache.lucene.util.Bits) will be called every time this query is used in a search.

Parameters:

query - Query to be filtered, cannot be null.

filter - Filter to apply to query results, cannot be null.

strategy - a filter strategy used to create a filtered scorer.

See Also:

FilteredQuery.FilterStrategy

Method Detail

createWeight

public Weight createWeight(IndexSearcher searcher,
                  boolean needsScores)
                    throws IOException

Returns a Weight that applies the filter to the enclosed query's Weight. This is accomplished by overriding the Scorer returned by the Weight.

Overrides:

createWeight in class Query

needsScores - True if document scores (Scorer.score()) or match frequencies (Scorer.freq()) are needed.

Throws:

IOException

rewrite

public Query rewrite(IndexReader reader)
              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.

Overrides:

rewrite in class Query

Throws:

IOException

getQuery

public final Query getQuery()

Returns this FilteredQuery's (unfiltered) Query

getFilter

public final Filter getFilter()

Returns this FilteredQuery's filter

getFilterStrategy

public FilteredQuery.FilterStrategy getFilterStrategy()

Returns this FilteredQuery's FilteredQuery.FilterStrategy

extractTerms

public void extractTerms(Set<Term> terms)

Description copied from class: Query

Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its rewritten form.

Overrides:

extractTerms in class Query

toString

public String toString(String s)

Prints a user-readable version of this query.

Specified by:

toString in class Query

equals

public boolean equals(Object o)

Returns true iff o is equal to this.

Overrides:

equals in class Query

hashCode

public int hashCode()

Returns a hash code value for this object.

Overrides:

hashCode in class Query