org.apache.lucene.search.grouping

Class GroupReducer<T,C extends Collector>

java.lang.Object

org.apache.lucene.search.grouping.GroupReducer<T,C>

Type Parameters:

T - the type of the value used for grouping

C - the type of Collector used to reduce each group

public abstract class GroupReducer<T,C extends Collector>
extends Object

Concrete implementations of this class define what to collect for individual groups during the second-pass of a grouping search. Each group is assigned a Collector returned by newCollector(), and LeafCollector.collect(int) is called for each document that is in a group

See Also:

SecondPassGroupingCollector

Constructor Summary

Constructors

Constructor and Description
GroupReducer()

Method Summary

Modifier and Type	Method and Description
void	collect(T value, int doc) Collect a given document into a given group
C	getCollector(T value) Get the Collector for a given group
abstract boolean	needsScores() Whether or not this reducer requires collected documents to be scored
protected abstract C	newCollector() Creates a new Collector for each group
void	setGroups(Collection<SearchGroup<T>> groups) Define which groups should be reduced.
void	setNextReader(LeafReaderContext ctx) Called when the parent SecondPassGroupingCollector moves to a new segment
void	setScorer(Scorable scorer) Set the Scorer on all group collectors

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GroupReducer

public GroupReducer()

Method Detail

setGroups

public void setGroups(Collection<SearchGroup<T>> groups)

Define which groups should be reduced. Called by SecondPassGroupingCollector

needsScores

public abstract boolean needsScores()

Whether or not this reducer requires collected documents to be scored

newCollector

protected abstract C newCollector()

Creates a new Collector for each group

getCollector

public final C getCollector(T value)

Get the Collector for a given group

collect

public final void collect(T value,
                          int doc)
                   throws IOException

Collect a given document into a given group

Throws:

IOException - on error

setScorer

public final void setScorer(Scorable scorer)
                     throws IOException

Set the Scorer on all group collectors

Throws:

IOException

setNextReader

public final void setNextReader(LeafReaderContext ctx)
                         throws IOException

Called when the parent SecondPassGroupingCollector moves to a new segment

Throws:

IOException