org.apache.lucene.search.grouping

Class AllGroupHeadsCollector<T>

java.lang.Object

org.apache.lucene.search.SimpleCollector

org.apache.lucene.search.grouping.AllGroupHeadsCollector<T>

All Implemented Interfaces:

Collector, LeafCollector

public abstract class AllGroupHeadsCollector<T>
extends SimpleCollector

This collector specializes in collecting the most relevant document (group head) for each group that matches the query. Clients should create new collectors by calling newCollector(GroupSelector, Sort)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AllGroupHeadsCollector.GroupHead<T> Represents a group head.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	compIDXEnd
protected LeafReaderContext	context
protected java.util.Map<T,AllGroupHeadsCollector.GroupHead<T>>	heads
protected int[]	reversed
protected Scorer	scorer
protected Sort	sort

Method Summary

Modifier and Type	Method and Description
void	collect(int doc) Called once for every document matching a query, with the unbased document number.
protected void	doSetNextReader(LeafReaderContext context) This method is called before collecting context.
protected java.util.Collection<? extends AllGroupHeadsCollector.GroupHead<T>>	getCollectedGroupHeads() Returns the collected group heads.
int	groupHeadsSize()
boolean	needsScores() Indicates if document scores are needed by this collector.
static <T> AllGroupHeadsCollector<T>	newCollector(GroupSelector<T> selector, Sort sort) Create a new AllGroupHeadsCollector based on the type of within-group Sort required
protected abstract AllGroupHeadsCollector.GroupHead<T>	newGroupHead(int doc, T value, LeafReaderContext context, Scorer scorer) Create a new GroupHead for the given group value, initialized with a doc, context and scorer
int[]	retrieveGroupHeads()
FixedBitSet	retrieveGroupHeads(int maxDoc)
void	setScorer(Scorer scorer) Called before successive calls to LeafCollector.collect(int).

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

getLeafCollector

Methods inherited from class java.lang.Object

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

Field Detail

sort

protected final Sort sort

reversed

protected final int[] reversed

compIDXEnd

protected final int compIDXEnd

heads

protected java.util.Map<T,AllGroupHeadsCollector.GroupHead<T>> heads

context

protected LeafReaderContext context

scorer

protected Scorer scorer

Method Detail

newCollector

public static <T> AllGroupHeadsCollector<T> newCollector(GroupSelector<T> selector,
                                                         Sort sort)

Create a new AllGroupHeadsCollector based on the type of within-group Sort required

Type Parameters:

T - the group value type

Parameters:

selector - a GroupSelector to define the groups

sort - the within-group sort to use to choose the group head document

retrieveGroupHeads

public FixedBitSet retrieveGroupHeads(int maxDoc)

Parameters:

maxDoc - The maxDoc of the top level IndexReader.

Returns:

a FixedBitSet containing all group heads.

retrieveGroupHeads

public int[] retrieveGroupHeads()

Returns:

an int array containing all group heads. The size of the array is equal to number of collected unique groups.

groupHeadsSize

public int groupHeadsSize()

Returns:

the number of group heads found for a query.

getCollectedGroupHeads

protected java.util.Collection<? extends AllGroupHeadsCollector.GroupHead<T>> getCollectedGroupHeads()

Returns the collected group heads. Subsequent calls should return the same group heads.

Returns:

the collected group heads

collect

public void collect(int doc)
             throws java.io.IOException

Description copied from interface: LeafCollector

Called once for every document matching a query, with the unbased document number.

Note: The collection of the current segment can be terminated by throwing a CollectionTerminatedException. In this case, the last docs of the current LeafReaderContext will be skipped and IndexSearcher will swallow the exception and continue collection with the next leaf.

Note: This is called in an inner search loop. For good search performance, implementations of this method should not call IndexSearcher.doc(int) or IndexReader.document(int) on every hit. Doing so can slow searches by an order of magnitude or more.

Specified by:

collect in interface LeafCollector

Specified by:

collect in class SimpleCollector

Throws:

java.io.IOException

needsScores

public boolean needsScores()

Description copied from interface: Collector

Indicates if document scores are needed by this collector.

Returns:

true if scores are needed.

doSetNextReader

protected void doSetNextReader(LeafReaderContext context)
                        throws java.io.IOException

Description copied from class: SimpleCollector

This method is called before collecting context.

Overrides:

doSetNextReader in class SimpleCollector

Throws:

java.io.IOException

setScorer

public void setScorer(Scorer scorer)
               throws java.io.IOException

Description copied from interface: LeafCollector

Called before successive calls to LeafCollector.collect(int). Implementations that need the score of the current document (passed-in to LeafCollector.collect(int)), should save the passed-in Scorer and call scorer.score() when needed.

Specified by:

setScorer in interface LeafCollector

Overrides:

setScorer in class SimpleCollector

Throws:

java.io.IOException

newGroupHead

protected abstract AllGroupHeadsCollector.GroupHead<T> newGroupHead(int doc,
                                                                    T value,
                                                                    LeafReaderContext context,
                                                                    Scorer scorer)
                                                             throws java.io.IOException

Create a new GroupHead for the given group value, initialized with a doc, context and scorer

Throws:

java.io.IOException