org.apache.lucene.search.grouping

Class FirstPassGroupingCollector<T>

java.lang.Object

org.apache.lucene.search.SimpleCollector

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

All Implemented Interfaces:

Collector, LeafCollector

public class FirstPassGroupingCollector<T>
extends SimpleCollector

FirstPassGroupingCollector is the first of two passes necessary to collect grouped hits. This pass gathers the top N sorted groups. Groups are defined by a GroupSelector

See org.apache.lucene.search.grouping for more details including a full code example.

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.TreeSet<CollectedSearchGroup<T>>	orderedGroups

Constructor Summary

Constructors

Constructor and Description
FirstPassGroupingCollector(GroupSelector<T> groupSelector, Sort groupSort, int topNGroups) Create the first pass collector.

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 readerContext) This method is called before collecting context.
GroupSelector<T>	getGroupSelector()
java.util.Collection<SearchGroup<T>>	getTopGroups(int groupOffset, boolean fillFields) Returns top groups, starting from offset.
boolean	needsScores() Indicates if document scores are needed by this collector.
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

orderedGroups

protected java.util.TreeSet<CollectedSearchGroup<T>> orderedGroups

Constructor Detail

FirstPassGroupingCollector

public FirstPassGroupingCollector(GroupSelector<T> groupSelector,
                                  Sort groupSort,
                                  int topNGroups)

Create the first pass collector.

Parameters:

groupSelector - a GroupSelector used to defined groups

groupSort - The Sort used to sort the groups. The top sorted document within each group according to groupSort, determines how that group sorts against other groups. This must be non-null, ie, if you want to groupSort by relevance use Sort.RELEVANCE.

topNGroups - How many top groups to keep.

Method Detail

needsScores

public boolean needsScores()

Description copied from interface: Collector

Indicates if document scores are needed by this collector.

Returns:

true if scores are needed.

getTopGroups

public java.util.Collection<SearchGroup<T>> getTopGroups(int groupOffset,
                                                         boolean fillFields)
                                                  throws java.io.IOException

Returns top groups, starting from offset. This may return null, if no groups were collected, or if the number of unique groups collected is <= offset.

Parameters:

groupOffset - The offset in the collected groups

fillFields - Whether to fill to SearchGroup.sortValues

Returns:

top groups, starting from offset

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

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

doSetNextReader

protected void doSetNextReader(LeafReaderContext readerContext)
                        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

getGroupSelector

public GroupSelector<T> getGroupSelector()

Returns:

the GroupSelector used for this Collector