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.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field and Description
protected 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)
protected void	doSetNextReader(LeafReaderContext readerContext)
GroupSelector<T>	getGroupSelector()
Collection<SearchGroup<T>>	getTopGroups(int groupOffset, boolean fillFields) Returns top groups, starting from offset.
boolean	needsScores()
void	setScorer(Scorer scorer)

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 TreeSet<CollectedSearchGroup<T>> orderedGroups

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

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()

getTopGroups

public Collection<SearchGroup<T>> getTopGroups(int groupOffset,
                                               boolean fillFields)
                                        throws 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:

IOException

setScorer

public void setScorer(Scorer scorer)
               throws IOException

Specified by:

setScorer in interface LeafCollector

Overrides:

setScorer in class SimpleCollector

Throws:

IOException

collect

public void collect(int doc)
             throws IOException

Specified by:

collect in interface LeafCollector

Specified by:

collect in class SimpleCollector

Throws:

IOException

doSetNextReader

protected void doSetNextReader(LeafReaderContext readerContext)
                        throws IOException

Overrides:

doSetNextReader in class SimpleCollector

Throws:

IOException

getGroupSelector

public GroupSelector<T> getGroupSelector()

Returns:

the GroupSelector used for this Collector