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

Direct Known Subclasses:

FunctionFirstPassGroupingCollector, TermFirstPassGroupingCollector

public abstract 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. Concrete subclasses define what a group is and how it is internally collected.

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(Sort groupSort, int topNGroups) Create the first pass collector.

Method Summary

Modifier and Type	Method and Description
void	collect(int doc)
protected abstract T	copyDocGroupValue(T groupValue, T reuse) Returns a copy of the specified group value by creating a new instance and copying the value from the specified groupValue in the new instance.
protected void	doSetNextReader(LeafReaderContext readerContext)
protected abstract T	getDocGroupValue(int doc) Returns the group value for the specified doc.
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(Sort groupSort,
                                  int topNGroups)

Create the first pass collector.

Parameters:

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)

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

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

getDocGroupValue

protected abstract T getDocGroupValue(int doc)
                               throws IOException

Returns the group value for the specified doc.

Parameters:

doc - The specified doc

Returns:

the group value for the specified doc

Throws:

IOException

copyDocGroupValue

protected abstract T copyDocGroupValue(T groupValue,
                                       T reuse)

Returns a copy of the specified group value by creating a new instance and copying the value from the specified groupValue in the new instance. Or optionally the reuse argument can be used to copy the group value in.

Parameters:

groupValue - The group value to copy

reuse - Optionally a reuse instance to prevent a new instance creation

Returns:

a copy of the specified group value