Package org.apache.lucene.search.grouping

Class CollapsingTopDocsCollector<T>

java.lang.Object

org.apache.lucene.search.SimpleCollector

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

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

All Implemented Interfaces:

Collector, LeafCollector

public final class CollapsingTopDocsCollector<T>
extends FirstPassGroupingCollector<T>

A collector that groups documents based on field values and returns CollapseTopFieldDocs output. The collapsing is done in a single pass by selecting only the top sorted document per collapse key. The value used for the collapse key of each group can be found in CollapseTopFieldDocs.collapseValues. TODO: If the sort is based on score we should propagate the mininum competitive score when orderedGroups is full. This is safe for collapsing since the group sort is the same as the query sort.

Field Summary

Fields

Modifier and Type	Field	Description
protected String	collapseField
protected Scorable	scorer
protected Sort	sort

Fields inherited from class org.apache.lucene.search.grouping.FirstPassGroupingCollector

orderedGroups

Method Summary

Modifier and Type	Method	Description
void	collect(int doc)	Called once for every document matching a query, with the unbased document number.
static CollapsingTopDocsCollector<?>	createKeyword(String collapseField, MappedFieldType collapseFieldType, Sort sort, int topN)	Create a collapsing top docs collector on a SortedDocValues field.
static CollapsingTopDocsCollector<?>	createNumeric(String collapseField, MappedFieldType collapseFieldType, Sort sort, int topN)	Create a collapsing top docs collector on a NumericDocValues field.
CollapseTopFieldDocs	getTopDocs()	Transform FirstPassGroupingCollector.getTopGroups(int) output in CollapseTopFieldDocs.
ScoreMode	scoreMode()	Indicates what features are required from the scorer.
void	setScorer(Scorable scorer)	Called before successive calls to LeafCollector.collect(int).

Methods inherited from class org.apache.lucene.search.grouping.FirstPassGroupingCollector

doSetNextReader, getGroupSelector, getTopGroups

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

collapseField

protected final String collapseField

sort

protected final Sort sort

scorer

protected Scorable scorer

Method Detail

getTopDocs

public CollapseTopFieldDocs getTopDocs()
                                throws IOException

Transform FirstPassGroupingCollector.getTopGroups(int) output in CollapseTopFieldDocs. The collapsing needs only one pass so we can get the final top docs at the end of the first pass.

Throws:

IOException

scoreMode

public ScoreMode scoreMode()

Description copied from interface: Collector

Indicates what features are required from the scorer.

Specified by:

scoreMode in interface Collector

Overrides:

scoreMode in class FirstPassGroupingCollector<T>

setScorer

public void setScorer(Scorable scorer)
               throws 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 FirstPassGroupingCollector<T>

Throws:

IOException

collect

public void collect(int doc)
             throws 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

Overrides:

collect in class FirstPassGroupingCollector<T>

Throws:

IOException

createNumeric

public static CollapsingTopDocsCollector<?> createNumeric(String collapseField,
                                                          MappedFieldType collapseFieldType,
                                                          Sort sort,
                                                          int topN)

Create a collapsing top docs collector on a NumericDocValues field. It accepts also SortedNumericDocValues field but the collect will fail with an IllegalStateException if a document contains more than one value for the field.

Parameters:

collapseField - The sort field used to group documents.

collapseFieldType - The MappedFieldType for this sort field.

sort - The Sort used to sort the collapsed hits. The collapsing keeps only the top sorted document per collapsed key. This must be non-null, ie, if you want to groupSort by relevance use Sort.RELEVANCE.

topN - How many top groups to keep.

createKeyword

public static CollapsingTopDocsCollector<?> createKeyword(String collapseField,
                                                          MappedFieldType collapseFieldType,
                                                          Sort sort,
                                                          int topN)

Create a collapsing top docs collector on a SortedDocValues field. It accepts also SortedSetDocValues field but the collect will fail with an IllegalStateException if a document contains more than one value for the field.

Parameters:

collapseField - The sort field used to group documents.

collapseFieldType - The MappedFieldType for this sort field.

sort - The Sort used to sort the collapsed hits. The collapsing keeps only the top sorted document per collapsed key. This must be non-null, ie, if you want to groupSort by relevance use Sort.RELEVANCE.

topN - How many top groups to keep.