org.apache.lucene.search.grouping
Class FirstPassGroupingCollector

java.lang.Object
  org.apache.lucene.search.Collector
      org.apache.lucene.search.grouping.FirstPassGroupingCollector

public class FirstPassGroupingCollector
extends org.apache.lucene.search.Collector

FirstPassGroupingCollector is the first of two passes necessary to collect grouped hits. This pass gathers the top N sorted groups.

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.

Constructor Summary

FirstPassGroupingCollector(String groupField, org.apache.lucene.search.Sort groupSort, int topNGroups)
Create the first pass collector.

Method Summary

boolean	acceptsDocsOutOfOrder()
void	collect(int doc)
String	getGroupField()
Collection<SearchGroup>	getTopGroups(int groupOffset, boolean fillFields) Returns top groups, starting from offset.
void	setNextReader(org.apache.lucene.index.IndexReader reader, int docBase)
void	setScorer(org.apache.lucene.search.Scorer scorer)

Methods inherited from class java.lang.Object

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

Constructor Detail

FirstPassGroupingCollector

public FirstPassGroupingCollector(String groupField,
                                  org.apache.lucene.search.Sort groupSort,
                                  int topNGroups)
                           throws IOException

Create the first pass collector.

Parameters:

groupField - The field used to group documents. This field must be single-valued and indexed (FieldCache is used to access its value per-document).

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.

Throws:

IOException

Method Detail

getTopGroups

public Collection<SearchGroup> 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.

getGroupField

public String getGroupField()

setScorer

public void setScorer(org.apache.lucene.search.Scorer scorer)
               throws IOException

Specified by:

setScorer in class org.apache.lucene.search.Collector

Throws:

IOException

collect

public void collect(int doc)
             throws IOException

Specified by:

collect in class org.apache.lucene.search.Collector

Throws:

IOException

acceptsDocsOutOfOrder

public boolean acceptsDocsOutOfOrder()

Specified by:

acceptsDocsOutOfOrder in class org.apache.lucene.search.Collector

setNextReader

public void setNextReader(org.apache.lucene.index.IndexReader reader,
                          int docBase)
                   throws IOException

Specified by:

setNextReader in class org.apache.lucene.search.Collector

Throws:

IOException