org.apache.lucene.search.grouping
Class TermFirstPassGroupingCollector

java.lang.Object
  org.apache.lucene.search.Collector
      org.apache.lucene.search.grouping.AbstractFirstPassGroupingCollector<String>
          org.apache.lucene.search.grouping.TermFirstPassGroupingCollector

public class TermFirstPassGroupingCollector
extends AbstractFirstPassGroupingCollector<String>

Concrete implementation of AbstractFirstPassGroupingCollector that groups based on field values and more specifically uses FieldCache.StringIndex to collect groups.

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

Constructor Summary

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

Method Summary

protected String	copyDocGroupValue(String groupValue, String 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 String	getDocGroupValue(int doc) Returns the group value for the specified doc.
void	setNextReader(IndexReader reader, int docBase) Called before collecting from each IndexReader.

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

acceptsDocsOutOfOrder, collect, getTopGroups, setScorer

Methods inherited from class java.lang.Object

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

Constructor Detail

TermFirstPassGroupingCollector

public TermFirstPassGroupingCollector(String groupField,
                                      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 - When I/O related errors occur

Method Detail

getDocGroupValue

protected String getDocGroupValue(int doc)

Description copied from class: AbstractFirstPassGroupingCollector

Returns the group value for the specified doc.

Specified by:

getDocGroupValue in class AbstractFirstPassGroupingCollector<String>

Parameters:

doc - The specified doc

Returns:

the group value for the specified doc

copyDocGroupValue

protected String copyDocGroupValue(String groupValue,
                                   String reuse)

Description copied from class: AbstractFirstPassGroupingCollector

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.

Specified by:

copyDocGroupValue in class AbstractFirstPassGroupingCollector<String>

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

setNextReader

public void setNextReader(IndexReader reader,
                          int docBase)
                   throws IOException

Description copied from class: Collector

Called before collecting from each IndexReader. All doc ids in Collector.collect(int) will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids in Collector.collect(int).

Overrides:

setNextReader in class AbstractFirstPassGroupingCollector<String>

Parameters:

reader - next IndexReader

Throws:

IOException