org.apache.lucene.search.grouping
Class AllGroupsCollector

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

public class AllGroupsCollector
extends Collector

A collector that collects all groups that match the query. Only the group value is collected, and the order is undefined. This collector does not determine the most relevant document of a group.

Implementation detail: an int hash set (SentinelIntSet) is used to detect if a group is already added to the total count. For each segment the int set is cleared and filled with previous counted groups that occur in the new segment.

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

Constructor Summary

AllGroupsCollector(String groupField)
Constructs a AllGroupsCollector.

AllGroupsCollector(String groupField, int initialSize)
Expert: Constructs a AllGroupsCollector

Method Summary

boolean	acceptsDocsOutOfOrder() Return true if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to Collector.collect(int).
void	collect(int doc) Called once for every document matching a query, with the unbased document number.
int	getGroupCount() Returns the total number of groups for the executed search.
Collection<String>	getGroups() Returns the group values This is an unordered collections of group values.
void	setNextReader(IndexReader reader, int docBase) Called before collecting from each IndexReader.
void	setScorer(Scorer scorer) Called before successive calls to Collector.collect(int).

Methods inherited from class java.lang.Object

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

Constructor Detail

AllGroupsCollector

public AllGroupsCollector(String groupField,
                          int initialSize)

Expert: Constructs a AllGroupsCollector

Parameters:

groupField - The field to group by

initialSize - The initial allocation size of the internal int set and group list which should roughly match the total number of expected unique groups. Be aware that the heap usage is 4 bytes * initialSize.

AllGroupsCollector

public AllGroupsCollector(String groupField)

Constructs a AllGroupsCollector. This sets the initial allocation size for the internal int set and group list to 128.

Parameters:

groupField - The field to group by

Method Detail

setScorer

public void setScorer(Scorer scorer)
               throws IOException

Description copied from class: Collector

Called before successive calls to Collector.collect(int). Implementations that need the score of the current document (passed-in to Collector.collect(int)), should save the passed-in Scorer and call scorer.score() when needed.

Specified by:

setScorer in class Collector

Throws:

IOException

collect

public void collect(int doc)
             throws IOException

Description copied from class: Collector

Called once for every document matching a query, with the unbased document number.

Note: This is called in an inner search loop. For good search performance, implementations of this method should not call Searcher.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 class Collector

Throws:

IOException

getGroupCount

public int getGroupCount()

Returns the total number of groups for the executed search. This is a convenience method. The following code snippet has the same effect:

getGroups().size()

Returns:

The total number of groups for the executed search

getGroups

public Collection<String> getGroups()

Returns the group values

This is an unordered collections of group values. For each group that matched the query there is a String representing a group value.

Returns:

the group values

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).

Specified by:

setNextReader in class Collector

Parameters:

reader - next IndexReader

Throws:

IOException

acceptsDocsOutOfOrder

public boolean acceptsDocsOutOfOrder()

Description copied from class: Collector

Return true if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to Collector.collect(int).

Most Lucene Query implementations will visit matching docIDs in order. However, some queries (currently limited to certain cases of BooleanQuery) can achieve faster searching if the Collector allows them to deliver the docIDs out of order.

Many collectors don't mind getting docIDs out of order, so it's important to return true here.

Specified by:

acceptsDocsOutOfOrder in class Collector