java.lang.Object
- org.apache.lucene.search.Collector
- - org.apache.lucene.facet.FacetsCollector

```
public class FacetsCollector
extends Collector
```
Collects hits for subsequent faceting. Once you've run a search and collect hits into this, instantiate one of the Facets subclasses to do the facet counting. Use the search utility methods to perform an "ordinary" search but also collect into a Collector.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class FacetsCollector.MatchingDocs
Holds the documents that were matched in the AtomicReaderContext.

Constructor Summary

Constructors
Constructor	Description
`FacetsCollector()`	Default constructor
`FacetsCollector(boolean keepScores)`	Create this; if `keepScores` is true then a float[] is allocated to hold score of all hits.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`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.
`boolean`	`getKeepScores()`	True if scores were saved.
`List<FacetsCollector.MatchingDocs>`	`getMatchingDocs()`	Returns the documents matched by the query, one `FacetsCollector.MatchingDocs` per visited segment.
`static TopDocs`	`search(IndexSearcher searcher, Query q, int n, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`static TopDocs`	`search(IndexSearcher searcher, Query q, Filter filter, int n, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`static TopFieldDocs`	`search(IndexSearcher searcher, Query q, Filter filter, int n, Sort sort, boolean doDocScores, boolean doMaxScore, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`static TopFieldDocs`	`search(IndexSearcher searcher, Query q, Filter filter, int n, Sort sort, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`TopDocs`	`searchAfter(IndexSearcher searcher, ScoreDoc after, Query q, int n, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`static TopDocs`	`searchAfter(IndexSearcher searcher, ScoreDoc after, Query q, Filter filter, int n, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`static TopDocs`	`searchAfter(IndexSearcher searcher, ScoreDoc after, Query q, Filter filter, int n, Sort sort, boolean doDocScores, boolean doMaxScore, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`static TopDocs`	`searchAfter(IndexSearcher searcher, ScoreDoc after, Query q, Filter filter, int n, Sort sort, Collector fc)`	Utility method, to search and also collect all hits into the provided `Collector`.
`void`	`setNextReader(AtomicReaderContext context)`	Called before collecting from each `AtomicReaderContext`.
`void`	`setScorer(Scorer scorer)`	Called before successive calls to `Collector.collect(int)`.

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- FacetsCollector
```
public FacetsCollector()
```
  Default constructor
- FacetsCollector
```
public FacetsCollector(boolean keepScores)
```
  Create this; if keepScores is true then a float[] is allocated to hold score of all hits.

Method Detail

getKeepScores
```
public final boolean getKeepScores()
```
True if scores were saved.

getMatchingDocs
```
public List<FacetsCollector.MatchingDocs> getMatchingDocs()
```
Returns the documents matched by the query, one FacetsCollector.MatchingDocs per visited segment.

acceptsDocsOutOfOrder
```
public final 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

collect
```
public final 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: The collection of the current segment can be terminated by throwing a CollectionTerminatedException. In this case, the last docs of the current AtomicReaderContext 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 class Collector

Throws:

IOException

setScorer
```
public final 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

setNextReader
```
public final void setNextReader(AtomicReaderContext context)
                         throws IOException
```
Description copied from class: Collector

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

Specified by:

setNextReader in class Collector

Parameters:

context - next atomic reader context

Throws:

IOException