org.apache.lucene.search

Class MultiCollector

java.lang.Object

org.apache.lucene.search.MultiCollector

All Implemented Interfaces:

Collector

public class MultiCollector
extends Object
implements Collector

A Collector which allows running a search with several Collectors. It offers a static wrap(org.apache.lucene.search.Collector...) method which accepts a list of collectors and wraps them with MultiCollector, while filtering out the null null ones.

NOTE:When mixing collectors that want to skip low-scoring hits (ScoreMode.TOP_SCORES) with ones that require to see all hits, such as mixing TopScoreDocCollector and TotalHitCountCollector, it should be faster to run the query twice, once for each collector, rather than using this wrapper on a single search.

Method Summary

Modifier and Type	Method and Description
LeafCollector	getLeafCollector(LeafReaderContext context) Create a new collector to collect the given context.
ScoreMode	scoreMode() Indicates what features are required from the scorer.
static Collector	wrap(Collector... collectors) See wrap(Iterable).
static Collector	wrap(Iterable<? extends Collector> collectors) Wraps a list of Collectors with a MultiCollector.

Methods inherited from class java.lang.Object

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

Method Detail

wrap

public static Collector wrap(Collector... collectors)

See wrap(Iterable).

wrap

public static Collector wrap(Iterable<? extends Collector> collectors)

Wraps a list of Collectors with a MultiCollector. This method works as follows:

• Filters out the null collectors, so they are not used during search time.
• If the input contains 1 real collector (i.e. non-null ), it is returned.
• Otherwise the method returns a MultiCollector which wraps the non-null ones.

Throws:

IllegalArgumentException - if either 0 collectors were input, or all collectors are null.

scoreMode

public ScoreMode scoreMode()

Description copied from interface: Collector

Indicates what features are required from the scorer.

Specified by:

scoreMode in interface Collector

getLeafCollector

public LeafCollector getLeafCollector(LeafReaderContext context)
                               throws IOException

Description copied from interface: Collector

Create a new collector to collect the given context.

Specified by:

getLeafCollector in interface Collector

Parameters:

context - next atomic reader context

Throws:

IOException