Module org.apache.lucene.facet

Package org.apache.lucene.facet

Class RandomSamplingFacetsCollector

java.lang.Object

org.apache.lucene.search.SimpleCollector

org.apache.lucene.facet.FacetsCollector

org.apache.lucene.facet.RandomSamplingFacetsCollector

All Implemented Interfaces:

Collector, LeafCollector

Direct Known Subclasses:

RandomSamplingFacetsCollector.ReducedRandomSamplingFacetsCollector

public class RandomSamplingFacetsCollector
extends FacetsCollector

Collects hits for subsequent faceting, using sampling if needed. Once you've run a search and collect hits into this, instantiate one of the Facets subclasses to do the facet counting. Note that this collector does not collect the scores of matching docs (i.e. FacetsCollector.MatchingDocs.scores()) is null.

If you require the original set of hits, you can call getOriginalMatchingDocs(). Also, since the counts of the top-facets is based on the sampled set, you can amortize the counts by calling amortizeFacetCounts(org.apache.lucene.facet.FacetResult, org.apache.lucene.facet.FacetsConfig, org.apache.lucene.search.IndexSearcher).

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	RandomSamplingFacetsCollector.ReducedRandomSamplingFacetsCollector
private static class	RandomSamplingFacetsCollector.XORShift64Random	Faster alternative for java.util.Random, inspired by http://dmurphy747.wordpress.com/2011/03/23/xorshift-vs-random- performance-in-java/

Nested classes/interfaces inherited from class org.apache.lucene.facet.FacetsCollector

FacetsCollector.MatchingDocs

Field Summary

Fields

Modifier and Type	Field	Description
private int	leftoverBin
private int	leftoverIndex
private static final int	NOT_CALCULATED
private final RandomSamplingFacetsCollector.XORShift64Random	random
private List<FacetsCollector.MatchingDocs>	sampledDocs
private final int	sampleSize
private double	samplingRate
private int	totalHits

Constructor Summary

Constructors

Constructor	Description
RandomSamplingFacetsCollector(int sampleSize)	Constructor with the given sample size and default seed.
RandomSamplingFacetsCollector(int sampleSize, long seed)	Constructor with the given sample size and seed.

Method Summary

Modifier and Type	Method	Description
FacetResult	amortizeFacetCounts(FacetResult res, FacetsConfig config, IndexSearcher searcher)	Note: if you use a counting Facets implementation, you can amortize the sampled counts by calling this method.
static CollectorManager<RandomSamplingFacetsCollector,RandomSamplingFacetsCollector>	createManager(int sampleSize, long seed)	Creates a CollectorManager for concurrent random sampling through RandomSamplingFacetsCollector
private FacetsCollector.MatchingDocs	createSample(FacetsCollector.MatchingDocs docs)	Create a sampled of the given hits.
private List<FacetsCollector.MatchingDocs>	createSampledDocs(List<FacetsCollector.MatchingDocs> matchingDocsList)	Create a sampled copy of the matching documents list.
List<FacetsCollector.MatchingDocs>	getMatchingDocs()	Returns the sampled list of the matching documents.
List<FacetsCollector.MatchingDocs>	getOriginalMatchingDocs()	Returns the original matching documents.
double	getSamplingRate()	Returns the sampling rate that was used.

Methods inherited from class org.apache.lucene.facet.FacetsCollector

collect, doSetNextReader, finish, getKeepScores, scoreMode, setScorer

Methods inherited from class org.apache.lucene.search.SimpleCollector

getLeafCollector

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.lucene.search.Collector

setWeight

Methods inherited from interface org.apache.lucene.search.LeafCollector

collect, competitiveIterator

Field Details

NOT_CALCULATED

private static final int NOT_CALCULATED

See Also:

• Constant Field Values

sampleSize

private final int sampleSize

random

private final RandomSamplingFacetsCollector.XORShift64Random random

samplingRate

private double samplingRate

sampledDocs

private List<FacetsCollector.MatchingDocs> sampledDocs

totalHits

private int totalHits

leftoverBin

private int leftoverBin

leftoverIndex

private int leftoverIndex

Constructor Details

RandomSamplingFacetsCollector

public RandomSamplingFacetsCollector(int sampleSize)

Constructor with the given sample size and default seed.

See Also:

• RandomSamplingFacetsCollector(int, long)

RandomSamplingFacetsCollector

public RandomSamplingFacetsCollector(int sampleSize,
 long seed)

Constructor with the given sample size and seed.

Parameters:

sampleSize - The preferred sample size. If the number of hits is greater than the size, sampling will be done using a sample ratio of sampling size / totalN. For example: 1000 hits, sample size = 10 results in samplingRatio of 0.01. If the number of hits is lower, no sampling is done at all

seed - The random seed. If 0 then a seed will be chosen for you.

Method Details

getMatchingDocs

public List<FacetsCollector.MatchingDocs> getMatchingDocs()

Returns the sampled list of the matching documents. Note that a FacetsCollector.MatchingDocs instance is returned per segment, even if no hits from that segment are included in the sampled set.

Note: One or more of the MatchingDocs might be empty (not containing any hits) as result of sampling.

Note: MatchingDocs.totalHits is copied from the original MatchingDocs, scores is set to null

Overrides:

getMatchingDocs in class FacetsCollector

getOriginalMatchingDocs

public List<FacetsCollector.MatchingDocs> getOriginalMatchingDocs()

Returns the original matching documents.

createSampledDocs

private List<FacetsCollector.MatchingDocs> createSampledDocs(List<FacetsCollector.MatchingDocs> matchingDocsList)

Create a sampled copy of the matching documents list.

createSample

private FacetsCollector.MatchingDocs createSample(FacetsCollector.MatchingDocs docs)

Create a sampled of the given hits.

amortizeFacetCounts

public FacetResult amortizeFacetCounts(FacetResult res,
 FacetsConfig config,
 IndexSearcher searcher)
                                throws IOException

Note: if you use a counting Facets implementation, you can amortize the sampled counts by calling this method. Uses the FacetsConfig and the IndexSearcher to determine the upper bound for each facet value.

Throws:

IOException

getSamplingRate

public double getSamplingRate()

Returns the sampling rate that was used.

createManager

public static CollectorManager<RandomSamplingFacetsCollector,RandomSamplingFacetsCollector> createManager(int sampleSize,
 long seed)

Creates a CollectorManager for concurrent random sampling through RandomSamplingFacetsCollector