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

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

FacetsCollector.MatchingDocs

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.
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, getKeepScores, scoreMode, search, search, search, searchAfter, searchAfter, searchAfter, 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.LeafCollector

competitiveIterator

Constructor Detail

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 Detail

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.

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.