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.
  `static CollectorManager<RandomSamplingFacetsCollector,RandomSamplingFacetsCollector>`
  `createManager(int sampleSize, long seed)`
  Creates a `CollectorManager` for concurrent random sampling through `RandomSamplingFacetsCollector`
  `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, collectRange, competitiveIterator`

- ## 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.

  - ### 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`