org.apache.lucene.facet.search
Class StandardFacetsAccumulator

java.lang.Object
  org.apache.lucene.facet.search.FacetsAccumulator
      org.apache.lucene.facet.search.StandardFacetsAccumulator

Direct Known Subclasses:

AdaptiveFacetsAccumulator, SamplingAccumulator, SamplingWrapper

public class StandardFacetsAccumulator
extends FacetsAccumulator

Standard implementation for FacetsAccumulator, utilizing partitions to save on memory.

Why partitions? Because if there are say 100M categories out of which only top K are required, we must first compute value for all 100M categories (going over all documents) and only then could we select top K. This is made easier on memory by working in partitions of distinct categories: Once a values for a partition are found, we take the top K for that partition and work on the next partition, them merge the top K of both, and so forth, thereby computing top K with RAM needs for the size of a single partition rather than for the size of all the 100M categories.

Decision on partitions size is done at indexing time, and the facet information for each partition is maintained separately.

Implementation detail: Since facets information of each partition is maintained in a separate "category list", we can be more efficient at search time, because only the facet info for a single partition need to be read while processing that partition.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

static double	DEFAULT_COMPLEMENT_THRESHOLD Default threshold for using the complements optimization.
static double	DISABLE_COMPLEMENT Passing this to setComplementThreshold(double) will disable using complement optimization.
static double	FORCE_COMPLEMENT Passing this to setComplementThreshold(double) will force using complement optimization.
protected boolean	isUsingComplements
protected int	maxPartitions
protected int	partitionSize

Fields inherited from class org.apache.lucene.facet.search.FacetsAccumulator

facetArrays, indexReader, searchParams, taxonomyReader

Constructor Summary

StandardFacetsAccumulator(FacetSearchParams searchParams, IndexReader indexReader, TaxonomyReader taxonomyReader)

StandardFacetsAccumulator(FacetSearchParams searchParams, IndexReader indexReader, TaxonomyReader taxonomyReader, FacetArrays facetArrays)

Method Summary

List<FacetResult>	accumulate(List<FacetsCollector.MatchingDocs> matchingDocs) Used by FacetsCollector to build the list of facet results that match the facet requests that were given in the constructor.
List<FacetResult>	accumulate(ScoredDocIDs docids)
protected ScoredDocIDs	actualDocsToAccumulate(ScoredDocIDs docids) Set the actual set of documents over which accumulation should take place.
protected PartitionsFacetResultsHandler	createFacetResultsHandler(FacetRequest fr) Creates a FacetResultsHandler that matches the given FacetRequest.
protected HashMap<CategoryListIterator,Aggregator>	getCategoryListMap(FacetArrays facetArrays, int partition) Create an Aggregator and a CategoryListIterator for each and every FacetRequest.
double	getComplementThreshold() Returns the complement threshold.
protected double	getTotalCountsFactor() Expert: factor by which counts should be multiplied when initializing the count arrays from total counts.
boolean	isUsingComplements() Returns true if complements are enabled.
protected boolean	mayComplement() check if all requests are complementable
void	setComplementThreshold(double complementThreshold) Set the complement threshold.
protected boolean	shouldComplement(ScoredDocIDs docids) Check if it is worth to use complements

Methods inherited from class org.apache.lucene.facet.search.FacetsAccumulator

create, getAggregator, getCategoryLists

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_COMPLEMENT_THRESHOLD

public static final double DEFAULT_COMPLEMENT_THRESHOLD

Default threshold for using the complements optimization. If accumulating facets for a document set larger than this ratio of the index size than perform the complement optimization.

See Also:

for more info on the complements optimization., Constant Field Values

DISABLE_COMPLEMENT

public static final double DISABLE_COMPLEMENT

Passing this to setComplementThreshold(double) will disable using complement optimization.

See Also:

Constant Field Values

FORCE_COMPLEMENT

public static final double FORCE_COMPLEMENT

Passing this to setComplementThreshold(double) will force using complement optimization.

See Also:

Constant Field Values

partitionSize

protected int partitionSize

maxPartitions

protected int maxPartitions

isUsingComplements

protected boolean isUsingComplements

Constructor Detail

StandardFacetsAccumulator

public StandardFacetsAccumulator(FacetSearchParams searchParams,
                                 IndexReader indexReader,
                                 TaxonomyReader taxonomyReader)

StandardFacetsAccumulator

public StandardFacetsAccumulator(FacetSearchParams searchParams,
                                 IndexReader indexReader,
                                 TaxonomyReader taxonomyReader,
                                 FacetArrays facetArrays)

Method Detail

accumulate

public List<FacetResult> accumulate(ScoredDocIDs docids)
                             throws IOException

Throws:

IOException

mayComplement

protected boolean mayComplement()

check if all requests are complementable

createFacetResultsHandler

protected PartitionsFacetResultsHandler createFacetResultsHandler(FacetRequest fr)

Description copied from class: FacetsAccumulator

Creates a FacetResultsHandler that matches the given FacetRequest.

Overrides:

createFacetResultsHandler in class FacetsAccumulator

actualDocsToAccumulate

protected ScoredDocIDs actualDocsToAccumulate(ScoredDocIDs docids)
                                       throws IOException

Set the actual set of documents over which accumulation should take place.

Allows to override the set of documents to accumulate for. Invoked just before actual accumulating starts. From this point that set of documents remains unmodified. Default implementation just returns the input unchanged.

Parameters:

docids - candidate documents to accumulate for

Returns:

actual documents to accumulate for

Throws:

IOException

shouldComplement

protected boolean shouldComplement(ScoredDocIDs docids)

Check if it is worth to use complements

getTotalCountsFactor

protected double getTotalCountsFactor()

Expert: factor by which counts should be multiplied when initializing the count arrays from total counts. Default implementation for this returns 1, which is a no op.

Returns:

a factor by which total counts should be multiplied

getCategoryListMap

protected HashMap<CategoryListIterator,Aggregator> getCategoryListMap(FacetArrays facetArrays,
                                                                      int partition)
                                                               throws IOException

Create an Aggregator and a CategoryListIterator for each and every FacetRequest. Generating a map, matching each categoryListIterator to its matching aggregator.

If two CategoryListIterators are served by the same aggregator, a single aggregator is returned for both. NOTE: If a given category list iterator is needed with two different aggregators (e.g counting and association) - an exception is thrown as this functionality is not supported at this time.

Throws:

IOException

accumulate

public List<FacetResult> accumulate(List<FacetsCollector.MatchingDocs> matchingDocs)
                             throws IOException

Description copied from class: FacetsAccumulator

Used by FacetsCollector to build the list of facet results that match the facet requests that were given in the constructor.

Overrides:

accumulate in class FacetsAccumulator

Parameters:

matchingDocs - the documents that matched the query, per-segment.

Throws:

IOException

getComplementThreshold

public double getComplementThreshold()

Returns the complement threshold.

See Also:

setComplementThreshold(double)

setComplementThreshold

public void setComplementThreshold(double complementThreshold)

Set the complement threshold. This threshold will dictate whether the complements optimization is applied. The optimization is to count for less documents. It is useful when the same FacetSearchParams are used for varying sets of documents. The first time complements is used the "total counts" are computed - counting for all the documents in the collection. Then, only the complementing set of documents is considered, and used to decrement from the overall counts, thereby walking through less documents, which is faster.

For the default settings see DEFAULT_COMPLEMENT_THRESHOLD.

To forcing complements in all cases pass FORCE_COMPLEMENT. This is mostly useful for testing purposes, as forcing complements when only tiny fraction of available documents match the query does not make sense and would incur performance degradations.

To disable complements pass DISABLE_COMPLEMENT.

Parameters:

complementThreshold - the complement threshold to set

See Also:

getComplementThreshold()

isUsingComplements

public boolean isUsingComplements()

Returns true if complements are enabled.