org.apache.lucene.facet.search

Class TopKFacetResultsHandler

java.lang.Object

org.apache.lucene.facet.search.FacetResultsHandler

org.apache.lucene.facet.search.TopKFacetResultsHandler

public class TopKFacetResultsHandler
extends FacetResultsHandler

Generate Top-K results for a particular FacetRequest.

K is global (among all results) and is defined by FacetRequest.getNumResults().

Note: Values of 0 (Zero) are ignored by this results handler.

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

Field Summary

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

facetRequest, taxonomyReader

Constructor Summary

Constructors

Constructor and Description
TopKFacetResultsHandler(TaxonomyReader taxonomyReader, FacetRequest facetRequest) Construct top-K results handler.

Method Summary

Methods

Modifier and Type	Method and Description
IntermediateFacetResult	fetchPartitionResult(FacetArrays facetArrays, int offset) Fetch results of a single partition, given facet arrays for that partition, and based on the matching documents and faceted search parameters.
void	labelResult(FacetResult facetResult) Label results according to settings in FacetRequest, such as FacetRequest.getNumLabel().
IntermediateFacetResult	mergeResults(IntermediateFacetResult... tmpResults) Merge results of several facet partitions.
FacetResult	rearrangeFacetResult(FacetResult facetResult) Perform any rearrangement as required on a facet result that has changed after it was rendered.
FacetResult	renderFacetResult(IntermediateFacetResult tmpResult) Create a facet result from the temporary result.

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

getFacetRequest, getTaxonomyReader, isSelfPartition

Methods inherited from class java.lang.Object

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

Constructor Detail

TopKFacetResultsHandler

public TopKFacetResultsHandler(TaxonomyReader taxonomyReader,
                       FacetRequest facetRequest)

Construct top-K results handler.

Parameters:

taxonomyReader - taxonomy reader

facetRequest - facet request being served

Method Detail

fetchPartitionResult

public IntermediateFacetResult fetchPartitionResult(FacetArrays facetArrays,
                                           int offset)
                                             throws IOException

Description copied from class: FacetResultsHandler

Fetch results of a single partition, given facet arrays for that partition, and based on the matching documents and faceted search parameters.

Specified by:

fetchPartitionResult in class FacetResultsHandler

Parameters:

facetArrays - facet arrays for the certain partition

offset - offset in input arrays where partition starts

Returns:

temporary facet result, potentially, to be passed back to this result handler for merging, or null in case that constructor parameter, facetRequest, requests an illegal FacetResult, like, e.g., a root node category path that does not exist in constructor parameter taxonomyReader .

Throws:

IOException - on error

mergeResults

public IntermediateFacetResult mergeResults(IntermediateFacetResult... tmpResults)
                                     throws IOException

Description copied from class: FacetResultsHandler

Merge results of several facet partitions. Logic of the merge is undefined and open for interpretations. For example, a merge implementation could keep top K results. Passed IntermediateFacetResult must be ones that were created by this handler otherwise a ClassCastException is thrown. In addition, all passed IntermediateFacetResult must have the same FacetRequest otherwise an IllegalArgumentException is thrown.

Specified by:

mergeResults in class FacetResultsHandler

Parameters:

tmpResults - one or more temporary results created by this handler.

Returns:

temporary facet result that represents to union, as specified by this handler, of the input temporary facet results.

Throws:

IOException - on error.

See Also:

IntermediateFacetResult.getFacetRequest()

renderFacetResult

public FacetResult renderFacetResult(IntermediateFacetResult tmpResult)

Description copied from class: FacetResultsHandler

Create a facet result from the temporary result.

Specified by:

renderFacetResult in class FacetResultsHandler

Parameters:

tmpResult - temporary result to be rendered as a FacetResult

rearrangeFacetResult

public FacetResult rearrangeFacetResult(FacetResult facetResult)

Description copied from class: FacetResultsHandler

Perform any rearrangement as required on a facet result that has changed after it was rendered.

Possible use case: a sampling facets accumulator invoked another other facets accumulator on a sample set of documents, obtained rendered facet results, fixed their counts, and now it is needed to sort the results differently according to the fixed counts.

Specified by:

rearrangeFacetResult in class FacetResultsHandler

Parameters:

facetResult - result to be rearranged.

See Also:

FacetResultNode.setValue(double)

labelResult

public void labelResult(FacetResult facetResult)
                 throws IOException

Description copied from class: FacetResultsHandler

Label results according to settings in FacetRequest, such as FacetRequest.getNumLabel(). Usually invoked by FacetsAccumulator.accumulate(ScoredDocIDs)

Specified by:

labelResult in class FacetResultsHandler

Parameters:

facetResult - facet result to be labeled.

Throws:

IOException - on error