org.apache.lucene.facet.search

Class FacetResultsHandler

java.lang.Object

org.apache.lucene.facet.search.FacetResultsHandler

Direct Known Subclasses:

TopKFacetResultsHandler, TopKInEachNodeHandler

public abstract class FacetResultsHandler
extends Object

Handler for facet results.

The facet results handler provided by the FacetRequest to a FacetsAccumulator.

First it is used by FacetsAccumulator to obtain a temporary facet result for each partition and to merge results of several partitions.

Later the accumulator invokes the handler to render the results, creating FacetResult objects.

Last the accumulator invokes the handler to label final results.

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

Field Summary

Fields

Modifier and Type	Field and Description
protected FacetRequest	facetRequest Facet request served by this handler.
protected TaxonomyReader	taxonomyReader Taxonomy for which facets are handled

Constructor Summary

Constructors

Constructor and Description
FacetResultsHandler(TaxonomyReader taxonomyReader, FacetRequest facetRequest) Create a faceted search handler.

Method Summary

Methods

Modifier and Type	Method and Description
abstract IntermediateFacetResult	fetchPartitionResult(FacetArrays arrays, int offset) Fetch results of a single partition, given facet arrays for that partition, and based on the matching documents and faceted search parameters.
FacetRequest	getFacetRequest() Return the facet request served by this handler.
TaxonomyReader	getTaxonomyReader() Return taxonomy reader used for current facets accumulation operation.
protected boolean	isSelfPartition(int ordinal, FacetArrays facetArrays, int offset) Check if an array contains the partition which contains ordinal
abstract void	labelResult(FacetResult facetResult) Label results according to settings in FacetRequest, such as FacetRequest.getNumLabel().
abstract IntermediateFacetResult	mergeResults(IntermediateFacetResult... tmpResults) Merge results of several facet partitions.
abstract FacetResult	rearrangeFacetResult(FacetResult facetResult) Perform any rearrangement as required on a facet result that has changed after it was rendered.
abstract FacetResult	renderFacetResult(IntermediateFacetResult tmpResult) Create a facet result from the temporary result.

Methods inherited from class java.lang.Object

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

Field Detail

taxonomyReader

protected final TaxonomyReader taxonomyReader

Taxonomy for which facets are handled

facetRequest

protected final FacetRequest facetRequest

Facet request served by this handler.

Constructor Detail

FacetResultsHandler

public FacetResultsHandler(TaxonomyReader taxonomyReader,
                   FacetRequest facetRequest)

Create a faceted search handler.

Parameters:

taxonomyReader - See getTaxonomyReader().

facetRequest - See getFacetRequest().

Method Detail

fetchPartitionResult

public abstract IntermediateFacetResult fetchPartitionResult(FacetArrays arrays,
                                           int offset)
                                                      throws IOException

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

Parameters:

arrays - 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 abstract IntermediateFacetResult mergeResults(IntermediateFacetResult... tmpResults)
                                              throws IOException,
                                                     ClassCastException,
                                                     IllegalArgumentException

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.

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.

ClassCastException - if the temporary result passed was not created by this handler

IllegalArgumentException - if passed facetResults do not have the same FacetRequest

See Also:

IntermediateFacetResult.getFacetRequest()

renderFacetResult

public abstract FacetResult renderFacetResult(IntermediateFacetResult tmpResult)
                                       throws IOException

Create a facet result from the temporary result.

Parameters:

tmpResult - temporary result to be rendered as a FacetResult

Throws:

IOException - on error.

rearrangeFacetResult

public abstract FacetResult rearrangeFacetResult(FacetResult facetResult)

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.

Parameters:

facetResult - result to be rearranged.

See Also:

FacetResultNode.setValue(double)

labelResult

public abstract void labelResult(FacetResult facetResult)
                          throws IOException

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

Parameters:

facetResult - facet result to be labeled.

Throws:

IOException - on error

getTaxonomyReader

public final TaxonomyReader getTaxonomyReader()

Return taxonomy reader used for current facets accumulation operation.

getFacetRequest

public final FacetRequest getFacetRequest()

Return the facet request served by this handler.

isSelfPartition

protected boolean isSelfPartition(int ordinal,
                      FacetArrays facetArrays,
                      int offset)

Check if an array contains the partition which contains ordinal

Parameters:

ordinal - checked facet

facetArrays - facet arrays for the certain partition

offset - offset in input arrays where partition starts