org.apache.lucene.facet.search
Class FacetResultsHandler

java.lang.Object
  extended by 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
protected  FacetRequest facetRequest
          Facet request served by this handler.
protected  TaxonomyReader taxonomyReader
          Taxonomy for which facets are handled
 
Constructor Summary
FacetResultsHandler(TaxonomyReader taxonomyReader, FacetRequest facetRequest)
          Create a faceted search handler.
 
Method Summary
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


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