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## org.apache.lucene.facet.search
Class TopKFacetResultsHandler

    java.lang.Object
      org.apache.lucene.facet.search.FacetResultsHandler
          org.apache.lucene.facet.partitions.PartitionsFacetResultsHandler
              org.apache.lucene.facet.search.TopKFacetResultsHandler

    public class TopKFacetResultsHandler

extends PartitionsFacetResultsHandler

Generate Top-K results for a particular `FacetRequest`. K is global (among all results) and is defined by `FacetRequest.numResults`.

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
`facetArrays, facetRequest, taxonomyReader`

Constructor Summary
`TopKFacetResultsHandler(TaxonomyReader taxonomyReader, FacetRequest facetRequest, FacetArrays facetArrays)` Construct top-K results handler.

Method Summary
`IntermediateFacetResult` | `fetchPartitionResult(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.partitions.PartitionsFacetResultsHandler
`compute, 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,
                                   FacetArrays facetArrays)

  Construct top-K results handler.

  Parameters:
    `taxonomyReader` - taxonomy reader
    `facetRequest` - facet request being served

Method Detail

### fetchPartitionResult

    public IntermediateFacetResult fetchPartitionResult(int offset)
                                                 throws IOException

  Description copied from class: `PartitionsFacetResultsHandler`
  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 `PartitionsFacetResultsHandler`
  Parameters:
    `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: `PartitionsFacetResultsHandler`
  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 `PartitionsFacetResultsHandler`
  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: `PartitionsFacetResultsHandler`
  Create a facet result from the temporary result.

  Specified by:
    `renderFacetResult` in class `PartitionsFacetResultsHandler`
  Parameters:
    `tmpResult` - temporary result to be rendered as a `FacetResult`

### rearrangeFacetResult

    public FacetResult rearrangeFacetResult(FacetResult facetResult)

  Description copied from class: `PartitionsFacetResultsHandler`
  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 `PartitionsFacetResultsHandler`
  Parameters:
    `facetResult` - result to be rearranged.
  See Also:
    `FacetResultNode.value`

### labelResult

    public void labelResult(FacetResult facetResult)
                     throws IOException

  Description copied from class: `PartitionsFacetResultsHandler`
  Label results according to settings in `FacetRequest`, such as `FacetRequest.getNumLabel()`. Usually invoked by `StandardFacetsAccumulator.accumulate(ScoredDocIDs)`

  Specified by:
    `labelResult` in class `PartitionsFacetResultsHandler`
  Parameters:
    `facetResult` - facet result to be labeled.
  Throws:
    `IOException` - on error

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