Package org.apache.lucene.search

Class TopFieldCollector

java.lang.Object
org.apache.lucene.search.Collector
org.apache.lucene.search.TopDocsCollector<FieldValueHitQueue.Entry>
org.apache.lucene.search.TopFieldCollector
public abstract class TopFieldCollector extends TopDocsCollector<FieldValueHitQueue.Entry>
A Collector that sorts by SortField using FieldComparators.

See the create(org.apache.lucene.search.Sort, int, boolean, boolean, boolean, boolean) method for instantiating a TopFieldCollector.

  • Method Details

    • create

      public static TopFieldCollector create(Sort sort, int numHits, boolean fillFields, boolean trackDocScores, boolean trackMaxScore, boolean docsScoredInOrder) throws IOException
      Creates a new TopFieldCollector from the given arguments.

      NOTE: The instances returned by this method pre-allocate a full array of length numHits.

      Parameters:
      sort - the sort criteria (SortFields).
      numHits - the number of results to collect.
      fillFields - specifies whether the actual field values should be returned on the results (FieldDoc).
      trackDocScores - specifies whether document scores should be tracked and set on the results. Note that if set to false, then the results' scores will be set to Float.NaN. Setting this to true affects performance, as it incurs the score computation on each competitive result. Therefore if document scores are not required by the application, it is recommended to set it to false.
      trackMaxScore - specifies whether the query's maxScore should be tracked and set on the resulting TopDocs. Note that if set to false, TopDocs.getMaxScore() returns Float.NaN. Setting this to true affects performance as it incurs the score computation on each result. Also, setting this true automatically sets trackDocScores to true as well.
      docsScoredInOrder - specifies whether documents are scored in doc Id order or not by the given Scorer in Collector.setScorer(Scorer).
      Returns:
      a TopFieldCollector instance which will sort the results by the sort criteria.
      Throws:
      IOException - if there is a low-level I/O error

    • create

      public static TopFieldCollector create(Sort sort, int numHits, FieldDoc after, boolean fillFields, boolean trackDocScores, boolean trackMaxScore, boolean docsScoredInOrder) throws IOException
      Creates a new TopFieldCollector from the given arguments.

      NOTE: The instances returned by this method pre-allocate a full array of length numHits.

      Parameters:
      sort - the sort criteria (SortFields).
      numHits - the number of results to collect.
      after - only hits after this FieldDoc will be collected
      fillFields - specifies whether the actual field values should be returned on the results (FieldDoc).
      trackDocScores - specifies whether document scores should be tracked and set on the results. Note that if set to false, then the results' scores will be set to Float.NaN. Setting this to true affects performance, as it incurs the score computation on each competitive result. Therefore if document scores are not required by the application, it is recommended to set it to false.
      trackMaxScore - specifies whether the query's maxScore should be tracked and set on the resulting TopDocs. Note that if set to false, TopDocs.getMaxScore() returns Float.NaN. Setting this to true affects performance as it incurs the score computation on each result. Also, setting this true automatically sets trackDocScores to true as well.
      docsScoredInOrder - specifies whether documents are scored in doc Id order or not by the given Scorer in Collector.setScorer(Scorer).
      Returns:
      a TopFieldCollector instance which will sort the results by the sort criteria.
      Throws:
      IOException - if there is a low-level I/O error

    • populateResults

      protected void populateResults(ScoreDoc[] results, int howMany)
      Description copied from class: TopDocsCollector
      Populates the results array with the ScoreDoc instances. This can be overridden in case a different ScoreDoc type should be returned.
      Overrides:
      populateResults in class TopDocsCollector<FieldValueHitQueue.Entry>

    • newTopDocs

      protected TopDocs newTopDocs(ScoreDoc[] results, int start)
      Description copied from class: TopDocsCollector
      Returns a TopDocs instance containing the given results. If results is null it means there are no results to return, either because there were 0 calls to collect() or because the arguments to topDocs were invalid.
      Overrides:
      newTopDocs in class TopDocsCollector<FieldValueHitQueue.Entry>

    • acceptsDocsOutOfOrder

      public boolean acceptsDocsOutOfOrder()
      Description copied from class: Collector
      Return true if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to Collector.collect(int).

      Most Lucene Query implementations will visit matching docIDs in order. However, some queries (currently limited to certain cases of BooleanQuery) can achieve faster searching if the Collector allows them to deliver the docIDs out of order.

      Many collectors don't mind getting docIDs out of order, so it's important to return true here.

      Specified by:
      acceptsDocsOutOfOrder in class Collector