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 Summary

Modifier and Type	Method	Description
boolean	acceptsDocsOutOfOrder()	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).
static TopFieldCollector	create(Sort sort, int numHits, boolean fillFields, boolean trackDocScores, boolean trackMaxScore, boolean docsScoredInOrder)	Creates a new TopFieldCollector from the given arguments.
static TopFieldCollector	create(Sort sort, int numHits, FieldDoc after, boolean fillFields, boolean trackDocScores, boolean trackMaxScore, boolean docsScoredInOrder)	Creates a new TopFieldCollector from the given arguments.

Methods inherited from class org.apache.lucene.search.TopDocsCollector

getTotalHits, topDocs, topDocs, topDocs

Methods inherited from class org.apache.lucene.search.Collector

collect, setNextReader, setScorer

Methods inherited from class java.lang.Object

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

Method Detail

create

public static TopFieldCollector create(Sort sort,
                                       int numHits,
                                       boolean fillFields,
                                       boolean trackDocScores,
                                       boolean trackMaxScore,
                                       boolean docsScoredInOrder)
                                throws java.io.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:

java.io.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 java.io.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:

java.io.IOException - if there is a low-level I/O error

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