org.apache.lucene.index.sorter

Class EarlyTerminatingSortingCollector

java.lang.Object

org.apache.lucene.search.Collector

org.apache.lucene.index.sorter.EarlyTerminatingSortingCollector

public class EarlyTerminatingSortingCollector
extends Collector

A Collector that early terminates collection of documents on a per-segment basis, if the segment was sorted according to the given Sorter.

NOTE: the Collector detects sorted segments according to SortingMergePolicy, so it's best used in conjunction with it. Also, it collects up to a specified num docs from each segment, and therefore is mostly suitable for use in conjunction with collectors such as TopDocsCollector, and not e.g. TotalHitCountCollector.

NOTE: If you wrap a TopDocsCollector that sorts in the same order as the index order, the returned TopDocsCollector.topDocs() will be correct. However the total of hit count will be underestimated since not all matching documents will have been collected.

NOTE: This Collector uses Sorter.getID() to detect whether a segment was sorted with the same Sorter as the one given in EarlyTerminatingSortingCollector(Collector, Sorter, int). This has two implications:

• if Sorter.getID() is not implemented correctly and returns different identifiers for equivalent Sorters, this collector will not detect sorted segments,
• if you suddenly change the IndexWriter's SortingMergePolicy to sort according to another criterion and if both the old and the new Sorters have the same identifier, this Collector will incorrectly detect sorted segments.

Constructor Summary

Constructors

Constructor and Description
EarlyTerminatingSortingCollector(Collector in, Sorter sorter, int numDocsToCollect) Create a new EarlyTerminatingSortingCollector instance.

Method Summary

Modifier and Type	Method and 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).
void	collect(int doc) Called once for every document matching a query, with the unbased document number.
void	setNextReader(AtomicReaderContext context) Called before collecting from each AtomicReaderContext.
void	setScorer(Scorer scorer) Called before successive calls to Collector.collect(int).

Methods inherited from class java.lang.Object

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

Constructor Detail

EarlyTerminatingSortingCollector

public EarlyTerminatingSortingCollector(Collector in,
                                        Sorter sorter,
                                        int numDocsToCollect)

Create a new EarlyTerminatingSortingCollector instance.

Parameters:

in - the collector to wrap

sorter - the same sorter as the one which is used by IndexWriter's SortingMergePolicy

numDocsToCollect - the number of documents to collect on each segment. When wrapping a TopDocsCollector, this number should be the number of hits.

Method Detail

setScorer

public void setScorer(Scorer scorer)
               throws IOException

Description copied from class: Collector

Called before successive calls to Collector.collect(int). Implementations that need the score of the current document (passed-in to Collector.collect(int)), should save the passed-in Scorer and call scorer.score() when needed.

Specified by:

setScorer in class Collector

Throws:

IOException

collect

public void collect(int doc)
             throws IOException

Description copied from class: Collector

Called once for every document matching a query, with the unbased document number.

Note: The collection of the current segment can be terminated by throwing a CollectionTerminatedException. In this case, the last docs of the current AtomicReaderContext will be skipped and IndexSearcher will swallow the exception and continue collection with the next leaf.

Note: This is called in an inner search loop. For good search performance, implementations of this method should not call IndexSearcher.doc(int) or IndexReader.document(int) on every hit. Doing so can slow searches by an order of magnitude or more.

Specified by:

collect in class Collector

Throws:

IOException

setNextReader

public void setNextReader(AtomicReaderContext context)
                   throws IOException

Description copied from class: Collector

Called before collecting from each AtomicReaderContext. All doc ids in Collector.collect(int) will correspond to IndexReaderContext.reader(). Add AtomicReaderContext.docBase to the current IndexReaderContext.reader()'s internal document id to re-base ids in Collector.collect(int).

Specified by:

setNextReader in class Collector

Parameters:

context - next atomic reader context

Throws:

IOException

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