org.apache.lucene.search

Interface Collector

All Known Implementing Classes:

CachingCollector, EarlyTerminatingSortingCollector, FilterCollector, MultiCollector, MultiCollectorManager.Collectors, PositiveScoresOnlyCollector, SimpleCollector, TimeLimitingCollector, TopDocsCollector, TopFieldCollector, TopScoreDocCollector, TotalHitCountCollector

public interface Collector

Expert: Collectors are primarily meant to be used to gather raw results from a search, and implement sorting or custom result filtering, collation, etc.

Lucene's core collectors are derived from Collector and SimpleCollector. Likely your application can use one of these classes, or subclass TopDocsCollector, instead of implementing Collector directly:

• TopDocsCollector is an abstract base class that assumes you will retrieve the top N docs, according to some criteria, after collection is done.
• TopScoreDocCollector is a concrete subclass TopDocsCollector and sorts according to score + docID. This is used internally by the IndexSearcher search methods that do not take an explicit Sort. It is likely the most frequently used collector.
• TopFieldCollector subclasses TopDocsCollector and sorts according to a specified Sort object (sort by field). This is used internally by the IndexSearcher search methods that take an explicit Sort.
• TimeLimitingCollector, which wraps any other Collector and aborts the search if it's taken too much time.
• PositiveScoresOnlyCollector wraps any other Collector and prevents collection of hits whose score is <= 0.0

WARNING: This API is experimental and might change in incompatible ways in the next release.

Method Summary

Modifier and Type	Method and Description
LeafCollector	getLeafCollector(LeafReaderContext context) Create a new collector to collect the given context.
boolean	needsScores() Indicates if document scores are needed by this collector.

Method Detail

getLeafCollector

LeafCollector getLeafCollector(LeafReaderContext context)
                        throws IOException

Create a new collector to collect the given context.

Parameters:

context - next atomic reader context

Throws:

IOException

needsScores

boolean needsScores()

Indicates if document scores are needed by this collector.

Returns:

true if scores are needed.