Lucene++ - a full-featured, c++ search engine
API Documentation


Loading...
Searching...
No Matches
Public Member Functions | Static Public Member Functions
Lucene::Collector Class Referenceabstract

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

#include <Collector.h>

+ Inheritance diagram for Lucene::Collector:

Public Member Functions

virtual ~Collector ()
 
virtual String getClassName ()
 
boost::shared_ptr< Collectorshared_from_this ()
 
virtual void setScorer (const ScorerPtr &scorer)=0
 Called before successive calls to collect(int32_t). Implementations that need the score of the current document (passed-in to collect(int32_t)), should save the passed-in Scorer and call scorer.score() when needed.
 
virtual void collect (int32_t doc)=0
 Called once for every document matching a query, with the unbased document number.
 
virtual void setNextReader (const IndexReaderPtr &reader, int32_t docBase)=0
 Called before collecting from each IndexReader. All doc ids in collect(int32_t) will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids in collect(int32_t).
 
virtual bool acceptsDocsOutOfOrder ()=0
 Return true if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to collect.
 
- Public Member Functions inherited from Lucene::LuceneObject
virtual ~LuceneObject ()
 
virtual void initialize ()
 Called directly after instantiation to create objects that depend on this object being fully constructed.
 
virtual LuceneObjectPtr clone (const LuceneObjectPtr &other=LuceneObjectPtr())
 Return clone of this object.
 
virtual int32_t hashCode ()
 Return hash code for this object.
 
virtual bool equals (const LuceneObjectPtr &other)
 Return whether two objects are equal.
 
virtual int32_t compareTo (const LuceneObjectPtr &other)
 Compare two objects.
 
virtual String toString ()
 Returns a string representation of the object.
 
- Public Member Functions inherited from Lucene::LuceneSync
virtual ~LuceneSync ()
 
virtual SynchronizePtr getSync ()
 Return this object synchronize lock.
 
virtual LuceneSignalPtr getSignal ()
 Return this object signal.
 
virtual void lock (int32_t timeout=0)
 Lock this object using an optional timeout.
 
virtual void unlock ()
 Unlock this object.
 
virtual bool holdsLock ()
 Returns true if this object is currently locked by current thread.
 
virtual void wait (int32_t timeout=0)
 Wait for signal using an optional timeout.
 
virtual void notifyAll ()
 Notify all threads waiting for signal.
 

Static Public Member Functions

static String _getClassName ()
 

Additional Inherited Members

- Protected Member Functions inherited from Lucene::LuceneObject
 LuceneObject ()
 
- Protected Attributes inherited from Lucene::LuceneSync
SynchronizePtr objectLock
 
LuceneSignalPtr objectSignal
 

Detailed Description

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. Likely your application can use one of these classes, or subclass TopDocsCollector, instead of implementing Collector directly:

Collector decouples the score from the collected doc: the score computation is skipped entirely if it's not needed. Collectors that do need the score should implement the setScorer method, to hold onto the passed Scorer instance, and call Scorer#score() within the collect method to compute the current hit's score. If your collector may request the score for a single hit multiple times, you should use ScoreCachingWrappingScorer.

NOTE: The doc that is passed to the collect method is relative to the current reader. If your collector needs to resolve this to the docID space of the Multi*Reader, you must re-base it by recording the docBase from the most recent setNextReader call. Here's a simple example showing how to collect docIDs into a BitSet:

class MyCollector : public Collector
{
public:
    MyCollector(const BitSetPtr& bits)
    {
        this->bits = bits;
        this->docBase = 0;
    }

protected:
    BitSetPtr bits;
    int32_t docBase;

public:
    virtual void setScorer(const ScorerPtr& scorer)
    {
        // ignore scorer
    }

    virtual void collect(int32_t doc)
    {
        bits->set(doc + docBase);
    }

    virtual void setNextReader(const IndexReaderPtr& reader, int32_t docBase)
    {
        this->docBase = docBase;
    }

    virtual bool acceptsDocsOutOfOrder()
    {
        return true; // accept docs out of order (for a BitSet it doesn't matter)
    }
};

...

SearcherPtr searcher = newLucene<IndexSearcher>(indexReader);
BitSetPtr bits = newLucene<BitSet>(indexReader->maxDoc());
searcher->search(query, newLucene<MyCollector>(bits));

Not all collectors will need to rebase the docID. For example, a collector that simply counts the total number of hits would skip it.

NOTE: Prior to 2.9, Lucene silently filtered out hits with score <= 0. As of 2.9, the core Collectors no longer do that. It's very unusual to have such hits (a negative query boost, or function query returning negative custom scores, could cause it to happen). If you need that behavior, use PositiveScoresOnlyCollector.

Constructor & Destructor Documentation

◆ ~Collector()

virtual Lucene::Collector::~Collector ( )
virtual

Member Function Documentation

◆ _getClassName()

static String Lucene::Collector::_getClassName ( )
inlinestatic

◆ acceptsDocsOutOfOrder()

virtual bool Lucene::Collector::acceptsDocsOutOfOrder ( )
pure virtual

Return true if this collector does not require the matching docIDs to be delivered in int sort order (smallest to largest) to collect.

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.

Implemented in Lucene::BooleanScorerCollector, Lucene::PositiveScoresOnlyCollector, Lucene::TimeLimitingCollector, and Lucene::TopFieldCollector.

◆ collect()

virtual void Lucene::Collector::collect ( int32_t  doc)
pure virtual

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

Note: This is called in an inner search loop. For good search performance, implementations of this method should not call Searcher#doc(int32_t) or IndexReader#document(int32_t) on every hit. Doing so can slow searches by an order of magnitude or more.

Implemented in Lucene::BooleanScorerCollector, Lucene::PositiveScoresOnlyCollector, and Lucene::TimeLimitingCollector.

◆ getClassName()

virtual String Lucene::Collector::getClassName ( )
inlinevirtual

◆ setNextReader()

virtual void Lucene::Collector::setNextReader ( const IndexReaderPtr reader,
int32_t  docBase 
)
pure virtual

Called before collecting from each IndexReader. All doc ids in collect(int32_t) will correspond to reader. Add docBase to the current IndexReaders internal document id to re-base ids in collect(int32_t).

Parameters
readernext IndexReader
docBase

Implemented in Lucene::BooleanScorerCollector, Lucene::PositiveScoresOnlyCollector, Lucene::TimeLimitingCollector, and Lucene::TopScoreDocCollector.

◆ setScorer()

virtual void Lucene::Collector::setScorer ( const ScorerPtr scorer)
pure virtual

Called before successive calls to collect(int32_t). Implementations that need the score of the current document (passed-in to collect(int32_t)), should save the passed-in Scorer and call scorer.score() when needed.

Implemented in Lucene::BooleanScorerCollector, Lucene::PositiveScoresOnlyCollector, Lucene::TimeLimitingCollector, and Lucene::TopScoreDocCollector.

◆ shared_from_this()

boost::shared_ptr< Collector > Lucene::Collector::shared_from_this ( )
inline

The documentation for this class was generated from the following file:

clucene.sourceforge.net