Lucene++ - a full-featured, c++ search engine
API Documentation
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>
Public Member Functions | |
virtual | ~Collector () |
virtual String | getClassName () |
boost::shared_ptr< Collector > | shared_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 . | |
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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. | |
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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 | |
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LuceneObject () | |
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SynchronizePtr | objectLock |
LuceneSignalPtr | objectSignal |
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:
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
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
.
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virtual |
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inlinestatic |
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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.
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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.
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inlinevirtual |
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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)
.
reader | next IndexReader |
docBase |
Implemented in Lucene::BooleanScorerCollector, Lucene::PositiveScoresOnlyCollector, Lucene::TimeLimitingCollector, and Lucene::TopScoreDocCollector.
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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.
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inline |