Interface LeafCollector
- All Known Implementing Classes:
FilterLeafCollector,SimpleCollector
setScorer(org.apache.lucene.search.Scorable)
method, to hold onto the passed Scorer instance, and call Scorable.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:
IndexSearcher searcher = new IndexSearcher(indexReader);
final BitSet bits = new BitSet(indexReader.maxDoc());
searcher.search(query, new Collector() {
public LeafCollector getLeafCollector(LeafReaderContext context)
throws IOException {
final int docBase = context.docBase;
return new LeafCollector() {
// ignore scorer
public void setScorer(Scorer scorer) throws IOException {
}
public void collect(int doc) throws IOException {
bits.set(docBase + doc);
}
};
}
});
Not all collectors will need to rebase the docID. For example, a collector that simply counts the total number of hits would skip it.
- WARNING: This API is experimental and might change in incompatible ways in the next release.
-
Method Summary
Modifier and TypeMethodDescriptionvoidcollect(int doc) Called once for every document matching a query, with the unbased document number.default voidcollect(DocIdStream stream) Bulk-collect doc IDs.default DocIdSetIteratorOptionally returns an iterator over competitive documents.default voidfinish()Hook that gets called once the leaf that is associated with this collector has finished collecting successfully, including when aCollectionTerminatedExceptionis thrown.voidCalled before successive calls tocollect(int).
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Method Details
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setScorer
Called before successive calls tocollect(int). Implementations that need the score of the current document (passed-in tocollect(int)), should save the passed-in Scorer and call scorer.score() when needed.- Throws:
IOException
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collect
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 currentLeafReaderContextwill be skipped andIndexSearcherwill 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
StoredFields.document(int)on every hit. Doing so can slow searches by an order of magnitude or more.- Throws:
IOException
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collect
Bulk-collect doc IDs.Note: The provided
DocIdStreammay be reused across calls and should be consumed immediately.Note: The provided
DocIdStreamtypically only holds a small subset of query matches. This method may be called multiple times per segment.Like
collect(int), it is guaranteed that doc IDs get collected in order, ie. doc IDs are collected in order within aDocIdStream, and if called twice, all doc IDs from the secondDocIdStreamwill be greater than all doc IDs from the firstDocIdStream.It is legal for callers to mix calls to
collect(DocIdStream)andcollect(int).The default implementation calls
stream.forEach(this::collect).- Throws:
IOException
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competitiveIterator
Optionally returns an iterator over competitive documents.Collectors should delegate this method to their comparators if their comparators provide the skipping functionality over non-competitive docs.
The default is to return
nullwhich is interpreted as the collector provide any competitive iterator.- Throws:
IOException
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finish
Hook that gets called once the leaf that is associated with this collector has finished collecting successfully, including when aCollectionTerminatedExceptionis thrown. This is typically useful to compile data that has been collected on this leaf, e.g. to convert facet counts on leaf ordinals to facet counts on global ordinals. The default implementation does nothing.Note: It can be assumed that this method will only be called once per LeafCollector instance.
- Throws:
IOException
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