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java.lang.Object org.apache.lucene.search.similarities.Similarity org.apache.lucene.search.similarities.PerFieldSimilarityWrapper
public abstract class PerFieldSimilarityWrapper
Provides the ability to use a different Similarity
for different fields.
Subclasses should implement get(String)
to return an appropriate
Similarity (for example, using field-specific parameter values) for the field.
Nested Class Summary |
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Nested classes/interfaces inherited from class org.apache.lucene.search.similarities.Similarity |
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Similarity.SimScorer, Similarity.SimWeight |
Constructor Summary | |
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PerFieldSimilarityWrapper()
Sole constructor. |
Method Summary | |
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long |
computeNorm(FieldInvertState state)
Computes the normalization value for a field, given the accumulated state of term processing for this field (see FieldInvertState ). |
Similarity.SimWeight |
computeWeight(float queryBoost,
CollectionStatistics collectionStats,
TermStatistics... termStats)
Compute any collection-level weight (e.g. |
abstract Similarity |
get(String name)
Returns a Similarity for scoring a field. |
Similarity.SimScorer |
simScorer(Similarity.SimWeight weight,
AtomicReaderContext context)
Creates a new Similarity.SimScorer to score matching documents from a segment of the inverted index. |
Methods inherited from class org.apache.lucene.search.similarities.Similarity |
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coord, queryNorm |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public PerFieldSimilarityWrapper()
Method Detail |
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public final long computeNorm(FieldInvertState state)
Similarity
FieldInvertState
).
Matches in longer fields are less precise, so implementations of this
method usually set smaller values when state.getLength()
is large,
and larger values when state.getLength()
is small.
computeNorm
in class Similarity
state
- current processing state for this field
public final Similarity.SimWeight computeWeight(float queryBoost, CollectionStatistics collectionStats, TermStatistics... termStats)
Similarity
computeWeight
in class Similarity
queryBoost
- the query-time boost.collectionStats
- collection-level statistics, such as the number of tokens in the collection.termStats
- term-level statistics, such as the document frequency of a term across the collection.
public final Similarity.SimScorer simScorer(Similarity.SimWeight weight, AtomicReaderContext context) throws IOException
Similarity
Similarity.SimScorer
to score matching documents from a segment of the inverted index.
simScorer
in class Similarity
weight
- collection information from Similarity.computeWeight(float, CollectionStatistics, TermStatistics...)
context
- segment of the inverted index to be scored.
context
IOException
- if there is a low-level I/O errorpublic abstract Similarity get(String name)
Similarity
for scoring a field.
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