public abstract class PerFieldSimilarityWrapper extends SimilarityProvides the ability to use a different
Similarityfor different fields.
Subclasses should implement
get(String)to return an appropriate Similarity (for example, using field-specific parameter values) for the field.
- WARNING: This API is experimental and might change in incompatible ways in the next release.
Constructors Constructor Description
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description
computeNorm(FieldInvertState state)Computes the normalization value for a field, given the accumulated state of term processing for this field (see
get(String name)Returns a
Similarityfor scoring a field.
scorer(float boost, CollectionStatistics collectionStats, TermStatistics... termStats)Compute any collection-level weight (e.g.
public final long computeNorm(FieldInvertState state)Description copied from class:
SimilarityComputes the normalization value for a field, given the accumulated state of term processing for this field (see
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
Note that for a given term-document frequency, greater unsigned norms must produce scores that are lower or equal, ie. for two encoded norms
Long.compareUnsigned(n1, n2) > 0then
SimScorer.score(freq, n1) <= SimScorer.score(freq, n2)for any legal
0is not a legal norm, so
1is the norm that produces the highest scores.
public final Similarity.SimScorer scorer(float boost, CollectionStatistics collectionStats, TermStatistics... termStats)Description copied from class:
SimilarityCompute any collection-level weight (e.g. IDF, average document length, etc) needed for scoring a query.
- Specified by:
boost- a multiplicative factor to apply to the produces scores
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.
- SimWeight object with the information this Similarity needs to score a query.