Class PerFieldSimilarityWrapper

  • public abstract class PerFieldSimilarityWrapper
    extends Similarity
    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.

    WARNING: This API is experimental and might change in incompatible ways in the next release.
    • Constructor Detail

      • PerFieldSimilarityWrapper

        public PerFieldSimilarityWrapper()
        Sole constructor. (For invocation by subclass constructors, typically implicit.)
    • Method Detail

      • computeNorm

        public final long computeNorm​(FieldInvertState state)
        Description copied from class: Similarity
        Computes the normalization value for a field, given the accumulated state of term processing for this field (see 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.

        Specified by:
        computeNorm in class Similarity
        state - current processing state for this field
        computed norm value
      • computeWeight

        public final Similarity.SimWeight computeWeight​(float boost,
                                                        CollectionStatistics collectionStats,
                                                        TermStatistics... termStats)
        Description copied from class: Similarity
        Compute any collection-level weight (e.g. IDF, average document length, etc) needed for scoring a query.
        Specified by:
        computeWeight in class Similarity
        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.