org.opencms.search

Class CmsSearchSimilarity

java.lang.Object

org.apache.lucene.search.similarities.Similarity

org.opencms.search.CmsSearchSimilarity

public class CmsSearchSimilarity
extends org.apache.lucene.search.similarities.Similarity

Reduces the importance of the computeNorm(FieldInvertState) factor for the CmsSearchField.FIELD_CONTENT field, while keeping the Lucene default for all other fields.

This implementation was added since apparently the default length norm is heavily biased for small documents. In the default, even if a term is found in 2 documents the same number of times, the smaller document (containing less terms) will have a score easily 3x as high as the longer document. Using this implementation the importance of the term number is reduced.

Inspired by Chuck Williams WikipediaSimilarity.

Since:

6.0.0

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.search.similarities.Similarity

org.apache.lucene.search.similarities.Similarity.SimScorer

Constructor Summary

Constructors

Constructor and Description
CmsSearchSimilarity() Creates a new instance of the OpenCms search similarity.

Method Summary

Modifier and Type	Method and Description
long	computeNorm(org.apache.lucene.index.FieldInvertState state) Special implementation for "compute norm" to reduce the significance of this factor for the CmsSearchField.FIELD_CONTENT field, while keeping the Lucene default for all other fields.
boolean	getDiscountOverlaps() Returns true iff overlap tokens are discounted from the document's length.
org.apache.lucene.search.similarities.Similarity.SimScorer	scorer(float boost, org.apache.lucene.search.CollectionStatistics collectionStats, org.apache.lucene.search.TermStatistics... termStats)
void	setDiscountOverlaps(boolean v) Sets whether overlap tokens (Tokens with 0 position increment) are ignored when computing norm.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CmsSearchSimilarity

public CmsSearchSimilarity()

Creates a new instance of the OpenCms search similarity.

Method Detail

computeNorm

public final long computeNorm(org.apache.lucene.index.FieldInvertState state)

Special implementation for "compute norm" to reduce the significance of this factor for the CmsSearchField.FIELD_CONTENT field, while keeping the Lucene default for all other fields.

Specified by:

computeNorm in class org.apache.lucene.search.similarities.Similarity

getDiscountOverlaps

public boolean getDiscountOverlaps()

Returns true iff overlap tokens are discounted from the document's length.

Returns:

true iff overlap tokens are discounted from the document's length.

See Also:

setDiscountOverlaps(boolean)

scorer

public org.apache.lucene.search.similarities.Similarity.SimScorer scorer(float boost,
                                                                         org.apache.lucene.search.CollectionStatistics collectionStats,
                                                                         org.apache.lucene.search.TermStatistics... termStats)

Specified by:

scorer in class org.apache.lucene.search.similarities.Similarity

See Also:

Similarity.scorer(float, org.apache.lucene.search.CollectionStatistics, org.apache.lucene.search.TermStatistics[])

setDiscountOverlaps

public void setDiscountOverlaps(boolean v)

Sets whether overlap tokens (Tokens with 0 position increment) are ignored when computing norm. By default this is true, meaning overlap tokens do not count when computing norms.

Parameters:

v - if true, tokens with position increment 0 are ignored when computing the norm, otherwise they are not ignored.