Field Detail

• discountOverlaps

  protected boolean discountOverlaps

Constructor Detail

• DefaultSimilarity

  public DefaultSimilarity()

Method Detail

• computeNorm

  public float computeNorm​(String field,
                           FieldInvertState state)

  Implemented as state.getBoost()*lengthNorm(numTerms), where numTerms is FieldInvertState.getLength() if setDiscountOverlaps(boolean) is false, else it's FieldInvertState.getLength() - FieldInvertState.getNumOverlap().

  Specified by:

  computeNorm in class Similarity

  Parameters:

  field - field name

  state - current processing state for this field

  Returns:

  the calculated float norm

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

• queryNorm

  public float queryNorm​(float sumOfSquaredWeights)

  Implemented as 1/sqrt(sumOfSquaredWeights).

  Specified by:

  queryNorm in class Similarity

  Parameters:

  sumOfSquaredWeights - the sum of the squares of query term weights

  Returns:

  a normalization factor for query weights

• tf

  public float tf​(float freq)

  Implemented as sqrt(freq).

  Specified by:

  tf in class Similarity

  Parameters:

  freq - the frequency of a term within a document

  Returns:

  a score factor based on a term's within-document frequency

• sloppyFreq

  public float sloppyFreq​(int distance)

  Implemented as 1 / (distance + 1).

  Specified by:

  sloppyFreq in class Similarity

  Parameters:

  distance - the edit distance of this sloppy phrase match

  Returns:

  the frequency increment for this match

  See Also:

  PhraseQuery.setSlop(int)

• idf

  public float idf​(int docFreq,
                   int numDocs)

  Implemented as log(numDocs/(docFreq+1)) + 1.

  Specified by:

  idf in class Similarity

  Parameters:

  docFreq - the number of documents which contain the term

  numDocs - the total number of documents in the collection

  Returns:

  a score factor based on the term's document frequency

• coord

  public float coord​(int overlap,
                     int maxOverlap)

  Implemented as overlap / maxOverlap.

  Specified by:

  coord in class Similarity

  Parameters:

  overlap - the number of query terms matched in the document

  maxOverlap - the total number of terms in the query

  Returns:

  a score factor based on term overlap with the query

• setDiscountOverlaps

  public void setDiscountOverlaps​(boolean v)

  Determines 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.

  See Also:

  computeNorm(java.lang.String, org.apache.lucene.index.FieldInvertState)

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

• getDiscountOverlaps

  public boolean getDiscountOverlaps()

  See Also:

  setDiscountOverlaps(boolean)