Class: Ferret::Search::Scorer

Inherits:
Object
  • Object
show all
Defined in:
lib/ferret/search/scorer.rb

Overview

Expert: Common scoring functionality for different types of queries.

A Scorer either iterates over documents matching a query, or provides an explanation of the score for a query for a given document.

Document scores are computed using a given Similarity implementation.

Constant Summary collapse

MAX_DOCS = 
0x7FFFFFFF

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(similarity) ⇒ Scorer

Constructs a Scorer.

similarity

The Similarity implementation used by this scorer.



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# File 'lib/ferret/search/scorer.rb', line 14

def initialize(similarity) 
  @similarity = similarity
end

Instance Attribute Details

#similarity ⇒ Object (readonly)

Returns the value of attribute similarity.



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# File 'lib/ferret/search/scorer.rb', line 9

def similarity
  @similarity
end

Instance Method Details

#doc ⇒ Object

Returns the current document number matching the query. Initially invalid, until #next?() is called the first time.

Raises:

  • (NotImplementedError) 


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# File 'lib/ferret/search/scorer.rb', line 49

def doc()
  raise NotImplementedError
end

#each_hit ⇒ Object

Expert: Iterates over matching all documents, yielding the document number and the score.

returns

true if more matching documents may remain.



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# File 'lib/ferret/search/scorer.rb', line 22

def each_hit() # :yields: doc, score

  while next?
    yield(doc(), score())
  end
end

#each_hit_up_to(max = MAX_DOCS) ⇒ Object

Expert: Iterates over matching documents in a range.

max

Do not score documents past this. Default will search all documents

avaliable.

returns

true if more matching documents may remain.



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# File 'lib/ferret/search/scorer.rb', line 33

def each_hit_up_to(max = MAX_DOCS) # :yields: doc, score

  while (next? and doc() < max)
    yield(doc(), score())
  end
  return doc() < max
end

#explain(doc) ⇒ Object

Returns an explanation of the score for a document.

When this method is used, the #next?(), #skip_to(int) and #score(HitCollector) methods should not be used.

doc

The document number for the explanation.

Raises:

  • (NotImplementedError) 


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# File 'lib/ferret/search/scorer.rb', line 87

def explain(doc)
  raise NotImplementedError
end

#next? ⇒ Boolean

Advances to the next document matching the query.

returns

true iff there is another document matching the query.

When this method is used the #explain(int) method should not be used.

Returns:

  • (Boolean)

Raises:

  • (NotImplementedError) 


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# File 'lib/ferret/search/scorer.rb', line 43

def next?()
  raise NotImplementedError
end

#score ⇒ Object

Returns the score for the current document matching the query. Initially invalid, until #next?() is called the first time.

Raises:

  • (NotImplementedError) 


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# File 'lib/ferret/search/scorer.rb', line 55

def score()
  raise NotImplementedError
end

#skip_to(target) ⇒ Object

Skips to the first match beyond the current whose document number is greater than or equal to a given target.

When this method is used the #explain(int) method should not be used.

target

The target document number.

returns

true iff there is such a match.

Behaves as if written:

def skip_to(target) 
  begin 
    return false if not next?()
  end while (target > doc())
  return true
end

Most implementations are considerably more efficient than that.

Raises:

  • (NotImplementedError) 


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# File 'lib/ferret/search/scorer.rb', line 77

def skip_to(target)
  raise NotImplementedError
end