Class: Ferret::Search::Spans::SpanWeight

Inherits:
Weight
  • Object
show all
Includes:
Ferret::Search
Defined in:
lib/ferret/search/spans/span_weight.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(query, searcher) ⇒ SpanWeight

Returns a new instance of SpanWeight.



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# File 'lib/ferret/search/spans/span_weight.rb', line 4

def initialize(query, searcher)
  @similarity = query.similarity(searcher)
  @query = query
  @terms = query.terms()

  @idf = @query.similarity(searcher).idf_phrase(@terms, searcher)
end

Instance Attribute Details

#query ⇒ Object (readonly)

Returns the value of attribute query.



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# File 'lib/ferret/search/spans/span_weight.rb', line 12

def query
  @query
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/ferret/search/spans/span_weight.rb', line 12

def value
  @value
end

Instance Method Details

#explain(reader, doc) ⇒ Object 



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# File 'lib/ferret/search/spans/span_weight.rb', line 31

def explain(reader, doc)
  result = Explanation.new()
  result.description = "weight(#{@query} in #{doc}), product of:"
  field = @query.field

  doc_freqs = @terms.map {|t| "#{t.text}=#{reader.doc_freq(t)}"}.join(' ')

  idf_expl = Explanation.new(@idf, "idf(#{field}: #{doc_freqs})")

  # explain query weight
  query_expl = Explanation.new()
  query_expl.description = "query_weight(#{@query}), product of:"

  boost_expl = Explanation.new(@query.boost, "boost")
  query_expl << boost_expl if (@query.boost != 1.0)
  query_expl << idf_expl

  query_norm_expl = Explanation.new(@query_norm,"query_norm")
  query_expl << query_norm_expl

  query_expl.value = boost_expl.value * idf_expl.value * query_norm_expl.value

  result << query_expl

  # explain field weight
  field_expl = Explanation.new()
  field_expl.description = "field_weight(#{field}:#{@query.to_s(field)}"+
                           " in #{doc}), product of:"

  tf_expl = scorer(reader).explain(doc)
  field_expl << tf_expl
  field_expl << idf_expl

  field_norm_expl = Explanation.new()
  field_norms = reader.get_norms(field)
  field_norm = (field_norms ? Similarity.decode_norm(field_norms[doc]) : 0.0)
  field_norm_expl.value = field_norm
  field_norm_expl.description = "field_norm(field=#{field}, doc=#{doc})"
  field_expl << field_norm_expl

  field_expl.value = tf_expl.value * idf_expl.value * field_norm_expl.value

  result << field_expl

  # combine them
  result.value = query_expl.value * field_expl.value

  if (query_expl.value == 1.0)
    return field_expl
  end
  return result
end

#normalize(query_norm) ⇒ Object 



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# File 'lib/ferret/search/spans/span_weight.rb', line 19

def normalize(query_norm) 
  @query_norm = query_norm
  @query_weight *= query_norm                     # normalize query weight
  @value = @query_weight * @idf                    # idf for document
end

#scorer(reader) ⇒ Object 



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# File 'lib/ferret/search/spans/span_weight.rb', line 25

def scorer(reader)
  return SpanScorer.new(@query.spans(reader), self,
                        @similarity,
                        reader.get_norms(@query.field))
end

#sum_of_squared_weights ⇒ Object 



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

def sum_of_squared_weights()
  @query_weight = @idf * @query.boost()         # compute query weight
  return @query_weight * @query_weight             # square it
end