Class: Ferret::Search::TermQuery::TermWeight

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(query, searcher) ⇒ TermWeight

Returns a new instance of TermWeight.



11
12
13
14
15
16
17
 
# File 'lib/ferret/search/term_query.rb', line 11

def initialize(query, searcher)
  @similarity = query.similarity(searcher)
  @idf = @similarity.idf(searcher.doc_freq(query.term),
                         searcher.max_doc) # compute idf
  @query = query
  @value = 0
end

Instance Attribute Details

#query ⇒ Object (readonly)

Returns the value of attribute query.



9
10
11
 
# File 'lib/ferret/search/term_query.rb', line 9

def query
  @query
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



9
10
11
 
# File 'lib/ferret/search/term_query.rb', line 9

def value
  @value
end

Instance Method Details

#explain(reader, doc) ⇒ Object 



41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
 
# File 'lib/ferret/search/term_query.rb', line 41

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

  idf_expl = Explanation.new(@idf, "idf(doc_freq=#{reader.doc_freq(@query.term)})")

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

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

  query_norm_expl = Explanation.new(@query_norm||0.0,"query_norm")
  query_expl << query_norm_expl

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

  explanation << query_expl

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

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

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

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

  # combine them
  explanation.value = (query_expl.value * field_expl.value)

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

  return explanation
end

#normalize(query_norm) ⇒ Object 



26
27
28
29
30
 
# File 'lib/ferret/search/term_query.rb', line 26

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 



32
33
34
35
36
37
38
39
 
# File 'lib/ferret/search/term_query.rb', line 32

def scorer(reader)
  term_docs = reader.term_docs_for(@query.term)

  return nil if term_docs.nil?

  return TermScorer.new(self, term_docs, @similarity,
                        reader.get_norms(@query.term.field))
end

#sum_of_squared_weights ⇒ Object 



21
22
23
24
 
# File 'lib/ferret/search/term_query.rb', line 21

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

#to_s ⇒ Object 



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

def to_s() return "TermWeight(#{@value})"; end