Class: ActsAsIndexed::SearchAtom

Inherits:
Object
  • Object
show all
Defined in:
lib/acts_as_indexed/search_atom.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(records = ActiveSupport::OrderedHash.new) ⇒ SearchAtom

Returns a new instance of SearchAtom.



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# File 'lib/acts_as_indexed/search_atom.rb', line 14

def initialize(records=ActiveSupport::OrderedHash.new)
  @records = records
end

Instance Attribute Details

#records ⇒ Object (readonly)

Contains a hash of records. { ‘record_id’ => [pos1, pos2, pos] } – Weighting: www.perlmonks.com/index.pl?node_id=27509 W(T, D) = tf(T, D) * log ( DN / df(T)) weighting = frequency_in_this_record * log (total_number_of_records / number_of_matching_records)



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# File 'lib/acts_as_indexed/search_atom.rb', line 12

def records
  @records
end

Instance Method Details

#+(other) ⇒ Object

Creates a new SearchAtom with the combined records from self and other



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# File 'lib/acts_as_indexed/search_atom.rb', line 50

def +(other)
  SearchAtom.new(@records.clone.merge!(other.records) { |key, _old, _new|
                                                        _old + _new
                                                      })
end

#-(other) ⇒ Object

Creates a new SearchAtom with records in other removed from self.



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# File 'lib/acts_as_indexed/search_atom.rb', line 57

def -(other)
  records = @records.clone.reject { |name, records| other.records.include?(name) }
  SearchAtom.new(records)
end

#add_position(record_id, pos) ⇒ Object

Adds pos to the array of positions for record_id.



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# File 'lib/acts_as_indexed/search_atom.rb', line 29

def add_position(record_id, pos)
  add_record(record_id)
  @records[record_id] << pos
end

#add_record(record_id) ⇒ Object

Adds record_id to the stored records.



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# File 'lib/acts_as_indexed/search_atom.rb', line 24

def add_record(record_id)
  @records[record_id] = [] unless include_record?(record_id)
end

#include_record?(record_id) ⇒ Boolean

Returns true if the given record is present.

Returns:

  • (Boolean) 


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# File 'lib/acts_as_indexed/search_atom.rb', line 19

def include_record?(record_id)
  @records.include?(record_id)
end

#positions(record_id) ⇒ Object

Returns an array of positions for record_id stored in this Atom.



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# File 'lib/acts_as_indexed/search_atom.rb', line 40

def positions(record_id)
  @records[record_id]
end

#preceded_by(former) ⇒ Object

Returns at atom containing the records and positions of self preceded by former “former latter” or “big dog” where “big” is the former and “dog” is the latter.



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# File 'lib/acts_as_indexed/search_atom.rb', line 64

def preceded_by(former)
  matches = SearchAtom.new
  latter = ActiveSupport::OrderedHash.new
  former.record_ids.each do |rid|
    latter[rid] = @records[rid] if @records[rid]
  end
  # Iterate over each record in latter.
  latter.each do |record_id,pos|

    # Iterate over each position.
    pos.each do |p|
      # Check if previous position is in former.
      if former.include_position?(record_id,p-1)
        matches.add_record(record_id) unless matches.include_record?(record_id)
        matches.add_position(record_id,p)
      end
    end

  end
  matches
end

#record_ids ⇒ Object

Returns all record IDs stored in this Atom.



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# File 'lib/acts_as_indexed/search_atom.rb', line 35

def record_ids
  @records.keys
end

#remove_record(record_id) ⇒ Object

Removes record_id from this Atom.



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# File 'lib/acts_as_indexed/search_atom.rb', line 45

def remove_record(record_id)
  @records.delete(record_id)
end

#weightings(records_size) ⇒ Object

Returns a hash of record_ids and weightings for each record in the atom.



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# File 'lib/acts_as_indexed/search_atom.rb', line 88

def weightings(records_size)
  out = ActiveSupport::OrderedHash.new

  ## phurni 2012-09-21 when records_size is exactly the @records.size (all records are matches), the Math.log would
  ## return 0 which means the frequency (pos.size) will have no effect. Cheat to make it like the matching
  ## record is one less, so that we still can weight on frequency.
  matching_records_size = (records_size == @records.size ? @records.size - 1 : @records.size)

  @records.each do |r_id, pos|

    # Fixes a bug when the records_size is zero. i.e. The only record
    # contaning the word has been deleted.
    if records_size < 1
      out[r_id] = 0.0
      next
    end

    # weighting = frequency * log (records.size / records_with_atom)
    ## parndt 2010/05/03 changed to records_size.to_f to avoid -Infinity Errno::ERANGE exceptions
    ## which would happen for example Math.log(1 / 20) == -Infinity but Math.log(1.0 / 20) == -2.99573227355399
    out[r_id] = pos.size * Math.log(records_size.to_f / matching_records_size)
  end

  out
end