Class: ActsAsXapian::Similar

Inherits:
QueryBase show all
Defined in:
lib/acts_as_xapian/similar.rb

Overview

Search for models which contain theimportant terms taken from a specified list of models. i.e. Use to find documents similar to one (or more) documents, or use to refine searches.

Instance Attribute Summary collapse

Attributes inherited from QueryBase

#cached_results, #limit, #offset, #query, #runtime

Instance Method Summary collapse

Methods inherited from QueryBase

#description, #matches, #matches_estimated, #results, #spelling_correction

Constructor Details

#initialize(model_classes, query_models, options = {}) ⇒ Similar

model_classes - model classes to search within, e.g. [PublicBody, User] query_models - list of models you want to find things similar to



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# File 'lib/acts_as_xapian/similar.rb', line 11

def initialize(model_classes, query_models, options = {})
  self.initialize_db(model_classes)

  self.runtime += Benchmark::realtime do
    # Case of an array, searching for models similar to those models in the array
    self.query_models = query_models

    # Find the documents by their unique term
    input_models_query = Xapian::Query.new(Xapian::Query::OP_OR, query_models.map {|m| "I#{m.xapian_document_term}" })
    begin
      @index.enquire.query = input_models_query

      # Get set of relevant terms for those documents
      selection = Xapian::RSet.new()
      @index.enquire.mset(0, 100, 100).matches.each {|m| selection.add_document(m.docid) } # XXX so this whole method will only work with 100 docs

      # Bit weird that the function to make esets is part of the enquire
      # object. This explains what exactly it does, which is to exclude
      # terms in the existing query.
      # http://thread.gmane.org/gmane.comp.search.xapian.general/3673/focus=3681
      #
      # Do main search for them
      self.important_terms = @index.enquire.eset(40, selection).terms.map {|e| e.name }
    rescue IOError => e
      if @retried.nil? && /DatabaseModifiedError/.match(e.message.to_s)
        @retried = true
        @index.reset_enquire!
        retry
      end
      raise e
    end

    similar_query = Xapian::Query.new(Xapian::Query::OP_OR, self.important_terms)
    # Exclude original
    combined_query = Xapian::Query.new(Xapian::Query::OP_AND_NOT, similar_query, input_models_query)

    # Restrain to model classes
    model_query = Xapian::Query.new(Xapian::Query::OP_OR, model_classes.map {|mc| "M#{mc}" })
    self.query = Xapian::Query.new(Xapian::Query::OP_AND, model_query, combined_query)
  end

  # Call base class constructor
  self.initialize_query(options)
end

Instance Attribute Details

#important_terms ⇒ Object

Returns the value of attribute important_terms.



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# File 'lib/acts_as_xapian/similar.rb', line 7

def important_terms
  @important_terms
end

#query_models ⇒ Object

Returns the value of attribute query_models.



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# File 'lib/acts_as_xapian/similar.rb', line 6

def query_models
  @query_models
end

Instance Method Details

#log_description ⇒ Object

Text for lines in log file



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# File 'lib/acts_as_xapian/similar.rb', line 57

def log_description
  "Similar: #{self.query_models}"
end