# File ar-extensions/lib/ar-extensions/delete.rb, line 73
      def delete_duplicates(options={})
        supports_delete!

        options[:query_field]||= primary_key

        query = "DELETE FROM"
        query << " c1 USING #{quoted_table_name} c1, #{quoted_table_name} c2"
        query << " WHERE ("
        query << options[:fields].collect{|field| "c1.#{field} = c2.#{field}" }.join(" and ")
        query << " and (#{sanitize_sql(options[:conditions])})" unless options[:conditions].blank?
        query << " and "
        query << (options[:winner_clause]||"c1.#{options[:query_field]} > c2.#{options[:query_field]}")
        query << ")"

        self.connection.execute(self.send(:sanitize_sql, query))
      end