def fetch_block(block_size = nil)
      block_size ||= @block_size ||= @options.fetch(:block_size, 1000)
      @result = @connection.execute("fetch #{block_size} from #{@cursor}")

      @block = if @iterate == :each_array
        @result.each_row.collect { |row| row }
      else
        @result.collect { |row| row }
      end
    end
Private: Fetches the next block of rows into @block