arel_columns

# File activerecord/lib/active_record/relation/query_methods.rb, line 1066
    def arel_columns(columns)
      if from_value
        columns
      else
        columns.map do |field|
          if (Symbol === field || String === field) && columns_hash.key?(field.to_s)
            arel_table[field]
          else
            field
          end
        end
      end
    end