hash_rows

# File activerecord/lib/active_record/result.rb, line 144
      def hash_rows
        @hash_rows ||=
          begin
            # We freeze the strings to prevent them getting duped when
            # used as keys in ActiveRecord::Base's @attributes hash
            columns = @columns.map(&:-@)
            length  = columns.length
            template = nil

            @rows.map { |row|
              if template
                # We use transform_values to build subsequent rows from the
                # hash of the first row. This is faster because we avoid any
                # reallocs and in Ruby 2.7+ avoid hashing entirely.
                index = -1
                template.transform_values do
                  row[index += 1]
                end
              else
                # In the past we used Hash[columns.zip(row)]
                #  though elegant, the verbose way is much more efficient
                #  both time and memory wise cause it avoids a big array allocation
                #  this method is called a lot and needs to be micro optimised
                hash = {}

                index = 0
                while index < length
                  hash[columns[index]] = row[index]
                  index += 1
                end

                # It's possible to select the same column twice, in which case
                # we can't use a template
                template = hash if hash.length == length

                hash
              end
            }
          end
      end