arel_columns_from_hash

# File activerecord/lib/active_record/relation/query_methods.rb, line 2186
      def arel_columns_from_hash(fields)
        fields.flat_map do |key, columns_aliases|
          case columns_aliases
          when Hash
            columns_aliases.map do |column, column_alias|
              if values[:joins]&.include?(key)
                references = PredicateBuilder.references({ key.to_s => fields[key] })
                self.references_values |= references unless references.empty?
              end
              arel_column("#{key}.#{column}") do
                predicate_builder.resolve_arel_attribute(key.to_s, column)
              end.as(column_alias.to_s)
            end
          when Array
            columns_aliases.map do |column|
              arel_column("#{key}.#{column}", &:itself)
            end
          when String, Symbol
            arel_column(key.to_s) do
              predicate_builder.resolve_arel_attribute(klass.table_name, key.to_s)
            end.as(columns_aliases.to_s)
          end
        end
      end