grails的domain继承之后生成的表结构

Now have the follow:
Category : Goods = one:many，
then create-domain-class Car ，do the following modifications：

class Car extends Goods{}

after run-app , compared to the previous table structure:
category : unchanged
goods : add a column : class . the content of this column is the object corresponding to the class name
car : column: id , version