Issue type:

[X] question
[?] bug report

Database system/driver:

[X] mysql / mariadb

TypeORM version:

[X] 0.2.6 (or put your version here)

Steps to reproduce or a small repository showing the problem:

My entities are like this

@Entity('User')
class User {
  @PrimaryColumn('varchar', { length: 120 })
  public id: string;

  @Column('varchar', { length: 120 })
  public name: string;

  @OneToMany(() => Comment, (comment: Comment) => comment.user, {
    cascade: true,
    eager: true
  })
  public comments: Comment[];
}

@Entity('Comment')
class Comment {
  @PrimaryGeneratedColumn('uuid')
  public id: string;

  @Column('varchar', { length: 500 })
  public content: string;

  @ManyToOne(() => User, (user: User) => user.comments, {
    onDelete: 'CASCADE'
  })
  @JoinColumn({ name: 'userId' })
  public comment: Comment;

  @Column('datetime', { nullable: true })
  public deletedAt: Date | null;
}
** I guess it could have some typos or mistakes because it is just code sample for describing my settings

My problem is

• I am working with DDD, so User is an aggregate which contains Comments
• In User aggregate, User is aggregate root and entity, comment is just value object.
• In DDD, VO must be replaced new value object when it should be modified.
• So, my job is here. I want to modify user's comment, in this time, i should create new VO as following it's change and save it. Including deletion of original comment. But I can't do that, because original comments are not deleted, just have null in it's foreign key. I know that I didn't set nullable=false, but If I set this option to false, an error occurs: QueryFailedError: ER_BAD_NULL_ERROR: Column 'UserId' cannot be null.

** Of course TypeOrm entities will be mapped to Domain Objects.
May they be like this:

class User {
	private userId: number;
	private comments: Comment[]

	...
	public modifyComment(origin: Comment) {
		comments.push(new Comment('blah blah'));
		this.removeComment(origin);
	}
}

• I can handle it modifying orignal object instead of creating new one and deleting it, however, it is not what I want to do. I am trying to strictly follow rules of DDD.

What I want is

• How can I remove an comment clearly instead of inserting null value to it's foreign key userId?
• and Why nullable=false is not working as I expected?

Thank you for your supporting.