Docs: Add examples for update many-to-many relations with custom properties

Issue type: [x] documentation issue

Database system/driver: [x] mysql / mariadb

TypeORM version: [x] latest

Steps to reproduce or a small repository showing the problem: Is it possible to add more examples in docs for “many-to-many relations with custom properties”? I’m having trouble getting it to work. For example save/update a many to many entity from one of the relationship:

I have 3 tables: users, roles, user_roles

User.ts

@Entity('users')
class User {
  @PrimaryGeneratedColumn('increment')
  id: number;

  @Column()
  name: string;

  @Column()
  email: string;
  
  @OneToMany(() => UserRole, userRole => userRole.user, {
    cascade: true,
    onDelete: 'CASCADE',
    onUpdate: 'CASCADE',
  })
  @JoinColumn({ referencedColumnName: 'user_id' })
  userRoles!: UserRole[];
}

export default User;

Role.ts

@Entity('roles')
class Role {
  @PrimaryGeneratedColumn('increment')
  id: number;

  @Column()
  role: string;

  @OneToMany(() => UserRole, userRole => userRole.role, {
    cascade: true,
    onDelete: 'CASCADE',
    onUpdate: 'CASCADE',
  })
  @JoinColumn({ referencedColumnName: 'role_id' })
  userRoles!: UserRole[];
}

export default Role;

UserRole.ts

@Entity('user_roles')
class UserRole {
 @PrimaryGeneratedColumn('increment')
 id: number;

 @Column()
 user_id!: number;

 @Column()
 role_id!: number;
 
 @CreateDateColumn()
 created_at: Date;

 @UpdateDateColumn()
 updated_at: Date;

 @ManyToOne(() => User, user => user.userRoles)
 @JoinColumn({ name: 'user_id' })
 user!: User;

 @ManyToOne(() => Role, role => role.userRoles)
 @JoinColumn({ name: 'role_id' })
 role!: Role;
}

export default UserRole;

Create a record in user_roles is working, I can save a user with related userRoles:

const user = {
  name: 'test',
  email: '[e-mail]',
  userRoles: [
    { role_id: 1 },
    { role_id: 2 }, 
    { role_id: 3 },
    { role_id: 4 }
  ],
};

await this.usersRepository.save(user);

Update its not working, I want to replace all related user_roles with the new ones, is there any save strategy option in typeorm many to many relation? I have seen in other orms for example ‘replace’ or ‘append‘ option in relation definition This is how im trying to update:

// load user
const user = await this.usersRepository.findById(user_id);

/*
returns

User {
 id: 2,
 name: 'Test user',
 email: '[e-mail]',
 userRoles: [
   UserRole {
     id: 376,
     user_id: 2,
     role_id: 1,
     created_at: 2020-09-18T17:26:52.000Z,
     updated_at: 2020-09-18T17:26:52.000Z
   },
   UserRole {
     id: 377,
     user_id: 2,
     role_id: 2,
     created_at: 2020-09-18T17:26:52.000Z,
     updated_at: 2020-09-18T17:26:52.000Z
   },
   UserRole {
     id: 378,
     user_id: 2,
     role_id: 3,
     created_at: 2020-09-18T17:26:53.000Z,
     updated_at: 2020-09-18T17:26:53.000Z
   },
   UserRole {
     id: 379,
     user_id: 2,
     role_id: 4,
     created_at: 2020-09-18T17:26:53.000Z,
     updated_at: 2020-09-18T17:26:53.000Z
   }
 ]
}
*/

// edit user
const newRolesIds = [4, 5, 6,];

user.name = 'updated name';
user.email = '[e-mail]';


// isnt it suposed to replace old user_roles and create this new ones?
user.userRoles = newRolesIds.map(role_id => {
 const userRole = new UserRole();
 userRole.user_id = user_id;
 userRole.role_id = role_id;
 return userRole;
});

/*
user after edit:
User {
 id: 2,
 name: 'updated name',
 email: '[e-mail]',
 userRoles: [
   UserRole { user_id: 2, role_id: 4 },
   UserRole { user_id: 2, role_id: 5 },
   UserRole { user_id: 2, role_id: 6 },
 ]
}
*/

this.ormRepository.save(user);

Save fails with this sql error Its a strange update sql, not recognizing user_id and role_id is not eve present in sql am I forgetting to define something in relationships?

QueryFailedError: Cannot add or update a child row: a foreign key constraint fails (`user_roles`, CONSTRAINT `UserRoleUserIdFK` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE)
  code: 'ER_NO_REFERENCED_ROW_2',
  errno: 1452,
  sqlState: '23000',
  sqlMessage: 'Cannot add or update a child row: a foreign key constraint fails (`user_roles`, CONSTRAINT `UserRoleUserIdFK` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE)',
  query: 'UPDATE `user_roles` SET `user_id` = ?, `updated_at` = CURRENT_TIMESTAMP WHERE `id` = ?',
  parameters: [ undefined, 376 ]

[allandiego]

@sa-webb typeorm dont suport delete orphaned rows it set the related key to null and in my case it cant be null because its a FK with index, just delete works. There are a PR to add this feat, its exactly my relationship:

https://github.com/typeorm/typeorm/pull/7105

[sa-webb]

@allandiego I had a lot of issues working with my relationships in my database but ended up working them out. I can try to help you resolve this if I can. I am quite confused by your data modeling though. Without explaining why you’ve defined those three entities can you tell me your desired functionality?