save related entities only with PK {typeorm}

TypeORM 엔티티 인스턴스를 생성할 때 연관 인스턴스 없이 식별키만 가지고 만들 수 있나요?

Yes, you can create an instance of a TypeORM entity and assign a primary key directly without fetching the related relational entity. This approach is useful when you only have the primary key of a related entity and do not need the full relational object.

Here’s how you can do it:

Example Scenario

Assume you have two entities: User and Post, where a Post entity has a many-to-one relationship with the User entity.

@Entity()
export class User {
    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    name: string;

    @OneToMany(() => Post, (post) => post.user)
    posts: Post[];
}

@Entity()
export class Post {
    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    title: string;

    @ManyToOne(() => User, (user) => user.posts)
    user: User;
}

Creating a Post with only the User ID

You can create an instance of the Post entity by assigning the user property with only the User entity's primary key, like this:

const userId = 1; // Assume this is the ID of an existing user

// Create a new Post instance
const post = new Post();
post.title = "New Post";
post.user = { id: userId } as User; // Assign only the primary key

// Save the Post
await postRepository.save(post);

Explanation

• In the above code, post.user is assigned a partial User object containing only the id.
• TypeORM understands this and uses the id to set up the relationship without fetching the full User entity from the database.

Notes

1. Validation: Ensure the referenced primary key exists in the database to avoid foreign key constraint errors.
2. Performance: This method avoids an extra query to fetch the related entity, improving performance when the primary key is already known.
3. Type Safety: Using as User ensures TypeScript does not complain about assigning a partial object.

This approach is clean and efficient when you do not need to load the full relational object.