Single table inheritance returns the same discriminator value error for unrelated tables where their parents extend from the same entity

[marypaz-sama]

Issue Description

There are two unrelated child entities following the single table inheritance pattern with same discriminator value, if both entities inherit from a class that just adds some common columns it, it throws an error.

For example:

             BaseEntity
           /            \
        Role           User
         |               |
     InternalRole    InternalUser

Both InternalRole and InternalRole entities have the same discriminator value internal.
BaseEntity just defines some common columns.

Expected Behavior

There should be no error, as the entities InternalUser and InternalRole are not related because BaseEntity is just a generic entity to create createdAt, updatedAt and primary columns for all tables. And TableInheritance decorator is added in User and Role entities not BaseEntity

Actual Behavior

It throws an error.

Error: Entities InternalUser and InternalRole have the same discriminator values. Make sure they are different while using the @ChildEntity decorator.

Steps to Reproduce

Minimal code reproduction:

export class BaseEntity {
  @PrimaryGeneratedColumn()
  id!: number;

  @CreateDateColumn()
  createdAt: Date;

  @UpdateDateColumn()
  updatedAt: Date;
}

@Entity()
@TableInheritance({ column: { type: 'varchar', name: 'type' } })
export abstract class User extends BaseEntity {
  @Column()
  firstName: string;

  @Column()
  lastName: string;
}

@ChildEntity('internal')
export class InternalUser extends User {
 }

@Entity()
@TableInheritance({ column: { type: 'varchar', name: 'type' } })
export class Role extends BaseEntity {
  @Column()
  name: string;

  @Column()
  description: string;
}

@ChildEntity('internal')
export class InternalRole extends Role {}

My Environment

Dependency	Version
Operating System	macOs
Node.js version	v16.13.1
Typescript version	v4.1.3
TypeORM version	v0.2.41
NestJS Version	v8.1.8

Additional Context

Relevant Database Driver(s)

• aurora-data-api
• aurora-data-api-pg
• better-sqlite3
• cockroachdb
• cordova
• expo
• mongodb
• mysql
• nativescript
• oracle
• postgres
• react-native
• sap
• sqlite
• sqlite-abstract
• sqljs
• sqlserver

Are you willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time, and I know how to start.
• Yes, I have the time, but I don't know how to start. I would need guidance.
• No, I don't have the time, although I believe I could do it if I had the time...
• No, I don't have the time and I wouldn't even know how to start.