Table Inheritance using Enum Discriminator: column of relation already exists

Expected Behavior

Table Inheritance can be used with an enum as discriminator.

Actual Behavior

When trying to use an enum to discriminate the child entities (see code sample in steps to reproduce) I ran into the error:

[Nest] 52222   - 27/01/2021, 10:30:25   [TypeOrmModule] Unable to connect to the database. Retrying (2)... +1ms
QueryFailedError: column "action_category" contains null values
    at new QueryFailedError (/Users/rai/dev/lexstep/lexstep-nest/node_modules/.pnpm/typeorm@0.2.29/node_modules/typeorm/error/QueryFailedError.js:11:28)
I can avoid this issue by changing the name of one of the columns (either the @TableInheritance 'action_category' or the @Column 'action_category' but this results in an extra column being created

So I changed the @Column definition to use a default value, which silenced this error, but then produced:

QueryFailedError: column "action_category" of relation "action" already exists

Steps to Reproduce

Using the following entity definition:

export enum ActionCategory {
  SYSTEM = 'system',
  EMAIL = 'email',
}

@Index('action_pkey', ['id'], { unique: true })
@Entity()
@TableInheritance({
  column: { type: 'enum', enum: ActionCategory, name: 'category' },
})
export class Action {
  @PrimaryGeneratedColumn({
    name: 'action_id',
    type: 'bigint',
  })
  readonly id: number

  @Column({
    name: 'category',
    type: 'enum',
    enum: ActionCategory,
    default: ActionCategory.SYSTEM
  })
  readonly category: ActionCategory
}

@ChildEntity(ActionCategory.SYSTEM)
export class SystemAction extends Action {
  @Column({ name: 'message', type: 'varchar', nullable: true })
  readonly message?: string
}

@ChildEntity(ActionCategory.EMAIL)
export class EmailAction extends Action {
  @Column({ name: 'email', type: 'varchar', nullable: true })
  readonly email?: string
}

…in any TypeORM project you can see the errors for yourself.

My Environment

Dependency	Version
Operating System	TempleOS
Node.js version	v14.12.0
Typescript version	v4.1.3
TypeORM version	v0.2.29

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.

[rbutera]

So I was able to circumvent this issue by specifying the column name in the TableInheritance decoration:

@TableInheritance({
  column: 'category',
})

this worked fine when leaving the @Column in the entity:

export class Action extends Timestamped {
  @PrimaryGeneratedColumn('uuid', {
    name: 'action_id',
  })
  readonly id: string

  @Column({
    name: 'action_category',
    type: 'enum',
    default: ActionCategory.SYSTEM,
    enum: ActionCategory,
  })
  readonly category: ActionCategory
}

I can close this issue if appropriate, but I think typeORM should have some sort of warning/error for the case where the TableInheritance column name matches the column name of an entity’s explicitly defined columns.

Any pointers for implementing such a warning/error? I’d like to contribute to the project.

[CarlosFandango]

So I was able to circumvent this issue by specifying the column name in the TableInheritance decoration:

@TableInheritance({
  column: 'category',
})

this worked fine when leaving the @Column in the entity:

export class Action extends Timestamped {
  @PrimaryGeneratedColumn('uuid', {
    name: 'action_id',
  })
  readonly id: string

  @Column({
    name: 'action_category',
    type: 'enum',
    default: ActionCategory.SYSTEM,
    enum: ActionCategory,
  })
  readonly category: ActionCategory
}

I can close this issue if appropriate, but I think typeORM should have some sort of warning/error for the case where the TableInheritance column name matches the column name of an entity’s explicitly defined columns.

Any pointers for implementing such a warning/error? I’d like to contribute to the project.

I had this same problem and removing the typing from the @TableInheritance decorator worked a charm! Thanks!

I declared my enum like this:

@Column({
    type: 'enum',
    enum: CourseTypeEnum,
    default: CourseTypeEnum.STUDIO,
  })
  @Field({ nullable: true })
  type!: CourseTypeEnum;