Tree entities

All four of TypeORM's tree strategies work with @Seed: adjacency-list, materialized-path, closure-table, and nested-set. Annotate @TreeParent with @Seed() to seed a parent node, and @TreeChildren with @Seed({ count: N }) to seed children.

@Entity()
@Tree('materialized-path')
class Category {
  @PrimaryGeneratedColumn()
  id!: number

  @Seed(() => faker.commerce.department())
  @Column()
  name!: string

  @Seed()
  @TreeParent()
  parent?: Category

  @Seed({ count: 2 })
  @TreeChildren()
  children!: Category[]
}

const category = await seed(Category).create()
// category.parent   → one Category, no further parent
// category.children → [Category, Category], no further children

const category = await seed(Category).save({ dataSource })
// Persisted and assigned an id

For save() and saveMany() the seeder detects tree entities automatically and persists nodes in the correct order for each strategy: the parent first so it has a DB-assigned ID or path, then the root, then the children. No extra configuration is needed.

Tree depth is limited to one level

The same circular guard that prevents infinite loops on regular relations applies here. When seeding a Category, the parent's own parent is not seeded (because Category is already in the ancestor chain at that point), and each child's own children are not seeded either.

The result is always a flat three-node snapshot: parent → root → [child₁, child₂, …]. Deep or arbitrarily shaped trees cannot be produced by auto-seeding alone — use a @Seeder to build those manually with the TypeORM tree repository API.

Seeded entities always have a parent when @TreeParent is annotated with @Seed()

The seeded entity is never a DB tree root in this case — it always has a parent node. To produce a root, skip the parent at call time:

// No relations at all
const root = await seed(Category).save({ dataSource, relations: false })

// Relations seeded, but parent overridden to undefined
const root = await seed(Category).save({ dataSource, values: { parent: undefined } })

To attach to an existing node in the tree, use values in the same way:

const existing = await dataSource.getTreeRepository(Category).findOneByOrFail({ name: 'Electronics' })
const child = await seed(Category).save({ dataSource, values: { parent: existing } })

Tree entities ​

Tree entities