Support recursive relationships

Problem

Let’s say I have a table called categories. This table can refer to itself as a foreign key with parentCategory. So a categories can have many subcategories, and subcategories can also have subcategories, with an unlimited combination. The idea is to support recursive queries to easily query them along with their sub categories.

Suggested solution

Some valid implementation of something similar to Postgres WITH RECURSIVE https://www.postgresqltutorial.com/postgresql-recursive-query/

Alternatives

N/A

Additional context

N/A

[Southclaws]

If the Prisma team is looking for a real-world example then I have one!

Here’s a schema with a Post model which has repies and also a root post. The reason it’s done this way is so there doesn’t need to be a separate model for “threads” and “posts” it’s all just a “post” and “first” indicates if it’s the first post in a thread.

And here’s a recursive CTE used to count the number of replies to threads (posts with “first” set to true)

If this could be expressed purely via Prisma, that would be awesome! I already hate the complexity and lack of composability with SQL syntax, but recursive CTEs are a special kind of hell!

[polypixeldev]

But isn’t this working already?

model Category {
  id                     Int      @id @default(autoincrement())
  parent_category_id     Int?
  [...more fields...]

  parentCategory         Category?  @relation("categoriesTocategories_parent_category_id", fields: [parent_category_id], references: [id])
  childCategory          Category[] @relation("categoriesTocategories_parent_category_id")

  @@map("categories")
}

I use this very often and never had problems.

I haven’t had an issue with recursive relationships in the schema, but querying them is the feature we’re looking for. How do you query your categories, since the depth is unknown?