Ambiguous relations inside nested createMany

[danprince]

Question

We have a few instances where we create nested related models which reference a DB generated UUID and Prisma is able to figure out which field to populate (presumably because we've defined a single relation field).

Let's look at a specific example where the IDs are known ahead of time.

db.animals.create({
  data: {
    id: "p",
    name: "Panda",
    eats: {
      createMany: {
        data: [
          {
            animalId: "p",
            name: "Bamboo"
          }
        ]
      }
    }
  }
})

Prisma has enough context to infer the animalId because animalId is defined as a relation in the Eats model , meaning writing it out explicitly inside the createMany is redundant.

This makes sense, but I'm less sure how to handle the case where the outer model ID is generated by the database and the inner model has two references to the outer model.

Imagine there's also a Likes model.

model Animal {
  // ...
  
  likesFrom Likes[] @relation(...)
  likesTo Likes[] @relation(...)
}

model Likes {
  fromAnimalId String @db.Uuid
  toAnimalId String @db.Uuid
  
  fromAnimal Animal @relation(...)
  toAnimal Animal @relation(...)
}

If we want to create likes when we create an animal, how can we specify which relation is inferred?

db.animals.create({
  data: {
    name: "Panda",
    likes: {
      createMany: {
        data: [
          {
            fromAnimalId: "?", // I want this to be inferred
            toAnimalId: "f",
          }
        ]
      }
    }
  }
})

Instinctively I'm looking for a way to mark the fromAnimalId as the default relation, or expecting the type signature to mean that you have to specify exactly one of the relations and have the other one inferred, but no dice with either option.

The only option I can currently see that doesn't involve splitting the query into multiple round trips would be to generate the IDs at the server instead of at the database, but we're using DB generated IDs everywhere else in our application and I'd prefer not to change that precedent.

[danprince]

Apparently I was having a slow day. The relation you use disambiguates. Using likesFrom will infer the toId and using likesTo will infer the fromId. 🤦