How to Implement an Optional One-to-One Relationship in Prisma with MongoDB?

Context

I'm using Prisma 5.10.2 with MongoDB and attempting to set up an optional one-to-one relationship between two models based on the official Prisma documentation. However, I've encountered a problem with MongoDB's support for nullable unique fields.

Models

Here are the models I'm using (the ones recommended in the docs actually)

model User {
  id        String   @id @default(auto()) @map("_id") @db.ObjectId
  profile   Profile? @relation(fields: [profileId], references: [id])
  profileId String?  @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   String @id @default(auto()) @map("_id") @db.ObjectId
  user User?
}

model User {
  id        String   @id @default(auto()) @map("_id") @db.ObjectId
  profile   Profile? @relation(fields: [profileId], references: [id])
  profileId String?  @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   String @id @default(auto()) @map("_id") @db.ObjectId
  user User?
}

`

Issue
MongoDB does not support "nullable uniques," which means that users without a profile (where the profile property is null) are not unique and cause write operations to fail.

Possible Solutions I've Considered

- Changing to a One-to-Many Relationship: Modify the User model to handle an array of profiles but only use the first item. This approach seems hacky as it deviates from the intended one-to-one relationship structure.

- Making the Profile Required: This would ensure uniqueness but defeats the purpose of the relationship being optional.

Question
Is there a standard approach to implementing optional one-to-one relationships in Prisma with MongoDB that avoids these issues, or is adapting one of the hacky solutions the only way?

I'm relatively new to this (been learning for about 8 months), so any guidance or alternative suggestions would be greatly appreciated.

Thank you!

Prisma•2y ago•

3 replies

Risatoga

How to Implement an Optional One-to-One Relationship in Prisma with MongoDB?

model User {
  id        String   @id @default(auto()) @map("_id") @db.ObjectId
  profile   Profile? @relation(fields: [profileId], references: [id])
  profileId String?  @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   String @id @default(auto()) @map("_id") @db.ObjectId
  user User?
}

model User {
  id        String   @id @default(auto()) @map("_id") @db.ObjectId
  profile   Profile? @relation(fields: [profileId], references: [id])
  profileId String?  @unique @db.ObjectId // relation scalar field (used in the `@relation` attribute above)
}

model Profile {
  id   String @id @default(auto()) @map("_id") @db.ObjectId
  user User?
}

How to Implement an Optional One-to-One Relationship in Prisma with MongoDB?

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