Relations over composite types

[pimeys]

If we have referential integrity handled in Prisma, we could have relations from composite types.

[maxime4000]

Let's said we have this model:

datasource db {
  provider = "mongodb"
  url      = env("DB_URL")
}

generator client {
  provider = "prisma-client-js"
}

model Country {
  id     String         @id @default(auto()) @map("_id") @db.ObjectId
  code   String
  name   String
  states CountryState[]
}

type CountryState {
  id        String @default(auto()) @db.ObjectId
  name      String
  stateCode String
  // Error validating: Defining `@relation` attribute for a field in a composite type is not allowed.
  taxe      Taxe?   @relation(fields: [taxeId], references: [id])
  taxeId    String? @db.ObjectId
}

model Taxe {
  id        String       @id @default(auto()) @map("_id") @db.ObjectId
  countryId String       @db.ObjectId
  country   Country      @relation(fields: [countryId], references: [id])
  state     CountryState @relation(fields: [stateId], references: [id])
  stateId   String       @db.ObjectId
  // ...
}

Could relations over compositeTypes work something like that ?

Our actual use case is to embedded a lightweight copy of the State and Country in Taxe (ex: {id, name, value}). So we have a Composite Type for TaxeCountry and TaxeState. Tbh, I'm not sure if what I wrote is optimized, embedding data is faster than referencing, but I would like to be able to fetch taxe from Countries' States. Because Country own multiple composite Type of CountryState, I cannot lookup Taxe from CountryState. Could do in a raw query format, but hey, if I don't have to, would be better.

If I change CountryState to model, I can remove countryId in Taxe and just reference the State. Being able to get the country coming from Taxe, which is what I could want here.

Note: I know the model wouldn't benefit much of nesting value for optimization, but I'm asking because we have better use case that would benefit having @relation in nested data.

[janpio]

While doing some research for #20217 I stumbled over the fact that MongoDB does support indexes on composite types / embedded documents, but not unique indexes:

https://www.mongodb.com/community/forums/t/unique-indexes-on-embedded-documents/16825
https://www.mongodb.com/community/forums/t/building-unique-index-on-array-of-embedded-documents/105981

That would be something to figure out when we implement this, as 1:1 relations are enforced via @unique.

[edobrb]

Hi, does anyone know if this issue will be included in the roadmap or if it will be left behind?