Prisma•9mo ago

children and favourite child (ambiguous relation)

I want to model a relationship where a parent record can have many children but there is also a 'favourite' (or 'current favourite') child out of the list of children indicated by an id reference in the parent, to the child. I realise that this is a bit of a circular relationship and care will need to be taken when removing children or changing the favourite but I think the efficiency in query performance is worth the effort. Here is a contrived example...

model Parent {
  id                 Int         @id @default(autoincrement())
  
  favourite_child_id Int
  favourite_child    Child       @relation(fields: [favourite_child_id], references: [id])

  children           Child[]

  @@map("parent")
}

model Child {
  id              Int         @id @default(autoincrement())

  parent_id       Int
  parent          Parent   @relation(fields: [parent_id], references: [id])

  @@map("child")
}

model Parent {
  id                 Int         @id @default(autoincrement())
  
  favourite_child_id Int
  favourite_child    Child       @relation(fields: [favourite_child_id], references: [id])

  children           Child[]

  @@map("parent")
}

model Child {
  id              Int         @id @default(autoincrement())

  parent_id       Int
  parent          Parent   @relation(fields: [parent_id], references: [id])

  @@map("child")
}

This according to my brain should be fine but Prisma complains

Error: Prisma schema validation - (validate wasm)
Error code: P1012
error: Error validating model "Parent": Ambiguous relation detected. The fields `favourite_child` and `children` in model `Parent` both refer to `Child`. Please provide different relation names for them by adding `@relation(<name>).
  -->  schema.prisma:280
   | 
279 |   favourite_child_id Int
280 |   favourite_child    Child       @relation(fields: [favourite_child_id], references: [id])
281 | 
   |

Error: Prisma schema validation - (validate wasm)
Error code: P1012
error: Error validating model "Parent": Ambiguous relation detected. The fields `favourite_child` and `children` in model `Parent` both refer to `Child`. Please provide different relation names for them by adding `@relation(<name>).
  -->  schema.prisma:280
   | 
279 |   favourite_child_id Int
280 |   favourite_child    Child       @relation(fields: [favourite_child_id], references: [id])
281 | 
   |

I have tried a number of iterations of this including naming the relations and adding back references etc, all of which just introduce even more validation issues. Any Ideas how I can make Prisma happy with this approach?

1 Reply

JavascriptMickOP•9mo ago

ok, never mind I figured it out. I want to apologise to anybody who is triggered by this example. I know these type of relationships can be fraught and vexxed. I only seek to understand.

model Parent {
  id                 Int         @id @default(autoincrement())
  
  favourite_child_id Int
  favourite_child    Child       @relation("ParentHasFavourite", fields: [favourite_child_id], references: [id])

  children           Child[]     @relation("ParentHasChildren")

  @@map("parent")
}

model Child {
  id              Int         @id @default(autoincrement())

  parent_id       Int
  parent          Parent   @relation("ParentHasChildren", fields: [parent_id], references: [id])

  parents_who_love_me_most Parent[] @relation("ParentHasFavourite")

  @@map("child")
}

model Parent {
  id                 Int         @id @default(autoincrement())
  
  favourite_child_id Int
  favourite_child    Child       @relation("ParentHasFavourite", fields: [favourite_child_id], references: [id])

  children           Child[]     @relation("ParentHasChildren")

  @@map("parent")
}

model Child {
  id              Int         @id @default(autoincrement())

  parent_id       Int
  parent          Parent   @relation("ParentHasChildren", fields: [parent_id], references: [id])

  parents_who_love_me_most Parent[] @relation("ParentHasFavourite")

  @@map("child")
}

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children and favourite child (ambiguous relation)