Prisma•2d ago

Relations on non unique fields

Hi guys, i'm building a new db and i need it to be multilingual. in order to achieve that i've created a contents table wich will handle every text/image for each language

model Contents {
  id         Int
  language   Languages
  content    String
  content_id Int
  type       ContentType
  challenges_names Challenges[] @relation("challenges_name_content")
  challenges_logo Challenges[] @relation("challenges_logo_content")
  challenges_badges Challenges[] @relation("challenges_badge_content")
  challenges_chapters_name Challenges_Chapters[]

  @@id([id])
  @@index([content_id])
  @@schema("system")
  @@unique([content_id, language])
}

model Contents {
  id         Int
  language   Languages
  content    String
  content_id Int
  type       ContentType
  challenges_names Challenges[] @relation("challenges_name_content")
  challenges_logo Challenges[] @relation("challenges_logo_content")
  challenges_badges Challenges[] @relation("challenges_badge_content")
  challenges_chapters_name Challenges_Chapters[]

  @@id([id])
  @@index([content_id])
  @@schema("system")
  @@unique([content_id, language])
}

Thanks to the content_id column i can join on the needed text and filter by language, that will come from the client basically id content_id language content 1 1 en hello 2 1 it ciao 3 1 es hola Now i can create my challenges modules and have a relation with Contents module like this

model Challenges {
  id Int
  name_content Contents @relation("challenges_name_content", fields: [name_content_id], references: [content_id])  
  name_content_id Int
  logo_content Contents @relation("challenges_logo_content", fields: [logo_content_id], references: [content_id])
  logo_content_id Int
  badge_content Contents @relation("challenges_badge_content", fields: [badge_content_id], references: [content_id])
  badge_content_id Int
  color String
  secondary_color String
  super_challenge_json Json[]
  countries Json[]

  chapters Challenges_Chapters[]

  @@id([id])

  @@schema("system")
}

model Challenges {
  id Int
  name_content Contents @relation("challenges_name_content", fields: [name_content_id], references: [content_id])  
  name_content_id Int
  logo_content Contents @relation("challenges_logo_content", fields: [logo_content_id], references: [content_id])
  logo_content_id Int
  badge_content Contents @relation("challenges_badge_content", fields: [badge_content_id], references: [content_id])
  badge_content_id Int
  color String
  secondary_color String
  super_challenge_json Json[]
  countries Json[]

  chapters Challenges_Chapters[]

  @@id([id])

  @@schema("system")
}

but i get this error Error parsing attribute "@relation": The argument references must refer to a unique criterion in the related model. Consider adding an @unique attribute to the field content_id in the model Contents.Prisma for each relation constraint. How can i deal with this?

2 Replies

Prisma AI Help•2d ago

You selected the bot's instantaneous insights. Let me compile your answer right away! The error you're encountering is because Prisma requires that the field referenced in a @relation attribute must be unique in the related model. In your case, you're trying to reference content_id in the Contents model, but this field isn't unique by itself - it's only unique when combined with language as part of a composite unique constraint. There are a few ways to solve this: Option 1: Reference the composite unique fields You need to reference both fields that make up your unique constraint:

model Challenges {
  id Int
  name_content Contents @relation("challenges_name_content", fields: [name_content_id, language], references: [content_id, language])  
  name_content_id Int
  language Languages
  // other fields...
  
  @@id([id])
  @@schema("system")
}

model Challenges {
  id Int
  name_content Contents @relation("challenges_name_content", fields: [name_content_id, language], references: [content_id, language])  
  name_content_id Int
  language Languages
  // other fields...
  
  @@id([id])
  @@schema("system")
}

This approach requires you to store the language in the Challenges model as well. Option 2: Make content_id unique If you want to keep your current structure, you could make content_id unique in the Contents model:

model Contents {
  // other fields...
  content_id Int @unique
  // rest of model...
}

model Contents {
  // other fields...
  content_id Int @unique
  // rest of model...
}

However, this would change your data model significantly, as you could no longer have multiple languages for the same content_id. Option 3: Use a join model Create an intermediate model to handle the many-to-many relationship between challenges and contents. This is a common issue when working with relations in Prisma. As noted in the documentation, "The argument references must refer to a unique criterion in the related model" One-to-many relations. For MySQL specifically, Prisma enforces this uniqueness requirement since version 4.0.0 What's new in Prisma? (Q2/22). Given your multilingual requireme nts, Option 1 is likely the most appropriate solution as it maintains your data model while satisfying Prisma's constraints. 🤔 Alright, thanks for letting us know that there's still some help needed. A team member will reply to you shortly. In the meantime, please let us know any additional info, questions, or which parts of the answer may need clarification.

ALESSIOOP•15h ago

Prisma AI, i can't use both solution 1 or 2

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Relations on non unique fields

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