connectOrCreate deletes old relation and creates a new one

Bug description

When there are prisma models that have an optional one-to-one relation and you are updating one of those models the connectOrCreate has unexpected behavior.

const item = await prisma.item.create({
    data: {name: 'Item 1'},
  })
  const myModel = await prisma.myModel.create({
    data: {
      name: 'MyModel 1',
      item: {connect: {id: item.id}}
    }
  })

  await prisma.item.update({
    where: {
      id: item.id
    },
    data: {
      name: 'Updated Item 1',
      myModel: {
        connectOrCreate: {
          where: {
            itemId: item.id
          },
          create: {
            name: 'MyModel 2'
          }
        }
      }
    }
  })

The result of the above code is two MyModels in the DB and the original ‘MyModel 1’ has been disconnected from its item and replaced with ‘MyModel 2’.

In our real world example at the time of executing this query we don’t currently know if the Item is connected to an existing MyModel and we are trying to avoid calling the DB to check if there is a MyModel already connected to manually perform the function that connectOrCreate should perform.

Thanks in advance for the help!!

How to reproduce

1. Clone this example repository.
2. Setup your DB, generate client, and run migrations.
3. Run node index.js

Observe the output where you can see the following:

MyModel 1 has been correctly linked to item with id e4767238-0a96-4b3b-83c8-56af27c7e741
All MyModels after connectOrCreate [
  {
    id: '4e29d553-c8c9-49d6-9949-f5c683374f3f',
    name: 'MyModel 1',
    itemId: null
  },
  {
    id: '2dc291ac-8875-4dfb-99cc-e86799039384',
    name: 'MyModel 2',
    itemId: 'e4767238-0a96-4b3b-83c8-56af27c7e741'
  }
]
There should only be one MyModel in the DB!!!

Expected behavior

When connectOrCreate-ing and the model is found via a where statement that uses the linking id column, then maintain that connection instead of creating a new model.

Prisma information

datasource db {
  provider = "postgresql"
  url      = "postgresql://testuser:testpw@localhost:5432/testdb?schema=public"
}

generator client {
  provider      = "prisma-client-js"
  binaryTargets = ["native", "rhel-openssl-1.0.x"]
}


model MyModel {
  id                         String              @id @default(uuid())
  name                       String
  itemId String?             @unique
  item   Item?               @relation(references: [id], fields: [itemId])

}

model Item {
  id           String              @id @default(uuid())
  name         String
  myModel      MyModel?
}

Environment & setup

• OS: Mac OS
• Database: PostgreSQL
• Node.js version: v16.13.2

Prisma Version

prisma                  : 3.9.1
@prisma/client          : 3.9.1
Current platform        : darwin-arm64
Query Engine (Node-API) : libquery-engine bcc2ff906db47790ee902e7bbc76d7ffb1893009 (at node_modules/@prisma/engines/libquery_engine-darwin-arm64.dylib.node)
Migration Engine        : migration-engine-cli bcc2ff906db47790ee902e7bbc76d7ffb1893009 (at node_modules/@prisma/engines/migration-engine-darwin-arm64)
Introspection Engine    : introspection-core bcc2ff906db47790ee902e7bbc76d7ffb1893009 (at node_modules/@prisma/engines/introspection-engine-darwin-arm64)
Format Binary           : prisma-fmt bcc2ff906db47790ee902e7bbc76d7ffb1893009 (at node_modules/@prisma/engines/prisma-fmt-darwin-arm64)
Default Engines Hash    : bcc2ff906db47790ee902e7bbc76d7ffb1893009
Studio                  : 0.457.0

[Jackman3005]

@janpio I don’t think this is new behavior. We recently upgraded to 3.9.2 and had it in our old version as well (3.2.1).

[sreuter]

Amazing work, thank you @dpetrick! 🙏