Referential actions upgrade path

The following behavior applies in Prisma versions 2.x.

When invoking the delete() or deleteAll() methods using the Prisma Client on required relations, a runtime check is performed and the deletion of records prevented if they are referencing related objects. This prevents cascade behavior, no matter how the foreign key is defined.

The behavior in Prisma 2, without upgrading, does not allow setting referential actions at all. See Prisma 2.x default referential actions

If you need to actually use the cascade behavior configured in the database, you can use raw SQL queries to delete multiple referenced records. This is because the Prisma Client will not perform runtime checks on raw queries.

Prisma 3 lets you control what should happen when deleting or updating records by explicitly settings referential actions on your models' relations. After the upgrade, the Prisma Client will not enforce any referential actions anymore, and any action written to the database foreign keys will define the behavior when deleting or updating records.

Prisma Migrate 3.x will use the actions previously done by the Prisma Client as the new default when writing the foreign key constraints to the database.

Prisma 2.x default referential actions

Below are the default referential actions written to the database foreign keys when using Prisma Migrate versions 2.x:

ClauseOptional relationsMandatory relations
onDeleteSetNullCascade
onUpdateCascadeCascade

On top of the database referential actions, the following actions are enforced in Prisma Client versions 2.x:

ClauseOptional relationsMandatory relations
onDeleteSetNullRestrict
onUpdateCascadeCascade

Upgrade paths

There are a couple of paths you can take when upgrading which will give different results depending on the desired outcome.

If you currently use the migration workflow, you can run prisma db pull to check how the defaults are reflected in your schema. You can then manually update your database if you need to.

You can also decide to skip checking the defaults and run a migration to update your database with the new default values.

Using Introspection

If you Introspect your database, the referential actions configured at the database level will be reflected in your Prisma Schema. If you have been using Prisma Migrate or prisma db push to manage the database schema, these are likely to be the <=2.25.0 default values.

When you run an Introspection, Prisma compares all the foreign keys in the database with the schema, if the SQL statements ON DELETE and ON UPDATE do not match the default values, they will be explicitly set in the schema file.

After introspecting, you can review the non-default clauses in your schema. The most important clause to review is onDelete, which defaults to Cascade in version 2.25.0 and earlier.

If you are using either the delete() or deleteAll() methods, cascading deletes will now be performed, as the safety net in Prisma Client that previously prevented cascading deletes at runtime is removed. Be sure to check your code and make any adjustments accordingly.

Make sure you are happy with every case of onDelete: Cascade in your schema. If not, either:

  • Modify your Prisma schema and db push or dev migrate to change the database or
  • Manually update the underlying database if you only use prisma db pull in your workflow

The following example would result in a cascading delete, meaning that if the User is deleted then all of their Post's will be deleted too.

A blog schema example

model Post {
id Int @id @default(autoincrement())
title String
author User @relation(fields: [authorId], references: [id], onDelete: Cascade)
authorId Int
}
model User {
id Int @id @default(autoincrement())
posts Post[]
}

Using Migration

When running a Migration (or the prisma db push command) the new defaults will be applied to your database.

Unlike when you run prisma db pull for the first time, the new referential actions clause and property will not automatically be added to your Prisma schema by the Prisma VSCode extension. You will have to manually add them if you wish to use anything other than the new defaults.

Explicitly defining referential actions in your Prisma schema is optional. If you do not explicitly define a referential action for a relation, Prisma uses the new defaults.

Note that referential actions can be added on a case by case basis. This means that you can add them to one single relation and leave the rest set to the defaults by not manually specifying anything.

Checking for errors

Before upgrading to version 3.0.1 (or versions 2.26.0 and above with the referentialActions feature flag enabled), Prisma prevented the deletion of records while using delete() or deleteMany() to preserve referential integrity. A custom runtime error would be thrown by the Prisma Client with the error code P2014.

After upgrading, Prisma no longer performs runtime checks. You can instead specify a custom referential action to preserve the referential integrity between relations.

When you use NoAction or Restrict to prevent the deletion of records, the error messages will be different in versions 3.0.1 and above (or 2.26.0 with the referentialActions feature flag enabled) compared to versions prior to that. This is because they are now triggered by the database and not the Prisma Client. The new error code that can be expected is P2003, so you should check your code to make adjustments accordingly.

Example of catching errors

The following example uses the below blog schema with a 1-m relationship between Post and User and sets a Restrict referential actions on the author field.

This means that if a user has a post, that user (and their posts) cannot be deleted.

schema.prisma
1model Post {
2 id Int @id @default(autoincrement())
3 title String
4 author User @relation(fields: [authorId], references: [id], onDelete: Restrict)
5 authorId String
6}
7
8model User {
9 id Int @id @default(autoincrement())
10 posts Post[]
11}

Prior to upgrading, the error code you would receive when trying to delete a user which has posts would be P2014 and it's message:

"The change you are trying to make would violate the required relation '{relation_name}' between the {model_a_name} and {model_b_name} models."

import { PrismaClient } from '@prisma/client'
const prisma = new PrismaClient()
async function main() {
try {
await prisma.user.delete({
where: {
id: 'some-long-id',
},
})
} catch (error) {
if (error instanceof Prisma.PrismaClientKnownRequestError) {
if (error.code === 'P2014') {
console.log(error.message)
}
}
}
}
main()
.catch((e) => {
throw e
})
.finally(async () => {
await prisma.$disconnect()
})

To make sure you are checking for the correct errors in your code, modify your check to look for P2003, which will deliver the message:

"Foreign key constraint failed on the field: {field_name}"

import { PrismaClient } from '@prisma/client'
const prisma = new PrismaClient()
async function main() {
try {
await prisma.user.delete({
where: {
id: 'some-long-id'
}
})
} catch (error) {
if (error instanceof Prisma.PrismaClientKnownRequestError) {
if (error.code === 'P2014') {
if (error.code === 'P2003') {
console.log(error.message)
}
}
}
}
main()
.catch(e => {
throw e
})
.finally(async () => {
await prisma.$disconnect()
})
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