Automatic Prisma migrations

Vitess

June 21, 2023

Note

This document has been updated to include the recommended Prisma and PlanetScale workflow, specifically the recommendation to use prisma db push instead of prisma migrate dev with shadow branches. Also, you previously needed to turn on the ability to automatically copy the Prisma migration metadata. You no longer need to do this. Read more below.

Introduction

In this tutorial, we're going to learn how to do Prisma migrations in PlanetScale as part of your deployment process using prisma db push.

Quick introduction to Prisma's db push

From a high level, Prisma's db push introspects your PlanetScale database to infer and execute the changes required to make your database schema reflect the state of your Prisma schema. When prisma db push is run, it will ensure the schema in the PlanetScale branch you are currently connected to matches your current Prisma schema.

We recommend prisma db push over prisma migrate dev for the following reasons:

PlanetScale provides Online Schema Changes that are deployed automatically when you merge a deploy request and prevents blocking schema changes that can lead to downtime. This is different from the typical Prisma workflow which uses prisma migrate in order to generate SQL migrations for you based on changes in your Prisma schema. When using PlanetScale with Prisma, the responsibility of applying the changes is on the PlanetScale side. Therefore, there is little value to using prisma migrate with PlanetScale.

Also, the migrations table created when prisma migrate runs can also be misleading since PlanetScale does the actual migration when the deploy request is merged, not when prisma migrate is run which only updates the schema in the development database branch. You can still see the history of your schema changes in PlanetScale.

Prerequisites

Add Prisma to your project using npm install prisma --save-dev or yarn add prisma --dev (depending on what package manager you prefer).
Run npx prisma init inside of your project to create the initial files needed for Prisma.
Install the PlanetScale CLI.
Authenticate the CLI with the following command:

pscale auth login

Execute your first Prisma db push

Prisma migrations follow the PlanetScale non-blocking schema change workflow. First, the schema is applied to a development branch and then the development branch is merged into the main production database.

Let's begin with an example flow for running Prisma migrations in PlanetScale:

Create a new prisma-playground database:
```
pscale db create prisma-playground
```
Connect to the database branch:
```
pscale connect prisma-playground main --port 3309
```
Note
This step assumes you created a new PlanetScale database and have not yet enabled Safe Migrations on the main branch. You will need to create a new development branch otherwise.

Update your prisma/schema.prisma file with the following schema:

Note

In Prisma 4.5.0, referentialIntegrity changed to relationMode and became generally available in 4.7.0. The following schema reflects this change.

You can learn more about Prisma's Relation mode in the Prisma docs.

datasource db {
  provider = "mysql"
  url      = env("DATABASE_URL")
  relationMode = "prisma"
}

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

model Post {
  id        Int      @default(autoincrement()) @id
  createdAt DateTime @default(now())
  updatedAt DateTime @updatedAt
  title     String   @db.VarChar(255)
  content   String?
  published Boolean  @default(false)
  author    User     @relation(fields: [authorId], references: [id])
  authorId  Int
}

model Profile {
  id     Int     @default(autoincrement()) @id
  bio    String?
  user   User    @relation(fields: [userId], references: [id])
  userId Int     @unique
}

model User {
  id      Int      @default(autoincrement()) @id
  email   String   @unique
  name    String?
  posts   Post[]
  profile Profile?
}

Update your .env file:

DATABASE_URL="mysql://root@127.0.0.1:3309/prisma-playground"

In another terminal, use the db push command to push the schema defined in prisma/schema.prisma:
```
npx prisma db push
```
Unlike the prisma migrate dev command, it will not create a migrations folder containing a SQL file with the SQL used to update the schema in your PlanetScale database. PlanetScale will be tracking your migrations in this workflow.
Tip
You can learn more about the prisma db push command in the Prisma docs.
After db push is successful, you can see the table created in your terminal. For example, to see the Post table:
```
pscale shell prisma-playground main
```
```
describe Post;
```
Tip
Use the exit command to exit the MySQL shell.
Or you can see it in the PlanetScale UI under the Schema tab in your main branch.
Finally, turn on safe migrations on the main branch to enable non-blocking schema changes:
```
pscale branch safe-migrations enable prisma-playground main
```

Execute succeeding Prisma migrations in PlanetScale

Our first example migration flow went well, but what happens when you need to run further changes to your schema?

Let's take a look:

Create a new development branch from main called add-subtitle-to-posts:
```
pscale branch create prisma-playground add-subtitle-to-posts
```
Close the proxy connection to your main branch (if still open) and connect to the new add-subtitle-to-posts development branch:
```
pscale connect prisma-playground add-subtitle-to-posts --port 3309
```
In the prisma/schema.prisma file, update the Post model:
Add a new subtitle field to Post:
```
subtitle  String   @db.VarChar(255)
```
Run db push again to update the schema in PlanetScale:
```
npx prisma db push
```
Open a deploy request for your add-subtitle-to-posts branch, so that you can deploy these changes to main.
You can complete the deploy request either in the web app or with the pscale deploy-request command.
```
pscale deploy-request create prisma-playground add-subtitle-to-posts
```
```
pscale deploy-request deploy prisma-playground 1
```
Once the deploy request is merged, you can see the results in your main branch's Post table:
```
pscale shell prisma-playground main
```
```
describe Post;
```

What's next?

Now that you've successfully conducted your first automatic Prisma migration in PlanetScale and know how to handle future migrations, it's time to deploy your application with a PlanetScale database! Let's learn how to deploy an application with a PlanetScale database to Vercel.

Need help?

Get help from the PlanetScale Support team, or join our GitHub discussion board to see how others are using PlanetScale.