# Expand-and-contract migrations (Prisma ORM v7) (/docs/guides/v7/database/data-migration)

> For the complete Prisma documentation index, see [llms.txt](https://www.prisma.io/docs/llms.txt). A markdown version of any docs page is available by appending `.md` to its URL.

Learn how to perform data migrations using the expand and contract pattern with Prisma ORM

Location: Guides > v7 > Database > Expand-and-contract migrations

## Introduction [#introduction]

When you change your database schema in production, you need to keep the data consistent and avoid downtime. This guide shows you how to use the expand and contract pattern to safely migrate data between columns. The example replaces a boolean field with an enum field while preserving existing data.

## Prerequisites [#prerequisites]

Before starting this guide, make sure you have:

* Node.js installed (version 20 or higher)
* A Prisma ORM project with an existing schema
* A supported database (PostgreSQL, MySQL, SQLite, SQL Server, etc.)
* Access to both development and production databases
* Basic understanding of Git branching
* Basic familiarity with TypeScript

## 1. Set up your environment [#1-set-up-your-environment]

### 1.1. Review initial schema [#11-review-initial-schema]

Start with a basic schema containing a Post model:

```prisma
generator client {
  provider = "prisma-client"
  output   = "./generated/prisma"
}

datasource db {
  provider = "postgresql"
}

model Post {
  id        Int     @id @default(autoincrement())
  title     String
  content   String?
  published Boolean @default(false)
}
```

### 1.2. Configure Prisma [#12-configure-prisma]

Create a `prisma.config.ts` file in the root of your project with the following content:

```typescript title="prisma.config.ts"
import "dotenv/config";
import { defineConfig, env } from "prisma/config";

export default defineConfig({
  schema: "prisma/schema.prisma",
  migrations: {
    path: "prisma/migrations",
  },
  datasource: {
    url: env("DATABASE_URL"),
  },
});
```

> [!NOTE]
> You'll need to install the required packages. If you haven't already, install them using your package manager:
> 
> 
>   
> 
>   #### bun

>     ```bash
>     bun add prisma@prev tsx @types/pg --dev
>     ```
>
> 
>   #### pnpm

>     ```bash
>     pnpm add prisma@prev tsx @types/pg --save-dev
>     ```
>
> 
>   #### yarn

>     ```bash
>     yarn add prisma@prev tsx @types/pg --dev
>     ```
>
> 
>   #### npm

>     ```bash
>     npm install prisma@prev tsx @types/pg --save-dev
>     ```
>
> 
> 
> 
>   
> 
>   #### bun

>     ```bash
>     bun add @prisma/client@7 @prisma/adapter-pg pg dotenv
>     ```
>
> 
>   #### pnpm

>     ```bash
>     pnpm add @prisma/client@7 @prisma/adapter-pg pg dotenv
>     ```
>
> 
>   #### yarn

>     ```bash
>     yarn add @prisma/client@7 @prisma/adapter-pg pg dotenv
>     ```
>
> 
>   #### npm

>     ```bash
>     npm install @prisma/client@7 @prisma/adapter-pg pg dotenv
>     ```
>
> 
> 
> If you are using a different database provider (MySQL, SQL Server, SQLite), install the corresponding driver adapter package instead of `@prisma/adapter-pg`. For more information, see [Database drivers](https://www.prisma.io/docs/orm/v7/core-concepts/supported-databases/database-drivers).

### 1.3. Create a development branch [#13-create-a-development-branch]

Create a new branch for your changes:

```bash
git checkout -b create-status-field
```

## 2. Expand the schema [#2-expand-the-schema]

### 2.1. Add new column [#21-add-new-column]

Update your schema to add the new Status enum and field:

```prisma
model Post {
  id        Int      @id @default(autoincrement())
  title     String
  content   String?
  published Boolean? @default(false)
  status    Status   @default(Unknown)
}

enum Status {
  Unknown
  Draft
  InProgress
  InReview
  Published
}
```

### 2.2. Create migration [#22-create-migration]

Generate the migration:

  

#### bun

```bash
bunx prisma migrate dev --name add-status-column
```

#### pnpm

```bash
pnpm prisma migrate dev --name add-status-column
```

#### yarn

```bash
yarn prisma migrate dev --name add-status-column
```

#### npm

```bash
npx prisma migrate dev --name add-status-column
```

Then generate Prisma Client:

  

#### bun

```bash
bunx prisma generate
```

#### pnpm

```bash
pnpm prisma generate
```

#### yarn

```bash
yarn prisma generate
```

#### npm

```bash
npx prisma generate
```

## 3. Migrate the data [#3-migrate-the-data]

### 3.1. Create migration script [#31-create-migration-script]

Create a new TypeScript file for the data migration:

```typescript
import { PrismaClient } from "../generated/prisma/client";
import { PrismaPg } from "@prisma/adapter-pg";
import "dotenv/config";

const adapter = new PrismaPg({
  connectionString: process.env.DATABASE_URL,
});

const prisma = new PrismaClient({
  adapter,
});

async function main() {
  await prisma.$transaction(async (tx) => {
    const posts = await tx.post.findMany();
    for (const post of posts) {
      await tx.post.update({
        where: { id: post.id },
        data: {
          status: post.published ? "Published" : "Unknown",
        },
      });
    }
  });
}

main()
  .catch(async (e) => {
    console.error(e);
    process.exit(1);
  })
  .finally(async () => await prisma.$disconnect());
```

### 3.2. Set up migration script [#32-set-up-migration-script]

Add the migration script to your package.json:

```json
{
  "scripts": {
    "data-migration:add-status-column": "tsx ./prisma/migrations/<migration-timestamp>/data-migration.ts"
  }
}
```

### 3.3. Execute migration [#33-execute-migration]

1. Update your DATABASE_URL to point to the production database
2. Run the migration script:

  

#### bun

```bash
bun run data-migration:add-status-column
```

#### pnpm

```bash
pnpm run data-migration:add-status-column
```

#### yarn

```bash
yarn data-migration:add-status-column
```

#### npm

```bash
npm run data-migration:add-status-column
```

## 4. Contract the schema [#4-contract-the-schema]

### 4.1. Create cleanup branch [#41-create-cleanup-branch]

Create a new branch for removing the old column:

```bash
git checkout -b drop-published-column
```

### 4.2. Remove old column [#42-remove-old-column]

Update your schema to remove the published field:

```prisma
model Post {
  id      Int      @id @default(autoincrement())
  title   String
  content String?
  status  Status   @default(Draft)
}

enum Status {
  Draft
  InProgress
  InReview
  Published
}
```

### 4.3. Generate cleanup migration [#43-generate-cleanup-migration]

Create and run the final migration:

  

#### bun

```bash
bunx prisma migrate dev --name drop-published-column
```

#### pnpm

```bash
pnpm prisma migrate dev --name drop-published-column
```

#### yarn

```bash
yarn prisma migrate dev --name drop-published-column
```

#### npm

```bash
npx prisma migrate dev --name drop-published-column
```

Then generate Prisma Client:

  

#### bun

```bash
bunx prisma generate
```

#### pnpm

```bash
pnpm prisma generate
```

#### yarn

```bash
yarn prisma generate
```

#### npm

```bash
npx prisma generate
```

## 5. Deploy to production [#5-deploy-to-production]

### 5.1. Set up deployment [#51-set-up-deployment]

Add the following command to your CI/CD pipeline:

  

#### bun

```bash
bunx prisma migrate deploy
```

#### pnpm

```bash
pnpm prisma migrate deploy
```

#### yarn

```bash
yarn prisma migrate deploy
```

#### npm

```bash
npx prisma migrate deploy
```

### 5.2. Monitor deployment [#52-monitor-deployment]

Watch for any errors in your logs and monitor your application's behavior after deployment.

## Troubleshooting [#troubleshooting]

### Common issues and solutions [#common-issues-and-solutions]

1. **Migration fails due to missing default**
   * Ensure you've added a proper default value
   * Check that all existing records can be migrated

2. **Data loss prevention**
   * Always backup your database before running migrations
   * Test migrations on a copy of production data first

3. **Transaction rollback**
   * If the data migration fails, the transaction will automatically rollback
   * Fix any errors and retry the migration

## Next steps [#next-steps]

Now that you've completed your first expand and contract migration, you can:

* Learn more about [Prisma Migrate](https://www.prisma.io/docs/orm/v7/prisma-migrate)
* Explore [schema prototyping](https://www.prisma.io/docs/orm/v7/prisma-migrate/workflows/prototyping-your-schema)
* Understand [customizing migrations](https://www.prisma.io/docs/orm/v7/prisma-migrate/workflows/customizing-migrations)

For more information:

* [Expand and Contract Pattern Documentation](https://www.prisma.io/dataguide/types/relational/expand-and-contract-pattern)
* [Prisma Migrate Workflows](https://www.prisma.io/docs/orm/v7/prisma-migrate/workflows/development-and-production)

## Related pages

- [`Multiple databases`](https://www.prisma.io/docs/guides/v7/database/multiple-databases): Learn how to use multiple Prisma Clients in a single app to connect to multiple databases, handle migrations, and deploy your application to Vercel
- [`Schema management in teams`](https://www.prisma.io/docs/guides/v7/database/schema-changes): Learn how to use Prisma Migrate effectively when collaborating on a project as a team