Use Prisma Postgres with Bun

Create a new project

First, create a directory and initialize it with bun init.

terminal

mkdir prisma-postgres-app
cd prisma-postgres-app
bun init

Install Prisma dependencies

Then install the Prisma CLI (prisma), Prisma Client (@prisma/client), and the Postgres driver adapter (@prisma/adapter-pg) as dependencies.

terminal

bun add -d prisma
bun add @prisma/client @prisma/adapter-pg

Initialize Prisma with PostgreSQL

Use the Prisma CLI with bunx to initialize the schema and migration directory, with PostgreSQL as the database.

terminal

bunx --bun prisma init --db

This creates a basic schema. Update it to use the Rust-free client optimized for Bun: open prisma/schema.prisma and modify the generator block, then add a User model.

prisma/schema.prisma

generator client {
	provider = "prisma-client"
	output = "../generated/prisma"
	output = "./generated"
	engineType = "client"
	runtime = "bun"
}

datasource db {
	provider = "postgresql"
}

model User { 
	id    Int     @id @default(autoincrement()) 
	email String  @unique
	name  String?
} 

Configure database connection

Set up your Postgres database URL in the .env file.

.env

DATABASE_URL="postgresql://username:password@localhost:5432/mydb?schema=public"

Create and run database migration

Then generate and run the initial migration.The command writes a .sql migration file to prisma/migrations and executes it against your Postgres database. Bun does not load .env automatically when it runs a CLI with --bun, and the prisma.config.ts generated by prisma init reads DATABASE_URL from the environment, so pass --env-file=.env explicitly.

terminal

bun run --bun --env-file=.env prisma migrate dev --name init

Loaded Prisma config from prisma.config.ts.

Prisma schema loaded from prisma/schema.prisma.
Datasource "db": PostgreSQL database "mydb", schema "public" at "localhost:5432"

Applying migration `20250114141233_init`

The following migration(s) have been created and applied from new schema changes:

prisma/migrations/
  └─ 20250114141233_init/
    └─ migration.sql

Your database is now in sync with your schema.

Generate Prisma Client

prisma migrate dev does not generate the Prisma client, so generate it with the Prisma CLI. The client provides a fully typed API for reading and writing to the database.

terminal

bun run --bun --env-file=.env prisma generate

Initialize Prisma Client with the Postgres adapter

Create a new file prisma/db.ts that initializes the PrismaClient with the Postgres adapter.

prisma/db.ts

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

const adapter = new PrismaPg({ connectionString: process.env.DATABASE_URL! });
export const prisma = new PrismaClient({ adapter });

Create a test script

Write a script that creates a new user, then counts the users in the database.

index.ts

import { prisma } from "./prisma/db";

// create a new user
await prisma.user.create({
  data: {
    name: "John Dough",
    email: `john-${Math.random()}@example.com`,
  },
});

// count the number of users
const count = await prisma.user.count();
console.log(`There are ${count} users in the database.`);

Run and test the application

Run the script with bun run. Each run creates a new user.

terminal

bun run index.ts

There are 1 users in the database.

terminal

bun run index.ts

There are 2 users in the database.

terminal

bun run index.ts

There are 3 users in the database.

Prisma Postgres is now set up with Bun. Refer to the official Prisma Postgres docs as you continue to develop your application.

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Use Prisma Postgres with Bun