Introspection

Prisma ORM introspects a MongoDB schema by sampling the data stored in the given database and inferring the schema of that data.

For the purposes of illustrating introspection, this guide will help you setup a MongoDB from scratch. But if you have a MongoDB database already, feel free to jump to Initializing Prisma ORM in your project.

Setting up your Database

To see this in action, first create a blog database with 2 collections: User and Post. We recommend MongoDB Compass for setting this up:

First, add a user to our User collection:

Next, add some posts to our Post collection. It's important that the ObjectID in userId matches the user you created above.

Initializing Prisma ORM

Now that you have a MongoDB database, the next step is to create a new project and initialize Prisma ORM:

mkdir blog
cd blog
npm init -y
npm install -D prisma
npx prisma init --datasource-provider mongodb --output ../generated/prisma

Initializing Prisma ORM will create a prisma/schema.prisma file. Edit this file to use MongoDB:

prisma/schema.prisma

datasource db {
  provider = "mongodb"
  url      = env("DATABASE_URL")
}

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

Next you'll need to adjust your .env file to point the DATABASE_URL to your MongoDB database

Introspecting MongoDB with Prisma ORM

You're now ready to introspect. Run the following command to introspect your database:

npx prisma db pull

This command introspects our database and writes the inferred schema into your prisma/schema.prisma file:

prisma/schema.prisma

datasource db {
  provider = "mongodb"
  url      = env("DATABASE_URL")
}

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

model Post {
  id     String @id @default(auto()) @map("_id") @db.ObjectId
  title  String
  userId String @db.ObjectId
}

model User {
  id    String @id @default(auto()) @map("_id") @db.ObjectId
  email String
}

Tweaking the Schema

To be able to join data using Prisma Client, you can add the @relation attributes to our models:

prisma/schema.prisma

datasource db {
  provider = "mongodb"
  url      = env("DATABASE_URL")
}

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

model Post {
  id     String @id @default(auto()) @map("_id") @db.ObjectId
  title  String
  userId String @db.ObjectId
  user   User   @relation(fields: [userId], references: [id])
}

model User {
  id    String @id @default(auto()) @map("_id") @db.ObjectId
  email String
  posts Post[]
}

tip

We're actively working on MongoDB introspection. Provide feedback for this feature in this issue.

And with that, you're ready to generate Prisma Client.