prisma-database-setup-mongodb

MongoDB Setup

⚠️ WARNING: MongoDB is NOT supported in Prisma ORM v7.

Support for MongoDB is planned for a future v7 release. If you need MongoDB, you must use Prisma ORM v6.

Prerequisites

• MongoDB 4.2+
• Replica Set configured (required for transactions)
• Prisma ORM v6.x

1. Schema Configuration (v6)

In prisma/schema.prisma:

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

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

ID Field Requirement

MongoDB models must have a mapped _id field using @id and @map("_id"), usually of type String with auto() and db.ObjectId.

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

Relations

Relations in MongoDB expect IDs to be db.ObjectId type.

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

2. Environment Variable

In .env:

DATABASE_URL="mongodb+srv://user:password@cluster.mongodb.net/mydb?retryWrites=true&w=majority"

Migrations vs Introspection

• No Migrations: MongoDB is schema-less. prisma migrate commands do not work.
• db push: Use prisma db push to sync indexes and constraints.
• db pull: Use prisma db pull to generate schema from existing data (sampling).

Common Issues

"Transactions not supported"

Ensure your MongoDB instance is a Replica Set. Standalone instances do not support transactions. Atlas clusters are replica sets by default.

"Invalid ObjectID"

Ensure fields referencing IDs are decorated with @db.ObjectId if the target is an ObjectID.