MongoDB

Connection URL

The MongoDB connection URL can be configured in different ways depending on how you are hosting your database. The standard configuration is made up of the following components:

mongodb://USERNAME:PASSWORD@HOST/DATABASE

mongodb://USERNAME:PASSWORD@HOST/DATABASE?ssl=true&connectTimeoutMS=5000&maxPoolSize=50

Generating ObjectId

To generate a valid ObjectId (for testing purposes or to manually set an ID field value) in your application, use the bson package.

npm install --save bson

import { ObjectId } from 'bson'

const id = new ObjectId()

No support for Prisma Migrate

Currently, there are no plans to add support for Prisma Migrate as MongoDB projects do not rely on internal schemas where changes need to be managed with an extra tool. Management of @unique indexes is realized through db push.

No support for @@id and autoincrement()

The @@id attribute (an ID for multiple fields) is not supported because primary keys in MongoDB are always on the _id field of a model.

The autoincrement() function (which creates incrementing @id values) is not supported because autoincrement() does not work with the ObjectID type that the _id field has in MongoDB.

Cyclic references and referential actions

If you have cyclic references in your models, either from self-relations or a cycle of relations between models, and you use referential actions, you must set a referential action of NoAction to prevent an infinite loop of actions.

See Special rules for referential actions for more details.

Replica set configuration

MongoDB only allows you to start a transaction on a replica set. Prisma uses transactions internally to avoid partial writes on nested queries. This means we inherit the requirement of needing a replica set configured.

When you try to use Prisma's MongoDB connector on a deployment that has no replica set configured, Prisma shows the message Error: Transactions are not supported by this deployment. The full text of the error message is the following:

PrismaClientUnknownRequestError2 [PrismaClientUnknownRequestError]:
Invalid `prisma.post.create()` invocation in
/index.ts:9:21

   6 await prisma.$connect()
   7
   8 // Create the first post
→  9 await prisma.post.create(
  Error in connector: Database error. error code: unknown, error message: Transactions are not supported by this deployment
    at cb (/node_modules/@prisma/client/runtime/index.js:34804:17)
    at processTicksAndRejections (internal/process/task_queues.js:97:5) {
  clientVersion: '3.xx.0'
}

To resolve this, we suggest you change your deployment to one with a replica set configured.

One simple way for this is to use MongoDB Atlas to launch a free instance that has replica set support out of the box.

There's also an option to run the replica set locally with this guide: https://docs.mongodb.com/manual/tutorial/convert-standalone-to-replica-set

Mapping from Prisma to MongoDB types on migration

The MongoDB connector maps the scalar types from the Prisma data model to MongoDB's native column types as follows:

MongoDB types that are currently unsupported:

• Decimal128
• Undefined
• DBPointer
• Null
• Symbol
• MinKey
• MaxKey
• Object
• Javascript
• JavascriptWithScope
• Regex

Mapping from MongoDB to Prisma types on Introspection

When introspecting a MongoDB database, Prisma uses the relevant scalar types. Some special types also get additional native type annotations:

Introspection adds native database types that are not yet supported as Unsupported fields:

schema.prisma
1model Example {
2  id    String                           @id @default(auto()) @map("_id") @db.ObjectId
3  name  String
4  regex Unsupported("RegularExpression")
5}