Migrate from Sequelize
This guide describes how to migrate from Sequelize to Prisma. It uses an extended version of the Sequelize Express example as a sample project to demonstrate the migration steps. You can find the example used for this guide on GitHub.
This migration guide uses PostgreSQL as the example database, but it equally applies to any other relational database that's supported by Prisma.
You can learn how Prisma compares to Sequelize on the Prisma vs Sequelize page.
Overview of the migration process
Note that the steps for migrating from Sequelize to Prisma are always the same, no matter what kind of application or API layer you're building:
- Install the Prisma CLI
- Introspect your database
- Create a baseline migration
- Install Prisma Client
- Gradually replace your Sequelize queries with Prisma Client
These steps apply, no matter if you're building a REST API (e.g. with Express, koa or NestJS), a GraphQL API (e.g. with Apollo Server, TypeGraphQL or Nexus) or any other kind of application that uses Sequelize for database access.
Prisma lends itself really well for incremental adoption. This means, you don't have migrate your entire project from Sequelize to Prisma at once, but rather you can step-by-step move your database queries from Sequelize to Prisma.
Overview of the sample project
For this guide, we'll use a REST API built with Express as a sample project to migrate to Prisma. It has four models/entities:
module.exports = (sequelize, DataTypes) => {const User = sequelize.define('User', {name: {type: DataTypes.STRING,},email: {type: DataTypes.STRING,unique: true,allowNull: false,},})User.associate = (models) => {User.hasMany(models.Post, {foreignKey: 'authorId',as: 'posts',})User.hasOne(models.Profile, {onDelete: 'CASCADE',foreignKey: 'userId',})}return User}
The models have the following relations:
- 1-1:
User
↔Profile
- 1-n:
User
↔Post
- m-n:
Post
↔Category
The corresponding tables have been created using a generated Sequelize migration.
In this guide, the route handlers are located in the src/controllers
directory. The models are located in the src/models
directory. From there, they are pulled into a central src/routes.js
file which is used to set up the required routes in src/index.js
:
└── blog-sequelize├── package.json└──src├── controllers│ ├── post.js│ └── user.js├── models│ ├── Category.js│ ├── Post.js│ ├── Profile.js│ └── User.js├── index.js└── routes.js
Step 1. Install the Prisma CLI
The first step to adopt Prisma is to install the Prisma CLI in your project:
$
Step 2. Introspect your database
2.1. Set up Prisma
Before you can introspect your database, you need to set up your Prisma schema and connect Prisma to your database. Run the following command in your terminal to create a basic Prisma schema file:
$
This command created a new directory called prisma
with the following files for you:
schema.prisma
: Your Prisma schema file that specifies your database connection and models.env
: Adotenv
to configure your database connection URL as an environment variable
The Prisma schema file currently looks as follows:
prisma/schema.prisma
1// This is your Prisma schema file,2// learn more about it in the docs: https://pris.ly/d/prisma-schema34datasource db {5 provider = "postgresql"6 url = env("DATABASE_URL")7}89generator client {10 provider = "prisma-client-js"11}
If you're using VS Code, be sure to install the Prisma VS Code extension for syntax highlighting, formatting, auto-completion and a lot more cool features.
2.2. Connect your database
If you're not using PostgreSQL, you need to adjust the provider
field on the datasource
block to the database you currently use:
datasource db {provider = "postgresql"url = env("DATABASE_URL")}
Once that's done, you can configure your database connection URL in the .env
file. Here's how the database connection from Sequelize maps to the connection URL format used by Prisma:
Assume you have the following database connection details in src/models/index.js
:
src/models/index.js
1const sequelize = new Sequelize('blog-sequelize', 'alice', 'myPassword42', {2 host: 'localhost',3 dialect: 'postgres',4})
The respective connection URL would look as follows in Prisma:
.env
1DATABASE_URL="postgresql://alice:myPassword42@localhost:5432/blog-sequelize"
Note that you can optionally configure the PostgreSQL schema by appending the schema
argument to the connection URL:
.env
1DATABASE_URL="postgresql://alice:myPassword42@localhost:5432/blog-sequelize?schema=myschema"
If not provided, the default schema called public
is being used.
2.3. Introspect your database using Prisma
With your connection URL in place, you can introspect your database to generate your Prisma models:
$
This creates the following Prisma models:
prisma/schema.prisma
1model Categories {2 id Int @id @default(autoincrement())3 name String4 createdAt DateTime5 updatedAt DateTime6 PostCategories PostCategories[]7}89model PostCategories {10 createdAt DateTime11 updatedAt DateTime12 CategoryId Int13 PostId Int14 Categories Categories @relation(fields: [CategoryId], references: [id])15 Posts Posts @relation(fields: [PostId], references: [id])1617 @@id([CategoryId, PostId])18}1920model Posts {21 id Int @id @default(autoincrement())22 title String23 content String?24 published Boolean? @default(false)25 createdAt DateTime26 updatedAt DateTime27 authorId Int?28 Users Users? @relation(fields: [authorId], references: [id])29 PostCategories PostCategories[]30}3132model Profiles {33 id Int @id @default(autoincrement())34 bio String35 createdAt DateTime36 updatedAt DateTime37 userId Int? @unique38 Users Users? @relation(fields: [userId], references: [id])39}4041model SequelizeMeta {42 name String @id43}4445model Users {46 id Int @id @default(autoincrement())47 name String?48 email String @unique49 createdAt DateTime50 updatedAt DateTime51 Posts Posts[]52 Profiles Profiles?53}
2.4. Create a baseline migration
To continue using Prisma Migrate to evolve your database schema, you will need to baseline your database.
First, create a migrations
directory and add a directory inside with your preferred name for the migration. In this example, we will use 0_init
as the migration name:
$mkdir -p prisma/migrations/0_init
Next, generate the migration file with prisma migrate diff
. Use the following arguments:
--from-empty
: assumes the data model you're migrating from is empty--to-schema-datamodel
: the current database state using the URL in thedatasource
block--script
: output a SQL script
$npx prisma migrate diff --from-empty --to-schema-datamodel prisma/schema.prisma --script > prisma/migrations/0_init/migration.sql
Review the generated migration to ensure everything is correct.
Next, mark the migration as applied using prisma migrate resolve
with the --applied
argument.
$npx prisma migrate resolve --applied 0_init
The command will mark 0_init
as applied by adding it to the _prisma_migrations
table.
You now have a baseline for your current database schema. To make further changes to your database schema, you can update your Prisma schema and use prisma migrate dev
to apply the changes to your database.
2.5. Adjust createdAt
and updatedAt
fields
The generated Prisma models represent your database tables and are the foundation for your programmatic Prisma Client API which allows you to send queries to your database.
You'll adjust the createdAt
and updatedAt
fields in our models. Sequelize doesn't add the DEFAULT
constraint to createdAt
when creating the tables in the database.
Therefore, you'll add @default(now())
and @updatedAt
attributes to the createdAt
and updatedAt
columns respectively.
To learn more how Prisma does this, you can read more @default(now())
and @updatedAt
here.
Our updated schema will be as follows:
prisma/schema.prisma
1model Categories {2 id Int @id @default(autoincrement())3 name String4 createdAt DateTime @default(now())5 updatedAt DateTime @updatedAt6 PostCategories PostCategories[]7}89model PostCategories {10 createdAt DateTime @default(now())11 updatedAt DateTime @updatedAt12 CategoryId Int13 PostId Int14 Categories Categories @relation(fields: [CategoryId], references: [id])15 Posts Posts @relation(fields: [PostId], references: [id])1617 @@id([CategoryId, PostId])18}1920model Posts {21 id Int @id @default(autoincrement())22 title String23 content String?24 published Boolean? @default(false)25 createdAt DateTime @default(now())26 updatedAt DateTime @updatedAt27 authorId Int?28 Users Users? @relation(fields: [authorId], references: [id])29 PostCategories PostCategories[]30}3132model Profiles {33 id Int @id @default(autoincrement())34 bio String35 createdAt DateTime @default(now())36 updatedAt DateTime @updatedAt37 userId Int? @unique38 Users Users? @relation(fields: [userId], references: [id])39}4041model SequelizeMeta {42 name String @id43}4445model Users {46 id Int @id @default(autoincrement())47 name String?48 email String @unique49 createdAt DateTime @default(now())50 updatedAt DateTime @updatedAt51 Posts Posts[]52 Profiles Profiles?53}
2.6. Adjust the Prisma schema (optional)
The models that were generated via introspection currently exactly map to your database tables. In this section, you'll learn how you can adjust the naming of the Prisma models to adhere to Prisma's naming conventions.
All of these adjustment are entirely optional and you are free to skip to the next step already if you don't want to adjust anything for now. You can go back and make the adjustments at any later point.
As opposed to the current snake_case notation of Prisma models, Prisma's naming conventions are:
- PascalCase for model names
- camelCase for field names
You can adjust the naming by mapping the Prisma model and field names to the existing table and column names in the underlying database using @@map
and @map
.
Also note that you can rename relation fields to optimize the Prisma Client API that you'll use later to send queries to your database. For example, the post
field on the user
model is a list, so a better name for this field would be posts
to indicate that it's plural.
Sequelize generates a SequelizeMeta
model that is used internally by the library that is not needed. Therefore, you'll manually delete it from the schema.
Here's an adjusted version of the Prisma schema that addresses these points:
prisma/schema.prisma
1generator client {2 provider = "prisma-client-js"3}45datasource db {6 provider = "postgresql"7 url = env("DATABASE_URL")8}910model Category {11 id Int @id @default(autoincrement())12 name String13 createdAt DateTime @default(now())14 updatedAt DateTime @updatedAt15 postCategories PostToCategories[]1617 @@map("Categories")18}1920model PostToCategories {21 createdAt DateTime @default(now())22 updatedAt DateTime @updatedAt23 categoryId Int24 postId Int25 category Category @relation(fields: [categoryId], references: [id])26 post Post @relation(fields: [postId], references: [id])2728 @@id([categoryId, postId])29 @@map("PostCategories")30}3132model Post {33 id Int @id @default(autoincrement())34 title String35 content String?36 published Boolean? @default(false)37 createdAt DateTime @default(now())38 updatedAt DateTime @updatedAt39 authorId Int?40 author User? @relation(fields: [authorId], references: [id])41 postToCategories PostToCategories[]4243 @@map("Posts")44}4546model Profile {47 id Int @id @default(autoincrement())48 bio String49 createdAt DateTime @default(now())50 updatedAt DateTime @updatedAt51 userId Int? @unique52 user User? @relation(fields: [userId], references: [id])5354 @@map("Profiles")55}5657model User {58 id Int @id @default(autoincrement())59 name String?60 email String @unique61 createdAt DateTime @default(now())62 updatedAt DateTime @updatedAt63 posts Post[]64 profile Profile?6566 @@map("Users")67}
Step 3. Install Prisma Client
As a next step, you can install Prisma Client in your project so that you can start replacing the database queries in your project that are currently made with Sequelize:
$npm install @prisma/client
Step 4. Replace your Sequelize queries with Prisma Client
In this section, we'll show a few sample queries that are being migrated from Sequelize to Prisma Client based on the example routes from the sample REST API project. For a comprehensive overview of how the Prisma Client API differs from Sequelize, check out the API comparison page.
First, to set up the PrismaClient
instance that you'll use to send database queries from the various route handlers. Create a new file named prisma.js
in the src
directory:
$
Now, instantiate PrismaClient
and export it from the file so you can use it in your route handlers later:
src/prisma.js
12345
The imports in our controller files are as follows:
src/controllers/post.js
1const { Post, User, Category } = require('../models')2const { Op } = require('sequelize')
src/controllers/user.js
1const { User } = require('../models')
You'll update the controller imports as you migrate from Sequelize to Prisma:
src/controllers/post.js
1const prisma = require('../prisma')
src/controllers/user.js
1const prisma = require('../prisma')
4.1. Replacing queries in GET
requests
The REST API has four routes that accept GET
requests:
/feed
: Return all published posts/filterPosts?searchString=SEARCH_STRING
: Filter returned posts bySEARCH_STRING
/post/:postId
: Returns a specific post/authors
: Returns a list of authors
Let's dive into the route handlers that implement these requests.
/feed
The /feed
handler is currently implemented as follows:
src/controllers/post.js
1const feed = async (req, res) => {2 try {3 const feed = await Post.findAll({4 where: { published: true },5 include: ['author', 'categories'],6 })7 return res.json(feed)8 } catch (error) {9 return res.status(500).json(error)10 }11}
Note that each returned Post
object includes the relation to the author
and category
it's associated with. With Sequelize, including the relation is not type-safe. For example, if there was a typo in the relation that is retrieved, your database query would fail only at runtime – the JavaScript compiler does not provide any safety here.
Here is how the same route is implemented using Prisma Client:
src/controllers/post.js
1const feed = async (req, res) => {2 try {3 const feed = await prisma.post.findMany({4 where: { published: true },5 include: { author: true, postToCategories: true },6 })7 return res.json(feed)8 } catch (error) {9 return res.status(500).json(error)10 }11}
Note that the way how Prisma Client includes the author
relation is absolutely type-safe. The JavaScript compiler would throw an error if you were trying to include a relation that does not exist on the Post
model.
/filterPosts?searchString=SEARCH_STRING
The /filterPosts
handler is currently implemented as follows:
src/controllers/post.js
1const filterPosts = async (req, res) => {2 const { searchString } = req.query34 try {5 const filteredPosts = await Post.findAll({6 where: {7 [Op.or]: [8 {9 title: {10 [Op.like]: `%${searchString}%`,11 },12 },13 {14 content: {15 [Op.like]: `%${searchString}%`,16 },17 },18 ],19 },20 include: 'author',21 })2223 res.json(filteredPosts)24 } catch (error) {25 return res.status(500).json(error)26 }27}
With Prisma, the route is implemented as follows:
src/controllers/post.js
1const filterPosts = async (req, res) => {2 const { searchString } = req.query34 try {5 const filteredPosts = prisma.post.findMany({6 where: {7 OR: [8 {9 title: { contains: searchString },10 },11 {12 content: { contains: searchString },13 },14 ],15 },16 })1718 res.json(filteredPosts)19 } catch (error) {20 return res.status(500).json(error)21 }22}
Note that Sequelize provides Operator symbols - Op
- to be used when querying data. Prisma on the other hand combines several where
conditions with an implicit AND
operator, so in this case the Prisma query needs to make the OR
explicit.
/post/:postId
The /post/:postId
handler is currently implemented as follows:
src/controllers/post.js
1const getPostById = async (req, res) => {2 const { postId } = req.params34 try {5 const post = await Post.findOne({6 where: { id: postId },7 include: 'author',8 })910 return res.json(post)11 } catch (error) {12 return res.status(500).json(error)13 }14}
With Prisma, the route is implemented as follows:
src/controllers/post.js
1const getPostById = async (req, res) => {2 const { postId } = req.params34 try {5 const post = await prisma.post.findUnique({6 where: { id: Number(postId) },7 include: { author: true },8 })910 return res.json(post)11 } catch (error) {12 return res.status(500).json(error)13 }14}
4.2. Replacing queries in POST
requests
The REST API has three routes that accept POST
requests:
/user
: Creates a newUser
record/post
: Creates a newUser
record/user/:userId/profile
: Creates a newProfile
record for aUser
record with a given ID
/user
The /user
handler is currently implemented as follows:
src/controllers/user.js
1const createUser = async (req, res) => {2 const { name, email } = req.body34 try {5 const user = await User.create({6 name,7 email,8 })910 return res.json(user)11 } catch (error) {12 return res.status(500).json(error)13 }14}
With Prisma, the route is implemented as follows:
src/controllers/user.js
1const createUser = async (req, res) => {2 const { name, email } = req.body34 try {5 const user = await prisma.user.create({6 data: {7 name,8 email,9 },10 })1112 return res.json(user)13 } catch (error) {14 return res.status(500).json(error)15 }16}
/post
The /post
handler is currently implemented as follows:
src/controllers/post.js
1const createDraft = async (req, res) => {2 const { title, content, authorEmail } = req.body34 try {5 const user = await User.findOne({ email: authorEmail })67 const draft = await Post.create({8 title,9 content,10 authorId: user.id,11 })1213 res.json(draft)14 } catch (error) {15 return res.status(500).json(error)16 }17}
With Prisma, the route is implemented as follows:
src/controllers/post.js
1const createDraft = async (req, res) => {2 const { title, content, authorEmail } = req.body34 try {5 const draft = await prisma.post.create({6 data: {7 title,8 content,9 author: {10 connect: { email: authorEmail },11 },12 },13 })1415 res.json(draft)16 } catch (error) {17 return res.status(500).json(error)18 }19}
Note that Prisma Client's nested write here save an initial query where first the User
record needs to be retrieved by its email
. That's because, with Prisma you can connect records in relations using any unique property.
/user/:userId/profile
The /user/:userId/profile
handler is currently implemented as follows:
src/controllers/user.js
1const setUserBio = async (req, res) => {2 const { userId } = req.params3 const { bio } = req.body45 try {6 const user = await User.findOne({7 where: {8 id: Number(userId),9 },10 })1112 const updatedUser = await user.createProfile({ bio })1314 return res.json(updatedUser)15 } catch (error) {16 return res.status(500).json(error)17 }18}
With Prisma, the route is implemented as follows:
src/controllers/user.js
1const setUserBio = async (req, res) => {2 const { userId } = req.params3 const { bio } = req.body45 try {6 const user = await prisma.user.update({7 where: { id: Number(userId) },8 data: {9 profile: {10 create: { bio },11 },12 },13 })1415 return res.json(user)16 } catch (error) {17 return res.status(500).json(error)18 }19}
4.3. Replacing queries in PUT
requests
The REST API has one route that accept a PUT
request:
/addPostToCategory?postId=POST_ID&categoryId=CATEGORY_ID
: Adds the post withPOST_ID
to the category withCATEGORY_ID
Let's dive into the route handlers that implement these requests.
/addPostToCategory?postId=POST_ID&categoryId=CATEGORY_ID
The /addPostToCategory?postId=POST_ID&categoryId=CATEGORY_ID
handler is currently implemented as follows:
src/controllers/post.js
1const addPostToCategory = async (req, res) => {2 const { postId, categoryId } = req.query34 try {5 const post = await Post.findOne({6 where: { id: postId },7 })89 const category = await Category.findOne({10 where: { id: categoryId },11 })1213 const updatedPost = await post.addCategory(category)1415 return res.json(updatedPost)16 } catch (error) {17 return res.status(500).json(error)18 }19}
With Prisma, the route is implemented as follows:
src/controllers/post.js
1const addPostToCategory = async (req, res) => {2 const { postId, categoryId } = req.query34 try {5 const post = await prisma.post.update({6 data: {7 postToCategories: {8 create: {9 categories: {10 connect: { id: Number(categoryId) },11 },12 },13 },14 },15 where: {16 id: Number(postId),17 },18 })1920 return res.json(post)21 } catch (error) {22 return res.status(500).json(error)23 }24}
Note that this Prisma Client can be made less verbose by modeling the relation as an implicit many-to-many relation instead. In that case, the query would look as follows:
src/controllers/posts.js
1const post = await prisma.post.update({2 data: {3 category: {4 connect: { id: categoryId },5 },6 },7 where: { id: postId },8})
More
Primary key column
By default, Sequelize defines a primaryKey
and used id
with the autoby default if not defined. This is optional.
If you would like to set your own primary key, you can use the primaryKey: true
and define your preferred data type in your field of choice:
// changing the primary key columnmodule.exports = (sequelize, DataTypes) => {const Post = sequelize.define('Post', {postId: {type: DataTypes.INTEGER,primaryKey: true,},})return Post}// changing the id DataTypemodule.exports = (sequelize, DataTypes) => {const Post = sequelize.define('Post', {id: {type: DataTypes.UUID, // alternative: DataTypes.STRINGprimaryKey: true,},})return Post}
Table name inference
Sequelize infers table names from the model name. When the name of a table isn't provided Sequelize automatically pluralizes the model name and uses that as the table name using a library called inflection. Prisma on the other hand maps the model name to the table name in your database modelling your data. If you wish to change this default behaviour in Sequelize, you can either enforce the table name to be equal to the model name or provide the table name directly:
// enforcing table name to be equal to model namemodule.exports = (sequelize, DataTypes) => {const Post = sequelize.define('Post',{// ... attributes},{freezeTableName: true,})return Post}
// providing the table name directlymodule.exports = (sequelize, DataTypes) => {const Post = sequelize.define('Post',{// ... attributes},{tableName: 'Post',})return Post}
Timestamps
Sequelize automatically adds the fields createdAt
and updatedAt
to every model using the data type DataTypes.DATE
, by default. You can disable this for a model with the timestamps: false
option:
sequelize.define('User',{// ... (attributes)},{timestamps: false,})
Prisma offers you the flexibility to define these fields in your model. You add the createdAt
and updatedAt
fields by defining them explicitly in your model.
To set the createdAt
field in your model, add the default(now())
attribute to the column. In order to set the updatedAt
column, update your model by adding the @updatedAt
attribute to the column.
model User {id Int @id @default(autoincrement())name String?email String @uniquecreatedAt DateTime @default(now())updatedAt DateTime @updatedAt}
Implicit many-to-many relations
Similar to the belongsToMany()
association method in Sequelize, Prisma allows you to model many-to-many relations implicitly. That is, a many-to-many relation where you do not have to manage the relation table (also sometimes called JOIN table) explicitly in your schema. Here is an example with Sequelize:
module.exports = (sequelize, DataTypes) => {const Post = sequelize.define('Post', {title: {type: DataTypes.STRING,allowNull: false,},content: {type: DataTypes.STRING,},published: {type: DataTypes.BOOLEAN,defaultValue: false,},})Post.associate = (models) => {Post.belongsTo(models.User, {foreignKey: 'authorId',as: 'author',})Post.belongsToMany(models.Category, {through: 'PostCategories',as: 'categories',})}return Post}
module.exports = (sequelize, DataTypes) => {const Category = sequelize.define('Category', {name: {type: DataTypes.STRING,allowNull: false,},})Category.associate = (models) => {Category.belongsToMany(models.Post, {through: 'PostCategories',as: 'posts',})}return Category}
When you start your application, Sequelize will create the the tables for you - based on these models:
Executing (default): CREATE TABLE IF NOT EXISTS "PostCategories"("createdAt" TIMESTAMP WITH TIME ZONE NOT NULL, "updatedAt" TIMESTAMP WITH TIME ZONE NOT NULL,"CategoryId" INTEGER REFERENCES "Categories" ("id") ON DELETE CASCADE ON UPDATE CASCADE,"PostId" INTEGER REFERENCES "Posts" ("id") ON DELETE CASCADE ON UPDATE CASCADE, PRIMARY KEY ("CategoryId","PostId"));
If you introspect the database with Prisma, you'll get the following result in the Prisma schema (note that some relation field names have been adjusted to look friendlier compared to the raw version from introspection):
model Categories {id Int @id @default(autoincrement())name StringcreatedAt DateTimeupdatedAt DateTimePostCategories PostCategories[]@@map("category")}model PostCategories {createdAt DateTimeupdatedAt DateTimeCategoryId IntPostId IntCategories Categories @relation(fields: [CategoryId], references: [id])Posts Posts @relation(fields: [PostId], references: [id])@@id([CategoryId, PostId])@@map("PostCategories")}model Posts {id Int @id @default(autoincrement())title Stringcontent String?published Boolean? @default(false)createdAt DateTimeupdatedAt DateTimeauthorId Int?Users Users? @relation(fields: [authorId], references: [id])PostCategories PostCategories[]@@map("post")}
In this Prisma schema, the many-to-many relation is modeled explicitly via the relation table PostCategories
By adhering to the conventions for Prisma relation tables, the relation could look as follows:
model Categories {id Int @id @default(autoincrement())name Stringposts Posts[]@@map("category")}model Posts {id Int @id @default(autoincrement())title Stringcontent String?published Boolean @default(false)authorId Int?author User? @relation(fields: [authorId], references: [id])categories Categories[]@@map("post")}
This would also result in a more ergonomic and less verbose Prisma Client API to modify the records in this relation, because you have a direct path from Post
to Category
(and the other way around) instead of needing to traverse the PostCategories
model first.