Drizzle Seed - Drizzle ORM

Drizzle Seed is a TypeScript library for generating realistic, deterministic fake data to populate your database. Using a seedable pseudorandom number generator (pRNG), it produces consistent, reproducible data across runs - perfect for testing, development, and debugging.

Requires [email protected] or higher for full compatibility with identity columns and type safety.

Installation

npm install drizzle-seed

You must have drizzle-orm installed:

npm install drizzle-orm

Quick Start

Generate 10 users with random data:

import { pgTable, serial, text } from 'drizzle-orm/pg-core';
import { drizzle } from 'drizzle-orm/node-postgres';
import { seed } from 'drizzle-seed';

const users = pgTable('users', {
  id: serial('id').primaryKey(),
  name: text('name').notNull(),
  email: text('email').notNull(),
});

const db = drizzle(process.env.DATABASE_URL!);

// Seed with default count of 10
await seed(db, { users });

How It Works

Deterministic Data Generation

Drizzle Seed uses a pseudorandom number generator (pRNG) initialized with a seed value. The same seed always produces the same sequence of data:

// Same seed = same data every time
await seed(db, schema, { seed: 12345 });

Benefits:

Consistency - Tests run on identical data every time
Debugging - Reproduce bugs with the same data set
Collaboration - Team members share seed values for consistent data

Automatic Type Inference

Drizzle Seed analyzes your schema and generates appropriate data for each column type:

import { pgTable, serial, varchar, integer, timestamp, boolean } from 'drizzle-orm/pg-core';

const users = pgTable('users', {
  id: serial('id').primaryKey(),           // Sequential: 1, 2, 3...
  name: varchar('name', { length: 255 }),  // Random names: "John Doe"
  age: integer('age'),                     // Random integers
  createdAt: timestamp('created_at'),      // Random timestamps
  active: boolean('active'),               // Random booleans
});

await seed(db, { users });

Basic Usage

Specify Count

Generate a specific number of records:

// Generate 1000 users
await seed(db, { users }, { count: 1000 });

Set Seed Value

Use different seeds for different data sets:

// Development seed
await seed(db, schema, { seed: 1 });

// Testing seed
await seed(db, schema, { seed: 999 });

// Staging seed
await seed(db, schema, { seed: 12345 });

Customize data generation with the refine method:

import { pgTable, serial, text, integer, timestamp } from 'drizzle-orm/pg-core';
import { seed } from 'drizzle-seed';

const users = pgTable('users', {
  id: serial('id').primaryKey(),
  email: text('email').notNull(),
  age: integer('age'),
  role: text('role'),
  createdAt: timestamp('created_at'),
});

await seed(db, { users }).refine((funcs) => ({
  users: {
    columns: {
      email: funcs.email(),
      age: funcs.int({ minValue: 18, maxValue: 80 }),
      role: funcs.valuesFromArray({
        values: ['admin', 'user', 'moderator'],
      }),
    },
  },
}));

Generator Functions

Drizzle Seed provides extensive generator functions:

String Generators

funcs.firstName()        // "John"
funcs.lastName()         // "Doe"
funcs.fullName()         // "John Doe"
funcs.email()            // "[email protected]"

Number Generators

// Integers
funcs.int({ minValue: 1, maxValue: 100 })

// Decimals
funcs.number({
  minValue: 0.0,
  maxValue: 1.0,
  precision: 100  // Two decimal places
})

// Sequential integers (for PKs)
funcs.intPrimaryKey()  // 1, 2, 3, 4...

Date and Time Generators

// Timestamps
funcs.timestamp()

// Dates
funcs.date()

// Times
funcs.time()

// Datetime
funcs.datetime()

// Years
funcs.year()

Special Generators

// UUIDs
funcs.uuid()

// Booleans
funcs.boolean()

// Enums
funcs.enum({ enum: myEnum })

// JSON
funcs.json()

// Phone numbers
funcs.phoneNumber()

Custom Values

// Static value
funcs.default({ defaultValue: "constant" })

// Values from array
funcs.valuesFromArray({
  values: ['option1', 'option2', 'option3'],
})

// Unique values from array
funcs.valuesFromArray({
  values: ['unique1', 'unique2', 'unique3'],
  isUnique: true,
})

// Weighted values
funcs.valuesFromArray({
  values: [
    { weight: 0.7, values: ['common'] },
    { weight: 0.3, values: ['rare'] },
  ],
})

Unique Generators

Generate unique values:

funcs.uniqueEmail()
funcs.uniqueInt({ minValue: 1, maxValue: 10000 })
funcs.uniqueString({ isUnique: true })
funcs.uniqueFirstName()
funcs.uniqueLastName()

Generate data for tables with relationships:

import { pgTable, serial, text, integer } from 'drizzle-orm/pg-core';
import { relations } from 'drizzle-orm';

const users = pgTable('users', {
  id: serial('id').primaryKey(),
  name: text('name').notNull(),
});

const posts = pgTable('posts', {
  id: serial('id').primaryKey(),
  title: text('title').notNull(),
  userId: integer('user_id').notNull().references(() => users.id),
});

const usersRelations = relations(users, ({ many }) => ({
  posts: many(posts),
}));

const postsRelations = relations(posts, ({ one }) => ({
  user: one(users, {
    fields: [posts.userId],
    references: [users.id],
  }),
}));

// Seed with relationships
await seed(db, { users, posts }).refine((funcs) => ({
  users: {
    count: 10,
    with: {
      posts: 5  // Each user gets 5 posts
    },
  },
}));

Weighted Relationships

Create varied relationship counts:

await seed(db, { users, posts }).refine((funcs) => ({
  users: {
    count: 100,
    with: {
      posts: [
        { weight: 0.2, count: 0 },        // 20% have no posts
        { weight: 0.5, count: [1, 3] },   // 50% have 1-3 posts
        { weight: 0.3, count: [4, 10] },  // 30% have 4-10 posts
      ],
    },
  },
}));

Reset Database

Clear and reseed your database:

import { reset } from 'drizzle-seed';
import * as schema from './schema';

const db = drizzle(process.env.DATABASE_URL!);

// Delete all data and reseed
await reset(db, schema);

This deletes all data in the specified tables. Use with caution!

Common Patterns

E-commerce Example

import { pgTable, serial, text, integer, numeric, timestamp } from 'drizzle-orm/pg-core';

const products = pgTable('products', {
  id: serial('id').primaryKey(),
  name: text('name').notNull(),
  price: numeric('price', { precision: 10, scale: 2 }),
  stock: integer('stock'),
  createdAt: timestamp('created_at').defaultNow(),
});

const orders = pgTable('orders', {
  id: serial('id').primaryKey(),
  productId: integer('product_id').references(() => products.id),
  quantity: integer('quantity'),
  total: numeric('total', { precision: 10, scale: 2 }),
  createdAt: timestamp('created_at').defaultNow(),
});

await seed(db, { products, orders }, { count: 100 }).refine((funcs) => ({
  products: {
    columns: {
      name: funcs.loremIpsum({ sentenceCount: 2 }),
      price: funcs.number({ minValue: 9.99, maxValue: 999.99, precision: 100 }),
      stock: funcs.int({ minValue: 0, maxValue: 1000 }),
    },
    with: {
      orders: [1, 5],  // Each product has 1-5 orders
    },
  },
  orders: {
    columns: {
      quantity: funcs.int({ minValue: 1, maxValue: 10 }),
    },
  },
}));

Blog Platform Example

import { pgTable, serial, text, timestamp, boolean } from 'drizzle-orm/pg-core';

const users = pgTable('users', {
  id: serial('id').primaryKey(),
  email: text('email').notNull().unique(),
  name: text('name').notNull(),
  bio: text('bio'),
});

const posts = pgTable('posts', {
  id: serial('id').primaryKey(),
  title: text('title').notNull(),
  content: text('content').notNull(),
  published: boolean('published').default(false),
  authorId: integer('author_id').references(() => users.id),
  createdAt: timestamp('created_at').defaultNow(),
});

const comments = pgTable('comments', {
  id: serial('id').primaryKey(),
  content: text('content').notNull(),
  postId: integer('post_id').references(() => posts.id),
  userId: integer('user_id').references(() => users.id),
  createdAt: timestamp('created_at').defaultNow(),
});

await seed(db, { users, posts, comments }, { seed: 1 }).refine((funcs) => ({
  users: {
    count: 50,
    columns: {
      email: funcs.email(),
      name: funcs.fullName(),
      bio: funcs.loremIpsum({ sentenceCount: 3 }),
    },
    with: {
      posts: [0, 10],  // Users have 0-10 posts
    },
  },
  posts: {
    columns: {
      title: funcs.loremIpsum({ sentenceCount: 1 }),
      content: funcs.loremIpsum({ sentenceCount: 20 }),
      published: funcs.boolean(),
    },
    with: {
      comments: [0, 25],  // Posts have 0-25 comments
    },
  },
  comments: {
    columns: {
      content: funcs.loremIpsum({ sentenceCount: 2 }),
    },
  },
}));

Testing Patterns

Test Setup

import { beforeEach, test } from 'vitest';
import { seed, reset } from 'drizzle-seed';
import * as schema from './schema';

beforeEach(async () => {
  // Reset database before each test
  await reset(db, schema);
  
  // Seed with consistent data
  await seed(db, schema, { seed: 1, count: 10 });
});

test('user creation', async () => {
  // Your test with seeded data
  const users = await db.select().from(schema.users);
  expect(users).toHaveLength(10);
});

Multiple Scenarios

const scenarios = {
  empty: { seed: 1, count: 0 },
  small: { seed: 2, count: 10 },
  medium: { seed: 3, count: 100 },
  large: { seed: 4, count: 1000 },
};

test('handles empty database', async () => {
  await reset(db, schema);
  await seed(db, schema, scenarios.empty);
  // Test with empty database
});

test('handles large dataset', async () => {
  await reset(db, schema);
  await seed(db, schema, scenarios.large);
  // Test with 1000 records
});

Performance Tips

Use appropriate counts

Start with small counts during development:

await seed(db, schema, { count: 10 });

Batch operations

Drizzle Seed automatically batches inserts for better performance.

Disable constraints for large seeds

For very large datasets, consider temporarily disabling foreign key constraints:

-- PostgreSQL
SET session_replication_role = 'replica';
-- Run seed
SET session_replication_role = 'origin';

Best Practices

Consistent Seeds

Use the same seed value for tests to ensure reproducible results

Realistic Data

Use appropriate generators to create data that resembles production

Relationship Balance

Use weighted relationships to simulate realistic data distribution

Clean State

Reset database between test runs for isolation

Next Steps

Schema Validation

Validate seeded data with Zod, Valibot, or TypeBox

Testing Guide

Learn testing patterns with Drizzle ORM

Get Started

Core Concepts

Database Drivers

Query Builders

Schema Definition

Advanced Features

Ecosystem

Guides

​Installation

​Quick Start

​How It Works

​Deterministic Data Generation

​Automatic Type Inference

​Basic Usage

​Specify Count

​Set Seed Value

​Advanced Usage with Refinements

​Generator Functions

​String Generators

​Number Generators

​Date and Time Generators

​Special Generators

​Custom Values

​Unique Generators

​Seeding Related Data

​Weighted Relationships

​Reset Database

​Common Patterns

​E-commerce Example

​Blog Platform Example

​Testing Patterns

​Test Setup

​Multiple Scenarios

​Performance Tips

​Best Practices

Consistent Seeds

Realistic Data

Relationship Balance

Clean State

​Next Steps

Schema Validation

Testing Guide

Build docs developers (and LLMs) love

Installation

Quick Start

How It Works

Deterministic Data Generation

Automatic Type Inference

Basic Usage

Specify Count

Set Seed Value

Advanced Usage with Refinements

Generator Functions

String Generators

Number Generators

Date and Time Generators

Special Generators

Custom Values

Unique Generators

Seeding Related Data

Weighted Relationships

Reset Database

Common Patterns

E-commerce Example

Blog Platform Example

Testing Patterns

Test Setup

Multiple Scenarios

Performance Tips

Best Practices

Next Steps