queryInterface.bulkInsert vs. Model.bulkCreate

Welcome to this tutorial on comparing queryInterface.bulkInsert and Model.bulkCreate in Sequelize. Imagine you are a gardener tasked with planting a field of seeds. You have two methods: one where you manually place each seed (queryInterface.bulkInsert) and another where you use a high-tech planter machine (Model.bulkCreate) that automatically checks the quality of each seed before planting. In this lesson, we’ll explore both approaches, discuss their limitations, and learn why the advanced planter (Model.bulkCreate) is often the preferred method.

Using queryInterface.bulkInsert

queryInterface.bulkInsert is a method provided by Sequelize’s queryInterface to insert multiple records into a table. It is generated in seeder files when you run the command:

npx sequelize seed:generate --name <name_of_seeder_file>

This creates a seeder file with an up function (to insert data) and a down function (to remove the data).

However, using bulkInsert has a couple of limitations:

Timestamps: It does not automatically set createdAt and updatedAt fields. You must manually include these values; otherwise, if your table requires them, the insertion will throw an error.
Validations: It does not run model-level validations. Even if your model defines strict rules, bulkInsert will not check these rules, potentially allowing invalid data.

For instance, consider this example. Without timestamps:

await queryInterface.bulkInsert('People', [
  {
    name: 'John Doe',
    isBetaMember: false
  }
], {});

This might throw an error if your table has timestamp columns. But if you add timestamps:

await queryInterface.bulkInsert('People', [
  {
    name: 'John Doe',
    isBetaMember: false,
    createdAt: new Date(),
    updatedAt: new Date()
  }
], {});

Also, if your model validates that isBetaMember must be a boolean, using bulkInsert won’t enforce that, meaning this code would run without errors:

await queryInterface.bulkInsert('People', [
  {
    name: 'John Doe',
    isBetaMember: "yes", // Incorrect type, but no validation occurs here.
    createdAt: new Date(),
    updatedAt: new Date()
  }
], {});

In summary, while bulkInsert is useful and straightforward, its manual nature can lead to oversights.

Using Model.bulkCreate

To overcome these limitations, the recommended approach is to use Model.bulkCreate. This is like using a high-tech planter machine that not only plants your seeds but also checks each seed for quality and automatically sets the correct timing values.

With Model.bulkCreate, you first import your model into your seeder file, and then call the method on the model. For example:

// Import the model
const { Person } = require('../db/models');

// Use Model.bulkCreate to insert data with validations
await Person.bulkCreate([
  {
    name: 'John Doe',
    isBetaMember: false
  }
], { validate: true });

With validate: true set in the options, Sequelize will run all the model-level validations defined in your model. This means that if you try to insert an invalid value (for instance, a string instead of a boolean for isBetaMember), an error will be thrown, ensuring data integrity.

Compare this with the previous approach: using bulkInsert allowed invalid data to slip through, whereas Model.bulkCreate enforces the rules you defined in your model, much like a quality-control system.

Code Comparison Example

Let’s see side-by-side examples to highlight the differences.

Using queryInterface.bulkInsert:

await queryInterface.bulkInsert('People', [
  {
    name: 'John Doe',
    isBetaMember: false,
    createdAt: new Date(),
    updatedAt: new Date()
  }
], {});

Using Model.bulkCreate:

const { Person } = require('../db/models');

await Person.bulkCreate([
  {
    name: 'John Doe',
    isBetaMember: false
  }
], { validate: true });

Notice that with Model.bulkCreate you don’t need to manually add the timestamps (if your model is configured to handle them), and validations will be applied automatically.

Summary and Recommendations

The App Academy recommends using Model.bulkCreate for inserting seed data in your projects. This method helps ensure that:

Timestamps are managed automatically
Model-level validations run, preserving data integrity
Your code is cleaner and easier to maintain

However, if for some reason you choose to use queryInterface.bulkInsert, be aware of its limitations, and make sure to manually handle timestamps and validations.

In practice, think of Model.bulkCreate as a smart assistant who not only plants your seeds but also checks each one to make sure they’re perfect. It’s a best practice that leads to more reliable and maintainable code.

Additional Topics to Explore

As you work more with Sequelize seeders, consider exploring:

How to structure seeder files for complex data relationships.
Strategies for re-running and undoing seed data.
The differences in behavior between queryInterface.bulkInsert and Model.bulkCreate across different SQL dialects.

Conclusion

In this tutorial, we compared two methods for inserting seed data in Sequelize: queryInterface.bulkInsert and Model.bulkCreate. While bulkInsert is straightforward, it requires manual management of timestamps and does not enforce model validations. Model.bulkCreate, on the other hand, automatically handles timestamps and runs all defined validations, making it the preferred method for maintaining data integrity.

By choosing the right method for seeding your data, you ensure that your database is populated with high-quality data that meets your application's requirements. Happy coding!