Bulk Creating Data with Auto-Incrementing Primary Keys in Sequelize

Sequelize is an Object-Relational Mapping (ORM) library that simplifies the interaction between a database and your application. One of its most useful features is bulk creating data, which allows you to insert multiple records into a table with a single query.

However, when working with auto-incrementing primary keys, things can get more complex. In this article, we’ll delve into the world of bulk creating data in Sequelize and explore why null values are being inserted into the primary key column.

Understanding Auto-Incrementing Primary Keys

Before we dive into the issue at hand, let’s quickly discuss auto-incrementing primary keys. In most databases, including PostgreSQL, primary keys are unique identifiers that can be used to reference a record in the table. One common method of generating these unique identifiers is through an auto-incrementing mechanism.

In Sequelize, the autoIncrement option is set to true by default for the primary key column (in this case, id). This means that whenever a new record is inserted into the table, the database will automatically assign a new, unique value to the primary key column based on the sequence it’s configured.

Bulk Creating Data with Auto-Incrementing Primary Keys

Now, let’s look at the code snippet provided by the user. The ProjectCategory.bulkCreate method is used to insert multiple records into the project_categories table in a single query.

await ProjectCategory.bulkCreate(
  projectCategoryIds?.map(categoryId =&gt; ({ categoryId, projectId: newProject.id })),
  {
    returning: true,
    transaction: t
  }
);

As we can see, the bulkCreate method takes an array of objects as its first argument. Each object represents a record to be inserted into the table.

The second argument is an options object that configures how the bulk create operation should be performed. In this case, the returning: true option tells Sequelize to return the values of all columns (including primary key) in each row as part of the result set.

Transaction and Transaction Management

In the provided code snippet, a transaction is created using await sequelize.transaction(async (t) => { ... }). This ensures that either both bulk create operations are successful or neither one is.

However, there’s an important distinction between the primary key column and other columns in this context. The returning option tells Sequelize to return the values of all columns, including the primary key (id). However, when using an auto-incrementing primary key, you might expect that it should be set automatically by the database.

Why are null values being inserted into the primary key column?

Let’s take a closer look at the migration script provided for creating the project_categories table. The id column is defined as having autoIncrement: true, which means that Sequelize will generate unique values for this column automatically.

However, when using bulkCreate with an auto-incrementing primary key, the issue arises because Sequelize doesn’t know how to handle the generated value (which is typically stored in the database sequence) during bulk creation. In other words, Sequelize needs to know what value should be inserted into the primary key column for each record.

To resolve this issue, we need to set returning: false in our options object so that only non-key columns are returned and their values can be used to update the key fields of the objects we’re creating.

Here’s how you might modify your bulk create operation:

await ProjectCategory.bulkCreate(
  projectCategoryIds?.map(categoryId =&gt; ({ categoryId, projectId: newProject.id })),
  {
    returning: false,
    transaction: t
  }
);

With this change, the generated value for the primary key column will be stored in a separate object within the result set returned by the bulk create operation. We can then access these values and use them to update the id field of our objects.

Using Return Values for Updating Auto-Generated Primary Keys

Now that we’ve understood how Sequelize handles auto-incrementing primary keys, let’s explore an alternative approach to updating the key fields using return values from the bulk create operation.

Instead of using bulkCreate, consider using createMany with a callback function:

ProjectCategory.createMany({
  data: projectCategoryIds,
}, {
  returning: true,
}).then((result) =&gt; {
  const ids = result.data.map((data) =&gt; data.id);
  // Now you can update your object's 'id' field with the correct value:
  newProject.id = ids[0];
});

In this approach, we’re using createMany instead of bulkCreate, which allows us to use a callback function and access the values returned by the database in a more explicit way.

By following these steps and modifications, you should be able to resolve the issue with null values being inserted into your primary key column when using Sequelize’s bulk create operation.

Last modified on 2024-10-04