The createMany() Method in Laravel 12.7

Laravel’s Eloquent ORM provides a robust suite of tools for managing database relationships, with the createMany() method standing out as a critical utility for bulk insertion of related models. This article examines the implementation, limitations, and evolution of createMany() in Laravel 12.7, contextualized within broader Eloquent relationship management patterns.

Introduction to Eloquent’s createMany() Method

The createMany() method in Laravel’s Eloquent ORM is designed to streamline the insertion of multiple related models through a single method call. Unlike the create() method, which inserts a single model instance, createMany() accepts an array of attributes and persists all entries in a batch operation^1_8. This method is particularly useful for one-to-many relationships, where a parent model (e.g., a Post) needs to create multiple child models (e.g., Comment instances)^1_8.

Key Characteristics of createMany()

• Relationship-Centric: createMany() is invoked on a relationship instance (e.g., $post->comments()) rather than directly on a model class^1_8.
• Mass Assignment Compliance: Like create(), createMany() respects the $fillable and $guarded properties on the target model, ensuring adherence to mass assignment safeguards^1_5.
• Return Type: The method returns an Illuminate\Database\Eloquent\Collection containing all created models, preserving their order and allowing immediate access to database-generated attributes like primary keys^1_4.

For example:

$post = Post::find(1);
$comments = $post->comments()->createMany([
    ['message' => 'First comment'],
    ['message' => 'Second comment']
]);

Here, two Comment records are inserted with their post_id automatically set to 1, and the $comments variable holds a collection of both new models^1_8.

The N+1 Model Creation Bug in Laravel 12.7

A significant issue affecting createMany() in Laravel 12.7 emerged when combining the method with factory counts, leading to unintended quadratic (N²) model creation^1_1. This bug arose from an interaction between the count() method on factories and the createMany() implementation.

Bug Mechanism

When using Factory::count(N)->createMany(), developers expected a flat collection of N models. Instead, the method returned a nested collection of N collections, each containing N models, resulting in N² total database entries^1_1. For example:

// Expected: 3 models
// Actual: 9 models (3 collections of 3 models each)
User::factory()->count(3)->createMany();

This behavior stemmed from the factory’s internal handling of counts, which iterated over each model creation step redundantly when combined with createMany()^1_1.

Resolution and Best Practices

The Laravel team addressed this issue in a subsequent patch by decoupling the factory’s count from the createMany() method. The corrected behavior ensures that createMany() overrides any preconfigured factory count, preventing multiplicative insertion^1_1. Developers should note that explicitly passing a count to createMany() (e.g., createMany(3)) takes precedence over factory-level counts, aligning with the principle of method chaining clarity^1_1.

Evolution in Laravel 12.8: forceCreateMany() and Related Enhancements

Laravel 12.8 introduced forceCreateMany() and forceCreateManyQuietly() methods, expanding the toolkit for bulk model creation^1_2. These methods cater to scenarios requiring bypassing mass assignment restrictions or suppressing events.

forceCreateMany() Use Cases

• Overriding Guarded Attributes: Unlike createMany(), which respects $guarded, forceCreateMany() inserts data without checking mass assignment rules^1_2. This is useful for administrative operations where all attributes must be settable.
• Quiet Operations: The forceCreateManyQuietly() variant skips firing model events, optimizing performance for bulk inserts where events are unnecessary^1_2.

Example:

$post->comments()->forceCreateMany([
    ['message' => 'Urgent comment', 'priority' => 10],
    ['message' => 'Routine comment', 'priority' => 1]
]);

Here, even if priority is not in $fillable, the attribute is persisted^1_2.

Integration with Collections

The new methods integrate seamlessly with Laravel’s Collection class. For instance, transforming raw data before insertion becomes more concise:

// Before: Manual iteration
collect($rawComments)->each(fn ($comment) => $post->comments()->forceCreateQuietly($comment));

// After: Pipelined processing
collect($rawComments)
    ->map(fn ($comment) => [...$comment, 'source' => 'api'])
    ->pipe($post->comments()->forceCreateManyQuietly(...));

This pattern reduces boilerplate and enhances readability^1_2.

Common Pitfalls and Misconceptions

Misapplying createMany() on Model Classes

A frequent mistake involves invoking createMany() directly on a model class (e.g., Order::createMany()) instead of a relationship instance^1_7. Since createMany() is a relationship method, this usage triggers a MethodNotFound exception. Correct usage requires accessing the relationship first:

// Incorrect
Order::createMany([...]);

// Correct
$user = User::find(1);
$user->orders()->createMany([...]);

Confusion with insert()

Developers sometimes conflate createMany() with the insert() method, which bypasses Eloquent’s event dispatching and mass assignment checks^1_3. While insert() offers raw performance, it lacks model lifecycle integrations:

// Skips $fillable, events, and timestamps
Order::insert([...]);

// Honors Eloquent conventions
$user->orders()->createMany([...]);

Nested Relationship Challenges

When creating deeply nested relationships (e.g., Questionnaire → Question → Answer), createMany() must be applied at each level:

$questionnaire = Questionnaire::create(...);
$questions = $questionnaire->questions()->createMany([...]);

// Requires iterating over created questions
$questions->each(fn ($question) => 
    $question->answers()->createMany([...])
);

Attempting to chain createMany() across multiple levels in a single statement fails because the intermediate result is a collection, not a relationship instance^1_4.

Best Practices for Optimal createMany() Utilization

Preprocessing Data

Leverage collection methods like map or transform to prepare attribute arrays before insertion. This ensures data consistency and avoids runtime errors:

$validatedData = collect($request->products)->map(function ($product) use ($request) {
    return [
        'order_number' => $request->order_number,
        'product' => $product,
        // Additional transformations
    ];
});

$order->products()->createMany($validatedData);

Batch Size Considerations

While createMany() abstracts batch insertion, extremely large datasets (e.g., 10,000+ rows) may benefit from chunking to avoid memory exhaustion:

$chunkedData = array_chunk($largeDataset, 500);

foreach ($chunkedData as $chunk) {
    $model->children()->createMany($chunk);
}

Testing and Debugging

When testing createMany(), verify both the database state and the returned collection. Use assertions like:

$this->assertCount(5, $post->comments);
$this->assertEquals('Test comment', $post->comments->first()->message);

For debugging, inspect the generated SQL with Laravel’s query logger:

DB::enableQueryLog();
$post->comments()->createMany([...]);
dd(DB::getQueryLog());

Conclusion and Future Directions

The createMany() method exemplifies Laravel’s commitment to developer ergonomics in database interactions. While version 12.7 exhibited edge-case bugs, subsequent releases have refined its behavior, introducing complementary methods like forceCreateMany() to address advanced use cases. Developers must remain mindful of the method’s relationship-centric nature and adhere to mass assignment rules to avoid common pitfalls.

Looking ahead, further enhancements could include:

• Automatic Chunking: Built-in handling of large datasets to prevent memory issues.
• Deep Nesting Support: Syntactic sugar for creating multi-level relationships in a single statement.
• Batch Event Dispatching: Opt-in events for bulk operations to maintain consistency without performance penalties.

By mastering createMany() and its ecosystem, Laravel developers can achieve efficient, maintainable data insertion workflows, fully leveraging Eloquent’s object-relational mapping capabilities.