Retrieving All MorphedByMany Relations in Laravel Eloquent

When dealing with polymorphic many-to-many relationships in Laravel, such as the morphedByMany setup you've described, developers often face a common challenge: how to efficiently retrieve all related models across different types (e.g., posts, videos, photos) in a single query or collection without hardcoding every possible relationship.

This post will dive into the mechanics of polymorphic relationships and provide practical strategies for querying these dynamic connections in Eloquent.

Understanding Polymorphic Relationships

As shown in the documentation, morphedByMany relations allow a model (like a Tag) to belong to multiple other models, where the target model can be one of several different types. This is achieved using two columns on the pivot table: taggable_id and taggable_type.

// Example definition from documentation context
public function posts()
{
    return $this->morphedByMany('App\Post', 'taggable');
}

The key takeaway here is that the relationship itself is defined specifically for one type (e.g., posts only returns Post models). To get all potential relationships dynamically, we need a query strategy that doesn't rely on statically named methods.

The Challenge: Unifying Polymorphic Relations

The difficulty arises when you want to fetch all related entities—whether they are posts, videos, or future photos—from a single parent model (like a Tag). If you try to iterate through known methods (posts(), videos()), you miss any other polymorphic targets. We need a way to query the database based on the dynamic nature of the relationship.

Strategy 1: Dynamic Querying via Raw Relations

Since Eloquent relationships are defined statically, retrieving all possible related models requires querying the pivot table directly or using advanced scope methods. The most robust approach involves leveraging the whereHas method combined with dynamic type checking if you know the potential model names ahead of time.

If we assume we know the possible polymorphic types (Post, Video, etc.), we can build a collection dynamically:

use App\Models\Tag;

class Tag extends Model
{
    public function getAllRelatedEntities()
    {
        // Define all potential polymorphic targets you expect to find.
        $relations = [
            'posts' => 'App\Post',
            'videos' => 'App\Video',
            // Add future relations here: 'photos' => 'App\Photo',
        ];

        $results = collect();

        foreach ($relations as $alias => $type) {
            // Use whereHas to fetch only the models matching that specific type.
            $results->push($this->relationLoaded($alias) ? $this->relationLoaded($alias)->get() : $this->relationLoaded($alias)?->where('taggable_type', $type)->get());
        }

        return $results->flatten()->unique(); // Flatten and remove duplicates if necessary
    }
}

While the above example demonstrates a logical approach, for true database efficiency when dealing with many disparate polymorphic types, direct SQL or using specialized package features (like those often found in advanced Eloquent patterns) can be more performant. For complex data retrieval, understanding how Eloquent interacts with the underlying database structure is crucial, especially when optimizing queries—a key concept emphasized by resources like laravelcompany.com.

Strategy 2: The Eager Loading Approach (Best Practice)

A cleaner approach for large datasets, instead of manually stitching together multiple whereHas calls, is to define a generic scope or use conditional eager loading if you can predict the types. However, when dealing with truly unknown future relations, dynamically building the query using raw relations combined with type filtering remains powerful.

For maximum flexibility and adherence to Eloquent principles, focus on defining clear, explicit relationships for each entity type rather than trying to force a single polymorphic method to return everything. If you frequently need to fetch related data across many types, consider structuring your models to allow these queries to be easily generated, perhaps using custom scopes instead of relying solely on the polymorphic definition.

Conclusion

Retrieving all morphedByMany relations in one go requires moving beyond simple method calls and embracing dynamic querying strategies. By understanding that the polymorphism is rooted in separate model types, we can construct queries that filter the pivot table based on the taggable_type. While defining static methods for each type is clean for specific use cases, employing dynamic collection building allows you to handle evolving polymorphic structures gracefully. Always prioritize clear, optimized database interaction when dealing with complex Eloquent relationships, ensuring your application remains performant and maintainable.