Composite Primary Keys in Laravel 5 Models

Many databases employ composite primary keys, where multiple columns form the unique identifier for each row. Laravel's default primary key, "id," may not always suffice in these cases.

Composite Key Implementation

To define composite primary keys in Laravel 5 models, you can employ a PHP trait such as the following:

trait HasCompositePrimaryKey
{
    ...
    // ... Additional code from the answer ...
    ...
}

Include this trait in your model and set the $primaryKey property to an array representing the composite keys:

class MyModel extends Eloquent
{
    use Traits\HasCompositePrimaryKey;

    protected $primaryKey = ['key1', 'key2'];
    ...
}

Laravel Modifications

The trait overrides certain Laravel methods to handle composite keys:

• getIncrementing(): Returns false to indicate non-incrementing primary keys.
• setKeysForSaveQuery(): Builds a query filter based on the composite keys for save operations.
• find(): Custom method that accepts an array of key values for record retrieval.

Caveats and Limitations

Although this solution provides a workaround for composite keys, it has some limitations:

• It requires modification of the Laravel framework, which may not be desirable in all scenarios.
• It may not be suitable for complex use cases involving relationships, eager loading, and other advanced features.
• The find() method may require adjustments to accommodate different data types and index structures.

Alternative Approaches

If the trait solution proves unsuitable, consider using custom primary keys or a different method for managing composite keys. Consult with Laravel documentation and online resources for further guidance.