Here is a detailed example of using Laravel's `loadMissing` method with a collection of users, including explanation:
Context:
`loadMissing` is used to eager load relationships on a collection of Eloquent models only if those relationships have not already been loaded. This avoids redundant database queries and prevents the N+1 query problem while allowing you to conditionally load relationships after the initial query.
Example of Using `loadMissing` with a Collection of Users
Assume you have a `User` model with relationships like `posts` and `comments`. You want to load these relationships only if they are not already loaded on the user models in your collection.
php
use App\Models\User;
// Retrieve a collection of users
$users = User::where('active', true)->get();
// Later in the code, you want to ensure 'posts' and 'comments' are loaded,
// but only if they haven't been loaded yet
$users->loadMissing(['posts', 'comments']);
// Now you can safely access $user->posts and $user->comments without triggering extra queries
foreach ($users as $user) {
echo $user->name . " has " . $user->posts->count() . " posts and " . $user->comments->count() . " comments.\n";
}
Explanation
- `User::where('active', true)->get()` fetches a collection of active users.
- `$users->loadMissing(['posts', 'comments'])` checks if each user model in the collection already has the `posts` and `comments` relationships loaded.
- For any user where these relationships are not loaded, Laravel will perform an efficient eager load query to fetch them for all such users at once.
- If some users already have these relationships loaded (e.g., from a previous query), Laravel skips loading them again.
- This method helps avoid unnecessary queries and improves performance, especially when dealing with large collections.
Additional Notes
- You can also pass closure constraints for conditional eager loading:
php
$users->loadMissing(['posts' => function ($query) {
$query->where('published', true);
}]);
- This will only load published posts if the `posts` relationship is missing.
- `loadMissing` works similarly to `load`, but `load` will always reload the relationships regardless of whether they are already loaded.
This approach is particularly useful in APIs or complex applications where you may want to conditionally load relationships on a collection of models without repeating queries or overriding previously loaded relations[5][6][9].
Citations:
[1] https://stackoverflow.com/questions/60323123/how-to-load-all-datas-in-a-mongodb-collection-using-mongoose
[2] https://www.squash.io/exploring-mongodb-does-it-load-documents-when-querying/
[3] https://www.mongodb.com/community/forums/t/i-want-to-create-a-user-collection-with-role-field/174322
[4] https://stackoverflow.com/questions/35834466/query-data-in-one-collection-based-on-data-in-another-collection-in-mongodb/35840304
[5] https://laravel.com/docs/11.x/eloquent-collections
[6] https://laravel-news.com/loadMissing
[7] https://github.com/laravel/framework/discussions/43418
[8] https://www.mongodb.com/community/forums/t/mongodb-spark-connector-v10-1-1-failing-to-read-from-some-mongo-tables/224114
[9] https://stackoverflow.com/questions/47238937/laravel-what-is-the-purpose-of-the-loadmissing-function
[10] https://pusher.com/blog/advanced-laravel-eloquent-usage/