The `loadMissing` method in Laravel Pennant is used primarily for eager loading feature flag values only when they have not already been loaded for a given scope or collection of scopes. This helps optimize performance by preventing redundant queries or lookups for feature flags that are already cached or loaded in memory during the current request lifecycle.
Detailed Use Cases for `loadMissing` in Pennant
- Avoiding Redundant Feature Value Loads: When you have a collection of scopes (e.g., users) and want to ensure that certain feature flags are loaded for them, `loadMissing` will only load those feature flags that have not been previously loaded. This prevents repeating database or cache queries for feature flags that are already available, improving efficiency.
- Performance Optimization in Loops: If you are iterating over a large collection of scopes and checking feature flags inside the loop, using `loadMissing` beforehand ensures that only missing feature values are fetched in bulk, avoiding the N+1 query problem where a query is executed for each iteration.
- Incremental Feature Loading: In scenarios where some feature flags may have been loaded earlier in the request and others need to be loaded later conditionally, `loadMissing` allows you to load only the additional missing feature flags without reloading the ones already present.
- Working with Collections of Scopes: When dealing with collections of models or scopes, `loadMissing` is useful to selectively eager load feature flags for all models in the collection if they aren't already loaded, ensuring consistent feature flag availability without unnecessary overhead.
- Complementing `load` and `loadAll` Methods: While `load` eagerly loads specified feature flags regardless of whether they were loaded before, and `loadAll` loads all defined features, `loadMissing` provides a middle ground by loading only those that are missing, which can be particularly useful in complex applications with dynamic feature flag usage patterns.
Example Usage
php
Feature::for($users)->loadMissing([
'new-api',
'purchase-button',
'notifications-beta',
]);
In this example, feature flags `new-api`, `purchase-button`, and `notifications-beta` will be loaded only if they have not been loaded yet for the given users, thus avoiding repeated queries or cache lookups for already loaded flags[1].
Summary
The `loadMissing` method is a performance optimization tool in Laravel Pennant that ensures feature flags are loaded only when necessary, preventing redundant operations and reducing database or cache load. It is especially useful when working with collections of scopes and when feature flags may be loaded incrementally throughout a request lifecycle. This method helps maintain efficient feature flag resolution and avoids the N+1 query problem common in feature flag checks within loops[1][4][5].
Citations:
[1] https://laravel.com/docs/11.x/pennant
[2] https://laracasts.com/discuss/replies/964941
[3] https://hackernoon.com/how-to-manage-feature-flags-with-laravel-pennant
[4] https://stackoverflow.com/questions/47238937/laravel-what-is-the-purpose-of-the-loadmissing-function
[5] https://laravel.com/docs/11.x/eloquent-collections
[6] https://laracasts.com/episodes/2685
[7] https://laravel.com/docs/11.x/eloquent-relationships
[8] https://github.com/laravel/pennant/issues/62