Eloquent Constrained Relations

Tip: Constrained Eager Loading

Post::with(['comments' => fn($q) => $q->where('approved', true)])->get();

Gotcha: whereHas vs with

whereHas filters parent models. with loads related models. They serve different purposes.

Tip: has() for Existence

Post::has('comments')->get();

Posts that have at least one comment.

Gotcha: withCount with Constraints

Post::withCount(['comments' => fn($q) => $q->where('approved', true)])->get();

Tip: whereRelation

Post::whereRelation('author', 'active', true)->get();

Shorthand for whereHas.

Gotcha: Multiple Constraints

Post::with(['comments' => fn($q) => $q->approved()->latest()->limit(5)])->get();

Tip: Use cursor() for Memory-Neutral Iteration

When exporting 100K rows, get() loads everything into memory. cursor() uses yield and keeps memory flat regardless of row count. Perfect for artisan commands.

Tip: Pivot Data Is Read-Only by Default

Many-to-many pivot columns are read-only unless you define custom pivot models. Use ->withPivot('expires_at') to make them accessible, and newPivot() to make them writable.

Gotcha: touch() Fires Multiple Queries

Calling touch() on a model updates the updated_at of ALL related models in the relationship chain. This can cascade into dozens of unnecessary writes.

Senior Insight

The constrained() method on foreign key definitions makes migrations cleaner, but it has a gotcha: it uses the table name by convention, which may not match the actual foreign key target. I've seen migrations fail because constrained() guessed the wrong table name from a non-standard foreign key column. Always verify the table name constrained() resolves to, and when in doubt, be explicit: constrained('actual_table_name').

Source: Laravel Docs (https://laravel.com/docs/eloquent), Laravel News (https://laravel-news.com/), Freek.dev (https://freek.dev/tags/eloquent)