Loading Prevention in Extra Lazy Collections

Suppose you have an entity that has a one-to-many relation with a million of related entities. The solution is to use fetch: 'EXTRA_LAZY' and indexBy: 'id'.

This will allow working with some of the methods of the collection without loading the whole collection into memory. As long as you don't call the other methods, you will be fine.

But then one of your team members forgets about it and inadvertently calls one of the methods that triggers a full load of the collection. In their development environment, it appears fine because of the much smaller dataset. It would pass CI and be deployed to production. But in production, everything immediately grinds to a halt because it tries to load a million records into memory.

A solution to prevent this problem is to decorate the collection to throw an exception if an unsafe method is called.

The list of safe methods is listed in the documentation of Extra Lazy Association. They are: contains(), containsKey(), count(), get(), slice(), add(), and offsetSet() if the first argument is null. We also add matching() to that list.

The Decorator Class

This package already comes with ExtraLazyCollection for this purpose.

info

While ExtraLazyCollection only allows the safe methods, they still implement the Collection interface so that the object can still be used in places where a Collection is expected.

Usage Example in Entities

use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
use Rekalogika\Collections\Decorator\ExtraLazy\ExtraLazyCollection;

#[ORM\Entity()]
class BookShelf
{
    // our bookshelf has a million of books...
    #[ORM\OneToMany(
        targetEntity: Book::class,
        fetch: 'EXTRA_LAZY', // needs this, or the safe methods become unsafe
        indexBy: 'id', // needs this, or containsKey() & get() become unsafe
    )]
    private Collection $books;

    public function getBooks(): Collection
    {
        return new ExtraLazyCollection($this->books);
    }
}