Which approach is better and faster - Symfony2, Doctrine2 - symfony

Question

I have some related entities, let's say for convenience Product and Category. They are related OneToMany and ManyToOne. (each product has one category and one category has many products)
My goal is to display in a template all categories with all their products, but in alphabetical order. For example like this:
Furniture
Bed
Sofa
TV
Meals
Banana
Fish
Lemon
Office
Paper
Pen
I want both categories and products to be sorted.
So:
Approach 1
Write queries with doctrine to get all categories orderedBy name ASC, and to get all products orderedBy name ASC and then in the template:
{% for c in all_categories %}
{{ c.name }}
{% for p in all_products %}
{% if p.category == c %}
{{ p.name }}
{% endif %}
{% endfor %}
{% endfor %}
Approach 2
Get only the categories no matter how they are ordered. Change fetch to eager. Then write a sort filter as Twig Extension like this:
public function sortByName($a, $b)
{
if($a->getName() === $b->getName()) {
return 0;
}
if($a->getName() < $b->getName()) {
return -1;
}
return 1;
}
and using an iterator and uasort() with this function and then in the template:
{% for c in all_categories|sortbyname %}
{{ c.name }}
{% for p in c.products|sortbyname %}
{{ p.name }}
{% endfor %}
{% endfor %}
What I can see is that in 1 the if check is bad because many checks will be redundant. And getting all products when I already have all categories is also redundant. But I think that sorting with Doctrine should be faster than that with the twig extension. So I can't tell which one should I use. If it matters, in my case, I have 3 entities, like this: Each shop has categories and each category has products.
Can you please help me? Thanks very much in advance! :)

Answer 1

This is more an algo choice rather than a symfony/doctrine issue.
My approach is to get all products sorted by (category-name, product-name), and then loop over them to store them in an array indexed by your category. It can be used if you have many products, and enough memory to load all objects at one, but will be faster ( #nbproducts, and not #nbproducts*#nbcategories ), and will use only one ORM request, that will use indexes to sort data.
Php code would look like this :
$sorted_products = array();
foreach ($products as $product) {
$category = $product->getCategory();
if (!array_key_exists($category->getId(), $sorted_products)) {
$sorted_products[$category->getId()] = array('category' => $category, 'products' => array());
}
$sorted_products['products'][] = $product;
}
And then you just have to do 2 foreach in your twig :
{% for category_infos in sorted_products %}
{{ category_infos.category.name }}
{% for product in category_infos.products %}
{{ product.name }}
{% endfor %}
{% endfor %}