Symfony / Doctrine - OneToMany too many queries - symfony

Question

is there a way to lower lower one to many queries?
I have self-referenced one to many entity(category tree). I'm trying to get all children like this:
private function getChildren(string $category): array
{
$em = $this->getDoctrine();
$category = $em->getRepository(Category::class)->getByUrl($category);
$children = $category->getChildren();
$childrenArr = [];
if (!empty($children)) {
foreach ($children as $child) {
$childrenArr[] = $child->getId();
if (!empty($child->getChildren())) {
$this->getChildren($child->getUrl(), $childrenArr);
}
}
}
return $childrenArr;
}
Here is my repository:
public function getByUrl(string $url)
{
$qb = $this->createQueryBuilder('c');
$qb->where('c.url = :url');
$qb->setParameter('url', $url);
return $qb->getQuery()->useQueryCache(true)->getSingleResult();
}
Problem is, if it finds 5 children, it creates 57 queries... It's ridiculous.
UPDATE:
Entity structure:
/**
* One Category has Many Subcategories.
* #ORM\OneToMany(targetEntity="Category", mappedBy="parent", cascade={"persist"}, fetch="EAGER"))
*/
private $children;
/**
* Many Subcategories have One Category.
* #ORM\ManyToOne(targetEntity="Category", inversedBy="children", cascade={"persist"}, fetch="EAGER")
* #ORM\JoinColumn(name="parent_id", referencedColumnName="id")
*/
private $parent;
/**
* Add child
*
* #param \App\Entity\Product\Category $child
*
* #return Category
*/
public function addChild(\App\Entity\Product\Category $child): Category
{
$this->children[] = $child;
return $this;
}
/**
* Remove child
*
* #param \App\Entity\Product\Category $child
*/
public function removeChild(\App\Entity\Product\Category $child)
{
$this->children->removeElement($child);
}
/**
* Get children
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getChildren(): Collection
{
return $this->children;
}
/**
* Set parent
*
* #param \App\Entity\Product\Category $parent
*
* #return Category
*/
public function setParent(\App\Entity\Product\Category $parent = null): Category
{
$this->parent = $parent;
return $this;
}
/**
* Get parent
*
* #return \App\Entity\Product\Category
*/
public function getParent()
{
return $this->parent;
}
/**
* Add products
*
* #param \App\Entity\Product\Product $products
*
* #return Category
*/
public function addProducts(\App\Entity\Product\Product $products)
{
$this->products[] = $products;
return $this;
}
/**
* Remove products
*
* #param \App\Entity\Product\Product $products
*/
public function removeProducts(\App\Entity\Product\Product $products)
{
$this->products->removeElement($products);
}
/**
* Get products
*
* #return \Doctrine\Common\Collections\Collection
*/
public function getProducts()
{
return $this->products;
}
Used fetch=EAGER it removed 2 queries(was 57 now its 55)

Answer 1

To avoid too many queries when I request all children, I do a fetch="EAGER" on my entity, it will automatically do a innerJoin from children table.
Ex:
/**
* #ORM\OneToMany(targetEntity="CoreBundle\Entity\Category", mappedBy="parent", cascade={"persist", "remove"}, fetch="EAGER")
*/
private $children;