Delete associated/referenced entity - doctrine-orm

Question

I have a table product, the items in these table are referenced in tables such as cart_item and order_item as well as shipping_item etc.
All these references are optional (the product_id is set to nullable in those tables).
I need to have a way to delete a product and still keeping the other tables's records. One way I can think of is to go into all those tables, set the product_id to null, then go back to the product table to delete. However, since I may not know all the tables that are referencing to product (many other bundles can have entities that are referencing to this product), is there a way that I can know all these association to loop through and set null?
(Or perhaps there is a better way?)
PS: the idea that this is a shopping cart and the owner may want to remove expired products to clean up but for ordered, shipped items they still need to keep records.
Edit1:
This is the definition of the product reference in the OrderItem entity:
/**
* #var \Product
*
* #ORM\ManyToOne(targetEntity="Product")
* #ORM\JoinColumns({
* #ORM\JoinColumn(name="product_id", referencedColumnName="id")
* })
*/
private $product;
The error I'm getting:
PDOException: SQLSTATE[23000]: Integrity constraint violation: 1451
Cannot delete or update a parent row: a foreign key constraint fails
(test.order_item, C ONSTRAINT fk_order_item_product1 FOREIGN KEY
(product_id) REFERENCES product (id) ON DELETE NO ACTION ON
UPDATE NO ACTION)
Edit2:
I initially set onupdate="SET NULL" to the order_item entity and thought that was enough, it was not:
/**
* #var \Product
*
* #ORM\ManyToOne(targetEntity="Product")
* #ORM\JoinColumns({
* #ORM\JoinColumn(name="product_id", referencedColumnName="id", nullable=true, onDelete="SET NULL")
* })
*/
private $product;
After that, I had to update db schema as well.

Answer 1

Assuming you have the proper relations set up between the owning entity product and the other entities e.g. cart_item that should have a foreign_key, your wanted behaviour is the default for doctrine 2.
Take a look here in the manual
As an example they show the deletion of a User entity and its corresponding Comments
$user = $em->find('User', $deleteUserId);
foreach ($user->getAuthoredComments() AS $comment) {
$em->remove($comment);
}
$em->remove($user);
$em->flush();
The example states:
Without the loop over all the authored comments Doctrine would use an UPDATE statement only to set the foreign key to NULL and only the User would be deleted from the database during the flush()-Operation.
This suggests to me that in your case you actually want that behaviour. So just remove the product entity and doctrine 2 will automatically find all other entities with a foreign_key belonging to that product and will set it to NULL
Edit
Your error message suggests that upon attempted removal of the product entity there are still foreign_keys present, i.e. they have not been set to null properly by Doctrine.
You need to be sure to add the cascade property, specifically remove to your entity relationship. It would look something like the following:
<?php
class Product
{
//...
/**
* Bidirectional - One-To-Many (INVERSE SIDE)
*
* #OneToMany(targetEntity="Cart", mappedBy="product", cascade={"remove"})
*/
private $carts;
//...
}