Symfony2 OneToMany bidirectional referencing not id column - php

Question

I depends on an external api to populate my tables, and with this relationships i can handle some required functions on the app with less queries.
Instead of the errors and warnings the tables and FK are created after use the command, but i dont know if i can just bypass this errors or it will generate problems in the future.
Obviously i can just references the id and the problem will dissapear, but need to now if this is possible.
I have two tables:
RARITIES
id
name
...
ITEMS
id
item_rarity
...
And the entities looks like:
class Rarity
{
...
/**
* #ORM\OneToMany(targetEntity="Item", mappedBy="rarity")
*/
private $items;
public function __construct() {
$this->items = new ArrayCollection();
}
...
}
class Item
{
...
/**
* #ORM\ManyToOne(targetEntity="Rarity", inversedBy="items")
* #ORM\JoinColumn(name="item_rarity", referencedColumnName="name")
**/
private $rarity;
...
}
When i create or update the schema, it outputs some errors and warnings:
[Doctrine\ORM\Tools\ToolsException]
Schema-Tool failed with Error 'An exception occurred while executing 'ALTER TABLE items ADD CONSTRAINT FK_E11EE94D3139CB89 FOREIGN KEY (item_rarity) REFERENCES rarities (name)':
SQLSTATE[HY000]: General error: 1005 Can't create table 'd2a.#sql-4fa_7c' (errno: 150)' while executing DDL: ALTER TABLE items ADD CONSTRAINT FK_E11EE94D3139CB89 FOREIGN KEY (item_rarity) REFERENCES rarities (name)
[Doctrine\DBAL\DBALException]
An exception occurred while executing 'ALTER TABLE items ADD CONSTRAINT K_E11EE94D3139CB89 FOREIGN KEY (item_rarity) REFERENCES rarities (name)':
SQLSTATE[HY000]: General error: 1005 Can't create table 'd2a.#sql-4fa_7c' (errno: 150)
[PDOException]
SQLSTATE[HY000]: General error: 1005 Can't create table 'd2a.#sql-4fa_7c' (errno: 150
Thanks in advice!

Answer 1

I suspect this has something to do with trying to link the two via 'name', which Doctrine does not believe to be a unique Identifier. There could be two Rarities with the same name as far as Doctrine is concerned. The reason 'id' works is because it is declared as the Primary key in the annotation using #Id, and therefore assumed to be unique:
/**
* #ORM\Column(type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
Without looking into it, I would assume that this relationship requires that Items references back to a Primary key.

Answer 2

First of all, thanks to Alex, he gives me the idea of whats going on.
Like he said "There could be two Rarities with the same name as far as Doctrine is concerned" so, lets make rarities.name column as unique:
/**
* Rarity
*
* #ORM\Table(name="rarities",
* uniqueConstraints={#ORM\UniqueConstraint(name="unique_name", columns={"name"})})
* #ORM\Entity
*/
class Rarity
{
And it works, no errors, no warnings, column items.item_rarity referencing rarities.name, and rarities.name is not a primary key in the table.
I hope it helps others, it took me time!