Doctrine 2 schema update produces MySQL errno 150, Foreign Key constraint

Question

When using Doctrine ORM in Symfony2, I have the following tables generated from three different entities, of which accessory has two foreign key constraints (marked A and B below).

describe publication;
+-------------------+--------------+------+-----+---------+----------------+
| Field             | Type         | Null | Key | Default | Extra          |
+-------------------+--------------+------+-----+---------+----------------+
| id                | int(11)      | NO   | PRI | NULL    | auto_increment |
| kid               | varchar(10)  | NO   |     | NULL    |                |
| title             | varchar(255) | NO   |     | NULL    |                |
| title_canonical   | varchar(255) | NO   |     | NULL    |                | <- A
| created           | datetime     | NO   |     | NULL    |                |
| modified          | datetime     | NO   |     | NULL    |                |
+-------------------+--------------+------+-----+---------+----------------+

describe accessory;
+-------------------+--------------+------+-----+---------+----------------+
| Field             | Type         | Null | Key | Default | Extra          |
+-------------------+--------------+------+-----+---------+----------------+
| id                | int(11)      | NO   | PRI | NULL    | auto_increment |
| publication_title | varchar(255) | YES  |     | NULL    |                | <- A
| index_id          | int(11)      | NO   |     | NULL    |                |
| index_alias       | varchar(255) | NO   |     | NULL    |                |
| value             | longtext     | NO   |     | NULL    |                |
| attribute_name    | varchar(255) | YES  |     | NULL    |                | <- B
+-------------------+--------------+------+-----+---------+----------------+

describe attribute;
+-------------------+--------------+------+-----+---------+----------------+
| Field             | Type         | Null | Key | Default | Extra          |
+-------------------+--------------+------+-----+---------+----------------+
| id                | int(11)      | NO   | PRI | NULL    | auto_increment |
| name              | varchar(255) | NO   |     | NULL    |                |
| name_canonical    | varchar(255) | NO   |     | NULL    |                | <- B
| parameter         | varchar(16)  | NO   |     | NULL    |                |
+-------------------+--------------+------+-----+---------+----------------+

The foreign keys are mapped with annotations:

Publication.php

/**
 * @ORM\OneToMany(targetEntity="Accessory", mappedBy="publication")
 */
protected $accessories;

Accessory.php

/**
 * @ORM\ManyToOne(targetEntity="Publication", inversedBy="accessories")
 * @ORM\JoinColumn(name="publication_title", referencedColumnName="title_canonical")
 */
protected $publication;


/**
 * @ORM\ManyToOne(targetEntity="Attribute", inversedBy="accessories")
 * @ORM\JoinColumn(name="attribute_name", referencedColumnName="name_canonical")
 */
protected $attribute;

Attribute.php

/**
 * @ORM\OneToMany(targetEntity="Accessory", mappedBy="attribute")
 */
protected $accessories;

but upon running php app/console doctrine:schema:update --force I got this exception

[Doctrine\DBAL\DBALException]                                                                                                                                               
An exception occurred while executing 'ALTER TABLE accessory ADD CONSTRAINT FK_A1B1251CCEE83EE7 FOREIGN KEY (publication_title) REFERENCES publication (title_canonical)':  

SQLSTATE[HY000]: General error: 1005 Can't create table 'publicationsapp.#sql-2a3c_2828' (errno: 150)

So I ran php app/console doctrine:schema:update --dump-sql

ALTER TABLE accessory ADD CONSTRAINT FK_A1B1251CCEE83EE7 FOREIGN KEY (publication_title) REFERENCES publication (title_canonical);
ALTER TABLE accessory ADD CONSTRAINT FK_A1B1251C5CBDA8E FOREIGN KEY (attribute_name) REFERENCES attribute (name_canonical);
CREATE INDEX IDX_A1B1251CCEE83EE7 ON accessory (publication_title);
CREATE INDEX IDX_A1B1251C5CBDA8E ON accessory (attribute_name);

What's the correct way to resolve this? Should I edit the tables manually or with Doctrine?

Based on what I've read about errno 150, the foreign column needs to be indexed, but can't Doctrine handle this automatically?

Answer 1

One could add unique=true to both $nameCanonical and $titleCanonical properties or whichever columns are referenced by the foreign key. Then drop and run the schema update command to recreate the tables.

In the case of $titleCanonical

/**
 * @var string
 *
 * @ORM\Column(name="title_canonical", type="string", length=255, unique=true)
 */
private $titleCanonical;

But ideally with Doctrine, the foreign keys should be referenced to the other table's primary key to make it valid.