352 lines
10 KiB
ReStructuredText
352 lines
10 KiB
ReStructuredText
Composite and Foreign Keys as Primary Key
|
|
=========================================
|
|
|
|
Doctrine 2 supports composite primary keys natively. Composite keys are a very powerful relational database concept
|
|
and we took good care to make sure Doctrine 2 supports as many of the composite primary key use-cases.
|
|
For Doctrine 2.0 composite keys of primitive data-types are supported, for Doctrine 2.1 even foreign keys as
|
|
primary keys are supported.
|
|
|
|
This tutorial shows how the semantics of composite primary keys work and how they map to the database.
|
|
|
|
General Considerations
|
|
~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Every entity with a composite key cannot use an id generator other than "ASSIGNED". That means
|
|
the ID fields have to have their values set before you call ``EntityManager#persist($entity)``.
|
|
|
|
Primitive Types only
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Even in version 2.0 you can have composite keys as long as they only consist of the primative types
|
|
``integer`` and ``string``. Suppose you want to create a database of cars and use the model-name
|
|
and year of production as primary keys:
|
|
|
|
.. configuration-block::
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
namespace VehicleCatalogue\Model;
|
|
|
|
/**
|
|
* @Entity
|
|
*/
|
|
class Car
|
|
{
|
|
/** @Id @Column(type="string") */
|
|
private $name;
|
|
/** @Id @Column(type="integer") */
|
|
private $year
|
|
|
|
public function __construct($name, $year)
|
|
{
|
|
$this->name = $name;
|
|
$this->year = $year;
|
|
}
|
|
|
|
public function getModelName()
|
|
{
|
|
return $this->name;
|
|
}
|
|
|
|
public function getYearOfProduction()
|
|
{
|
|
return $this->year;
|
|
}
|
|
}
|
|
|
|
.. code-block:: xml
|
|
|
|
<?xml version="1.0" encoding="UTF-8"?>
|
|
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
|
|
http://www.doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
|
|
|
|
<entity name="VehicleCatalogue\Model\Car">
|
|
<id field="name" type="string" />
|
|
<id field="year" type="integer" />
|
|
</entity>
|
|
</doctrine-mapping>
|
|
|
|
.. code-block:: yaml
|
|
|
|
VehicleCatalogue\Model\Car:
|
|
type: entity
|
|
id:
|
|
name:
|
|
type: string
|
|
year:
|
|
type: integer
|
|
|
|
Now you can use this entity:
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
namespace VehicleCatalogue\Model;
|
|
|
|
// $em is the EntityManager
|
|
|
|
$car = new Car("Audi A8", 2010);
|
|
$em->persist($car);
|
|
$em->flush();
|
|
|
|
And for querying you can use arrays to both DQL and EntityRepositories:
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
namespace VehicleCatalogue\Model;
|
|
|
|
// $em is the EntityManager
|
|
$audi = $em->find("VehicleCatalogue\Model\Car", array("name" => "Audi A8", "year" => 2010));
|
|
|
|
$dql = "SELECT c FROM VehicleCatalogue\Model\Car c WHERE c.id = ?1";
|
|
$audi = $em->createQuery($dql)
|
|
->setParameter(1, array("name" => "Audi A8", "year" => 2010))
|
|
->getSingleResult();
|
|
|
|
You can also use this entity in associations. Doctrine will then generate two foreign keys one for ``name``
|
|
and to ``year`` to the related entities.
|
|
|
|
.. note::
|
|
|
|
This example shows how you can nicely solve the requirement for existing
|
|
values before ``EntityManager#persist()``: By adding them as mandatory values for the constructor.
|
|
|
|
Identity through foreign Entities
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
.. note::
|
|
|
|
Identity through foreign entities is only supported with Doctrine 2.1
|
|
|
|
There are tons of use-cases where the identity of an Entity should be determined by the entity
|
|
of one or many parent entities.
|
|
|
|
- Dynamic Attributes of an Entity (for example Article). Each Article has many
|
|
attributes with primary key "article_id" and "attribute_name".
|
|
- Address object of a Person, the primary key of the adress is "user_id". This is not a case of a composite primary
|
|
key, but the identity is derived through a foreign entity and a foreign key.
|
|
- Join Tables with metadata can be modelled as Entity, for example connections between two articles
|
|
with a little description and a score.
|
|
|
|
The semantics of mapping identity through foreign entities are easy:
|
|
|
|
- Only allowed on Many-To-One or One-To-One associations.
|
|
- Plug an ``@Id`` annotation onto every association.
|
|
- Set an attribute ``association-key`` with the field name of the association in XML.
|
|
- Set a key ``associationKey:`` with the field name of the association in YAML.
|
|
|
|
Use-Case 1: Dynamic Attributes
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
We keep up the example of an Article with arbitrary attributes, the mapping looks like this:
|
|
|
|
.. configuration-block::
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
namespace Application\Model;
|
|
|
|
use Doctrine\Common\Collections\ArrayCollection;
|
|
|
|
/**
|
|
* @Entity
|
|
*/
|
|
class Article
|
|
{
|
|
/** @Id @Column(type="integer") @GeneratedValue */
|
|
private $id;
|
|
/** @Column(type="string") */
|
|
private $title;
|
|
|
|
/**
|
|
* @OneToMany(targetEntity="ArticleAttribute", mappedBy="article", cascade={"ALL"}, indexBy="attribute")
|
|
*/
|
|
private $attributes;
|
|
|
|
public function addAttribute($name, $value)
|
|
{
|
|
$this->attributes[$name] = new ArticleAttribute($name, $value, $this);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @Entity
|
|
*/
|
|
class ArticleAttribute
|
|
{
|
|
/** @Id @ManyToOne(targetEntity="Article", inversedBy="attributes") */
|
|
private $article;
|
|
|
|
/** @Id @Column(type="string") */
|
|
private $attribute;
|
|
|
|
/** @Column(type="string") */
|
|
private $value;
|
|
|
|
public function __construct($name, $value, $article)
|
|
{
|
|
$this->attribute = $name;
|
|
$this->value = $value;
|
|
$this->article = $article;
|
|
}
|
|
}
|
|
|
|
.. code-block:: xml
|
|
|
|
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
|
|
http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
|
|
|
|
<entity name="Application\Model\ArticleAttribute">
|
|
<id name="article" association-key="true" />
|
|
<id name="attribute" type="string" />
|
|
|
|
<field name="value" type="string" />
|
|
|
|
<many-to-one field="article" target-entity="Article" inversed-by="attributes" />
|
|
<entity>
|
|
|
|
</doctrine-mapping>
|
|
|
|
.. code-block:: yaml
|
|
|
|
Application\Model\ArticleAttribute:
|
|
type: entity
|
|
id:
|
|
article:
|
|
associationKey: true
|
|
attribute:
|
|
type: string
|
|
fields:
|
|
value:
|
|
type: string
|
|
manyToOne:
|
|
article:
|
|
targetEntity: Article
|
|
inversedBy: attributes
|
|
|
|
|
|
Use-Case 2: Simple Derived Identity
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Sometimes you have the requirement that two objects are related by a One-To-One association
|
|
and that the dependent class should re-use the primary key of the class it depends on.
|
|
One good example for this is a user-address relationship:
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
/**
|
|
* @Entity
|
|
*/
|
|
class User
|
|
{
|
|
/** @Id @Column(type="integer") @GeneratedValue */
|
|
private $id;
|
|
}
|
|
|
|
/**
|
|
* @Entity
|
|
*/
|
|
class Address
|
|
{
|
|
/** @Id @OneToOne(targetEntity="User") */
|
|
private $user;
|
|
}
|
|
|
|
Use-Case 3: Join-Table with Metadata
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
In the classic order product shop example there is the concept of the order item
|
|
which contains references to order and product and additional data such as the amount
|
|
of products purchased and maybe even the current price.
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
use Doctrine\Common\Collections\ArrayCollection;
|
|
|
|
/** @Entity */
|
|
class Order
|
|
{
|
|
/** @Id @Column(type="integer") @GeneratedValue */
|
|
private $id;
|
|
|
|
/** @ManyToOne(targetEntity="Customer") */
|
|
private $customer;
|
|
/** @OneToMany(targetEntity="OrderItem", mappedBy="order") */
|
|
private $items;
|
|
|
|
/** @Column(type="boolean") */
|
|
private $payed = false;
|
|
/** @Column(type="boolean") */
|
|
private $shipped = false;
|
|
/** @Column(type="datetime") */
|
|
private $created;
|
|
|
|
public function __construct(Customer $customer)
|
|
{
|
|
$this->customer = $customer;
|
|
$this->items = new ArrayCollection();
|
|
$this->created = new \DateTime("now");
|
|
}
|
|
}
|
|
|
|
/** @Entity */
|
|
class Product
|
|
{
|
|
/** @Id @Column(type="integer") @GeneratedValue */
|
|
private $id;
|
|
|
|
/** @Column(type="string") */
|
|
private $name;
|
|
|
|
/** @Column(type="decimal") */
|
|
private $currentPrice;
|
|
|
|
public function getCurrentPrice()
|
|
{
|
|
return $this->currentPrice;
|
|
}
|
|
}
|
|
|
|
/** @Entity */
|
|
class OrderItem
|
|
{
|
|
/** @Id @ManyToOne(targetEntity="Order") */
|
|
private $order;
|
|
|
|
/** @Id @ManyToOne(targetEntity="Product") */
|
|
private $product;
|
|
|
|
/** @Column(type="integer") */
|
|
private $amount = 1;
|
|
|
|
/** @Column(type="decimal") */
|
|
private $offeredPrice;
|
|
|
|
public function __construct(Order $order, Product $product, $amount = 1)
|
|
{
|
|
$this->order = $order;
|
|
$this->product = $product;
|
|
$this->offeredPrice = $product->getCurrentPrice();
|
|
}
|
|
}
|
|
|
|
|
|
Performance Considerations
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Using composite keys always comes with a performance hit compared to using entities with
|
|
a simple surrogate key. This performance impact is mostly due to additional PHP code that is
|
|
necessary to handle this kind of keys, most notably when using derived identifiers.
|
|
|
|
On the SQL side there is not much overhead as no additional or unexpected queries have to be
|
|
executed to manage entities with derived foreign keys.
|