85 lines
3.2 KiB
ReStructuredText
85 lines
3.2 KiB
ReStructuredText
Extra Lazy Associations
|
|
=======================
|
|
|
|
.. versionadded:: 2.1
|
|
|
|
In many cases associations between entities can get pretty large. Even in a simple scenario like a blog.
|
|
where posts can be commented, you always have to assume that a post draws hundreds of comments.
|
|
In Doctrine 2.0 if you accessed an association it would always get loaded completely into memory. This
|
|
can lead to pretty serious performance problems, if your associations contain several hundreds or thousands
|
|
of entities.
|
|
|
|
With Doctrine 2.1 a feature called **Extra Lazy** is introduced for associations. Associations
|
|
are marked as **Lazy** by default, which means the whole collection object for an association is populated
|
|
the first time its accessed. If you mark an association as extra lazy the following methods on collections
|
|
can be called without triggering a full load of the collection:
|
|
|
|
- ``Collection#contains($entity)``
|
|
- ``Collection#count()``
|
|
- ``Collection#slice($offset, $length = null)``
|
|
|
|
For each of this three methods the following semantics apply:
|
|
|
|
- For each call, if the Collection is not yet loaded, issue a straight SELECT statement against the database.
|
|
- For each call, if the collection is already loaded, fallback to the default functionality for lazy collections. No additional SELECT statements are executed.
|
|
|
|
Additionally even with Doctrine 2.0 the following methods do not trigger the collection load:
|
|
|
|
- ``Collection#add($entity)``
|
|
- ``Collection#offsetSet($key, $entity)`` - ArrayAccess with no specific key ``$coll[] = $entity``, it does
|
|
not work when setting specific keys like ``$coll[0] = $entity``.
|
|
|
|
With extra lazy collections you can now not only add entities to large collections but also paginate them
|
|
easily using a combination of ``count`` and ``slice``.
|
|
|
|
|
|
Enabling Extra-Lazy Associations
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The mapping configuration is simple. Instead of using the default value of ``fetch="LAZY"`` you have to
|
|
switch to extra lazy as shown in these examples:
|
|
|
|
.. configuration-block::
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
namespace Doctrine\Tests\Models\CMS;
|
|
|
|
/**
|
|
* @Entity
|
|
*/
|
|
class CmsGroup
|
|
{
|
|
/**
|
|
* @ManyToMany(targetEntity="CmsUser", mappedBy="groups", fetch="EXTRA_LAZY")
|
|
*/
|
|
public $users;
|
|
}
|
|
|
|
.. 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="Doctrine\Tests\Models\CMS\CmsGroup">
|
|
<!-- ... -->
|
|
<many-to-many field="users" target-entity="CmsUser" mapped-by="groups" fetch="EXTRA_LAZY" />
|
|
</entity>
|
|
</doctrine-mapping>
|
|
|
|
.. code-block:: yaml
|
|
|
|
Doctrine\Tests\Models\CMS\CmsGroup:
|
|
type: entity
|
|
# ...
|
|
manyToMany:
|
|
users:
|
|
targetEntity: CmsUser
|
|
mappedBy: groups
|
|
fetch: EXTRA_LAZY
|
|
|