Ordering To-Many Associations

There are use-cases when you'll want to sort collections when they are retrieved from the database. In userland you do this as long as you haven't initially saved an entity with its associations into the database. To retrieve a sorted collection from the database you can use the #[OrderBy] attribute with a collection that specifies a DQL snippet that is appended to all queries with this collection.

Additional to any #[OneToMany] or #[ManyToMany] attribute you can specify the #[OrderBy] in the following way:

.. configuration-block::

.. code-block:: attribute

    <?php
    #[Entity]
    class User
    {
        // ...

        #[ManyToMany(targetEntity: Group::class)]
        #[OrderBy(['name' => 'ASC', 'createdAt' => 'DESC'])]
        private Collection $groups;
    }

.. code-block:: xml

    <doctrine-mapping>
        <entity name="User">
            <many-to-many field="groups" target-entity="Group">
                <order-by>
                    <order-by-field name="name" direction="ASC" />
                    <order-by-field name="createdAt" direction="DESC" />
                </order-by>
            </many-to-many>
        </entity>
    </doctrine-mapping>

The DQL Snippet representing the field is only allowed to consist of unqualified, unquoted field names. The direction can be either ASC or DESC and is mandatory when using attributes, but optional when using XML. When using the XML driver, the direction defaults to ASC if not specified.

The referenced field names have to exist on the targetEntity class of the #[ManyToMany] or #[OneToMany] attribute.

The semantics of this feature can be described as follows:

@OrderBy acts as an implicit ORDER BY clause for the given fields, that is appended to all the explicitly given ORDER BY items.
All collections of the ordered type are always retrieved in an ordered fashion.
To keep the database impact low, these implicit ORDER BY items are only added to a DQL Query if the collection is fetch joined in the DQL query.

Given our previously defined example, the following would not add ORDER BY, since g is not fetch joined:

.. code-block:: sql

SELECT u FROM User u JOIN u.groups g WHERE SIZE(g) > 10

However the following:

.. code-block:: sql

SELECT u, g FROM User u JOIN u.groups g WHERE u.id = 10

...would internally be rewritten to:

.. code-block:: sql

SELECT u, g FROM User u JOIN u.groups g WHERE u.id = 10 ORDER BY g.name ASC

You can reverse the order with an explicit DQL ORDER BY:

.. code-block:: sql

SELECT u, g FROM User u JOIN u.groups g WHERE u.id = 10 ORDER BY g.name DESC

...is internally rewritten to:

.. code-block:: sql

SELECT u, g FROM User u JOIN u.groups g WHERE u.id = 10 ORDER BY g.name DESC, g.name ASC