42 lines
1.5 KiB
ReStructuredText
42 lines
1.5 KiB
ReStructuredText
Pagination
|
|
==========
|
|
|
|
Starting with version 2.2 Doctrine ships with a Paginator for DQL queries. It
|
|
has a very simple API and implements the SPL interfaces ``Countable`` and
|
|
``IteratorAggregate``.
|
|
|
|
.. code-block:: php
|
|
|
|
<?php
|
|
use Doctrine\ORM\Tools\Pagination\Paginator;
|
|
|
|
$dql = "SELECT p, c FROM BlogPost p JOIN p.comments c";
|
|
$query = $entityManager->createQuery($dql)
|
|
->setFirstResult(0)
|
|
->setMaxResults(100);
|
|
|
|
$paginator = new Paginator($query, $fetchJoinCollection = true);
|
|
|
|
$c = count($paginator);
|
|
foreach ($paginator as $post) {
|
|
echo $post->getHeadline() . "\n";
|
|
}
|
|
|
|
Paginating Doctrine queries is not as simple as you might think in the
|
|
beginning. If you have complex fetch-join scenarios with one-to-many or
|
|
many-to-many associations using the "default" LIMIT functionality of database
|
|
vendors is not sufficient to get the correct results.
|
|
|
|
By default the pagination extension does the following steps to compute the
|
|
correct result:
|
|
|
|
- Perform a Count query using `DISTINCT` keyword.
|
|
- Perform a Limit Subquery with `DISTINCT` to find all ids of the entity in from on the current page.
|
|
- Perform a WHERE IN query to get all results for the current page.
|
|
|
|
This behavior is only necessary if you actually fetch join a to-many
|
|
collection. You can disable this behavior by setting the
|
|
``$fetchJoinCollection`` flag to ``false``; in that case only 2 instead of the 3 queries
|
|
described are executed. We hope to automate the detection for this in
|
|
the future.
|