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