Doctrine QueryBuilder groupBy relation not working - php

Question

I have the following query:
$query = $qb->select('p')
->from(get_class($page), 'p')
->innerJoin('p1.translations', 't')
->groupBy('p.id')
->addGroupBy('t.id')
->getQuery();
Doctrine returns the above like:
Page entity -> [translation 1, translation 2, translation 3]
But I want the result like:
Page entity 1 -> translation 1
Page entity 1 -> translation 2
Page entity 1 -> translation 3
Does anyone know how I can do this? I want to return a list of entities.

Answer 1

First of all, both groupBy are completely superfluous, assuming both id fields you are grouping by are the primary keys of their respective tables. For any given (p.id, t.id) combination there will only be at most one result, whether you are grouping or not.
Second, even though you are joining the the translations table, you are not fetching any data from it (t is absent from your ->select()). It just appears that way since doctrine "magically" loads the data in the background when you call $page->getTranslations() (assuming your getter is called that way).
Third, your issue isn't with the groupBy. You are completely misunderstanding what an ORM actually does when hydrating a query result. The SQL query that doctrine generates from your code will actually return results in a fashion just like you expect, with "Page entity 1" repeated multiple times.
However, now comes the hydration step. Doctrine reads the first result row, builds a "Page entity 1" and a "Translation 1" entity, links them and adds them to it's internal entity registry. Then, for the second result, Doctrine notices that it has already hydrated the "Page entity 1" object and (this is the crucial part!) reuses the same object from the first row, adding the second translation to the ->translation collection of the existing object. Even if you read the "Page entity 1" again in a completely different query later in your code, you still get the same PHP object again.
This behaviour is at the core of what Doctrine does. Basically, any table row in the database will always be mirrored by a single object on the PHP side, no matter how often or in what way you actually read it from the database.
To summarize, your query should look like this:
$query = $qb->select('p, t')
->from(get_class($page), 'p')
->innerJoin('p.translations', 't')
->getQuery();
If you really need to iterate over all (p, t) combinations, do so with nested loops:
foreach ($query->getResult() as $p) {
foreach ($p->getTranslations() as $t) {
// do something
}
}
EDIT: If your relationship is bidirectional, you could also turn your query around:
$query = $qb->select('t, p')
->from('My\Bundle\Entity\Translation', 't')
->innerJoin('t.page', 'p')
->getQuery();
Now in your example you actually get 3 results that you can iterate over in a single foreach(). You would still only get a single "Page entity 1" object, with all the translations in the query result pointing to it.