[DDC-2891] Impossible to pass a limit to a subquery Created: 07/Jan/14  Updated: 08/Jan/14

Status: Open
Project: Doctrine 2 - ORM
Component/s: None
Affects Version/s: 2.4.2
Fix Version/s: None
Security Level: All

Type: Improvement Priority: Major
Reporter: alex Assignee: Benjamin Eberlei
Resolution: Unresolved Votes: 0
Labels: None


 Description   

It seems that passing the limit to a subquery is not working

 
$subquery = $em->createQueryBuilder()->from('...')->where('...')->setMaxResults(5);
$query = $em->createQueryBuilder()->from('...')->where(
   $qb->expr()->in('p.id', $subquery->getDQL())
);
$query->getQuery()->getResult();

The query works but the is no specified limit in the resulting SQL.
I am aware that DQL does not support the limits and offsets, so i guess there should be another way to get this working?



 Comments   
Comment by Steve Müller [ 08/Jan/14 ]

Can you please tell which database platform you are using? Because limiting results heavily depends on the platform used.

Comment by alex [ 08/Jan/14 ]

MySql

Comment by Steve Müller [ 08/Jan/14 ]

Hmmm I am not quite sure if the limit/offset is invoked for subqueries but I don't see why it shouldn't. Also I think this is not a DBAL issue because the limit/offset support for MySQL is the easiest we have on all platform. See: https://github.com/doctrine/dbal/blob/master/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php#L51-L63
The query doesn't have to be modified but instead only the limit clause is appended to the query. Can you maybe provide the generated SQL for that query?

Comment by alex [ 08/Jan/14 ]

I think if you try to build any query with QueryBuilder, set a limit to it with setMaxResults then call getDQL method, you should see that the output contains no info about limit.
So if you look at my code example , at $qb->expr()>in('p.id', $subquery>getDQL()), then you will see that the getDQL passes to the IN expression a query which already DOES NOT have limit. So this is the place where any info about limits and offsets gets lost.

So I fail to see what it has to do with any specific db engine,however I can provide the mysql resulting query if you want,though it looked perfectly normal to me,just lacks the LIMIT part.

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