How to use "distinct on" with doctrine? - php

Question

I try to use "distinct on" with doctrine but I get the following error:
Error: Expected known function, got 'on'
class Report extends EntityRepository
{
public function findForList() {
$queryBuilder = $this->createQueryBuilder('r');
$queryBuilder->select('distinct on (r.parentId)')
->orderBy('r.parentId')
->orderBy('r.date', 'DESC');
return $queryBuilder->getQuery()->getResult();
}
}
How could I implement the following query?
select distinct on (r.parent_id)
r.parent_id,
r.id,
r.name
from frontend.report r
order by r.parent_id, r.date desc;
Apparently it doesn't seem possible to do this with the query builder. I tried to rewrite my query in different ways:
select * from frontend.report r
where
r.id in (
select distinct
(select r3.id from frontend.report r3
where r3.parent_id = r.parent_id
order by r3.date desc limit 1) AS id
from frontend.report r2);
But doctrine doesn't support LIMIT:
public function findForList() {
$qb3 = $this->_em->createQueryBuilder();
$qb3->select('r3.id')
->from('MyBundle:frontend\report', 'r3')
->where('r3.parentId = r2.parentId')
->orderBy('r3.date', 'DESC')
//->setMaxResults(1)
;
$qb2 = $this->_em->createQueryBuilder();
$qb2->select('(' . $qb3->getDql() . ' LIMIT 1)')
->from('MyBundle:frontend\report', 'r2')
->distinct(); // groupBy('r2.parentId')
$queryBuilder = $this->createQueryBuilder('r');
$queryBuilder->where(
$queryBuilder->expr()->in('rlt.id', $qb2->getDql())
);
return $queryBuilder->getQuery()->getResult();
}
I think the only solution is to use native SQL queries.

Answer 1

This response is for someone that yet looking for the solution in similar cases.
If you need a sample "DISTINCT" you can use:
$queryBuinder->select('parentId')
->distinct('parentId');
but if you want a "DISTINCT ON" you should use Native SQL instead of Query Builder, check out the manual here: Doctrine Native SQL

Answer 2

Just remove the on word :
$queryBuilder->select('distinct r.parentId')
->orderBy('r.parentId')
->orderBy('r.date', 'DESC');