Doctrine DQL - nested subqueries in WHERE clause throw Syntax Error - php

Question

I'm trying to query data from one table based on the SUMed and COALESCEd result of two associated tables.
The query works fine when executed as native SQL, unfortunately my application is restricted to only using Doctrine's DQL on a QueryBuilder object here.
This is how I build my QueryBuilder:
$resUnitQuery = $queryBuilder->getEntityManager()->createQueryBuilder();
$resUnitQuery->select('COALESCE(SUM(pc.residentialUnits), 0)')
->from(PropertyConnection::class, 'pc')
->where("$rootAlias.id = pc.contract");
$comUnitQuery = $queryBuilder->getEntityManager()->createQueryBuilder();
$comUnitQuery->select('COALESCE(SUM(pwa.residential_units), 0)')
->from(PropertyWithoutAddress::class, 'pwa')
->where("$rootAlias.id = pwa.contract");
$queryBuilder = $this->getEntityManager(Contract::class)->createQueryBuilder();
$queryBuilder
->select('id')
->from(Contract::class, 'o')
->andWhere(
':residentialUnits <= ' .
sprintf(
'((%s) + (%s))',
$resUnitQuery->getQuery()->getDQL(),
$comUnitQuery->getQuery()->getDQL()
)
)
->setParameter('residentialUnits', $params['rangeFrom']);
The generated DQL code is as follows:
SELECT id
FROM App\Entity\Contract o
WHERE :residentialUnits <= ((SELECT COALESCE(SUM(pc.residentialUnits), 0) FROM App\Entity\PropertyConnection pc WHERE o.id = pc.contract) + (SELECT COALESCE(SUM(pwa.residential_units), 0) FROM App\Entity\PropertyWithoutAddress pwa WHERE o.id = pwa.contract))
This results in the following error:
[Syntax Error] line 0, col 66: Error: Expected Literal, got 'SELECT'
I found an old Doctrine GitHub issue stating that double parenthetis can cause issues, which is why I skipped them in my WHERE clause and replaced
((%s) + (%s))
with
(%s) + (%s)
The surrounding parenthesis are required for native SQL to work, and it also results in an error from Doctrine:
[Syntax Error] line 0, col 174: Error: Expected end of string, got '+'
May I be running into restrictions of Doctrine's DQL here?
According to the docs, both SUM and COALESCE are supported, as well as nested queries.
Thanks a lot in advance,
Rene

Answer 1

Correct, the DBAL does not support arithmetic operations on subqueries. Additional the DBAL does not support joined subqueries, JOIN (SELECT FROM...) ON without using a native query.
Another issue is the WHERE statement of your subqueries, being dependant on the root query, will cause your root query to perform a full table scan. Executing each of the subqueries per-row, unless a criteria is added to the root query (WHERE o.id ...).
As the subquery SUM values are dependant on the root query id. You can rewrite the query to use a subquery as a hidden column and a HAVING clause, to filter the id result set from the added column results.
$em = $queryBuilder->getEntityManager();
$expr = $em->getExpressionBuilder();
$qbPC = $em->createQueryBuilder()
->select('COALESCE(SUM(pc.residentialUnits), 0)')
->from(App\Entity\PropertyConnection::class, 'pc')
->where($expr->eq('pc.contract', "$rootAlias.id"));
$qbPWA = $em->createQueryBuilder()
->select('COALESCE(SUM(pwa.residential_units), 0)')
->from(App\Entity\PropertyWithoutAddress::class, 'pwa')
->where($expr->eq('pwa.contract', "$rootAlias.id"));
$qb = $this->getEntityManager(Contract::class)
->createQueryBuilder()
->select('o.id')
->from(App\Entity\Contract::class, 'o')
->addSelect('(' . $qbPC->getDQL() . ') AS HIDDEN pc_ru')
->addSelect('(' . $qbPWA->getDQL() . ') AS HIDDEN pwa_ru')
->having($expr->lte(':v', 'pc_ru + pwa_ru'))
->setParameter('v', $params['rangeFrom']);
dump($qb->getDQL());
Resulting DQL
SELECT
o.id,
(SELECT
COALESCE(SUM(pc.residentialUnits), 0)
FROM App\Entity\PropertyConnection pc
WHERE pc.contract = o.id
) AS HIDDEN pc_ru,
(SELECT
COALESCE(SUM(pwa.residential_units), 0)
FROM App\Entity\PropertyWithoutAddress pwa
WHERE pwa.contract = o.id
) AS HIDDEN pwa_ru
FROM App\Entity\Contract o
HAVING :v <= pc_ru + pwa_ru