ApiPlatform\Core\Bridge\Doctrine\Orm\Extension\EagerLoadingExtension::joinRelations PHP Method

    private function joinRelations(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $queryNameGenerator, string $resourceClass, bool $forceEager, string $parentAlias, array $propertyMetadataOptions = [], bool $wasLeftJoin = false, int &$joinCount = 0)
    {
        if ($joinCount > $this->maxJoins) {
            throw new RuntimeException('The total number of joined relations has exceeded the specified maximum. Raise the limit if necessary.');
        }
        $entityManager = $queryBuilder->getEntityManager();
        $classMetadata = $entityManager->getClassMetadata($resourceClass);
        foreach ($classMetadata->associationMappings as $association => $mapping) {
            try {
                $propertyMetadata = $this->propertyMetadataFactory->create($resourceClass, $association, $propertyMetadataOptions);
            } catch (PropertyNotFoundException $propertyNotFoundException) {
                //skip properties not found
                continue;
            } catch (ResourceClassNotFoundException $resourceClassNotFoundException) {
                //skip associations that are not resource classes
                continue;
            }
            if (false === $forceEager && ClassMetadataInfo::FETCH_EAGER !== $mapping['fetch']) {
                continue;
            }
            if (false === $propertyMetadata->isReadableLink() || false === $propertyMetadata->isReadable()) {
                continue;
            }
            $isNullable = $mapping['joinColumns'][0]['nullable'] ?? true;
            if (false !== $wasLeftJoin || true === $isNullable) {
                $method = 'leftJoin';
            } else {
                $method = 'innerJoin';
            }
            $associationAlias = $queryNameGenerator->generateJoinAlias($association);
            $queryBuilder->{$method}(sprintf('%s.%s', $parentAlias, $association), $associationAlias);
            ++$joinCount;
            try {
                $this->addSelect($queryBuilder, $mapping['targetEntity'], $associationAlias, $propertyMetadataOptions);
            } catch (ResourceClassNotFoundException $resourceClassNotFoundException) {
                continue;
            }
            $this->joinRelations($queryBuilder, $queryNameGenerator, $mapping['targetEntity'], $forceEager, $associationAlias, $propertyMetadataOptions, $method === 'leftJoin', $joinCount);
        }
    }