TYPO3 Core

Extbases DataMapper resolves relations to other entities. 1:n relations usually store a relation count on the parent, so whenever it shows 0, it wouldn't be necessary to try to fetch relations. This saves 1 query per relation but in certain scenarios with many entities and relations this saves tons of superfluous db operations.

protected function fetchRelatedEager(DomainObjectInterface $parentObject, $propertyName, $fieldValue = '')
{
    return $fieldValue === '' ? $this->getEmptyRelationValue($parentObject, $propertyName) : $this->getNonEmptyRelationValue($parentObject, $propertyName, $fieldValue);
}

This method already tries to be smart but it only sees empty strings as empty relation value.

Proposal: Expect the $fieldValue to hold an integer, cast other types to int and evaluate if said int is 0. https://3v4l.org/mqsvQ