protected function findExistingRelationIds($checkIds = null)
    {
        $foreignKeyName = $this->relationModel->getQualifiedKeyName();

        $results = $this->relationObject
            ->getBaseQuery()
            ->select($foreignKeyName);

        if ($checkIds !== null && is_array($checkIds) && count($checkIds)) {
            $results = $results->whereIn($foreignKeyName, $checkIds);
        }

        return $results->lists($foreignKeyName);
    }