Django 过滤相关对象的聚合

我试图通过相关对象的特征来计算符合条件和组的对象。例如，如果我有一组这样的模型：

class Office(User):
    name = models.CharField(max_length=50)
    city = models.CharField(max_length=50)

class Staff(User):
    home_office = models.ForeignKey(Office)

class Appointment(models.Model):
    appt_start = models.DateTimeField()
    appt_end = models.DateTimeField()
    client = models.ForeignKey(User)
    provider = models.ForeignKey(Staff)
    result = models.CharField(max_length=50)

SELECT office.name, COUNT(appointment.id)
    FROM appointment
        JOIN staff ON staff.id = appointment.provider_id
        JOIN office ON office.id = staff.home_office_id
    WHERE appointment.result = 'success' GROUP BY office.name;

我想获得每个办公室成功的预约次数，我可以执行一个原始SQL查询，如下所示：

class Office(User):
    name = models.CharField(max_length=50)
    city = models.CharField(max_length=50)

class Staff(User):
    home_office = models.ForeignKey(Office)

class Appointment(models.Model):
    appt_start = models.DateTimeField()
    appt_end = models.DateTimeField()
    client = models.ForeignKey(User)
    provider = models.ForeignKey(Staff)
    result = models.CharField(max_length=50)

SELECT office.name, COUNT(appointment.id)
    FROM appointment
        JOIN staff ON staff.id = appointment.provider_id
        JOIN office ON office.id = staff.home_office_id
    WHERE appointment.result = 'success' GROUP BY office.name;

如果可能的话，我更愿意使用ORM和Django的QuerySet聚合和注释函数得到这个结果，但是在阅读了文档之后，我认为不可能基于相关对象的字段进行聚合，但我想问一下，万一我遗漏了什么。

这个怎么样：

Office.objects.filter(
    staff__appointment__result='success'
).values('name').annotate(appointments=models.Count('staff__appointment'))