使用单个数据库表的Django模型继承 - 访问超类的子类时出现问题

我正在开发一个使用Oracle的Django应用程序，但不允许修改数据库模式。我有一个表，其中存在所有Thesis，它可以分为两个不相交的集合：PhdThesis和BscMscThesis。我也Review模型，其中链接到Thesis数据库表，并不在乎是否是PhdThesis或BscMscThesis，所以我想保留Thesis为abstract = False类。使用单个数据库表的Django模型继承 - 访问超类的子类时出现问题

class Thesis(models.Model): 
    # Primary key has to be specified explicite here for inheritance to work? 
    id = models.DecimalField(db_column="ID", max_digits=10, decimal_places=0, primary_key=True) 
    class Meta: 
     db_table = "DZ_PRACE_CERT" 
     managed = False 

class Person(models.Model): 
    class Meta: 
     db_table = "MV_OSOBY" 
     managed = False 


class BscMscThesisManager(models.Manager): 
    def get_query_set(self): 
     return super(BscMscThesisManager, self).get_query_set().filter(personbscmscdiploma__isnull=False) 

class BscMscThesis(Thesis): 
    # needed for inheritance? 
    thesis = models.OneToOneField(Thesis, db_column="ID", primary_key=True, parent_link=True) 
    authors = models.ManyToManyField(Person, through="PersonBscMscDiploma", related_name='author_of_bsc_msc_theses') 
    objects = BscMscThesisManager() 

    class Meta: 
     db_table = "DZ_PRACE_CERT" 
     managed = False 

class PersonBscMscDiploma(models.Model): 
    bsc_msc_thesis = models.ForeignKey(BscMscThesis, db_column="PRC_CERT_ID") 


class PhdThesisManager(models.Manager): 
    def get_query_set(self): 
     return super(PhdThesisManager, self).get_query_set().filter(personphddiploma__isnull=False) 

class PhdThesis(Thesis): 
    # needed for inheritance? 
    thesis = models.OneToOneField(Thesis, db_column="ID", primary_key=True, parent_link=True) 
    authors = models.ManyToManyField(Person, through="PersonPhdDiploma", related_name='author_of_phd_theses') 
    objects = PhdThesisManager() 

    class Meta: 
     db_table = "DZ_PRACE_CERT" 
     managed = False 

class PersonPhdDiploma(models.Model): 
    phd_thesis = models.ForeignKey(PhdThesis, db_column="PRC_CERT_ID")

我遇到的问题是：

>>> Thesis.objects.all()[0].phdthesis 
<PhdThesis: Uniwersytecki System Obsługi Studiów. Parametryzowane filtry> 
>>> Thesis.objects.all()[0].bscmscthesis 
<BscMscThesis: Uniwersytecki System Obsługi Studiów. Parametryzowane filtry> 
>>> Thesis.objects.all()[0].phdthesis.authors.all() 
[] 
>>> Thesis.objects.all()[0].bscmscthesis.authors.all() 
[<Person: Jan1912 Kowalski1912>] 
>>> Thesis.objects.all()[0].id 
Decimal('903') 
>>> BscMscThesis.objects.get(id=903) 
<BscMscThesis: Uniwersytecki System Obsługi Studiów. Parametryzowane filtry> 
>>> PhdThesis.objects.get(id=903) 
DoesNotExist: PhdThesis matching query does not exist.

PhdThesis.objects.all()和BscMscThesis.objects.all()回两个不相交集的预期。

为什么Thesis.objects.all()[0].phdthesis在上例中没有返回None或DoesNotExist？我能做些什么来获得这种行为？

来源

2011-07-20 mczers

Django似乎没有简单的方法来做到这一点。我结束了实施方法，如is_phd()和is_bsc_msc()并使用它们，如下所示：

def get_absolute_url(self): 
    if self.is_phd(): 
     return self.phdthesis.get_absolute_url() 
    else: 
     return self.bscmscthesis.get_absolute_url()

来源

2011-08-10 13:28:05 mczers

使用单个数据库表的Django模型继承 - 访问超类的子类时出现问题

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