Django get queryset在非托管数据库上失败

Question

我正在尝试在只读数据库上使用Django的ORM。

下面是使用的模型:

class Languages(models.Model):
idlanguage = models.IntegerField(primary_key=True)
language = models.CharField(max_length=50)
code = models.CharField(max_length=50)
class Meta:
managed = False
db_table = 'languages'

settings.py文件中数据库部分的配置:

DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql',
'NAME': 'XXXXXXX',
'USER': 'XXX',
'PASSWORD': 'XXXXXXXXXXXXXXXXXXXXX',
'HOST': '',
'PORT': '',
},
'ro_bdd': {
'ENGINE': 'django.db.backends.oracle',
'NAME': 'XXXXX',
'USER': 'XXXXXXXXXX',
'PASSWORD': 'XXXXX',
'HOST': 'XXXXXXXXX',
'PORT': 'XXXX',
}
}

和查询集:

In [1]: Languages.objects.all().using("ro_bdd")
Out[1]: <QuerySet [<Languages: Languages object (1)>]>
In [2]: Languages.objects.filter(idlanguage=1).using("ro_bdd")
Out[2]: <QuerySet [<Languages: Languages object (1)>]>
In [3]: Languages.objects.get(idlanguage=1).using("ro_bdd")

/....../python3.9/site-packages/django/db/backends/utils.py in _execute(self, sql, params, *ignored_wrapper_args)
82                 return self.cursor.execute(sql)
83             else:
---> 84                 return self.cursor.execute(sql, params)
85
86     def _executemany(self, sql, param_list, *ignored_wrapper_args):
ProgrammingError: ERROR:  relation « languages » does not exist
LINE 1: ..., "languages"."language", "languages"."code" FROM "languages...
^

价值观:

'sql' => SELECT "languages"."idlanguage", "languages"."language", "languages"."code" FROM "languages" WHERE "languages"."idlanguage" = %s LIMIT 21
'params' => (1,)

为什么get查询集不工作?

Answer 1

你应该把.using()放在前面，因为.get()解析很急切，然后它就"太迟了"，所以:

Languages.objects.using('ro_bdd').get(idlanguage=1)

模型对象也没有.using()，所以如果.get()成功，最终会导致类型错误。