[英]Working with composite primary key in django project with legacy database
[英]django admin site returns MultipleObjectsReturned exception with inspectdb imported legacy database and composite primary key
使用 inspectdb,我在 django 中導入了一個遺留數據庫,其中包含具有復合主鍵的實體。數據庫模式包含大約 200 個不同的實體,inspectdb 在這種情況下非常方便。
這是 mysql 中的架構:
CREATE TABLE `mymodel` (
`id` bigint(20) unsigned NOT NULL DEFAULT '0',
`siteid` bigint(20) unsigned NOT NULL DEFAULT '0',
...
PRIMARY KEY (`siteid`,`id`),
...
在 django 中自動生成 model(使用 python manager.py inspectdb 導入)
class Mymodel(models.Model):
id = models.PositiveBigIntegerField()
siteid = models.PositiveBigIntegerField(primary_key=True)
...
class Meta:
managed = False
db_table = 'mymodel'
unique_together = (('siteid', 'id'),
我已經使用以下方法在管理站點中注冊了所有模型:
from django.contrib import admin
from django.apps import apps
app = apps.get_app_config('appname')
for model_name, model in app.models.items():
admin.site.register(model)
完成所有工作后,我導航到管理站點並單擊“mymodel”部分中的任意 object,將返回以下異常:
appname.models.Content.MultipleObjectsReturned: get() returned more than one Mymodel-- it returned more than 20!
顯然,(至少在我看來是這樣)管理員正在使用 siteid 獲取 object,但它應該使用 Meta class 中的 unique_together。
關於如何通過一般配置解決此問題並讓管理站點模塊使用 unique_together 進行查詢的任何建議?
是的,你可以解決這個問題,但你付出了更多的努力。
首先你將 model-admin class 分離為 model Mymodel並自定義 model-admin class 方法:
由於 django admin build 在ChangeList class 中更改了 url,因此我們可以像 MymodelChangelist 一樣創建自定義Changelist class並將id
字段值作為查詢參數傳遞。 我們將使用id
字段值來獲取 object。
覆蓋get_object()方法以使用自定義查詢從查詢集中獲取 object
覆蓋 model-admin 的get_changelist()方法以設置您的自定義更改列表class
覆蓋save_model()方法以顯式保存 object。
管理員.py
class MymodelChangelist(ChangeList):
# override changelist class
def url_for_result(self, result):
id = getattr(result, 'id')
pk = getattr(result, self.pk_attname)
url = reverse('admin:%s_%s_change' % (self.opts.app_label,
self.opts.model_name),
args=(quote(pk),),
current_app=self.model_admin.admin_site.name)
# Added `id` as query params to filter queryset to get unique object
url = url + "?id=" + str(id)
return url
@admin.register(Mymodel)
class MymodelAdmin(admin.ModelAdmin):
list_display = [
'id', 'siteid', 'other_model_fields'
]
def get_changelist(self, request, **kwargs):
"""
Return the ChangeList class for use on the changelist page.
"""
return MymodelChangelist
def get_object(self, request, object_id, from_field=None):
"""
Return an instance matching the field and value provided, the primary
key is used if no field is provided. Return ``None`` if no match is
found or the object_id fails validation.
"""
queryset = self.get_queryset(request)
model = queryset.model
field = model._meta.pk if from_field is None else model._meta.get_field(from_field)
try:
object_id = field.to_python(object_id)
# get id field value from query params
id = request.GET.get('id')
return queryset.get(**{'id': id, 'siteid': object_id})
except (model.DoesNotExist, ValidationError, ValueError):
return None
def save_model(self, request, obj, form, change):
cleaned_data = form.cleaned_data
if change:
id = cleaned_data.get('id')
siteid = cleaned_data.get('siteid')
other_fields = cleaned_data.get('other_fields')
self.model.objects.filter(id=id, siteid=siteid).update(other_fields=other_fields)
else:
obj.save()
現在您可以更新任何對象並添加新的 object。但是,在另外一種情況下,您無法siteid which is already added because of primary key validation
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