我有三种型号
class Customer(models.Model):
created = models.DateTimeField(auto_now_add=True)
# some other fields, which don't matter
class ActivityStatus(models.Model):
created = models.DateTimeField(auto_now_add=True)
name = models.CharField(max_length=5)
class Activities(models.Model):
created = models.DateTimeField(auto_now_add=True)
status = models.ForeignKey(ActivityStatus)
planned_execution_date = models.DateField()
我也有两个管理员
class CustomerAdmin(admin.ModelAdmin):
fields = () # doesn't matter really
list_display() # doesn't matter really
class ActivityAdmin(admin.ModelAdmin):
fields = () # doesn't matter really
list_display() # doesn't matter really
我想添加自定义字段(last_activity_planned_date),以便在CustomerAdmin的changelist_view上显示和排序。条件如下: -仅显示客户最近一次活动的计划执行日期,但前提是该活动的状态为status_id =2。否则不显示任何内容
示例1
客户1有2个活动-最近的一个活动的status_id = 2,planned_execution_date = 2017-09-17
changelist_view:
| id | last_activity_planned_date |
| 1 | 2017-09-17 |
示例2
客户1有2个活动-最新活动的status_id = 3,planned_execution_date = 2017-09-27
| id | last_activity_planned_date |
| 1 | null |
答案 0 :(得分:1)
使用this anwer我设法找到了解决方法
from django.db.models.expressions import Subquery, OuterRef
ACTIVITY_STATUS_NEW = 2
def get_queryset(self, request):
queryset = super().get_queryset(request)
activities_per_customer = Activities.objects.filter(customer_id=OuterRef('pk'))
latest_activity_per_customer = (activities_per_customer.order_by('pk', '-created')).distinct('pk')
latest_active_activity_per_customer =(latest_activity_per_customer.filter(status_id=ACTIVITY_STATUS_NEW))
queryset = queryset.annotate(_last_activity_planned_date=Subquery(latest_active_activity_per_customer.values('planned_execution_date')[:1]),)
return queryset
然后
list_display = ('id', 'last_activity_planned_date')
def last_activity_planned_date(self, obj):
return obj._last_activity_planned_date
last_activity_planned_date.short_description = "Optional description"
答案 1 :(得分:0)
您可以添加custom fields in list_display
:
class CustomerAdmin(admin.ModelAdmin):
fields = ()
list_display = ('last_activity_planned_date',)
def last_activity_planned_date(self, obj):
latest_activity = obj.activities.order_by('-planned_execution_date').first()
if latest_activity and latest_activity.status_id == 2:
return latest_activity.planned_execution_date
else:
return None
但是,要使此列可排序将非常复杂。即使在原始SQL中,它似乎也很复杂。在Django 2.1中,在admin_order_field
中添加了对查询表达式的支持,但是我仍然想不出一个像样的SQL查询来实现这种排序。
一种解决方案是将这些信息复制到Customer.last_activity_planned_date
字段中(使用db_index=True
来提高订购性能)。
如果您可以提供仅定期更新的信息,则可以设置cronjob以每1500万,1小时或1天(根据您的需要和进行更新所需的资源)对其进行更新。
如果您需要始终准确无误地获取此信息,则每次创建,更新或删除Activities
条目时都必须对其进行更新。根据您的需要,有多种方法可以执行此操作,包括SQL triggers和Django signals。效果很好,但不能百分百确定,因此,即使您使用此解决方案,我也建议您设置每日cronjob以确保所有数据都是一致的。