你真的用到Django中的事务了吗？

最新推荐文章于 2025-04-22 21:00:12 发布

原创最新推荐文章于 2025-04-22 21:00:12 发布 · 423 阅读

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#django #python #后端

这篇博客讨论了Django中事务管理的问题，指出在一段代码中，由于没有正确使用事务，导致了在新增操作失败时删除操作仍然执行，违反了事务的原子性和一致性。Django默认支持事务，但在这里需要显式使用`@transaction.atomic()`装饰器或`with transaction.atomic():`来包裹多条数据库操作。文章提供了优化后的代码示例，展示了如何通过事务确保所有操作要么全部成功，要么全部回滚，从而维护数据的完整性。

答案是肯定的，Django中默认支持事务。
那就意味着，一段代码:

from django.db import transaction
class UpdatePlan(APIView):
    # authentication_classes = []

    @transaction.atomic()
    def post(self, request):
        plan_id = request.data.get("plan_id", None)
        resultList = request.data.get("busizArray", [])
        attentions = request.data.get("attentions", None)
        if not check_params_ok(plan_id):
            return Response({"detail": "params lose"}, status=status.HTTP_202_ACCEPTED)
        if not resultList:
            return Response({"detail": "方案不能为空"}, status=status.HTTP_202_ACCEPTED)

        try:
            all_treatment = CareTreatment.objects.filter(plan_id=plan_id)
            all_treatment.delete()
            cp = CarePlan.objects.get(id=plan_id)
            for i in resultList:
                homeList=i.get('home')
                for k in range(0,len(homeList)):
                    caredicts = homeList[k].get('home_care')
                    for caredict in caredicts:
                        goods = PlanGoods.objects.get(id=caredict.get('product_item_id'))

                        CareTreatment.objects.create(
                            goods=goods,
                            usage_tag=caredict.get('giftRemark'),
                            plan_id=cp,
                            order=caredict.get('order'),
                            plan=str(i.get("name"))+"方案",
                            group=k+1
                        )
                    advice = homeList[k].get('advice')
                    advice_id = advice["id"]
                    advice = advice["advice"]
                    if advice_id is not None:
                        cpa_ = CarePlanAdvices.objects.get(id=advice_id)
                        cpa_.advice = advice
                        cpa_.save()

                    if advice is not None:
                        CarePlanAdvices.objects.create(plan=str(i.get("name"))+"方案", plan_id=cp, group=k+1, advice=advice)
        except Exception as e:
            print(e)
            result = {"detail": "提交院护方案失败"}
            return Response(result,status=status.HTTP_202_ACCEPTED)

这段代码的核心部分包括删除和新增 CareTreatment这张表数据, 两部分操作。

事实上，遇到一个问题，在新增报错的情况下，会导致删除成功，而新增没有成功。

那么这就不是一个合格的事务，至少是违反了原子性和一致性两大特点。

Django默认支持的事务去哪了呢？

Django默认是支持事务，Django 如何显示的使用事务呢？

有三种方法:

装饰器的用法

from django.db import transaction

@transaction.atomic
def post(request):
    pass
    # 事务的代码

with语句的用法

from django.db import transaction

def post(request):

  with transaction.atomic():
        pass
        # 事务的代码

保存点的用法

from django.db import transaction

# 创建保存点
save_id = transaction.savepoint()  
# 回滚
transaction.savepoint_rollback(save_id)
# 提交
transaction.savepoint_commit(save_id)

其实我们可以理解django默认支持的事务是第一种形式的。

Django也没想到我们在实现View的时候居然有多重的操作。

所以我们需要用后两种形式对我们多重操作的自定义事务。

第二种形式优化后:

class UpdatePlan(APIView):

    def post(self, request):
        plan_id = request.data.get("plan_id", None)
        resultList = request.data.get("busizArray", [])
        attentions = request.data.get("attentions", None)
        if not check_params_ok(plan_id):
            return Response({"detail": "params lose"}, status=status.HTTP_202_ACCEPTED)
        if not resultList:
            return Response({"detail": "方案不能为空"}, status=status.HTTP_202_ACCEPTED)

        try:
            with transaction.atomic():
                all_treatment = CareTreatment.objects.filter(plan_id=plan_id)
                all_treatment.delete()
                cp = CarePlan.objects.get(id=plan_id)
                for i in resultList:
                    homeList=i.get('home')
                    for k in range(0,len(homeList)):
                        caredicts = homeList[k].get('home_care')
                        for caredict in caredicts:
                            goods = PlanGoods.objects.get(id=caredict.get('product_item_id'))

                            CareTreatment.objects.create(
                                goods=goods,
                                usage_tag=caredict.get('giftRemark'),
                                plan_id=cp,
                                order=caredict.get('order'),
                                plan=str(i.get("name"))+"方案",
                                group=k+1
                            )
                        advice = homeList[k].get('advice')
                        advice_id = advice["id"]
                        advice = advice["advice"]
                        if advice_id is not None:
                            cpa_ = CarePlanAdvices.objects.get(id=advice_id)
                            cpa_.advice = advice
                            cpa_.save()

                        if advice is not None:
                            CarePlanAdvices.objects.create(plan=str(i.get("name"))+"方案", plan_id=cp, group=k+1, advice=advice)
        except Exception as e:
            print(e)
            result = {"detail": "提交院护方案失败"}
            return Response(result,status=status.HTTP_202_ACCEPTED)

第三种形式优化后:

class UpdatePlan(APIView):

    def post(self, request):
        plan_id = request.data.get("plan_id", None)
        resultList = request.data.get("busizArray", [])
        attentions = request.data.get("attentions", None)
        if not check_params_ok(plan_id):
            return Response({"detail": "params lose"}, status=status.HTTP_202_ACCEPTED)
        if not resultList:
            return Response({"detail": "方案不能为空"}, status=status.HTTP_202_ACCEPTED)

        save_id = transaction.savepoint()
        try:
            all_treatment = CareTreatment.objects.filter(plan_id=plan_id)
            all_treatment.delete()
            cp = CarePlan.objects.get(id=plan_id)
            for i in resultList:
                homeList=i.get('home')
                for k in range(0,len(homeList)):
                    caredicts = homeList[k].get('home_care')
                    for caredict in caredicts:
                        goods = PlanGoods.objects.get(id=caredict.get('product_item_id'))

                        CareTreatment.objects.create(
                            goods=goods,
                            usage_tag=caredict.get('giftRemark'),
                            plan_id=cp,
                            order=caredict.get('order'),
                            plan=str(i.get("name"))+"方案",
                            group=k+1
                        )
                    advice = homeList[k].get('advice')
                    advice_id = advice["id"]
                    advice = advice["advice"]
                    if advice_id is not None:
                        cpa_ = CarePlanAdvices.objects.get(id=advice_id)
                        cpa_.advice = advice
                        cpa_.save()

                    if advice is not None:
                        CarePlanAdvices.objects.create(plan=str(i.get("name"))+"方案", plan_id=cp, group=k+1, advice=advice)
            transaction.savepoint_commit(save_id)
        except Exception as e:
            print(e)
            transaction.savepoint_rollback(save_id)
            result = {"detail": "提交院护方案失败"}
            return Response(result,status=status.HTTP_202_ACCEPTED)