Django_事務

 

介紹

函數說明

from django.db import transaction

transaction.atomic  # 原子性操做，把一系列操做當作一個總體，錯了則集體回退
transaction.on_commit(func，using = None)  # 在整個事件完成後，執行func函數

使用方法

from django.db import transaction

# atomic
@transaction.atomic
def index(request):
    ...

def index(request):
    with transation.atomic():
        ....
    ....


# on_commit
@transaction.atomic
def index(request):
    do_something...
    transation.oncommit(func)

 

示例

from django.db import models

class Account(models.Model):
    nid = models.IntegerField(primary_key=True)
    money = models.IntegerField(verbose_name="餘額")

models.py

from django.contrib import admin
from django.urls import path,re_path,include
from app01 import views

urlpatterns = [
    re_path("index.html",views.index)
]

urls.py

 

 一、正常狀況，轉帳成功

from django.shortcuts import render,HttpResponse
from app01 import models
from django.db.models import F

def index(request):
    models.Account.objects.filter(nid=1).update(money=F("money")-1)  # 帳號1給帳號2轉帳1元錢
    # raise IndexError
    models.Account.objects.filter(nid=2).update(money=F("money")+1)
    return HttpResponse("OK")

views.py

二、轉帳到一半出現錯誤

from django.shortcuts import render,HttpResponse
from app01 import models
from django.db.models import F

def index(request):
    models.Account.objects.filter(nid=1).update(money=F("money")-1)
    raise IndexError
    models.Account.objects.filter(nid=2).update(money=F("money")+1)
    return HttpResponse("OK")

views.py

三、還原全部money到1000，配置事務

from django.shortcuts import render,HttpResponse
from app01 import models
from django.db import transaction
from django.db.models import F


def index(request):
    with transaction.atomic():
        models.Account.objects.filter(nid=1).update(money=F("money")-1)
        raise IndexError
        models.Account.objects.filter(nid=2).update(money=F("money")+1)
    return HttpResponse("OK")

# 能夠使用裝飾器
# @transaction.atomic
# def index(request):
#     models.Account.objects.filter(nid=1).update(money=F("money")-1)
#     raise ValueError("出錯")
#     models.Account.objects.filter(nid=2).update(money=F("money")+1)
#     return HttpResponse("OK")

views.py

 四、驗證on_commit

說明：若是原子性操做出錯，則整個on_commit都不會執行，不管on_commit放在什麼位置。這與直接在該位置執行func是不同的。

from django.shortcuts import render,HttpResponse
from app01 import models
from django.db import transaction
from django.db.models import F


def before():
    print("before")
    # 能夠作一些特定工做，如發郵件、記錄log

def after():
    print("after")


@transaction.atomic
def index(request):
    transaction.on_commit(before)
    models.Account.objects.filter(nid=1).update(money=F("money")-1)
    # raise ValueError("出錯")
    models.Account.objects.filter(nid=2).update(money=F("money")+1)
    transaction.on_commit(after)
    return HttpResponse("OK")

views.py

from django.shortcuts import render,HttpResponse
from app01 import models
from django.db import transaction
from django.db.models import F


def before():
    print("before")
    # 能夠作一些特定工做，如發郵件、記錄log

def after():
    print("after")


@transaction.atomic
def index(request):
    transaction.on_commit(before)
    models.Account.objects.filter(nid=1).update(money=F("money")-1)
    raise ValueError("出錯")
    models.Account.objects.filter(nid=2).update(money=F("money")+1)
    transaction.on_commit(after)
    return HttpResponse("OK")

觸發錯誤，raise ValueError，未出現func的東西