在Django出现异常时回滚一组数据库事务

Question

首先，this GitHub project包含我在本文中讨论和询问的代码。这是一个非专有和简短的例子，我的团队正在处理这些事情。

我正在研究一个项目，我们使用Django数据库事务在表格上进行更新，以准备转换为可用于业务目的的XML。我们通过使用transaction.atomic()上下文管理器来确定错误得到正确处理，从而修复了以前破坏的代码。每个UPDATE语句都位于一个上下文管理器中，而上下文管理器又位于一个函数中。有三个在程序中调用另一个函数（bulk_set()）内的这些功能（set_yes()，set_no()和broken_query()）：

models.py

from __future__ import unicode_literals 
from django.db import connection, DatabaseError, transaction 
import pandas as pd 

from django.db import models 


class TestTable(models.Model): 
    value1 = models.IntegerField() 
    value2 = models.IntegerField() 
    same = models.CharField(max_length=3, null=True) 


def setup_table(): 
    """ 
    sets up the basic table. 
    several rows will have matching values, some won't. 
    :return: None 
    """ 
    row1 = TestTable(value1=1, value2=1) 
    row1.save() 

    row2 = TestTable(value1=2, value2=1) 
    row2.save() 

    row3 = TestTable(value1=56, value2=1) 
    row3.save() 

    row4 = TestTable(value1=10, value2=10) 
    row4.save() 


def set_yes(): 
    """ 
    sets "same" column on rows with matching value1 and value2 columns to "yes" 
    :return: None 
    """ 
    query = ''' 
     UPDATE db_app_testtable 
     SET same = 'yes' 
     WHERE value1 = value2 
    ''' 
    try: 
     with transaction.atomic(): 
      cursor = connection.cursor() 
      cursor.execute(query) 
    except DatabaseError as ex: 
     print "set_yes has error %s" % (ex) 
     raise 
    finally: 
     cursor.close() 
     print_table() 


def set_no(): 
    """ 
    sets "same" column on rows with differing value1 and value2 columns to "no" 
    :return: None 
    """ 
    query = ''' 
     UPDATE db_app_testtable 
     SET same = 'no' 
     WHERE value1 != value2 
    ''' 
    try: 
     with transaction.atomic(): 
      cursor = connection.cursor() 
      cursor.execute(query) 
    except DatabaseError as ex: 
     print "set_no has error %s" % (ex) 
     raise 
    finally: 
     cursor.close() 
     print_table() 


def broken_query(): 
    """ 
    a function meant to break. there is no column named 'different', so this should cause 
    a DatabaseError to be thrown upon execution. 
    :return: None 
    """ 
    query = ''' 
     UPDATE db_app_testtable 
     SET different = 'lol no' 
     WHERE value1 = value2 
    ''' 
    try: 
     with transaction.atomic(): 
      cursor = connection.cursor() 
      cursor.execute(query) 
    except DatabaseError as ex: 
     print "broken_query has error %s" % (ex) 
     raise 
    finally: 
     cursor.close() 
... 

def bulk_set(): 
    try: 
     set_no() 
     set_yes() 
     broken_query() 
    except Exception as gen_ex: 
     print "Exception has occurred." 
     raise 

正如你所看到的，broken_query()将无法​​正常工作，这是通过设计。我们试图设计一个代码块，如果broken_query()失败，它将回滚set_yes()和set_no()完成的操作，这是不可避免的。

鉴于django.db.transaction.atomic()的功能，这可能吗？读取documentation时，它说：“如果代码块已成功完成，则更改将提交给数据库。如果发生异常，则更改将回滚。”“我的问题是，这可以扩展到使在同一代码块中调用的其他操作也会回滚？

Answer 1

是的，在with atomic.transaction的同一个块中，如果您拨打raise Exception，您将使事务回滚。