django - Django select_for_update不能在事务外部使用

Question

我使用的是Django 1.5.1，并已升级到Django 1.6.6。

在Django 1.5.1中，我使用select进行更新以保证原子执行。

job_qs = Job.objects.select_for_update().filter(pk=job.id)
for job in job_qs:

不幸的是，这现在抛出一个错误：

  File "/srv/venvs/django-picdoc/local/lib/python2.7/site-packages/django/db/models/query.py", line 96, in __iter__
    self._fetch_all()

  File "/srv/venvs/django-picdoc/local/lib/python2.7/site-packages/django/db/models/query.py", line 857, in _fetch_all
    self._result_cache = list(self.iterator())

  File "/srv/venvs/django-picdoc/local/lib/python2.7/site-packages/django/db/models/query.py", line 220, in iterator
    for row in compiler.results_iter():

  File "/srv/venvs/django-picdoc/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 713, in results_iter
    for rows in self.execute_sql(MULTI):

  File "/srv/venvs/django-picdoc/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 776, in execute_sql
    sql, params = self.as_sql()

  File "/srv/venvs/django-picdoc/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 147, in as_sql
    raise TransactionManagementError("select_for_update cannot be used outside of a transaction.")

TransactionManagementError: select_for_update cannot be used outside of a transaction.

有哪些解决方案可以解决此问题？

Answer 1

答案在错误中，将查询包装在事务中

Django的文档位于：https://docs.djangoproject.com/en/dev/topics/db/transactions/#django.db.transaction.atomic

一种方法是：

from django.db import transaction

def some_method():    
   with transaction.atomic():
      job_qs = Job.objects.select_for_update().filter(pk=job.id)
      for job in job_qs: