tests/modeltests/transactions/models.py

   1 """
   2 15. Transactions
   3
   4 Django handles transactions in three different ways. The default is to commit
   5 each transaction upon a write, but you can decorate a function to get
   6 commit-on-success behavior. Alternatively, you can manage the transaction
   7 manually.
   8 """
   9
  10 from django.db import models
  11
  12 class Reporter(models.Model):
  13     first_name = models.CharField(max_length=30)
  14     last_name = models.CharField(max_length=30)
  15     email = models.EmailField()
  16
  17     def __unicode__(self):
  18         return u"%s %s" % (self.first_name, self.last_name)
  19
  20 __test__ = {'API_TESTS':"""
  21 >>> from django.db import connection, transaction
  22 """}
  23
  24 from django.conf import settings
  25
  26 building_docs = getattr(settings, 'BUILDING_DOCS', False)
  27
  28 if building_docs or settings.DATABASE_ENGINE not in ('mysql', 'mysql_old'):
  29     __test__['API_TESTS'] += """
  30 # the default behavior is to autocommit after each save() action
  31 >>> def create_a_reporter_then_fail(first, last):
  32 ...     a = Reporter(first_name=first, last_name=last)
  33 ...     a.save()
  34 ...     raise Exception("I meant to do that")
  35 ...
  36 >>> create_a_reporter_then_fail("Alice", "Smith")
  37 Traceback (most recent call last):
  38     ...
  39 Exception: I meant to do that
  40
  41 # The object created before the exception still exists
  42 >>> Reporter.objects.all()
  43 [<Reporter: Alice Smith>]
  44
  45 # the autocommit decorator works exactly the same as the default behavior
  46 >>> autocomitted_create_then_fail = transaction.autocommit(create_a_reporter_then_fail)
  47 >>> autocomitted_create_then_fail("Ben", "Jones")
  48 Traceback (most recent call last):
  49     ...
  50 Exception: I meant to do that
  51
  52 # Same behavior as before
  53 >>> Reporter.objects.all()
  54 [<Reporter: Alice Smith>, <Reporter: Ben Jones>]
  55
  56 # With the commit_on_success decorator, the transaction is only comitted if the
  57 # function doesn't throw an exception
  58 >>> committed_on_success = transaction.commit_on_success(create_a_reporter_then_fail)
  59 >>> committed_on_success("Carol", "Doe")
  60 Traceback (most recent call last):
  61     ...
  62 Exception: I meant to do that
  63
  64 # This time the object never got saved
  65 >>> Reporter.objects.all()
  66 [<Reporter: Alice Smith>, <Reporter: Ben Jones>]
  67
  68 # If there aren't any exceptions, the data will get saved
  69 >>> def remove_a_reporter():
  70 ...     r = Reporter.objects.get(first_name="Alice")
  71 ...     r.delete()
  72 ...
  73 >>> remove_comitted_on_success = transaction.commit_on_success(remove_a_reporter)
  74 >>> remove_comitted_on_success()
  75 >>> Reporter.objects.all()
  76 [<Reporter: Ben Jones>]
  77
  78 # You can manually manage transactions if you really want to, but you
  79 # have to remember to commit/rollback
  80 >>> def manually_managed():
  81 ...     r = Reporter(first_name="Carol", last_name="Doe")
  82 ...     r.save()
  83 ...     transaction.commit()
  84 >>> manually_managed = transaction.commit_manually(manually_managed)
  85 >>> manually_managed()
  86 >>> Reporter.objects.all()
  87 [<Reporter: Ben Jones>, <Reporter: Carol Doe>]
  88
  89 # If you forget, you'll get bad errors
  90 >>> def manually_managed_mistake():
  91 ...     r = Reporter(first_name="David", last_name="Davidson")
  92 ...     r.save()
  93 ...     # oops, I forgot to commit/rollback!
  94 >>> manually_managed_mistake = transaction.commit_manually(manually_managed_mistake)
  95 >>> manually_managed_mistake()
  96 Traceback (most recent call last):
  97     ...
  98 TransactionManagementError: Transaction managed block ended with pending COMMIT/ROLLBACK
  99 """