django/tests/modeltests/transactions/models.py

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"""
15. Transactions
Django handles transactions in three different ways. The default is to commit
each transaction upon a write, but you can decorate a function to get
commit-on-success behavior. Alternatively, you can manage the transaction
manually.
"""
from django.db import models
class Reporter(models.Model):
first_name = models.CharField(maxlength=30)
last_name = models.CharField(maxlength=30)
email = models.EmailField()
def __str__(self):
return "%s %s" % (self.first_name, self.last_name)
API_TESTS = """
>>> from django.db import connection, transaction
"""
from django.conf import settings
building_docs = getattr(settings, 'BUILDING_DOCS', False)
if building_docs or settings.DATABASE_ENGINE != 'mysql':
API_TESTS += """
# the default behavior is to autocommit after each save() action
>>> def create_a_reporter_then_fail(first, last):
... a = Reporter(first_name=first, last_name=last)
... a.save()
... raise Exception("I meant to do that")
...
>>> create_a_reporter_then_fail("Alice", "Smith")
Traceback (most recent call last):
...
Exception: I meant to do that
# The object created before the exception still exists
>>> Reporter.objects.all()
[<Reporter: Alice Smith>]
# the autocommit decorator works exactly the same as the default behavior
>>> autocomitted_create_then_fail = transaction.autocommit(create_a_reporter_then_fail)
>>> autocomitted_create_then_fail("Ben", "Jones")
Traceback (most recent call last):
...
Exception: I meant to do that
# Same behavior as before
>>> Reporter.objects.all()
[<Reporter: Alice Smith>, <Reporter: Ben Jones>]
# With the commit_on_success decorator, the transaction is only comitted if the
# function doesn't throw an exception
>>> committed_on_success = transaction.commit_on_success(create_a_reporter_then_fail)
>>> committed_on_success("Carol", "Doe")
Traceback (most recent call last):
...
Exception: I meant to do that
# This time the object never got saved
>>> Reporter.objects.all()
[<Reporter: Alice Smith>, <Reporter: Ben Jones>]
# If there aren't any exceptions, the data will get saved
>>> def remove_a_reporter():
... r = Reporter.objects.get(first_name="Alice")
... r.delete()
...
>>> remove_comitted_on_success = transaction.commit_on_success(remove_a_reporter)
>>> remove_comitted_on_success()
>>> Reporter.objects.all()
[<Reporter: Ben Jones>]
# You can manually manage transactions if you really want to, but you
# have to remember to commit/rollback
>>> def manually_managed():
... r = Reporter(first_name="Carol", last_name="Doe")
... r.save()
... transaction.commit()
>>> manually_managed = transaction.commit_manually(manually_managed)
>>> manually_managed()
>>> Reporter.objects.all()
[<Reporter: Ben Jones>, <Reporter: Carol Doe>]
# If you forget, you'll get bad errors
>>> def manually_managed_mistake():
... r = Reporter(first_name="David", last_name="Davidson")
... r.save()
... # oops, I forgot to commit/rollback!
>>> manually_managed_mistake = transaction.commit_manually(manually_managed_mistake)
>>> manually_managed_mistake()
Traceback (most recent call last):
...
TransactionManagementError: Transaction managed block ended with pending COMMIT/ROLLBACK
"""