#2227: atch] transaction.commit()/rollback() should be aware of nested calls to
transaction.managed(True)
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Reporter: md...@yandex.ru | Owner: nobody
Status: assigned | Milestone:
Component: Database layer (models, ORM) | Version: SVN
Resolution: | Keywords:
transaction, nest, scope
Stage: Accepted | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by Glenn):
This seems like a step in the right direction, but not being allowed to
call rollback() from within a nested transaction seems like a killer.
What are you supposed to do? You'd have to remember that you aren't the
top-level transaction level, raise an exception instead of rolling back,
and expect whoever is the top-level transaction to rollback for you once
the exception propagates out.
That's very brittle. If someone accidentally eats the exception before it
gets there, then the transaction might be committed, which is the worst
possible failure mode.
Instead, I'd suggest:
- when rollback is called when nested, mark the transaction failed;
- if commit is called when not nested and the transaction was marked
failed, raise an exception, because rollback should have been called
instead.
This allows calling rollback() to cancel the transaction, and guarantees
that the transaction will never be committed, which I think is a critical
invariant.
Then, this would work (easily dropped into a decorator):
{{{
def foo():
transaction.enter_transaction_management()
try:
# code
transaction.set_dirty()
transaction.commit()
except:
transaction.rollback()
raise
finally:
transaction.leave_transaction_management()
def fum():
transaction.enter_transaction_management()
try:
foo()
except:
transaction.rollback()
raise
finally:
transaction.leave_transaction_management()
}}}
--
Ticket URL: <http://code.djangoproject.com/ticket/2227#comment:17>
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