#14970: Inconsistency in handling of managed/unmanaged transactions
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Reporter: mwrobel | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.2
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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I think that there are some bugs in the way the 'managed' flag is handled
in enter_transaction_management() and leave_transaction_management() in
django/db/transaction.py.
1. enter_transaction_management() has a 'managed' parameter. I guess it
should set the new transaction in managed mode depending on the value of
this parameter, but it takes the mode from the surrounding transaction or
from the settings (as stated in a comment). Surprisingly,
connection._enter_transaction_management() is called with the value of the
'managed' parameter instead of the mode that is set for the new
transaction.
2. leave_transaction_management() calls
connection._leave_transaction_management() passing the mode of the current
transaction (the transaction that is being left) as a parameter. From what
I can see in django/db/backends/postgresql_psycopg2/base.py, it expects to
get the mode of the transaction that will be active after
leave_transaction_management() finishes.
Now I will describe the use case in which I encountered the problems: I
use the psycopg2 backend and I want to have the connection in database-
level autocommit mode by default. Sometimes I want to begin a managed
transaction and after some operations commit or rollback it and return to
the database-level autocommit mode.
Currently I have to enter the transaction as follows:
{{{
enter_transaction_management(managed=True)
managed(True)
}}}
and leave:
{{{
managed(False)
leave_transaction_management()
}}}
I think that the managed() calls should be redundant, but the first/second
one is needed to circumvent the first/second problem I mentioned.
My proposal is to:
1. change enter_transaction_management() to set mode depending on the
parameter (and when parameter is not given, take the mode from the
surrounding transaction or the settings).
2. change leave_transaction_management() to pass the mode of the
transaction that becomes active to
connection._leave_transaction_management() (I don't know what was the
intended semantics, but it is what pycopg2 backend seems to expect, and
other backends don't override _leave_transaction_management()).
I see that the proposed changes can break backward compatibility, but I
think that they don't change any documented behavior.
I can create patches that fix the problem, but I would like to hear from
Django developers if the fix is acceptable before I write the patches.
--
Ticket URL: <http://code.djangoproject.com/ticket/14970>
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