Support for transactions using 'with' statement

[Former user]

This patch allows SessionTransaction objects to be used with python 2.5's 'with' statement:

with session.create_transaction():
    item1 = sess.query(Item).get(1)
    item2 = sess.query(Item).get(2)
    item1.foo = 'bar'
    item2.bar = 'foo'

If the operations all complete successfully then the transaction is committed, otherwise it is rolled back. It's a bit simpler than:

trans = session.create_transaction()
try:
    item1 = sess.query(Item).get(1)
    item2 = sess.query(Item).get(2)
    item1.foo = 'bar'
    item2.bar = 'foo'
    trans.commit()
except:
    trans.rollback()
    raise

[Mike Bayer]

beautiful. like in other tickets, i only have web access ATM so ETA on this will be by early next week...if youre bored, an extra patch for the documentation (unitofwork.txt) might be nice.

[Former user]

A few things I was thinking about are whether or not {{{enter}}} should return the transaction object, and if {{{exit}}} should check whether the transaction is closed before trying to commit or roll it back.

As the patch is, this causes an error:

with sess.create_transaction() as t:
    item1 = sess.query(Item).get(1)
    item2 = sess.query(Item).get(2)
    item1.foo = 'bar'
    item2.bar = 'foo'
    t.commit()
    # other stuff...

since {{{t.exit}}} tries to commit the transaction again.

It seems to me like it would make the most sense to have {{{exit}}} check if the transaction is closed, and if so, to neither commit nor rollback the transaction.

[Former user]

attachment:session.2.patch adds a check in __exit__ to see if the transaction has been closed (it checks self.session.transaction, is that the correct way to do this?)

I also updated unitofwork.txt

[Mike Bayer]

changeset:2311

[Mike Bayer]

yeah, i think checking the session is OK for now (its basically an is_closed() check).