For a variety of reasons, sometimes it's nice to be able to do something
like this:
with dbsess.begin(rollback=True):
do_stuff
Where the expected behavior is that everything in the context runs in a
transaction, but upon exiting the context we issue a rollback. Sometimes
this is useful to *guarantee* that actions that take place within the
context are transactionally read-only.
I had authored and am using this:
def make_dbsess_contextual(sess_factory):
@contextmanager
def dbsess(on_success='commit'):
sess = sess_factory()
# we could use 'with sess.begin() here but it's
# easier to have parity
sess.begin()
try:
yield sess
except:
sess.rollback()
sess.close()
raise
else:
if on_success == 'commit':
sess.commit()
else:
sess.rollback()
sess.close()
return dbsess
and it's used like this:
factory = ....
contextual_factory = make_dbsess_contextual(factory)
with contextual_factory('rollback') as dbsess:
do_stuff(dbsess)
however it would be nice if the functionality could be integrated directly.
I also strongly suspect that the way I've approached this is non-optimal.
I looked at the code for how this might work and I have some ideas but I
thought I'd check here first to see if I'm completely off-base.
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