nested transactions with zope extension
gizli
This is only for people who use the zope extension for SA (http://
pypi.python.org/pypi/zope.sqlalchemy). Consider the following:
for task in conn.query(Task):
conn.begin_nested()
try:
conn.delete(task)
conn.commit()
except Exception:
conn.rollback()
conn.commit()
I noticed that when I use the zope extension and the transaction
manager, I have to code this differently to do the same thing. Most
noticeably, I cannot have a commit inside the for loop anymore (which
closes/discards the save-point). The reason is that transaction.commit
() automatically discards all nested save-points and commits the
entire transaction. So, I need to do something like this:
for task in conn.query(Task):
conn.begin_nested()
try:
conn.delete(task)
except Exception:
conn.rollback()
transaction.commit()
Is this acceptable and expected? It just seems wrong to begin nested
transactions this way. conn.commit() is strictly forbidden by the zope
extension. May be the zope extension should allow commits if they are
discarding a savepoint rather than actually doing a commit? Or may be
SA should have a conn.end_nested() rather than commit? Right now, the
terminology is confusing (when I first saw the first piece of code, I
thought the loop was committing the changes at each iteration).
Could you please shed some light on this situation?
Thanks.
Daniel Holth
Take a look at transaction.savepoint(). It looks like it may only
support rolling back (not committing) savepoints.
http://svn.zope.org/repos/main/zope.sqlalchemy/trunk/src/zope/sqlalchemy/