On Apr 5, 2006, at 8:12 AM, Qvx wrote:
Good as long as this connection is now accessible only to it's
caller. Once I get connection it is *mine* and there are no
surprise operations carried out over this connection by some other
parts of the system. This connection must be used only in places
where I explicitly use it be it via using(), set_current() or some
other ways.
Once I'm done with it, how do I release such connection back to
pool so it can be used by other parts of the system?
yes, its unique to you owning it. to release it, you just let go of
it. The pooling module works based on the Connection object falling
out of scope, which is what will ultimately occur.
# 4. natural nesting behavior
As always, begin/commit/rollback uses the "outermost nested" idea,
where "nested" calls to begin/commit dont affect the single
"outermost" transaction.
e = create_engine('foo')
trans = e.begin()
try:
mytable.update().execute()
# then in some other function..
trans2 = e.begin()
try:
myothertable.update.execute()
trans2.commit() # doesnt commit
except:
trans2.rollback() # rolls trans2, trans
trans.commit() # commits mytable, myothertable
except:
trans.rollback() # rolls back trans
"trans2.rollback()" will also roll back "mytable.update().execute
()". On Oracle you would have to issue savepoint and then rollback
to this savepoint in order to achieve partial rollback. On other
databases this is perhaps handled differently.
the point is, there is only one real transaction occuring above. the
second call to begin() returns a no-op, as does the commit() on trans2.
Yes, but in my case it is more like this:
trans_mssql = engine_mssql.begin()
trans_oracle = engine_oracle.begin()
trans_mysql = engine_mysql.begin()
try:
#...
trans_mssql.commit()
trans_oracle.commit()
trans_mysql.commit()
except:
trans_mssql.rollback()
trans_oracle.rollback()
trans_mysql.rollback()
you need something else, which I havent gotten into with this
proposal, which is a TransactionManager. youd gather up all your
ConnectionProxy objects and register them with a TransactionManager
that does a pattern like the above. This is something I could take
a stab at, but its not something I have deep experience with (also
the JTA docs, which describe the J2EE standard for this sort of
thing, are somewhat daunting)...it would be a little simplistic to
start out. Or folks could contribute such a thing, theyre likely to
put more thought into it than me.
-------------------------------------------------------
This SF.Net email is sponsored by xPML, a groundbreaking scripting language
that extends applications into web and mobile media. Attend the live webcast
and join the prime developer group breaking into this new coding territory!
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
_______________________________________________
Sqlalchemy-users mailing list
Sqlalchemy-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users
