On Wed, May 16, 2012 at 11:27 PM, Michael Bayer <mike...@zzzcomputing.com> wrote: > > On May 16, 2012, at 11:11 AM, limodou wrote: > >> Thank you for the detail explains. And I tried like this again: >> >> 1. if there are only select statements it will ok, and the select >> statements will fetch the new changed records. >> 2. select after update, if there is no record at some point, it'll not >> fetch the new changed records in the later loop, just like what you >> said the "state" is hold. >> >> So in my application, I need to do like: >> >> while True: >> for row in select(xxx): >> update(xxxx) >> >> And I want to keep each update has seperate transaction, maybe like this: >> >> while True: >> conn = engine.connect() >> for row in conn.execute(select(xxx)): >> trans = conn.begin() >> conn.execute(update(xxxx)) >> trans.commit() >> >> But above code is not right, I should put the transaction out of the >> loop just like what you written. So I want to know what is the suit >> appoach of keeping each update has seperate transaction? Should I use >> nested transaction? > > OK you need to use two different connections here, for the "read from one > connection, persist on another in a short transaction" pattern. Again the > "with engine.begin()" thing, which is new as of 0.7...6? makes this pretty > succinct: > > > while True: > with engine.begin() as conn: > for row in conn.execute(select...): > with engine.begin() as c2: > c2.execute(update...) > sleep(...) > >
Ok, I see. And the last word, is there a way to disable the accumulation of transactional state? Thank you very much. -- I like python! UliPad <<The Python Editor>>: http://code.google.com/p/ulipad/ UliWeb <<simple web framework>>: http://code.google.com/p/uliweb/ My Blog: http://hi.baidu.com/limodou -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
