On Oct 1, 12:54 pm, Michael Bayer <mike...@zzzcomputing.com> wrote: > Any extension, mapper or session, can cancel the operation overall by raising > an exception, which will result in halting the flush and issuing a ROLLBACK. > Usually, if something goes "wrong" inside of a transaction, the whole thing > is rolled back since you otherwise have only a partial state of data. > > Inside of mapper extension, a simplistic "dont update the row" operation may > be possible if you just expired the attributes of the instance inside of > before_update(), though I haven't tried this and it wouldnt really work for > inserts or deletes anyway. > > Within session extension, its common to search for objects by traversing > through the .new, .dirty and .deleted collections. 0.7 will be expanding > on this model by providing event listener hooks that do this filtering for > you, sending only objects of the desired type to the listener, and from that > it follows that we can eventually optimize the search by improving the > bookkeeping performed by these collections. SessionExtension is definitely > the more generic choice overall these days for flush events. the use cases > for MapperExtension are much smaller.
Sounds good. I suppose I would most often raise an exception to rollback the entire flush, but in rare cases I might want to go ahead and save the rest of the object I would just detach one from the session and delete it. Thanks for you reply, Landreville -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@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.
