bulk update/delete events / invent new system for changing event arguments

[Mike Bayer]

the bulk UD events should have access to the arguments that were passed:

def after_bulk_update(self, session, query, query_context, values, synchronize_session, result):
   ""

and while we're at it, mapper events should get some more context too:

    def before_insert(self, session, flush_context, mapper, connection, target):
         ""

how can we pull this off? we'd need to build a really smart argument adapter that uses inspect:

@event.legacy_signature("0.9", ["query", "query_context", "result"]("session",))
def after_bulk_update(self, session, query, query_context, values, synchronize_session, result):
   ""

legacy_signature would need to receive the decorated fn, use inspect to look at how many arguments it accepts, then produce a translation wrapper corresponding to the given signature. it should even stick a "..versionchanged::" directive into the docstring.

another issue, these events take a crapload of arguments. How do we deal with that? Let's support this too:

@event.listens_for(Session, "after_bulk_update")
def after_update(self, **kw):

with the above signature the event system will detect that, and just send all args in as key/value pairs, so that event handlers can be written more simply just to look for what they need.

[Mike Bayer]

02a81707dc8b7c4d69551cad195fb has the work within master for the moment. we might consider porting the documentation part of this to 0.8. before_insert() etc. is left alone. bulk update/delete, it's just sending the BulkUD object itself for now - I didn't want the **kw style to fire off implicitly, you need to listen with named=True to take advantage of that.

[Mike Bayer]

Removing milestone: 0.9.0 (automated comment)