[Sqlalchemy-tickets] [sqlalchemy] #2809: Strange effect with association proxy and event listener

[sqlalchemy <mi...@zz...>]

#2809: Strange effect with association proxy and event listener
----------------------+-----------------------------------------
 Reporter:  schlamar  |           Owner:  zzzeek
     Type:  defect    |          Status:  new
 Priority:  medium    |       Milestone:  0.8.xx
Component:  (none)    |        Severity:  no triage selected yet
 Keywords:            |  Progress State:  awaiting triage
----------------------+-----------------------------------------
 I'm getting this strange traceback in a proprietary codebase.
 `job.programs` is an association proxy to `job.job_programs`.
 `set_max_stat_program_added` is an event handler listening on
 `job.job_programs.append`.

 Unfortunately I'm not able to reproduce this issue with a simple test
 case. But it looks to me that the flush in the event callback is emitting
 a wrong SQL statement related to the association proxy. I can further
 investigate and debug this issue if someone gives me instructions but I'm
 not allowed to publish the code.

 A workaround for this issue is to preload `job.pallets` with `joinedload`
 in the query.


 {{{
 Traceback (most recent call last):
   File "tests\test_resources.py", line 251, in test_check_enable
     job_res.update(job_id, {'programs': [prog_id], 'enabled': True})
   File "mes\resource.py", line 185, in update
     job.programs.append(prog)
   File "packages\sqlalchemy\ext\associationproxy.py", line 568, in append
     self.col.append(item)
   File "packages\sqlalchemy\orm\collections.py", line 1057, in append
     item = __set(self, item, _sa_initiator)
   File "packages\sqlalchemy\orm\collections.py", line 1029, in __set
     item = getattr(executor, 'fire_append_event')(item, _sa_initiator)
   File "packages\sqlalchemy\orm\collections.py", line 733, in
 fire_append_event
     item, initiator)
   File "packages\sqlalchemy\orm\attributes.py", line 910, in
 fire_append_event
     value = fn(state, value, initiator or self)
   File "packages\sqlalchemy\orm\events.py", line 1496, in wrap
     orig_fn(target, value, *arg)
   File "mes\model.py", line 81, in set_max_stat_program_added
     for pallet in job.pallets:
   File "packages\sqlalchemy\orm\attributes.py", line 316, in __get__
     return self.impl.get(instance_state(instance), dict_)
   File "packages\sqlalchemy\orm\attributes.py", line 613, in get
     value = self.callable_(state, passive)
   File "packages\sqlalchemy\orm\strategies.py", line 524, in
 _load_for_state
     return self._emit_lazyload(session, state, ident_key, passive)
   File "packages\sqlalchemy\orm\strategies.py", line 585, in
 _emit_lazyload
     result = q.all()
   File "packages\sqlalchemy\orm\query.py", line 2237, in all
     return list(self)
   File "packages\sqlalchemy\orm\query.py", line 2348, in __iter__
     self.session._autoflush()
   File "packages\sqlalchemy\orm\session.py", line 1139, in _autoflush
     self.flush()
   File "packages\sqlalchemy\orm\session.py", line 1818, in flush
     self._flush(objects)
   File "packages\sqlalchemy\orm\session.py", line 1936, in _flush
     transaction.rollback(_capture_exception=True)
   File "packages\sqlalchemy\util\langhelpers.py", line 58, in __exit__
     compat.reraise(exc_type, exc_value, exc_tb)
   File "packages\sqlalchemy\orm\session.py", line 1900, in _flush
     flush_context.execute()
   File "packages\sqlalchemy\orm\unitofwork.py", line 372, in execute
     rec.execute(self)
   File "packages\sqlalchemy\orm\unitofwork.py", line 525, in execute
     uow
   File "packages\sqlalchemy\orm\persistence.py", line 64, in save_obj
     table, insert)
   File "packages\sqlalchemy\orm\persistence.py", line 569, in
 _emit_insert_statements
     execute(statement, params)
   File "packages\sqlalchemy\engine\base.py", line 662, in execute
     params)
   File "packages\sqlalchemy\engine\base.py", line 761, in
 _execute_clauseelement
     compiled_sql, distilled_params
   File "packages\sqlalchemy\engine\base.py", line 874, in _execute_context
     context)
   File "packages\sqlalchemy\engine\base.py", line 1024, in
 _handle_dbapi_exception
     exc_info
   File "packages\sqlalchemy\util\compat.py", line 195, in raise_from_cause
     reraise(type(exception), exception, tb=exc_tb)
   File "packages\sqlalchemy\engine\base.py", line 867, in _execute_context
     context)
   File "packages\sqlalchemy\engine\default.py", line 324, in do_execute
     cursor.execute(statement, parameters)
 IntegrityError: (IntegrityError) job_programs.job_id may not be NULL
 u'INSERT INTO job_programs (program_id) VALUES (?)'
  (1,)
 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2809>
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