On Aug 6, 2013, at 8:14 PM, Victor Reichert <vfr...@gmail.com> wrote:
> Hi, > > I'm running: > > selected_eventids = [] > > selected_event = > self.session.query(Master_Simulation_Event).filter(Master_Simulation_Event.cumulative_probability > >= selection_percentile, > Master_Simulation_Event.event_id.notin_(selected_eventids) ).\ > order_by(Master_Simulation_Event.cumulative_probability - > selection_percentile).first() > > And it generates: > > 2013-08-06 18:03:43,196 INFO sqlalchemy.engine.base.Engine SELECT TOP 1 > master_simulation_events.id AS master_simulation_events_id, > master_simulation_events.event_id AS master_simulation_events_event_id, > master_simulation_events.rate AS master_simulation_events_rate, > master_simulation_events.sample_probability AS > master_simulation_events_sample_probability, > master_simulation_events.cumulative_probability AS > master_simulation_events_cumulative_probability > FROM master_simulation_events > WHERE master_simulation_events.cumulative_probability >= ? AND > master_simulation_events.event_id != master_simulation_events.event_id ORDER > BY master_simulation_events.cumulative_probability - ? > 2013-08-06 18:03:43,196 INFO sqlalchemy.engine.base.Engine > (0.19528160149168805, 0.19528160149168805) > > The important part is the notin_([]) is translated to: > master_simulation_events.event_id != master_simulation_events.event_id > > I recieve the following warning: > > C:\Python27\lib\site-packages\sqlalchemy\sql\expression.py:1982: SAWarning: > The IN-predicate on "master_simulation_events.event_id" was invoked with an > empty sequence. This results in a contradiction, which nonetheless can be > expensive to evaluate. Consider alternative strategies for improved > performance. > return o[0](self, self.expr, op, *(other + o[1:]), **kwargs) > > While it doesn't make a lot of sense to pass an empty list to an in_ clause I > think passing an emtpy list list to notin_ clause is OK and it shouldn't be > replaced. fixed in 3302187fea0ffd431b980081e7bc483ea364da2b (0.8.3) and 34ef21909bd6ed3574e37c345ca9e (master). You don't really need "notin" in any case, just use ~col.in_([]) for now.
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