On Aug 2, 2010, at 1:58 PM, SQLAlchemy User wrote: >>> I ha > Thanks, Michael. Two followup questions: > > 1) The histogram() method is designed to provide statistics on a set > of Events (defined by a query), so it made sense (to me) to make it a > method of EventQuery. I don't know how I'd do this as a method of > Event. Could you clarify?
Well if you need to say Event.<generate query>.<generate query>.histogram(), then yeah I see what you are going for, though you might say Event.histogram.<generate query>.<generate query>, that's probably not as appealing. > > 2) When you say 'old "query property"' accessor, are you implying that > query_property is deprecated? Is there an alternative? I really like > the idea of subclassing Query and adding custom methods. Is this a > misguided approach? subclassing Query and using query_property aren't necessarily connected things. The idea of MyClass.query(foo) isn't deprecated, though it is kind of an old pattern back when we were trying to hide the Session as much as possible (or when there wasn't really even a Session). I tend towards a more coarse grained interface, I guess, i.e. I'd just have a coarse grained Event.histogram(x, y, z) type of method that works only for the necessary use cases. I don't have a strong case for that approach (I have a weak one which is, hide complexity, sort of). > BTW: the values() generator takes at least as long as the from_self() > does, and uses a huge amount of memory since all().values() still > passes the entire object list to python. from_self() took 1920 seconds > to run against the entire 'events' table, where > Session.query(func.distinct(Event.source)).all() took 0.02 seconds. > I'll try experimenting with joins next. values() should be using the least amount of memory of any approach - it only buffers 10 rows in memory at a time, and doesn't deal with session or object accounting at all so is also much more performant than all(). I dont know what "all().values()" is or if that's a typo. Session.query(Event).values(func.distinct(Event.source)) should emit a brief "SELECT DISTINCT" query and whip through a single column for the result. -- 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.
