On Monday 16 July 2007 17:08:08 Michael Bayer wrote: > On Jul 16, 2007, at 2:59 AM, Yves-Eric wrote: > > Thanks for the explanation! The root of the issue is now very > > clear. But are you saying that this is intended behavior? Was I > > wrong in trying to use the session as an object cache? > > this is why im extremely hesitant to call the session a "cache". > its only slightly cachelike becuase in most cases it doesnt prevent > SQL from being issued. > > > Now onto a possible solution or workaround... Please forgive me > > if the following does not make sense, but would it be possible to > > store our object in the identity map under a second key: (Person, > > (2,))? Then the Person mapper would find it and we'd avoid having > > to generate a DB query. Is there any technical issue that would > > prevent the same object from being registered under different > > keys in the identity map? > > There are some kinds of inheritance where both Person/2 and > Employee/ 2 exist distinctly, namely the concrete inheritance svil > mentions. so that makes me less comfortable with that approach. > it does seem like you can in many cases define the set of > identities for an entire class hierarchy a/b/c/d/e... against the > root mapper only, i.e. just (A, (id,)). its something to look > into (changing the key to represent based on the root class in all > non-concrete cases, not storing two keys).
i think it is not a problem to store as many keys as there are identical levels in polymorphism/inheritance as long as this is synchronized with type of inheritance. i.e. joined-table inheritance chains (and single table maybe) are ok as is, anything concrete-table in between changes the game. As for the concrete, i think it can be done same as with polymorphism - storing composite keys (type,id) where just keys are ambigious. but i bet noone has ever wanted mixed inheritance, no? (:-) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
