On Tuesday 27 March 2007 09:08:32 chris e wrote: > Currently when sqlalchemy performs a polymorphic lookup, it queries > against all the detail tables, and returns the correct Python > object represented by the polymorphic identity. Essentially you get > a sub select for each detail table that is included in your primary > join even though only one of the detail tables contains the data > that is specific to the identity of the object. Is there currently > a way, or a plan to support, splitting the polymorphic query into > two queries? The first would get the base table, the second would > retrieve the details based on the discovered table. This way only > two tables would be queried instead of n where n is the number of > polymorphic identities. can u explain some more.. e.g. how do u know which is that 2nd table of yours? what would be these 2 queries?
Lets say u have 5 leaf types in 4-5 levels of the hierarchy tree, say that makes 10 tables total. say E object is a leaf and comes from A.join(B).join(C).join(E) - so E is split amongst all A B C E tables. Which is the detail table? or are u talking concrete tables? > Our DBAs have concerns that as our tables grow, possibly to the > size of 2.5million rows, that unioning against multiple tables, > despite the fact that we are unioning against a primary key, will > become non- performant. I know I could write a custom mapper to > resolve this issue, however, I thought I would bring this up since > it may affect other users, and there may already be a way to solve > this easily of which I am not aware. it will surely affect me, as i target 10M rows - in order to feel very comfortable under 1M. svil --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
