You can use a similar select you are using in the old system and then you can return only the root from your DAO.BTW 3000 entities in RAM will have some cost.
2009/3/18 kello <[email protected]> > > I am working on a system that has Bill Of Materials (BOM) which > contains about 1000-3000 parts organized in a hierarchy about 10 > levels deep. The system was using Typed Datasets but I have converterd > parts of it to use an object model and NHibernate for persistance. > > The problem is that the NHibernate version is currently much slower > than the dataset version because of the time it takes to load a BOM > into memory. In the old system the entire BOM is loaded into a dataset > in less than a second using a single SELECT (then there is of course a > lot of ugly code working with the dataset in-memory). > > Now in the NHibernate version the BOM is loaded as a root entity which > has a persistent collection of its parts which are entities of the > same class and they have collection of their parts etc. This causes > the loading to happen with one SELECT per collection load. I have read > the performance part of the reference docs and have added "batch-size" > to get more collections loaded with each level and it helped some but > it is still generating a lot of SELECT since the BOM is so large and > have lots of levels. Using a very large batch-size does not seem to > work either.... > > It is quite easy to make a special query using a single SELECT to get > all the objects in the BOM back in a single list but then I loose the > hierarchical organization since the collection of children in each > object are not loaded and when the collections are accessed they will > each generate a new SELECT to get filled anyway. > > I thought about making a special repository method to load all objects > in a single list with a single SELECT and then using some sorting code > to put the objects from this list into each BOM objects childrens > collection. The problem with this approach is that since the children > collection list is a mapped persistant collection the proxy object > will fill the collection when I access it. I would have to find some > way to temporarily bybass the proxy object's collection loading and > fill the childrens collection manually but I don't know how... or am I > on the wrong track here? Is there some other way to fill all > collections in a single SELECT but still have them mapped so they > cacade save etc.? > > Another problem is the deletion of a BOM. What happens is that first a > lot of SELECT is generated to sort out which objects belong to the BOM > and then a lot of DELETE is generated. It would be more effective if I > could do a single DELETE and then find and evict any BOM objects that > might be loaded in the session for the BOM being deleted. Could this > be done? > > > > > > > -- Fabio Maulo --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "nhusers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nhusers?hl=en -~----------~----~----~----~------~----~------~--~---
