Ok i see. Yes, approach from blog post will work. But the deeper collection have to be fetched, the bigger cartesian product will be returned. I have 5-6 levels tree.
On Fri, Oct 3, 2008 at 7:10 PM, Ken Egozi <[EMAIL PROTECTED]> wrote: > ok, here's why it's not working: > > when you access c.Customers, NH can't be sure that all of the relevant > customers for c are loaded. so it's going to the DB. > the approach described in the said blog post is loading the child > collection based on a join to the type it belongs to > > so, "select cs from Country c join fetch c.Customers cs where c = :c" > should work. > > On Fri, Oct 3, 2008 at 7:04 PM, Andrew Melnichuk < > [EMAIL PROTECTED]> wrote: > >> Just to be sure... if NH logs sql statement, is it 100% will reach db? I'm >> just using SQLite inmemory mode, can't use profiler. >> >> >> On Fri, Oct 3, 2008 at 7:03 PM, Andrew Melnichuk < >> [EMAIL PROTECTED]> wrote: >> >>> I changed >>> Assert.That(NHibernateUtil.IsInitialized(c.Customers)); >>> to >>> Assert.That(c.Customers.Count == 2); >>> >>> and it still hits the db, here is the SQL >>> >>> // for root >>> select country0_.Id as Id0_, country0_.Name as Name0_ from Country >>> country0_ where (Name='Germany' ) >>> >>> // for collection >>> select customer0_.Id as Id1_, customer0_.Name as Name1_, >>> customer0_.CountryId as CountryId1_ from Customer customer0_ where >>> ([EMAIL PROTECTED] )and(customer0_.Name='GermanyCustomer1' ); @p0 = >>> '1' >>> >>> // for collection.count >>> SELECT customers0_.CountryId as CountryId1_, customers0_.Id as Id1_, >>> customers0_.Id as Id1_0_, customers0_.Name as Name1_0_, >>> customers0_.CountryId as CountryId1_0_ FROM Customer customers0_ WHERE >>> [EMAIL PROTECTED]; @p0 = '1' >>> >>> >>> >>> On Fri, Oct 3, 2008 at 6:54 PM, Ken Egozi <[EMAIL PROTECTED]> wrote: >>> >>>> try to simply access the c.Customers and check (via show-sql or DB >>>> profiler) that the DB is not being hit, but the customers data is being >>>> hooked from the session cache. >>>> >>>> >>>> On Fri, Oct 3, 2008 at 6:40 PM, Andrew Melnichuk < >>>> [EMAIL PROTECTED]> wrote: >>>> >>>>> Hi all. >>>>> >>>>> I have a complex object graph. There is a root entity which has a set >>>>> of collections (some of them are pretty big), entities in collections have >>>>> their own collections etc.. - a kind of tree. I need to fetch this tree >>>>> with >>>>> minimum performance hit for database. I have tried 2 options for now: >>>>> 1st - load root entity, and then navigate through properties to load >>>>> all child and grandchild collections, ofcourse set fetch="subselect" in >>>>> mapping file before, to prevent select n+1 problem >>>>> 2nd - use approach, described here >>>>> http://blogs.hibernatingrhinos.com/nhibernate/archive/2008/04/06/eager-loading-aggregate-with-many-child-collections.aspx, >>>>> where different collections load by different queries, but session is >>>>> smart >>>>> enough, to merge different result to object graph, initializing different >>>>> collections. >>>>> >>>>> But i can't use 1st approach, because i can't define fetch plan on a >>>>> global level (number of reasons), and i can't use 2nd approach, because it >>>>> seems that it works fine for 1st level collection only, selecting deeper >>>>> level collections will produce cartesian product, which will grow with >>>>> level >>>>> of query of collection. >>>>> >>>>> What i thought about, is would it be possible to use approach based on >>>>> several queries, like 2nd approach i mentioned. The difference is i tried >>>>> to >>>>> start fetching not from the root entity level, but from the level i have >>>>> to >>>>> fetch next, after i already fetched with previous query. For example: >>>>> >>>>> [Test] >>>>> public void Test1() >>>>> { >>>>> // load root entity >>>>> Country c = _session >>>>> .CreateQuery("from Country where Name = 'Germany'") >>>>> .List<Country>()[0]; >>>>> >>>>> // trying to load 1st level child collection >>>>> _sess >>>>> .CreateQuery("from Customer cs where cs.Country = :c") >>>>> .SetParameter("c", c) >>>>> .List(); >>>>> >>>>> Assert.That(NHibernateUtil.IsInitialized(c.Customers)); // >>>>> fails >>>>> } >>>>> >>>>> I thought that session will initialize Country.Customers collection, >>>>> but it is not. >>>>> Ofcourse i could use eager join for this collection and others at the >>>>> same level, but as i said this will causes cartesian product for deeper >>>>> collections. >>>>> I'm not sure that what i did is valid, maybe it is invalid by design, >>>>> however it seems that session can initialize customers collection, since >>>>> it >>>>> "knows" to which country selected customers belongs. >>>>> >>>>> Just wanted to ask, how people solve same problems. >>>>> >>>>> -- >>>>> Best regards, >>>>> Andrew Melnichuk >>>>> >>>>> >>>>> >>>> >>>> >>>> -- >>>> Ken Egozi. >>>> http://www.kenegozi.com/blog >>>> http://www.musicglue.com >>>> http://www.castleproject.org >>>> http://www.gotfriends.co.il >>>> >>>> >>>> >>> >>> >>> -- >>> Best regards, >>> Andrew Melnichuk >>> >> >> >> >> -- >> Best regards, >> Andrew Melnichuk >> >> >> > > > -- > Ken Egozi. > http://www.kenegozi.com/blog > http://www.musicglue.com > http://www.castleproject.org > http://www.gotfriends.co.il > > > > -- Best regards, Andrew Melnichuk --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "nhusers" group. 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