DistinctRootEntityResultTransformer and HQL

mcooke24 · **Joined:** Thu Oct 26, 2006 4:02 pm **Posts:** 12

Is DistinctRootEntityResultTransformer supported with HQL? The following is a sample Northwind system where Customer has a set of Orders. Most of the time I want to lazy load the Orders collection, but for this specific case I want to be able to load all of the Customer objects with their Orders collection already initialized.

Code:

IQuery query = Session.CreateQuery("select c from Customer c join fetch c.Orders");
query.SetResultTransformer(new DistinctRootEntityResultTransformer());
IList results = query.List();

When I run this code, I get the following exception:

Code:

Unable to cast object of type 'Northwind.Customer' to type 'System.Object[]'.

I've been able to achieve the same behavior by using a criteria query.

Code:

ICriteria criteria = Session.CreateCriteria(typeof(Customer));
criteria.SetFetchMode("Orders", FetchMode.Join);
criteria.SetResultTransformer(new DistinctRootEntityResultTransformer());
IList results = criteria.List();

However, I really would like to use HQL so that I can take advantage of some other features in more complex queries that require the same principle. Is DistinctRootEntityResultTransformer not supported with HQL?

sethrohit1977 · **Joined:** Mon Jan 22, 2007 10:32 am **Posts:** 101

HQL do support distinct keyword. Try something like

select distinct c from Customer c join fetch c.Orders

mcooke24 · **Joined:** Thu Oct 26, 2006 4:02 pm **Posts:** 12

The distinct keyword doesn't do what I want. When I tried using it, it added the distinct keyword to the SQL that was generated but since I'm doing a join on the Orders table I ended up with with a bunch of duplicate customers that each had 1 distinct order. I'm pretty sure that I'm supposed to use the DistinctRootEntityResultTransformer as I've used it lots before when doing a Criteria query, but I'm just wading into HQL for the first time and want the same behavior.

mcooke24 · **Joined:** Thu Oct 26, 2006 4:02 pm **Posts:** 12

I found the answer. It's a bug in 1.2.0 but is fixed in the development trunk. http://jira.nhibernate.org/browse/NH-1018