Not sure if this is possible, but...

I have a hierarchy of objects (call it Task) where each Task object can have a parent Task object (the Parent property) and a collection of child Task objects (the Children property). If the parent is null then it's a ROOT object, if it has a parent and children it's a PARENT object and if it's got a parent but no children it's a LEAF object. The Task type is lazy loaded.

My question is can you select a subset of the ROOT nodes (say the first 50) and all their child objects, and their children, their children's children (etc, etc) down the the leaf objects using HQL?

Thanks in advance to those who have a clue.

Cheers,

Symon.

You can select the a subset of the ROOT nodes... (if you want, the first 50) and after that, you can call the "Children" relationship and that will fetch the childs... but feching all down to leafs... in just one shot... I find that hard to do...

Hmmm. That's what I thought. I know I can use the FETCH keyword to populate the Children collection of each of the ROOT objects, but that won't take care of the Children collections of each *those* objects.

I'm just trying to work out how to minimize round trips to the database to display a hierarchy.

Symon.

You could use some database-specific hierarchical SQL (like START WITH ... CONNECT BY in Oracle) in a native SQL query and get all the needed objects into memory in one roundtrip, but I think NH won't be smart enough to organize them into collections properly, so all Children collections will be left uninitialized and will cause an extra database query when accessed. I'm not so sure about this, so maybe it could actually be made to work.

In any case, the Parent properties of all objects will be set correctly after the first query though.

Hey Sergey - I'll investigate that.

Thanks,

Symon.