Clarification on behavior of LEFT OUTER JOIN FETCH please

RF · **Joined:** Fri May 30, 2008 3:57 pm **Posts:** 26

version 1.2.1
.Net 3.5

Sometimes I get null objects returned when I'm doing a LEFT OUTER JOIN FETCH of an entity and it's children (or their children).

Code:

FROM parent p
LEFT OUTER JOIN FETCH p.children child
LEFT OUTER JOIN FETCH child.children

where the collections are either mapped as lists or sets. initial testing shows that NHibernate is smart enough to deduce that a null return means no children in the resultset, but I still sometimes get null objects.

Under what circumstances will the above hql return with null objects for the children? Not all of the child objects are null, but some of them are.

PS
I believe a skipped list index will also result in null being inserted for that specific index. but I was hoping for other scenario's.

thanks!

wolli · **Posted:** Thu Aug 07, 2008 2:36 am

Quote:

I believe a skipped list index will also result in null being inserted for that specific index. but I was hoping for other scenario's.

Afaik this is the bevahior you get when you have leaks in your index values and use lists. It shouldn't happen with sets since you don't have an index column there.