Hi,

I have a Hierarchy. The super class is A, and child class are A1, A2 and A3. I need get all instances of A1 and A2, but i don't have an interface between A and A1, A2.

Any idea ?

I make a query with a 2 exists() sentences into where condition, but is very slow for my intention.

best regards
epsino

I solve this with next HQL query:

from A
where
exists(
from A1
where A1.id = A.id
)
or exists(
from A2
where A2.id = A.id
)
and not exists(
from A3
where A3.id = A.id
)

The problem is that this query is very heavy, i need better performance.

Can you help me ?

regards
epsino

1- what about
from A1

then

from A2

?

2- are you using discriminator strategy? if yes, check class keyword in the reference guide

3-

should work?

1. This solutions is not sufficient for me.

2. Are you using discriminator strategy? if yes, check class keyword in the reference guide

I use discriminator strategy, but i don't know how to use it with HQL.

3. This solution not work.

Thank you for all...

regards
epsino

Thank you !!!

I found how to use class keyword in HQL. This is the solution that i hope.

Thanks for all Hibernate Team, this is a greate, GREATE ORM.

regards
epsino

please explain me what is the error, i use something like this i should work

You can do amazingly fast queries on hierarchies if you use the nested set theory.

See here:

http://www.intelligententerprise.com/00 ... o1_1.jhtml

With this method, you can for intance, get all children of a parent in a single SQL statement.

I have implemented this completely in hibernate if you need any help.

when I said children, I meant descendants by the way, so for instance, if you have a hierarchy with 1000 nodes, the nested set way of doing things allows you to find all descendants of, say, the root node, in one SQL statement.

3. This solution not work.

please explain me what is the error, i use something like this i should work

I probe it, and not happend an error, but the result is not the expected result. The result are empty. Maybe i probe it wrong... i test it and reply to you later...

regards
epsino

I would be interested in knowing how exactly you implemented this

I would be interested too in knowing how you implemented the mapping. I already implemented SQL procedures get insert/remove tree nodes but I'm not sure about the proper way to do the mapping.
TIA, Martin

Found an interesting discussion on various techniques here:

http://www.dbazine.com/oracle/or-articles/tropashko4

Any chance you still have the mapping files around for your implementation of nested sets. It would be much appreciated. I realize the original post is 2 years old, but I am having some trouble mapping the descendants collection.