I am creating a system with order-header and line-item tables. The line-item table has three many-to-one relationships with other tables (such as the Item table).

I expect a very large number of line-items (in the tens of thousands), so I need to optimize the performance of inserts. In order to do this, I have created a stored procedure which returns all the data I need to create the line-items. This data incudes all the IDs of the many-to-one relationships for each line-item.

I had hoped to simply be able to populate these IDs on the line item class, and save the line-item data. For example, I would like to do this:

LineItem.setItem(new Item(itemID);

If I try this, when I attempt to save the record I get:

org.hibernate.TransientObjectException: object references an unsaved transient instance

After some testing, I determined that I need a "real" Hibernate-managed Item instance to make this work. My problem is that I don't need the rest of the Item data. I already have the ID and this is all that needs to be populated in the LineItem table. I would rather not instantiate 10,000 or 20,000 Item instances if I don't need them. I also have two other many-to-one relationships, making this a real problem.

Is there any way around this, other than an HQL insert statement?

I also tried a StatelessSession.

So, the item already exists in the database, but you are using the following code:

LineItem.setItem(new Item(itemID);

Why not:

LineItem.setItem(itemDAO.findById(itemID));

Would that solve the problem?

With LazyLoading, or even just swapping load and get methods on the finder implementation, you can avoid actually loading the associated objects.

Yes, you have understood exactly. Your code would solve the problem. The reason I am looking to avoid this is that for each line-item on my order, I have three associated objects that need to be set. On a 10,000 line order (not uncommon), this would mean that I would perform 30,000 "findById" calls. Even with LazyLoading, this is still a very large number of database lookups that I don't really need, since I already have a valid key for each of these associated objects.

Dears,

I am having the same problem. Did you find any solution.


Thanks
BISO

I re-mapped the object replacing my many-to-one entries with property entries that represent the ID columns of the related objects. By doing so I could set the IDs of the related objects directly into the foreign key columns, without having the non-transient related objects in memory.

This solution is very bad from an ORM perspective, so I really wouldn't recommend it. One problem is that the object became an insert-only object, since it doesn't have the relationships that are needed for selecting all of the data. To get around this, you would have to map other objects to represent the same tables. This would probably lead to coding horrors, etc.

In retrospect, using a native SQL Query for the insert would probably be a much better idea.