Not cascaded OneToMany association gets refreshed on merge

ge0ffrey · **Joined:** Thu Oct 13, 2005 4:19 am **Posts:** 98

I have a City with a bi-directional @OneToMany association to Person:

Code:

@OneToMany(mappedBy = "city")
@OptimisticLock(excluded = true) // No dirty checking
public List<Person> getPersons()

So there's no cascading.
However when I merge a detached City back into the persistent context, I see it refresh (= select) every detached Person of the detached city.
How can I avoid this?

It has 2 problems:
- It creates an n+1 query problem, which is a big problem for a City with 500+ persons.
- If meanwhile one of those Persons are deleted, it throws an EntityNotFoundException on the merge of the city, while it should just update the properties of the city and don't care about the persons.

Thanks for any and all help :)

Adrian Moos · **Joined:** Wed Nov 21, 2007 8:04 am **Posts:** 27

What about making sure the city's person collection is not initialized? If the person collection is a proxy you shouldn't have the problem.

ge0ffrey · **Joined:** Thu Oct 13, 2005 4:19 am **Posts:** 98

Adrian Moos wrote:

What about making sure the city's person collection is not initialized? If the person collection is a proxy you shouldn't have the problem.

That's not possible, since it's been loading in a single query with "from City city left join fetch city.persons".

Adrian Moos · **Joined:** Wed Nov 21, 2007 8:04 am **Posts:** 27

Quote:

don't care about the persons

Quote:

fetch city.persons

This looks like a contradiction: why fetch data you don't care about?

ge0ffrey · **Joined:** Thu Oct 13, 2005 4:19 am **Posts:** 98

When the user is editing a City, he's also shown a list of the persons in that city.
So the City select does a left join fetch to persons,
after which everything becomes detached,
the user is shown the city with its persons,
changes the city's properties (but can't change the persons list)
and finally the city is merged back into a persistent state.