NH-2715 - Lazy="proxy" does eager load on one-to-one relation through PK

[nhibernate-bot]

Boyan Trushev created an issue — 19th May 2011, 1:33:31:

Hi,

This is a follow-up of the problem I described in #NH-2704. There I found that when one-to-one relation is through FK the related property is eagerly loaded. I have been told that this is an expected behavior for one-to-one relation through FK, so I decided to examine also the case when the one-to-one relation is through PK. I have found the same problem there too. It can be easily reproduced with the LazyOneToOne test case. You just have to change lazy="no-proxy" to lazy="proxy" for Employee property of the Person class and for Person property of Employee class in Person.hbm.xml and run the Lazy() test. You'll notice that both the person and it's employee property are loaded on:

p = s.CreateQuery("from Person where name='Gavin'").UniqueResult<Person>();

And on the next line the test fails as the Employee property was already loaded:

Assert.That(!NHibernateUtil.IsPropertyInitialized(p, "Employee"));

[fredericDelaporte]

Similarly to #806, a nullable one-to-one cannot know without querying the associated table whether it exists or not, thus for loading its proxy it is required to query the associated table. From that point, it has up to now been consider in past discussions (other similar Jira tickets) to be better to query the whole state rather than just the key, thus the eager load.

The lazy="no-proxy" exists just for that reason, allowing to actually eager load such association cases.

Maybe mapping lazy="proxy" in such case should have raised an error at mapping compilation time (something like "lazy proxy option is invalid on one-to-one non-constrained side, use no-proxy or false instead"), but it was instead chosen to silently ignore such setting instead. Changing that would now be a major breaking change.

[hazzik]

The assert here is invalid, but the concern is valid. The assert should be instead:

Assert.That(NHibernateUtil.IsInitialized(p.Employee), Is.False);

[hazzik]

I would reopen this issue to season it for a few more years.