[OPENJPA-2246] when using fetchplans a different entitymanager may incorrectly eagerly fetch a lazy association

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.1.1, 2.2.0
• Component/s: jpa, performance
• Assignee: Unassigned
• Reporter: Vermeulen
• Created: 03/Aug/12 14:12
• Updated: 03/Aug/12 14:13

Description

Setting a FetchPlan on an entitymanager which loads a certain @OneToMany field that is marked as lazy and cascade all, can result in a different entityManager (created by the same factory) to eagerly fetch this field, even if the field is not in the fetchplan of this different entityManager.

I found two situations where this occurs (each step uses a different entityManager with a transaction):
1.

• em.merge a new entity (and cascaded related entity) with fetchgroup added
• find entity with no fetchgroup added
  -> the lazy-fetched field is incorrectly loaded
  2.
• em.persist a new entity (and cascaded related entity) with NO fetchgroup added
• find entity with fetchgroup added
• find entity with NO fetchgroup added
  -> the lazy-fetched field is incorrectly loaded

The weird thing is that persist and merge behave inconsistently - isn't that great, an inconsistency within an inconsistency? - because switching persist/merge results in the following situations that work as expected:
1.

• em.persist a new entity (and cascaded related entity) with fetchgroup added
• find entity with no fetchgroup added
  -> the lazy-fetched field is a null reference (expected)
  2.
• em.merge a new entity (and cascaded related entity) with NO fetchgroup added
• find entity with fetchgroup added
• find entity with NO fetchgroup added
  -> the lazy-fetched field is a null reference (expected)

Checking the trace and generated SQL confirms that the field that should not be fetched is in fact fetched.
I think this is a bug because this is both inefficient and is inconsistent because I wish my data access to behave predictably.

Note that turning on <property name="openjpa.DetachState" value="fetch-groups" /> in persistence.xml solves the issues but internally OpenJPA still performs the eager fetch.