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From "Vermeulen (JIRA)" <j...@apache.org>
Subject [jira] [Created] (OPENJPA-2246) when using fetchplans a different entitymanager may incorrectly eagerly fetch a lazy association
Date Fri, 03 Aug 2012 14:14:02 GMT
Vermeulen created OPENJPA-2246:
----------------------------------

             Summary: when using fetchplans a different entitymanager may incorrectly eagerly
fetch a lazy association
                 Key: OPENJPA-2246
                 URL: https://issues.apache.org/jira/browse/OPENJPA-2246
             Project: OpenJPA
          Issue Type: Bug
          Components: jpa, performance
    Affects Versions: 2.2.0, 2.1.1
            Reporter: Vermeulen
         Attachments: openjpalazyeagerfetchplan.zip

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.

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