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

     [ https://issues.apache.org/jira/browse/OPENJPA-2246?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vermeulen updated OPENJPA-2246:
-------------------------------

    Attachment: openjpalazyeagerfetchplan.zip

Added a complete test case (build with Maven) which shows this bug.
                
> 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: 2.1.1, 2.2.0
>            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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