[jira] Issue Comment Edited: (OPENJPA-258) MetaDataInheritanceComparator is not transitive; C > B > A > C leads to out-of-memory crash in PCEnhancer

["Jonathan Feinberg (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OPENJPA-258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12503952 ] 

Jonathan Feinberg edited comment on OPENJPA-258 at 6/12/07 11:23 AM:
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Attached: An eclipse/AJDT project. When built and run with AspectJ, will instrument the defective comparator and fail fast on detection of cycle. Without AJDT, will run out of memory and die.


 was:
An eclipse/AJDT project. When built and run with AspectJ, will instrument the defective comparator and fail fast on detection of cycle. Without AJDT, will run out of memory and die.

> MetaDataInheritanceComparator is not transitive; C > B > A > C leads to out-of-memory crash in PCEnhancer
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: OPENJPA-258
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-258
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: jpa
>    Affects Versions: 1.0.0
>         Environment: Sun JDK 5, Sun JDK 6
>            Reporter: Jonathan Feinberg
>            Priority: Blocker
>         Attachments: jpa-comparator-bug.zip
>
>
> Comparisons done by MetaDataInheritanceComparator are not transitive. It is possible to have classes A, B, and C such that the comparator simultaneously reports that A > B, B > C, and C > A. Under certain unlucky conditions, this causes the SortedTree holding the metadata resolution buffer to become confused during Red-Black fix, such that it can retrieve a certain element, but not delete it. The "processed" list then grows until heap is exhausted.
> In the enclosed sample project, 
> A < B by name
> B < C by assignable promary key field
> C < A by "levels" from base class (Object)
> If you import the enclosed eclipse project into an AspectJ-enabled eclipse, and refer the AspectJ compiler to an OpenJPA jar file, you'll get the following output:
>   bug.B > bug.A
>   bug.C > bug.B
>   bug.A > bug.C
>   Cycle detected: 
>   bug.A > bug.C > bug.B > bug.A
> The project will work outside of AspectJ, and will exhibit the out of memory condition described above.
> I acknowledge that the enclosed persistence.xml file is not kosher, in that it doesn't list all classes to be instrumented. My own project, affected by this bug, has a correct persistence.xml file. I had to work hard to contrive a simple example, as the order in which classes are buffered affects the appearance of the bug.
> There is no work-around that I know of. I don't believe that the comparator's semantics are well-defined.

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