MetaDataInheritanceComparator is not transitive; C > B > A > C leads to
out-of-memory crash in PCEnhancer
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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
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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