OptimisticLockException NOT thrown for entity using Timestamp Version when
update from current persistence contexts
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Key: OPENJPA-359
URL: https://issues.apache.org/jira/browse/OPENJPA-359
Project: OpenJPA
Issue Type: Bug
Components: jdbc
Affects Versions: 1.0.0
Environment: WIntel 32
Reporter: Albert Lee
Priority: Minor
We ran a test using Timestamp as the version field in an entity, the following
(pseudo) test failed when an OptimisticLockException is expected:
em1.persist( e0(pk1) );
e1 = em1.find(pk1);
e2 = em2.find(pk1);
e1.setAttr( "new1");
e2.setAttr( "new2");
em1.merge( e1 );
em2.merge( e2 ); <<<< Expect an OptimisticLockException
The cause of this problem is because the TimestampVersionStrategy.nextVersion
returns a java.sql.Timestamp(System.currentTimeMillis()); In the Wintel
environment, the currentTimeMillis() only has approximately 15ms resolution.
When 2 subsequent Timestamp version objects are requested within this 15ms
interval, both has the same version value. Therefore the em2.merge does not
detected the versions difference between o1 and o2, hence no exception is
thrown.
Due to this behavior, the same test case may failed intermittenly depends on
the currentTimeMillis() resolution and the time when a timestamp version is
created. From some preliminary tests, the resolution for wintel, linux and
z/os are about 15ms, 2ms and 2ms respectively.
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