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Hi Yiping,
thanks for the feedback.
in the AdvancedQueryTestSuite, I had to find a solution for the following
issue:
when tx1 places a pessimistic lock, I am using an
*exclusive* lock on MaxDB. This later blocks em2.find before tx2 can even atempt
to lock. To avoid blocking of tx2, I replaced em2.find by a query and rearanged
this before tx1.lock. While this avoids the deadlock,I am losing the assertion
that em2.find is non-blocking.
Ideally, I would place a *shared* read lock as lock mode READ is specified, which
would not block em2.find. However, I am under the impression that the
distinction between PESSIMISTIC_READ locks and PESSIMISTIC_WRITE locks cannot be
made in the database platform. Hence I am propagating the READ lock to a WRITE
lock (which is in agreement with the spec).
-Adrian
Hi Adrian,
Sorry for the late reply, I saw the email too
late until yesterday late afternoon.
I think the changes are OK, you
simplified the PessimisticLockingExtendedScopeTestSuite.java a lot, that's
great. For the changes in AdvancedQueryTestSuite.java, you changed the
sequences of entities operations, I am not sure if that will do same thing as
the original one:
Original:
starts tx1; tx1 does query and sets lock mode using
query.setLockMode() for read lock, modifies entity;
starts
tx2; tx2 reads entity, locks it using em with 0 timeout and updates, lock
can't be obtained and results in transaction-level rollback and throws
PessimisticLockException
Yours:
starts tx1; starts tx2, tx2 reads entity,
tx1 reads and modifies entity, locks it as read lock and updates; tx2 locks
entity and updates
Maybe Gordon can confirm
that.
Thanks,
Yiping
Yiping, Gordon, all,
Some tests of PessimisticLockingExtendedScopeTestSuite and
AdvancedQueryTestSuite are deadlocking on MaxDB.
Moreover, it turned out that pessimistic lock scope EXTENDED was not
locking properly on MySQL.
I am proposing a patch for these issues:
Could you please have a look?
Thanks and regards,
Adrian
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