Bug 331064

Description john.vandale 2010-11-24 16:47:37 EST

Build Identifier: 

Deadlocks can occur when trying to delete a collection of objects using
uow.deleteObject(objectToBeDeleted). In this reported use case the mapping of this object is one table without any relationship. The primary key is set in all objectToBeDeleted instances.

It is impossible to have a deterministic order for generated
delete SQL. DELETE is executed neither in the order in which the application calls deleteObject or in a PK value ordered fashion.
Deadlocks may occur when concurrent delete/update are executed on the database.

Whether or not a deadlock occurs a non-ordered delete sequence occurs every time.

Reproducible: Sometimes

Steps to Reproduce:
Write an application which deletes objects e.g.:

long[] ids = {800, 801, 802, 803, 804, 805, 806, 807, 808, 809};
UnitOfWork uow = getSession().acquireUnitOfWork();   
uow.setShouldOrderUpdates(true);

for (int i = 0; i < ids.length; i++) {
    Employee employee = new Employee();
    employee.setId(new java.math.BigDecimal(ids[i]));
    Employee registeredEmployee = (Employee) uow.registerExistingObject(employee);
    uow.deleteObject(registeredEmployee);    
   }

uow.commit();

You will see the deletes seem to be in a random order e.g.:

DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [804]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [806]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [808]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [807]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [802]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [800]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [803]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [801]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [809]
DELETE FROM EMPLOYEE  WHERE (CNT_ID = ?)bind => [805]