When I try to end a process instance with DBID_ = 9, an exception as flows is thrown:

Hibernate:
/* delete org.jbpm.jpdl.internal.model.JpdlExecution */ delete
from
JBPM4_EXECUTION
where
DBID_=?
and DBVERSION_=?
[http-8080-Processor25] 19:24:49 ERROR (JDBCExceptionReporter.logExceptions:101) - Cannot delete or update a parent row: a foreign key constraint fails (`jbpm4_execution`, CONSTRAINT `FK_EXEC_INSTANCE` FOREIGN KEY (`INSTANCE_`) REFERENCES `jbpm4_execution` (`DBID_`))
[http-8080-Processor25] 19:24:49 ERROR (AbstractFlushingEventListener.performExecutions:324) - Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: could not delete: org.jbpm.jpdl.internal.model.JpdlExecution#9
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:94)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:2569)
at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:2725)
at org.hibernate.action.EntityDeleteAction.execute(EntityDeleteAction.java:97)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:263)
at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:172)
at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1027)
at org.jbpm.pvm.internal.tx.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:79)
at org.jbpm.pvm.internal.svc.EnvironmentInterceptor.execute(EnvironmentInterceptor.java:54)
at org.jbpm.pvm.internal.svc.RetryInterceptor.execute(RetryInterceptor.java:55)
at org.jbpm.pvm.internal.svc.ExecutionServiceImpl.endProcessInstance(ExecutionServiceImpl.java:113)
...

The row to be deleted in table jbpm4_execution has data:

9, 'jpdl', 1, 'request_vacation', 'vacation2-1', b, '', '', 'vacation2.9', 'active-root', '', 0, 4, , 9, , ,

It seems column PROCESS_ has value 9 which self references current row with foreign key K_EXEC_INSTANCE.

but MySQL can not delete this row with SQL:
/* delete org.jbpm.jpdl.internal.model.JpdlExecution */ delete
from
JBPM4_EXECUTION
where
DBID_=?
and DBVERSION_=?