Hello,
we use hibernate, oracle and pessimstic locking, to avoid concurrent modification through different threads.
This worked fine for a while. But now we sometimes get deadlocks. We analyzied and found the cause.
Our mapping:
Code:
<class name="TraceObject" table="TraceObjects">
<cache usage="read-write" />
<id name="objectId" column="objectId" type="long">
<generator class="native">
<param name="sequence">TraceObjectsSeq</param>
</generator>
</id>
<timestamp name="dbVersionControl" />
...
</class>
<joined-subclass name="VehicleObject" table="VehicleObjects" extends="TraceObject">
<key column="id" />
...
</joined-subclass>
In thread A we retrieve the vehicleObject through Criteria:
Code:
criteria.setLockMode(LockMode.UPGRADE);
criteria.uniqueResult();
This results in a select statement with
FOR UPDATE OF TraceObjects.objectId. This only locks the relevant data in table TraceObjects.
In thread B we retrieve the vehicleObject through Session:
Code:
getSession().get(getPersistentClass(), ao_Id, LockMode.UPGRADE);
This results in a select statement with
FOR UPDATE. This locks the relevant data in table TraceObjects and joined table VehicleObjects.
We think, our problem are the different deepnesses of the locks.
Is there a way to create locks on criterias just with "FOR UPDATE" not with "FOR UPDATE OF"? Does anybody know, why the locking from session and from criteria works different?
Login
FAQ
Search