----- Original Message -----
Sent: Thursday, November 14, 2002 7:33
AM
Subject: [castor-dev] Pleeease help
!!!!!
Hi,
We are in a desperate situation and if there is
no solution to this , it could have serious implications on the project which
we are working on now :-(( . so if anyone knows anyway to solve this please
tell... the lazy loading method suggested by Margaret Martin did not
work.
We have a Doctor class whch is having N-1
relation with a Department class. In our test code when multiple threads tried
to load and update different Doctor objects simultaneously, all but one are
getting LockNotGranted(persis t.deadlock) exceptions. The objects are
loaded in Shared mode and cache-type is set to unlimited. Going through the
castor code our finding is that:
Suppose there are two Doctors Doc1 & Doc2
both belonging to the same Department Dept1.
When a transaction T1 loads Doc1, Doc2 is also
loaded because of its relation with the same Department and thus the T1 gets a
read lock on Doc2 also.
When another concurrent Transaction T2 loads
Doc2, Doc1 is also loaded because of its relation with the same Department and
thus the T2 gets a read lock on Doc1 also.
When T1 requests for a write lock (upgrade using
db.lock()) on Doc1, the request cannot be satisfied immediately as T2 is
having read lock on Doc1
When T2 requests for a write lock (upgrade using
db.lock()) on Doc2, the request is not satisfied as T1 is having read lock on
Doc2, and here a dead lock is detected (in detectDeadLock() method of
ObjectLock.java)
MAPPING.XML
<mapping>
<!-- Mapping for
Department-->
<class name="Department" identity="id"
key-generator="MAX" access="shared" >
<cache-type type="unlimited"
/>
<description>User</description>
<map-to
table="Department" />
<field name="id" type
="long">
<sql name="pk_department_id"
type="bigint"/>
</field>
<field
name="deptName" type="string">
<sql name="deptName"
type="varchar" dirty="check"/>
</field>
<field name="doctors"
type="Doctor" required="false"
collection="arraylist">
<sql
many-key="dept_id"/>
</field>
</class>
<!-- Mapping for Doctor-->
<class
name="Doctor" identity="id" key-generator="MAX" access="shared" >
<cache-type type="unlimited"
/>
<description>Doctor</description>
<map-to
table="doctor" />
<field name="id" type
="long">
<sql name="pk_doctor_id"
type="bigint"/>
</field>
<field
name="userName" type="string">
<sql name="UserName"
type="varchar"
dirty="check"/>
</field>
<field
name="dept" type="Department">
<sql name="dept_id"
/>
</field>
</class>
</mapping>
We are in urgent requirement of a solution
and the we are not in a position to set cache-type to none due to performance
issues.
