Transaction Lock method

[bin]

Hi Sir,

I used the following code to update a set of regions and in the same time no one can have read access to them

IQueryable<Region> result = from q in objScope.Extent<Region>() select q;
            List<Region> list = result.ToList();
            objScope.TransactionProperties.Concurrency = TransactionMode.PESSIMISTIC_EXPLICIT;
            objScope.Transaction.Lock(list, LockMode.READ);
            objScope.Transaction.Begin();
            list[0].RegionDescription = "Eastern";
            blprovider.CommitTransaction();

I got the following exception :

Telerik.OpenAccess.Exceptions.InvalidOperationException was unhandled
  Message=The supplied instance is not of type Telerik.OpenAccess.SPI.dataobjects.PersistenceCapable (System.Collections.Generic.List`1[[Entity.Region, Entity, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]). Are you trying to add a wrong object or is the assembly not enhanced?
  Source=Telerik.OpenAccess.Runtime
  CanRetry=true
  StackTrace:
       at OpenAccessRuntime.DataObjects.OpenAccessPersistenceManagerImp.checkPersCapable(Object o)
       at OpenAccessRuntime.DataObjects.OpenAccessPersistenceManagerImp.pmPreCheck(Object pc)
       at OpenAccessRuntime.DataObjects.OpenAccessPersistenceManagerImp.retrieveImp(Object o, FetchPlanIF fPlan, RetrieveFetchContext rContext)
       at OpenAccessRuntime.DataObjects.OpenAccessPersistenceManagerImp.retrieveAllImp(Object[] objects, Boolean useFetchPlan)
       at OpenAccessRuntime.DataObjects.OpenAccessPersistenceManagerImp.retrieve(Object o, Boolean useFetchPlan)
       at OpenAccessRuntime.DataObjects.OpenAccessPersistenceManagerImp.retrieve(Object o)
       at OpenAccessRuntime.DataObjects.SynchronizedPMProxy.retrieve(Object o)
       at Telerik.OpenAccess.RT.TransactionImpl.Lock(Object target, LockMode lm)
   .............
    ........... paths to local folders
................
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: System.InvalidCastException
       Message=Specified cast is not valid.
       InnerException:

[Jan Blessenohl]

Hi bin,
PerstsinceCapable is the interface all your persistent classes get from the enhancer.

You cannot pass in a list but only single persistent objects. You have to call lock inside the txn boundary, please move the call behind the begin.

Regards,
Jan Blessenohl
the Telerik team

[bin]

Hi Sir,
I modified my code as you told me before. As multiple threads sharing the same ObjectScope is not supported in OpenAccess, the  GetNewObjectScope method returns a new objectscope object for each thread. I used the following code in  multiple threads to increase the RegionID by one and to achieve this i have to set a lock read access on the last record in the region table then after i add a new Region i commit the transaction.

private void ThreadOperation()
       {
           IObjectScope objectScope = GetNewObjectScope();
           objScope.TransactionProperties.Concurrency = TransactionMode.PESSIMISTIC_EXPLICIT;
           objScope.Transaction.Begin();
           Region r = (from q in objScope.Extent<Region>() select q).Last();
           objScope.Transaction.Lock(r, LockMode.READ);
           Region region = new Region();
           region.RegionID = r.RegionID + 1;
           region.RegionDescription = r.RegionDescription + r.RegionID.ToString();
           objScope.Add(region);
           objScope.Transaction.Commit();
       }

I got the following exception :

EXCEPTION : Telerik.OpenAccess.RT.sql.SQLException: Violation of PRIMARY KEY constraint 'PK_Region'. Cannot insert duplicate key in object 'dbo.Region'. The duplicate key value is (13). The statement has been terminated. at Telerik.OpenAccess.RT.Adonet2Generic.Impl.PreparedStatementImp.execute() at OpenAccessRuntime.Relational.conn.PooledPreparedStatement.execute() at OpenAccessRuntime.Relational.RelationalStorageManager.generateInserts(NewObjectOID oid, Int32 index, ClassMetaData cmd, PersistGraph graph, Int32[] fieldNos, CharBuf s, Object[] oidData, IntArray toUpdateIndexes)

could you till me please how can i do it ???

Thanks

[Jan Blessenohl]

Hello bin,
First, you cannot be sure that the query.Last returns the object with the highest id, please add an order by to have a fix ordering.
Second why can't you use the autoinc or highlow key generator functionality instead of doing it by yourself?

Kind regards,
Jan Blessenohl
the Telerik team

[bin]

Hi Sir,
I did all what you told me to do and I added the recursive method CheckID  to ensure that I am getting the last ID and i got the same error .

private void ThreadOperation()

       {

           IObjectScope objectScope = GetNewObjectScope();

           objScope.TransactionProperties.Concurrency = TransactionMode.PESSIMISTIC_EXPLICIT;

           objScope.Transaction.Begin();

           Region r = (from q in objScope.Extent<Region>().OrderBy(t => t.RegionID) select q).Last();

           objScope.Transaction.Lock(r, LockMode.READ);

           Region region = new Region();

           region.RegionID = CheckID(r.RegionID);

           region.RegionDescription = r.RegionDescription + r.RegionID.ToString();

           objScope.Add(region);

           objScope.Transaction.Commit();

       }



       private int CheckID(int ID)

       {

           IObjectScope objectScope = GetNewObjectScope();

           Entity.Region r = (from q in objScope.Extent<Region>().Where(t => t.RegionID == ID) select q).FirstOrDefault();

           if (r != null)

           {

               ID += 1;

               CheckID(ID);

           }

           return ID;

       }

I changed the LockMode to LockMode.WRITE  and i also got the same error.
What is the autoinc or highlow key generator functionality ? how can i use it ???

Thanks

[Jan Blessenohl]

Hello bin,
The problem is that if you want the last object, maybe you get the one before if the last is locked. I have attached a project showing autoinc and highlow behavior.

Greetings,
Jan Blessenohl
the Telerik team