>If every time OQL hit the database, why after I changed the records in the
>database externally, OQL returns wrong results (count is right, value
inside
>the object is wrong)?
>And will the result update the JDO cache ?
No. Castor does not let you to see dirty read.
The result is right, but your expectation is not right.
>I guess it
>does not, after OQL results showing on the screen, if I pick up one to
>update through db.load() ( db.load() by id will get the object from the JDO
>cache ),
Castor will return the same instance as returning from the first load.
No, it is not a new instance that has the same data as cache.
>then I got ObjectModifiedException. Maybe that is the reason. All
>above is with default cache type.
>
>Maybe it is totally my design issue, if I use Castor, I'd better not touch
>db externally.
You shouldn't modify any row that loaded by Castor, especially if you modify
the loaded object as well.
If you do modify it, you should expect ObjectModifiedException. It is how
reference integrity can be enforced.
Also, what you're doing will result in two connections being acquired for
the same transaction (one by Castor, antoher by the "external"). Although in
theory it should work, providing that the same row will NOT modified by two
connections in the same transaction, but it is not case in reality for most
TransactionManager.
Thomas
>thank you.
>
>Regards
>------------
>Zhongling "Alex" Li
>
>
>-----Original Message-----
>From: Thomas Yip [mailto:[EMAIL PROTECTED]]
>Sent: Tuesday, October 16, 2001 2:02 PM
>To: [EMAIL PROTECTED]
>Subject: Re: [castor-dev] Concurrent transaction problem. Help !
>
>
>
>
>
>
>-----Original Message-----
>>From: Li, Alex [mailto:[EMAIL PROTECTED]]
>>Sent: Tuesday, October 16, 2001 1:30 PM
>>To: [EMAIL PROTECTED]
>>Subject: Re: [castor-dev] Concurrent transaction problem. Help !
>>
>>We got the same problems here, WebLogic 6.1 + Oracle 8.1.7 + CVS Castor
jar
>>( 10/12/2001 )
>>
>>With Castor-0.9.3.jar ( official release ), there are even more problems,
I
>>have to mention that because I hope you guys can figure out what changes
>>made it better while still not stable.
>>
>>Initial problem is: Castor could not use the Connection Pool which is
using
>>WebLogic OCI driver, even I set the jdo-config database type to "generic".
>>With WebLogic OCI driver, lots of weired things will happen, executing the
>>same OQL first time return the correct resultset, then it keeps on
>returning
>>only one record. After we switched to Oracle OCI driver, seems Castor
works
>>fine at first.
>
>We never tried WebLogic OCI.
>However, we did succeed with Castor with Tyrex, after workarounds and bug
>fixes.
>
>In our experience, not that much can be done in the Castor side.
>In fact, the Castor connection mechanism is pretty simple.
>Get a connection when the getDatabase is created, use the connection and
>close it and commit or rollback it at the end.
>
>>Then we found randomly ( 1 in 3-4 times ), Castor throws
>>"org.exolab.castor.jdo.ObjectModifiedException: Transaction aborted:
Object
>>of type ABC with identity 132 has been modified by a concurrent
transaction
>>", no matter it is Connection Pool or not. I am pretty sure there is no
>>other transaction going on, especially in stand-alone test.
>>
>>Then I updated my Castor with CVS version. All stand-alone tests passed,
>>even loop several hundred times. While, the Connection Pool still is bad.
>I
>>tried to set cache-type to all kinds, does not work out, finally I keep it
>>default. Problem happens randomly, but if I touch the db externally, 100%
>it
>>will happen.
>>
>>Is that true that every OQL will hit the database ? Seems not in
Connection
>>Pool env, after I changed some records, OQL gives me back very strange
>>resultset, part of the them are correct, part are not. Like the count is
>>correct, while the field values of each object seems wrong. Then, if I try
>>to update one of them ( no matter long tx or short tx ), definitely it
>gives
>>back ObjectModifiedException.
>
>Yes. It does. If you are using hasMoreElements(), nextElement() pair to
>iterate the QueryResults,
>then try hasMore() and next() pair, because those give you errors message.
>
>>I heard Oracle OCI driver is not thread safe, that is the reason why
>>WebLogic comes out with its OCI driver, even shipped inside weblogic.jar.
>>Sadly, Castor does not work with it. Is this the problem?
>>
>>Please help, we are going to production this week. If I still can not fix
>>it, I have to throw away Connection Pool.
>
>
>
>
>
>Thomas
>
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