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Posted to ojb-user@db.apache.org by Laran Evans <la...@elevasoft.com> on 2005/08/18 19:20:29 UTC

optimistic locking problems

I'm getting optimistic lock exceptions when saving an object. But, the
exception only comes up occasionally. It happens maybe 3 out of every 4
runs.

 

The object has 3 lists of objects, all of which are persisted as well.
Before saving the parent object all version numbers are null. After saving
1) the parent object and all elements of two of the collections have a
version number of 1. 2) the elements of the third collection have version
numbers of 2.

 

Can anyone spot from my simple description any potential optimistic locking
issues?

 

Many thanks,

- laran

Re: optimistic locking problems (P6Spy question)

Posted by Vamsi Atluri <vk...@yahoo.com>.

Hello all,

Sorry to hijack the thread into a question about P6Spy. The P6Spy document
that Armin pointed out here says that we have to modify the "driver"
parameter in the "jdbc-connection-descriptor" of the repository.xml file.
However, I have a managed environment (WSAD/WAS) wherein I do not specify
the driver in the repository.xml file. More specifically, my connection
descriptor is like this:

<jdbc-connection-descriptor 
		jcd-alias="OJBDb" 
		default-connection="true" 
		platform="Db2" 
		jdbc-level="1.0" 
		jndi-datasource-name="jdbc/ojbDataSource"		
		username="*****" 
		password="*****" 
		batch-mode="false" 
		useAutoCommit="1" 
		ignoreAutoCommitExceptions="false">
		<sequence-manager
className="org.apache.ojb.broker.util.sequence.SequenceManagerNativeImpl">
		    <attribute attribute-name="grabSize"
attribute-value="1"></attribute>
		</sequence-manager>
	</jdbc-connection-descriptor>

Since I am using jndi-datasource-name, I didn't have to specify the
driver. How do I use P6Spy in such cases? Do I just add an additional
parameter for driver? Any help is appreciated. Thank you.

Regards,
-Vamsi


> Did you
> 
> > check the generated sql statements, e.g. via P6Spy (jar is shipped
> with 
> > OJB)?
> > http://db.apache.org/ojb/docu/faq.html#traceProfileSQL
> > 
> > 
> > regards,
> > Armin
> > 

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Re: optimistic locking problems

Posted by Laran Evans <la...@elevasoft.com>.

The problem turned out to be a sequence which had recently been reset in 
an external database.

But, I had forgotten about P6spy. So thanks for that reminder.

- laran

Armin Waibel wrote:
> Hi Laran,
> 
> Laran Evans wrote:
> 
>> I'm getting optimistic lock exceptions when saving an object. But, the
>> exception only comes up occasionally. It happens maybe 3 out of every 4
>> runs.
>>
>>  
>>
>> The object has 3 lists of objects, all of which are persisted as well.
>> Before saving the parent object all version numbers are null. After 
>> saving
>> 1) the parent object and all elements of two of the collections have a
>> version number of 1. 2) the elements of the third collection have version
>> numbers of 2.
>>
> 
> Maybe OJB does perform the objects of the third collection twice (insert 
> + update). Could you post the (pseudo) code of your test case? Did you 
> check the generated sql statements, e.g. via P6Spy (jar is shipped with 
> OJB)?
> http://db.apache.org/ojb/docu/faq.html#traceProfileSQL
> 
> 
> regards,
> Armin
> 
>>  
>>
>> Can anyone spot from my simple description any potential optimistic 
>> locking
>> issues?
>>
>>  
>>
>> Many thanks,
>>
>> - laran
>>
>>  
>>
>>
> 
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Re: optimistic locking problems

Posted by Armin Waibel <ar...@apache.org>.

Hi Laran,

Laran Evans wrote:
> I'm getting optimistic lock exceptions when saving an object. But, the
> exception only comes up occasionally. It happens maybe 3 out of every 4
> runs.
> 
>  
> 
> The object has 3 lists of objects, all of which are persisted as well.
> Before saving the parent object all version numbers are null. After saving
> 1) the parent object and all elements of two of the collections have a
> version number of 1. 2) the elements of the third collection have version
> numbers of 2.
> 

Maybe OJB does perform the objects of the third collection twice (insert 
+ update). Could you post the (pseudo) code of your test case? Did you 
check the generated sql statements, e.g. via P6Spy (jar is shipped with 
OJB)?
http://db.apache.org/ojb/docu/faq.html#traceProfileSQL


regards,
Armin

>  
> 
> Can anyone spot from my simple description any potential optimistic locking
> issues?
> 
>  
> 
> Many thanks,
> 
> - laran
> 
>  
> 
> 

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