[rules-dev] persistence and optimistic locking

[Mark Proctor]

Some Guy wrote:
> All that should be required is to define a version or timestamp 
> property for the entity in question.  Hbn will constrain against that 
> field when it performs the update.  If the db returns 0 updated rows, 
> then Hbn will throw the stale exception. 
That's what I thought and did, but wasn't that simple. I think it's 
because our persistence approach isn't too friendly with EJB.
>
> I recall there's a way to pessimistically lock using db locks (select 
> for update, etc.), but I assume that's only valid for the duration of 
> your transaction.  I never had call to use it.
>
> If you use timestamps, make sure your db columns have millisecond 
> resolution.
>
> On Nov 12, 2009, at 10:18 PM, Mark Proctor <mproctor at codehaus.org 
> <mailto:mproctor at codehaus.org>> wrote:
>
>> Michael Neale wrote:
>>> I am not aware of peasimistic locking use being very common. When  
>>> people want it, it's generally cause the GUI suggests it (eg bob wants  
>>> to view a file, but Alice has it locked)
>>>
>>>   
>> With optimistic locking we can just submit our update and it fails if 
>> something else updted the recorded in the mean time - doing a counter 
>> comparison. With pessemistic we have to download the record first, 
>> compare them, and then upload. As what we are comparing in a binary 
>> blob, we want to avoid pulling that from the db.
>>
>> Mark
>>> Sent from my phone.
>>>
>>> On 13/11/2009, at 10:27 AM, Salaboy <salaboy at gmail.com <mailto:salaboy at gmail.com>> wrote:
>>>
>>>   
>>>> I suppose that the versión field its being used. So, the default must
>>>> be optimistic
>>>>
>>>> - Ing. Mauricio Salatino -
>>>>
>>>> On Nov 12, 2009, at 9:43 PM, Michael Neale <michael.neale at gmail.com <mailto:michael.neale at gmail.com>>
>>>> wrote:
>>>>
>>>>     
>>>>> I thought optimistic locking was the default ? Or do you mean you  
>>>>> know
>>>>> how to switch, just that it doesn't work?
>>>>>
>>>>>
>>>>> Sent from my phone.
>>>>>
>>>>> On 13/11/2009, at 8:16 AM, Salaboy <salaboy at gmail.com <mailto:salaboy at gmail.com>> wrote:
>>>>>
>>>>>       
>>>>>> I Will take a look on that
>>>>>> Sent from my iPhone
>>>>>>
>>>>>> On Nov 12, 2009, at 7:33 PM, Mark Proctor <mproctor at codehaus.org <mailto:mproctor at codehaus.org>>
>>>>>> wrote:
>>>>>>
>>>>>>         
>>>>>>> Any hibernate guru's out there? Currently the persistence stuff  
>>>>>>> uses
>>>>>>> pessematic locking, which is slow, in theory we should be using
>>>>>>> optimistic locking, but I couldn't get it to work. Anyone want to
>>>>>>> give
>>>>>>> that a go?
>>>>>>>
>>>>>>> Mark
>>>>>>>
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