[rules-dev] persistence and optimistic locking

[Some Guy]

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.

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>  
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> 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>
>>> 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> 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>
>>>>> 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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