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From Dzmitry Kazimirchyk <dkazimirc...@gmail.com>
Subject Re: Regarding CAY-1714
Date Thu, 19 Jul 2012 19:52:22 GMT
Hi Eshan,

Sorry for late response on this... Let me describe the problem in more 
details. When committing child context's changes to parent context all 
the child context's objects change their state to COMMITTED and are 
flushed into the parent context without committing to database. In 
parent context these objects will have persistence state NEW.

Then to the problem itself: when accessing object's relationship from 
child context for objects in COMMITTED state Cayenne tries to resolve 
relationship fault, RelationshipQuery is fired and routed up in context 
hierarchy until it will be resolved by some of the parent contexts or if 
not it will go to the top level DataChannel and will be queried from the 
db. So the problem is that when we try to access some not yet faulted 
relationship from child context we will end up trying to route the 
relationship query up which eventually will fail since the object is not 
into db yet.

Attempt to solve this was made already per CAY-1183 and the solution (or 
maybe call it workaround...) was to intercept relationship queries in 
top level context and if object is in persistence state NEW return empty 
result since in this case we don't have valid places left to look up for 
the requested relationship. This solution however doesn't work if object 
was not yet committed to top level context and is in NEW state somewhere 
in between top and bottom contexts. I'm thinking of possibility to 
expand the CAY-1183 workaround to not top level contexts unless we will 
come to some generic solution on this. But of course this will require 
testing and thinking of how it may affect on current workflow...

Please fill free to ask more questions and propose your ideas on how to 
deal with this.

Dima


On 07/18/2012 05:52 PM, Eshan Sudharaka wrote:
> Hi,
>
> Or should it be handle in resolveFromDB method in RelationshipFault class ?
>
> On Wed, Jul 18, 2012 at 3:10 PM, Eshan Sudharaka <esudharaka@gmail.com>wrote:
>
>> Hi,
>>
>> I have gone through the method invocations of this issue.  As mentioned in
>> jira task reason for this is that the parent context is not being committed
>> when last statement is executing.(childMt2.getTable3();)
>>
>> As I see We need  handle this in BaseContext.prepareForAccess method.
>> Inside that we can check objectContext.hasChanges(); boolean value and if
>> it is false only we can continue that flow.  Could you please provide me a
>> feed back for this approach
>>
>>
>>
>> On Mon, Jul 16, 2012 at 5:12 PM, Andrus Adamchik <andrus@objectstyle.org>wrote:
>>
>>> Yes, the API would be the same...
>>>
>>> But good point on usability. We had rather transparent API before, and
>>> then replaced it with what we have now :)
>>>
>>> The reason for this change was to avoid storing context factory and any
>>> other stack singletons in an ObjectContext instance (be it DataContext or
>>> CayenneContext). As ObjectContext is serializable, having lots of extra
>>> "services" as ivars made bootstrapping it back to the stack on
>>> deserialization a rather painful operation. So in order to streamline that
>>> process, some of the earlier conveniences were sacrificed.
>>>
>>> If you think of CayenneRuntime as a "factory of everything" it may not
>>> look so confusing actually... Also maybe we can add a convenience method
>>> CayenneRuntime.getContext(ObjectContext) to avoid a cast.
>>>
>>> Also "getContext(DataChannel)" javadoc is mindlessly cloned from
>>> "getContext()" without explaining the difference and needs to be fixed :)
>>>
>>> Andrus
>>>
>>>
>>> On Jul 16, 2012, at 2:28 PM, Dzmitry Kazimirchyk wrote:
>>>
>>>> What about next level of nesting...
>>>>
>>>> ObjectContext nestedChild = runtime.getContext((DataChannel)
>>> clientContextChild);
>>>> This approach doesn't seem handy or obvious. Is there a better way?
>>>>
>>>> Dima
>>>>
>>>>
>>>> On 07/16/2012 02:11 PM, Andrus Adamchik wrote:
>>>>> The API was refactored, but the nested contexts feature is of course
>>> still present. Right now you'd create a client nested context using
>>> ClientRuntime:
>>>>> ClientRuntime runtime = ..
>>>>> ObjectContext clientContextChild = runtime.getContext(clientContext);
>>>>>
>>>>> Andrus
>>>>>
>>>>> On Jul 16, 2012, at 1:00 PM, Eshan Sudharaka wrote:
>>>>>
>>>>>> Hi,
>>>>>> I was trying to reproduce the issue CAY-1714 and it seems that
>>> following
>>>>>> operation is now invalid. (since CayenneContext has mo such method
>>>>>> declaration)
>>>>>>
>>>>>> ObjectContext clientContext = this.clientContext.createChildContext();
>>>>>>
>>>>>> So is this bug is fixed  now ?
>>>>>>
>>>>>> --
>>>>>> *~Thanks & Regards~*
>>>>>> ***
>>>>>> *
>>>>>> Eshan
>>>>
>>>>
>>>
>>
>> --
>> *~Thanks & Regards~*
>> ***
>> *
>> P.A.Eshan Sudharaka
>> Dept of Computer Science and Engineering
>> University of Moratuwa
>> Sri Lanka
>> http://esudharaka.blogspot.com/
>>
>>
>



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