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From "Musall, Maik" <m...@selbstdenker.ag>
Subject Re: Creating a fault for an ObjectId
Date Wed, 15 Feb 2017 17:49:06 GMT
Hi Michael,

that's an interesting idea, thank you. That could work. I'll think about it.

Maik


> Am 15.02.2017 um 16:31 schrieb Michael Gentry <blacknext@gmail.com>:
> 
> Hi Maik,
> 
> Would it be possible to use child DataContexts and then push the changes up
> to the parent?
> 
> 
> On Wed, Feb 15, 2017 at 11:17 AM, Musall, Maik <maik@selbstdenker.ag> wrote:
> 
>> The use case is as follows.
>> 
>> I have a large collection of objects which I want some function to be
>> executed on. I want to use multiple threads to do this, so AFAIK I have to
>> use separate ObjectContexts per thread like in EOF. So, I will then
>> instantiate those objects in the per-thread contexts, do the processing,
>> but then the wrapper function should return the entire collection of
>> processed objects in the original context that they were in at the
>> beginning.
>> 
>> With EOF, I have a snapshot cache that will contain the changed
>> attributes, but the EO instances in the original context have their
>> original values. So, I will then call ec.faultForGlobalID() to have them
>> refaulted from the snapshot cache, avoiding to refetch 100.000 objects from
>> db.
>> 
>> I suppose using a shared cache would make the problem obsolete, as those
>> objects would receive changed attributes automatically, but I'm still on
>> the fence whether or not to use a shared cache, because it's a major
>> behavioural difference to EOF and I still have to think about that while
>> migrating my project.
>> 
>> Maik
>> 
>> 
>>> Am 15.02.2017 um 15:49 schrieb Ken Anderson <ken.anderson@amphorainc.com
>>> :
>>> 
>>> Yes, use the objectID to pass around, but on the receiving end, you
>> should turn it into a fault and release it into the wild.  Then, if some
>> code needs it, the fault fires, otherwise – no DB activity.
>>> 
>>> Ken Anderson
>>> CTO Amphora, Inc.
>>> Mobile:   +1 914 262 8540
>>> 
>>> 
>>> 
>>> www.amphorainc.com <http://www.amphorainc.com/>
>>> 
>>> 
>>> 
>>> 
>>> On 2/15/17, 10:47 AM, "Amedeo Mantica" <amedeomantica@me.com> wrote:
>>> 
>>>   I would just use the ObjectId
>>> 
>>>> On 15 Feb 2017, at 16:45, Hugi Thordarson <hugi@karlmenn.is> wrote:
>>>> 
>>>> It can be useful in some cases—one example is if you want to be able to
>> pass objects around in an API without triggering a DB fetch unless they are
>> actually used.
>>>> 
>>>> Cheers,
>>>> - hugi
>>>> 
>>>> 
>>>>> On 15. feb. 2017, at 15:28, Amedeo Mantica <amedeomantica@me.com>
>> wrote:
>>>>> 
>>>>> no worries, but I cannot understand your goal, why do you want to get
>> the fault ?
>>>>> 
>>>>>> On 15 Feb 2017, at 16:25, Hugi Thordarson <hugi@karlmenn.is>
wrote:
>>>>>> 
>>>>>> Thanks Ken, but the immediate fetch performed by Cayenne.objectForPk
>> is precisely what I’d like to avoid.
>>>>>> 
>>>>>> Cheers,
>>>>>> - hugi
>>>>>> 
>>>>>> S: Amedeo, sorry about calling you “Amadeo” in my last post.
I have
>> been properly lambasted.
>>>>>> 
>>>>>> 
>>>>>>> On 15. feb. 2017, at 15:20, Ken Anderson <
>> ken.anderson@amphorainc.com> wrote:
>>>>>>> 
>>>>>>> I do this:
>>>>>>> 
>>>>>>> dataObject = (DataObject) Cayenne.objectForPK(getObjectContext(),
>> MyEntity.class, oid);
>>>>>>> 
>>>>>>> But it will do the fetch if it’s not already in cache.
>>>>>>> 
>>>>>>> Ken
>>>>>>> 
>>>>>>> Ken Anderson
>>>>>>> CTO Amphora, Inc.
>>>>>>> Mobile:   +1 914 262 8540
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> www.amphorainc.com <http://www.amphorainc.com/>
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> On 2/15/17, 9:59 AM, "Hugi Thordarson" <hugi@karlmenn.is>
wrote:
>>>>>>> 
>>>>>>> Thanks Amadeo, but I ended up creating a method that looks like
>> this. It would be nice to get some feedback on it, if I’m violating any
>> Cayenne Commandments.
>>>>>>> 
>>>>>>> /**
>>>>>>> * @return An existing object or fault if registered with the
OC,
>> otherwise creates a new hollow object based on the given ObjectId.
>>>>>>> */
>>>>>>> public static Persistent faultForObjectId( ObjectContext oc,
>> ObjectId objectId ) {
>>>>>>> Persistent object = (Persistent) oc.getGraphManager().getNode(
>> objectId );
>>>>>>> 
>>>>>>> if( object == null ) {
>>>>>>> ClassDescriptor descriptor = oc.getEntityResolver().
>> getClassDescriptor(objectId.getEntityName());
>>>>>>> 
>>>>>>> object = (Persistent) descriptor.createObject();
>>>>>>> 
>>>>>>> object.setPersistenceState(PersistenceState.HOLLOW);
>>>>>>> object.setObjectContext(oc);
>>>>>>> object.setObjectId(objectId);
>>>>>>> 
>>>>>>> oc.getGraphManager().registerNode(objectId, object);
>>>>>>> }
>>>>>>> 
>>>>>>> return object;
>>>>>>> }
>>>>>>> 
>>>>>>> Cheers,
>>>>>>> - hugi
>>>>>>> 
>>>>>>> 
>>>>>>>> On 15. feb. 2017, at 14:41, Amedeo Mantica <amedeomantica@me.com>
>> wrote:
>>>>>>>> 
>>>>>>>> may be you want invalidateObject ?
>>>>>>>> 
>>>>>>>>> On 15 Feb 2017, at 14:15, Hugi Thordarson <hugi@karlmenn.is>
>> wrote:
>>>>>>>>> 
>>>>>>>>> Hi all,
>>>>>>>>> I need to get a fault for an ObjectId from an ObjectContext.
How
>> would I do this?
>>>>>>>>> 
>>>>>>>>> I don’t see any public API for this—the implementation
of
>> createFault in CayenneContext seems to get me halfway there, but it will
>> not return an existing fault, only create new ones.
>>>>>>>>> 
>>>>>>>>> Cheers,
>>>>>>>>> - hugi
>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
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>>>>>> 
>>>>> 
>>>> 
>>> 
>>> 
>>> 
>>> Confidentiality Notice: This e-mail and accompanying documents contain
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>> 


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