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From "Musall, Maik" <m...@selbstdenker.ag>
Subject Re: Creating a fault for an ObjectId
Date Wed, 15 Feb 2017 16:17:43 GMT
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 confidential information
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