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From Fernando Padilla <f...@alum.mit.edu>
Subject Re: openjpa-slices
Date Fri, 21 Nov 2008 18:33:30 GMT
Yeah.  I was riding in today and I was thinking about the Replication 
feature.  I was thinking the same thing about how the Replication slices 
and the Distribution slices look a lot a like.. and I was wondering 
maybe I didn't see the motivating use-case for the replication feature.

So for me to understand it better.. can you share some use-cases, users 
of the Replication feature.. was it a feature needed/used by someone, or 
was it just a neat feature to add.. just wondering.  I bet it's useful, 
but I guess from my app, I don't see a use for it just yet.


Pinaki Poddar wrote:
> Hi,
>> I have finished walking through the whole slices code, and it looks good.
> 
> "Proof of the pudding is in eating" :)
> 
>> I think we need to have a plugin to figure out the slice targets the
>> queries run against. Currently this is > supported through query "hints",
>> but I think that is a really bad choice, 
> 
> The "bad choice" is made to ensure JPA API stability. So far, one of the
> strong design constraints in Slice is to place minimal demand to an existing
> JPA application and Query hints being a JPA concept, we decided to leverage
> the same for narrowing the target slices for a query. But more on this
> follows...
> 
>> when really the ReplicationPolicy is the one that should decide which
>> classes are replicated and how...
> 
> An alternative design possibility is to reinterpret DistributionPolicy
> itself and deprecate ReplicationPolicy and @Replicated altogether. The
> modified DistributionPolicy method should return an array or list of slice
> names -- with the semantics that return value of more than one slices imply
> that the input entity is to be replicated.
> If we go by that route of modifying DistributionPolicy then it can also
> incorporate the Query targets as per your suggestions.
> 

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