[hibernate-issues] [Hibernate-JIRA] Commented: (HSHARDS-1) Support for replicated data

[Max Ross (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSHARDS-1?page=comments#action_26524 ] 

Max Ross commented on HSHARDS-1:
--------------------------------

Interesting idea.  Would this be different than plugging in a distributed cache that just happens to be distributed across multiple SFs running in the same jvm?
As long as your replicated data has the same primary key on each shard it seems like this would work great.  We'd probably want some way to configure which cached objects are available across shards and which ones are available only the shard from which they were originally loaded since we don't want everything that's in the second level cache to be shared across shards.  I assume the class level would be the right place to control this.  Or maybe it's time to introduce a third-level cache.  :-)

> Support for replicated data
> ---------------------------
>
>          Key: HSHARDS-1
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HSHARDS-1
>      Project: Hibernate Shards
>         Type: New Feature

>   Components: engine
>     Versions: 3.0.0.Beta1
>  Environment: all environments
>     Reporter: Max Ross
>     Assignee: Max Ross

>
>
> It's currently difficult to deal with replicated, slow-changing data.  For example, you might have a Country table on all your shards with the same data and the guarantee that this data will never change.  You'd want to create associations to Country objects in your domain model too.  So now suppose you want to create a new persistent object with an association to a Country.  First off, your query to lookup that country by id is going to return 1 Country per shard.  That in and of itself is a problem, but supposing we could do something to make it return just one shard.  How do we guarantee that we get the Country that lives on the shard that the object is going to be saved on?  We haven't even gone through shard selection yet!  So anyway, yeah, we need to address this.  Enhancing the cross-shard relationship detection interceptor to "swap" out the wrong Country instance for the right Country instance seems like an interesting idea.

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