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From Andy Schlaikjer <ha...@cmu.edu>
Subject Re: Dynamic Persistence Unit in SE
Date Tue, 26 Feb 2008 18:16:52 GMT
It's actually a bit easier for me to describe the database schema than 
the api, so I'll start with that;

I'd like a primary entity table to store all "fixed" fields for the 
entity, along with primary key. Any "dynamic" entity fields would 
generate separate tables which might look like:

Table name: <name of entity>_<name of field>
Column 1: foreign key to entity table
Column 2: field value
Column 2 type: defined in terms of field type
(indices defined as needed)

Of course, if the dynamic field type were something more complex than a 
basic type, then this organization would have to be extended somehow..

Andy

Patrick Linskey wrote:
> Can you describe what you're looking for in more detail, both in terms
> of the database schema and the Java APIs?
> 
> -Patrick
> 
> On Tue, Feb 26, 2008 at 9:44 AM, Andy Schlaikjer <hazen@cs.cmu.edu> wrote:
>> On a somewhat related note, I'm interested in using column stores for
>>  entities with arbitrary, typed attributes, but not sure how I might
>>  structure this in JPA. Any thoughts?
>>
>>  Andy
>>
>>
>>
>>  Patrick Linskey wrote:
>>  > Hi,
>>  >
>>  > In Java SE, this is trivial: simply do not list persistent types,
>>  > jars, or mapping files in your persistence.xml file. Dynamic class
>>  > loading is discussed in the docs [1].
>>  >
>>  > It would be nice to add an API to register new classes even when other
>>  > types are listed in persistence.xml; the underlying capability exists,
>>  > but the product does not have such an explicit API.
>>  >
>>  > -Patrick
>>  >
>>  > [1] http://openjpa.apache.org/docs/latest/manual/ref_guide_pc.html#ref_guide_pc_pcclasses
>>  >
>>  > On Sun, Feb 24, 2008 at 2:10 AM, cws <info@jyvy.net> wrote:
>>  >>  brief: I want to add an unknown entity to my running PU in JavaSE.
>>  >>
>>  >>  My JavaSE client app needs to load new, unknown entities (classes, not
>>  >>  objects) from a trusted URLClassLoader.  I would like to add these new
>>  >>  entities to the existing PU, but this doesn't seem possible in SE
>>  >>  without changing the persistence.xml and restarting.  As a kludge I can
>>  >>  send a persistence.xml with the class and create a new PU, but that
>>  >>  doesn't allow interaction with unknown entities in the existing PU.
>>  >>
>>  >>  I believe the spec requires all classes to be known at start, but I'm
>>  >>  hoping OpenJPA or something else has implemented this dynamic
>>  >>  feature(?).  Are there any established workarounds for the client here?
>>
>>
> 
> 
> 

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