In my application I'm using JDO. In some cases, I have un-owned
relationships where I explicitly created my own entity group because I
need to be able to do transactions with a group of records. For
instance;
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
public class Customer
{
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Long customerId = null;
...
}
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
public class User
{
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key userId = null;
@Persistent(defaultFetchGroup="true")
private Long customerId = null; // foreign-key for Customer
...
}
When I persist a User, I set the parent part of the userId key, then
let JDO fill in the id portion when I call save(). This all works
well. However, sometimes I want to query a set of User's by the
Customer's id. As you can see above, I've duplicated the customerId
in the User record for this purpose. This works fine, but it takes an
extra field and creates an extra index. What I'd really like to do is
to query the User key's parent part so I can save an index, which
could add up over time. I already have records in a production
database that have the above structure, so anything I do needs to be
backward compatible. Everything I see in the docs assumes that you
are using JDO to maintain owned relationships, but I'm not doing
that. I've tried using the 'parent-pk' field Datanucleus extension in
a query where I create a full Customer Key from the customerId field,
but I get an exception. I believe this is because this 'virtual'
field is created by JDO only for owned relationships (but that is just
a guess). Is there an explicit way within JDO to do an ancestor query
using the parent key if you are using unowned relationships?
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