CODEWITHSUNDEEP
javajdodatanucleus
Karl M. Davis
Karl M. Davis

Reputation: 616

How to customize the foreign key names used in DataNucleus JDO inheritance hierarchies?

The JDO Inheritance guide for DataNucleus mentions that in InheritanceStrategy.NEW_TABLE class relationships, a foreign key will be created between the superclass' and subclass' tables. Running the DataNucleus schema generator, I do see that such a foreign key is being generated. What I can't discover, though, is how the names for these foreign keys can be customized.

For example:

@PersistenceCapable(table = "login_identities")
@Inheritance(strategy = InheritanceStrategy.NEW_TABLE)
public abstract class AbstractLoginIdentity { ... }

@PersistenceCapable(table = "email_login_identities")
@Inheritance(strategy = InheritanceStrategy.NEW_TABLE)
public class EmailLoginIdentity extends AbstractLoginIdentity { ... }

Given those classes, DataNucleus will generate a foreign key like the following (for PostgreSQL):

-- Constraints for table "email_login_identities" for class(es) [com.trickle.api.accounts.EmailLoginIdentity]
ALTER TABLE "email_login_identities" ADD CONSTRAINT "email_login_identities_FK1" FOREIGN KEY ("id") REFERENCES "login_identities" ("id") ;

I can't discover any way to alter the "email_login_identities_FK1" constraint's name. Adding a @ForeignKey annotation to the subclass just adds a new foreign key.

Can this be customized?

Upvotes: 1

Views: 208

Answers (1)

Neil Stockton
Neil Stockton

Reputation: 11531

The foot of this page shows how to define a foreign key for the join to superclass, using XML.

I don't see a way of doing that in annotations (since @Inheritance has no @Join, and @Join has no @ForeignKey) ... but then I would never want to hardcode ORM definitions into a Java class. I assume you could request such a facility in annotations via the Apache JDO people.

Upvotes: 1

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