Using Relationships with Multiple Entity Managers

Question

I am wondering if it is possible to create a relationship between two entities that reside in separate databases.

For example if we took the solution found here http://symfony.com/doc/current/cookbook/doctrine/multiple_entity_managers.html and created a one to many relationship with Users in the customer database to Posts in the default database.

Is this something that is supported by Symfony2 and Doctrine?

Answer 1

Using different object managers (entity managers) doesn't allow the object graphs to intersect. That case is too complex and isn't managed by Doctrine ORM.

If you need such a case, keep the object graphs disconnected by saving the identifiers of the related objects (old style) instead of a reference to them, then manually get the objects through services. You can find a fairly good example of how this would work in an example of connection between Doctrine2 ORM and Doctrine2 MongoDB ODM. Alternatively, you could also use a @PostLoad event listener that populates data in your entities by creating the link through the repositories I've linked in the example. Same for @PostPersist (which should instead extract the identifiers for the related objects), but beware that this technique can become really messy.

Also, if your RDBMS supports cross-database operations on a single host, you can just use a single EntityManager and reference the other table with @ORM\Table(name="schemaname.tablename").