I want to fetch a lazy association, which is present on a subclass only.
In Hibernate, it is possible to use fetch treat joins, for example
select a from A a left join fetch treat(a.parent as Child) u left join fetch child.some
This is not supported in EclipseLink by default (I believe it is a bug). But there is working workaround in Joiner library (
InheritanceJoiningCustomizer in https://github.com/encircled/Joiner)