Follow up #3173 - Change BeanSet clear() with orphanRemoval to lazy load ALL properties (avoid 1+N)

[rbygrave]

Scenario:
set.clear() on a Set with orphanRemoval = true

Currently the clear() invokes lazy loads only fetching the Id properties but this is problematic when the entity bean in the Set has a hashcode/equals implementation as it results in 1 + N queries. That is, for orphan removal it is identifying the beans that are going to be deleted and when doing that (with only the Id property fetched) the hashcode/equals implementation is invoked and that then invokes lazy loading N times where N is the number of elements in the collection that is being cleared.

To avoid the 1+N lazy loading queries instead the clear() invokes lazy loading that includes ALL the properties such that equals/hashcode implementation does not itself invoke lazy loading.

To be awesome, ebean would detect the properties that are used in hashcode/equals implementation and only fetch the Id property and those properties involved in the hashcode/equals for this case (rather than all properties). This might be a future optimisation that we could pursue using the entity bean enhancement to detect those properties used in the hashcode/equals.