According to the JPA spec, the default ordering of a 1:M or M:M relationship is by the primary key.

Does anybody know how hibernate implements this?

Does hibernate do an in memory sort?

The reason why I ask is because, from the logging, the prepared statement that executes the query for reading the relationship has no "ORDER BY" in it?

My design is using compound primary keys and I cannot figure out hibernate is doing the default sort.

Any help appreciated.

by default there is no ordering in Java Persistence
if you use @OrderBy, you'll see the order by clause in SQL