@Entity
public class Parent implements Serializable {
	private static final long serialVersionUID = 1L;

	@Id
	private Integer id;
	private Integer code;
	private Integer item;
}

@Entity
public class Child implements Serializable{
	
	private static final long serialVersionUID = 1L;

	@Id
	private Integer id;
	
	@ManyToOne(fetch=FetchType.LAZY)
	@JoinColumns({
		@JoinColumn(name="prop_code", referencedColumnName="code"),
		@JoinColumn(name="prop_item", referencedColumnName="item")
	})
	private Parent property;
}

When i load two different childs in the same session, and both reference the same parent, 4 queries are fired, 2 for the childs and 2 for the (same) parent.

In that case there should be only 3 queries, two for the childs, and one for the parent, as i believe the parent should be added to the persistenceContext entitiesByUniqueKey map after it is retrieved from the database for the first time.

If my assumptions are correct, a NAIVE fix would be to call persister.addEntity(euk, result) somewhere inside EntityType.loadByUniqueKey.

I've tried this already in a fork, and although it fixed the issue, when running the full suite of tests with H2, a (seemingly) unrelated test (org.hibernate.jpa.test.lock.LockTest.testContendedPessimisticLock) broke on cleanup, so since im extremelly new to Hibernate i have no idea of the side effects of my "fix".