[hibernate-dev] Bad performance with collection fetching and @BatchSize (HHH-9592)

Hi all, For the past few weeks, we've been struggling with bad performance caused by HHH-9592. In short, even with @BatchSize(size=100) on all entities, the vast majority of queries (up to 70%) is in the form of 'SELECT a, b, c FROM foo WHERE id=123'. As far as I can see, almost all of these queries are caused by PersistentBag.initializeFromCache. This method assumes an entity can be loaded from cache if the collection that contains it, was loaded from cache. However, as entities and collections do not live in the cache together, this often is not the case. The current implementation triggers a separate query for every record that cannot be loaded from the cache, ignoring the @BatchSize on that entity. As this issue is effecting of our application severely, I'm investigating possible solutions. Pre-fetching entities that are likely to be fetched later on in the request, in a separate query helps a bit, but requires a lot of work. So, I'm looking for a more fundamental solution. In the ideal world, Hibernate would fetch a full batch (100 in our case) at once, not only from the collection being loaded, but also from other collections with unloaded entities. Is this possible? If not, what can we do to improve the situation? Best regards, Emond Papegaaij