How hibernate works with lazy fetching references?

Question

First I will fetch a list of Game objects form database using hibernate

List<Game> games = (List<Game>) session.createQuery("from Game where status=2").list();

Consider that Game Object has a reference to Location object. And Location object has an Id.

long id = games.get(0).getLocation().getId();

Here I need to know the Id of the location where game is mapped to. And Location is defined as a lazy fetch. But in the database each row for game has the location_id field.

So my question is when I request hibernate to fetch the Id through an object as shown, is it first fetching the object and then the Id of that? or is it more intelligent and fetch the Id directly from the game?

Answer 1

It will produce 2 statements.

First the Select for the Game including the Gameid and the locationid

Second the Select for the Whole location-row including the LocationId.

Why? Because after getLocation() the Runtime will not know that you only need the id .