NHibernate query cache not working when using join - nhibernate

Question

When this gets called two times, the second invocation doesn't re-run the query on the database, the query caching works.
var query = from p in session.Query<Product>()
where p.YearIntroduced >= 0
select p;
query = query.Cacheable();
var t = query.ToList();
However, when I put some join on the query, the query cache is not working anymore, hence when this is invoked two times, the query is invoked on database two times too:
var query = from p in session.Query<Product>()
join l in session.Query<ProductLanguage>()
on p.ProductId equals l.ProductId
where p.YearIntroduced >= 0
select new { p, l };
query = query.Cacheable();
var t = query.ToList();
Might be a dumb question, is query caching can work on one table only, hence when adding a join, the query is not cacheable anymore?
What's the solution to make a query cacheable even it has a join?
Another oddity, the query caching with join will work if I remove the where clause. When this gets called two times, the second invocation doesn't re-run the query on database, the query caching works
var query = from p in session.Query<Product>()
join l in session.Query<ProductLanguage>()
on p.ProductId equals l.ProductId
select new { p, l };
query = query.Cacheable();
var t = query.ToList();
But what's the use of a query when you can't put a where clause on it?
Is this an NHibernate bug, or am I just using query caching the wrong way?

Answer 1

Found the solution, put the Where clause on the final part of the query:
var query = from p in session.Query<Product>()
join l in session.Query<ProductLanguage>()
on p.ProductId equals l.ProductId
select new { p, l };
query = query.Where(x => x.p.ProductId && x.l.LanguageCode == "en").Cacheable();
var t = query.ToList();