Hello

First of all thank you all for the work done.
I am currently testing a newly developed application based on stateless
EJB sessions executing many HQL queries. One of the bottlenecks in
the application is the memory consumed by HQL query instanciations.
Given a HQL string, why hibernate must re-parse and regenerate
a QueryImpl each time a session.createQuery is achieved ? Given that
all sessions are obtained from the same SessionFactory, this should result
in equivalent QueryImpl objects ? So could it be possible to extend the
caching strategy of Hibernate so that a query is fully compiled only the
first time a new HQL is encountered, for a given SessionFactory ?
Afterwards, an instance of such a Query could be internally cached and clone()d (or something like this) each time createQuery is called with the same HQL ?

Am I totally wrong ?

Thank you in advance for any advice, and good luck for hibernate 2.2... ;-)

sincerely yours

Emmanuel Ligne

You are mistaken. Hibernate caches compiled HQL queries.

Is this Query cache by Session or by SessionFactory ?
To be more accurate : given 2 sessions from the same sessionfactory,
if I call createQuery(myHQL) on one session, this will create a new
QueryImpl. If I recall it on the same session, the query cache should
return me the same QueryImpl instance. Nice.
Now if I call createQuery(myHQL) (the same HQL) on the other session,
does hibernate gives me the previously instanciated query or does it
compile a new one ? Personally I vote for the second choice, while
I would have liked the first one (as both sessions are from the same
sessionfactory). Optionally for thread safety, return a clone of the already
instanciated query.

Am I wrong ?

And thank you for your quick answer Gavin (as usual...).

Sincerely yours

Emmanuel Ligne

Hello again

I just looked at the SessionImpl code (in hibernate 2.1.1) and it seems
like query caching is only enabled when executing HQL via
session.find or session.iterate.
When calling createQuery on a session, a new QueryImpl instance
is created, resulting in a new HQL parsing and so. Features of Query
such as max-result count and parameterList (ie usage of IN in hql)
are a must-have for my app, and they don't seem to be available in
the simpler, direct call to session.iterate/find.

look again, you have misunderstood the code - all compiled HQL queries are cached in the SessionFactory