Hello. I am using hibernate-core-3.3.2GA with hibernate-jbosscache2-3.3.2GA and I have a question about the query cache.
When I run a query using a Criteria and after calling setCacheable(true), it works fine in the general case.
However, when I search for something that ends up with an empty result set, that query doesn't seem to be cached.
When I monitor the hibernate SQL log (or even monitoring the MySQL TCP connection) I see multiple identical queries performed and when I inspect the cache with jconsole, I don't see any lines corresponding to those queries with empty result sets.

Has anyone experienced this? Is it on purpose?
Thanks.

Question: do you perform a NaturalKeyLookup query ?
In this case empty-result-sets are not stored into cache (and I can also explain you why)

StandardQueryCache#put()
...
if ( isNaturalKeyLookup && result.size() == 0 ) {
return false;
}
...

Thanks for the response.
I don't believe that a NaturalKeyLookup is being performed. The entity with which I was experiencing the issue doesn't have a natural key in its hibernate mapping. Is there any way that natural key lookups can happen automatically?
I re-tested the issue today and queries with empty result sets are being cached now (it only puts a timestamp in the value part).
It's really strange because this was something that was easily noticeable before and now it works fine without any known changes.

>>Is there any way that natural key lookups can happen automatically?

Hardly.
Namely I found todaya bug in the handling of natural key lookups
http://opensource.atlassian.com/projects/hibernate/browse/HHH-4838
but there are 3 conditions which must be fullfilled to generate a natural key lookup:
1. use Restrictions.naturalId()
2. attributes in the where condition must be annotated as NaturalId
3. the NaturalId annotation must have the immutable property set to true.

>>... (it only puts a timestamp in the value part).
Yes, the timestamp is always saved as element nr. 0 in the result-set-array.

>>It's really strange because this was something that was easily noticeable before and now it works fine without any known changes.