Ok, I was affraid of having a lot more data into the DB.
The stored data type  will be just simple object or some embedded object
could be present too (to know if I have to go all over the field map to
find relationnal data) ?
Guillaume
2012/3/15 Emmanuel Bernard <emmanuel(a)hibernate.org>
 On 15 mars 2012, at 17:04, Guillaume SCHEIBEL wrote:
 > TestableGridDialect.associationCacheSize is killing me !
 > Because it's not possible to perform a query without knowing the field
 name. So I can forget about "I want to know the amount of document which
 contain a field (except '_id') whose type is ObjectID"
 >
 > The same query with "contain a field named 'myField' ..." works.
 >
 > I could probable iterator over all collections and all documents but it
 definitely bursts the tests performances.
 Does it? Surely we don't have much than 10 elements in these collections
 for a given test.