performance question

hi there,

assuming we need multiple lists of objects from the db.

which of the following solutions do perform better?

1)
1 db call using the ojb collection descriptor with retrieve = true
(multiple joins)
i heard about performance issues with too many joins ...

2)
multiple db calls in 1 transaction retrieving each of the lists
separately with broker.getCollectionByQuery calls

with best regards,
Björn