[news.eclipse.technology.ejb-orm] JDO fetch-groups important for RCP, EJ

[Joerg von Frantzius <joerg.von.frantzius@xxxxxxxxxxxxxxxxxxxx>]

Max Rydahl Andersen schrieb:

with a initial report query and then only load the full objects

Sorry, I can't find anything about "report query", neither with respect  to Hibernate nor EJB3, could you tell me what that is?

its also called scalar queries.

"select o.x, o.y, o.z from SomeEntity o"

..but as I said - there is more ways to do this, each case has their
strength/weaknesses.

/max

I can't see how retrieving the ids could be of help here, as that doesn't give you "hollow" objects as in JDO, which you can use as a table input with their field values being lazy-loaded initially for the first k visible rows of the table.

As far as I can see, what is doable with EJB3 will take you O(n) SELECT statements (n being the number of objects), in contrast to O(k) SELECT statements with JDO (k being a small constant). That's one real hell of a difference! That's the number of SELECTs until the table contents are fully loaded into memory, with the first rows being visible before it is fully loaded, and the user at least being able to scroll with perceivable delays before it is fully loaded, and with no perceivable delays once it is loaded.

If that can be done with EJB3 in O(k), then please tell me how exactly that can be done. Until then, I'd say EJB3 is badly missing the concept of fetch-groups. Maybe someone else of the JSR220 experts assembled here has an idea how it can be done in O(k) with EJB3?

My insisting here might seem a bit trollish, but things like that absolutely make a difference for RCP fat clients. The technical competitor here is MS Access, and that has some really damn fast table loading.