Grails/Gorm - namedQuery hasMany relationship - grails

Question

I have the following domain classes
class EventA {
static belongsTo = [offer: Offer]
}
class EventB extends EventA {}
class EventC extends EventA {}
class Offer {
static hasMany [events: EventA]
}
I need to retrieve offers that are not associated with an EventC.
In SQL this can easily be performed as:
SELECT *
FROM OFFER O
LEFT JOIN EVENTC C ON O.event_id = C.id
WHERE C.ID IS NULL
Searching through the grails documentation I found instanceOf. Stating that once you have the result set you can perform a check of the instance type.
def offers = Offer.list()
for (Offer o in offers) {
for(Event e : o.events) {
if (e.instanceOf(EventC)) {
// no bueno
}
}
}
The above just feels wrong. I would prefer to have the database do such filtering for me. Is there a way to perform such a filter with searchCriteria?

Answer 1

You can accomplish this by querying the Event classes directly. That way you can specifically query the flavor of Event you care about. Then query the Offer table with the list of Id's
Offer.findAllByIdInList(EventC.list().offerId)

Answer 2

This actually ended up being easier then I expected. On my search criteria, I can build an expression to not include any Offer that has an event EventC.
Example:
Offer.with {
events {
ne('class', EventC)
}
}
Since I questioned this approach I enabled hibernate logging. Ironically, it generated SQL that was pretty similar to what I was after.
SELECT *
FROM OFFER O
LEFT JOIN EVENTB B ON O.ID == B.EVENT_ID
LEFT JOIN EVENTC C ON O.ID == C.EVENT_ID
WHERE
(
CASE
WHEN B.ID IS NOT NULL THEN 1
WHEN C.ID IS NOT NULL THEN 2
END <> ?
)