Hi , I guess, If you mergeA with one less B , then the association between A and B will be lost but the instance of B will not be deleted.
If you call em.remove(B) then the instance of B (corresponding row in B) will be deleted. Delete by query also should remove the instance of B. If memory is a constraint and I do not want to pull all the instances of B into memory then I will go with delete by query. I personally think ( I could be wrong), delete by query is better in terms of memory and performance. Regards, Ravi. -----Original Message----- From: Jean-Baptiste BRIAUD -- Novlog [mailto:j-b.bri...@novlog.com] Sent: Thursday, August 13, 2009 3:24 AM To: users@openjpa.apache.org Subject: Re: Delete or merge, update or merge ? up : any advice on that point ? On Aug 8, 2009, at 08:57 , Jean-Baptiste BRIAUD -- Novlog wrote: > Hi, > > say I have one instance to delete, an instance of B knowing that A > contains one to many B. > > Should I merge A with one less B, that should delete the required B > or should I explicitly delete that B with a delete by query or > should I use the remove(thatB) API ? > What are the differences in term of design, memory, performance, ... ? > > Quedtion also apply in case of a new B : merge on A, insert by query > or persist(thatB) on entityManager ? > > The same question apply to merge or update by query one B. > > Thanks ! >
