Re: [hibernate-dev] What should happen to queued operations when a collection is detached?

Guillaume has reviewed my PR and I've pushed the fix to master. I still think the inconsistency should be resolved. I have no plans to do any more on this without any feedback. Regards, Gail On Tue, Oct 2, 2018 at 6:16 PM Gail Badner <gbadner(a)redhat.com&gt; wrote: > Since I haven't heard anything back, I've gone ahead and updated my PR [1] > to ignore queued operations when merging a detached collection. This restores > the functionality that was in place prior to HHH-5855 (which caused > HHH-11209). > > In addition I've added warnings for the following situations: > * a detached collection is being merged that has queued operations; > * a collection with queued operations is attached to a session; > * a collection with queued operations is detached from a session. > > I've also added a test case that shows that Session#merge and > Session#saveOrUpdate have different results when called on an entity with a > collection with queued operations. When Session#merge is called, the queued > operations are ignored. When Session#saveOrUpdate is called, the queued > operations are executed on flush. > > I don't like this inconsistency, but I'm not sure what to do about it. I > don't think it's a good idea to have collections floating around with > queued operations. As far as the application knows, it is just an > uninitialized collection. I can see that the entity could find its way into > a new session, with surprising results. > > IIUC, an application probably shouldn't detach an entity with a collection > in this state (having queued operations), so I think it makes sense that a > warning be logged when this happens. On the other hand, the warning will > also be logged if a transaction involving updates to a collection with > queued operations fails. > > I would really appreciate some feedback on this, since HHH-11209 is a bad > regression that really should be fixed. > > Thanks, > Gail > > [1] https://github.com/hibernate/hibernate-orm/pull/2460 > > On Fri, Sep 28, 2018 at 6:27 PM Gail Badner <gbadner(a)redhat.com&gt; wrote: > >> HHH-11209 involves a bug merging a detached entity with an uninitialized >> collection that has queued operations. >> >> After looking into this issue I found a bug >> where AbstractPersistentCollection#operationQueue was not being cleared >> after a commit, if there was no cascade mapped for the collection. >> >> I've fixed that in a PR. [1] >> >> After that fix, the detached entity in the test case attached to >> HHH-11209 has an uninitialized entity without any queued operations after >> commit, which can be merged successfully in a new session/transaction. >> >> There is still a problem when Hibernate tries to merge a detached entity >> has an uninitialized collection with queued operations though. My PR throws >> UnsupportedOperationException in this case, and there is a test case that >> reproduces it. >> >> I've been working on a fix to add support for this, but I have my doubts >> that it really should be supported. I see that prior to fixing HHH-5855 >> (which caused HHH-11209), Hibernate simply ignored the queued operations in >> the detached collection. [2]. >> >> The fix for HHH-5855 properly dealt with merging a managed collection >> that was uninitialized with queued operations. It introduced the bug where >> a NullPointerException would get thrown if that collection was detached. >> >> If we want to support merging the queued operations, then I would >> consider that an improvement. Would this be a worthwhile improvement? I'm >> guessing not, but I wanted to get some opinions. >> >> For now, I see a couple of ways to deal with this so that HHH-11209 can >> be wrapped up: >> 1) ignore queued operations in a detached collection when merging, as was >> done before HHH-5855 was fixed. >> 2) clear the queued operations when the collection is detached. >> >> Comments? >> >> Thanks, >> Gail >> >> [1] https://github.com/hibernate/hibernate-orm/pull/2460 >> [2] >> https://github.com/hibernate/hibernate-orm/commit/c1934b72edb4f7815209376... >> > _______________________________________________ hibernate-dev mailing list hibernate-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev