Incorrect information. The nH session does know the loaded state.... NHibernate.Engine.EntityEntry.LoadedState NHibernate.Engine.CollectionEntry.Snapshot
On May 4, 8:01 pm, John Davidson <[email protected]> wrote: > It is not possible to revert to a copy as retained by the cache because the > cache does not have a separate copy. NHibernate only tracks whether an > object has been changed and if it has then it must be persisted or evicted. > The only way to get the original object back in cache is to reread the > database. > > You may wish it were otherwise, expect it were otherwise, but it is not so. > > John Davidson > > On Tue, May 4, 2010 at 2:49 PM, tz > <[email protected]>wrote: > > > > > "Revert changes with the state of my first load" is what the user > > thinks when she has changed an entity, but regrets. Thus wants to > > cancel. However, she doesn't want to be punished by another database > > hit. I'm sure many other people decide in this case to start a new > > session or evict the object graph and get it again. All to me sound > > like a half-baked solution for reasons I've mentioned before. Another > > half-baked solution is to say that you only change the entities once > > you're 100% sure (no, I want to "commit" once I'm 100% sure). > > > Having said all this, what I want to reach here, completely fits in > > how I want my application to work. I think it is compatible with UoW > > and all those other fancy design patterns. This is clearly a missing > > feature to me. Therefore, I was really hoping for a technical > > satisfying answer, rather than advocating that I'm doing is something > > which is not written in one of the tutorials. > > > So, please... does anyone know how I could do this trick of reverting > > changes in a graph? > > > On May 4, 7:32 pm, Fabio Maulo <[email protected]> wrote: > > > There is something saying me that your problem is in another place. > > > "Revert changes with the state of my first load"..... mmmmm > > > > On Tue, May 4, 2010 at 3:05 PM, tz <[email protected] > > >wrote: > > > > > Thanks for confirming that. I silently started guessing that the > > > > Refresh method shouldn't be what I should use. I started writing my > > > > own "RevertChanges" on a graph, but I'm stuck on how to evict > > > > collections (plus the attached pending deletes/adds). See my code > > > > below: > > > > > public static class ISessionExtensions > > > > { > > > > public static void RevertChanges(this ISession session, object > > > > obj) > > > > { > > > > var source = session as IEventSource; > > > > var action = new RevertChangesCascadingAction(); > > > > > action.RevertChanges(source, obj); > > > > } > > > > > private class RevertChangesCascadingAction : CascadingAction > > > > { > > > > public override void Cascade(IEventSource session, object > > > > child, string entityName, object anything, bool > > > > isCascadeDeleteEnabled) > > > > { > > > > DoRevert(session, child); > > > > } > > > > public override IEnumerable > > > > GetCascadableChildrenIterator(IEventSource session, CollectionType > > > > collectionType, object collection) > > > > { > > > > var coll = collection as > > > > NHibernate.Collection.IPersistentCollection; > > > > var collectionEntry = > > > > session.PersistenceContext.GetCollectionEntry(coll); > > > > > // TODO: HELP!!! > > > > //session.Evict(collection); > > > > //collectionEntry.LoadedPersister.Recreate(coll, > > > > collectionEntry.LoadedKey, session); > > > > > // evicts don't cascade to uninitialized collections > > > > return GetLoadedElementsIterator(session, > > > > collectionType, collection); > > > > } > > > > public override bool DeleteOrphans > > > > { > > > > get { return false; } > > > > } > > > > public override bool PerformOnLazyProperty > > > > { > > > > get { return false; } > > > > } > > > > > protected void DoRevert(IEventSource session, object obj) > > > > { > > > > EntityEntry entityEntry = GetEntityEntry(session, > > > > obj); > > > > > IEntityPersister persister = entityEntry.Persister; > > > > EntityMode mode = persister.GuessEntityMode(obj) ?? > > > > EntityMode.Poco; > > > > persister.SetPropertyValues(obj, > > > > entityEntry.LoadedState, mode); > > > > } > > > > > protected EntityEntry GetEntityEntry(IEventSource session, > > > > object obj) > > > > { > > > > IPersistenceContext context = > > > > session.PersistenceContext; > > > > > if (obj is ValueType) > > > > return null; > > > > > if (context.IsEntryFor(obj) == false) > > > > return null; > > > > > EntityEntry entityEntry = context.GetEntry(obj); > > > > return entityEntry; > > > > } > > > > > public void RevertChanges(IEventSource session, object > > > > obj) > > > > { > > > > EntityEntry entityEntry = GetEntityEntry(session, > > > > obj); > > > > > DoRevert(session, obj); > > > > > session.PersistenceContext.IncrementCascadeLevel(); > > > > try > > > > { > > > > new Cascade(this, CascadePoint.AfterUpdate, > > > > session).CascadeOn(entityEntry.Persister, obj); > > > > } > > > > finally > > > > { > > > > > session.PersistenceContext.DecrementCascadeLevel(); > > > > } > > > > } > > > > } > > > > } > > > > > On Apr 30, 7:55 pm, Jason Dentler <[email protected]> wrote: > > > > > Confirmed it with Fabio: "Refresh is an explicit hit to DB" > > > > > > On Fri, Apr 30, 2010 at 8:35 AM, tz < > > > > [email protected]>wrote: > > > > > > > * Transaction over a read didn't help (see reply on Jason Dentler) > > > > > > * Second level cache is for sharing data across transactions > > > > > > > On Apr 30, 12:24 pm, John Davidson <[email protected]> wrote: > > > > > > > It does not matter what the UoW pattern says about data read. You > > > > > > _REALLY_ > > > > > > > need to put a read action in a NHibernate transaction if you want > > to > > > > > > improve > > > > > > > performance. Not having your reads in a transaction may be why > > you > > > > need a > > > > > > > second level cache (to compensate for not following the specified > > > > rules). > > > > > > > Most of the transactional databases now wrap a read action in an > > ACID > > > > > > > transaction on their own, if the request is not already in a > > > > transaction > > > > > > - > > > > > > > this activity by the database takes more time and resource than > > if it > > > > is > > > > > > > done in the application with NHibernate and UoW. > > > > > > > > John Davidson > > > > > > > > On Fri, Apr 30, 2010 at 7:14 AM, tz < > > > > > > [email protected]>wrote: > > > > > > > > > Thanks for the reply. See my comments inline > > > > > > > > > On Apr 29, 8:26 pm, Jason Meckley <[email protected]> > > wrote: > > > > > > > > > I would approach the problem in a completely different > > manner. > > > > > > > > > 1. no long running sessions > > > > > > > > > 2. only use 2nd level cache in edge cases as a last resort > > > > > > > > > 3. for multi-step operations/commands I would use an > > intermediate > > > > DTO > > > > > > > > > to store updates. When the user clicks "save" is when i would > > > > alter > > > > > > > > > the domain objects. this makes undoing changes much easier. > > > > simply > > > > > > > > > abandon the DTO. > > > > > > > > > I'm not sure whether you do understand my question, but I can't > > > > relate > > > > > > > > any of your reply to my question. I also don't agree with what > > > > you're > > > > > > > > saying... > > > > > > > > * I don't know what "no long running sessions" would solve for > > my > > > > > > > > issue. All these things you're proposing are a "very complex" > > way > > > > to > > > > > > > > do Evict/Load on the same session. > > > > > > > > * 2nd level cache is for performance reasons. The issue I'm > > posting > > > > > > > > about is also for performance reasons. So, this cache stays > > > > > > > > * Why would I do any object dirty management myself, if > > nHibernate > > > > can > > > > > > > > do it for me. > > > > > > > > > > if you do continue down this path are all your session calls > > > > > > happening > > > > > > > > > within a transaction? Proper use of NH dictates that all > > > > operations, > > > > > > > > > both read and write, should happen within at transaction. > > This is > > > > > > > > > critical for client POIDs, proper UOW management and 2nd > > level > > > > cache. > > > > > > > > > Again, no answer on my question. Even more, I don't agree with > > > > you... > > > > > > > > * UoW pattern doesn't say that a read should be in a ACID > > > > transaction. > > > > > > > > UoW itself is a "business transaction" implementation, which is > > > > based > > > > > > > > optimistic concurrency ideologies (meaning that you shouldn't > > keep > > > > an > > > > > > > > ACID transaction open between the reads and the writes). > > > > > > > > > What I want is simply a Update() which does what Evict/Load > > does, > > > > but > > > > > > > > not with giving me a new instance. That's all I'd want to know. > > I > > > > know > > > > > > > > nH keeps the original state in the session (and the second > > level > > > > > > > > cache), so it shouldn't be that difficult I assume. > > > > > > > > > > On Apr 29, 2:05 pm, tz <[email protected] > > > > > wrote: > > > > > > > > > > > Hi guys, > > > > > > > > > > > I'm working with a long running session which contains all > > my > > > > > > required > > > > > > > > > > data. Further, I use level 2 cache intensively, to cache > > that > > > > > > > > > > information. I let my > > ... > > read more »- Hide quoted text - > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups "nhusers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nhusers?hl=en.
