Hi Anne,
thank you very much for the reply. I tried to follow your suggestions,
but my collections are not yet fetched from the SL Cache. So here is
what my structure looks like.
ClassA -> Decorated with [Cache(Usage = CacheUsage.ReadWrite, Region =
"10Minutes")]
|_______> SubclassB -> Decorated with [Cache(Usage =
CacheUsage.ReadWrite, Region = "10Minutes")]
|_____________SubclassC -> Decorated with [Cache
(Usage = CacheUsage.ReadWrite, Region = "10Minutes")]
|_____________SubclassD -> Decorated with [Cache
(Usage = CacheUsage.ReadWrite, Region = "10Minutes")]
So first of all, my classes are all decorated with the Cache Tag. Now
i have in my ClassA a OneToMany reference to SubclassB. This reference
is configured as follows
[Bag(0, Lazy = true, Name = "SubclassB ", Cascade = "all", Fetch =
CollectionFetchMode.Unspecified)]
[Key(1, Column = "CLASSA_ID")]
[OneToMany(2, ClassType = typeof(SubclassB))]
[Cache(3, Region = "5Minutes", Usage = CacheUsage.ReadWrite)]
public virtual PersistentGenericBag<SubclassB> SubclassBList{ get;
set; }
I hope this is correct. Now in SubclassB there are to more references.
To SubclassC and SubclassD. Both are ManyToOne references. I will show
you the configs.
[ManyToOne(0, Name = "SubclassC", ClassType = typeof(SubclassC),
Column = "SUBCLASSC_ID", Cascade = "all", Fetch =
FetchMode.Unspecified)]
[Cache(1, Region = "5Minutes", Usage = CacheUsage.ReadWrite)]
public virtual SubclassC SubclassC{ get; set; }
[ManyToOne(0, Name = "SubclassD", ClassType = typeof(SubclassD),
Column = "SUBCLASSC_ID", Cascade = "all", Fetch =
FetchMode.Unspecified)]
[Cache(1, Region = "5Minutes", Usage = CacheUsage.ReadWrite)]
public virtual SubclassD SubclassD{ get; set; }
Ok now i think every class an every collection is configured for
caching. But i have already hits to the db and i do not understand why
i have these hits. What am i doing wrong? Do you have any more hints
for me?
Here is what i found in the nhibernate debug log. It firsts looks for
a cached collection of classA. An surprisingly i get an:
ReadOnlyCache ThreadID=8: Cache hit
This is what i see in my sql profiler. There is no second dbhit for
class a. Alright.
Now he is looking for a cached collection for SubclassB. The result
is:
DefaultInitializeCollectionEventListener ThreadID=8: collection not
cached
And here is what i see in my sql profiler. I get the dbhit. Why? For
SubclassC and D its the same behaviour.
Anne you, and maybe an other professional, are my last hope to get an
success story out of this. Please let my know if you have any other
hints for me.
Thanks in advance
Regards
eigeneachse
On Nov 14, 5:12 am, Anne Epstein <[email protected]> wrote:
> Hi! Caching is a bit more difficult to get right than it seems initially.
> All entities you want cached should have the cache tag on them, and this
> includes your referenced object mappings. If you mark the entity you're
> referencing as cached, then you should be set for your many-to-one
> relationships, i.e. . If your query was for Dog and Dog has one Owner(type
> Person) you would need to set the type Person to be cached to not get the db
> hit when you traverse the dog-owner relationship. The reason you need to
> cache Person is because cached Dog only has the OwnerId in it, not a whole
> Person. NH will index objects of type Person by that ID so if you have
> Person cached NH will grab it there instead of going to the DB.
>
> Traversing collections off your cached object is similar, but is a bit more
> involved. Let's say your Dog had a collection of Puppies. Sure, you may
> have all Dog objects caching, but when it you have NH cache a Dog, it only
> caches the things that are in that DB row. if you think about how
> collections are implemented in a database, the relationship to Dog isn't in
> that Dog row, it's in the rows of each of the Puppies as a foreign key so
> it's not cached with Dog. Even if each of the puppies is cached, it's that
> relationship FROM Dog TO the puppies that you need, and will get the query
> hit for. Don't want that DB hit? there's an easy fix: put a cache tag
> *inside your collection definitions*, i.e. your lists, sets, bags. That
> will cache the *list of ids* of the puppies that Dog has. Your puppy
> objects themselve are already cached, right? So now it's like the Dog to
> Owner: cached id to object, no db hit.
>
> Hope that helps,
> Anne
>
> On Fri, Nov 13, 2009 at 3:14 PM, eigeneachse
> <[email protected]>wrote:
>
>
>
> > h...@all,
> > i have read various posts, blogs.... about the nhibernate caching
> > methods. For me it is good that my SysCache2 configuration is working.
> > But it is only working in parts and i have a few problems in my
> > understanding if this is an configuration failure on my side or if
> > there is something other wrong.
>
> > So i have the following HQL Query
>
> > return Session.CreateQuery(@"
> > select something.....")
> > .SetParameter(0, aParameter)
> > .SetParameter(1, aSecondParameter)
> > .SetCacheable(true)
> > .SetCacheRegion("10Minutes")
> > .List<aClass>()[0];
>
> > The returning class itself has some references to other tables which
> > are configured via an one-to-many relationship. When i call this query
> > then the first time the sql is fired against the database. So the base
> > objects and the referenced objects are fetched from the database. If i
> > do this a second time, then only the referenced objects are fetched
> > over sql again. But why? I think i have configured that everything
> > should be cached.
> > And here is where my understanding in nhibernate caching ends. Are
> > only the base objects cached? Why arent the referenced objects cached?
> > I read about the query cache and the entity cache. I think that here
> > the query cache is used. How can the referenced objects be cached?
>
> > It would be very good if someone could help my with this. I am really
> > optimistic that this problem is solved already.
> > Please let me know if you need more informations.
>
> > Thanks in advance for your help
>
> > Regards
>
> > eigeneachse
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