Comments on: Quickly Setting Up And Using NHibernate’s Second Level Cache

By: abc

abc — Thu, 26 May 2011 10:49:00 +0000

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By: wes

wes — Wed, 19 Jan 2011 10:13:47 +0000

@ Reggie: whenever you delete/modify something in database, it is also upgraded in cache as well as 2L cache is synchronized with database. A lot of 2l cache provider like NCache has support of SQL dependencies. Whenever there is a modification in database it sends a notification. For further study, please visit this link.

http://www.alachisoft.com/ncache/nhibernate_l2cache_index.html

By: Davy Brion

Davy Brion — Mon, 28 Dec 2009 08:33:31 +0000

@Reggie

the SysCache2 provider is supposed to support SQL Dependencies but i’ve never tried it.

generally speaking though, deleting/updating date directly in a production database is a _bad_ idea and will of course negatively impact pretty much any kind of caching

By: Reggie

Reggie — Mon, 28 Dec 2009 06:53:04 +0000

Hello Davy,

i’m am new to nhibernate and currently learning about the 2nd level cache..

i have a question.

what if the data is deleted or modified directly to the database table(not the cache)?

using sql update or delete statements of course.

can it still synchronize the data correctly?

Thanks,
Reggie

By: Kevin Clark

Kevin Clark — Tue, 05 May 2009 12:57:25 +0000

Nice post. i would like to mention here that NCache is out with its new version with much better support for NHibernate Cache. It can boost NHibernate performance and scalibility.

By: Davy Brion

Davy Brion — Sat, 21 Feb 2009 12:37:04 +0000

not sure about the role thing either, haven’t used it yet

are you sure the lifetime of your session isn’t too long? If you have to load a list of objects, possibly modifying them, then having to discard your changes and having to reload them all within the same session, then you might be doing too much here.

An ISession is like a Unit Of Work… you should try to keep those pretty short.

By: Hitesh

Hitesh — Sat, 21 Feb 2009 11:55:50 +0000

Hi.
Thanks for the imediate response.
1. Yes, I am using the same session object the second time. I cannot use session.clear since the session object is being used for populating other objects too.

2. .Evict requires a single object as a parameter. However, there may be a situation where i make changes to more than one object (ex. i modify 3 objects in the list.) In such a case, I will need to loop through the list and evict each object one by one. Is there a way to avoid the loop.

3. I see that there is sessionFactory.EvictCollection method. This evicts all the lists created using that session Factory. However, there is overloaded sessionFactory.EvictCollection(rolename as string). But I am not able to figure out when and how to create a ‘role’.

Thanks again.

Hitesh.

By: Davy Brion

Davy Brion — Sat, 21 Feb 2009 10:40:31 +0000

when you call the List method through Criteria again, are you still using the same session as you were using when you retrieved the objects the first time? If so, those modified entities are in your _first_ level cache (which is stored at the session level) and those are probably the results you’re getting back

If you are using the same session, try to .Clear the session before reloading the objects or .Evict the one you modified

By: Hitesh

Hitesh — Sat, 21 Feb 2009 10:20:24 +0000

Hi,
The above post explains caching really well. But there is something that I am missing.
Following is the scenario which is failing. Can u guide me to the correct approach.

1. I populate the list using ICriteria. For example, I populate the list with student objects.
2. I have 4 students in the collection.
3. I edit the first object and change the ‘name’ property from Paul to Patrick.
4. I donot save or rollback.
4. I then need to undo the change, so I wish to re-populate the list from the database. Hence I call the List method of the ICriteria object once again.
5. This time I once again get 4 student objects, but the edited object’s ‘name’ property still shows me Patrick and not Paul.

How do I refresh the collection from the database?

I have added all the tags as sepcified in your post to enable the second level cache

Thanks in dvance.
-Hitesh.

By: Davy Brion

Davy Brion — Fri, 20 Feb 2009 15:04:30 +0000

it definitely works, although i’m not sure if it’a actually a good idea to do so… i don’t really think there’s a problem with it, but you might want to investigate possible downsides to using the ASP.NET cache outside of the ASP.NET environment.

By: Miha Necak

Miha Necak — Fri, 20 Feb 2009 14:52:21 +0000

Since one can use ASP.NET Cache outside web development, do you think SysCache will work in a WinForms app for example as well? I haven’t tried it yet, but it seems that it should. What do you thik would be the downfalls of such ussage?