This document discusses nHibernate caching. It explains that nHibernate uses two levels of caching - a first level cache associated with sessions for each transaction, and a second level cache associated with the session factory that caches objects across transactions. It provides details on configuring different cache providers like Prevalence and SysCache, and setting caching strategies for entities. Logs show objects being retrieved from the cache instead of the database, improving performance.

1. nHibernate Caching Albert Kuo 1

2. Database Transaction nHibernate Caching nHibernate Caching Implementation Reference 2 Agenda

3. Database Transaction 3

4. Understanding database transactions 4

5. NHibernateITransaction API 5

6. NHibernateITransaction API 6

7. nHibernate Caching 7

8. Used for optimizing database applications. A cache is designed to reduce traffic between your application and the database by conserving data already loaded from the database. Database access is necessary only when retrieving data that is not currently available in the cache. The application may need to empty (invalidate) the cache from time to time if the database is updated or modified in some way, because it has no way of knowing whether the cache is up to date What is caching? 8

9. nHibernate Cache Persistence context cache Pluggable, scope is process or cluster 9

10. Two different Caches First-level cache Second-level cache associated with the Session object Hibernate uses first-level cache on a per transaction basis (within a single transaction boundary) Used mainly to reduce the number of SQL queries it needs to generate within a given transaction. For example, if an object is modified several times within the same transaction, Hibernate will generate only one SQL UPDATE statement at the end of the transaction, containing all the modifications associated with the SessionFactory object Second-level cache keeps loaded objects at the Session Factory level across transaction boundaries The objects in the second-level cache are available to the whole application, not just to the user running the query This way, each time a query returns an object that is already loaded in the cache, one or more database transactions potentially are avoided. 10

11. Use it when you need to cache actual query results, rather than just persistent objects Query-level Cache 11

12. nHibernate Caching Implementation 12

13. http://nhforge.org/media/p/6.aspx Where to download 13

14. 14 Cache Providers You can choose one of provider to use

15. How to configure? Prevalence SysCache 15

16. How to configure? Prevalence SysCache 16 Add four properties into <session-factory> <!-- nHibernate Cache configuration --> <property name="cache.provider_class">NHibernate.Caches.Prevalence.PrevalenceCacheProvider, NHibernate.Caches.Prevalence</property> <property name="cache.use_query_cache">true</property> <property name="cache.use_second_level_cache">true</property> <property name="cache.default_expiration">120</property> Add four properties into <session-factory> <!-- nHibernate Cache configuration --> <property name="cache.provider_class">NHibernate.Caches.SysCache.SysCacheProvider,NHibernate.Caches.SysCache</property> <property name="cache.use_query_cache">true</property> <property name="cache.use_second_level_cache">true</property> <property name="cache.default_expiration">120</property>

17. How to configure ? – cont. 17

18. 18 How to configure ? – cont.

19. How to configure ? – cont. Configure caching strategy for each mapping file 19

20. read only If your application needs to read but never modify instances of a persistent class, a read-only cache may be used. This is the simplest and best performing strategy. read/write If the application needs to update data, a read-write cache might be appropriate. This cache strategy should never be used if serializable transaction isolation level is required. nonstrict read/write If the application only occasionally needs to update data and strict transaction isolation is not required, a nonstrict-read-write cache might be appropriate. Cache StrategieCache Strategies (for Second-Level) 20

21. 21 Run Search Function

22. 2009-10-01 16:36:49,250 INFO NHibernate.Cfg.SettingsFactory.CreateCacheProvider(:0) - cache provider: NHibernate.Caches.Prevalence.PrevalenceCacheProvider, NHibernate.Caches.Prevalence 2009-10-01 16:36:49,250 INFO NHibernate.Cfg.SettingsFactory.BuildSettings(:0) - query cache factory: NHibernate.Cache.StandardQueryCacheFactory 2009-10-01 16:36:49,578 DEBUG NHibernate.Cache.CacheFactory.CreateCache(:0) - cache for: HelloNHibernate.vo.Contact usage strategy: read-write 2009-10-01 16:36:49,750 DEBUG NHibernate.Cache.CacheFactory.CreateCache(:0) - cache for: HelloNHibernate.vo.People usage strategy: read-write 2009-10-01 16:36:50,125 DEBUG NHibernate.Loader.Loader.InitializeEntitiesAndCollections(:0) - total objects hydrated: 3 2009-10-01 16:36:50,125 DEBUG NHibernate.Engine.TwoPhaseLoad.InitializeEntity(:0) - resolving associations for [HelloNHibernate.vo.People#3] 2009-10-01 16:36:50,140 DEBUG NHibernate.Engine.Loading.LoadContexts.LocateLoadingCollection(:0) - creating collection wrapper:[HelloNHibernate.vo.People.Contacts#3] 2009-10-01 16:36:50,140 DEBUG NHibernate.Engine.TwoPhaseLoad.InitializeEntity(:0) - adding entity to second-level cache: [HelloNHibernate.vo.People#3] 2009-10-01 16:36:50,140 DEBUG NHibernate.Cache.ReadWriteCache.Put(:0) - Caching: HelloNHibernate.vo.People#3 2009-10-01 16:36:50,140 DEBUG NHibernate.Caches.Prevalence.PrevalenceCache.Get(:0) - Fetching object 'NHibernate-Cache:HelloNHibernate.vo.People:HelloNHibernate.vo.People#3@3' from the cache. 2009-10-01 16:36:50,156 DEBUG NHibernate.Cache.ReadWriteCache.Put(:0) - Item was already cached: HelloNHibernate.vo.People#3 22 Check log – Prevalence Set cache provider Cache strategy Fetch data from cache

23. 2009-10-19 13:21:27,046 DEBUG NHibernate.Cache.ReadWriteCache.Get(:0) - Cache lookup: Persistence.vo.CaseState#0 2009-10-19 13:21:27,046 DEBUG NHibernate.Caches.SysCache.SysCache.Get(:0) - Fetching object 'NHibernate-Cache:Persistence.vo.CaseState:Persistence.vo.CaseState#0@0' from the cache. 2009-10-19 13:21:27,046 DEBUG NHibernate.Cache.ReadWriteCache.Get(:0) - Cache hit: Persistence.vo.CaseState#0 2009-10-19 13:21:27,046 DEBUG NHibernate.Event.Default.DefaultLoadEventListener.AssembleCacheEntry(:0) - assembling entity from second-level cache: [Persistence.vo.CaseState#0] 2009-10-19 13:21:27,046 DEBUG NHibernate.Event.Default.DefaultLoadEventListener.AssembleCacheEntry(:0) - Cached Version: 2009-10-19 13:21:27,046 DEBUG NHibernate.Event.Default.DefaultLoadEventListener.DoLoad(:0) - resolved object in second-level cache: [Persistence.vo.CaseState#0] 2009-10-19 13:21:27,046 DEBUG NHibernate.Engine.TwoPhaseLoad.InitializeEntity(:0) - adding entity to second-level cache: [Persistence.vo.Cases#200910090114] 2009-10-19 13:21:27,046 DEBUG NHibernate.Cache.ReadWriteCache.Put(:0) - Caching: Persistence.vo.Cases#200910090114 2009-10-19 13:21:27,046 DEBUG NHibernate.Caches.SysCache.SysCache.Get(:0) - Fetching object 'NHibernate-Cache:Persistence.vo.Cases:Persistence.vo.Cases#200910090114@-909291618' from the cache. 2009-10-19 13:21:27,046 DEBUG NHibernate.Cache.ReadWriteCache.Put(:0) - Item was already cached: Persistence.vo.Cases#200910090114 23 Check log – SysCache

24. nHibernate in Action, Manning, 2009/2 http://www.manning.com/kuate/ nHibernate online doc: Chapter 14. Improving performance https://www.hibernate.org/hib_docs/nhibernate/html/performance.html nHibernate online doc: Chapter 20. NHibernate.Caches https://www.hibernate.org/hib_docs/nhibernate/html/caches.html NHibernate考察系列 06 进阶篇 http://www.cnblogs.com/riccc/archive/2007/04/17/nhibernate-entity-lifecycle-secondary-cache-interceptor.html NHibernate之旅(22)：探索NHibernate一级缓存 http://www.cnblogs.com/lyj/archive/2008/11/24/1340253.html 24 Reference