Beginner needs help with second-level cache

[Julien Martin]

Hello,
I am trying to get the second-level cache to work. I log the summary of stats and I noticed that I always get ZERO second-level cache puts and hits whereas the query-cache gets puts and hits. Is that normal. Can anyone help me understand what's going on??
Thanks in advance,
Julien Martin.

Here is the relevant snippet from my persitence.xml:

 <properties>
      <property name="hibernate.connection.url" value="jdbc:as400://AS400D.CALYONFINANCIAL.COM"/>
      <property name="hibernate.connection.driver_class" value="com.ibm.as400.access.AS400JDBCDriver"/>
      <property name="hibernate.connection.password" value="martin2"/>
      <property name="hibernate.connection.username" value="jmartin"/>
      <property name="hibernate.cache.provider_class" value="org.hibernate.cache.OSCacheProvider"/>
      <property name="hibernate.cache.use_second_level_cache" value="true"/>
      <property name="hibernate.cache.use_query_cache" value="true"/>
      <property name="hibernate.generate_statistics" value="true"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.DB2400Dialect"/>
</properties>

[Jaikiran Pai]

Have you added

<cache usage=..../>

entry in the hbm.xml file of your hibernate mappings?

[Julien Martin]

Japirai,
I use JPA... Can you advise me on how to proceed please?
Julien.

[Jaikiran Pai]

I havent used JPA extensively. So i wont be able to help you much. I would believe there would be some class level annotation which will allow you to enable caching the entity - Just a guess.

[Julien Martin]

Thanks anyhow for taking the time to reply!! I'll have a look at the jpa annotations.
Best regards,
Julien.

[Jaikiran Pai]

Here it is Hibernate Annotations. Section 2.4.8 "Cache" on that page.

[Julien Martin]

Hello again,

I followed the instructions to the letter as follows:

@Entity
@Table(name = "EMRPRD.EQUIEX")
@org.hibernate.annotations.Cache(usage=CacheConcurrencyStrategy.READ_ONLY)

Here is what I get:
**********************************
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:463 - Logging statistics....
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:464 - start time: 1177342200468
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:465 - sessions opened: 8
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:466 - sessions closed: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:467 - transactions: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:468 - successful transactions: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:469 - optimistic lock failures: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:470 - flushes: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:471 - connections obtained: 16
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:472 - statements prepared: 16
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:473 - statements closed: 16
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:474 - second level cache puts: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:475 - second level cache hits: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:476 - second level cache misses: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:477 - entities loaded: 30
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:478 - entities updated: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:479 - entities inserted: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:480 - entities deleted: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:481 - entities fetched (minimize this): 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:482 - collections loaded: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:483 - collections updated: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:484 - collections removed: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:485 - collections recreated: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:486 - collections fetched (minimize this): 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:487 - queries executed to database: 16
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:488 - query cache puts: 10
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:489 - query cache hits: 0
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:490 - query cache misses: 10
INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:491 - max query time: 765ms
**********************************

The persistence.xml has not changed.

Any clue?

J.

[Mark Spritzler]

It looks to me like some values were being loaded into the second level cache. Why would you need to change your persistence.xml. The second level cache is not part of the JPA spec, so nothing would be defined in the spec defined persistence.xml.

Second Level caching here is a Hibernate specific thing, hence the Hibernate annotation instead.

Mark

[Julien Martin]

Thanks Mark,

It looks to me like some values were being loaded into the second level cache.

Please tell me what makes you say that?

Why would you need to change your persistence.xml. The second level cache is not part of the JPA spec, so nothing would be defined in the spec defined persistence.xml.

I make good note of this. I thought the property would just be ignored if the persistence provider was changed.

Julien.

[Mark Spritzler]

"INFO-org.hibernate.stat.StatisticsImpl-StatisticsImpl.java:488 - query cache puts: 10"

But wait, that is the query cache.

So, which cache provider are you using and did you define your cache region in that providers configuration file?

Not only do you put a cache usage in the mapping, but you also have to tell the provider what cache region to create

Ah, you use OSCacheProvider, not sure their configuration file name, but like for ehcache it is ehcache.xml.

I will also ask why you are using the query-cache. It is useful for data that never changes, because if the results change often, what you will have in the query-cache will be stale pretty quickly.

Mark