[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1523) Rebuild fetches from query-cache hits
Titi Wangsa bin Damhore (JIRA)
noreply at atlassian.com
Sat Oct 9 15:16:01 EDT 2010
[ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1523?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=38668#action_38668 ]
Titi Wangsa bin Damhore commented on HHH-1523:
----------------------------------------------
I've just been hit by the problem and it took me a while to debug it.
I'm using hibernate-core-3.5.6-Final
The code is in org.hibernate.event.def.DefaultLoadEventListener line 254, method "proxyOrLoad"
This is the function that will load the actual object from session or from the db, but it does not check for the existence of the object in second level cache.
Line 360, method createProxyIfNecessary is where the proxy actually get created.
What I've done is copy the whole source code to my class, "CustomLoadEventListener" (I'd prefer inheritance, but the method I want to modify is a private method), and change line 358 - 363
log.trace( "creating new proxy for entity" );
// return new uninitialized proxy
Object proxy = persister.createProxy( event.getEntityId(), event.getSession() );
persistenceContext.getBatchFetchQueue().addBatchLoadableEntityKey(keyToLoad);
persistenceContext.addProxy(keyToLoad, proxy);
return proxy;
to
final Object cached = loadFromSecondLevelCache(event, persister, options);
if (cached != null) {
return cached;
} else {
log.trace("creating new proxy for entity");
// return new uninitialized proxy
final Object proxy = persister.createProxy(event.getEntityId(), event.getSession());
persistenceContext.getBatchFetchQueue().addBatchLoadableEntityKey(keyToLoad);
persistenceContext.addProxy(keyToLoad, proxy);
return proxy;
}
and reconfigure hibernate to use the new LoadEventListener
i am not sure about the performance implication of this, but it gets rid of my "LazyInitializationException"
> Rebuild fetches from query-cache hits
> -------------------------------------
>
> Key: HHH-1523
> URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1523
> Project: Hibernate Core
> Issue Type: New Feature
> Components: caching (L2), core, query-criteria, query-hql, query-sql
> Affects Versions: 3.0.5, 3.1
> Reporter: Vikas Sasidharan
> Attachments: cache_issue.log, QueryCacheIssue.zip
>
>
> I have two domain objects - Employee and Department - and there is a 1:N relationship from Department to Employee. When I join fetch an Employee with its Department, without query cache enabled, it works fine. If I enable query cache for this same query, it bombs with a LazyInitializationException.
> Notes:
> 1) We get this error only if query cache is enabled.
> 2) We observed the same behaviour on both oscache and ehcache
> 3) Calling Hibernate.initialize() explicitly after firing the HQL seems to work. The initialization does not fire an extra query though (it seems to pick it from the cache).
> 4) Setting "lazy=false" on the "many-to-one" mapping also works. However, it wouldn't be acceptable.
> Hibernate version: 3.0.5
> Mapping documents:
> Employee.hbm.xml
> <hibernate-mapping>
> <class name="tavant.platform.test.domain.Employee"
> table="CACHE_ISSUE_EMP" lazy="true" dynamic-update="true" dynamic-insert="true">
> <cache usage="read-write" />
> <id name="id" column="EMP_ID" type="java.lang.Long"
> access="field" unsaved-value="null">
> <generator class="increment" />
> </id>
>
> <property name="name" type="string" update="true"
> insert="true" column="EMP_NAME"/>
> <many-to-one name="department" class="tavant.platform.test.domain.Department"
> cascade="none" outer-join="auto" update="true" insert="true" column="DEPARTMENT_ID"/>
> </class>
> </hibernate-mapping>
>
> Department.hbm.xml
> <hibernate-mapping>
> <class name="tavant.platform.test.domain.Department" table="CACHE_ISSUE_DEP"
> lazy="true" dynamic-update="true" dynamic-insert="true">
>
> <cache usage="read-write" />
> <id name="id" column="DEPARTMENT_ID"
> type="java.lang.Long" access="field">
> <generator class="increment"/>
> </id>
> <property name="name" type="java.lang.String"
> update="false" insert="true" column="NAME"/>
> <bag name="employees" lazy="true"
> inverse="true" cascade="save-update" access="field">
> <cache usage="read-write"/>
> <key column="DEPARTMENT_ID"/>
> <one-to-many class="tavant.platform.test.domain.Employee"/>
> </bag>
> </class>
> </hibernate-mapping>
>
> Code between sessionFactory.openSession() and session.close():
> public Employee getEmployeeWithDepartment(String empName) {
> Session session = null;
> try {
> session = sessionFactory.openSession();
> Employee emp = (Employee) session.createQuery(
> "from Employee e join fetch e.department where e.name = :name")
> .setString("name", empName)
> .setCacheable(true)
> .uniqueResult();
> // If I uncomment the next line, this works (even without
> // firing an extra query)!
> // Hibernate.initialize(emp.getDepartment());
> return emp;
> } finally {
> if (session != null) {
> session.close();
> }
> }
> }
>
> // First load employee and populate cahces
> Employee emp = test.getEmployeeWithDepartment(EMPLOYEE_NAME);
> System.out.println("Employee : " + emp + ", Employee.Department : "
> + emp.getDepartment());
>
> // Now try to make use of the cache
> emp = test.getEmployeeWithDepartment(EMPLOYEE_NAME);
> System.out.println("Employee : " + emp + ", Employee.Department : "
> + emp.getDepartment());
>
> Full stack trace of any exception that occurs:
> org.hibernate.LazyInitializationException: could not initialize proxy - the owning Session was closed
> at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:53)
> at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:84)
> at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:134)
> at tavant.platform.test.domain.Department$$EnhancerByCGLIB$$67b26899.toString(<generated>)
> at java.lang.String.valueOf(String.java:2131)
> at java.lang.StringBuffer.append(StringBuffer.java:370)
> at tavant.platform.test.client.TestPrefetchRelationWithQueryCacheEnabled.main(TestPrefetchRelationWithQueryCacheEnabled.java:116)
>
> Name and version of the database you are using:
> We have noticed this on Oracle and HSQL
> The generated SQL (show_sql=true):
> #First read, goes fine
> Hibernate: select employee0_.EMP_ID as EMP1_0_, department1_.DEPARTMENT_ID as DEPARTMENT1_1_, employee0_.EMP_NAME as EMP2_1_0_, employee0_.DEPARTMENT_ID as DEPARTMENT3_1_0_, department1_.NAME as NAME0_1_ from CACHE_ISSUE_EMP employee0_ inner join CACHE_ISSUE_DEP department1_ on employee0_.DEPARTMENT_ID=department1_.DEPARTMENT_ID where (employee0_.EMP_NAME=? )
> #Prints the Employee and Department fine
> Employee : [Id : 1, name : testEmployee], Employee.Department : [Id : 1, name : testDepartment]
> #Second read bombs!
> org.hibernate.LazyInitializationException: could not initialize proxy - the owning Session was closed
> at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:53)
> at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:84)
> at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:134)
> [..]
> Please have a look at the post [http://forum.hibernate.org/viewtopic.php?t=955839] for more details and follow ups.
> Kindly help. I am attaching an Eclipse Project containing the TestCase. The main file is TestPrefetchRelationWithQueryCacheEnabled.
> Thanks,
> Vikas
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