[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2545) Query cache dosen't work with queries that return Collections
Query cache dosen't work with queries that return Collections
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Key: HHH-2545
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2545
Project: Hibernate3
Issue Type: Bug
Components: core
Affects Versions: 3.2.3
Environment: Windows XP, jdk1.5.0_06
Reporter: Jacek halat
Priority: Critical
Attachments: QueryCacheBag.zip
If :
* second level cache is enabled
* query cache is enabled
* query return collection of objects
first query execution return collection of objects, but second, third etc, call
returns.... Collection with null element (collection size is corect, but collection
contains onlu null elements instead of objects).
I do some investigation and found, that if query cache is enabled,
StandardQueryCache.put() method is caled. This method store cachable object in queryCache.
Cachable is List with timestamp as first element and disassembled Entities as rest
elements.
If List contains only 1 element this line is called:
if ( returnTypes.length==1 ) {
cacheable.add( returnTypes[0].disassemble( result.get(i), session, null ) );
}
else {
cacheable.add( TypeFactory.disassemble( (Object[]) result.get(i), returnTypes, null,
session, null ) );
}
if query returns collection, CollectionType.disassemble() is called, this methods looks
like:
public Serializable disassemble(Object value, SessionImplementor session, Object owner)
throws HibernateException {
//remember the uk value
//This solution would allow us to eliminate the owner arg to disassemble(), but
//what if the collection was null, and then later had elements added? seems unsafe
//session.getPersistenceContext().getCollectionEntry( (PersistentCollection) value
).getKey();
final Serializable key = getKeyOfOwner(owner, session);
if (key==null) {
return null;
}
else {
return getPersister(session)
.getKeyType()
.disassemble( key, session, owner );
}
}
This method is called with owner=null, and value=first element from collection.
IF cource because owner==null getKeyOfOwner returns null and null is stored in
queryCache!!!!!!!!!!! (and no warning or error is logged or exception is thrown), so user
can think, that query is corrcectly cached.
Now when query is executed second time, cached collection is returned, but it contains
only null as value!!!!!
JUnit test included (QueryCacheBagTest)
For me this is critical bug, because it's impossible to work with qached query in
clustered environment, so system performance is now very, very low.
I hope that this issue wil be resolved as soon possible.
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