[hibernate-issues] [Hibernate-JIRA] Created: (HHH-4551) Query caching becomes very ineffective on conversations with extended sessions.

[Guenther Demetz (JIRA)]

Query caching becomes very ineffective on conversations with extended sessions.
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                 Key: HHH-4551
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4551
             Project: Hibernate Core
          Issue Type: Improvement
          Components: caching (L2)
    Affects Versions: 3.3.2
         Environment: 3.3.2 GA
            Reporter: Guenther Demetz


Hibernate's query cache (hibernate.cache.use_query_cache) always takes the initial session timestamp
for storing the result-set timestamp.


---------------------------------------------
StandardQueryCache.java (put-method):
...
Long ts = new Long( session.getTimestamp() );
...
cacheable.add( ts );
---------------------------------------------

When extending a session for a whole conversation (Book "Java Persistence with Hibernate" chapter. 11.2.3), the sessions initial timestamp get's soon rather deferred to the time a new query result set is produced actually. Immagine a long conversation which lasts more than 5 minutes.
This leads to the effect, that often still valid result-set-cache entries are considered not up-to-date because of a flushed update action occured during the conversation.
Furthermore the new obtained query-resultset (note that this query now considers the last update!) 
is subsequently again put in cache still with the original and outdated sessions-timestamp:  That's for the birds !


Proposal:
Why not take the current timestamp instead?
For example calling:

Long ts = new Long( cacheRegion.nextTimestamp());


best regards
Guenther D.

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