[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-4550) Document that update-timestamps cache region should not be configured for expiry.

Document that update-timestamps cache region should not be configured for expiry. --------------------------------------------------------------------------------- Key: HHH-4550 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4550 Project: Hibernate ORM Issue Type: Improvement Components: documentation Affects Versions: 3.3.2 Environment: 3.3.2 GA Reporter: Guenther Demetz Assignee: Steve Ebersole Priority: Trivial Fix For: 3.3.x, 3.5.0-Beta-3 Attachments: TestCaseQuryCache.jar When using hibernate's query cache (hibernate.cache.use_query_cache), then it's of fundamental importance to configure the Update Timestamps cache region in a way that his entries survive longer than the cached result sets in the Query cache region. Otherwise queries could return wrong (obsolete) result sets (See attached testcase). This is because the current UpdateTimestampsCache#isUpToDate implementation considers a result-set also as up-to-date, if there are no update-timestamps cached for the interested spaces (tables) at all. It if therefore important to notice that: 1- The Update-Timestamps-Cache-Region elements max-size should be configured higher than the number of tables you have on the db-schema, in manner that he can remember/hold the last update-timestamp for each table. 2- If you use any other eviction policy in the Update-Timestamps-Cache-Region, then you must assure that cached result sets in the Query-cache-region are evicted before relevant update-timestamps are going to be evicted. This fact should be clearly documented somewhere. Thanks G.D.