use of org.hibernate.cache.UpdateTimestamp

[aricci]

hi all,
i am using JBossCache (1.4.1.SP3) and i am trying to understand how it works.
looking at the printDetails() function of the JBossCache bean in the JBoss JMX-Console, i have noticed that org.hibernate.cache.UpdateTimestamp..item is updated everytime with the timestamp of the last modification of the corresponding table. i would like to know why this timestamp is needed by JBossCache.

thank you very much
Andrea

[brian.stansberry]

It's not needed by JBoss Cache per se, it's needed by Hibernate. Briefly mentioned in the Hibernate docs at http://www.hibernate.org/hib_docs/v3/reference/en/html/performance.html#performance-querycache.

Basically, Hibernate tracks the update timestamp for an entity type so it can know if any cached query results may have been invalidated due to a change in the queried entities.