Hey, I have been experimenting with Hibernate flush modes recently. The motivation was that we experienced premature flushes triggered by Hibernate while retrieving data from the DB, which made us temporarily switch from FlushMode.AUTO to FlushMode.COMMIT or MANUAL to execute some parts of code like validation.
The initial attempt for a more general solution was TRUNK-3069, which switched from the AUTO to COMMIT mode for all transactions. The flush was triggered by us around any method annotated with @Transactional(readOnly=false), but not around @Transactional(readOnly=true). It seemed like a good approach at first, but then I discovered TRUNK-3103. The problem could be eventually resolved by annotating with @Transactional dao methods, which we are considering. Anyway TRUNK-3069 disables much of Hibernate functionality to handle flushes for us and now I think it is not how we should approach the problem. I believe we need to stay with the AUTO flush mode and tune it only when it is needed. Unfortunately, we cannot change the flush mode in any other place than the DAO layer where we have access to hibernate's session, whereas most of the time we actually need to control it in the service layer. So far whenever we needed to execute a service method in the manual flush mode our approach was to go down to the DAO layer, which resulted in such strange constructions as in getDefaultConceptMapType [0], where we put in the DAO layer code that really belonged to the service layer. We have a few possibilities to deal with that. 1. We continue to handle the flush issue in DAOs the way it was before. 2. We have something like CustomSessionFlushTask [1]. 3. We have Context.getFlushMode() and Context.setFlushMode(flushMode). We need our own FlushMode enum so that we don't introduce a dependency on Hibernate in the service layer. 4. We have @ManualFlush annotation to annotate service methods that we want to explicitly execute in the manual flush mode. It's a more elegant variation of 2., but slightly less useful since it requires to create a dedicated method. For instance we have the getConcept method and if we want it to be executed in one place only in the manual flush mode we need to create a second method getConceptInManualFlush for the purpose of annotating it with @ManualFlush. I am really curious what do you think or if there is anyone who has more experience with that. [0] - https://source.openmrs.org/browse/~br=1.9.x/OpenMRS/branches/1.9.x/api/src/main/java/org/openmrs/api/db/hibernate/HibernateConceptDAO.java?r=26243 [1] - https://source.openmrs.org/browse/~br=trunk/Modules/metadatasharing/trunk/src/org/openmrs/module/metadatasharing/api/db/hibernate/CustomSessionFlushTask.java?r=26268 -Rafal _________________________________________ To unsubscribe from OpenMRS Developers' mailing list, send an e-mail to [email protected] with "SIGNOFF openmrs-devel-l" in the body (not the subject) of your e-mail. [mailto:[email protected]?body=SIGNOFF%20openmrs-devel-l]
