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POGrails hibernate session in batches
 

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  1. POGrails hibernate session in batches
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    <p>GORM works fine out of the box as long as there is no batch with more than 10.000 objects. Without optimisation you will face the outOfMemory problems.</p> <p>The common solution is to flush() and clear() the session each n (e.g.n=500) objects:</p> <pre><code>Session session = sessionFactory.currentSession Transaction tx = session.beginTransaction(); def propertyInstanceMap = org.codehaus.groovy.grails.plugins.DomainClassGrailsPlugin.PROPERTY_INSTANCE_MAP Date yesterday = new Date() - 1 Criteria c = session.createCriteria(Foo.class) c.add(Restrictions.lt('lastUpdated',yesterday)) ScrollableResults rawObjects = c.scroll(ScrollMode.FORWARD_ONLY) int count=0; while ( rawObjects.next() ) { def rawOject = rawObjects.get(0); fooService.doSomething() int batchSize = 500 if ( ++count % batchSize == 0 ) { //flush a batch of updates and release memory: try{ session.flush(); }catch(Exception e){ log.error(session) log.error(" error: " + e.message) throw e } session.clear(); propertyInstanceMap.get().clear() } } session.flush() session.clear() tx.commit() </code></pre> <p>But there are some problems I can't solve:</p> <ol> <li>If I use currentSession, then the controller fails because of session is empty</li> <li>If I use sessionFactory.openSession(), then the currentSession is still used inside FooService. Of cause I can use the session.save(object) notation. But this means, that I have to modify fooService.doSomething() and duplicate code for single operation (common grails notation like fooObject.save() ) and batch operation (session.save(fooObject() ).. notation).</li> <li>If I use Foo.withSession{session->} or Foo.withNewSession{session->}, then the objects of Foo Class are cleared by session.clear() as expected. All the other objects are not cleared(), what leads to memory leak.</li> <li>Of cause I can use evict(object) to manualy clear the session. But it is nearly impossible to get all relevant objects, due to autofetching of assosiations.</li> </ol> <p>So I have no idea how to solve my problems without making the FooService.doSomething() more complex. I'm looking for something like withSession{} for all domains. Or to save session at the begin (Session tmp = currentSession) and do something like sessionFactory.setCurrentSession(tmp). Both doesn't exists!</p> <p>Any idea is wellcome!</p>
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    1. COThis looks like work that should be done entirely in a service method. If within the service method, you use `currentSession`, does your controller still work?
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    2. COI agree with @doelleri. Services are the wright place to do it. Also, remember that by default they are transactional, if you want to handle manually the status, use `Domain.withTransaction` and set the `static transactional = false` or let the service take care of the commit/rollback.
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    3. COThe code I posted there is already inside a service method. Yes I could use the transaction context of the service method, but it will not solve my problem. @doelleri - The answer to your question is: the controller brakes, so that the user can't do anything more in the application except to close the browser. (see problem 1)
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