Also it may help to search google for “ghost updates nhibernate” https://www.google.co.uk/search?q=ghost+u%5Bdates+nhibernate&oq=ghost+u%5Bdates+nhibernate&aqs=chrome..69i57j0.7383j0j7&sourceid=chrome&espv=210&es_sm=93&ie=UTF-8
Rippo From: [email protected] [mailto:[email protected]] On Behalf Of Vinicius G. D. Menezes Sent: 05 April 2014 14:15 To: [email protected] Subject: Re: [nhusers] Re: How to prevent DB update if value not changed Hi Peter, I've been working with different projects at the company I work for and I could hint you that the updates also depend on the lifecycle of your ISession. Since ISession can only work for one Thread, you might be in a position of creating and destroying it too early, therefore making nhibernate update your objects without necessity. Have you tried implementing IComparable, overding .GetHashCode() and .Equals() methods and interfaces for your objects? NHibernate compares the objects to track it's differences, sometimes a reference difference can change your object Hashcode making NHibernate "think" it's an update. Generally Value Objects will need that kind of implementation I suggested. Would you be able to detail your problem a bit more? Vinicius Menezes On Mon, Mar 17, 2014 at 7:25 AM, Carel Blumenstock <[email protected]<mailto:[email protected]>> wrote: We are using fluent mappings, in order to have changes to child lists not trigger a version update of the parent we had to state as such in mapping like Not.OptimisticLock(), hth Op maandag 10 maart 2014 20:12:27 UTC+1 schreef Peter V: We're using NHibernate where the DB can be updated by either a user (via GUI) or external systems (via background message handlers). Our DB schema, by the way, uses a lot of joins. So what can happen is, we can get multiple background messages that provide exactly the same information, and so trigger repeated writes to the DB across all the joined tables that don't actually change anything (other than the version). What I'm trying to figure out is, for performance reasons, is there a way to prevent NH from updating the DB if a value hasn't changed? So when an object's setter is called, NH should first read the current value from the DB, and if the new value is the same, do nothing; if different or not found, then save/update it. Thanks, Peter P.S. I was looking through other postings that talked about Session.Merge(): - https://groups.google.com/forum/#!searchin/nhusers/saveorupdate$20merge/nhusers/6_8uwwl5KX4/11Pef_FreXgJ - http://stackoverflow.com/questions/4725785/stop-hibernate-from-updating-collections-when-they-have-not-changed ...and I thought Merge() would do what I needed. But reading some more, I see that Merge is really more about whether the instance is already associated with the current session. (Merge will... "Copy the state of the given object onto the persistent object with the same identifier. If there is no persistent instance currently associated with the session, it will be loaded.") So I'm confused - will Merge() do what I need? Or am I looking in the wrong place? -- You received this message because you are subscribed to the Google Groups "nhusers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]<mailto:[email protected]>. To post to this group, send email to [email protected]<mailto:[email protected]>. Visit this group at http://groups.google.com/group/nhusers. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "nhusers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]<mailto:[email protected]>. To post to this group, send email to [email protected]<mailto:[email protected]>. Visit this group at http://groups.google.com/group/nhusers. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "nhusers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/nhusers. For more options, visit https://groups.google.com/d/optout.
