dear community,

i have a very strange problem regarding session's update() function:

at one point of my application, users can select a dataset to be editted which is loaded out of the database (via Criteria-API) and then shown in an edit mask.
Nothing special so far.

Now, i have experienced, that - sometimes - the code behind the "save changes"-button produces a new row in the database (with new PK), instead of having the "orignal" row updated. The code for the button does nothing else than just calling Session.Update().

I cannot reproduce this behaviour all time, but it seems to me it has something to do with the "object lifecycle" (so to say); is that possible ?
I looks like, a new row is created by Update() instead of updating the old if the users are lasting too long in the applications edit mask. I assume, there must be some "timestamps" on queried objects telling hibernate to create a new row (with new PK) instead of using the old row.

I have to mention that i'm closing (and throwing away) the session between loading the object and updating.
As i've read in other threads, it should be no problem to close the session between "Object loading -> user edits object -> save object with new session" - am i right ? Or may be this the problem ?

I'm running on NHibernate 1.0.2.0 & MSSQL2000.

hi jojorico,

thank you for the reply.

i will try it... the problem is (as said) i can't reproduce this behaviour all the time; some times it happens, and some it doesn't...

what i don't understand exactly, is:
the instance, i'm trying to update, is not a newly created one; it's loaded out of the DB.
may this be a problem when closing the session-object between these two steps ?



bye

What are the unsaved-values of Id and version or timestamp elements? Do the corresponding properties have appropriate values before calling update?

BTW, did You know that You do not need to call ISession.Update() if changed object was loaded by the same session?

Gert

Hi gert,

the block of the PK is this one in the hbm.xml file:



i don't have any timestamp elements in the record itself. i just throwed the word "timestamp" into because that's what i assumed hibernate holds "in the background".


they should; i'm just loading the object, e.g. modifying the title of the record (a standard string) and then saving it back to the DB.
(nothing special, i'm assuming)? But between loading and saving i'm closing the session.

no, i didn't know that i don't have to call Update() when the object is loaded by the same session :) thank you
but, in my case i'm closing the session between these two calls

I'm not sure how closing session affects the behaviour, but propably the Update() call is needed. Diconnecting session should not make the Update needed.

Anyway, my observations about Save/SaveOrUpdate/Update behaviour:

1. Save - in case of new entity, will create new row in database. If id generator is not "assigned", the object will have new primary key.
2. Update - Associates the entity with session to be updated on next flush.
3. SaveOrUpdate - will try to guess if Save or Update is needed, based on the unsaved-value of <version> (or <timestamp>) or <id> element.

So, if You are using SaveOrUpdate anywhere, maybe You should add sensible unsaved-value to mappings? Otherwise I suspect You call "Save" instead of "Update" somewhere.

Gert

I replied to two of Your questions... I did not find more un-answered ones. Give a glue if there is something more.

Gert

Dear Gert,

Thanks for the reply, or shall i say thanks for the REPLIES!

It's not the first time you reply on a topic of mine as i remember...
As if you were the only active user in this forum ..

10x a lot ...
I don't know if there is anything i can do for you to thank you ..

Regards,
Jojo

Gert,



currently my construction calls Session.Save() when the application edit masks is loaded with a new "item"; when the users are loading the edit mask with an already existing item, the code just calls Session.Update()

I will now try to swith over to Session.SaveOrUpdate(), but i'm not sure if this will fix my problem.
Regarding this "unsaved-value mapping", i'm not exactly sure what you you want me to set it:

which parameter should i try, in your oppinion ? should i just copy&paste this "any|none..." ?

strange to me is the following line from this PDF:


my problem is, that my code will go into beta-production next tuesday, and currently i'm not sure how to handle this issue; as said, most of the time it works out correctly, but sometimes it won't.

thanks in advance.

So, in some cases Your code the edit mask is messing up and erronously thinking that the item is new one. Check out all usage path, including the ones like Create new item, save, edit data for same item, save again... Or create item & save, hit back button edit and save again.



"|" means one of the possible values, so unsaved-value="any" or unsaved-value="none" or unsaved-value="-1", if You set the Id to be -1 when You cerate new unsaved instance.

Gert