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From Marcel Reutegger <marcel.reuteg...@gmx.net>
Subject Re: Problems with concurrent sessions
Date Fri, 08 Jul 2005 08:06:40 GMT
Hi Nicolas,

Nicolas Belisle wrote:
> What is the session isolation level [ref. 
> http://www.unix.org.ua/orelly/java-ent/ebeans/ch08_03.htm] by default ?

the default is read commited.

> Is it configurable ?

no, but you may use locks to further control isolation level.

a session in jackrabbit will see changes as soon as they are committed. 
you may however use locks to achieve a higher isolation level. 
successfully setting a lock on a node will give you repeatable read for 
that subtree. if you do that on the root node you get serializable 
isolation level.

> At least, Jackrabbit seems to prevent dirty reads 
> (determined from tests). Is there any documentation regarding isolation 
> level ? I think it is a very important topic...

Unfortunately there is currently no documentation on isolation levels, 
but this thread may be a good starting point to collect all relevant 
information and then put it into a nice xdoc or wiki page.

> Example :
> A : open session
> A : read nodes "test" & "test2"
> B : open session
> A : delete nodes "test" & "test2"
> B : save session //WHAT SHOULD HAPPEN ??
> B : logout
> A : read nodes "test" & "test2" //WHAT SHOULD HAPPEN ??
> A : logout

I cannot quite follow you here. thread B seems to save a session without 
having made changes to it? that means 'B : save session' is basically no 
op. But I guess that's not what you want to know...

regards
  marcel

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