[jboss-jira] [JBoss JIRA] Commented: (JBCACHE-956) Use LockParentForChildInsertRemove flag to control Optimistic node versioning

[Manik Surtani (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBCACHE-956?page=comments#action_12351941 ] 
            
Manik Surtani commented on JBCACHE-956:
---------------------------------------

This actually does not work for optimistic locking and here's why.

Whenever a node is added, the following happens:

1)  Parent read into TX Workspace (call this parentW)
2)  New node created in workspace
3)  New node added to parentW's child map
4)  At commit, parentW's child map is used to overwrite parent's child map

Because of step 4, there is no way we can support concurrent adds/removes on parent nodes without implementing a diffing/merging algorithm for child maps.  Step 4 has to be an overwrite since we don't know whether part of the tx also involved removing children unless we have a merging algo.

I agree that this is pretty crap and we do need something more sophisticated here, but I don't think it is correct to do in 1.4.1.SP1.  

See JBCACHE-961

> Use LockParentForChildInsertRemove flag to control Optimistic node versioning
> -----------------------------------------------------------------------------
>
>                 Key: JBCACHE-956
>                 URL: http://jira.jboss.com/jira/browse/JBCACHE-956
>             Project: JBoss Cache
>          Issue Type: Feature Request
>      Security Level: Public(Everyone can see) 
>    Affects Versions: 1.4.1.GA
>            Reporter: Brian Stansberry
>         Assigned To: Manik Surtani
>             Fix For: 1.4.1.SP1
>
>
> See JBCACHE-955 for background on locking issues related to inserting and removing child nodes.
> This JIRA is to look into using JBCACHE-955's LockParentForChildInsertRemove flag to control whether the insertion or removal of a child node affects a workspace node's data version.

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