On Monday 02 June 2003 08:18 pm, Andr� van Toly wrote:This is quite possible (at least for new installation) and it's a nice to havePierre van Rooden heeft op maandag, 2 jun 2003 om 16:21 (Europe/Amsterdam) het volgende geschreven:
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[1c] Since MMBase has no locking mechanism, the wizard maintains a 'original data' xml tree. The Dove uses this tree to validate changes (so if someone changes the object, the wizard issues an error). Perhaps a less memory-consuming way can be found to check on changes in an object (so the original data tree is not needed), but I gather this would either require versioning (or 'last modified dates'), or another method to make comparison easy (hashcodes?).
All nodes in MMBase have at least two fields: number and owner. These are deeply rooted in the core but is it not worth investigating to add an extra field 'updated' or 'modified'? Or would that involve a complete rewrite of MMBase?
but i don't think this solves the problem. it still doesn't allow locking.
it is something like a timestamp field
Some thoughts: I think it is difficult to manage and implement the locking of a node (when do you lock a node and when will it be released? setting a lock boolean in the database would require a database commit while retrieving the node, but when do you know that a node is being retrieved for editing? put a boolean lock in memory then?). But it is easier to check whether a node is updated or not (a check for updated and a commit when you commit the changed node). Locking a node has to be managed at a low level in MMBase, the same can be done with a mechanism that checks for an update but doesn't necessary has to be at a low level. Checking whether a node is updated could easily be implemented in every kind of editor currently available in MMBase, also on a voluntary or optional basis.
Kees has a point that you would lose your edits (which you won't when you lock a node cause you would not be able to edit it), but i believe that a mechanism with updated or modified fields is easier to implement in all the current available editors in MMBase.
---Andr�
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