[ZODB-Dev] What's the deal with _p_independent?

[Stefan H. Holek]

BTrees.Length is used in many places to maintain the length of  
BTrees. Just the other day it was added to zope.app.container.btree.  
While I am happy about the speed improvements, I am concerned about  
the fact that BTrees.Length declares itself _p_independent. I'd like  
some clarification about what happens in a conflict resolution  
situation, when the Length is _p_independent but the BTree itself is  
not. I *think* that with MVCC this means a read-conflict will reset  
the BTree, but not it's Length.

All I could google up is this from 2004: http://mail.zope.org/ 
pipermail/zodb-dev/2004-April/007269.html

Now, do we need another Length class or is BTrees.Length just fine  
and dandy?

Thanks,
Stefan


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