HBTreeFolder2 fixes
There's no magic in this patch series: it is known that HBTreeFolder2 has limitations about the ids that can be set without conflict, and this can't be fixed without causing compatibility issues with existing data.
What I suggest here is:
- some optimization
- bug fixes
- detect id conflicts before causing data loss
I also started to study this product when trying to use a newer version of ZODB. Recent BTrees fails on the following line of _setOb:
if len(id_list) == 1 and not htree.has_key(None):(None is not valid key for comparison)
One of the commit removes _tree_list. I hope this does not make getTreeIdList too slow.
The long story about id conflicts is that a HBTreeFolder2 can't store 2 objects <A> and <A>-<B> where <A> does not contain '-', and that's the rule followed by _getOb/_setOb/_delOb. However:
- Conflicts are detected by testing the type of the value, which means HBTreeFolder2 can't store values of the same type as the one it uses internally (i.e. OOBTree).
- For performance reasons, _htree_iteritems and getTreeIdList use a stricter rule: they assume there can't be 2 objects <A> and <A>-<B>, regardless of the presence of a separator in <A>. Maybe this rule should be enforced in _setOb.