[ZODB-Dev] PersistentMapping good for large numbers of objects?

[Tim Peters]

[Steve Alexander]
> Or, the code could ask the BTree for its __len__() after the update,
> and then store that.
>
> I don't think I use the update method often enough for this to be
> an issue.

Heh.  If we supply a canned object, people will take that (reasonably
enough) as a claim that the canned object is suitable for all BTree
purposes.  That your particular app is happy to abide a grossly inefficient
implementation of .update() doesn't help me when I get a bug report
complaining that someone else's app isn't so tolerant.

"someone who wants it enough is welcome to write it" is still my take on it,
and if that someone decides to implement update inefficiently-- or not to
implement update at all --they should document that up-front.