[ZODB-Dev] BTrees package problems

[Christian Tismer]

On 22.07.13 16:38, Patrick Strawderman wrote:
> On Jul 20, 2013, at 11:27 PM, Christian Tismer <tismer at stackless.com> wrote:
>
>> - BTrees has a serious bug, see the following example:
>>
>>>>>> from BTrees import OOBTree as BT
>>>>>> t = BT.BTree()
>>>>>> for num in range(100):
>>> ...   k = str(num)
>>> ...   t[k] = k
>>> ...
>>>>>> t._firstbucket._next = None
>>>>>> len(t)
>>> Bus error: 10
>>> (tmp)minimax:doc tismer$
>> So there is either an omission to make t._next() read-only, or a check
>> of its validity is missing.
> Maybe you could open an issue on Github?

Yes I can do that (and fix it).

I was just telling it here because I'd like to know how it is meant to
be.

- should the attributes be exposed at all? (I guess yes)

- are they meant to be writable? (probably not, although that is handy :)

I would actually like to be able to derive from Bucket and implement
copy-on-write semantics for FrozenBTree (not yet existing) without
re-coding much in C, this was the reason while I played around here.

For that purpose (sharing buckets) I need a way to make the _next
pointers indirect.

cheers - chris

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