Re: Migrating to BTrees 4.x

On Sat, Nov 26, 2016 at 8:55 PM, David Glick <[email protected]> wrote:

> On 11/20/16 9:31 AM, Jim Fulton wrote:
>
>
>
> On Sun, Nov 20, 2016 at 12:11 PM, Jason Madden <
> [email protected]> wrote:
>
>>
>> > On Nov 20, 2016, at 10:25, Jim Fulton <[email protected]> wrote:
>> >
>> >> But it seems safe to say there are at least some discrepancies and
>> some clear bugs in the handling of unorderable objects still.
>> >
>> > Yup.  Partly I suspect this is the related to the many ways one can
>> express comparison in Python. (Talk about more than one way to do it.)
>> >
>> > I think this may also be related to inserting into an empty BTree,
>> where there's noting to compare the new item to and thus no opportunity to
>> fail.  Perhaps, if we're paranoid, we should compare the first item to
>> itself on insert.
>>
>> You're right, under Python 3, this only happens in an empty tree. Once
>> there are other items, you get "TypeError: unorderable types: Bad() < ..."
>> errors. Under Python 2, of course, no such luck.
>>
>> > In any case, I think the focus for this seat belt should be on
>> insertion.
>>
>> I've opened a series of issues in the repository (
>> https://github.com/zopefoundation/BTrees/issues) that I think capture
>> the discussion here.
>
>
> Thanks.
>
>
>> I may be able to come up with some PRs over the next week for them.
>>
>
> It looks like David was going to try a fix. David, did this discussion
> help?
>
>
> I finally had time to look at this again today. I've got a branch
> (check-obj-cmp-on-insert-only) that makes the CPython implementation only
> do the check on insertion so it's more like the Python implementation.
> However, trying to delete None as a key still raises "TypeError:
> unorderable types: NoneType() < NoneType()" in Python 3 (both
> implementations; we weren't testing the pure-Python implementation on
> Python 3 except for PyPy3). This is presumably Python itself complaining
> when trying to search for the bucket. I suppose the workaround is: for the
> search during delete only, if the keys use default comparison, compare them
> using a function that mimics Python 2 comparison and thus skips the check
> for unorderable types. Gaaa...
>

Well

a) We don't have a way to use databases created in Python 2 in Python 3 (do
we?).

b) It's impossible to insert None as a key in Python 3.

If a & b, then this seems to be a non-issue and the tests should be Python
version dependent.

Jim




-- 
Jim Fulton
http://jimfulton.info

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