[ZODB-Dev] weird BTrees KeyError (CVS HEAD)

[Christian Reis]

Hi there,

I'm trying to track down a bug with IC, and since I know Jeremy and Tim
have been working on BTrees lately, I'll try and take advantage of the
freshness of memory. I haven't been able to reproduce the bug in a
simple testcase (after hours of trying), so I'll try and paste out the
simple error.

I have a BTree (held by ListIndex for the IC-interested) that uses
PersistentLists as keys. I'm running into the following situation:

    >>> pprint.pprint(list(index.keys()))
    [[<OutPayment -856997433 at 0x139009928: None (10)>],
     [<OutPayment -184497724 at 0x139009744: Pergunte AO JÃO (9)>],
     [<OutPayment -996636965 at 0x135391528:  (7)>, 
      <OutPayment 685848900 at 0x135391624:  (8)>],
     [<OutPayment 76244553 at 0x139117880:  (6)>],
     [<OutPayment 233388722 at 0x139019608: 231232131 (4)>],
     [<OutPayment 479303017 at 0x139596568: 23123231 (3)>],
     [<OutPayment -984951907 at 0x139600696: 21331421 (2)>],
     [<OutPayment 310965931 at 0x139119824: XXX XXX XXX 123 (1)>]]
     
    >>> print x
    [<OutPayment -856997433 at 0x139009928: None (10)>]
    >>> print x in index.keys()
    1
    >>> print x in list(index.keys())
    1

    >>> print index.get(key)
    None
    >>> print index[x]
    Traceback (most recent call last):
      File "<console>", line 1, in ?
      KeyError: [<OutPayment -856997433 at 0x139009928: None (10)>]

I've tried to track this down, but it seems very odd. The worst part is
that *sometimes* it works -- once every 4 or 5 runs no keyerror is
produced. The only thing really special here is that these objects have
custom hash functions, but I don't think hash is used in this case.

This was happening before, and I moved to BTrees from CVS HEAD, hopeful
that the problem was fixed, but using yesterday's version, I still get
the same errors.

I can provide a FileStorage that contains the problematic BTree along
with a script that reproduces the error, if it's helpful.

Take care,
--
Christian Reis, Senior Engineer, Async Open Source, Brazil.
http://async.com.br/~kiko/ | [+55 16] 261 2331 | NMFL