Re: [ZODB-Dev] Corrupted OOTreeSet - strange behavior
On 18 July 2011 11:07, Pedro Ferreira jose.pedro.ferre...@cern.ch wrote: Hello, I have an OOTreeSet in my DB that is behaving a bit funny (seems to be corrupted). I thought I could get some more information by performing a sanity check, but that doesn't seem to help a lot: c in s False c in list(s) True s._check() Shouldn't there be an error in this case? TreeSets are essentially BTrees with only keys. This means that the members of a TreeSet must have a stable ordering. I suspect that that c's class does not define the comparison methods (such as __lt__) which means under Python 2 it falls back to the default ordering based on object id (Python 3 will raise a TypeError instead, avoiding this problem.) With ZODB an object's Python id (the memory address of the object) will change whenever it is reloaded, i.e. across restarts, after invalidation or removal from the cache. A TreeSet is ordered, so the contains comparison only needs to perform a lookup to see whether an object is a member of the TreeSet, as the id of the object has changed, its expected position has changed and it is not found. A list is not ordered, so it has to check against every object in the list to test for containment. The _check() method only confirms that the BTree/TreeSets's internal data structure is consistent. It does not check every item. So it does not show an error in this case. You will need to add comparison methods for the class of the objects you are storing in the TreeSet and then rebuild the TreeSets. Laurence ___ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
Re: [ZODB-Dev] Corrupted OOTreeSet - strange behavior
TreeSets are essentially BTrees with only keys. This means that the members of a TreeSet must have a stable ordering. I suspect that that c's class does not define the comparison methods (such as __lt__) which means under Python 2 it falls back to the default ordering based on object id (Python 3 will raise a TypeError instead, avoiding this problem.) With ZODB an object's Python id (the memory address of the object) will change whenever it is reloaded, i.e. across restarts, after invalidation or removal from the cache. Yes, I know that. But I have a __cmp__ function defined, based on an object property that never changes. That should be enough, no? The _check() method only confirms that the BTree/TreeSets's internal data structure is consistent. It does not check every item. So it does not show an error in this case. I see. I thought it did some order checking as well. Thanks, Pedro -- José Pedro Ferreira Software Developer, Indico Project http://indico-software.org +---+ + '``'--- `+ CERN - European Organization for Nuclear Research + |CERN| / + 1211 Geneve 23, Switzerland + ..__. \. + IT-UDS-AVC + \\___.\ + Office: 513-1-005 + /+ Tel. +41227677159 +---+ ___ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
Re: [ZODB-Dev] Corrupted OOTreeSet - strange behavior
On 18 July 2011 13:08, Pedro Ferreira jose.pedro.ferre...@cern.ch wrote: TreeSets are essentially BTrees with only keys. This means that the members of a TreeSet must have a stable ordering. I suspect that that c's class does not define the comparison methods (such as __lt__) which means under Python 2 it falls back to the default ordering based on object id (Python 3 will raise a TypeError instead, avoiding this problem.) With ZODB an object's Python id (the memory address of the object) will change whenever it is reloaded, i.e. across restarts, after invalidation or removal from the cache. Yes, I know that. But I have a __cmp__ function defined, based on an object property that never changes. That should be enough, no? I think it should, but are you absolutely certain it never changes? Does list(s) == sorted(list(s)) and does list(s) == list(OOTreeSet(s))? Laurence ___ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
