- Collector #1899: fixed migration issue when using export/import for
        ZCatalog instances

doc/CHANGES.txt

@@ -42,6 +42,9 @@ Zope Changes
 
     Bugs Fixed
 
+      - Collector #1899: fixed migration issue when using export/import for
+        ZCatalog instances
+
       - Collector #1871: Applied patch to support lists with records using
         ZTUtils.make_query()
 

lib/python/Products/PluginIndexes/common/UnIndex.py

@@ -175,7 +175,15 @@ class UnIndex(SimpleItem):
 
             except AttributeError:
                 # index row is an int
+                try:
                     del self._index[entry]
+                except KeyError:
+                    # XXX swallow KeyError because it was probably
+                    # removed and then _length AttributeError raised
+                    pass 
+                if isinstance(self.__len__, BTrees.Length.Length):
+                    self._length = self.__len__
+                    del self.__len__ 
                 self._length.change(-1)
 
             except:
@@ -202,6 +210,13 @@ class UnIndex(SimpleItem):
         # an IntSet and stuff it in first.
         if indexRow is _marker:
             self._index[entry] = documentId
+            # XXX _length needs to be migrated to Length object
+            try:
+                self._length.change(1)
+            except AttributeError:
+                if isinstance(self.__len__, BTrees.Length.Length):
+                    self._length = self.__len__
+                    del self.__len__
                 self._length.change(1)
         else:
             try: indexRow.insert(documentId)