_collect_revs(): It's possible that the metadata and txnoids entries

for an object revision in objrevs got collected away when the entire
object was refcounted to zero.  Be more defensive about find and
deleting these records.

Also, truncate the packtime table before writing the new record, to
maintain the database invariant that there is only allowed one entry
in this table at a time.

lib/python/BDBStorage/BDBFullStorage.py

@@ -15,7 +15,7 @@
 """Berkeley storage with full undo and versioning support.
 """
 
-__version__ = '$Revision: 1.51 $'.split()[-2:][0]
+__version__ = '$Revision: 1.52 $'.split()[-2:][0]
 
 import sys
 import time
@@ -1452,13 +1452,24 @@ class Full(BerkeleyBase, ConflictResolvingStorage):
                 # with it again.  Otherwise, we can remove the metadata record
                 # for this revision and decref the corresponding pickle.
                 if oldserial <> ZERO:
-                    metadata = self._metadata[oid+oldserial]
-                    self._metadata.delete(oid+oldserial, txn=txn)
-                    # Decref the pickle
-                    self._decrefPickle(oid, metadata[16:24], txn)
-                    # Remove the txnoids entry.  We have to use a cursor here.
-                    ct.set_both(oldserial, oid)
-                    ct.delete()
+                    # It's possible this object revision has already been
+                    # deleted, if the oid points to a decref'd away object
+                    try:
+                        metadata = self._metadata[oid+oldserial]
+                    except KeyError:
+                        pass
+                    else:
+                        self._metadata.delete(oid+oldserial, txn=txn)
+                        # Decref the pickle
+                        self._decrefPickle(oid, metadata[16:24], txn)
+                    try:
+                        # Remove the txnoids entry.  We have to use a cursor
+                        # here because of the set_both().
+                        ct.set_both(oldserial, oid)
+                    except db.DBNotFoundError:
+                        pass
+                    else:
+                        ct.delete()
                 co.delete()
                 rec = co.next()
         finally:
@@ -1467,6 +1478,7 @@ class Full(BerkeleyBase, ConflictResolvingStorage):
         # Note that before we commit this Berkeley transaction, we also need
         # to update the packtime table, so we can't have the possibility of a
         # race condition with undoLog().
+        self._packtime.truncate(txn)
         self._packtime.put(packtid, PRESENT, txn=txn)
 
     def _decrefPickle(self, oid, lrevid, txn):

lib/python/BDBStorage/Full.py

@@ -15,7 +15,7 @@
 """Berkeley storage with full undo and versioning support.
 """
 
-__version__ = '$Revision: 1.51 $'.split()[-2:][0]
+__version__ = '$Revision: 1.52 $'.split()[-2:][0]
 
 import sys
 import time
@@ -1452,13 +1452,24 @@ class Full(BerkeleyBase, ConflictResolvingStorage):
                 # with it again.  Otherwise, we can remove the metadata record
                 # for this revision and decref the corresponding pickle.
                 if oldserial <> ZERO:
-                    metadata = self._metadata[oid+oldserial]
-                    self._metadata.delete(oid+oldserial, txn=txn)
-                    # Decref the pickle
-                    self._decrefPickle(oid, metadata[16:24], txn)
-                    # Remove the txnoids entry.  We have to use a cursor here.
-                    ct.set_both(oldserial, oid)
-                    ct.delete()
+                    # It's possible this object revision has already been
+                    # deleted, if the oid points to a decref'd away object
+                    try:
+                        metadata = self._metadata[oid+oldserial]
+                    except KeyError:
+                        pass
+                    else:
+                        self._metadata.delete(oid+oldserial, txn=txn)
+                        # Decref the pickle
+                        self._decrefPickle(oid, metadata[16:24], txn)
+                    try:
+                        # Remove the txnoids entry.  We have to use a cursor
+                        # here because of the set_both().
+                        ct.set_both(oldserial, oid)
+                    except db.DBNotFoundError:
+                        pass
+                    else:
+                        ct.delete()
                 co.delete()
                 rec = co.next()
         finally:
@@ -1467,6 +1478,7 @@ class Full(BerkeleyBase, ConflictResolvingStorage):
         # Note that before we commit this Berkeley transaction, we also need
         # to update the packtime table, so we can't have the possibility of a
         # race condition with undoLog().
+        self._packtime.truncate(txn)
         self._packtime.put(packtid, PRESENT, txn=txn)
 
     def _decrefPickle(self, oid, lrevid, txn):