Fix subtle bug in restore().

The _txn_find() must not stop at the pack boundary when it is called
by restore().  It was originally written for _txn_undo() which isn't
supposed to undo to a transaction across a pack.  But it should be
legal to restore() a transaction with a reference to a data record in
a transaction that was packed.

Fix by adding stop_at_pack flag to _txn_find() and add tests of this
behavior for FileStorage.

src/ZODB/FileStorage.py

@@ -115,7 +115,7 @@
 #   may have a back pointer to a version record or to a non-version
 #   record.
 #
-__version__='$Revision: 1.120 $'[11:-2]
+__version__='$Revision: 1.121 $'[11:-2]
 
 import base64
 from cPickle import Pickler, Unpickler, loads
@@ -786,7 +786,7 @@ class FileStorage(BaseStorage.BaseStorage,
         try:
             prev_pos = 0
             if prev_txn is not None:
-                prev_txn_pos = self._txn_find(prev_txn)
+                prev_txn_pos = self._txn_find(prev_txn, 0)
                 if prev_txn_pos:
                     prev_pos = self._data_find(prev_txn_pos, oid, data)
             old = self._index_get(oid, 0)
@@ -1159,12 +1159,12 @@ class FileStorage(BaseStorage.BaseStorage,
         # Find the right transaction to undo and call _txn_undo_write().
         tid = base64.decodestring(transaction_id + '\n')
         assert len(tid) == 8
-        tpos = self._txn_find(tid)
+        tpos = self._txn_find(tid, 1)
         tindex = self._txn_undo_write(tpos)
         self._tindex.update(tindex)
         return tindex.keys()
 
-    def _txn_find(self, tid):
+    def _txn_find(self, tid, stop_at_pack):
         pos = self._pos
         # XXX Why 39?  Only because undoLog() uses it as a boundary.
         while pos > 39:
@@ -1175,8 +1175,9 @@ class FileStorage(BaseStorage.BaseStorage,
             _tid = h[:8]
             if _tid == tid:
                 return pos
-            status = h[16] # get the c in 8s8sc
-            if status == 'p' or _tid < self._packt:
+            if stop_at_pack:
+                # check the status field of the transaction header
+                if h[16] == 'p' or _tid < self._packt:
                     break
         raise UndoError(None, "Invalid transaction id")
 

src/ZODB/tests/RecoveryStorage.py

@@ -16,8 +16,11 @@
 from ZODB.Transaction import Transaction
 from ZODB.tests.IteratorStorage import IteratorDeepCompare
 from ZODB.tests.StorageTestBase import MinPO, zodb_unpickle, removefs
+from ZODB import DB
+from ZODB.referencesf import referencesf
 from ZODB.FileStorage import FileStorage
 
+import time
 
 class RecoveryStorage(IteratorDeepCompare):
     # Requires a setUp() that creates a self._dst destination storage
@@ -126,3 +129,27 @@ class RecoveryStorage(IteratorDeepCompare):
         self._dst = FileStorage('Dest.fs')
         self._dst.copyTransactionsFrom(self._storage)
         self.compare(self._storage, self._dst)
+        
+    def checkRestoreAcrossPack(self):
+        db = DB(self._storage)
+        c = db.open()
+        r = c.root()
+        obj1 = r["obj1"] = MinPO(1)
+        get_transaction().commit()
+        obj1 = r["obj2"] = MinPO(1)
+        get_transaction().commit()
+
+        self._dst.copyTransactionsFrom(self._storage)
+        self._dst.pack(time.time(), referencesf)
+
+        self._undo(self._storage.undoInfo()[0]['id'])
+
+        # copy the final transaction manually.  even though there
+        # was a pack, the restore() ought to succeed.
+        final = list(self._storage.iterator())[-1]
+        self._dst.tpc_begin(final, final.tid, final.status)
+        for r in final:
+            self._dst.restore(r.oid, r.serial, r.data, r.version, r.data_txn,
+                         final)
+        self._dst.tpc_vote(final)
+        self._dst.tpc_finish(final)

src/ZODB/tests/StorageTestBase.py

@@ -196,7 +196,7 @@ class StorageTestBase(unittest.TestCase):
     
     # The following methods depend on optional storage features.
 
-    def _undo(self, tid, oid):
+    def _undo(self, tid, oid=None):
         # Undo a tid that affects a single object (oid).
         # XXX This is very specialized
         t = Transaction()
@@ -205,6 +205,7 @@ class StorageTestBase(unittest.TestCase):
         oids = self._storage.transactionalUndo(tid, t)
         self._storage.tpc_vote(t)
         self._storage.tpc_finish(t)
+        if oid is not None:
             self.assertEqual(len(oids), 1)
             self.assertEqual(oids[0], oid)
         return self._storage.lastTransaction()