.

wcfs/testprog/treegen.py

@@ -114,14 +114,19 @@ class ZCtx(object):
         zctx.root  = zctx.zconn.root()
 
         # init root['treegen/values'] = {} v -> ZBlk(v)
-        # TODO don't generate if already there
-        zctx.valdict = zctx.root['treegen/values'] = PersistentMapping()
+        valdict = zctx.root.get('treegen/values', None)
+        if valdict is None:
+            valdict = zctx.root['treegen/values'] = PersistentMapping()
         valv = b'abcdefghi'
         for v in valv:
+            zblk = valdict.get(v, None)
+            if zblk is not None and zblk.loadblkdata() == v:
+                continue
             zblk = ZBlk()
             zblk.setblkdata(v)
-            zctx.valdict[v] = zblk
-        commit('treegen/values: init %r' % valv)
+            valdict[v] = zblk
+        zctx.valdict = valdict
+        commit('treegen/values: init %r' % valv, skipIfEmpty=True)
 
     # close release resources associated with zctx.
     def close(zctx):
@@ -343,11 +348,13 @@ def patch(d, diff, verify):
 
 
 # commit commits current transaction with description.
-def commit(description): # -> tid
+def commit(description, skipIfEmpty=False): # -> tid | None
     txn = transaction.get()
+    if skipIfEmpty and len(txn._resources) == 0:
+        return None
     txn.description = description
     # XXX hack to retrieve committed transaction ID via ._p_serial of object changed in this transaction
-    assert len(txn._resources) == 1
+    assert len(txn._resources) == 1, txn._resources
     zconn = txn._resources[0]
     assert isinstance(zconn, Connection)
     assert len(zconn._registered_objects) > 0