prototype take 1: add version_id / vid everywhere (rebased)

8 files changed, 266 insertions, 187 deletions

diff --git a/src/carquinyol/__init__.py b/src/carquinyol/__init__.py
index e69de29..d53da54 100644
--- a/src/carquinyol/__init__.py
+++ b/src/carquinyol/__init__.py
@@ -0,0 +1,8 @@
+import logging
+import decorator
+
+@decorator.decorator
+def trace(f, *args, **kwargs) :
+    logging.debug("%s(%s)" % (f.__name__, ", ".join([repr(a) for a in args]+['%s=%r' % (k,v) for (k,v) in kwargs.items()]))),
+    return f(*args, **kwargs)
+
diff --git a/src/carquinyol/datastore.py b/src/carquinyol/datastore.py
index 41b16b5..9b66ccd 100644
--- a/src/carquinyol/datastore.py
+++ b/src/carquinyol/datastore.py
@@ -27,6 +27,7 @@ import gobject
 
 from sugar import mime
 
+from carquinyol import trace
 from carquinyol import layoutmanager
 from carquinyol import migration
 from carquinyol.layoutmanager import MAX_QUERY_LIMIT
@@ -62,6 +63,7 @@ class DataStore(dbus.service.Object):
             layout_manager.set_version(layoutmanager.CURRENT_LAYOUT_VERSION)
             layout_manager.index_updated = False
         elif layout_manager.get_version() == 1:
+            migration.migrate_from_1()
             layout_manager.set_version(layoutmanager.CURRENT_LAYOUT_VERSION)
             layout_manager.index_updated = False
 
@@ -86,120 +88,127 @@ class DataStore(dbus.service.Object):
         self._optimizer = Optimizer(self._file_store, self._metadata_store)
 
     def _rebuild_index(self):
-        uids = layoutmanager.get_instance().find_all()
-        logging.debug('Going to update the index with uids %r' % uids)
-        gobject.idle_add(lambda: self.__rebuild_index_cb(uids),
+        uvids = layoutmanager.get_instance().find_all()
+        logging.debug('Going to update the index with uvids %r' % uvids)
+        gobject.idle_add(lambda: self.__rebuild_index_cb(uvids),
                             priority=gobject.PRIORITY_LOW)
 
-    def __rebuild_index_cb(self, uids):
-        if uids:
-            uid = uids.pop()
+    def __rebuild_index_cb(self, uvids):
+        if uvids:
+            (uid,vid) = uvids.pop()
 
-            logging.debug('Updating entry %r in index. %d to go.' % \
-                          (uid, len(uids)))
+            logging.debug('Updating entry (%r,%r) in index. %d to go.' % \
+                          (uid, vid, len(uvids)))
 
-            if not self._index_store.contains(uid):
+            if not self._index_store.contains(uid,vid):
                 try:
-                    props = self._metadata_store.retrieve(uid)
-                    self._index_store.store(uid, props)
+                    props = self._metadata_store.retrieve(uid,vid)
+                    self._index_store.store(uid, vid, props)
                 except Exception:
-                    logging.error('Error processing %r\n%s.' \
-                            % (uid, traceback.format_exc()))
+                    logging.error('Error processing (%r,%r)\n%s.' \
+                            % (uid, vid, traceback.format_exc()))
 
-        if not uids:
+        if not uvids:
             logging.debug('Finished updating index.')
             layoutmanager.get_instance().index_updated = True
             return False
         else:
             return True
 
-    def _create_completion_cb(self, async_cb, async_err_cb, uid, exc=None):
-        logger.debug("_create_completion_cb(%r, %r, %r, %r)" % \
-            (async_cb, async_err_cb, uid, exc))
+    @trace
+    def _create_completion_cb(self, async_cb, async_err_cb, uid, vid, exc=None):
         if exc is not None:
             async_err_cb(exc)
             return
 
-        self.Created(uid)
-        self._optimizer.optimize(uid)
-        logger.debug("created %s" % uid)
-        async_cb(uid)
+        self.Created(uid, vid)
+        self._optimizer.optimize(uid, vid)
+        logger.debug("created (%s,%s)" % (uid,vid))
+        async_cb(uid,vid)
 
     @dbus.service.method(DS_DBUS_INTERFACE,
                          in_signature='a{sv}sb',
-                         out_signature='s',
+                         out_signature='ss',
                          async_callbacks=('async_cb', 'async_err_cb'),
                          byte_arrays=True)
     def create(self, props, file_path, transfer_ownership,
                async_cb, async_err_cb):
         uid = str(uuid.uuid4())
-        logging.debug('datastore.create %r' % uid)
+        vid = str(uuid.uuid4()) # use fake for now
+        logging.debug('datastore.create %r %r' % (uid, vid))
 
         if not props.get('timestamp', ''):
             props['timestamp'] = int(time.time())
 
-        self._metadata_store.store(uid, props)
-        self._index_store.store(uid, props)
-        self._file_store.store(uid, file_path, transfer_ownership,
+        self._metadata_store.store(uid, vid, props)
+        self._index_store.store(uid, vid, props)
+        self._file_store.store(uid, vid, file_path, transfer_ownership,
                 lambda *args: self._create_completion_cb(async_cb,
                                                          async_err_cb,
                                                          uid,
+                                                         vid,
                                                          *args))
+        return (uid, vid)
 
-    @dbus.service.signal(DS_DBUS_INTERFACE, signature="s")
-    def Created(self, uid):
+    @dbus.service.signal(DS_DBUS_INTERFACE, signature="ss")
+    def Created(self, uid, vid):
         pass
 
-    def _update_completion_cb(self, async_cb, async_err_cb, uid, exc=None):
-        logger.debug("_update_completion_cb() called with %r / %r, exc %r" % \
-            (async_cb, async_err_cb, exc))
+    @trace
+    def _update_completion_cb(self, async_cb, async_err_cb, uid, vid, exc=None):
         if exc is not None:
             async_err_cb(exc)
             return
 
-        self.Updated(uid)
-        self._optimizer.optimize(uid)
-        logger.debug("updated %s" % uid)
-        async_cb()
+        self.Updated(uid,vid)
+        self._optimizer.optimize(uid,vid)
+        logger.debug("updated %s %s" % (uid, vid))
+        async_cb(uid, vid)
 
     @dbus.service.method(DS_DBUS_INTERFACE,
-             in_signature='sa{sv}sb',
-             out_signature='',
+             in_signature='ssa{sv}sb',
+             out_signature='ss',
              async_callbacks=('async_cb', 'async_err_cb'),
              byte_arrays=True)
-    def update(self, uid, props, file_path, transfer_ownership,
+    @trace
+    def update(self, uid, vid, props, file_path, transfer_ownership,
                async_cb, async_err_cb):
-        logging.debug('datastore.update %r' % uid)
 
         if not props.get('timestamp', ''):
             props['timestamp'] = int(time.time())
 
-        self._metadata_store.store(uid, props)
-        self._index_store.store(uid, props)
+        # TODO: create branch if required (inside some abstraction layer)
+        if file_path :
+            # only for data updates
+            vid = str(uuid.uuid4()) # use fake for now
 
-        if os.path.exists(self._file_store.get_file_path(uid)) and \
-                (not file_path or os.path.exists(file_path)):
-            self._optimizer.remove(uid)
-        self._file_store.store(uid, file_path, transfer_ownership,
+        self._metadata_store.store(uid, vid, props)
+        self._index_store.store(uid, vid, props)
+
+#        if os.path.exists(self._file_store.get_file_path(uid, vid)) and \
+#                (not file_path or os.path.exists(file_path)):
+#            self._optimizer.remove(uid, vid)
+        self._file_store.store(uid, vid, file_path, transfer_ownership,
                 lambda *args: self._update_completion_cb(async_cb,
                                                          async_err_cb,
                                                          uid,
+                                                         vid,
                                                          *args))
+        return (uid, vid)
 
-    @dbus.service.signal(DS_DBUS_INTERFACE, signature="s")
-    def Updated(self, uid):
+    @dbus.service.signal(DS_DBUS_INTERFACE, signature="ss")
+    def Updated(self, uid, vid):
         pass
 
     @dbus.service.method(DS_DBUS_INTERFACE,
              in_signature='a{sv}as',
              out_signature='aa{sv}u')
+    @trace
     def find(self, query, properties):
-        logging.debug('datastore.find %r' % query)
-        t = time.time()
-
+        uvids = None
         if layoutmanager.get_instance().index_updated:
             try:
-                uids, count = self._index_store.find(query)
+                uvids, count = self._index_store.find(query)
             except Exception:
                 logging.error('Failed to query index, will rebuild\n%s' \
                         % traceback.format_exc())
@@ -209,13 +218,13 @@ class DataStore(dbus.service.Object):
                 self._index_store.open_index()
                 self._rebuild_index()
 
-        if not layoutmanager.get_instance().index_updated:
+        if uvids is None :
             logging.warning('Index updating, returning all entries')
             return self._find_all(query, properties)
 
         entries = []
-        for uid in uids:
-            entry_path = layoutmanager.get_instance().get_entry_path(uid)
+        for (uid, vid) in uvids:
+            entry_path = layoutmanager.get_instance().get_entry_path(uvid)
             if not os.path.exists(entry_path):
                 logging.warning(
                     'Inconsistency detected, returning all entries')
@@ -228,7 +237,7 @@ class DataStore(dbus.service.Object):
 
                 return self._find_all(query, properties)
 
-            metadata = self._metadata_store.retrieve(uid, properties)
+            metadata = self._metadata_store.retrieve(uid, vid, properties)
             entries.append(metadata)
 
         logger.debug('find(): %r' % (time.time() - t))
@@ -236,42 +245,50 @@ class DataStore(dbus.service.Object):
         return entries, count
 
     def _find_all(self, query, properties):
-        uids = layoutmanager.get_instance().find_all()
-        count = len(uids)
+        uvids = layoutmanager.get_instance().find_all()
+        if not query.get('all_versions', False) :
+            # only return latest version for each entry
+            uids_vtime = {}
+            for (uid, vid) in uvids :
+                uids_vtime.setdefault(uid, []).append((vid, self._metadata_store.retrieve(uid, vid, 'timestamp')))
 
+            uvids = [(uid, sorted(candidates, key=lambda e: e[1], reverse=True)[0][0])
+                     for (uid, candidates) in uids_vtime.items()]
+
+        count = len(uvids)
         offset = query.get('offset', 0)
         limit = query.get('limit', MAX_QUERY_LIMIT)
         uids = uids[offset:offset + limit]
 
         entries = []
-        for uid in uids:
-            metadata = self._metadata_store.retrieve(uid, properties)
+        for (uid, vid) in uvids:
+            metadata = self._metadata_store.retrieve(uid, vid, properties)
             entries.append(metadata)
 
         return entries, count
 
     @dbus.service.method(DS_DBUS_INTERFACE,
-             in_signature='s',
+             in_signature='ss',
              out_signature='s',
              sender_keyword='sender')
-    def get_filename(self, uid, sender=None):
-        logging.debug('datastore.get_filename %r' % uid)
+    @trace
+    def get_filename(self, uid, vid, sender=None):
         user_id = dbus.Bus().get_unix_user(sender)
-        extension = self._get_extension(uid)
-        return self._file_store.retrieve(uid, user_id, extension)
+        extension = self._get_extension(uid,vid)
+        return self._file_store.retrieve(uid, vid, user_id, extension)
 
-    def _get_extension(self, uid):
-        mime_type = self._metadata_store.get_property(uid, 'mime_type')
+    def _get_extension(self, uid, vid):
+        mime_type = self._metadata_store.get_property(uid, vid, 'mime_type')
         if mime_type is None or not mime_type:
             return ''
         return mime.get_primary_extension(mime_type)
 
     @dbus.service.method(DS_DBUS_INTERFACE,
-                         in_signature='s',
+                         in_signature='ss',
                          out_signature='a{sv}')
-    def get_properties(self, uid):
-        logging.debug('datastore.get_properties %r' % uid)
-        metadata = self._metadata_store.retrieve(uid)
+    @trace
+    def get_properties(self, uid, vid):
+        metadata = self._metadata_store.retrieve(uid,vid)
         return metadata
 
     @dbus.service.method(DS_DBUS_INTERFACE,
@@ -289,23 +306,24 @@ class DataStore(dbus.service.Object):
             return []
 
     @dbus.service.method(DS_DBUS_INTERFACE,
-             in_signature='s',
+             in_signature='ss',
              out_signature='')
-    def delete(self, uid):
-        self._optimizer.remove(uid)
+    def delete(self, uid, vid):
+        # TODO: vid=None/'' => remove all versions
+        self._optimizer.remove(uid, vid)
 
-        self._index_store.delete(uid)
-        self._file_store.delete(uid)
-        self._metadata_store.delete(uid)
+        self._index_store.delete(uid, vid)
+        self._file_store.delete(uid, vid)
+        self._metadata_store.delete(uid, vid)
 
-        entry_path = layoutmanager.get_instance().get_entry_path(uid)
+        entry_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         os.removedirs(entry_path)
 
-        self.Deleted(uid)
-        logger.debug("deleted %s" % uid)
+        self.Deleted(uid, vid)
+        logger.debug("deleted (%r,%r)" % (uid,vid))
 
-    @dbus.service.signal(DS_DBUS_INTERFACE, signature="s")
-    def Deleted(self, uid):
+    @dbus.service.signal(DS_DBUS_INTERFACE, signature="ss")
+    def Deleted(self, uid, vid):
         pass
 
     def stop(self):
@@ -316,29 +334,3 @@ class DataStore(dbus.service.Object):
     @dbus.service.signal(DS_DBUS_INTERFACE)
     def Stopped(self):
         pass
-
-    @dbus.service.method(DS_DBUS_INTERFACE,
-                         in_signature="sa{sv}",
-                         out_signature='s')
-    def mount(self, uri, options=None):
-        return ''
-
-    @dbus.service.method(DS_DBUS_INTERFACE,
-                         in_signature="",
-                         out_signature="aa{sv}")
-    def mounts(self):
-        return [{'id': 1}]
-
-    @dbus.service.method(DS_DBUS_INTERFACE,
-                         in_signature="s",
-                         out_signature="")
-    def unmount(self, mountpoint_id):
-        pass
-
-    @dbus.service.signal(DS_DBUS_INTERFACE, signature="a{sv}")
-    def Mounted(self, descriptior):
-        pass
-
-    @dbus.service.signal(DS_DBUS_INTERFACE, signature="a{sv}")
-    def Unmounted(self, descriptor):
-        pass
diff --git a/src/carquinyol/filestore.py b/src/carquinyol/filestore.py
index b96c323..bf77e5b 100644
--- a/src/carquinyol/filestore.py
+++ b/src/carquinyol/filestore.py
@@ -31,11 +31,11 @@ class FileStore(object):
     # TODO: add protection against store and retrieve operations on entries
     # that are being processed async.
 
-    def store(self, uid, file_path, transfer_ownership, completion_cb):
+    def store(self, uid, vid, file_path, transfer_ownership, completion_cb):
         """Store a file for a given entry.
 
         """
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         if not os.path.exists(dir_path):
             os.makedirs(dir_path)
 
@@ -83,10 +83,10 @@ class FileStore(object):
            deleting this file.
 
         """
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         file_path = os.path.join(dir_path, 'data')
         if not os.path.exists(file_path):
-            logging.debug('Entry %r doesnt have any file' % uid)
+            logging.debug('Entry (%r,%r) doesnt have any file' % (uid,vid))
             return ''
 
         use_instance_dir = os.path.exists('/etc/olpc-security') and \
@@ -108,19 +108,19 @@ class FileStore(object):
         elif extension:
             extension = '.' + extension
 
-        destination_path = os.path.join(destination_dir, uid + extension)
+        destination_path = os.path.join(destination_dir, "%s-%s%s" % (uid, vid, extension))
 
         attempt = 1
         while os.path.exists(destination_path):
             if attempt > 10:
-                fd_, destination_path = tempfile.mkstemp(prefix=uid,
+                fd_, destination_path = tempfile.mkstemp(prefix="%s-%s" % (uid,vid),
                                                          suffix=extension,
                                                          dir=destination_dir)
                 del fd_
                 os.unlink(destination_path)
                 break
             else:
-                file_name = '%s_%s%s' % (uid, attempt, extension)
+                file_name = '%s-%s_%s%s' % (uid, vid, attempt, extension)
                 destination_path = os.path.join(destination_dir, file_name)
                 attempt += 1
 
@@ -144,25 +144,25 @@ class FileStore(object):
 
         return destination_path
 
-    def get_file_path(self, uid):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+    def get_file_path(self, uid, vid):
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         return os.path.join(dir_path, 'data')
 
-    def delete(self, uid):
+    def delete(self, uid, vid):
         """Remove the file associated to a given entry.
 
         """
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         file_path = os.path.join(dir_path, 'data')
         if os.path.exists(file_path):
             os.remove(file_path)
 
-    def hard_link_entry(self, new_uid, existing_uid):
+    def hard_link_entry(self, new_uid, new_vid, existing_uid, existing_vid):
         existing_file = os.path.join(
-                layoutmanager.get_instance().get_entry_path(existing_uid),
+                layoutmanager.get_instance().get_entry_path(existing_uid, existing_vid),
                 'data')
         new_file = os.path.join(
-                layoutmanager.get_instance().get_entry_path(new_uid),
+                layoutmanager.get_instance().get_entry_path(new_uid, new_vid),
                 'data')
 
         logging.debug('removing %r' % new_file)
diff --git a/src/carquinyol/indexstore.py b/src/carquinyol/indexstore.py
index 42c3132..617ebd4 100644
--- a/src/carquinyol/indexstore.py
+++ b/src/carquinyol/indexstore.py
@@ -27,8 +27,10 @@ from carquinyol.layoutmanager import MAX_QUERY_LIMIT
 _VALUE_UID = 0
 _VALUE_TIMESTAMP = 1
 _VALUE_TITLE = 2
+_VALUE_VID = 3
 
 _PREFIX_UID = 'Q'
+_PREFIX_VID = 'V'
 _PREFIX_ACTIVITY = 'A'
 _PREFIX_ACTIVITY_ID = 'I'
 _PREFIX_MIME_TYPE = 'M'
@@ -69,17 +71,19 @@ class IndexStore(object):
         for f in os.listdir(index_path):
             os.remove(os.path.join(index_path, f))
 
-    def contains(self, uid):
-        postings = self._database.postlist(_PREFIX_UID + uid)
+    def contains(self, uid, vid):
+        postings = self._database.postlist(_PREFIX_UID + uid + _PREFIX_VID + vid)
         try:
             postlist_item = postings.next()
         except StopIteration:
             return False
         return True
 
-    def store(self, uid, properties):
+    def store(self, uid, vid, properties):
         document = Document()
+        document.add_term("%s%s%s%s" % (_PREFIX_UID, uid, _PREFIX_VID, vid))
         document.add_term(_PREFIX_UID + uid)
+        document.add_term(_PREFIX_VID + vid)
         document.add_term(_PREFIX_ACTIVITY + properties.get('activity', ''))
         document.add_term(_PREFIX_MIME_TYPE + properties.get('mime_type', ''))
         document.add_term(_PREFIX_ACTIVITY_ID +
@@ -87,6 +91,7 @@ class IndexStore(object):
         document.add_term(_PREFIX_KEEP + str(properties.get('keep', 0)))
 
         document.add_value(_VALUE_UID, uid)
+        document.add_value(_VALUE_VID, vid)
         document.add_value(_VALUE_TIMESTAMP, str(properties['timestamp']))
         document.add_value(_VALUE_TITLE, properties.get('title', '').strip())
 
@@ -107,10 +112,10 @@ class IndexStore(object):
         term_generator.index_text_without_positions(
                 self._extract_text(properties), 1, '')
 
-        if not self.contains(uid):
+        if not self.contains(uid, vid):
             self._database.add_document(document)
         else:
-            self._database.replace_document(_PREFIX_UID + uid, document)
+            self._database.replace_document("%s%s%s%s" % (_PREFIX_UID, uid, _PREFIX_VID, vid), document)
         self._flush()
 
     def _extract_text(self, properties):
@@ -129,6 +134,7 @@ class IndexStore(object):
     def find(self, query):
         offset = query.pop('offset', 0)
         limit = query.pop('limit', MAX_QUERY_LIMIT)
+        all_versions = query.pop('all_versions', False)
         order_by = query.pop('order_by', [])
 
         enquire = Enquire(self._database)
@@ -156,11 +162,25 @@ class IndexStore(object):
         query_result = enquire.get_mset(offset, limit, check_at_least)
         total_count = query_result.get_matches_estimated()
 
-        uids = []
+        uvids = []
+        timestamps = []
         for hit in query_result:
-            uids.append(hit.document.get_value(_VALUE_UID))
+            uvids.append((hit.document.get_value(_VALUE_UID), hit.document.get_value(_VALUE_VID)))
 
-        return (uids, total_count)
+        if not all_versions :
+            # only return latest version for each entry
+            # result set is already sorted by time so we only need to take the first entry for each uid
+            uids_vid = {}
+            uvids_new = []
+            for (uid, vid) in uvids :
+                if uid not in uids_vid :
+                    uids_vid[uid] = vid
+                    uvids_new.append((uid,vid))
+
+            uvids = uvids_new
+
+        # TODO: total_count will be totally off if all_versions is not set
+        return (uvids, total_count)
 
     def _parse_query(self, query_dict):
         logging.debug('_parse_query %r' % query_dict)
@@ -193,10 +213,15 @@ class IndexStore(object):
             query = Query(Query.OP_VALUE_RANGE, _VALUE_TIMESTAMP, start, end)
             queries.append(query)
 
+        # TODO: refactor / simplify
         uid = query_dict.pop('uid', None)
         if uid is not None:
             queries.append(Query(_PREFIX_UID + uid))
 
+        vid = query_dict.pop('vid', None)
+        if vid is not None:
+            queries.append(Query(_PREFIX_VID + vid))
+
         activity = query_dict.pop('activity', None)
         if activity is not None:
             queries.append(Query(_PREFIX_ACTIVITY + activity))
@@ -226,8 +251,8 @@ class IndexStore(object):
 
         return Query(Query.OP_AND, queries)
 
-    def delete(self, uid):
-        self._database.delete_document(_PREFIX_UID + uid)
+    def delete(self, uid, vid):
+        self._database.delete_document("%s%s%s%s" % (_PREFIX_UID, uid, _PREFIX_VID, vid))
 
     def get_activities(self):
         activities = []
diff --git a/src/carquinyol/layoutmanager.py b/src/carquinyol/layoutmanager.py
index 42db46f..f14c9e6 100644
--- a/src/carquinyol/layoutmanager.py
+++ b/src/carquinyol/layoutmanager.py
@@ -61,9 +61,9 @@ class LayoutManager(object):
         version_path = os.path.join(self._root_path, 'version')
         open(version_path, 'w').write(str(version))
 
-    def get_entry_path(self, uid):
+    def get_entry_path(self, uid, vid):
         # os.path.join() is just too slow
-        return '%s/%s/%s' % (self._root_path, uid[:2], uid)
+        return '%s/%s/%s-%s' % (self._root_path, uid[:2], uid, vid)
 
     def get_root_path(self):
         return self._root_path
@@ -93,13 +93,13 @@ class LayoutManager(object):
     index_updated = property(_is_index_updated, _set_index_updated)
 
     def find_all(self):
-        uids = []
+        uvids = []
         for f in os.listdir(self._root_path):
             if os.path.isdir(os.path.join(self._root_path, f)) and len(f) == 2:
                 for g in os.listdir(os.path.join(self._root_path, f)):
-                    if len(g) == 36:
-                        uids.append(g)
-        return uids
+                    if len(g) == 73:
+                        uvids.append((g[:36], g[37:]))
+        return uvids
 
     def _is_empty(self):
         for f in os.listdir(self._root_path):
diff --git a/src/carquinyol/metadatastore.py b/src/carquinyol/metadatastore.py
index 8461ef7..ea0b389 100644
--- a/src/carquinyol/metadatastore.py
+++ b/src/carquinyol/metadatastore.py
@@ -7,9 +7,8 @@ MAX_SIZE = 256
 
 
 class MetadataStore(object):
-
-    def store(self, uid, metadata):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+    def store(self, uid, vid, metadata):
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         if not os.path.exists(dir_path):
             os.makedirs(dir_path)
 
@@ -21,6 +20,7 @@ class MetadataStore(object):
                 os.remove(os.path.join(metadata_path, key))
 
         metadata['uid'] = uid
+        metadata['vid'] = vid
         for key, value in metadata.items():
 
             # Hack to support activities that still pass properties named as
@@ -38,19 +38,19 @@ class MetadataStore(object):
             finally:
                 f.close()
 
-    def retrieve(self, uid, properties=None):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+    def retrieve(self, uid, vid, properties=None):
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         return metadatareader.retrieve(dir_path, properties)
 
-    def delete(self, uid):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+    def delete(self, uid, vid):
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         metadata_path = os.path.join(dir_path, 'metadata')
         for key in os.listdir(metadata_path):
             os.remove(os.path.join(metadata_path, key))
         os.rmdir(metadata_path)
 
-    def get_property(self, uid, key):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+    def get_property(self, uid, vid, key):
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         metadata_path = os.path.join(dir_path, 'metadata')
         property_path = os.path.join(metadata_path, key)
         if os.path.exists(property_path):
@@ -58,8 +58,8 @@ class MetadataStore(object):
         else:
             return None
 
-    def set_property(self, uid, key, value):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+    def set_property(self, uid, vid, key, value):
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         metadata_path = os.path.join(dir_path, 'metadata')
         property_path = os.path.join(metadata_path, key)
         open(property_path, 'w').write(value)
diff --git a/src/carquinyol/migration.py b/src/carquinyol/migration.py
index 02f8e68..8ff63b3 100644
--- a/src/carquinyol/migration.py
+++ b/src/carquinyol/migration.py
@@ -22,6 +22,7 @@ import logging
 import shutil
 import time
 import traceback
+import uuid
 
 import cjson
 
@@ -31,7 +32,7 @@ DATE_FORMAT = '%Y-%m-%dT%H:%M:%S'
 
 
 def migrate_from_0():
-    logging.info('Migrating datastore from version 0 to version 1')
+    logging.info('Migrating datastore from version 0 to version 2')
 
     root_path = layoutmanager.get_instance().get_root_path()
     old_root_path = os.path.join(root_path, 'store')
@@ -44,10 +45,11 @@ def migrate_from_0():
             continue
 
         logging.debug('Migrating entry %r' % uid)
+        vid = str(uuid.uuid4())
         try:
-            _migrate_metadata(root_path, old_root_path, uid)
-            _migrate_file(root_path, old_root_path, uid)
-            _migrate_preview(root_path, old_root_path, uid)
+            _migrate_metadata_0(root_path, old_root_path, uid, vid)
+            _migrate_file_0(root_path, old_root_path, uid, vid)
+            _migrate_preview_0(root_path, old_root_path, uid, vid)
         except Exception:
             logging.error('Error while migrating entry %r: %s\n' % \
                           (uid, traceback.format_exc()))
@@ -59,8 +61,8 @@ def migrate_from_0():
     logging.info('Migration finished')
 
 
-def _migrate_metadata(root_path, old_root_path, uid):
-    dir_path = layoutmanager.get_instance().get_entry_path(uid)
+def _migrate_metadata_0(root_path, old_root_path, uid, vid):
+    dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
     metadata_path = os.path.join(dir_path, 'metadata')
     os.makedirs(metadata_path)
 
@@ -70,6 +72,8 @@ def _migrate_metadata(root_path, old_root_path, uid):
     if 'uid' not in metadata:
         metadata['uid'] = uid
 
+    metadata['vid'] = vid
+
     if 'timestamp' not in metadata and 'mtime' in metadata:
         metadata['timestamp'] = \
                 time.mktime(time.strptime(metadata['mtime'], DATE_FORMAT))
@@ -91,15 +95,62 @@ def _migrate_metadata(root_path, old_root_path, uid):
                     (key, uid, traceback.format_exc()))
 
 
-def _migrate_file(root_path, old_root_path, uid):
+def _migrate_file_0(root_path, old_root_path, uid, vid):
     if os.path.exists(os.path.join(old_root_path, uid)):
-        dir_path = layoutmanager.get_instance().get_entry_path(uid)
+        dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
         os.rename(os.path.join(old_root_path, uid),
                   os.path.join(dir_path, 'data'))
 
 
-def _migrate_preview(root_path, old_root_path, uid):
-    dir_path = layoutmanager.get_instance().get_entry_path(uid)
+def _migrate_preview_0(root_path, old_root_path, uid, vid):
+    dir_path = layoutmanager.get_instance().get_entry_path(uid, vid)
     metadata_path = os.path.join(dir_path, 'metadata')
     os.rename(os.path.join(old_root_path, 'preview', uid),
               os.path.join(metadata_path, 'preview'))
+
+
+def migrate_from_1():
+    logging.info('Migrating datastore from version 1 to version 2')
+
+    root_path = layoutmanager.get_instance().get_root_path()
+    checksum_path = os.path.join(root_path, "checksums")
+
+    vids = {}
+    for hash02 in os.listdir(root_path):
+        if len(hash02) != 2 :
+            continue
+
+        for uid in os.listdir(os.path.join(root_path, hash02)) :
+            if (len(uid) != 36) :
+                continue
+
+            logging.debug('Migrating entry %r' % uid)
+
+            vid = str(uuid.uuid4())
+            vids[uid] = vid
+            try:
+                new_path = layoutmanager.get_instance().get_entry_path(uid, vid)
+                os.rename(os.path.join(root_path, hash02, uid),
+                          new_path)
+                file(os.path.join(new_path, "metadata", "vid"), "w").write(vid)
+
+            except Exception:
+                logging.error('Error while migrating entry %r: %s\n' % \
+                              (uid, traceback.format_exc()))
+
+    for checksum in os.listdir(checksum_path) :
+        entries_path = os.path.join(checksum_path, checksum)
+        for uid in os.listdir(entries_path) :
+            if len(uid) != 36 :
+                continue
+
+            try :
+                os.rename(os.path.join(entries_path, uid),
+                          os.path.join(entries_path, "%s-%s" % (uid,vids[uid])))
+
+            except Exception:
+                logging.error('Error while migrating checksum entry %r / %r: %s\n' % \
+                              (checksum, uid, traceback.format_exc()))
+
+    logging.info('Migration finished')
+
diff --git a/src/carquinyol/optimizer.py b/src/carquinyol/optimizer.py
index 6cb1374..361afef 100644
--- a/src/carquinyol/optimizer.py
+++ b/src/carquinyol/optimizer.py
@@ -18,6 +18,7 @@ import os
 import errno
 import logging
 import subprocess
+import uuid
 
 import gobject
 
@@ -33,33 +34,34 @@ class Optimizer(object):
         self._metadata_store = metadata_store
         self._enqueue_checksum_id = None
 
-    def optimize(self, uid):
+    def optimize(self, uid, vid):
         """Add an entry to a queue of entries to be checked for duplicates.
 
         """
-        if not os.path.exists(self._file_store.get_file_path(uid)):
+        if not os.path.exists(self._file_store.get_file_path(uid, vid)):
             return
 
         queue_path = layoutmanager.get_instance().get_queue_path()
-        open(os.path.join(queue_path, uid), 'w').close()
-        logging.debug('optimize %r' % os.path.join(queue_path, uid))
+        fname = os.path.join(queue_path, "%s-%s" % (uid, vid))
+        open(fname, 'w').close()
+        logging.debug('optimize %r' % fname)
 
         if self._enqueue_checksum_id is None:
             self._enqueue_checksum_id = \
                     gobject.idle_add(self._process_entry_cb,
                                      priority=gobject.PRIORITY_LOW)
 
-    def remove(self, uid):
+    def remove(self, uid, vid):
         """Remove any structures left from space optimization
 
         """
-        checksum = self._metadata_store.get_property(uid, 'checksum')
+        checksum = self._metadata_store.get_property(uid, vid, 'checksum')
         if checksum is None:
             return
 
         checksums_dir = layoutmanager.get_instance().get_checksums_dir()
         checksum_path = os.path.join(checksums_dir, checksum)
-        checksum_entry_path = os.path.join(checksum_path, uid)
+        checksum_entry_path = os.path.join(checksum_path, "%s-%s" % (uid,vid))
 
         if os.path.exists(checksum_entry_path):
             logging.debug('remove %r' % checksum_entry_path)
@@ -81,14 +83,14 @@ class Optimizer(object):
         checksum_path = os.path.join(checksums_dir, checksum)
         return os.path.exists(checksum_path)
 
-    def _get_uid_from_checksum(self, checksum):
+    def _get_uvid_from_checksum(self, checksum):
         """Get an existing entry which file matches checksum.
 
         """
         checksums_dir = layoutmanager.get_instance().get_checksums_dir()
         checksum_path = os.path.join(checksums_dir, checksum)
-        first_uid = os.listdir(checksum_path)[0]
-        return first_uid
+        first_uvid = os.listdir(checksum_path)[0]
+        return (first_uvid[:36], first_uvid[37:])
 
     def _create_checksum_dir(self, checksum):
         """Create directory that tracks files with this same checksum.
@@ -99,24 +101,25 @@ class Optimizer(object):
         logging.debug('create dir %r' % checksum_path)
         os.mkdir(checksum_path)
 
-    def _add_checksum_entry(self, uid, checksum):
-        """Create a file in the checksum dir with the uid of the entry
+    def _add_checksum_entry(self, uid, vid, checksum):
+        """Create a file in the checksum dir with the uid and vid of the entry
 
         """
         checksums_dir = layoutmanager.get_instance().get_checksums_dir()
         checksum_path = os.path.join(checksums_dir, checksum)
 
-        logging.debug('touch %r' % os.path.join(checksum_path, uid))
-        open(os.path.join(checksum_path, uid), 'w').close()
+        fname = os.path.join(checksum_path, "%s-%s" % (uid,vid))
+        logging.debug('touch %r' % fname)
+        open(fname, 'w').close()
 
-    def _already_linked(self, uid, checksum):
+    def _already_linked(self, uid, vid, checksum):
         """Check if this entry's file is already a hard link to the checksums
            dir.
 
         """
         checksums_dir = layoutmanager.get_instance().get_checksums_dir()
         checksum_path = os.path.join(checksums_dir, checksum)
-        return os.path.exists(os.path.join(checksum_path, uid))
+        return os.path.exists(os.path.join(checksum_path, "%s-%s" % (uid,vid)))
 
     def _process_entry_cb(self):
         """Process one item in the checksums queue by calculating its checksum,
@@ -127,30 +130,30 @@ class Optimizer(object):
         queue_path = layoutmanager.get_instance().get_queue_path()
         queue = os.listdir(queue_path)
         if queue:
-            uid = queue[0]
-            logging.debug('_process_entry_cb processing %r' % uid)
+            (uid,vid) = queue[0][:36], queue[0][37:]
+            logging.debug('_process_entry_cb processing (%r,%r)' % (uid,vid))
 
-            file_in_entry_path = self._file_store.get_file_path(uid)
+            file_in_entry_path = self._file_store.get_file_path(uid,vid)
             if not os.path.exists(file_in_entry_path):
-                logging.info('non-existent entry in queue: %r' % uid)
+                logging.info('non-existent entry in queue: (%r,%r)' % (uid,vid))
             else:
                 checksum = self._calculate_md5sum(file_in_entry_path)
-                self._metadata_store.set_property(uid, 'checksum', checksum)
+                self._metadata_store.set_property(uid, vid, 'checksum', checksum)
 
                 if self._identical_file_already_exists(checksum):
-                    if not self._already_linked(uid, checksum):
-                        existing_entry_uid = \
-                                self._get_uid_from_checksum(checksum)
+                    if not self._already_linked(uid, vid, checksum):
+                        existing_entry_uvid = \
+                                self._get_uvid_from_checksum(checksum)
 
-                        self._file_store.hard_link_entry(uid,
-                                                         existing_entry_uid)
+                        self._file_store.hard_link_entry(uid, vid,
+                                                         *existing_entry_uvid)
 
-                        self._add_checksum_entry(uid, checksum)
+                        self._add_checksum_entry(uid, vid, checksum)
                 else:
                     self._create_checksum_dir(checksum)
-                    self._add_checksum_entry(uid, checksum)
+                    self._add_checksum_entry(uid, vid, checksum)
 
-            os.remove(os.path.join(queue_path, uid))
+            os.remove(os.path.join(queue_path, "%s-%s" % (uid,vid)))
 
         if len(queue) <= 1:
             self._enqueue_checksum_id = None