Add simple index WikiRevisionHistoryByPage.

This will eventually replace WikiRevisionsByPage, which stores
the full contents of each revision in the column value and is
hurting cassandra.

r2/r2/models/wiki.py

@@ -165,7 +165,7 @@ class WikiRevision(tdb_cassandra.UuidThing, Printable):
         self.hidden = not self.is_hidden
         self._commit()
         return self.hidden
-    
+
     @classmethod
     def create(cls, pageid, content, author=None, reason=None):
         kw = dict(pageid=pageid, content=content)
@@ -176,13 +176,15 @@ class WikiRevision(tdb_cassandra.UuidThing, Printable):
         wr = cls(**kw)
         wr._commit()
         WikiRevisionsByPage.add_object(wr)
+        WikiRevisionHistoryByPage.add_object(wr)
         WikiRevisionsRecentBySR.add_object(wr)
         return wr
-    
+
     def _on_commit(self):
         WikiRevisionsByPage.add_object(self)
+        WikiRevisionHistoryByPage.add_object(self)
         WikiRevisionsRecentBySR.add_object(self)
-    
+
     @classmethod
     def get_recent(cls, sr, count=100):
         return WikiRevisionsRecentBySR.query([sr._id36], count=count)
@@ -424,6 +426,23 @@ class WikiPage(tdb_cassandra.Thing):
                 self._id = pageid   
         return tdb_cassandra.Thing._commit(self, *a, **kw)
 
+
+class WikiRevisionHistoryByPage(tdb_cassandra.View):
+    """Create a time ordered index of revisions for a wiki page"""
+    _use_db = True
+    _connection_pool = 'main'
+    _view_of = WikiRevision
+    _compare_with = TIME_UUID_TYPE
+
+    @classmethod
+    def _rowkey(cls, wikirevision):
+        return wikirevision.pageid
+
+    @classmethod
+    def _obj_to_column(cls, wikirevision):
+        return {wikirevision._id: ''}
+
+
 class WikiRevisionsByPage(tdb_cassandra.DenormalizedView):
     """ Associate revisions with pages """