tdb_cassandra: Resurrect View.get_time_sorted_columns.

r2/r2/lib/db/tdb_cassandra.py

@@ -1431,6 +1431,14 @@ class View(ThingBase):
         # TODO: at present this only grabs max_column_count columns
         return self._t
 
+    @classmethod
+    def get_time_sorted_columns(cls, rowkey, limit=None):
+        q = cls._cf.xget(rowkey, include_timestamp=True)
+        r = sorted(q, key=lambda i: i[1][1]) # (col_name, (col_val, timestamp))
+        if limit:
+            r = r[:limit]
+        return OrderedDict([(i[0], i[1][0]) for i in r])
+
     @classmethod
     @will_write
     def _set_values(cls, row_key, col_values,