--- a/schema.py	Thu Nov 12 12:15:19 2009 +0100
+++ b/schema.py	Thu Nov 12 13:46:10 2009 +0100
@@ -812,6 +812,7 @@
                 raise Exception('unable to guess selection variables')
             mainvars = ','.join(mainvars)
         RQLExpression.__init__(self, expression, mainvars, eid)
+        # graph of links between variable, used by rql rewriter
         self.vargraph = {}
         for relation in self.rqlst.get_nodes(nodes.Relation):
             try: