# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2014-09-18 22:52:45
# Node ID 00c8abe64cf3dba4693db99f1c915f1692d5b95a
# Parent  13e3f07d74a343a352a8adafb37d32087a1d823f

revset: prefetch an attribute in _generatorset.__iter__

Python's attribute lookup are expensible, lets do less of them.

This gives us a 7% speedup on this revset iteration (from 0.063403 to 0.059032)

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2667,12 +2667,13 @@ class _generatorset(object):
         # iteration.
         i = 0
         genlist = self._genlist
-        consume = self._consumegen()
+        nextrev = self._consumegen().next
+        _len = len # cache global lookup
         while True:
-            if i < len(genlist):
+            if i < _len(genlist):
                 yield genlist[i]
             else:
-                yield consume.next()
+                yield nextrev()
             i += 1
 
     def _consumegen(self):