Rev 3525: Shortcut the case when one revision is in the ancestry of the other. in http://bzr.arbash-meinel.com/branches/bzr/1.6-dev/weave_merge

[John Arbash Meinel]

At http://bzr.arbash-meinel.com/branches/bzr/1.6-dev/weave_merge

------------------------------------------------------------
revno: 3525
revision-id: john at arbash-meinel.com-20080711214124-qi09irlj7pd5cuzg
parent: john at arbash-meinel.com-20080711212836-1ehghrnzgaioqwou
committer: John Arbash Meinel <john at arbash-meinel.com>
branch nick: weave_merge
timestamp: Fri 2008-07-11 16:41:24 -0500
message:
  Shortcut the case when one revision is in the ancestry of the other.
  
  At the cost of a heads() check, when one parent supersedes, we don't have to extract
  the text for the other. Changes merge time from 3m37s => 3m21s. Using a
  CachingParentsProvider would drop the time down to 3m11s.
-------------- next part --------------
=== modified file 'bzrlib/merge.py'
--- a/bzrlib/merge.py	2008-07-11 21:28:36 +0000
+++ b/bzrlib/merge.py	2008-07-11 21:41:24 +0000
@@ -1400,22 +1400,22 @@
         self.a_key = self._key_prefix + (self.a_rev,)
         self.b_key = self._key_prefix + (self.b_rev,)
         self.graph = Graph(self.vf)
-        # heads = self.graph.heads((self.a_key, self.b_key))
-        # if len(heads) == 1:
-        #     # one side dominates, so we can just return its values, yay for
-        #     # per-file graphs
-        #     # Ideally we would know that before we get this far
-        #     self._head_key = heads.pop()
-        #     if self._head_key == self.a_key:
-        #         other = b_rev
-        #     else:
-        #         other = a_rev
-        #     mutter('found dominating revision for %s\n%s > %s', self.vf,
-        #            self._head_key[-1], other)
-        #     self._weave = None
-        # else:
-        self._head_key = None
-        self._build_weave()
+        heads = self.graph.heads((self.a_key, self.b_key))
+        if len(heads) == 1:
+            # one side dominates, so we can just return its values, yay for
+            # per-file graphs
+            # Ideally we would know that before we get this far
+            self._head_key = heads.pop()
+            if self._head_key == self.a_key:
+                other = b_rev
+            else:
+                other = a_rev
+            mutter('found dominating revision for %s\n%s > %s', self.vf,
+                   self._head_key[-1], other)
+            self._weave = None
+        else:
+            self._head_key = None
+            self._build_weave()
 
     def _precache_tip_lines(self):
         # Turn this into a no-op, because we will do this later

=== modified file 'bzrlib/tests/test_merge.py'
--- a/bzrlib/tests/test_merge.py	2008-07-11 21:28:36 +0000
+++ b/bzrlib/tests/test_merge.py	2008-07-11 21:41:24 +0000
@@ -525,12 +525,14 @@
         self.add_version(('root', 'D'),
             [('root', 'A'), ('root', 'B'), ('root', 'C')], 'abcdegh')
         my_plan = _PlanMerge('B', 'D', self.plan_merge_vf, ('root',))
+        # We shortcut when one text supersedes the other in the per-file graph.
+        # We don't actually need to compare the texts at this point.
         self.assertEqual([
-                          ('unchanged', 'a\n'),
-                          ('unchanged', 'b\n'),
-                          ('unchanged', 'c\n'),
-                          ('unchanged', 'd\n'),
-                          ('unchanged', 'e\n'),
+                          ('new-b', 'a\n'),
+                          ('new-b', 'b\n'),
+                          ('new-b', 'c\n'),
+                          ('new-b', 'd\n'),
+                          ('new-b', 'e\n'),
                           ('new-b', 'g\n'),
                           ('new-b', 'h\n')],
                           list(my_plan.plan_merge()))