Rev 2368: Only generate a new set when we need to. Drops 'bzr log NEWS' time from 22s => 8s in http://bzr.arbash-meinel.com/branches/bzr/0.16-dev/log_ancestry

[John Arbash Meinel]

At http://bzr.arbash-meinel.com/branches/bzr/0.16-dev/log_ancestry

------------------------------------------------------------
revno: 2368
revision-id: john at arbash-meinel.com-20070423175330-cwzggk38xbsf4wyy
parent: john at arbash-meinel.com-20070418223921-0h2g7salf1scfd2a
committer: John Arbash Meinel <john at arbash-meinel.com>
branch nick: log_ancestry
timestamp: Mon 2007-04-23 12:53:30 -0500
message:
  Only generate a new set when we need to. Drops 'bzr log NEWS' time from 22s => 8s
modified:
  bzrlib/log.py                  log.py-20050505065812-c40ce11702fe5fb1
-------------- next part --------------
=== modified file 'bzrlib/log.py'
--- a/bzrlib/log.py	2007-04-18 22:39:21 +0000
+++ b/bzrlib/log.py	2007-04-23 17:53:30 +0000
@@ -304,11 +304,17 @@
     sorted_rev_list = topo_sort(rev_graph)
     ancestry = {}
     for rev in sorted_rev_list:
-        rev_ancestry = set()
-        if rev in weave_modifed_revisions:
-            rev_ancestry.add(rev)
-        for parent in rev_graph[rev]:
-            rev_ancestry = rev_ancestry.union(ancestry[parent])
+        parents = rev_graph[rev]
+        if rev not in weave_modifed_revisions and len(parents) == 1:
+            # We will not be adding anything new, so just use a reference to
+            # the parent ancestry.
+            rev_ancestry = ancestry[parents[0]]
+        else:
+            rev_ancestry = set()
+            if rev in weave_modifed_revisions:
+                rev_ancestry.add(rev)
+            for parent in parents:
+                rev_ancestry = rev_ancestry.union(ancestry[parent])
         ancestry[rev] = rev_ancestry
 
     def is_merging_rev(r):