# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@logilab.fr>
# Date 1357570225 -3600
# Node ID 254b708fd37d2d5e13710e3a5c8cd1fac9c45ab8
# Parent  a2d54f68e13cb68132a161617b8e5386eec49047
performance: speedup computation of mutable revisions

In their current state, revset calls can be very costly, as we test
predicates on the entire repository. The "mutable" filter is used
during branch cache loading operation. We need to make it fast.

This change drops revset calls in favor of direct testing of the
phase of a changeset.

Performance test on my Mercurial checkout
- 19857 total changesets,
- 1646 mutable revision

Before:
  ! mutable
  ! wall 0.032405

After:
  ! mutable
  ! wall 0.001469

Performance test on a Mozilla central checkout:
- 117293 total changesets,
- 1 mutable changeset,

Before:
  ! mutable
  ! wall 0.188636

After:
  ! mutable
  ! wall 0.000022

diff -r a2d54f68e13c -r 254b708fd37d mercurial/repoview.py
--- a/mercurial/repoview.py	Fri Jan 04 20:19:05 2013 +0100
+++ b/mercurial/repoview.py	Mon Jan 07 15:50:25 2013 +0100
@@ -58,7 +58,9 @@
     assert not repo.changelog.filteredrevs
     # fast check to avoid revset call on huge repo
     if util.any(repo._phasecache.phaseroots[1:]):
-        return frozenset(repo.revs('draft() + secret()'))
+        getphase = repo._phasecache.phase
+        maymutable = filteredrevs(repo, 'impactable')
+        return frozenset(r for r in maymutable if getphase(repo, r))
     return frozenset()
 
 def computeimpactable(repo):