phases: avoid N² behavior in `advanceboundary`
We allowed duplicated entries in the deque, which each entry could potentially
insert all its ancestors. So advancing boundary for the full repository would
mean each revision would walk all its ancestors, resulting in O(N²) iteration.
For repository of any decent size, N² is quickly insane.
We introduce a simple set to avoid this and get back to reasonable performance.
--- a/mercurial/phases.py Thu Mar 14 16:25:46 2024 +0100
+++ b/mercurial/phases.py Fri Mar 15 01:31:57 2024 +0100
@@ -703,6 +703,7 @@
return set()
# search for affected high phase changesets and roots
+ seen = set(new_revs)
push = heapq.heappush
pop = heapq.heappop
parents = cl.parentrevs
@@ -735,9 +736,11 @@
# higher phases
delroots.add(current)
# schedule a walk down if needed
- if p1_phase > targetphase:
+ if p1_phase > targetphase and p1 not in seen:
+ seen.add(p1)
push(revs, -p1)
- if p2_phase > targetphase:
+ if p2_phase > targetphase and p2 not in seen:
+ seen.add(p2)
push(revs, -p2)
if p1_phase < targetphase and p2_phase < targetphase:
new_target_roots.add(current)