diff mercurial/phases.py @ 51421:23950e39281f

phases: large rework of advance boundary

In a similar spirit as the rework of retractboundary, the new algorithm is doing
an amount of work in the order of magnitude of the amount of changeset that
changes phases. (except to find new roots in impacted higher phases if any may
exists).

This result in a very significant speedup for repository with many old draft
like mozilla try.

runtime of perf:unbundle for a bundle constaining a single changeset (C code):

before 6.7 phase work: 14.497 seconds
before this change:     6.311 seconds (-55%)
with this change:       2.240 seconds (-85%)

Combined with the other patches that fixes the phases computation in the Rust
index, the rust code with a persistent nodemap get back to quite interresting
performances with 2.026 seconds for the same operation, about 10% faster than
the C code.

--- a/mercurial/phases.py	Thu Feb 22 19:21:14 2024 +0100
+++ b/mercurial/phases.py	Fri Feb 23 05:25:35 2024 +0100
@@ -101,6 +101,7 @@
 """
 
 
+import heapq
 import struct
 import typing
 import weakref
@@ -685,46 +686,104 @@
         else:
             phasetracking = tr.changes.get(b'phases')
 
-        # filter revision already in the right phase
+        affectable_phases = sorted(
+            p for p in allphases if p > targetphase and self._phaseroots[p]
+        )
+        # filter revision already in the right phases
+        candidates = new_revs
+        new_revs = set()
         self._ensure_phase_sets(repo)
-        for phase, revs in self._phasesets.items():
-            if phase <= targetphase:
-                new_revs -= revs
+        for phase in affectable_phases:
+            found = candidates & self._phasesets[phase]
+            new_revs |= found
+            candidates -= found
+            if not candidates:
+                break
         if not new_revs:
             return set()
 
         # search for affected high phase changesets and roots
-        revs = new_revs
-        changes = set()  # set of revisions to be changed
-        delroots = []  # set of root deleted by this path
-        for phase in (phase for phase in allphases if phase > targetphase):
-            # filter nodes that are not in a compatible phase already
-            revs = [rev for rev in revs if self.phase(repo, rev) >= phase]
-            if not revs:
-                break  # no roots to move anymore
-
-            olds = self._phaseroots[phase]
+        push = heapq.heappush
+        pop = heapq.heappop
+        parents = cl.parentrevs
+        get_phase = self.phase
+        changed = {}  # set of revisions to be changed
+        # set of root deleted by this path
+        delroots = set()
+        new_roots = {p: set() for p in affectable_phases}
+        new_target_roots = set()
+        # revision to walk down
+        revs = [-r for r in new_revs]
+        heapq.heapify(revs)
+        while revs:
+            current = -pop(revs)
+            current_phase = get_phase(repo, current)
+            changed[current] = current_phase
+            p1, p2 = parents(current)
+            if p1 == nullrev:
+                p1_phase = public
+            else:
+                p1_phase = get_phase(repo, p1)
+            if p2 == nullrev:
+                p2_phase = public
+            else:
+                p2_phase = get_phase(repo, p2)
+            # do we have a root ?
+            if current_phase != p1_phase and current_phase != p2_phase:
+                # do not record phase, because we could have "duplicated"
+                # roots, were one root is shadowed by the very same roots of an
+                # higher phases
+                delroots.add(current)
+            # schedule a walk down if needed
+            if p1_phase > targetphase:
+                push(revs, -p1)
+            if p2_phase > targetphase:
+                push(revs, -p2)
+            if p1_phase < targetphase and p2_phase < targetphase:
+                new_target_roots.add(current)
 
-            affected = repo.revs(b'%ld::%ld', olds, revs)
-            changes.update(affected)
-            if dryrun:
-                continue
-            for r in affected:
-                _trackphasechange(
-                    phasetracking, r, self.phase(repo, r), targetphase
-                )
+        # the last iteration was done with the smallest value
+        min_current = current
+        # do we have unwalked children that might be new roots
+        if (min_current + len(changed)) < len(cl):
+            for r in range(min_current, len(cl)):
+                if r in changed:
+                    continue
+                phase = get_phase(repo, r)
+                if phase <= targetphase:
+                    continue
+                p1, p2 = parents(r)
+                if not (p1 in changed or p2 in changed):
+                    continue  # not affected
+                if p1 != nullrev and p1 not in changed:
+                    p1_phase = get_phase(repo, p1)
+                    if p1_phase == phase:
+                        continue  # not a root
+                if p2 != nullrev and p2 not in changed:
+                    p2_phase = get_phase(repo, p2)
+                    if p2_phase == phase:
+                        continue  # not a root
+                new_roots[phase].add(r)
 
-            roots = set(repo.revs(b'roots((%ld::) - %ld)', olds, affected))
-            if olds != roots:
-                self._updateroots(repo, phase, roots, tr)
-                # some roots may need to be declared for lower phases
-                delroots.extend(olds - roots)
+        # apply the changes
         if not dryrun:
-            # declare deleted root in the target phase
-            if targetphase != 0:
-                self._retractboundary(repo, tr, targetphase, revs=delroots)
+            for r, p in changed.items():
+                _trackphasechange(phasetracking, r, p, targetphase)
+            for phase in affectable_phases:
+                roots = self._phaseroots[phase]
+                removed = roots & delroots
+                if removed or new_roots[phase]:
+                    # Be careful to preserve shallow-copied values: do not
+                    # update phaseroots values, replace them.
+                    final_roots = roots - delroots | new_roots[phase]
+                    self._updateroots(repo, phase, final_roots, tr)
+            if new_target_roots:
+                # Thanks for previous filtering, we can't replace existing
+                # roots
+                new_target_roots |= self._phaseroots[targetphase]
+                self._updateroots(repo, targetphase, new_target_roots, tr)
             repo.invalidatevolatilesets()
-        return changes
+        return changed
 
     def retractboundary(self, repo, tr, targetphase, nodes):
         if tr is None: