From patchwork Sun Mar 13 02:08:49 2016
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Subject: [3, of,
 3] cache: rebuild branch cache from scratch when inconsistencies are
 detected
From: timeless <timeless@gmail.com>
X-Patchwork-Id: 13849
Message-Id: <CAAKMeYg+3-jr-GL0mG1Z2kXxcti3Ccgt8083MED1AFFeXL53Hg@mail.gmail.com>
To: Mads Kiilerich <mads@kiilerich.com>
Cc: mercurial-devel@mercurial-scm.org
Date: Sat, 12 Mar 2016 21:08:49 -0500

Could you please add issue5058
# HG changeset patch
# User Mads Kiilerich <madski@unity3d.com>
# Date 1457831183 -3600
#      Sun Mar 13 02:06:23 2016 +0100
# Node ID 7f85c3393e4594a886b535f0679d1abca37f4604
# Parent  b8a5abd4a18ee070b922d03e5c14d63df504b78a
cache: rebuild branch cache from scratch when inconsistencies are detected

This should recover automatically from some corruptions that for unknown
reasons are seen in the wild.

diff --git a/mercurial/branchmap.py b/mercurial/branchmap.py
--- a/mercurial/branchmap.py
+++ b/mercurial/branchmap.py
@@ -383,6 +383,15 @@ class revbranchcache(object):
         self._rbcnamescount = len(self._names) # number of good names on
disk
         self._namesreverse = dict((b, r) for r, b in
enumerate(self._names))

+    def _clear(self):
+        self._rbcsnameslen = 0
+        del self._names[:]
+        self._rbcnamescount = 0
+        self._namesreverse.clear()
+        self._rbcrevslen = len(self._repo.changelog)
+        self._rbcrevs = array('c')
+        self._rbcrevs.fromstring('\0' * (self._rbcrevslen * _rbcrecsize))
+
     def branchinfo(self, rev):
         """Return branch name and close flag for rev, using and updating
         persistent cache."""
@@ -408,7 +417,11 @@ class revbranchcache(object):
         if cachenode == '\0\0\0\0':
             pass
         elif cachenode == reponode:
-            return self._names[branchidx], close
+            if branchidx < self._rbcnamescount:
+                return self._names[branchidx], close
+            # referenced branch doesn't exist - rebuild is expensive but
needed
+            self._repo.ui.debug("rebuilding corrupted revision branch
cache\n")
+            self._clear()
         else:
             # rev/node map has changed, invalidate the cache from here up
             truncate = rbcrevidx + _rbcrecsize
diff --git a/tests/test-branches.t b/tests/test-branches.t
--- a/tests/test-branches.t
+++ b/tests/test-branches.t
@@ -629,4 +629,25 @@ situation where the cache is out of sync
   $ f --size .hg/cache/rbc-revs*
   .hg/cache/rbc-revs-v1: size=112

+cache is rebuilt when corruption is detected
+  $ echo > .hg/cache/rbc-names-v1
+  $ hg log -r '5:&branch(.)' -T '{rev} ' --debug
+  rebuilding corrupted revision branch cache
+  8 9 10 11 12 13 truncating cache/rbc-revs-v1 to 40
+  $ f --size --hexdump .hg/cache/rbc-*
+  .hg/cache/rbc-names-v1: size=79
+  0000: 62 00 61 00 63 00 61 20 62 72 61 6e 63 68 20 6e |b.a.c.a branch n|
+  0010: 61 6d 65 20 6d 75 63 68 20 6c 6f 6e 67 65 72 20 |ame much longer |
+  0020: 74 68 61 6e 20 74 68 65 20 64 65 66 61 75 6c 74 |than the default|
+  0030: 20 6a 75 73 74 69 66 69 63 61 74 69 6f 6e 20 75 | justification u|
+  0040: 73 65 64 20 62 79 20 62 72 61 6e 63 68 65 73    |sed by branches|
+  .hg/cache/rbc-revs-v1: size=112
+  0000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0020: 00 00 00 00 00 00 00 00 d8 cb c6 1d 00 00 00 01 |................|
+  0030: 58 97 36 a2 00 00 00 02 10 ff 58 95 00 00 00 03 |X.6.......X.....|
+  0040: ee bb 94 44 00 00 00 00 5f 40 61 bb 00 00 00 00 |...D...._@a.....|
+  0050: bf be 84 1b 00 00 00 00 d3 f1 63 45 80 00 00 00 |..........cE....|
+  0060: e3 d4 9c 05 80 00 00 00 e2 3b 55 05 00 00 00 00 |.........;U.....|
+
   $ cd ..