# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@octobus.net>
# Date 2020-01-15 14:50:14
# Node ID e41a164db7a98a957d5e88f4bd8b0d5a443e1714
# Parent  6614b301ea5887acc30a694344188b0ad826a613

nodemap: track the maximum revision tracked in the nodemap

We need a simple way to detect when the on disk data contains less revision
than the index we read from disk. The docket file is meant for this, we just had
to start tracking that data.

We should also try to detect strip operation, but we will deal with this in
later changesets. Right now we are focusing on defining the API for index
supporting persistent nodemap.

Differential Revision: https://phab.mercurial-scm.org/D7888

diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -2137,6 +2137,7 @@ def debugnodemap(ui, repo, **opts):
         if nm_data is not None:
             docket, data = nm_data
             ui.write((b"uid: %s\n") % docket.uid)
+            ui.write((b"tip-rev: %d\n") % docket.tip_rev)
 
 
 @command(
diff --git a/mercurial/pure/parsers.py b/mercurial/pure/parsers.py
--- a/mercurial/pure/parsers.py
+++ b/mercurial/pure/parsers.py
@@ -170,15 +170,15 @@ class PersistentNodeMapIndexObject(Index
         self._nm_root = self._nm_max_idx = self._nm_rev = None
         return data
 
-    def update_nodemap_data(self, nm_data):
-        """provide full blokc of persisted binary data for a nodemap
+    def update_nodemap_data(self, docket, nm_data):
+        """provide full block of persisted binary data for a nodemap
 
         The data are expected to come from disk. See `nodemap_data_all` for a
         produceur of such data."""
         if nm_data is not None:
             self._nm_root, self._nm_max_idx = nodemaputil.parse_data(nm_data)
             if self._nm_root:
-                self._nm_rev = len(self) - 1
+                self._nm_rev = docket.tip_rev
             else:
                 self._nm_root = self._nm_max_idx = self._nm_rev = None
 
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -639,7 +639,7 @@ class revlog(object):
             if use_nodemap:
                 nodemap_data = nodemaputil.persisted_data(self)
                 if nodemap_data is not None:
-                    index.update_nodemap_data(nodemap_data[1])
+                    index.update_nodemap_data(*nodemap_data)
         except (ValueError, IndexError):
             raise error.RevlogError(
                 _(b"index %s is corrupted") % self.indexfile
diff --git a/mercurial/revlogutils/nodemap.py b/mercurial/revlogutils/nodemap.py
--- a/mercurial/revlogutils/nodemap.py
+++ b/mercurial/revlogutils/nodemap.py
@@ -36,9 +36,11 @@ def persisted_data(revlog):
     if version != ONDISK_VERSION:
         return None
     offset += S_VERSION.size
-    (uid_size,) = S_HEADER.unpack(pdata[offset : offset + S_HEADER.size])
+    headers = S_HEADER.unpack(pdata[offset : offset + S_HEADER.size])
+    uid_size, tip_rev = headers
     offset += S_HEADER.size
     docket = NodeMapDocket(pdata[offset : offset + uid_size])
+    docket.tip_rev = tip_rev
 
     filename = _rawdata_filepath(revlog, docket)
     return docket, revlog.opener.tryread(filename)
@@ -94,6 +96,7 @@ def _persist_nodemap(tr, revlog):
         # store vfs
         with revlog.opener(datafile, b'w') as fd:
             fd.write(data)
+    target_docket.tip_rev = revlog.tiprev()
     # EXP-TODO: if this is a cache, this should use a cache vfs, not a
     # store vfs
     with revlog.opener(revlog.nodemap_file, b'w', atomictemp=True) as fp:
@@ -142,7 +145,7 @@ def _persist_nodemap(tr, revlog):
 ONDISK_VERSION = 0
 
 S_VERSION = struct.Struct(">B")
-S_HEADER = struct.Struct(">B")
+S_HEADER = struct.Struct(">BQ")
 
 ID_SIZE = 8
 
@@ -164,15 +167,19 @@ class NodeMapDocket(object):
         if uid is None:
             uid = _make_uid()
         self.uid = uid
+        self.tip_rev = None
 
     def copy(self):
-        return NodeMapDocket(uid=self.uid)
+        new = NodeMapDocket(uid=self.uid)
+        new.tip_rev = self.tip_rev
+        return new
 
     def serialize(self):
         """return serialized bytes for a docket using the passed uid"""
         data = []
         data.append(S_VERSION.pack(ONDISK_VERSION))
-        data.append(S_HEADER.pack(len(self.uid)))
+        headers = (len(self.uid), self.tip_rev)
+        data.append(S_HEADER.pack(*headers))
         data.append(self.uid)
         return b''.join(data)
 
diff --git a/tests/test-persistent-nodemap.t b/tests/test-persistent-nodemap.t
--- a/tests/test-persistent-nodemap.t
+++ b/tests/test-persistent-nodemap.t
@@ -14,8 +14,9 @@ Test the persistent on-disk nodemap
   $ hg debugbuilddag .+5000
   $ hg debugnodemap --metadata
   uid: ???????????????? (glob)
+  tip-rev: 5000
   $ f --size .hg/store/00changelog.n
-  .hg/store/00changelog.n: size=18
+  .hg/store/00changelog.n: size=26
   $ f --sha256 .hg/store/00changelog-*.nd
   .hg/store/00changelog-????????????????.nd: sha256=b961925120e1c9bc345c199b2cc442abc477029fdece37ef9d99cbe59c0558b7 (glob)
   $ hg debugnodemap --dump-new | f --sha256 --size
@@ -51,8 +52,9 @@ add a new commit
   $ hg ci -m 'foo'
   $ hg debugnodemap --metadata
   uid: ???????????????? (glob)
+  tip-rev: 5001
   $ f --size .hg/store/00changelog.n
-  .hg/store/00changelog.n: size=18
+  .hg/store/00changelog.n: size=26
 
 (The pure code use the debug code that perform incremental update, the C code reencode from scratch)