changeset 31218:fc57a8b95f1b

dirstate: avoid unnecessary load+dump during backup Previously, dirstate.savebackup unconditionally dumps the dirstate map to disk. It may require loading dirstate first to be able to dump it. Those operations could be expensive if the dirstate is big, and could be avoided if we know the dirstate file is up-to-date. This patch avoids the read and write if the dirstate is clean. In that case, we just do a plain copy without any serialization. This should make commands which use transactions but do not touch dirstate faster. For example, "hg bookmark -r REV NAME".
author Jun Wu <quark@fb.com>
date Wed, 01 Mar 2017 18:21:06 -0800
parents 1ef37b16b8e8
children dd2364f5180a
files mercurial/dirstate.py
diffstat 1 files changed, 3 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- a/mercurial/dirstate.py	Wed Mar 01 17:59:21 2017 -0800
+++ b/mercurial/dirstate.py	Wed Mar 01 18:21:06 2017 -0800
@@ -1220,8 +1220,9 @@
         # use '_writedirstate' instead of 'write' to write changes certainly,
         # because the latter omits writing out if transaction is running.
         # output file will be used to create backup of dirstate at this point.
-        self._writedirstate(self._opener(filename, "w", atomictemp=True,
-                                         checkambig=True))
+        if self._dirty or not self._opener.exists(filename):
+            self._writedirstate(self._opener(filename, "w", atomictemp=True,
+                                             checkambig=True))
 
         if tr:
             # ensure that subsequent tr.writepending returns True for