# HG changeset patch
# User Martin von Zweigbergk <martinvonz@google.com>
# Date 1416467707 28800
# Node ID a179db3db9b96b38c10c491e6e7e7ad5f40a7787
# Parent  aa0a430d9c75e3fcd0589c1620796857b32d2497
dirstate: speed up repeated missing directory checks

In a mozilla repo with tip at bb3ff09f52fe,

  hg update tip~1000 && time hg revert -nq -r tip .

displays ~4:20 minutes. With tip~100, it runs in ~11 s. With revision
100000, it did not finish in 12 minutes.

Revert calls dirstate.status() with a matcher that matches each file
in the target revision. The main problem [1] lies in
dirstate._walkexplicit(), which looks for matching deleted directories
by checking whether each path is prefix of any path in the
dirstate. With m files in the dirstate and n files in the target
revision that are not in the dirstate, this is clearly O(m*n). Let's
improve by keeping a lazily initialized set of all the directories in
the dirstate, so the time becomes O(m+n).

After this patch, the 4:20 minutes become 5.5 s, while for a single
missing path, it slows down from 1.092 s to 1.150 s (best of 4). The
>12 min case becomes 5.8 s.

 [1] A narrower optimization would be to make revert take the fast
     path for '.' and '--all'.

diff -r aa0a430d9c75 -r a179db3db9b9 mercurial/dirstate.py
--- a/mercurial/dirstate.py	Wed Nov 19 17:07:27 2014 -0800
+++ b/mercurial/dirstate.py	Wed Nov 19 23:15:07 2014 -0800
@@ -629,6 +629,7 @@
         results = dict.fromkeys(subrepos)
         results['.hg'] = None
 
+        alldirs = None
         for ff in files:
             if normalize:
                 nf = normalize(normpath(ff), False, True)
@@ -657,13 +658,12 @@
                 if nf in dmap: # does it exactly match a missing file?
                     results[nf] = None
                 else: # does it match a missing directory?
-                    prefix = nf + "/"
-                    for fn in dmap:
-                        if fn.startswith(prefix):
-                            if matchedir:
-                                matchedir(nf)
-                            notfoundadd(nf)
-                            break
+                    if alldirs is None:
+                        alldirs = scmutil.dirs(dmap)
+                    if nf in alldirs:
+                        if matchedir:
+                            matchedir(nf)
+                        notfoundadd(nf)
                     else:
                         badfn(ff, inst.strerror)