Significantly sped up processing of large numbers of directories passed to a single git-annex command.

Utility/Path.hs

@@ -170,17 +170,19 @@ prop_relPathDirToFile_regressionTest = same_dir_shortcurcuits_at_difference
 				== joinPath ["..", "..", "..", "..", ".git", "annex", "objects", "18", "gk", "SHA256-foo", "SHA256-foo"]
 
 {- Given an original list of paths, and an expanded list derived from it,
- - generates a list of lists, where each sublist corresponds to one of the
+ - partitions the expanded list, so that sublist corresponds to one of the
  - original paths. When the original path is a directory, any items
  - in the expanded list that are contained in that directory will appear in
  - its segment.
+ -
+ - The expanded list must have the same ordering as the original list.
  -}
 segmentPaths :: [FilePath] -> [FilePath] -> [[FilePath]]
 segmentPaths [] new = [new]
 segmentPaths [_] new = [new] -- optimisation
 segmentPaths (l:ls) new = found : segmentPaths ls rest
   where
-	(found, rest)=partition (l `dirContains`) new
+	(found, rest) = break (\p -> not (l `dirContains` p)) new
 
 {- This assumes that it's cheaper to call segmentPaths on the result,
  - than it would be to run the action separately with each path. In

debian/changelog

@@ -22,6 +22,8 @@ git-annex (5.20150328) UNRELEASED; urgency=medium
     corresponding to duplicated files they process.
   * fsck: Added --distributed and --expire options,
     for distributed fsck.
+  * Significantly sped up processing of large numbers of directories
+    passed to a single git-annex command.
 
  -- Joey Hess <id@joeyh.name>  Fri, 27 Mar 2015 16:04:43 -0400
 

doc/bugs/feeding_git_annex_with_xargs_can_fail.mdwn

@@ -9,3 +9,7 @@ Feeding git-annex a long list off directories, eg with xargs can have
   git-ls-files results. There is probably an exponential blowup in the time
   relative to the number of parameters. Some of the stuff being done to
   preserve original ordering etc is likely at fault.
+  
+  > I think I've managed to speed this up something like
+  > 1000x or some such. segmentPaths on an utterly insane list of 6 million
+  > files now runs in about 10 seconds. --[[Joey]]