* lisp/ido.el (ido-set-matches-1): Improve flex matching performance by

removing backtracking in the regexp (suggested by Stefan).

Fixes: debbugs:12796

2 files changed, 10 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index a07749e4f18..fb436fa0038 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2012-11-10  Leo Liu  <sdl.web@gmail.com>
+
+        * ido.el (ido-set-matches-1): Improve flex matching performance by
+        removing backtracking in the regexp (suggested by Stefan).  (Bug#12796)
+
 2012-11-09  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * emacs-lisp/advice.el (ad-set-advice-info): Set defalias-fset-function.
diff --git a/lisp/ido.el b/lisp/ido.el
index 4ab183b3207..f4f9c27c847 100644
--- a/lisp/ido.el
+++ b/lisp/ido.el
@@ -3764,7 +3764,11 @@ This is to make them appear as if they were \"virtual buffers\"."
                ido-enable-flex-matching
                (> (length ido-text) 1)
                (not ido-enable-regexp))
-      (setq re (mapconcat #'regexp-quote (split-string ido-text "") ".*"))
+      (setq re (concat (regexp-quote (string (aref ido-text 0)))
+                       (mapconcat (lambda (c)
+                                    (concat "[^" (string c) "]*"
+                                            (regexp-quote (string c))))
+                                  (substring ido-text 1) "")))
       (if ido-enable-prefix
           (setq re (concat "\\`" re)))
       (mapc