Hi Carsten,

Thanks to the new variable org-agenda-entry-types, I have moved all my
appointments from emacs diary into org-mode. It is now quite fast to
pull up weekly and monthly calendars with a custom agenda command.

The missing piece of the puzzle is integration with "diary" and
"cal-tex" functions via the org-diary sexp. I have found org-diary to be
excruciatingly slow when called for anything more than a couple of days.
I have the following line in my diary file:

&%%(org-diary :timestamp :sexp)

If I try to view 20 or so upcoming days in the diary by typing C-u 20 d
on a date in the calendar, it can take upwards of 30 seconds to generate
the diary display. This is of little consequence, since I can, after
all, simply use the custom agenda command. But I often want to print out
a nice LaTeX calendar of my appointments with cal-tex-cursor-month. And
that takes upwards of 50 seconds (see attached elp-results file).

Judging from the elp-results, the culprit seems to be
org-prepare-agenda-buffers (46 seconds), which is called 31 times (once
for each day). It seems to me that since org-diary is being called 31
times in quick succession by the same function (diary-sexp-entry), one
should only need to call org-prepare-agenda-buffers once.

The only solution I could see to this problem was to add a test to see
if org-diary had been called less than 1 second ago. Thus, I added the
variable org-diary-last-run-time and a conditional in org-diary that
only runs org-prepare-agenda-buffers if org-diary-last-run-time is less
than 1 second in the past. 

With the patch, it now takes appr. 5 seconds to generate the LaTeX
calendar with cal-tex and org-prepare-agenda-buffers is called only
once. 

--8<---------------cut here---------------start------------->8---
diff --git a/lisp/org-agenda.el b/lisp/org-agenda.el
index 797728b..6179907 100644
--- a/lisp/org-agenda.el
+++ b/lisp/org-agenda.el
@@ -4086,6 +4086,8 @@ Needed to avoid empty dates which mess up holiday display."
       (apply 'diary-add-to-list args)
     (apply 'add-to-diary-list args)))
 
+(defvar org-diary-last-run-time nil)
+
 ;;;###autoload
 (defun org-diary (&rest args)
   "Return diary information from org-files.
@@ -4123,8 +4125,14 @@ function from a program - use `org-agenda-get-day-entries' instead."
   (let* ((files (if (and entry (stringp entry) (string-match "\\S-" entry))
 		    (list entry)
 		  (org-agenda-files t)))
+	 (time (org-float-time))
 	 file rtn results)
-    (org-prepare-agenda-buffers files)
+    (when (or (not org-diary-last-run-time)
+	      (> (- time
+		    org-diary-last-run-time)
+		 1))
+      (org-prepare-agenda-buffers files))
+    (setq org-diary-last-run-time time)
     ;; If this is called during org-agenda, don't return any entries to
     ;; the calendar.  Org Agenda will list these entries itself.
     (if org-disable-agenda-to-diary (setq files nil))
--8<---------------cut here---------------end--------------->8---

Thanks for looking at this. I'm eager to know if there is a more elegant
way of accomplishing the same thing.

- Matt