# Where parallels cross

Interesting bits of life

# Caching Yankpad snippets for a quicker note capturing

Yankpad's yankpad--snippets may have to read your snippets file multiple times to insert your snippet: here I "memoize" that function.

## The problem

I am preparing myself to a big lifestyle change which hopefully will wonderfully fill all my free time: so I want to make more of that!

One thing that I do pretty often is capturing tasks in Org Mode. That way I don't have to overload my mind remembering things I wish to do later. Recently I found myself waiting on my computer to capture a task. Very annoying. I dismissed the thing and moved on. But it kept happening: ouch!

My setup for capturing is a bit complex because I use snippets to setup my notes. Using snippets allows me to add metadata to my tasks that I can then analyze later to learn where I spend time most.

This means that the slowness can come from any of Yankpad, YASnippet or my own package ya-org-capture, which enables the snippet engine to work with Org Capture.

Only a good inspector can help with an opaque system. So I started the profiler: profiler-start, profiler-stop and profiler-report are your friends here.

After a bit of navigating in the profiler's report, I found that the function consuming most of the memory was yankpad--snippets.

If you don't use it, Yankpad allows you to store snippets in the YASnippet format within an Org Mode file. I find more enjoyable to maintain my snippets that way.

I discovered that any time that function gets called it opens your Org Mode file and reads its contents to find the snippets that apply in your context. For example, if you are editing a Clojure file, it will look for Clojure snippets only.

Long story short: the more snippets you have the longer this function takes. And I have just enough to cause a significant delay.

## And there is a solution

Time to change that function then! Caching is king here. In functional programming functions without side effects (said "pure") are equivalent to a dictionary input->output. When you have an expensive (in terms of time) function, you can just produce a dictionary of it. The next time you call that function it becomes super fast because the result is saved somewhere in memory. Functional languages usually come with a function called "memoize" which transforms any pure function into a dictionary.

Anyway we don't have that in Elisp, so given the current body of yankpad--snippets, we will make our handmade caching.

Currently the body looks like this.

(defun yankpad--snippets (category-name)
"Get an alist of the snippets in CATEGORY-NAME.
Each snippet is a list (NAME TAGS SRC-BLOCKS TEXT)."
(include (when propertystring
(split-string propertystring "|")))
(snippets
(append
(mapcar (lambda (d)
(list (concat (car d) yankpad-expand-separator) nil nil (cdr d)))
(cl-reduce #'append
'tree))))))
(append snippets (cl-reduce #'append (mapcar #'yankpad--snippets include)))))


The troublemaker above is org-with-point-at. That is basically reading the file, which is expensive. A little extra bit of knowledge to deepen the problem: a category in the Yankpad file may include other categories (which is a pretty cool feature). That also means that this function may run multiple times for each category (if it includes others). That means reading the same file multiple times: super slow = not cool!

Let's memoize/cache things then.

(defvar yankpad-snippets-cache nil "A dictionary category-name . snippets.")

"Get an alist of the snippets in CATEGORY-NAME.
Each snippet is a list (NAME TAGS SRC-BLOCKS TEXT)."
snippets
(include (when propertystring
(split-string propertystring "|")))
(snippets
(append
(mapcar (lambda (d)
(list (concat (car d) yankpad-expand-separator) nil nil (cdr d)))
(cl-reduce #'append
'tree)))))
(all-snippets (append snippets (cl-reduce #'append (mapcar #'yankpad--snippets include)))))
all-snippets)))


The cache/dictionary is yankpad-snippets-cache. The if-let checks if the cache contains the Yankpad category already, and returns that on a hit. On a miss we gather the snippets as before, add these snippets to the cache and finally return what we found.

The problem with caching is that now we have to maintain the cache. When we save a new snippet via Yankpad, the cached function above will not look at the file anymore but just at the yankpad-snippets-cache dictionary we made. We could handle this with something fancy like checking the file modification timestamp, but since I am probably the only person facing this issue, I just made my own function to reload snippets (and invalidate the cache):

(defun yankpad-my-reload ()
(interactive)