Re: agenda-view: match tags: Sorting by number of tags matched?

[Kyle Meyer <kyle@kyleam.com>]

Budiman Snowman writes:

> Suppose I have this document:
>
> * topic1                                               :tag1:tag2:tag3:
> * topic2                                               :tag1:tag2:tag4:
> * topic3                                               :tag1:tag3:tag4:
> * topic4                                               :tag2:tag3:tag4:
> * topic5                                               :tag1:tag2:
> * topic6                                               :tag1:tag4:
> * topic7                                               :tag3:tag4:
> * topic8                                               :tag1:
>
> And I turn on org-agenda m, then search for tag1|tag3|tag4. Emacs will then
> show the results (all entries match) in the above order.

org-agenda-sorting-strategy is the main option that controls sorting in
the agenda.  Going through the values there, I don't see anything
fitting your description.  But there is a user-defined-{up,down} option
that lets you implement your own logic via org-agenda-cmp-user-defined.
Here's an example.  It's probably brittle and inefficient in a number of
ways (and maybe completely wrong), but hopefully it gives you something
to start with.

  (add-to-list 'org-agenda-sorting-strategy
               '(tags user-defined-down))
  
  (defun my/org-agenda-cmp-num-tags-matched (a b)
    (when (and (eq (car org-agenda-redo-command) 'org-tags-view)
               org-agenda-query-string
               (string-match-p "|" org-agenda-query-string))
      (let* ((query-tags (split-string org-agenda-query-string "|"))
             (count (lambda (entry)
                      (length
                       (cl-intersection query-tags
                                        (get-text-property 0 'tags entry)
                                        :test #'equal))))
             (a-nmatched (funcall count a))
             (b-nmatched (funcall count b)))
        (cond
         ((> a-nmatched b-nmatched) 1)
         ((< a-nmatched b-nmatched) -1)))))
  
  (setq org-agenda-cmp-user-defined #'my/org-agenda-cmp-num-tags-matched)

> Is there a way for Emacs to show based on the number of tags matched
> ("sort based on relevance"), e.g.:
>
> * topic2                                               :tag1:tag2:tag4:
> * topic1                                               :tag1:tag2:tag3:
> * topic3                                               :tag1:tag3:tag4:
> * topic4                                               :tag2:tag3:tag4:
> * topic6                                               :tag1:tag4:
> * topic5                                               :tag1:tag2:
> * topic7                                               :tag3:tag4:
> * topic8                                               :tag1:

Hmm, your example query is "tag1|tag3|tag4", so a few of those lines
seem off.  For example, shouldn't topic 3 be at the top?  Anyway,
perhaps I'm misunderstanding your goal, but you should be able to adapt
the above approach to what you want.

Here are the results with the above custom sorting strategy and your
example query:

  topic3                                                            :tag1:tag3:tag4:
  topic1                                                            :tag1:tag2:tag3:
  topic2                                                            :tag1:tag2:tag4:
  topic4                                                            :tag2:tag3:tag4:
  topic6                                                                 :tag1:tag4:
  topic7                                                                 :tag3:tag4:
  topic5                                                                 :tag1:tag2:
  topic8                                                                      :tag1: