Getting rid of the mandb profile hook?

[Ludovic Courtès]

Hi Guix!

I was inspired by Michael Stapelberg’s talk recently shared on IRC¹
(well worth watching!).  One of the takeaways for me is that many
actions should be done lazily, in particular populating caches.

‘guix install’ & co. spend a significant time populating such caches, in
particular the XDG caches² and the manual page database (mandb).

I’m thinking we could get rid of the mandb hook.  However, the
functionality matters IMO (we need good tools so users can browse local
documentation; mandb is not that good but better than no search
mechanism.)  Here are several options that come to mind:

  1. Provide a ‘man’ wrapper or modify the ‘man-db’ package such that
     the database gets built on the first use of ‘man -k’, unless it’s
     already up-to-date.

  2. Add a phase in gnu-build-system.scm that creates a per-package
     database.  Change the mandb profile hook such that all it needs to
     do is “concatenate” all these GDBM databases (which should be much
     faster than browsing all the man pages as it currently does).

There are crazier option that came to mind but let’s ignore them for
now.

Thoughts?  :-)

Ludo’.

¹ “distri: researching fast Linux package management”
  
https://media.ccc.de/v/arch-conf-online-2020-6387-distri-researching-fast-linux-package-management

² https://issues.guix.gnu.org/44053#4