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Re: Getting rid of the mandb profile hook?
From: |
Maxim Cournoyer |
Subject: |
Re: Getting rid of the mandb profile hook? |
Date: |
Sat, 27 Feb 2021 08:05:22 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) |
Hi Ludovic,
Ludovic Courtès <ludo@gnu.org> writes:
> 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.
That would mean the database would live in some user-specific writable
area of the file system correct (where?), right? And could use the
common 'update' mechanism of man-db to make it as fast as possible.
This sounds good from a performance perpective, but could introduce
cache issues every now and then (if man-db changes a lot). I wouldn't
expect much problem given how mature man-db is, but that's one thing to
consider.
> 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).
I like that idea better, but I don't know how feasible it would be.
> There are crazier option that came to mind but let’s ignore them for
> now.
What is taking so much time anyway? Why is generating this database so
compute intensive? I don't grok why it should be so inefficient to scan
a union'd tree for expected prefixes and append a bunch of file names
together.
> Thoughts? :-)
Lazily doing things seems a good idea in general to make the experience
more snappy. Thanks for looking into it!
Maxim
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