Hi Ludovic, Ludovic Courtès <l...@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
