bug#64735: 29.0.92; find invocations are ~15x slower because of ignores

[Dmitry Gutov]

On 23/07/2023 14:18, Eli Zaretskii wrote:
> > Date: Sun, 23 Jul 2023 13:46:30 +0300
> > Cc:luangruo@yahoo.com,sbaugh@janestreet.com,yantar92@posteo.net,
> >   64735@debbugs.gnu.org
> > From: Dmitry Gutov<dmitry@gutov.dev>
> >
> > On 23/07/2023 08:11, Eli Zaretskii wrote:
> > > Even better: compute completion-regexp-list so that IGNOREs are
> > > filtered by file-name-all-completions in the first place.
> > We don't have lookahead in Emacs regexps, so I'm not sure it's possible
> > to construct regexp that says "don't match entries A, B and C".
> Well, maybe just having a way of telling file-name-all-completions to
> negate the sense of completion-regexp-list would be enough to make
> that happen?

Some way to do that is certainly possible (e.g. a new option and 
corresponding code, maybe; maybe not), it's just that the person 
implementing it should consider the performance of the resulting solution.

And, ideally, do all the relevant benchmarking when proposing the change.