bug#23377: 25.0.93; Completion is extremely slow for insert-char

[Eli Zaretskii]

> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Mon, 25 Apr 2016 21:10:50 -0700
> Cc: "N. Jackson" <nljlistbox2@gmail.com>, 23377@debbugs.gnu.org
> 
> Drew Adams wrote:
> > if the main reason to disable it is for performance in
> > an extreme use case (C-x 8 RET TAB)
> 
> It's not that extreme. It's natural for a user to get the whole list and then
> use C-s to find the desired character.

It surprises me that this is perceived as "natural", for an Emacs
user.  Do they also use this when completing on file names or buffer
names?  I don't think so.  So why would we assume they do so in this
case?  There are more than 30K names in the list popped up by the
above; how is it "reasonable", let alone economical, to search that
huge list, instead of typing some string to narrow down the list of
completions?