bug#23223: 25.0.92; Can xref-find-references be sped up?

[Eli Zaretskii]

> Cc: 23223-done@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 12 Apr 2016 21:49:14 +0300
> 
> > Btw, I noticed another strange thing, but I was only able to reproduce
> > it with the current version, before your patch: the set of results
> > returned by xref-find-references, when it uses IDUtils, is not
> > entirely repeatable.  Sometimes, a few matches, sometimes a few dozen
> > of them, are missing.  I have no idea why; the lid command
> > consistently returns the same number of lines each time I invoke it.
> 
> That sounds troubling. Please report if you encounter this again, 

I just did, with the current emacs-25 branch.

> together with: do you get different results when immediately repeating 
> the same search? Or do you search from different files, in different 
> directories?

The same search, immediately repeated from the same directory.  More
accurately, the first time I invoke xref-find-references in the
top-level directory of the Emacs repository, I get 980 matches;
thereafter, all the subsequent searches from the same Emacs session
yield 1128 matches.  This is with the ID database present in the
top-level directory.

> Getting different results between searches from c-mode and 
> emacs-lisp-mode is to be expected, because the latter searches in all 
> load-path as well (and it ends up using Grep in most of those 
> directories anyway).

All the searches are done from *scratch* in "emacs -Q".

Let me know if I can provide more info.