Re: emacs-27 b46c75b: xref-matches-in-files: Big Tramp speed-up

[Dmitry Gutov <dgutov@yandex.ru>]

On 08.01.2020 22:51, Stefan Monnier wrote:
> Yes, I saw that, but it's still not clear to me which part of this costs
> so much more than tramp-file-local-name itself, nor why.

The whole of it, mostly. I've shown a simple patch which improved 
performance a lot, by Michael says it's unmaintainable (IIUC):

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=34343#83

(and there's a follow-up suggestion later)

By the way, the commit under discussion already references this bug report.

> The "remote" pat would presumably be in the DIR argument (DIR would
> presumably be the root of the project or something like that).

The current discussion is about xref-matches-in-files where Grep acts on 
a list of files, not a directory. It's used by both project-find-regexp 
and dired-do-find-regexp.

> Actually, maybe xref could apply `file-local-name` to the root of
> the project?

See above. It's not about projects only.

I've considered about having xref-matches-in-files also accept a 
(REMOTE-ID LOCAL-FILES) struct, but that's also increase in complexity, 
in all callers and related APIs, which will also affect maintainability. 
So it's doable, but I'd rather make a good effort and fix it in Tramp to 
have everyone benefit automatically.