bug#47711: bug#48841: bug#47711: [PATCH VERSION 2] Add new `completion-filter-completions` API and deferred highlighting

[Eli Zaretskii <eliz@gnu.org>]

> Cc: Dmitry Gutov <dgutov@yandex.ru>, Lars Ingebrigtsen <larsi@gnus.org>,
>  47711@debbugs.gnu.org, 48841@debbugs.gnu.org,
>  Stefan Monnier <monnier@iro.umontreal.ca>, Eli Zaretskii <eliz@gnu.org>
> From: Daniel Mendler <mail@daniel-mendler.de>
> Date: Mon, 16 Aug 2021 12:52:58 +0200
> 
> On 8/16/21 12:15 PM, João Távora wrote:
> > On Mon, Aug 16, 2021 at 10:09 AM Daniel Mendler <mail@daniel-mendler.de> wrote:
> > 
> >> There are serious drawbacks of attaching "private" string properties to
> >> arbitrary strings. For once it complicates debugging seriously if there
> >> are suddenly string properties attached to symbol names. It also leads
> >> to a potential memory leak.
> > 
> > Please, in the name of the sanity of this discussion, justify these two
> > statements with examples or follow them with a clause like "because...".
> 
> João, I am giving hard examples here. What is not an example about
> "memory leak" or making debugging output verbose thanks to the attached
> string properties?

FWIW, I also don't understand how adding properties could cause a
memory leak.  When a string is GCed, its properties get GCed as well,
all of them.  Am I missing something?

As to more difficult debugging, I think adding a couple of properties
that have simple structure will not impair debugging too much.
Strings with many properties are not uncommon in Emacs, so we already
have to deal with that.

> As I said, I will ensure that my API does not introduce performance
> regressions. And since my new API performs strictly less work than your
> proposal it will necessarily be faster if you consider only the
> filtering, which is what matters for incrementally updating UIs.

I would indeed suggest both to make sure there's no performance
regressions, and would like to see some data similar to what João
presented, which backs up your assessments about your proposal being
faster.  Since performance is the main motivation for these changes, I
think it's important for us to be on the same page wrt facts related
to performance, before we make the decision how to proceed.

Thanks.