Subject: Re: [PATCH 1/3] revision: complicated pathspecs disable filters

From: Taylor Blau <[email-masked]>
Date: Sun, 12 Apr 2020 18:07:48 -0600

On Sun, Apr 12, 2020 at 03:30:07PM -0700, Junio C Hamano wrote:
> Taylor Blau <[email-masked]> writes:
>
> > I certainly wouldn't complain about a comment here explaining these
> > three checks, but I suppose that the rationale is only a 'git blame'
> > away (and I guess that is faster now after this series ;-)).
> >
> >> +	if (revs->prune_data.has_wildcard)
> >> +		return;
> >> +	if (revs->prune_data.nr > 1)
> >> +		return;
> >> +	if (revs->prune_data.magic ||
> >> +	    (revs->prune_data.nr &&
> >> +	     revs->prune_data.items[0].magic))
>
> This says "any magic", but it is overly pessimistic to disable the
> optimization for "literal" magic.  That magic is the one that lets
> well written scripts to say "I have in a '$variable' that the user
> gave me as a pathname (not pathspec), and it may have a wildcard
> letter in it, but please treat it as a literal string" by prefixing
> ":(literal)" before that user-supplied data, so it is punishing well
> disciplined folks.

I hadn't thought of that, but it makes sense to me. How about something
like this squashed into this patch? I moved the if-chain that Stolee
introduced out to its own function, at least since they seem
well-contained and related to one another. I figure that this simplifies
the implementation of 'prepare_to_use_bloom_filter' by giving the reader
less to think about up-front.

diff --git a/revision.c b/revision.c
index 534c0bf996..15bf4ccff5 100644
--- a/revision.c
+++ b/revision.c
@@ -654,6 +654,18 @@ static void trace2_bloom_filter_statistics_atexit(void)
        jw_release(&jw);
 }

+static int has_bloom_key(struct pathspec *spec)
+{
+       if (spec->has_wildcard)
+               return 0;
+       if (spec->nr > 1)
+               return 0;
+       if ((spec->magic & ~PATHSPEC_LITERAL) ||
+           (spec->nr && spec->items[0].magic & ~PATHSPEC_LITERAL))
+               return 0;
+       return 1;
+}
+
 static void prepare_to_use_bloom_filter(struct rev_info *revs)
 {
        struct pathspec_item *pi;
@@ -665,13 +677,7 @@ static void prepare_to_use_bloom_filter(struct rev_info *revs)
        if (!revs->commits)
            return;

-       if (revs->prune_data.has_wildcard)
-               return;
-       if (revs->prune_data.nr > 1)
-               return;
-       if (revs->prune_data.magic ||
-           (revs->prune_data.nr &&
-            revs->prune_data.items[0].magic))
+       if (!has_bloom_key(&revs->prune_data))
                return;

        repo_parse_commit(revs->repo, revs->commits->item);

> >> +		return;
> >> +
> >>  	repo_parse_commit(revs->repo, revs->commits->item);
> >>
> >>  	if (!revs->repo->objects->commit_graph)
> >> --
> >> gitgitgadget
> >
> >   Reviewed-by: Taylor Blau <[email-masked]>
> >
> > Thanks,
> > Taylor

Thanks,
Taylor