@matheusbsbs / matheus-bagliano / commits / b9584c5858

ref-filter: avoid parsing tagged objects in match_points_at()

When we peel tags to check if they match a --points-at oid, we recursively parse the tagged object to see if it is also a tag. But since the tag itself tells us the type of the object it points to (and even gives us the appropriate object struct via its "tagged" member), we can use that directly. We do still have to make sure to call parse_tag() before looking at each tag. This is redundant for the outermost tag (since we did call parse_object() to find its type), but that's OK; parse_tag() is smart enough to make this a noop when the tag has already been parsed. In my clone of linux.git, with 782 tags (and only 3 non-tags), this yields a significant speedup (bringing us back where we were before the commit before this one started recursively dereferencing tags): Benchmark 1: ./git.old for-each-ref --points-at=HEAD --format="%(refname)" Time (mean ± σ): 20.3 ms ± 0.5 ms [User: 11.1 ms, System: 9.1 ms] Range (min … max): 19.6 ms … 21.5 ms 141 runs Benchmark 2: ./git.new for-each-ref --points-at=HEAD --format="%(refname)" Time (mean ± σ): 11.4 ms ± 0.2 ms [User: 6.3 ms, System: 5.0 ms] Range (min … max): 11.0 ms … 12.2 ms 250 runs Summary './git.new for-each-ref --points-at=HEAD --format="%(refname)"' ran 1.79 ± 0.05 times faster than './git.old for-each-ref --points-at=HEAD --format="%(refname)"' Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Jul 2, 2023 at 18:35 UTC b9584c5858799d5603851af5f0dbad5e7af29b22

1 file changed +10 -2

ref-filter.c

+10 -2

@@ -2346,10 +2346,18 @@ static const struct object_id *match_points_at(struct oid_array *points_at,

2346 return oid;

2347 obj = parse_object(the_repository, oid);

2348 while (obj && obj->type == OBJ_TAG) {

2349 - oid = get_tagged_oid((struct tag *)obj);

2349 + struct tag *tag = (struct tag *)obj;

2350 +

2351 + if (parse_tag(tag) < 0) {

2352 + obj = NULL;

2353 + break;

2354 + }

2355 +

2356 + oid = get_tagged_oid(tag);

2357 if (oid_array_lookup(points_at, oid) >= 0)

2358 return oid;

2352 - obj = parse_object(the_repository, oid);

2359 +

2360 + obj = tag->tagged;

2361 }

2362 if (!obj)

2363 die(_("malformed object at '%s'"), refname);