@matheusbsbs / matheus-bagliano / commits / 16c4fa26b9

builtin/remote: only iterate through refs that are to be renamed

When renaming a remote we also need to rename all references accordingly. But while we only need to rename references that are contained in the "refs/remotes/$OLDNAME/" namespace, we end up using `refs_for_each_rawref()` that iterates through _all_ references. We know to exit early in the callback in case we see an irrelevant reference, but ultimately this is still a waste of compute as we knowingly iterate through references that we won't ever care about. Improve this by using `refs_for_each_rawref_in()`, which knows to only iterate through (potentially broken) references in a given prefix. The following benchmark renames a remote with a single reference in a repository that has 100k unrelated references. This shows a sizeable improvement with the "files" backend: Benchmark 1: rename remote (refformat = files, revision = HEAD~) Time (mean ± σ): 42.6 ms ± 0.9 ms [User: 29.1 ms, System: 8.4 ms] Range (min … max): 40.1 ms … 43.3 ms 10 runs Benchmark 2: rename remote (refformat = files, revision = HEAD) Time (mean ± σ): 31.7 ms ± 4.0 ms [User: 19.6 ms, System: 6.9 ms] Range (min … max): 27.1 ms … 36.0 ms 10 runs Summary rename remote (refformat = files, revision = HEAD) ran 1.35 ± 0.17 times faster than rename remote (refformat = files, revision = HEAD~) The "reftable" backend shows roughly the same absolute improvement, but given that it's already significantly faster than the "files" backend this translates to a much larger relative improvement: Benchmark 1: rename remote (refformat = reftable, revision = HEAD~) Time (mean ± σ): 18.2 ms ± 0.5 ms [User: 12.7 ms, System: 3.0 ms] Range (min … max): 17.3 ms … 21.4 ms 110 runs Benchmark 2: rename remote (refformat = reftable, revision = HEAD) Time (mean ± σ): 8.8 ms ± 0.5 ms [User: 3.8 ms, System: 2.9 ms] Range (min … max): 7.5 ms … 9.9 ms 167 runs Summary rename remote (refformat = reftable, revision = HEAD) ran 2.07 ± 0.12 times faster than rename remote (refformat = reftable, revision = HEAD~) Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patrick Steinhardt committed Jul 31, 2025 at 16:56 UTC 16c4fa26b99e6f6c24dc93575ffa884c13b1fe5f

3 files changed +13 -10

builtin/remote.c

+4 -9

@@ -720,16 +720,8 @@ static int rename_one_ref(const char *old_refname, const char *referent,

720 struct strbuf new_referent = STRBUF_INIT;

721 struct strbuf new_refname = STRBUF_INIT;

722 struct rename_info *rename = cb_data;

723 - const char *ptr = old_refname;

723 int error;

724

726 - if (!skip_prefix(ptr, "refs/remotes/", &ptr) ||

727 - !skip_prefix(ptr, rename->old_name, &ptr) ||

728 - !skip_prefix(ptr, "/", &ptr)) {

729 - error = 0;

730 - goto out;

731 - }

732 -

725 compute_renamed_ref(rename, old_refname, &new_refname);

726

727 if (flags & REF_ISSYMREF) {

@@ -932,7 +924,10 @@ static int mv(int argc, const char **argv, const char *prefix,

924 rename.progress = start_delayed_progress(the_repository,

925 _("Renaming remote references"), 0);

926

935 - result = refs_for_each_rawref(get_main_ref_store(the_repository),

927 + strbuf_reset(&buf);

928 + strbuf_addf(&buf, "refs/remotes/%s/", rename.old_name);

929 +

930 + result = refs_for_each_rawref_in(get_main_ref_store(the_repository), buf.buf,

931 rename_one_ref, &rename);

932 if (result < 0)

933 die(_("queueing remote ref renames failed: %s"), rename.err->buf);

refs.c

+7 -1

@@ -1839,7 +1839,13 @@ int refs_for_each_namespaced_ref(struct ref_store *refs,

1839

1840 int refs_for_each_rawref(struct ref_store *refs, each_ref_fn fn, void *cb_data)

1841 {

1842 - return do_for_each_ref(refs, "", NULL, fn, 0,

1842 + return refs_for_each_rawref_in(refs, "", fn, cb_data);

1843 +}

1844 +

1845 +int refs_for_each_rawref_in(struct ref_store *refs, const char *prefix,

1846 + each_ref_fn fn, void *cb_data)

1847 +{

1848 + return do_for_each_ref(refs, prefix, NULL, fn, 0,

1849 DO_FOR_EACH_INCLUDE_BROKEN, cb_data);

1850 }

1851

refs.h

@@ -428,6 +428,8 @@ int refs_for_each_namespaced_ref(struct ref_store *refs,

428

429 /* can be used to learn about broken ref and symref */

430 int refs_for_each_rawref(struct ref_store *refs, each_ref_fn fn, void *cb_data);

431 +int refs_for_each_rawref_in(struct ref_store *refs, const char *prefix,

432 + each_ref_fn fn, void *cb_data);

433

434 /*

435 * Iterates over all refs including root refs, i.e. pseudorefs and HEAD.