From ad2e20d8aab0d4d43fbac407736f05a94e65c49b Mon Sep 17 00:00:00 2001 From: Tamir Duberstein Date: Fri, 12 Jun 2026 17:27:44 -0400 Subject: [PATCH] ref-filter: restore prefix-scoped iteration dabecb9db2 (for-each-ref: introduce a '--start-after' option, 2025-07-15) changed branch, remote-tracking branch, and tag enumeration from constructing an iterator with the namespace prefix to constructing an unscoped iterator and seeking to the prefix. Review of --start-after noted that the construction prefix and seek position represent different state and are easy to conflate [1]. It also noted that future branch or tag support would need to retain the namespace prefix while moving the cursor [2]. The files backend constructs its loose-ref iterator with cache priming enabled. cache_ref_iterator_begin() immediately applies the construction prefix through cache_ref_iterator_set_prefix(), reading loose refs beneath it before packed refs are opened. An empty prefix therefore reads every loose ref, and a later seek cannot undo that I/O. For the current single-kind filters, construct the iterator with the namespace prefix when start_after is not set. Leave the existing start_after path unchanged; no current command combines it with these filters, and future support must carry the prefix separately from the cursor. With 10,000 unrelated loose refs in the files backend, the p6300 tests improve as follows: before after branch 2.74 s 0.11 s branch --remotes 2.81 s 0.12 s tag 3.01 s 0.11 s [1] https://lore.kernel.org/r/aGZidwwlToWThkn8@pks.im/ [2] https://lore.kernel.org/r/xmqqikjq7s16.fsf@gitster.g/ Fixes: dabecb9db2b2 ("for-each-ref: introduce a '--start-after' option") Suggested-by: Karthik Nayak Signed-off-by: Tamir Duberstein Signed-off-by: Junio C Hamano --- ref-filter.c | 13 ++++++------ t/perf/p6300-for-each-ref.sh | 39 +++++++++++++++++++++++++++++++++++- 2 files changed, 44 insertions(+), 8 deletions(-) diff --git a/ref-filter.c b/ref-filter.c index 1da4c0e60d..9b04e3af85 100644 --- a/ref-filter.c +++ b/ref-filter.c @@ -3316,15 +3316,14 @@ static int do_filter_refs(struct ref_filter *filter, unsigned int type, refs_for if (prefix) { struct ref_iterator *iter; + struct ref_store *store = get_main_ref_store(the_repository); - iter = refs_ref_iterator_begin(get_main_ref_store(the_repository), - "", NULL, 0, 0); - - if (filter->start_after) + if (filter->start_after) { + iter = refs_ref_iterator_begin(store, "", NULL, 0, 0); ret = start_ref_iterator_after(iter, filter->start_after); - else - ret = ref_iterator_seek(iter, prefix, - REF_ITERATOR_SEEK_SET_PREFIX); + } else { + iter = refs_ref_iterator_begin(store, prefix, NULL, 0, 0); + } if (!ret) ret = do_for_each_ref_iterator(iter, fn, cb_data); diff --git a/t/perf/p6300-for-each-ref.sh b/t/perf/p6300-for-each-ref.sh index fa7289c752..25ffa5e84c 100755 --- a/t/perf/p6300-for-each-ref.sh +++ b/t/perf/p6300-for-each-ref.sh @@ -1,6 +1,6 @@ #!/bin/sh -test_description='performance of for-each-ref' +test_description='performance of ref-filter users' . ./perf-lib.sh test_perf_fresh_repo @@ -84,4 +84,41 @@ test_expect_success 'pack refs' ' ' run_tests "packed" +test_expect_success 'setup many unrelated refs' ' + git init scoped && + test_commit -C scoped --no-tag base && + test_seq $ref_count_per_type | + sed "s,.*,update refs/custom/unrelated_& HEAD," | + git -C scoped update-ref --stdin && + git -C scoped update-ref refs/remotes/origin/main HEAD && + git -C scoped update-ref refs/tags/only HEAD +' + +test_perf "branch (many unrelated refs)" " + ( + cd scoped && + for i in \$(test_seq $test_iteration_count); do + git branch --format='%(refname)' >/dev/null + done + ) +" + +test_perf "branch --remotes (many unrelated refs)" " + ( + cd scoped && + for i in \$(test_seq $test_iteration_count); do + git branch --remotes --format='%(refname)' >/dev/null + done + ) +" + +test_perf "tag (many unrelated refs)" " + ( + cd scoped && + for i in \$(test_seq $test_iteration_count); do + git tag --format='%(refname)' >/dev/null + done + ) +" + test_done