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refs: speed up refs_for_each_glob_ref_in()

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The function `refs_for_each_glob_ref_in()` can be used to iterate
through all refs in a specific prefix with globbing. The logic to handle
this is currently hosted by `refs_for_each_glob_ref_in()`, which sets up
a callback function that knows to filter out refs that _don't_ match the
given globbing pattern.

The way we do this is somewhat inefficient though: even though the
function is expected to only yield refs in the given prefix, we still
end up iterating through _all_ references, regardless of whether or not
their name matches the given prefix.

Extend `refs_for_each_ref_ext()` so that it can handle patterns and
adapt `refs_for_each_glob_ref_in()` to use it. This means we continue to
use the same callback-based infrastructure to filter individual refs via
the globbing pattern, but we can now also use the other functionality of
the `_ext()` variant.

Most importantly, this means that we now properly handle the prefix.
This results in a performance improvement when using a prefix where a
significant majority of refs exists outside of the prefix. The following
benchmark is an extreme case, with 1 million refs that exist outside the
prefix and a single ref that exists inside it:

    Benchmark 1: git rev-parse --branches=refs/heads/* (rev = HEAD~)
      Time (mean ± σ):     115.9 ms ±   0.7 ms    [User: 113.0 ms, System: 2.4 ms]
      Range (min … max):   114.9 ms … 117.8 ms    25 runs

    Benchmark 2: git rev-parse --branches=refs/heads/* (rev = HEAD)
      Time (mean ± σ):       1.1 ms ±   0.1 ms    [User: 0.3 ms, System: 0.7 ms]
      Range (min … max):     1.0 ms …   2.3 ms    2092 runs

    Summary
      git rev-parse --branches=refs/heads/* (rev = HEAD) ran
      107.01 ± 6.49 times faster than git rev-parse --branches=refs/heads/* (rev = HEAD~)

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Patrick Steinhardt
2026-02-23 12:59:41 +01:00
committed by Junio C Hamano
parent aefcc9b367
commit daf01b1366
2 changed files with 64 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

87
refs.c
View File

@@ -444,7 +444,7 @@ char *refs_resolve_refdup(struct ref_store *refs,
/* The argument to for_each_filter_refs */
struct for_each_ref_filter {
const char *pattern;
const char *prefix;
size_t trim_prefix;
refs_for_each_cb *fn;
void *cb_data;
};
@@ -475,9 +475,11 @@ static int for_each_filter_refs(const struct reference *ref, void *data)
if (wildmatch(filter->pattern, ref->name, 0))
return 0;
if (filter->prefix) {
if (filter->trim_prefix) {
struct reference skipped = *ref;
skip_prefix(skipped.name, filter->prefix, &skipped.name);
if (strlen(skipped.name) <= filter->trim_prefix)
BUG("attempt to trim too many characters");
skipped.name += filter->trim_prefix;
return filter->fn(&skipped, filter->cb_data);
} else {
return filter->fn(ref, filter->cb_data);
@@ -590,40 +592,24 @@ void normalize_glob_ref(struct string_list_item *item, const char *prefix,
strbuf_release(&normalized_pattern);
}
int refs_for_each_glob_ref_in(struct ref_store *refs, refs_for_each_cb fn,
int refs_for_each_glob_ref_in(struct ref_store *refs, refs_for_each_cb cb,
const char *pattern, const char *prefix, void *cb_data)
{
struct strbuf real_pattern = STRBUF_INIT;
struct for_each_ref_filter filter;
int ret;
if (!prefix && !starts_with(pattern, "refs/"))
strbuf_addstr(&real_pattern, "refs/");
else if (prefix)
strbuf_addstr(&real_pattern, prefix);
strbuf_addstr(&real_pattern, pattern);
if (!has_glob_specials(pattern)) {
/* Append implied '/' '*' if not present. */
strbuf_complete(&real_pattern, '/');
/* No need to check for '*', there is none. */
strbuf_addch(&real_pattern, '*');
}
filter.pattern = real_pattern.buf;
filter.prefix = prefix;
filter.fn = fn;
filter.cb_data = cb_data;
ret = refs_for_each_ref(refs, for_each_filter_refs, &filter);
strbuf_release(&real_pattern);
return ret;
struct refs_for_each_ref_options opts = {
.pattern = pattern,
.prefix = prefix,
.trim_prefix = prefix ? strlen(prefix) : 0,
};
return refs_for_each_ref_ext(refs, cb, cb_data, &opts);
}
int refs_for_each_glob_ref(struct ref_store *refs, refs_for_each_cb fn,
int refs_for_each_glob_ref(struct ref_store *refs, refs_for_each_cb cb,
const char *pattern, void *cb_data)
{
return refs_for_each_glob_ref_in(refs, fn, pattern, NULL, cb_data);
struct refs_for_each_ref_options opts = {
.pattern = pattern,
};
return refs_for_each_ref_ext(refs, cb, cb_data, &opts);
}
const char *prettify_refname(const char *name)
@@ -1862,16 +1848,51 @@ int refs_for_each_ref_ext(struct ref_store *refs,
refs_for_each_cb cb, void *cb_data,
const struct refs_for_each_ref_options *opts)
{
struct strbuf real_pattern = STRBUF_INIT;
struct for_each_ref_filter filter;
struct ref_iterator *iter;
size_t trim_prefix = opts->trim_prefix;
int ret;
if (!refs)
return 0;
if (opts->pattern) {
if (!opts->prefix && !starts_with(opts->pattern, "refs/"))
strbuf_addstr(&real_pattern, "refs/");
else if (opts->prefix)
strbuf_addstr(&real_pattern, opts->prefix);
strbuf_addstr(&real_pattern, opts->pattern);
if (!has_glob_specials(opts->pattern)) {
/* Append implied '/' '*' if not present. */
strbuf_complete(&real_pattern, '/');
/* No need to check for '*', there is none. */
strbuf_addch(&real_pattern, '*');
}
filter.pattern = real_pattern.buf;
filter.trim_prefix = opts->trim_prefix;
filter.fn = cb;
filter.cb_data = cb_data;
/*
* We need to trim the prefix in the callback function as the
* pattern is expected to match on the full refname.
*/
trim_prefix = 0;
cb = for_each_filter_refs;
cb_data = &filter;
}
iter = refs_ref_iterator_begin(refs, opts->prefix ? opts->prefix : "",
opts->exclude_patterns,
opts->trim_prefix, opts->flags);
trim_prefix, opts->flags);
return do_for_each_ref_iterator(iter, cb, cb_data);
ret = do_for_each_ref_iterator(iter, cb, cb_data);
strbuf_release(&real_pattern);
return ret;
}
int refs_for_each_ref(struct ref_store *refs, refs_for_each_cb cb, void *cb_data)

10
refs.h
View File

@@ -458,6 +458,16 @@ struct refs_for_each_ref_options {
/* Only iterate over references that have this given prefix. */
const char *prefix;
/*
* A globbing pattern that can be used to only yield refs that match.
* If given, refs will be matched against the pattern with
* `wildmatch()`.
*
* If the pattern doesn't contain any globbing characters then it is
* treated as if it was ending with "/" and "*".
*/
const char *pattern;
/*
* Exclude any references that match any of these patterns on a
* best-effort basis. The caller needs to be prepared for the exclude