Jacob VosmaerRe: [PATCH 1/1] ls-refs.c: minimize number of refs visited
Hi Taylor,
Thanks for your reply. That sounds like a great idea!
On Tue, Jan 19, 2021 at 5:12 PM Taylor Blau <me@ttaylorr.com> wrote:
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> But, I think that we could get pretty far by treating the prefixes as > refs so that we can call ref-filter.c:find_longest_prefixes(). For its > purposes, it doesn't really care about whether or not the arguments > actually are references. It simply returns the longest common prefix > among all of its arguments (delimited by '/' characters).
What does "delimited by /" mean?
Without really understanding the longest common prefix code in ref-filter.c, my intuitive concern is that the specifics of glob matching and special treatment of '/' may bite us. I suppose we'll be fine because ls-refs has its own matching logic. So long as for_each_fullref_in_prefixes yield enough prefixes, the end result would remain the same.
The question is then, does for_each_fullref_in_prefixes yield everything we need?
I think my approach would be to expose the new for_each_fullref_in_prefixes iterator you propose through test-tool, and unit test it so we can be sure it handles both contexts (for-each-refs with globs and special '/', and ls-refs without any special character behavior) correctly.
I may be overly cautious here, take this with a grain of salt because I am not an experienced Git contributor. On that topic, apologies if I'm botching my inline replies in this email.
Regarding your patch: it works correctly and as fast as expected for my development "many refs" test case. Yay! It also segfaults and fails some tests but see my comments below.
All in all: thanks, great idea, yes we should reuse, I only lack confidence on correctness because I don't fully grasp your longest-common-prefix algorithm yet.
Cheers, Jacob
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> --- >8 ---
>
> Subject: [PATCH] ls-refs: iterate longest common refs prefix
>
> Signed-off-by: Taylor Blau <me@ttaylorr.com>
> ---
> ls-refs.c | 4 +++-
> ref-filter.c | 46 ++++++++++++++++++++++++++++++++--------------
> ref-filter.h | 10 ++++++++++
> 3 files changed, 45 insertions(+), 15 deletions(-)
>
> diff --git a/ls-refs.c b/ls-refs.c
> index a1e0b473e4..6a3e11d45c 100644
> --- a/ls-refs.c
> +++ b/ls-refs.c
> @@ -6,6 +6,7 @@
> #include "ls-refs.h"
> #include "pkt-line.h"
> #include "config.h"
> +#include "ref-filter.h"
>
> /*
> * Check if one of the prefixes is a prefix of the ref.
> @@ -109,7 +110,8 @@ int ls_refs(struct repository *r, struct strvec *keys,
> die(_("expected flush after ls-refs arguments"));
>
> head_ref_namespaced(send_ref, &data);
> - for_each_namespaced_ref(send_ref, &data);
> + for_each_fullref_in_prefixes(get_git_namespace(), data.prefixes.v,
> + send_ref, &data, 0);Remember to add that strvec_init(&data.prefixes) I talked about in my commit message, or you get a segfault.
You also need: if (!data.prefixes.nr) strvec_push(&data.prefixes, "refs/");
Without it, the "ls-refs without ref-prefix" scenario fails.
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> packet_flush(1);
> strvec_clear(&data.prefixes);
> return 0;
> diff --git a/ref-filter.c b/ref-filter.c
> index aa260bfd09..c34bf34d06 100644
> --- a/ref-filter.c
> +++ b/ref-filter.c
> @@ -1987,6 +1987,36 @@ static void find_longest_prefixes(struct string_list *out,
> strbuf_release(&prefix);
> }
>
> +int for_each_fullref_in_prefixes(const char *namespace,
> + const char **patterns,
> + each_ref_fn cb,
> + void *cb_data,
> + int broken)
> +{
> + struct string_list prefixes = STRING_LIST_INIT_DUP;
> + struct string_list_item *prefix;
> + struct strbuf buf = STRBUF_INIT;
> + int ret = 0, namespace_len;
> +
> + find_longest_prefixes(&prefixes, patterns);
> +
> + if (namespace)
> + strbuf_addstr(&buf, namespace);
> + namespace_len = buf.len;
> +
> + for_each_string_list_item(prefix, &prefixes) {
> + strbuf_addf(&buf, prefix->string);Missing format string "%s".
Show 66 quoted lines
> + ret = for_each_fullref_in(buf.buf, cb, cb_data, broken);
> + if (ret)
> + break;
> + strbuf_setlen(&buf, namespace_len);
> + }
> +
> + string_list_clear(&prefixes, 0);
> + strbuf_release(&buf);
> + return ret;
> +}
> +
> /*
> * This is the same as for_each_fullref_in(), but it tries to iterate
> * only over the patterns we'll care about. Note that it _doesn't_ do a full
> @@ -1997,10 +2027,6 @@ static int for_each_fullref_in_pattern(struct ref_filter *filter,
> void *cb_data,
> int broken)
> {
> - struct string_list prefixes = STRING_LIST_INIT_DUP;
> - struct string_list_item *prefix;
> - int ret;
> -
> if (!filter->match_as_path) {
> /*
> * in this case, the patterns are applied after
> @@ -2024,16 +2050,8 @@ static int for_each_fullref_in_pattern(struct ref_filter *filter,
> return for_each_fullref_in("", cb, cb_data, broken);
> }
>
> - find_longest_prefixes(&prefixes, filter->name_patterns);
> -
> - for_each_string_list_item(prefix, &prefixes) {
> - ret = for_each_fullref_in(prefix->string, cb, cb_data, broken);
> - if (ret)
> - break;
> - }
> -
> - string_list_clear(&prefixes, 0);
> - return ret;
> + return for_each_fullref_in_prefixes(NULL, filter->name_patterns,
> + cb, cb_data, broken);
> }
>
> /*
> diff --git a/ref-filter.h b/ref-filter.h
> index feaef4a8fd..f666a0fb49 100644
> --- a/ref-filter.h
> +++ b/ref-filter.h
> @@ -146,4 +146,14 @@ struct ref_array_item *ref_array_push(struct ref_array *array,
> const char *refname,
> const struct object_id *oid);
>
> +/**
> + * iterate all refs which descend from the longest common prefix among
> + * "patterns".
> + */
> +int for_each_fullref_in_prefixes(const char *namespace,
> + const char **patterns,
> + each_ref_fn cb,
> + void *cb_data,
> + int broken);
> +
> #endif /* REF_FILTER_H */
> --
> 2.30.0.138.g6d7191ea01
>
