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From 47c61004c7cfbb8662b13fac813b45e3fd214665 Mon Sep 17 00:00:00 2001
Message-Id: <47c61004c7cfbb8662b13fac813b45e3fd214665.1631166322.git.ps@pks.im>
In-Reply-To: <fe7df03a9a2fa434ebce38b2cd5e6da42f8b2692.1631166322.git.ps@pks.im>
References: <fe7df03a9a2fa434ebce38b2cd5e6da42f8b2692.1631166322.git.ps@pks.im>
From: Patrick Steinhardt <ps@pks.im>
Date: Wed, 1 Sep 2021 15:09:45 +0200
Subject: [PATCH 09/14] fetch: avoid unpacking headers in object existence
check
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
When updating local refs after the fetch has transferred all objects, we
do an object existence test as a safety guard to avoid updating a ref to
an object which we don't have. We do so via `oid_object_info()`: if it
returns an error, then we know the object does not exist.
One side effect of `oid_object_info()` is that it parses the object's
type, and to do so it must unpack the object header. This is completely
pointless: we don't care for the type, but only want to assert that the
object exists.
Refactor the code to use `repo_has_object_file()`, which both makes the
code's intent clearer and is also faster because it does not unpack
object headers. In a real-world repo with 2.3M refs, this results in a
small speedup when doing a mirror-fetch:
Benchmark #1: HEAD~: git-fetch
Time (mean ± σ): 33.686 s ± 0.176 s [User: 30.119 s, System: 5.262 s]
Range (min … max): 33.512 s … 33.944 s 5 runs
Benchmark #2: HEAD: git-fetch
Time (mean ± σ): 31.247 s ± 0.195 s [User: 28.135 s, System: 5.066 s]
Range (min … max): 30.948 s … 31.472 s 5 runs
Summary
'HEAD: git-fetch' ran
1.08 ± 0.01 times faster than 'HEAD~: git-fetch'
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
builtin/fetch.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 91d1301613..01513e6aea 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -846,13 +846,11 @@ static int update_local_ref(struct ref *ref,
int summary_width)
{
struct commit *current = NULL, *updated;
- enum object_type type;
struct branch *current_branch = branch_get(NULL);
const char *pretty_ref = prettify_refname(ref->name);
int fast_forward = 0;
- type = oid_object_info(the_repository, &ref->new_oid, NULL);
- if (type < 0)
+ if (!repo_has_object_file(the_repository, &ref->new_oid))
die(_("object %s not found"), oid_to_hex(&ref->new_oid));
if (oideq(&ref->old_oid, &ref->new_oid)) {
--
2.33.0
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