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sha1_name: use bsearch_pack() for abbreviations

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When computing abbreviation lengths for an object ID against a single
packfile, the method find_abbrev_len_for_pack() currently implements
binary search. This is one of several implementations. One issue with
this implementation is that it ignores the fanout table in the pack-
index.

Translate this binary search to use the existing bsearch_pack() method
that correctly uses a fanout table.

Due to the use of the fanout table, the abbreviation computation is
slightly faster than before. For a fully-repacked copy of the Linux
repo, the following 'git log' commands improved:

* git log --oneline --parents --raw
  Before: 59.2s
  After:  56.9s
  Rel %:  -3.8%

* git log --oneline --parents
  Before: 6.48s
  After:  5.91s
  Rel %: -8.9%

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2018-03-22 13:40:10 -04:00 committed by Junio C Hamano
parent 3d475f46a8
commit 0aaf05b3bd
1 changed files with 4 additions and 20 deletions
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24
sha1_name.c
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@ -512,32 +512,16 @@ static void find_abbrev_len_for_pack(struct packed_git *p,
struct min_abbrev_data *mad)
{
int match = 0;
uint32_t num, last, first = 0;
uint32_t num, first = 0;
struct object_id oid;
const struct object_id *mad_oid;
if (open_pack_index(p) || !p->num_objects)
return;
num = p->num_objects;
last = num;
while (first < last) {
uint32_t mid = first + (last - first) / 2;
const unsigned char *current;
int cmp;
current = nth_packed_object_sha1(p, mid);
cmp = hashcmp(mad->oid->hash, current);
if (!cmp) {
match = 1;
first = mid;
break;
}
if (cmp > 0) {
first = mid + 1;
continue;
}
last = mid;
}
mad_oid = mad->oid;
match = bsearch_pack(mad_oid, p, &first);
/*
* first is now the position in the packfile where we would insert