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Speed up git notes lookup

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To avoid looking up each and every commit in the notes ref's tree
object, which is very expensive, speed things up by slurping the tree
object's contents into a hash_map.

The idea for the hashmap singleton is from David Reiss, initial
benchmarking by Jeff King.

Note: the implementation allows for arbitrary entries in the notes
tree object, ignoring those that do not reference a valid object.  This
allows you to annotate arbitrary branches, or objects.

This patch has been improved by the following contributions:
- Junio C Hamano: fixed an obvious error in initialize_hash_map()

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Johannes Schindelin 2009-10-09 12:21:59 +02:00 committed by Junio C Hamano
parent 65d9fb487f
commit fd53c9eb44
1 changed files with 102 additions and 10 deletions
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112
notes.c
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@ -4,15 +4,112 @@
#include "refs.h"
#include "utf8.h"
#include "strbuf.h"
#include "tree-walk.h"
struct entry {
unsigned char commit_sha1[20];
unsigned char notes_sha1[20];
};
struct hash_map {
struct entry *entries;
off_t count, size;
};
static int initialized;
static struct hash_map hash_map;
static int hash_index(struct hash_map *map, const unsigned char *sha1)
{
int i = ((*(unsigned int *)sha1) % map->size);
for (;;) {
unsigned char *current = map->entries[i].commit_sha1;
if (!hashcmp(sha1, current))
return i;
if (is_null_sha1(current))
return -1 - i;
if (++i == map->size)
i = 0;
}
}
static void add_entry(const unsigned char *commit_sha1,
const unsigned char *notes_sha1)
{
int index;
if (hash_map.count + 1 > hash_map.size >> 1) {
int i, old_size = hash_map.size;
struct entry *old = hash_map.entries;
hash_map.size = old_size ? old_size << 1 : 64;
hash_map.entries = (struct entry *)
xcalloc(sizeof(struct entry), hash_map.size);
for (i = 0; i < old_size; i++)
if (!is_null_sha1(old[i].commit_sha1)) {
index = -1 - hash_index(&hash_map,
old[i].commit_sha1);
memcpy(hash_map.entries + index, old + i,
sizeof(struct entry));
}
free(old);
}
index = hash_index(&hash_map, commit_sha1);
if (index < 0) {
index = -1 - index;
hash_map.count++;
}
hashcpy(hash_map.entries[index].commit_sha1, commit_sha1);
hashcpy(hash_map.entries[index].notes_sha1, notes_sha1);
}
static void initialize_hash_map(const char *notes_ref_name)
{
unsigned char sha1[20], commit_sha1[20];
unsigned mode;
struct tree_desc desc;
struct name_entry entry;
void *buf;
if (!notes_ref_name || read_ref(notes_ref_name, commit_sha1) ||
get_tree_entry(commit_sha1, "", sha1, &mode))
return;
buf = fill_tree_descriptor(&desc, sha1);
if (!buf)
die("Could not read %s for notes-index", sha1_to_hex(sha1));
while (tree_entry(&desc, &entry))
if (!get_sha1(entry.path, commit_sha1))
add_entry(commit_sha1, entry.sha1);
free(buf);
}
static unsigned char *lookup_notes(const unsigned char *commit_sha1)
{
int index;
if (!hash_map.size)
return NULL;
index = hash_index(&hash_map, commit_sha1);
if (index < 0)
return NULL;
return hash_map.entries[index].notes_sha1;
}
void get_commit_notes(const struct commit *commit, struct strbuf *sb,
const char *output_encoding)
{
static const char utf8[] = "utf-8";
struct strbuf name = STRBUF_INIT;
unsigned char sha1[20];
unsigned char *sha1;
char *msg, *msg_p;
unsigned long linelen, msglen;
enum object_type type;
@ -23,17 +120,12 @@ void get_commit_notes(const struct commit *commit, struct strbuf *sb,
notes_ref_name = getenv(GIT_NOTES_REF_ENVIRONMENT);
else if (!notes_ref_name)
notes_ref_name = GIT_NOTES_DEFAULT_REF;
if (notes_ref_name && read_ref(notes_ref_name, sha1))
notes_ref_name = NULL;
initialize_hash_map(notes_ref_name);
initialized = 1;
}
if (!notes_ref_name)
return;
strbuf_addf(&name, "%s:%s", notes_ref_name,
sha1_to_hex(commit->object.sha1));
if (get_sha1(name.buf, sha1))
sha1 = lookup_notes(commit->object.sha1);
if (!sha1)
return;
if (!(msg = read_sha1_file(sha1, &type, &msglen)) || !msglen ||