From: Garima Singh <garima.singh@xxxxxxxxxxxxx>
Add the core implementation for computing Bloom filters for
the paths changed between a commit and it's first parent.
We fill the Bloom filters as (const char *data, int len) pairs
as `struct bloom_filters" within a commit slab.
Filters for commits with no changes and more than 512 changes,
is represented with a filter of length zero. There is no gain
in distinguishing between a computed filter of length zero for
a commit with no changes, and an uncomputed filter for new commits
or for commits with more than 512 changes. The effect on
`git log -- path` is the same in both cases. We will fall back to
the normal diffing algorithm when we can't benefit from the
existence of Bloom filters.
Helped-by: Jeff King <peff@xxxxxxxx>
Helped-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
Reviewed-by: Jakub Narębski <jnareb@xxxxxxxxx>
Signed-off-by: Garima Singh <garima.singh@xxxxxxxxxxxxx>
---
bloom.c | 97 +++++++++++++++++++++++++++++++++++++++++++
bloom.h | 8 ++++
t/helper/test-bloom.c | 20 +++++++++
t/t0095-bloom.sh | 47 +++++++++++++++++++++
4 files changed, 172 insertions(+)
diff --git a/bloom.c b/bloom.c
index 888b67f1ea6..881a9841ede 100644
--- a/bloom.c
+++ b/bloom.c
@@ -1,5 +1,18 @@
#include "git-compat-util.h"
#include "bloom.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "revision.h"
+#include "hashmap.h"
+
+define_commit_slab(bloom_filter_slab, struct bloom_filter);
+
+struct bloom_filter_slab bloom_filters;
+
+struct pathmap_hash_entry {
+ struct hashmap_entry entry;
+ const char path[FLEX_ARRAY];
+};
static uint32_t rotate_left(uint32_t value, int32_t count)
{
@@ -107,3 +120,87 @@ void add_key_to_filter(const struct bloom_key *key,
filter->data[block_pos] |= get_bitmask(hash_mod);
}
}
+
+void init_bloom_filters(void)
+{
+ init_bloom_filter_slab(&bloom_filters);
+}
+
+struct bloom_filter *get_bloom_filter(struct repository *r,
+ struct commit *c)
+{
+ struct bloom_filter *filter;
+ struct bloom_filter_settings settings = DEFAULT_BLOOM_FILTER_SETTINGS;
+ int i;
+ struct diff_options diffopt;
+
+ if (bloom_filters.slab_size == 0)
+ return NULL;
+
+ filter = bloom_filter_slab_at(&bloom_filters, c);
+
+ repo_diff_setup(r, &diffopt);
+ diffopt.flags.recursive = 1;
+ diff_setup_done(&diffopt);
+
+ if (c->parents)
+ diff_tree_oid(&c->parents->item->object.oid, &c->object.oid, "", &diffopt);
+ else
+ diff_tree_oid(NULL, &c->object.oid, "", &diffopt);
+ diffcore_std(&diffopt);
+
+ if (diff_queued_diff.nr <= 512) {
+ struct hashmap pathmap;
+ struct pathmap_hash_entry *e;
+ struct hashmap_iter iter;
+ hashmap_init(&pathmap, NULL, NULL, 0);
+
+ for (i = 0; i < diff_queued_diff.nr; i++) {
+ const char *path = diff_queued_diff.queue[i]->two->path;
+
+ /*
+ * Add each leading directory of the changed file, i.e. for
+ * 'dir/subdir/file' add 'dir' and 'dir/subdir' as well, so
+ * the Bloom filter could be used to speed up commands like
+ * 'git log dir/subdir', too.
+ *
+ * Note that directories are added without the trailing '/'.
+ */
+ do {
+ char *last_slash = strrchr(path, '/');
+
+ FLEX_ALLOC_STR(e, path, path);
+ hashmap_entry_init(&e->entry, strhash(path));
+ hashmap_add(&pathmap, &e->entry);
+
+ if (!last_slash)
+ last_slash = (char*)path;
+ *last_slash = '\0';
+
+ } while (*path);
+
+ diff_free_filepair(diff_queued_diff.queue[i]);
+ }
+
+ filter->len = (hashmap_get_size(&pathmap) * settings.bits_per_entry + BITS_PER_WORD - 1) / BITS_PER_WORD;
+ filter->data = xcalloc(filter->len, sizeof(unsigned char));
+
+ hashmap_for_each_entry(&pathmap, &iter, e, entry) {
+ struct bloom_key key;
+ fill_bloom_key(e->path, strlen(e->path), &key, &settings);
+ add_key_to_filter(&key, filter, &settings);
+ }
+
+ hashmap_free_entries(&pathmap, struct pathmap_hash_entry, entry);
+ } else {
+ for (i = 0; i < diff_queued_diff.nr; i++)
+ diff_free_filepair(diff_queued_diff.queue[i]);
+ filter->data = NULL;
+ filter->len = 0;
+ }
+
+ free(diff_queued_diff.queue);
+ DIFF_QUEUE_CLEAR(&diff_queued_diff);
+
+ return filter;
+}
diff --git a/bloom.h b/bloom.h
index b9ce422ca2d..85ab8e9423d 100644
--- a/bloom.h
+++ b/bloom.h
@@ -1,6 +1,9 @@
#ifndef BLOOM_H
#define BLOOM_H
+struct commit;
+struct repository;
+
struct bloom_filter_settings {
/*
* The version of the hashing technique being used.
@@ -73,4 +76,9 @@ void add_key_to_filter(const struct bloom_key *key,
struct bloom_filter *filter,
const struct bloom_filter_settings *settings);
+void init_bloom_filters(void);
+
+struct bloom_filter *get_bloom_filter(struct repository *r,
+ struct commit *c);
+
#endif
\ No newline at end of file
diff --git a/t/helper/test-bloom.c b/t/helper/test-bloom.c
index 20460cde775..f18d1b722e1 100644
--- a/t/helper/test-bloom.c
+++ b/t/helper/test-bloom.c
@@ -1,6 +1,7 @@
#include "git-compat-util.h"
#include "bloom.h"
#include "test-tool.h"
+#include "commit.h"
struct bloom_filter_settings settings = DEFAULT_BLOOM_FILTER_SETTINGS;
@@ -32,6 +33,16 @@ static void print_bloom_filter(struct bloom_filter *filter) {
printf("\n");
}
+static void get_bloom_filter_for_commit(const struct object_id *commit_oid)
+{
+ struct commit *c;
+ struct bloom_filter *filter;
+ setup_git_directory();
+ c = lookup_commit(the_repository, commit_oid);
+ filter = get_bloom_filter(the_repository, c);
+ print_bloom_filter(filter);
+}
+
int cmd__bloom(int argc, const char **argv)
{
if (!strcmp(argv[1], "get_murmur3")) {
@@ -57,5 +68,14 @@ int cmd__bloom(int argc, const char **argv)
print_bloom_filter(&filter);
}
+ if (!strcmp(argv[1], "get_filter_for_commit")) {
+ struct object_id oid;
+ const char *end;
+ if (parse_oid_hex(argv[2], &oid, &end))
+ die("cannot parse oid '%s'", argv[2]);
+ init_bloom_filters();
+ get_bloom_filter_for_commit(&oid);
+ }
+
return 0;
}
\ No newline at end of file
diff --git a/t/t0095-bloom.sh b/t/t0095-bloom.sh
index 36a086c7c60..8f9eef116dc 100755
--- a/t/t0095-bloom.sh
+++ b/t/t0095-bloom.sh
@@ -67,4 +67,51 @@ test_expect_success 'compute bloom key for test string 2' '
test_cmp expect actual
'
+test_expect_success 'get bloom filters for commit with no changes' '
+ git init &&
+ git commit --allow-empty -m "c0" &&
+ cat >expect <<-\EOF &&
+ Filter_Length:0
+ Filter_Data:
+ EOF
+ test-tool bloom get_filter_for_commit "$(git rev-parse HEAD)" >actual &&
+ test_cmp expect actual
+'
+
+test_expect_success 'get bloom filter for commit with 10 changes' '
+ rm actual &&
+ rm expect &&
+ mkdir smallDir &&
+ for i in $(test_seq 0 9)
+ do
+ echo $i >smallDir/$i
+ done &&
+ git add smallDir &&
+ git commit -m "commit with 10 changes" &&
+ cat >expect <<-\EOF &&
+ Filter_Length:25
+ Filter_Data:82|a0|65|47|0c|92|90|c0|a1|40|02|a0|e2|40|e0|04|0a|9a|66|cf|80|19|85|42|23|
+ EOF
+ test-tool bloom get_filter_for_commit "$(git rev-parse HEAD)" >actual &&
+ test_cmp expect actual
+'
+
+test_expect_success EXPENSIVE 'get bloom filter for commit with 513 changes' '
+ rm actual &&
+ rm expect &&
+ mkdir bigDir &&
+ for i in $(test_seq 0 512)
+ do
+ echo $i >bigDir/$i
+ done &&
+ git add bigDir &&
+ git commit -m "commit with 513 changes" &&
+ cat >expect <<-\EOF &&
+ Filter_Length:0
+ Filter_Data:
+ EOF
+ test-tool bloom get_filter_for_commit "$(git rev-parse HEAD)" >actual &&
+ test_cmp expect actual
+'
+
test_done
\ No newline at end of file
--
gitgitgadget
