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author | Garima Singh <garima.singh@microsoft.com> | 2020-03-30 00:31:26 +0000 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2020-03-30 09:59:53 -0700 |
commit | ed591febb4a201ce48b34a4e90027414cd0d7966 (patch) | |
tree | a928b663ad556a34b2f69ac991eb84663a95e4d5 /bloom.c | |
parent | f1294eaf7fbf7673567b698b11e062566b9f1035 (diff) | |
download | git-ed591febb4a201ce48b34a4e90027414cd0d7966.tar.gz |
bloom.c: core Bloom filter implementation for changed paths.
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@peff.net>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Jakub Narębski <jnareb@gmail.com>
Signed-off-by: Garima Singh <garima.singh@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'bloom.c')
-rw-r--r-- | bloom.c | 97 |
1 files changed, 97 insertions, 0 deletions
@@ -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; +} |