> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>
> The 'git multi-pack-index expire' command looks at the existing
> mult-pack-index, counts the number of objects referenced in each
> pack-file, deletes the pack-fils with no referenced objects, and
> rewrites the multi-pack-index to no longer reference those packs.
Thanks - this was quite straightforwardly written.
> @@ -745,7 +761,10 @@ int write_midx_file(const char *object_dir)
> midx_name);
> }
>
> - packs.m = load_multi_pack_index(object_dir, 1);
> + if (m)
> + packs.m = m;
> + else
> + packs.m = load_multi_pack_index(object_dir, 1);
If we already loaded the m, we can just pass it in - OK.
> + if (packs_to_drop && packs_to_drop->nr) {
> + int drop_index = 0;
> + int missing_drops = 0;
> +
> + for (i = 0; i < packs.nr && drop_index < packs_to_drop->nr; i++) {
> + int cmp = strcmp(packs.info[i].pack_name,
> + packs_to_drop->items[drop_index].string);
> +
> + if (!cmp) {
> + drop_index++;
> + packs.info[i].expired = 1;
> + } else if (cmp > 0) {
> + error(_("did not see pack-file %s to drop"),
> + packs_to_drop->items[drop_index].string);
> + drop_index++;
> + missing_drops++;
> + i--;
> + } else {
> + packs.info[i].expired = 0;
> + }
> + }
> +
> + if (missing_drops) {
> + result = 1;
> + goto cleanup;
> + }
> + }
This takes into account that packfiles can shift while we run this
command, I see. Other than that, this is a common pattern - how we
iterate through 2 sorted arrays, one a subsequence of each other.
And indeed packs_to_drop is a sorted list, because we use
string_list_insert() below.
> ALLOC_ARRAY(pack_perm, packs.nr);
> for (i = 0; i < packs.nr; i++) {
> - pack_perm[packs.info[i].orig_pack_int_id] = i;
> + if (packs.info[i].expired) {
> + dropped_packs++;
> + pack_perm[packs.info[i].orig_pack_int_id] = PACK_EXPIRED;
> + } else {
> + pack_perm[packs.info[i].orig_pack_int_id] = i - dropped_packs;
> + }
Here...
> }
>
> - for (i = 0; i < packs.nr; i++)
> - pack_name_concat_len += strlen(packs.info[i].pack_name) + 1;
> + for (i = 0; i < packs.nr; i++) {
> + if (!packs.info[i].expired)
> + pack_name_concat_len += strlen(packs.info[i].pack_name) + 1;
> + }
...and here and elsewhere, we have to contend with the fact that
packs.info has pack_info that we don't want to write. I think it would
be slightly better to filter out the expired ones from packs.info, and
then when generating pack_perm, first memset it to 0xff. This way, we
wouldn't have to check expiry everywhere. But I don't feel too strongly
about this.
> int expire_midx_packs(const char *object_dir)
> {
> - return 0;
> + uint32_t i, *count, result = 0;
> + struct string_list packs_to_drop = STRING_LIST_INIT_DUP;
> + struct multi_pack_index *m = load_multi_pack_index(object_dir, 1);
> +
> + if (!m)
> + return 0;
> +
> + count = xcalloc(m->num_packs, sizeof(uint32_t));
> + for (i = 0; i < m->num_objects; i++) {
> + int pack_int_id = nth_midxed_pack_int_id(m, i);
> + count[pack_int_id]++;
> + }
> +
> + for (i = 0; i < m->num_packs; i++) {
> + char *pack_name;
> +
> + if (count[i])
> + continue;
> +
> + if (prepare_midx_pack(m, i))
> + continue;
> +
> + if (m->packs[i]->pack_keep)
> + continue;
> +
> + pack_name = xstrdup(m->packs[i]->pack_name);
> + close_pack(m->packs[i]);
> + FREE_AND_NULL(m->packs[i]);
> +
> + string_list_insert(&packs_to_drop, m->pack_names[i]);
> + unlink_pack_path(pack_name, 0);
> + free(pack_name);
> + }
> +
> + free(count);
> +
> + if (packs_to_drop.nr)
> + result = write_midx_internal(object_dir, m, &packs_to_drop);
> +
> + string_list_clear(&packs_to_drop, 0);
> + return result;
> }
This is as I expected - unlink all the files we don't want, and even
though much of the midx hasn't changed, we still need to write it
because it has a new list of packfiles.
> +test_expect_success 'expire removes unreferenced packs' '
> + (
> + cd dup &&
> + git pack-objects --revs .git/objects/pack/pack-combined <<-EOF &&
> + refs/heads/A
> + ^refs/heads/C
> + EOF
> + git multi-pack-index write &&
> + ls .git/objects/pack | grep -v -e pack-[AB] >expect &&
> + git multi-pack-index expire &&
> + ls .git/objects/pack >actual &&
> + test_cmp expect actual &&
> + ls .git/objects/pack/ | grep idx >expect-idx &&
> + test-tool read-midx .git/objects | grep idx >actual-midx &&
> + test_cmp expect-idx actual-midx
> + )
> +'
Maybe add a fsck at the end for sanity's sake. Also, I think that
preservation of .keep packfiles is an important feature, and maybe worth
a test.
