[PATCH 2/3] index-pack: no blobs during outgoing link check
- From
- Jonathan Tan <jonathantanmy@google.com>
- Date
- Dec 2, 2024, 20:18 UTC
- Message-ID
- <300f53b8e39fa1dd55f65924d20f8abd22cbbfc9.1733170252.git.jonathantanmy@google.com>
- In-Reply-To
- <cover.1733170252.git.jonathantanmy@google.com>
As a follow-up to the parent of this commit, it was found that not checking for the existence of blobs linked from trees sped up the fetch from 24m47.815s to 2m2.127s. Teach Git to do that.
The benefit of doing this is as above (fetch speedup), but the drawback is that if the packfile to be indexed references a local blob directly (that is, not through a local tree), that local blob is in danger of being garbage collected. Such a situation may arise if we push local commits, including one with a change to a blob in the root tree, and then the server incorporates them into its main branch through a "rebase" or "squash" merge strategy, and then we fetch the new main branch from the server.
This situation has not been observed yet - we have only noticed missing commits, not missing trees or blobs. (In fact, if it were believed that only missing commits are problematic, one could argue that we should also exclude trees during the outgoing link check; but it is safer to include them.)
Due to the rarity of the situation (it has not been observed to happen in real life), and because the "penalty" in such a situation is merely to refetch the missing blob when it's needed, the tradeoff seems worth it.
(Blobs may also be linked from tag objects, but it is impossible to know the type of an object linked from a tag object without looking it up in the object database, so the code for that is untouched.)
Signed-off-by: Jonathan Tan <jonathantanmy@google.com> --- builtin/index-pack.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/builtin/index-pack.c b/builtin/index-pack.c index 8e7d14c17e..58d24540dc 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -830,8 +830,10 @@ static void do_record_outgoing_links(struct object *obj) * verified, so do not print any here. */ return; - while (tree_entry_gently(&desc, &entry)) - record_outgoing_link(&entry.oid); + while (tree_entry_gently(&desc, &entry)) { + if (S_ISDIR(entry.mode)) + record_outgoing_link(&entry.oid); + } } else if (obj->type == OBJ_COMMIT) { struct commit *commit = (struct commit *) obj; struct commit_list *parents = commit->parents;
-- 2.47.0.338.g60cca15819-goog