Re: [PATCH 2/2] odb/source-loose: fix existence checks for newly written objects

[Junio C Hamano <gitster@pobox.com>]

Patrick Steinhardt <ps@pks.im> writes:

> On Thu, Nov 05, 2026 at 02:43:14PM -0500, Jeff King wrote:
>> On Wed, Nov 04, 2026 at 01:16:35PM +0100, Patrick Steinhardt wrote:
>> ...
>> So I kind of wonder if prefetch_cache_entries(), along with any caller
>> doing an OBJECT_INFO_FOR_PREFETCH check, ought to omit the QUICK flag.
>> It would mean that the normal case of having missing partial objects
>> (about to be fetched) would cause us to re-scan the local pack list, but
>> that's not _that_ expensive, especially compared to the fetch we're
>> about to do.
>
> Yeah, that's a valid point. Honestly, by now I'm almost urged to just
> drop the QUICK flag altogther. It's a source of bugs, and the longer we
> look at it the more cases we find where the existing users thereof are
> buggy in specific edge cases. We just recently removed one user of
> QUICK, and this here is another dubious case. I wouldn't be surprised if
> we could find edge cases for the other, remaining users, as well.
> ...
>> > We could in theory fix this by flushing all the loose object caches
>> > again, like we used to do before 5946a564cdd. But that wouldn't address
>> > the root cause: the cache would still be stale unless somebody does a
>> > non-QUICK read for a missing object. Instead, fix the bug by updating
>> > the cache whenever we write a new loose object.

OK.  At least this change hides this specific failure mode.  Can we
include some documentation that we may want to rethink the "QUICK"
thing and audit its current uses (if we decide to keep it, that is)
and move on with this change?


 odb.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git c/odb.h w/odb.h
index dd85b880a7..61ff443d46 100644
--- c/odb.h
+++ w/odb.h
@@ -386,6 +386,9 @@ enum object_info_flags {
 	/*
 	 * This is meant for bulk prefetching of missing blobs in a partial
 	 * clone. Implies OBJECT_INFO_SKIP_FETCH_OBJECT and OBJECT_INFO_QUICK.
+	 *
+	 * NEEDSWORK: rethink if QUICK is desired in this context.
+	 * cf. <au23Hvzp09yrym9s@pks.im>
 	 */
 	OBJECT_INFO_FOR_PREFETCH = (OBJECT_INFO_SKIP_FETCH_OBJECT | OBJECT_INFO_QUICK),
 };