[PATCH 4/9] odb: lift object existence check out of the "loose" backend

From: Patrick Steinhardt <ps@pks.im>
Date: Jul 17, 2026, 09:32 UTC
Message-ID: <20260717-pks-odb-move-loose-object-writing-v1-4-46446a3cb5b7@pks.im>
In-Reply-To: <20260717-pks-odb-move-loose-object-writing-v1-0-46446a3cb5b7@pks.im>

Before writing a new loose object we first check whether the object already exists in any of the sources attached to the object database. This results in a couple of issues:

  - We have a layering violation, where the source needs to be aware of
    objects stored in any of the other sources.

  - Every backend would have to reimplement this check, which feels
    somewhat pointless.

  - It is not possible to easily write an object into a source in case
    the same object already exists in another source.

Refactor the code and lift up the object existence check from the "loose" backend into the generic ODB layer. No callers need adjustment as none of them write via a specific source, but via the ODB layer.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 odb.c              | 7 +++++++
 odb/source-loose.c | 8 ++------
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/odb.c b/odb.c
index 4adbdf8a64..bfeca76f4e 100644
--- a/odb.c
+++ b/odb.c
@@ -997,6 +997,13 @@ int odb_write_object_ext(struct object_database *odb,
 
 	hash_object_file(odb->repo->hash_algo, buf, len, type, oid);
 
+	/*
+	 * We can skip the write in case we already have the object available.
+	 * In that case, we only freshen its mtime.
+	 */
+	if (odb_freshen_object(odb, oid))
+		return 0;
+
 	if (compat) {
 		const struct git_hash_algo *algo = odb->repo->hash_algo;
 
diff --git a/odb/source-loose.c b/odb/source-loose.c
index d4715da6d1..04af1a54a3 100644
--- a/odb/source-loose.c
+++ b/odb/source-loose.c
@@ -595,16 +595,12 @@ static int odb_source_loose_write_object(struct odb_source *source,
 
 	hdrlen = format_object_header(hdr, sizeof(hdr), type, len);
 
-	/*
-	 * Normally if we have it in the pack then we do not bother writing
-	 * it out into .git/objects/??/?{38} file.
-	 */
-	if (odb_freshen_object(source->odb, oid))
-		return 0;
 	if (write_loose_object(loose, oid, hdr, hdrlen, buf, len, 0, flags))
 		return -1;
+
 	if (compat_oid)
 		return repo_add_loose_object_map(loose, oid, compat_oid);
+
 	return 0;
 }

-- 
2.55.0.407.g700c83d4f3.dirty