odb/source-packed: improve lookup when enumerating objects

When iterating through objects of a packed source that have a specific
prefix we do so via two different methods:

  - When a multi-pack index is available we use that one to efficiently
    loop through all objects.

  - We then loop through all packfiles that aren't covered by a
    multi-pack index.

Regardless of which mechanism we use, we then iterate through all the
objects indexed by the respective data structure. Curiously though,
while we use the indices for enumerating the objects, we completely
ignore it for the actual object lookup. Instead, we call into the
generic `odb_source_read_object_info()` function, which will itself
consult the indices to figure out where the object in question even
lives.

This has two consequences:

  - It's inefficient, as we basically have to figure out the position of
    the object a second time.

  - It's subtly wrong, as it may now happen that a specific object will
    be looked up via a different pack in case it exists multiple times.
    This is unlikely to have any real-world consequences, but it's still
    the wrong thing to do.

Fix the issue by using `packed_object_info()` directly. While at it,
rename the `store` variable to `source`.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/odb/source-packed.c b/odb/source-packed.c
index 0edea5356d821072af791445fc2975d3771e2ba8..9cfa02b7a2e53ef514cc50e90070b5be7582eff5 100644 (file)
--- a/odb/source-packed.c
+++ b/odb/source-packed.c
@@ -143,7 +143,7 @@ static bool should_exclude_pack(struct packed_git *p, enum odb_for_each_object_f
 }
 
 static int for_each_prefixed_object_in_midx(
-       struct odb_source_packed *store,
+       struct odb_source_packed *source,
        struct multi_pack_index *m,
        const struct odb_for_each_object_options *opts,
        struct odb_source_packed_for_each_object_wrapper_data *data)
@@ -170,6 +170,7 @@ static int for_each_prefixed_object_in_midx(
                 */
                for (i = first; i < num; i++) {
                        const struct object_id *current = NULL;
+                       struct packed_git *pack;
                        struct object_id oid;
 
                        current = nth_midxed_object_oid(&oid, m, i);
@@ -177,9 +178,8 @@ static int for_each_prefixed_object_in_midx(
                        if (!match_hash(len, opts->prefix->hash, current->hash))
                                break;
 
-                       if (opts->flags) {
+                       if (opts->flags || data->request) {
                                uint32_t pack_id = nth_midxed_pack_int_id(m, i);
-                               struct packed_git *pack;
 
                                if (prepare_midx_pack(m, pack_id)) {
                                        pack_errors = true;
@@ -193,9 +193,9 @@ static int for_each_prefixed_object_in_midx(
 
                        if (data->request) {
                                struct object_info oi = *data->request;
+                               off_t offset = nth_midxed_offset(m, i);
 
-                               ret = odb_source_read_object_info(&store->base, current,
-                                                                 &oi, 0);
+                               ret = packed_object_info(source, pack, offset, &oi);
                                if (ret)
                                        goto out;
 
@@ -219,7 +219,7 @@ out:
 }
 
 static int for_each_prefixed_object_in_pack(
-       struct odb_source_packed *store,
+       struct odb_source_packed *source,
        struct packed_git *p,
        const struct odb_for_each_object_options *opts,
        struct odb_source_packed_for_each_object_wrapper_data *data)
@@ -246,8 +246,9 @@ static int for_each_prefixed_object_in_pack(
 
                if (data->request) {
                        struct object_info oi = *data->request;
+                       off_t offset = nth_packed_object_offset(p, i);
 
-                       ret = odb_source_read_object_info(&store->base, &oid, &oi, 0);
+                       ret = packed_object_info(source, p, offset, &oi);
                        if (ret)
                                goto out;