@matheusbsbs / matheus-bagliano / commits / b31f2aac56

midx: teach `midx_preferred_pack()` about incremental MIDXs

The function `midx_preferred_pack()` is used to determine the identity of the preferred pack, which is the identity of a unique pack within the MIDX which is used as a tie-breaker when selecting from which pack to represent an object that appears in multiple packs within the MIDX. Historically we have said that the MIDX's preferred pack has the unique property that all objects from that pack are represented in the MIDX. But that isn't quite true: a more precise statement would be that all objects from that pack *which appear in the MIDX* are selected from that pack. This helps us extend the concept of preferred packs across a MIDX chain, where some object(s) in the preferred pack may appear in other packs in an earlier MIDX layer, in which case those object(s) will not appear in a subsequent MIDX layer from either the preferred pack or any other pack. Extend the concept of preferred packs by using the pack which represents the object at the first position in MIDX pseudo-pack order belonging to the current MIDX layer (i.e., at position 'm->num_objects_in_base'). Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Taylor Blau committed Aug 6, 2024 at 11:37 UTC b31f2aac561d9a819dc4f4ed54fafdeb3041bccd

1 file changed +5 -2

midx.c

+5 -2

@@ -501,13 +501,16 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)

501 int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id)

502 {

503 if (m->preferred_pack_idx == -1) {

504 + uint32_t midx_pos;

505 if (load_midx_revindex(m) < 0) {

506 m->preferred_pack_idx = -2;

507 return -1;

508 }

509

509 - m->preferred_pack_idx =

510 - nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));

510 + midx_pos = pack_pos_to_midx(m, m->num_objects_in_base);

511 +

512 + m->preferred_pack_idx = nth_midxed_pack_int_id(m, midx_pos);

513 +

514 } else if (m->preferred_pack_idx == -2)

515 return -1; /* no revindex */

516