From b31f2aac561d9a819dc4f4ed54fafdeb3041bccd Mon Sep 17 00:00:00 2001 From: Taylor Blau Date: Tue, 6 Aug 2024 11:37:49 -0400 Subject: [PATCH] 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 Signed-off-by: Junio C Hamano --- midx.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/midx.c b/midx.c index 454c27b673..918349576f 100644 --- a/midx.c +++ b/midx.c @@ -501,13 +501,16 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name) int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id) { if (m->preferred_pack_idx == -1) { + uint32_t midx_pos; if (load_midx_revindex(m) < 0) { m->preferred_pack_idx = -2; return -1; } - m->preferred_pack_idx = - nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0)); + midx_pos = pack_pos_to_midx(m, m->num_objects_in_base); + + m->preferred_pack_idx = nth_midxed_pack_int_id(m, midx_pos); + } else if (m->preferred_pack_idx == -2) return -1; /* no revindex */