git/midx.h
Taylor Blau fcb2205b77 midx: implement support for writing incremental MIDX chains
Now that the rest of the MIDX subsystem and relevant callers have been
updated to learn about how to read and process incremental MIDX chains,
let's finally update the implementation in `write_midx_internal()` to be
able to write incremental MIDX chains.

This new feature is available behind the `--incremental` option for the
`multi-pack-index` builtin, like so:

    $ git multi-pack-index write --incremental

The implementation for doing so is relatively straightforward, and boils
down to a handful of different kinds of changes implemented in this
patch:

  - The `compute_sorted_entries()` function is taught to reject objects
    which appear in any existing MIDX layer.

  - Functions like `write_midx_revindex()` are adjusted to write
    pack_order values which are offset by the number of objects in the
    base MIDX layer.

  - The end of `write_midx_internal()` is adjusted to move
    non-incremental MIDX files when necessary (i.e. when creating an
    incremental chain with an existing non-incremental MIDX in the
    repository).

There are a handful of other changes that are introduced, like new
functions to clear incremental MIDX files that are unrelated to the
current chain (using the same "keep_hash" mechanism as in the
non-incremental case).

The tests explicitly exercising the new incremental MIDX feature are
relatively limited for two reasons:

  1. Most of the "interesting" behavior is already thoroughly covered in
     t5319-multi-pack-index.sh, which handles the core logic of reading
     objects through a MIDX.

     The new tests in t5334-incremental-multi-pack-index.sh are mostly
     focused on creating and destroying incremental MIDXs, as well as
     stitching their results together across layers.

  2. A new GIT_TEST environment variable is added called
     "GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL", which modifies the
     entire test suite to write incremental MIDXs after repacking when
     combined with the "GIT_TEST_MULTI_PACK_INDEX" variable.

     This exercises the long tail of other interesting behavior that is
     defined implicitly throughout the rest of the CI suite. It is
     likewise added to the linux-TEST-vars job.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-08-06 12:01:39 -07:00

140 lines
4.9 KiB
C

#ifndef MIDX_H
#define MIDX_H
#include "string-list.h"
struct object_id;
struct pack_entry;
struct repository;
struct bitmapped_pack;
#define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
#define MIDX_VERSION 1
#define MIDX_BYTE_FILE_VERSION 4
#define MIDX_BYTE_HASH_VERSION 5
#define MIDX_BYTE_NUM_CHUNKS 6
#define MIDX_BYTE_NUM_PACKS 8
#define MIDX_HEADER_SIZE 12
#define MIDX_CHUNK_ALIGNMENT 4
#define MIDX_CHUNKID_PACKNAMES 0x504e414d /* "PNAM" */
#define MIDX_CHUNKID_BITMAPPEDPACKS 0x42544d50 /* "BTMP" */
#define MIDX_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
#define MIDX_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
#define MIDX_CHUNKID_OBJECTOFFSETS 0x4f4f4646 /* "OOFF" */
#define MIDX_CHUNKID_LARGEOFFSETS 0x4c4f4646 /* "LOFF" */
#define MIDX_CHUNKID_REVINDEX 0x52494458 /* "RIDX" */
#define MIDX_CHUNKID_BASE 0x42415345 /* "BASE" */
#define MIDX_CHUNK_OFFSET_WIDTH (2 * sizeof(uint32_t))
#define MIDX_LARGE_OFFSET_NEEDED 0x80000000
#define GIT_TEST_MULTI_PACK_INDEX "GIT_TEST_MULTI_PACK_INDEX"
#define GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL \
"GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL"
struct multi_pack_index {
struct multi_pack_index *next;
const unsigned char *data;
size_t data_len;
const uint32_t *revindex_data;
const uint32_t *revindex_map;
size_t revindex_len;
uint32_t signature;
unsigned char version;
unsigned char hash_len;
unsigned char num_chunks;
uint32_t num_packs;
uint32_t num_objects;
int preferred_pack_idx;
int local;
int has_chain;
const unsigned char *chunk_pack_names;
size_t chunk_pack_names_len;
const uint32_t *chunk_bitmapped_packs;
size_t chunk_bitmapped_packs_len;
const uint32_t *chunk_oid_fanout;
const unsigned char *chunk_oid_lookup;
const unsigned char *chunk_object_offsets;
const unsigned char *chunk_large_offsets;
size_t chunk_large_offsets_len;
const unsigned char *chunk_revindex;
size_t chunk_revindex_len;
struct multi_pack_index *base_midx;
uint32_t num_objects_in_base;
uint32_t num_packs_in_base;
const char **pack_names;
struct packed_git **packs;
char object_dir[FLEX_ARRAY];
};
#define MIDX_PROGRESS (1 << 0)
#define MIDX_WRITE_REV_INDEX (1 << 1)
#define MIDX_WRITE_BITMAP (1 << 2)
#define MIDX_WRITE_BITMAP_HASH_CACHE (1 << 3)
#define MIDX_WRITE_BITMAP_LOOKUP_TABLE (1 << 4)
#define MIDX_WRITE_INCREMENTAL (1 << 5)
#define MIDX_EXT_REV "rev"
#define MIDX_EXT_BITMAP "bitmap"
#define MIDX_EXT_MIDX "midx"
const unsigned char *get_midx_checksum(struct multi_pack_index *m);
void get_midx_filename(struct strbuf *out, const char *object_dir);
void get_midx_filename_ext(struct strbuf *out, const char *object_dir,
const unsigned char *hash, const char *ext);
void get_midx_chain_dirname(struct strbuf *buf, const char *object_dir);
void get_midx_chain_filename(struct strbuf *buf, const char *object_dir);
void get_split_midx_filename_ext(struct strbuf *buf, const char *object_dir,
const unsigned char *hash, const char *ext);
struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local);
int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);
struct packed_git *nth_midxed_pack(struct multi_pack_index *m,
uint32_t pack_int_id);
int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
struct bitmapped_pack *bp, uint32_t pack_int_id);
int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
uint32_t *result);
int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m,
uint32_t *result);
int midx_has_oid(struct multi_pack_index *m, const struct object_id *oid);
off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos);
uint32_t nth_midxed_pack_int_id(struct multi_pack_index *m, uint32_t pos);
struct object_id *nth_midxed_object_oid(struct object_id *oid,
struct multi_pack_index *m,
uint32_t n);
int fill_midx_entry(struct repository *r, const struct object_id *oid, struct pack_entry *e, struct multi_pack_index *m);
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);
int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local);
/*
* Variant of write_midx_file which writes a MIDX containing only the packs
* specified in packs_to_include.
*/
int write_midx_file(const char *object_dir,
const char *preferred_pack_name,
const char *refs_snapshot,
unsigned flags);
int write_midx_file_only(const char *object_dir,
struct string_list *packs_to_include,
const char *preferred_pack_name,
const char *refs_snapshot,
unsigned flags);
void clear_midx_file(struct repository *r);
int verify_midx_file(struct repository *r, const char *object_dir, unsigned flags);
int expire_midx_packs(struct repository *r, const char *object_dir, unsigned flags);
int midx_repack(struct repository *r, const char *object_dir, size_t batch_size, unsigned flags);
void close_midx(struct multi_pack_index *m);
#endif