git/sparse-index.c
Derrick Stolee 71f82d032f sparse-index: expand_to_path()
Some users of the index API have a specific path they are looking for,
but choose to use index_file_exists() to rely on the name-hash hashtable
instead of doing binary search with index_name_pos(). These users only
need to know a yes/no answer, not a position within the cache array.

When the index is sparse, the name-hash hash table does not contain the
full list of paths within sparse directories. It _does_ contain the
directory names for the sparse-directory entries.

Create a helper function, expand_to_path(), for intended use with the
name-hash hashtable functions. The integration with name-hash.c will
follow in a later change.

The solution here is to use ensure_full_index() when we determine that
the requested path is within a sparse directory entry. This will
populate the name-hash hashtable as the index is recomputed from
scratch.

There may be cases where the caller is trying to find an untracked path
that is not in the index but also is not within a sparse directory
entry. We want to minimize the overhead for these requests. If we used
index_name_pos() to find the insertion order of the path, then we could
determine from that position if a sparse-directory exists. (In fact,
just calling index_name_pos() in that case would lead to expanding the
index to a full index.) However, this takes O(log N) time where N is the
number of cache entries.

To keep the performance of this call based mostly on the input string,
use index_file_exists() to look for the ancestors of the path. Using the
heuristic that a sparse directory is likely to have a small number of
parent directories, we start from the bottom and build up. Use a string
buffer to allow mutating the path name to terminate after each slash for
each hashset test.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-04-14 13:47:54 -07:00

359 lines
8.7 KiB
C

#include "cache.h"
#include "repository.h"
#include "sparse-index.h"
#include "tree.h"
#include "pathspec.h"
#include "trace2.h"
#include "cache-tree.h"
#include "config.h"
#include "dir.h"
#include "fsmonitor.h"
static struct cache_entry *construct_sparse_dir_entry(
struct index_state *istate,
const char *sparse_dir,
struct cache_tree *tree)
{
struct cache_entry *de;
de = make_cache_entry(istate, S_IFDIR, &tree->oid, sparse_dir, 0, 0);
de->ce_flags |= CE_SKIP_WORKTREE;
return de;
}
/*
* Returns the number of entries "inserted" into the index.
*/
static int convert_to_sparse_rec(struct index_state *istate,
int num_converted,
int start, int end,
const char *ct_path, size_t ct_pathlen,
struct cache_tree *ct)
{
int i, can_convert = 1;
int start_converted = num_converted;
enum pattern_match_result match;
int dtype;
struct strbuf child_path = STRBUF_INIT;
struct pattern_list *pl = istate->sparse_checkout_patterns;
/*
* Is the current path outside of the sparse cone?
* Then check if the region can be replaced by a sparse
* directory entry (everything is sparse and merged).
*/
match = path_matches_pattern_list(ct_path, ct_pathlen,
NULL, &dtype, pl, istate);
if (match != NOT_MATCHED)
can_convert = 0;
for (i = start; can_convert && i < end; i++) {
struct cache_entry *ce = istate->cache[i];
if (ce_stage(ce) ||
S_ISGITLINK(ce->ce_mode) ||
!(ce->ce_flags & CE_SKIP_WORKTREE))
can_convert = 0;
}
if (can_convert) {
struct cache_entry *se;
se = construct_sparse_dir_entry(istate, ct_path, ct);
istate->cache[num_converted++] = se;
return 1;
}
for (i = start; i < end; ) {
int count, span, pos = -1;
const char *base, *slash;
struct cache_entry *ce = istate->cache[i];
/*
* Detect if this is a normal entry outside of any subtree
* entry.
*/
base = ce->name + ct_pathlen;
slash = strchr(base, '/');
if (slash)
pos = cache_tree_subtree_pos(ct, base, slash - base);
if (pos < 0) {
istate->cache[num_converted++] = ce;
i++;
continue;
}
strbuf_setlen(&child_path, 0);
strbuf_add(&child_path, ce->name, slash - ce->name + 1);
span = ct->down[pos]->cache_tree->entry_count;
count = convert_to_sparse_rec(istate,
num_converted, i, i + span,
child_path.buf, child_path.len,
ct->down[pos]->cache_tree);
num_converted += count;
i += span;
}
strbuf_release(&child_path);
return num_converted - start_converted;
}
static int set_index_sparse_config(struct repository *repo, int enable)
{
int res;
char *config_path = repo_git_path(repo, "config.worktree");
res = git_config_set_in_file_gently(config_path,
"index.sparse",
enable ? "true" : NULL);
free(config_path);
prepare_repo_settings(repo);
repo->settings.sparse_index = 1;
return res;
}
int set_sparse_index_config(struct repository *repo, int enable)
{
int res = set_index_sparse_config(repo, enable);
prepare_repo_settings(repo);
repo->settings.sparse_index = enable;
return res;
}
int convert_to_sparse(struct index_state *istate)
{
int test_env;
if (istate->split_index || istate->sparse_index ||
!core_apply_sparse_checkout || !core_sparse_checkout_cone)
return 0;
if (!istate->repo)
istate->repo = the_repository;
/*
* The GIT_TEST_SPARSE_INDEX environment variable triggers the
* index.sparse config variable to be on.
*/
test_env = git_env_bool("GIT_TEST_SPARSE_INDEX", -1);
if (test_env >= 0)
set_sparse_index_config(istate->repo, test_env);
/*
* Only convert to sparse if index.sparse is set.
*/
prepare_repo_settings(istate->repo);
if (!istate->repo->settings.sparse_index)
return 0;
if (!istate->sparse_checkout_patterns) {
istate->sparse_checkout_patterns = xcalloc(1, sizeof(struct pattern_list));
if (get_sparse_checkout_patterns(istate->sparse_checkout_patterns) < 0)
return 0;
}
if (!istate->sparse_checkout_patterns->use_cone_patterns) {
warning(_("attempting to use sparse-index without cone mode"));
return -1;
}
if (cache_tree_update(istate, 0)) {
warning(_("unable to update cache-tree, staying full"));
return -1;
}
remove_fsmonitor(istate);
trace2_region_enter("index", "convert_to_sparse", istate->repo);
istate->cache_nr = convert_to_sparse_rec(istate,
0, 0, istate->cache_nr,
"", 0, istate->cache_tree);
/* Clear and recompute the cache-tree */
cache_tree_free(&istate->cache_tree);
cache_tree_update(istate, 0);
istate->sparse_index = 1;
trace2_region_leave("index", "convert_to_sparse", istate->repo);
return 0;
}
static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
{
ALLOC_GROW(istate->cache, nr + 1, istate->cache_alloc);
istate->cache[nr] = ce;
add_name_hash(istate, ce);
}
static int add_path_to_index(const struct object_id *oid,
struct strbuf *base, const char *path,
unsigned int mode, void *context)
{
struct index_state *istate = (struct index_state *)context;
struct cache_entry *ce;
size_t len = base->len;
if (S_ISDIR(mode))
return READ_TREE_RECURSIVE;
strbuf_addstr(base, path);
ce = make_cache_entry(istate, mode, oid, base->buf, 0, 0);
ce->ce_flags |= CE_SKIP_WORKTREE;
set_index_entry(istate, istate->cache_nr++, ce);
strbuf_setlen(base, len);
return 0;
}
void ensure_full_index(struct index_state *istate)
{
int i;
struct index_state *full;
struct strbuf base = STRBUF_INIT;
if (!istate || !istate->sparse_index)
return;
if (!istate->repo)
istate->repo = the_repository;
trace2_region_enter("index", "ensure_full_index", istate->repo);
/* initialize basics of new index */
full = xcalloc(1, sizeof(struct index_state));
memcpy(full, istate, sizeof(struct index_state));
/* then change the necessary things */
full->sparse_index = 0;
full->cache_alloc = (3 * istate->cache_alloc) / 2;
full->cache_nr = 0;
ALLOC_ARRAY(full->cache, full->cache_alloc);
for (i = 0; i < istate->cache_nr; i++) {
struct cache_entry *ce = istate->cache[i];
struct tree *tree;
struct pathspec ps;
if (!S_ISSPARSEDIR(ce->ce_mode)) {
set_index_entry(full, full->cache_nr++, ce);
continue;
}
if (!(ce->ce_flags & CE_SKIP_WORKTREE))
warning(_("index entry is a directory, but not sparse (%08x)"),
ce->ce_flags);
/* recursively walk into cd->name */
tree = lookup_tree(istate->repo, &ce->oid);
memset(&ps, 0, sizeof(ps));
ps.recursive = 1;
ps.has_wildcard = 1;
ps.max_depth = -1;
strbuf_setlen(&base, 0);
strbuf_add(&base, ce->name, strlen(ce->name));
read_tree_at(istate->repo, tree, &base, &ps,
add_path_to_index, full);
/* free directory entries. full entries are re-used */
discard_cache_entry(ce);
}
/* Copy back into original index. */
memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
istate->sparse_index = 0;
free(istate->cache);
istate->cache = full->cache;
istate->cache_nr = full->cache_nr;
istate->cache_alloc = full->cache_alloc;
strbuf_release(&base);
free(full);
/* Clear and recompute the cache-tree */
cache_tree_free(&istate->cache_tree);
cache_tree_update(istate, 0);
trace2_region_leave("index", "ensure_full_index", istate->repo);
}
/*
* This static global helps avoid infinite recursion between
* expand_to_path() and index_file_exists().
*/
static int in_expand_to_path = 0;
void expand_to_path(struct index_state *istate,
const char *path, size_t pathlen, int icase)
{
struct strbuf path_mutable = STRBUF_INIT;
size_t substr_len;
/* prevent extra recursion */
if (in_expand_to_path)
return;
if (!istate || !istate->sparse_index)
return;
if (!istate->repo)
istate->repo = the_repository;
in_expand_to_path = 1;
/*
* We only need to actually expand a region if the
* following are both true:
*
* 1. 'path' is not already in the index.
* 2. Some parent directory of 'path' is a sparse directory.
*/
if (index_file_exists(istate, path, pathlen, icase))
goto cleanup;
strbuf_add(&path_mutable, path, pathlen);
strbuf_addch(&path_mutable, '/');
/* Check the name hash for all parent directories */
substr_len = 0;
while (substr_len < pathlen) {
char temp;
char *replace = strchr(path_mutable.buf + substr_len, '/');
if (!replace)
break;
/* replace the character _after_ the slash */
replace++;
temp = *replace;
*replace = '\0';
if (index_file_exists(istate, path_mutable.buf,
path_mutable.len, icase)) {
/*
* We found a parent directory in the name-hash
* hashtable, because only sparse directory entries
* have a trailing '/' character. Since "path" wasn't
* in the index, perhaps it exists within this
* sparse-directory. Expand accordingly.
*/
ensure_full_index(istate);
break;
}
*replace = temp;
substr_len = replace - path_mutable.buf;
}
cleanup:
strbuf_release(&path_mutable);
in_expand_to_path = 0;
}