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diff: restrict when prefetching occurs

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Commit 7fbbcb21b1 ("diff: batch fetching of missing blobs", 2019-04-08)
optimized "diff" by prefetching blobs in a partial clone, but there are
some cases wherein blobs do not need to be prefetched. In these cases,
any command that uses the diff machinery will unnecessarily fetch blobs.

diffcore_std() may read blobs when it calls the following functions:
 (1) diffcore_skip_stat_unmatch() (controlled by the config variable
     diff.autorefreshindex)
 (2) diffcore_break() and diffcore_merge_broken() (for break-rewrite
     detection)
 (3) diffcore_rename() (for rename detection)
 (4) diffcore_pickaxe() (for detecting addition/deletion of specified
     string)

Instead of always prefetching blobs, teach diffcore_skip_stat_unmatch(),
diffcore_break(), and diffcore_rename() to prefetch blobs upon the first
read of a missing object. This covers (1), (2), and (3): to cover the
rest, teach diffcore_std() to prefetch if the output type is one that
includes blob data (and hence blob data will be required later anyway),
or if it knows that (4) will be run.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jonathan Tan
2020-04-07 15:11:43 -07:00
committed by Junio C Hamano
parent c14b6f83ec
commit 95acf11a3d
5 changed files with 181 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

73
diff.c
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@ -4034,10 +4034,18 @@ int diff_populate_filespec(struct repository *r,
*/
info.contentp = &s->data;
if (options && options->missing_object_cb) {
if (!oid_object_info_extended(r, &s->oid, &info,
OBJECT_INFO_LOOKUP_REPLACE |
OBJECT_INFO_SKIP_FETCH_OBJECT))
goto object_read;
options->missing_object_cb(options->missing_object_data);
}
if (oid_object_info_extended(r, &s->oid, &info,
OBJECT_INFO_LOOKUP_REPLACE))
die("unable to read %s", oid_to_hex(&s->oid));
object_read:
if (size_only || check_binary) {
if (size_only)
return 0;
@ -6444,6 +6452,8 @@ static int diff_filespec_check_stat_unmatch(struct repository *r,
{
struct diff_populate_filespec_options dpf_options = {
.check_size_only = 1,
.missing_object_cb = diff_queued_diff_prefetch,
.missing_object_data = r,
};
if (p->done_skip_stat_unmatch)
@ -6520,9 +6530,9 @@ void diffcore_fix_diff_index(void)
QSORT(q->queue, q->nr, diffnamecmp);
}
static void add_if_missing(struct repository *r,
struct oid_array *to_fetch,
const struct diff_filespec *filespec)
void diff_add_if_missing(struct repository *r,
struct oid_array *to_fetch,
const struct diff_filespec *filespec)
{
if (filespec && filespec->oid_valid &&
!S_ISGITLINK(filespec->mode) &&
@ -6531,28 +6541,47 @@ static void add_if_missing(struct repository *r,
oid_array_append(to_fetch, &filespec->oid);
}
void diff_queued_diff_prefetch(void *repository)
{
struct repository *repo = repository;
int i;
struct diff_queue_struct *q = &diff_queued_diff;
struct oid_array to_fetch = OID_ARRAY_INIT;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
diff_add_if_missing(repo, &to_fetch, p->one);
diff_add_if_missing(repo, &to_fetch, p->two);
}
/*
* NEEDSWORK: Consider deduplicating the OIDs sent.
*/
promisor_remote_get_direct(repo, to_fetch.oid, to_fetch.nr);
oid_array_clear(&to_fetch);
}
void diffcore_std(struct diff_options *options)
{
if (options->repo == the_repository && has_promisor_remote()) {
/*
* Prefetch the diff pairs that are about to be flushed.
*/
int i;
struct diff_queue_struct *q = &diff_queued_diff;
struct oid_array to_fetch = OID_ARRAY_INIT;
int output_formats_to_prefetch = DIFF_FORMAT_DIFFSTAT |
DIFF_FORMAT_NUMSTAT |
DIFF_FORMAT_PATCH |
DIFF_FORMAT_SHORTSTAT |
DIFF_FORMAT_DIRSTAT;
for (i = 0; i < q->nr; i++) {
struct diff_filepair *p = q->queue[i];
add_if_missing(options->repo, &to_fetch, p->one);
add_if_missing(options->repo, &to_fetch, p->two);
}
/*
* NEEDSWORK: Consider deduplicating the OIDs sent.
*/
promisor_remote_get_direct(options->repo,
to_fetch.oid, to_fetch.nr);
oid_array_clear(&to_fetch);
}
/*
* Check if the user requested a blob-data-requiring diff output and/or
* break-rewrite detection (which requires blob data). If yes, prefetch
* the diff pairs.
*
* If no prefetching occurs, diffcore_rename() will prefetch if it
* decides that it needs inexact rename detection.
*/
if (options->repo == the_repository && has_promisor_remote() &&
(options->output_format & output_formats_to_prefetch ||
options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK))
diff_queued_diff_prefetch(options->repo);
/* NOTE please keep the following in sync with diff_tree_combined() */
if (options->skip_stat_unmatch)