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cache-tree: prefetch in partial clone read-tree 

"git read-tree" checks the existence of the blobs referenced by the
given tree, but does not bulk prefetch them. Add a bulk prefetch.

The lack of prefetch here was noticed at $DAYJOB during a merge
involving some specific commits, but I couldn't find a minimal merge
that didn't also trigger the prefetch in check_updates() in
unpack-trees.c (and in all these cases, the lack of prefetch in
cache-tree.c didn't matter because all the relevant blobs would have
already been prefetched by then). This is why I used read-tree here to
exercise this code path.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jonathan Tan 2021-07-23 11:52:23 -07:00 committed by Junio C Hamano
parent b2896d2739
commit d3da223f22
2 changed files with 42 additions and 2 deletions
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11
cache-tree.c
View File

@ -237,6 +237,11 @@ int cache_tree_fully_valid(struct cache_tree *it)
return 1;
}
static int must_check_existence(const struct cache_entry *ce)
{
return !(has_promisor_remote() && ce_skip_worktree(ce));
}
static int update_one(struct cache_tree *it,
struct cache_entry **cache,
int entries,
@ -378,8 +383,7 @@ static int update_one(struct cache_tree *it,
}
ce_missing_ok = mode == S_IFGITLINK || missing_ok ||
(has_promisor_remote() &&
ce_skip_worktree(ce));
!must_check_existence(ce);
if (is_null_oid(oid) ||
(!ce_missing_ok && !has_object_file(oid))) {
strbuf_release(&buffer);
@ -466,6 +470,9 @@ int cache_tree_update(struct index_state *istate, int flags)
if (!istate->cache_tree)
istate->cache_tree = cache_tree();
if (!(flags & WRITE_TREE_MISSING_OK) && has_promisor_remote())
prefetch_cache_entries(istate, must_check_existence);
trace_performance_enter();
trace2_region_enter("cache_tree", "update", the_repository);
i = update_one(istate->cache_tree, istate->cache, istate->cache_nr,

33
t/t1022-read-tree-partial-clone.sh Executable file
View File

@ -0,0 +1,33 @@
#!/bin/sh
test_description='git read-tree in partial clones'
TEST_NO_CREATE_REPO=1
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
. ./test-lib.sh
test_expect_success 'read-tree in partial clone prefetches in one batch' '
test_when_finished "rm -rf server client trace" &&
git init server &&
echo foo >server/one &&
echo bar >server/two &&
git -C server add one two &&
git -C server commit -m "initial commit" &&
TREE=$(git -C server rev-parse HEAD^{tree}) &&
git -C server config uploadpack.allowfilter 1 &&
git -C server config uploadpack.allowanysha1inwant 1 &&
git clone --bare --filter=blob:none "file://$(pwd)/server" client &&
GIT_TRACE_PACKET="$(pwd)/trace" git -C client read-tree $TREE &&
# "done" marks the end of negotiation (once per fetch). Expect that
# only one fetch occurs.
grep "fetch> done" trace >donelines &&
test_line_count = 1 donelines
'
test_done