git@vger.kernel.org mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Derrick Stolee <stolee@gmail.com>
To: Jonathan Tan <jonathantanmy@google.com>, git@vger.kernel.org
Subject: Re: [PATCH] cache-tree: do not lazy-fetch merge tree
Date: Tue, 3 Sep 2019 21:37:06 -0400	[thread overview]
Message-ID: <69f2b069-3e11-4a2e-9b81-bde18c463d8c@gmail.com> (raw)
In-Reply-To: <20190903194247.217964-1-jonathantanmy@google.com>

On 9/3/2019 3:42 PM, Jonathan Tan wrote:
> When cherry-picking (for example), new trees may be constructed. During
> this process, Git checks whether these trees exist. However, in a
> partial clone, this causes a lazy fetch to occur, which is both
> unnecessary (because Git has already constructed this tree as part of
> the cherry-picking process) and likely to fail (because the remote
> probably doesn't have this tree).

If we have constructed the object already, then why do we not see it
and avoid fetching it? This must be a slightly strange timing issue
with objects being flushed to disk or added to the object cache.

One approach is to find all of these has_object_file() calls that should
really be one with OBJECT_INFO_SKIP_FETCH_OBJECT. Another would be to
find out why has_object_file() isn't seeing the object we constructed.

> Do not lazy fetch in this situation.
I agree that the patch has this effect.
 
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---
> Another partial clone bug.
> 
> This raises the issue that failed fetches are currently fatal - if they
> weren't fatal, this cherry-pick would have worked (except with some
> delay as the fetch is attempted, and with a warning message about the
> fetch failing). My personal inclination right now is to leave things as
> it is (fatal failed fetches), but I'm open to other opinions.
> ---
>  cache-tree.c             |  2 +-
>  t/t0410-partial-clone.sh | 14 ++++++++++++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/cache-tree.c b/cache-tree.c
> index c22161f987..9e596893bc 100644
> --- a/cache-tree.c
> +++ b/cache-tree.c
> @@ -407,7 +407,7 @@ static int update_one(struct cache_tree *it,
>  	if (repair) {
>  		struct object_id oid;
>  		hash_object_file(buffer.buf, buffer.len, tree_type, &oid);
> -		if (has_object_file(&oid))
> +		if (has_object_file_with_flags(&oid, OBJECT_INFO_SKIP_FETCH_OBJECT))
>  			oidcpy(&it->oid, &oid);
>  		else
>  			to_invalidate = 1;
> diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
> index 6415063980..3e434b6a81 100755
> --- a/t/t0410-partial-clone.sh
> +++ b/t/t0410-partial-clone.sh
> @@ -492,6 +492,20 @@ test_expect_success 'gc stops traversal when a missing but promised object is re
>  	! grep "$TREE_HASH" out
>  '
>  
> +test_expect_success 'do not fetch when checking existence of tree we construct ourselves' '
> +	rm -rf repo &&
> +	test_create_repo repo &&
> +	test_commit -C repo base &&
> +	test_commit -C repo side1 &&
> +	git -C repo checkout base &&
> +	test_commit -C repo side2 &&
> +
> +	git -C repo config core.repositoryformatversion 1 &&
> +	git -C repo config extensions.partialclone "arbitrary string" &&
> +
> +	git -C repo cherry-pick side1
> +'
> +

I appreciate this test!

Thanks,
-Stolee

  reply	other threads:[~2019-09-04  1:37 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-03 19:42 [PATCH] cache-tree: do not lazy-fetch merge tree Jonathan Tan
2019-09-04  1:37 ` Derrick Stolee [this message]
2019-09-04 22:35   ` Jonathan Tan
2019-09-04 23:35     ` Junio C Hamano
2019-09-09 19:01 ` [PATCH v2] " Jonathan Tan
2019-09-09 19:55   ` Junio C Hamano
2019-09-09 21:05     ` Junio C Hamano
2019-09-09 22:21       ` Jeff King
2019-09-10  1:09         ` Junio C Hamano
2019-09-10 18:15       ` Jonathan Tan
2019-09-10 12:49   ` SZEDER Gábor
2019-09-10 18:19     ` Jonathan Tan

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=69f2b069-3e11-4a2e-9b81-bde18c463d8c@gmail.com \
    --to=stolee@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=jonathantanmy@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).