From: Derrick Stolee <derrickstolee@github.com>
To: Jeff King <peff@peff.net>
Cc: Junio C Hamano <gitster@pobox.com>,
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, me@ttaylorr.com, vdye@github.com
Subject: Re: [PATCH v2 0/8] ref-filter: ahead/behind counting, faster --merged option
Date: Wed, 15 Mar 2023 13:44:53 -0400 [thread overview]
Message-ID: <97a34499-7dc0-72f7-abd2-1bd0a78fa956@github.com> (raw)
In-Reply-To: <ZBIA7+85Lld+lpUS@coredump.intra.peff.net>
On 3/15/2023 1:31 PM, Jeff King wrote:
> On Fri, Mar 10, 2023 at 02:25:52PM -0500, Derrick Stolee wrote:
>
>>> Having read all the patches, I am very impressed and pleased, but
>>> are we losing anything by having the feature inside for-each-ref
>>> compared to a new command ahead-behind? As far as I can tell, the
>>> new "for-each-ref --stdin" would still want to match refs and work
>>> only on refs, but there shouldn't be any reason for ahead-behind
>>> computation to limit to tips that are at the tip of a ref, so that
>>> may be one downside in this updated design. For the intended use
>>> case of "let's find which branches are stale", that downside does
>>> not matter in practice, but for other use cases people will think
>>> of in the future, the limitation might matter (at which time we can
>>> easily resurrect the other subcommand, using the internal machinery
>>> we have here, so it is not a huge deal, I presume).
>>
>> I think the for-each-ref implementation solves the use case we
>> had in mind, I think. I'll double-check to see if we ever use
>> exact commit IDs instead of reference names, but I think these
>> callers are rarely interested in an exact commit ID but instead
>> want the latest version of refs.
>
> One thing I'd worry about here are race conditions.
>
> If you have a porcelain-ish view (and I'd count "showing a web page" as
> a porcelain view) that requires several commands to compute, it's
> possible for there to be simultaneous ref updates between your commands.
> If each command is given a refname, then the results may not be
> consistent.
> I don't know if this is how your current application-level code calling
> ahead-behind works, or if it just accepts the possibility of a race (or
> maybe the call is not presented along with other information so it's
> sort-of atomic on its own). Presumably your double-checking will find
> out. :)
I completely agree on both of these points.
The major lift in this series is that the two commit walk algorithms
are being contributed to the core project in a way that are easy to
modify our 'git ahead-behind' builtin to use the "new" internals
without any UX change. Actually porting the application layer to use
'git for-each-ref' instead would be a second step, where I'd plan to
do this deep dive. From what I understand, though, these race conditions
do exist already, but they are minor relative to the cost of doing a
lookup of all the ref values and then calling this backend.
> I do otherwise like exposing this as an option of for-each-ref, as that
> is the way I'd expect most normal client users to want to get at the
> information. And if this is step 1 and that's good enough for now, and
> we have a path forward to later expose it for general commits, that's OK
> with me.
And if we truly need more general committish inputs for tips (HEAD~10,
too), then a new builtin could be built on top. Modeling it after
for-each-ref (for-each-commit?) would be a good start to make the
behavior as similar as possible. Doing that in full generality might
require strange updates to ref-filter.[c|h], but we can cross that
bridge when we come to it.
Thanks,
-Stolee
next prev parent reply other threads:[~2023-03-15 17:45 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 14:06 [PATCH 0/8] ahead-behind: new builtin for counting multiple commit ranges Derrick Stolee via GitGitGadget
2023-03-06 14:06 ` [PATCH 1/8] ahead-behind: create empty builtin Derrick Stolee via GitGitGadget
2023-03-06 18:48 ` Junio C Hamano
2023-03-07 0:40 ` Taylor Blau
2023-03-08 22:14 ` Derrick Stolee
2023-03-08 22:56 ` Junio C Hamano
2023-03-06 14:06 ` [PATCH 2/8] ahead-behind: parse tip references Derrick Stolee via GitGitGadget
2023-03-07 0:43 ` Taylor Blau
2023-03-06 14:06 ` [PATCH 3/8] ahead-behind: implement --ignore-missing option Derrick Stolee via GitGitGadget
2023-03-07 0:46 ` Taylor Blau
2023-03-06 14:06 ` [PATCH 4/8] commit-graph: combine generation computations Derrick Stolee via GitGitGadget
2023-03-06 14:06 ` [PATCH 5/8] commit-graph: return generation from memory Derrick Stolee via GitGitGadget
2023-03-06 14:06 ` [PATCH 6/8] commit-graph: introduce `ensure_generations_valid()` Taylor Blau via GitGitGadget
2023-03-06 18:52 ` Junio C Hamano
2023-03-07 0:50 ` Taylor Blau
2023-03-06 14:06 ` [PATCH 7/8] ahead-behind: implement ahead_behind() logic Derrick Stolee via GitGitGadget
2023-03-07 1:05 ` Taylor Blau
2023-03-09 17:32 ` Derrick Stolee
2023-03-06 14:06 ` [PATCH 8/8] ahead-behind: add --contains mode Derrick Stolee via GitGitGadget
2023-03-06 18:26 ` [PATCH 0/8] ahead-behind: new builtin for counting multiple commit ranges Junio C Hamano
2023-03-06 20:18 ` Derrick Stolee
2023-03-06 22:24 ` Junio C Hamano
2023-03-07 0:36 ` Taylor Blau
2023-03-09 9:20 ` Jeff King
2023-03-09 21:51 ` Junio C Hamano
2023-03-07 0:33 ` Taylor Blau
2023-03-10 17:20 ` [PATCH v2 0/8] ref-filter: ahead/behind counting, faster --merged option Derrick Stolee via GitGitGadget
2023-03-10 17:20 ` [PATCH v2 1/8] for-each-ref: add --stdin option Derrick Stolee via GitGitGadget
2023-03-10 18:08 ` Junio C Hamano
2023-03-13 10:31 ` Phillip Wood
2023-03-13 13:33 ` Derrick Stolee
2023-03-13 21:10 ` Taylor Blau
2023-03-15 13:37 ` Ævar Arnfjörð Bjarmason
2023-03-15 17:17 ` Jeff King
2023-03-15 17:49 ` Jeff King
2023-03-15 19:24 ` Junio C Hamano
2023-03-15 19:44 ` Jeff King
2023-03-10 17:20 ` [PATCH v2 2/8] for-each-ref: explicitly test no matches Derrick Stolee via GitGitGadget
2023-03-10 17:20 ` [PATCH v2 3/8] commit-graph: combine generation computations Derrick Stolee via GitGitGadget
2023-03-10 17:20 ` [PATCH v2 4/8] commit-graph: return generation from memory Derrick Stolee via GitGitGadget
2023-03-10 17:21 ` [PATCH v2 5/8] commit-graph: introduce `ensure_generations_valid()` Taylor Blau via GitGitGadget
2023-03-10 17:21 ` [PATCH v2 6/8] commit-reach: implement ahead_behind() logic Derrick Stolee via GitGitGadget
2023-03-15 13:50 ` Ævar Arnfjörð Bjarmason
2023-03-15 16:03 ` Junio C Hamano
2023-03-15 16:13 ` Derrick Stolee
2023-03-10 17:21 ` [PATCH v2 7/8] for-each-ref: add ahead-behind format atom Derrick Stolee via GitGitGadget
2023-03-10 19:09 ` Junio C Hamano
2023-03-15 13:57 ` Ævar Arnfjörð Bjarmason
2023-03-15 16:01 ` Junio C Hamano
2023-03-15 16:12 ` Derrick Stolee
2023-03-15 16:11 ` Derrick Stolee
2023-03-10 17:21 ` [PATCH v2 8/8] commit-reach: add tips_reachable_from_bases() Derrick Stolee via GitGitGadget
2023-03-15 14:13 ` Ævar Arnfjörð Bjarmason
2023-03-15 16:17 ` Derrick Stolee
2023-03-15 16:18 ` Derrick Stolee
2023-03-10 19:16 ` [PATCH v2 0/8] ref-filter: ahead/behind counting, faster --merged option Junio C Hamano
2023-03-10 19:25 ` Derrick Stolee
2023-03-15 17:31 ` Jeff King
2023-03-15 17:44 ` Derrick Stolee [this message]
2023-03-15 19:34 ` Junio C Hamano
2023-03-15 13:22 ` Ævar Arnfjörð Bjarmason
2023-03-15 13:54 ` Derrick Stolee
2023-03-15 17:45 ` [PATCH v3 " Derrick Stolee via GitGitGadget
2023-03-15 17:45 ` [PATCH v3 1/8] for-each-ref: add --stdin option Derrick Stolee via GitGitGadget
2023-03-15 18:06 ` Jeff King
2023-03-15 19:14 ` Junio C Hamano
2023-03-15 22:41 ` Jonathan Tan
2023-03-15 17:45 ` [PATCH v3 2/8] for-each-ref: explicitly test no matches Derrick Stolee via GitGitGadget
2023-03-15 17:45 ` [PATCH v3 3/8] commit-graph: combine generation computations Derrick Stolee via GitGitGadget
2023-03-15 22:49 ` Jonathan Tan
2023-03-17 18:30 ` Derrick Stolee
2023-03-15 17:45 ` [PATCH v3 4/8] commit-graph: return generation from memory Derrick Stolee via GitGitGadget
2023-03-15 22:58 ` Jonathan Tan
2023-03-15 17:45 ` [PATCH v3 5/8] commit-graph: introduce `ensure_generations_valid()` Taylor Blau via GitGitGadget
2023-03-15 17:45 ` [PATCH v3 6/8] commit-reach: implement ahead_behind() logic Derrick Stolee via GitGitGadget
2023-03-15 23:28 ` Jonathan Tan
2023-03-17 18:44 ` Derrick Stolee
2023-03-15 17:45 ` [PATCH v3 7/8] for-each-ref: add ahead-behind format atom Derrick Stolee via GitGitGadget
2023-03-15 17:45 ` [PATCH v3 8/8] commit-reach: add tips_reachable_from_bases() Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 0/9] ref-filter: ahead/behind counting, faster --merged option Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 1/9] for-each-ref: add --stdin option Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 2/9] for-each-ref: explicitly test no matches Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 3/9] commit-graph: refactor compute_topological_levels() Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 4/9] commit-graph: simplify compute_generation_numbers() Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 5/9] commit-graph: return generation from memory Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 6/9] commit-graph: introduce `ensure_generations_valid()` Taylor Blau via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 7/9] commit-reach: implement ahead_behind() logic Derrick Stolee via GitGitGadget
2023-03-20 20:40 ` Jonathan Tan
2023-03-20 11:26 ` [PATCH v4 8/9] for-each-ref: add ahead-behind format atom Derrick Stolee via GitGitGadget
2023-03-20 11:26 ` [PATCH v4 9/9] commit-reach: add tips_reachable_from_bases() Derrick Stolee via GitGitGadget
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