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From: Derrick Stolee <stolee@gmail.com>
To: Elijah Newren <newren@gmail.com>
Cc: Matheus Tavares <matheus.bernardino@usp.br>,
	Git Mailing List <git@vger.kernel.org>,
	Derrick Stolee <dstolee@microsoft.com>,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	Stefan Beller <stefanbeller@gmail.com>
Subject: Re: [RFC PATCH 2/3] grep: honor sparse checkout patterns
Date: Tue, 24 Mar 2020 13:02:02 -0400	[thread overview]
Message-ID: <068ff330-5ace-32b6-e930-db5bd7480bec@gmail.com> (raw)
In-Reply-To: <CABPp-BFf-A_a=_02gP_=kBFmQmpM8udFZyrq17Co_u+QWURFKw@mail.gmail.com>

On 3/24/2020 12:16 PM, Elijah Newren wrote:
> On Tue, Mar 24, 2020 at 8:12 AM Derrick Stolee <stolee@gmail.com> wrote:
>>
>> On 3/24/2020 3:15 AM, Elijah Newren wrote:
>>> Hi Matheus,
>>>
>>> On Mon, Mar 23, 2020 at 11:12 PM Matheus Tavares
> ...
>>>> Something I'm not entirely sure in this patch is how we implement the
>>>> mechanism to honor sparsity for the `git grep <commit-ish>` case (which
>>>> is treated in the grep_tree() function). Currently, the patch looks for
>>>> an index entry that matches the path, and then checks its skip_worktree
>>>
>>> As you discuss below, checking the index is both wrong _and_ costly.
>>
>> I'm not sure why checking the index is _wrong_, but I agree about the
>> performance cost.
> 
> Let's say there are two directories, dir1 and dir2.  Over time, there
> have existed a total of six files:
>    dir1/{a,b,c}
>    dir2/{d,e,f}
> At the current time, there are only four files in the index:
>    dir1/{a,b}
>    dir2/{d,e}
> And the user has done a `git sparse-checkout set dir2` and then at
> some point later run `git grep OTHERCOMMIT foobar`.  What happens?
> 
> Well, since we're in a sparse checkout, we should only search the
> relevant paths within OTHERCOMMIT for "foobar".  Let's say we attempt
> to figure out the "relevant paths" using the index.  We can tell that
> dir1/a and dir2/a are marked as SKIP_WORKTREE so we don't search them.
> dir1/c is untracked -- what do we do with it?  Include it?  Exclude
> it?  Carrying on with the other files, dir2/d and dir2/e are tracked
> and !SKIP_WORKTREE so we search them.  dir2/f is untracked -- what do
> we do with it?  Include it?  Exclude it?
> 
> We're left without the necessary information to tell whether we should
> search OTHERCOMMIT's dir1/c and dir2/f if we consult the index.  Any
> decision we make is going to be wrong for one of the two paths.
> 
> If we instead do not attempt to consult the index (which corresponds
> to a version close to HEAD) in order to ask questions about the
> completely different OTHERCOMMIT, but instead use the sparsity
> patterns to query whether those files/directories are interesting,
> then we get the right answer.  The index can only be consulted for the
> right answer in the case of --cached; in all other cases (including
> OTHERCOMMIT == HEAD), we should use the sparsity patterns.  In fact,
> we could also use the sparsity patterns in the case of --cached, it's
> just that for that one particular case consulting the index will also
> give the right answer.

Thanks! This helps a lot.

-Stolee


  reply	other threads:[~2020-03-24 17:02 UTC|newest]

Thread overview: 123+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24  6:04 [RFC PATCH 0/3] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-03-24  6:11 ` [RFC PATCH 1/3] doc: grep: unify info on configuration variables Matheus Tavares
2020-03-24  7:57   ` Elijah Newren
2020-03-24 21:26     ` Junio C Hamano
2020-03-24 23:38       ` Matheus Tavares
2020-03-24  6:12 ` [RFC PATCH 2/3] grep: honor sparse checkout patterns Matheus Tavares
2020-03-24  7:15   ` Elijah Newren
2020-03-24 15:12     ` Derrick Stolee
2020-03-24 16:16       ` Elijah Newren
2020-03-24 17:02         ` Derrick Stolee [this message]
2020-03-24 23:01       ` Matheus Tavares Bernardino
2020-03-24 22:55     ` Matheus Tavares Bernardino
2020-04-21  2:10       ` Matheus Tavares Bernardino
2020-04-21  3:08         ` Elijah Newren
2020-04-22 12:08           ` Derrick Stolee
2020-04-23  6:09           ` Matheus Tavares Bernardino
2020-03-24  6:13 ` [RFC PATCH 3/3] grep: add option to ignore sparsity patterns Matheus Tavares
2020-03-24  7:54   ` Elijah Newren
2020-03-24 18:30     ` Junio C Hamano
2020-03-24 19:07       ` Elijah Newren
2020-03-25 20:18         ` Junio C Hamano
2020-03-30  3:23       ` Matheus Tavares Bernardino
2020-03-31 19:12         ` Elijah Newren
2020-03-31 20:02           ` Derrick Stolee
2020-04-27 17:15             ` Matheus Tavares Bernardino
2020-04-29 16:46               ` Elijah Newren
2020-04-29 17:21             ` Elijah Newren
2020-03-25 23:15     ` Matheus Tavares Bernardino
2020-03-26  6:02       ` Elijah Newren
2020-03-27 15:51         ` Junio C Hamano
2020-03-27 19:01           ` Elijah Newren
2020-03-30  1:12         ` Matheus Tavares Bernardino
2020-03-31 16:48           ` Elijah Newren
2020-05-10  0:41 ` [RFC PATCH v2 0/4] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-05-10  0:41   ` [RFC PATCH v2 1/4] doc: grep: unify info on configuration variables Matheus Tavares
2020-05-10  0:41   ` [RFC PATCH v2 2/4] config: load the correct config.worktree file Matheus Tavares
2020-05-11 19:10     ` Junio C Hamano
2020-05-12 22:55       ` Matheus Tavares Bernardino
2020-05-12 23:22         ` Junio C Hamano
2020-05-10  0:41   ` [RFC PATCH v2 3/4] grep: honor sparse checkout patterns Matheus Tavares
2020-05-11 19:35     ` Junio C Hamano
2020-05-13  0:05       ` Matheus Tavares Bernardino
2020-05-13  0:17         ` Junio C Hamano
2020-05-21  7:26           ` Elijah Newren
2020-05-21 17:35             ` Matheus Tavares Bernardino
2020-05-21 17:52               ` Elijah Newren
2020-05-22  5:49                 ` Matheus Tavares Bernardino
2020-05-22 14:26                   ` Elijah Newren
2020-05-22 15:36                     ` Elijah Newren
2020-05-22 20:54                       ` Matheus Tavares Bernardino
2020-05-22 21:06                         ` Elijah Newren
2020-06-10 11:40                     ` Derrick Stolee
2020-06-10 16:22                       ` Matheus Tavares Bernardino
2020-06-10 17:42                         ` Derrick Stolee
2020-06-10 18:14                           ` Matheus Tavares Bernardino
2020-06-10 20:12                         ` Elijah Newren
2020-06-10 19:58                       ` Elijah Newren
2020-05-21  7:36       ` Elijah Newren
2020-05-10  0:41   ` [RFC PATCH v2 4/4] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-05-10  4:23     ` Matheus Tavares Bernardino
2020-05-21 17:18       ` Elijah Newren
2020-05-21  7:09     ` Elijah Newren
2020-05-28  1:12   ` [PATCH v3 0/5] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-05-28  1:12     ` [PATCH v3 1/5] doc: grep: unify info on configuration variables Matheus Tavares
2020-05-28  1:13     ` [PATCH v3 2/5] t/helper/test-config: return exit codes consistently Matheus Tavares
2020-05-30 14:29       ` Elijah Newren
2020-06-01  4:36         ` Matheus Tavares Bernardino
2020-05-28  1:13     ` [PATCH v3 3/5] config: correctly read worktree configs in submodules Matheus Tavares
2020-05-30 14:49       ` Elijah Newren
2020-06-01  4:38         ` Matheus Tavares Bernardino
2020-05-28  1:13     ` [PATCH v3 4/5] grep: honor sparse checkout patterns Matheus Tavares
2020-05-30 15:48       ` Elijah Newren
2020-06-01  4:44         ` Matheus Tavares Bernardino
2020-06-03  2:38           ` Elijah Newren
2020-06-10 17:08             ` Matheus Tavares Bernardino
2020-05-28  1:13     ` [PATCH v3 5/5] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-05-30 16:18       ` Elijah Newren
2020-06-01  4:45         ` Matheus Tavares Bernardino
2020-06-03  2:39           ` Elijah Newren
2020-06-10 21:15             ` Matheus Tavares Bernardino
2020-06-11  0:35               ` Elijah Newren
2020-06-12 15:44     ` [PATCH v4 0/6] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-06-12 15:44       ` [PATCH v4 1/6] doc: grep: unify info on configuration variables Matheus Tavares
2020-06-12 15:45       ` [PATCH v4 2/6] t/helper/test-config: return exit codes consistently Matheus Tavares
2020-06-12 15:45       ` [PATCH v4 3/6] t/helper/test-config: facilitate addition of new cli options Matheus Tavares
2020-06-12 15:45       ` [PATCH v4 4/6] config: correctly read worktree configs in submodules Matheus Tavares
2020-06-16 19:13         ` Elijah Newren
2020-06-21 16:05           ` Matheus Tavares Bernardino
2020-09-01  2:41         ` Jonathan Nieder
2020-09-01 21:44           ` Matheus Tavares Bernardino
2020-06-12 15:45       ` [PATCH v4 5/6] grep: honor sparse checkout patterns Matheus Tavares
2020-06-12 15:45       ` [PATCH v4 6/6] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-06-16 22:31       ` [PATCH v4 0/6] grep: honor sparse checkout and add option to ignore it Elijah Newren
2020-09-02  6:17       ` [PATCH v5 0/8] " Matheus Tavares
2020-09-02  6:17         ` [PATCH v5 1/8] doc: grep: unify info on configuration variables Matheus Tavares
2020-09-02  6:17         ` [PATCH v5 2/8] t1308-config-set: avoid false positives when using test-config Matheus Tavares
2020-09-02  6:57           ` Eric Sunshine
2020-09-02 16:16             ` Matheus Tavares Bernardino
2020-09-02 16:38               ` Eric Sunshine
2020-09-02  6:17         ` [PATCH v5 3/8] t/helper/test-config: be consistent with exit codes Matheus Tavares
2020-09-02  6:17         ` [PATCH v5 4/8] t/helper/test-config: check argc before accessing argv Matheus Tavares
2020-09-02  7:18           ` Eric Sunshine
2020-09-02  6:17         ` [PATCH v5 5/8] t/helper/test-config: unify exit labels Matheus Tavares
2020-09-02  7:30           ` Eric Sunshine
2020-09-02  6:17         ` [PATCH v5 6/8] config: correctly read worktree configs in submodules Matheus Tavares
2020-09-02 20:15           ` Jonathan Nieder
2020-09-09 13:04             ` Matheus Tavares Bernardino
2020-09-09 23:32               ` Jonathan Nieder
2020-09-02  6:17         ` [PATCH v5 7/8] grep: honor sparse checkout patterns Matheus Tavares
2020-09-02  6:17         ` [PATCH v5 8/8] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2020-09-10 17:21         ` [PATCH v6 0/9] grep: honor sparse checkout and add option to ignore it Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 1/9] doc: grep: unify info on configuration variables Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 2/9] t1308-config-set: avoid false positives when using test-config Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 3/9] t/helper/test-config: be consistent with exit codes Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 4/9] t/helper/test-config: diagnose missing arguments Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 5/9] t/helper/test-config: unify exit labels Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 6/9] config: make do_git_config_sequence receive a 'struct repository' Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 7/9] config: correctly read worktree configs in submodules Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 8/9] grep: honor sparse checkout patterns Matheus Tavares
2020-09-10 17:21           ` [PATCH v6 9/9] config: add setting to ignore sparsity patterns in some cmds Matheus Tavares
2021-02-09 21:33           ` [PATCH v7] grep: honor sparse-checkout on working tree searches Matheus Tavares
2021-02-09 23:23             ` Junio C Hamano
2021-02-10  6:12               ` Elijah Newren

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