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From: Elijah Newren <newren@gmail.com>
To: Victoria Dye via GitGitGadget <gitgitgadget@gmail.com>
Cc: "Git Mailing List" <git@vger.kernel.org>,
	"Derrick Stolee" <stolee@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Taylor Blau" <me@ttaylorr.com>,
	"Bagas Sanjaya" <bagasdotme@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Phillip Wood" <phillip.wood123@gmail.com>,
	"Emily Shaffer" <emilyshaffer@google.com>,
	"Victoria Dye" <vdye@github.com>
Subject: Re: [PATCH v6 0/8] Sparse Index: integrate with reset
Date: Mon, 29 Nov 2021 10:37:19 -0800	[thread overview]
Message-ID: <CABPp-BG0iDHf268UAnRyA=0y0T69YTc+bLMdxCmSbrL8s=9ziA@mail.gmail.com> (raw)
In-Reply-To: <pull.1048.v6.git.1638201164.gitgitgadget@gmail.com>

Hi,

On Mon, Nov 29, 2021 at 7:52 AM Victoria Dye via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> Changes since V5
> ================
>
>  * Update t1092 test 'reset with wildcard pathspec' with more cases and
>    better checks
>  * Add "special case" wildcard pathspec check when determining whether to
>    expand the index (avoids double-loop over pathspecs & index entries)

Looks pretty good.  However, I'm worried this special case you added
at my prodding might be problematic, and that I may have been wrong to
prod you into it...

> Thanks! -Victoria
>
> Range-diff vs v5:
>
>  7:  a9135a5ed64 ! 7:  822d7344587 reset: make --mixed sparse-aware
>      @@ Commit message
>
>           Remove the `ensure_full_index` guard on `read_from_tree` and update `git
>           reset --mixed` to ensure it can use sparse directory index entries wherever
>      -    possible. Sparse directory entries are reset use `diff_tree_oid`, which
>      +    possible. Sparse directory entries are reset using `diff_tree_oid`, which
>           requires `change` and `add_remove` functions to process the internal
>           contents of the sparse directory. The `recursive` diff option handles cases
>           in which `reset --mixed` must diff/merge files that are nested multiple
>      @@ builtin/reset.c: static void update_index_from_diff(struct diff_queue_struct *q,
>       +          * (since we can reset whole sparse directories without expanding them).
>       +          */
>       +         if (item.nowildcard_len < item.len) {
>      ++                 /*
>      ++                  * Special case: if the pattern is a path inside the cone
>      ++                  * followed by only wildcards, the pattern cannot match
>      ++                  * partial sparse directories, so we don't expand the index.
>      ++                  */
>      ++                 if (path_in_cone_mode_sparse_checkout(item.original, &the_index) &&
>      ++                     strspn(item.original + item.nowildcard_len, "*") == item.len - item.nowildcard_len)

I usually expect in an &&-chain to see the cheaper function call first
(because that ordering often avoids the need to call the second
function), and I would presume that strspn() would be the cheaper of
the two.  Did you switch the order because you expect the strspn call
to nearly always return true, though?

Could the strspn() call be replaced by a `item.len ==
item.nowildcard_len + 1`?  I mean, sure, folks could list multiple
asterisks in a row in their pathspec, but that seems super unlikely
and even if it does happen the code will just fall back to the slower
codepath and still give them the right answer.  And the simpler check
feels a lot easier to parse for human readers.

But I'm worried there's a deeper issue here:


Is the wildcard character (or characters) in path treated as a literal
by path_in_cone_mode_sparse_checkout()?  I think it is...and I'm
worried that may be incorrect.  For example, if the path is

   foo/*

and the user has done a

  git sparse-checkout set foo/bar/

Then 'foo/baz/file' is not in the sparse checkout.  However, 'foo/*'
should match 'foo/baz/file' and yet 'foo/*' when treated as a literal
path would be considered in the sparse checkout by
path_in_cone_mode_sparse_checkout.  Does this result in the code
returning an incorrect answer?  (Or did I misunderstand something so
far?)

I'm wondering if I misled you earlier in my musings about whether we
could avoid the slow codepath for pathspecs with wildcard characters.
Maybe there's no safe optimization here and wildcard characters should
always go through the slower codepath.

>      ++                         continue;
>      ++
>       +                 for (pos = 0; pos < active_nr; pos++) {
>       +                         struct cache_entry *ce = active_cache[pos];
>       +
>  8:  f91d1dcf024 = 8:  ddd97fb2837 unpack-trees: improve performance of next_cache_entry
>
> --
> gitgitgadget

  parent reply	other threads:[~2021-11-29 22:35 UTC|newest]

Thread overview: 114+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-30 14:50 [PATCH 0/7] " Victoria Dye via GitGitGadget
2021-09-30 14:50 ` [PATCH 1/7] reset: behave correctly with sparse-checkout Kevin Willford via GitGitGadget
2021-09-30 18:34   ` Junio C Hamano
2021-10-01 14:55     ` Victoria Dye
2021-09-30 14:50 ` [PATCH 2/7] sparse-index: update command for expand/collapse test Victoria Dye via GitGitGadget
2021-09-30 19:17   ` Taylor Blau
2021-09-30 20:11     ` Victoria Dye
2021-09-30 21:32       ` Junio C Hamano
2021-09-30 22:59         ` Victoria Dye
2021-10-01  0:04           ` Junio C Hamano
2021-10-04 13:47             ` Victoria Dye
2021-10-01  9:14   ` Bagas Sanjaya
2021-09-30 14:50 ` [PATCH 3/7] reset: expand test coverage for sparse checkouts Victoria Dye via GitGitGadget
2021-09-30 14:50 ` [PATCH 4/7] reset: integrate with sparse index Victoria Dye via GitGitGadget
2021-09-30 14:50 ` [PATCH 5/7] reset: make sparse-aware (except --mixed) Victoria Dye via GitGitGadget
2021-09-30 14:51 ` [PATCH 6/7] reset: make --mixed sparse-aware Victoria Dye via GitGitGadget
2021-10-01 15:03   ` Victoria Dye
2021-09-30 14:51 ` [PATCH 7/7] unpack-trees: improve performance of next_cache_entry Victoria Dye via GitGitGadget
2021-10-05 13:20 ` [PATCH v2 0/7] Sparse Index: integrate with reset Victoria Dye via GitGitGadget
2021-10-05 13:20   ` [PATCH v2 1/7] reset: behave correctly with sparse-checkout Kevin Willford via GitGitGadget
2021-10-05 19:30     ` Junio C Hamano
2021-10-05 21:59       ` Victoria Dye
2021-10-06 12:44         ` Junio C Hamano
2021-10-06  1:46     ` Elijah Newren
2021-10-06 20:09       ` Victoria Dye
2021-10-06 10:31     ` Bagas Sanjaya
2021-10-05 13:20   ` [PATCH v2 2/7] update-index: add --force-full-index option for expand/collapse test Victoria Dye via GitGitGadget
2021-10-06  2:00     ` Elijah Newren
2021-10-06 20:40       ` Victoria Dye
2021-10-08  3:42         ` Elijah Newren
2021-10-08 17:11           ` Junio C Hamano
2021-10-06 10:33     ` Bagas Sanjaya
2021-10-05 13:20   ` [PATCH v2 3/7] reset: expand test coverage for sparse checkouts Victoria Dye via GitGitGadget
2021-10-06  2:04     ` Elijah Newren
2021-10-05 13:20   ` [PATCH v2 4/7] reset: integrate with sparse index Victoria Dye via GitGitGadget
2021-10-06  2:15     ` Elijah Newren
2021-10-06 17:48       ` Junio C Hamano
2021-10-05 13:20   ` [PATCH v2 5/7] reset: make sparse-aware (except --mixed) Victoria Dye via GitGitGadget
2021-10-06  3:43     ` Elijah Newren
2021-10-06 20:56       ` Victoria Dye
2021-10-06 10:34     ` Bagas Sanjaya
2021-10-05 13:20   ` [PATCH v2 6/7] reset: make --mixed sparse-aware Victoria Dye via GitGitGadget
2021-10-06  4:43     ` Elijah Newren
2021-10-07 14:34       ` Victoria Dye
2021-10-05 13:20   ` [PATCH v2 7/7] unpack-trees: improve performance of next_cache_entry Victoria Dye via GitGitGadget
2021-10-06 10:37     ` Bagas Sanjaya
2021-10-05 15:34   ` [PATCH v2 0/7] Sparse Index: integrate with reset Ævar Arnfjörð Bjarmason
2021-10-05 20:44     ` Victoria Dye
2021-10-06  5:46   ` Elijah Newren
2021-10-07 21:15   ` [PATCH v3 0/8] " Victoria Dye via GitGitGadget
2021-10-07 21:15     ` [PATCH v3 1/8] reset: rename is_missing to !is_in_reset_tree Victoria Dye via GitGitGadget
2021-10-07 21:15     ` [PATCH v3 2/8] reset: preserve skip-worktree bit in mixed reset Kevin Willford via GitGitGadget
2021-10-08  9:04       ` Junio C Hamano
2021-10-07 21:15     ` [PATCH v3 3/8] update-index: add --force-full-index option for expand/collapse test Victoria Dye via GitGitGadget
2021-10-08  2:50       ` Bagas Sanjaya
2021-10-08  5:24       ` Junio C Hamano
2021-10-08 15:47         ` Victoria Dye
2021-10-08 17:19           ` Junio C Hamano
2021-10-11 14:12             ` Derrick Stolee
2021-10-11 15:05               ` Victoria Dye
2021-10-11 15:24               ` Junio C Hamano
2021-10-07 21:15     ` [PATCH v3 4/8] reset: expand test coverage for sparse checkouts Victoria Dye via GitGitGadget
2021-10-07 21:15     ` [PATCH v3 5/8] reset: integrate with sparse index Victoria Dye via GitGitGadget
2021-10-07 21:15     ` [PATCH v3 6/8] reset: make sparse-aware (except --mixed) Victoria Dye via GitGitGadget
2021-10-08 11:09       ` Phillip Wood
2021-10-08 17:14         ` Victoria Dye
2021-10-08 18:31           ` Junio C Hamano
2021-10-09 11:18             ` Phillip Wood
2021-10-10 22:03               ` Junio C Hamano
2021-10-11 15:55                 ` Victoria Dye
2021-10-11 16:16                   ` Junio C Hamano
2021-10-12 10:16                 ` Phillip Wood
2021-10-12 19:15                   ` Junio C Hamano
2021-10-12 10:17           ` Phillip Wood
2021-10-07 21:15     ` [PATCH v3 7/8] reset: make --mixed sparse-aware Victoria Dye via GitGitGadget
2021-11-20 22:02       ` Elijah Newren
2021-11-22 16:46         ` Victoria Dye
2021-10-07 21:15     ` [PATCH v3 8/8] unpack-trees: improve performance of next_cache_entry Victoria Dye via GitGitGadget
2021-10-11 20:30     ` [PATCH v4 0/8] Sparse Index: integrate with reset Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 1/8] reset: rename is_missing to !is_in_reset_tree Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 2/8] reset: preserve skip-worktree bit in mixed reset Victoria Dye via GitGitGadget
2021-10-22  4:19         ` Emily Shaffer
2021-10-25 15:59           ` Victoria Dye
2021-10-11 20:30       ` [PATCH v4 3/8] sparse-index: update command for expand/collapse test Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 4/8] reset: expand test coverage for sparse checkouts Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 5/8] reset: integrate with sparse index Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 6/8] reset: make sparse-aware (except --mixed) Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 7/8] reset: make --mixed sparse-aware Victoria Dye via GitGitGadget
2021-10-11 20:30       ` [PATCH v4 8/8] unpack-trees: improve performance of next_cache_entry Victoria Dye via GitGitGadget
2021-10-27 14:39       ` [PATCH v5 0/8] Sparse Index: integrate with reset Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 1/8] reset: rename is_missing to !is_in_reset_tree Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 2/8] reset: preserve skip-worktree bit in mixed reset Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 3/8] sparse-index: update command for expand/collapse test Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 4/8] reset: expand test coverage for sparse checkouts Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 5/8] reset: integrate with sparse index Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 6/8] reset: make sparse-aware (except --mixed) Victoria Dye via GitGitGadget
2021-10-27 14:39         ` [PATCH v5 7/8] reset: make --mixed sparse-aware Victoria Dye via GitGitGadget
2021-11-20 22:05           ` Elijah Newren
2021-11-22 16:54             ` Victoria Dye
2021-10-27 14:39         ` [PATCH v5 8/8] unpack-trees: improve performance of next_cache_entry Victoria Dye via GitGitGadget
2021-11-20 22:13         ` [PATCH v5 0/8] Sparse Index: integrate with reset Elijah Newren
2021-11-29 15:52         ` [PATCH v6 " Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 1/8] reset: rename is_missing to !is_in_reset_tree Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 2/8] reset: preserve skip-worktree bit in mixed reset Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 3/8] sparse-index: update command for expand/collapse test Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 4/8] reset: expand test coverage for sparse checkouts Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 5/8] reset: integrate with sparse index Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 6/8] reset: make sparse-aware (except --mixed) Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 7/8] reset: make --mixed sparse-aware Victoria Dye via GitGitGadget
2021-11-29 15:52           ` [PATCH v6 8/8] unpack-trees: improve performance of next_cache_entry Victoria Dye via GitGitGadget
2021-11-29 18:37           ` Elijah Newren [this message]
2021-11-29 19:44             ` [PATCH v6 0/8] Sparse Index: integrate with reset Victoria Dye
2021-11-30  3:59               ` Elijah Newren
2021-12-01 20:26               ` Ævar Arnfjörð Bjarmason

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