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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Jeff King" <peff@peff.net>,
	git@vger.kernel.org, "Gregory Anders" <greg@gpanders.com>,
	"Đoàn Trần Công Danh" <congdanhqx@gmail.com>,
	"Eric Sunshine" <sunshine@sunshineco.com>,
	"Eric Wong" <e@80x24.org>
Subject: Re: [PATCH v2 00/10] send-email: various optimizations to speed up by >2x
Date: Fri, 21 May 2021 08:23:15 +0200	[thread overview]
Message-ID: <875yzcpo52.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <xmqqv97drmge.fsf@gitster.g>


On Fri, May 21 2021, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
>
>> I like all of this, except for the change in the interface of
>> Git::config_regexp(). You mention that it's new-ish, and probably not in
>> wide use. And I agree that's probably true. But it feels like violating
>> a principle of not breaking APIs, and we should stick to that principle
>> and not bend it for "well, it's not that old an API".
>>
>> I'd find it more compelling if it the existing interface was broken or
>> hard to avoid changing. But couldn't we just add a new function with the
>> extra info (config_regexp_with_values() or something)?
>
> We seem to use it in-tree only once, but we have no control over
> what out-of-tree users have been doing.

I thought people might have bought my argument in v1 that we just
document these as "public" as part of some copy/pasting in Git.pm, but
sure, I'll re-roll and make this a new function or something...

> I do like your proposed name for the fact that it has _with_values
> in it; the original gave us only a list of configuration variable
> names, and now we are getting name-value tuples.
>
> BUT
>
> I am not sure if I like the new interface, and I do not know if the
> the name "config_with_values" is a good match for what it does.
>
> Namely, when a function is described as:
>
>     =item config_regexp ( RE )
>
>     Retrieve the list of configuration key names matching the regular
>     expression C<RE>. The return value is an ARRAY of key-value pairs.
>
> I would expect it to return ([key1, value1], [key2, value2], ...),
> but the implementation returns (key1, value1, key2, value2, ...),
> i.e. a flattened list, if I am not mistaken.


...

>     my @cmd = ('config', '--null', '--get-regexp', $regex);
>     unshift @cmd, $self if $self;
>     my $data = command(@cmd);
>     my (@kv) = map { split /\n/, $_, 2 } split /\0/, $data;
>     return @kv;
>
> We get NUL terminated records, so we first split the entire output
> at NULs (to get a list of key-value records).  Each key-value record
> has the key followed by LF followed by value, so we split it at the
> first LF (i.e. a value with an embedded LF would behave correctly)
> to extract key and value out of it.  But the resulting list is a
> flat list with alternating key and value.
>
> The side that works on the returned value of courese knows that it
> is getting a flattened list and acts accordingly:
>
>     my @kv = Git::config_regexp("^sende?mail[.]");
>     while (my ($k, $v) = splice @kv, 0, 2) {
>         push @{$known_config_keys{$k}} => $v;
>     }
>
> Perhaps it may be more performant than a more obvious and
> straight-forward "list of tuples", i.e.
>
>     return map { [split /\n/, $_, 2] } split /\0/, $data;
>
>     my @kv = Git::config_regexp("^sende?mail[.]");
>     for my $tuple (@kv) {
>         push @{$known_config_keys{$tuple->[0]}}, $tuple->[1];
>     }
>
> but somehow the flattened list felt unnatural at least to a naïve
> reader like me.

The "performant" really doesn't matter here, we're comparing shelling
out to getting a small number of config keys back. So I wasn't trying to
optimize this.

Returning a flattened list is idiomatic in Perl, it means that a caller
can do any of:

    # I only care about the last value for a key, or only about
    # existence checks
    my %hash = func();

Or:

    # I want all key-values to iterate over
    my @kv = func();

Returning touples like this makes that less convenient for both, who'll
need to do more work to unpack them.

For what it's worth In Perl "return a list" means "flattened list", the
term "flattened list" I think comes from other languages. You'd call
what you're suggesting a list of arrays, or (if a top-level reference)
an array of arrays, AoA for short, AoH for array (ref) of hashes etc.

  reply	other threads:[~2021-05-21  7:00 UTC|newest]

Thread overview: 108+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12 13:48 [PATCH 0/9] send-email: various optimizations to speed up by >2x Ævar Arnfjörð Bjarmason
2021-05-12 13:48 ` [PATCH 1/9] send-email: remove non-working support for "sendemail.smtpssl" Ævar Arnfjörð Bjarmason
2021-05-12 15:46   ` Đoàn Trần Công Danh
2021-05-12 13:48 ` [PATCH 2/9] send-email: refactor sendemail.smtpencryption config parsing Ævar Arnfjörð Bjarmason
2021-05-12 13:48 ` [PATCH 3/9] send-email: lazily load config for a big speedup Ævar Arnfjörð Bjarmason
2021-05-12 13:48 ` [PATCH 4/9] send-email: lazily shell out to "git var" Ævar Arnfjörð Bjarmason
2021-05-12 13:48 ` [PATCH 5/9] send-email: use function syntax instead of barewords Ævar Arnfjörð Bjarmason
2021-05-12 23:11   ` Jeff King
2021-05-12 13:48 ` [PATCH 6/9] send-email: get rid of indirect object syntax Ævar Arnfjörð Bjarmason
2021-05-12 13:48 ` [PATCH 7/9] send-email: lazily load modules for a big speedup Ævar Arnfjörð Bjarmason
2021-05-12 13:48 ` [PATCH 8/9] perl: lazily load some common Git.pm setup code Ævar Arnfjörð Bjarmason
2021-05-12 18:05   ` Eric Wong
2021-05-12 13:48 ` [PATCH 9/9] send-email: move trivial config handling to Perl Ævar Arnfjörð Bjarmason
2021-05-12 19:52   ` Eric Sunshine
2021-05-12 23:08   ` Jeff King
2021-05-13  7:04     ` Felipe Contreras
2021-05-13  7:07       ` Ævar Arnfjörð Bjarmason
2021-05-13  7:26       ` Jeff King
2021-05-13  8:15         ` Felipe Contreras
2021-05-13 11:45           ` Ævar Arnfjörð Bjarmason
2021-05-12 18:04 ` [PATCH 0/9] send-email: various optimizations to speed up by >2x Eric Wong
2021-05-12 23:34 ` Jeff King
2021-05-12 23:36 ` Jeff King
2021-05-13  7:37   ` Ævar Arnfjörð Bjarmason
2021-05-13  7:49     ` Jeff King
2021-05-20  8:18 ` [PATCH v2 00/10] " Ævar Arnfjörð Bjarmason
2021-05-20  8:18   ` [PATCH v2 01/10] send-email: remove non-working support for "sendemail.smtpssl" Ævar Arnfjörð Bjarmason
2021-05-20  8:18   ` [PATCH v2 02/10] send-email: refactor sendemail.smtpencryption config parsing Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 03/10] send-email: lazily load config for a big speedup Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 04/10] send-email: lazily shell out to "git var" Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 05/10] send-email: use function syntax instead of barewords Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 06/10] send-email: get rid of indirect object syntax Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 07/10] send-email: lazily load modules for a big speedup Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 08/10] perl: lazily load some common Git.pm setup code Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 09/10] send-email: move trivial config handling to Perl Ævar Arnfjörð Bjarmason
2021-05-20  8:19   ` [PATCH v2 10/10] perl: nano-optimize by replacing Cwd::cwd() with Cwd::getcwd() Ævar Arnfjörð Bjarmason
2021-05-20  8:27   ` [PATCH v2 00/10] send-email: various optimizations to speed up by >2x Jeff King
2021-05-20 23:53     ` Junio C Hamano
2021-05-21  6:23       ` Ævar Arnfjörð Bjarmason [this message]
2021-05-21  7:07         ` Junio C Hamano
2021-05-21  9:13         ` Jeff King
2021-05-21  9:24           ` Ævar Arnfjörð Bjarmason
2021-05-21  9:37             ` Jeff King
2021-05-28 15:49         ` Felipe Contreras
2021-05-29  8:19           ` Ævar Arnfjörð Bjarmason
2021-05-29 14:53             ` Felipe Contreras
2021-05-30 11:33               ` Ævar Arnfjörð Bjarmason
2021-05-30 16:07                 ` Felipe Contreras
2021-05-28 15:12     ` Felipe Contreras
2021-05-23  8:56   ` [PATCH v3 00/13] " Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 01/13] send-email tests: support GIT_TEST_PERL_FATAL_WARNINGS=true Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 02/13] send-email tests: test for boolean variables without a value Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 03/13] send-email: remove non-working support for "sendemail.smtpssl" Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 04/13] send-email: refactor sendemail.smtpencryption config parsing Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 05/13] send-email: copy "config_regxp" into git-send-email.perl Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 06/13] send-email: lazily load config for a big speedup Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 07/13] send-email: lazily shell out to "git var" Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 08/13] send-email: use function syntax instead of barewords Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 09/13] send-email: get rid of indirect object syntax Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 10/13] send-email: lazily load modules for a big speedup Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 11/13] perl: lazily load some common Git.pm setup code Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 12/13] send-email: move trivial config handling to Perl Ævar Arnfjörð Bjarmason
2021-05-23  8:56     ` [PATCH v3 13/13] perl: nano-optimize by replacing Cwd::cwd() with Cwd::getcwd() Ævar Arnfjörð Bjarmason
2021-05-24  1:15     ` [PATCH v3 00/13] send-email: various optimizations to speed up by >2x Junio C Hamano
2021-05-24  7:52     ` [PATCH v4 " Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 01/13] send-email tests: support GIT_TEST_PERL_FATAL_WARNINGS=true Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 02/13] send-email tests: test for boolean variables without a value Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 03/13] send-email: remove non-working support for "sendemail.smtpssl" Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 04/13] send-email: refactor sendemail.smtpencryption config parsing Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 05/13] send-email: copy "config_regxp" into git-send-email.perl Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 06/13] send-email: lazily load config for a big speedup Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 07/13] send-email: lazily shell out to "git var" Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 08/13] send-email: use function syntax instead of barewords Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 09/13] send-email: get rid of indirect object syntax Ævar Arnfjörð Bjarmason
2021-05-24  7:52       ` [PATCH v4 10/13] send-email: lazily load modules for a big speedup Ævar Arnfjörð Bjarmason
2021-05-27  1:11         ` Junio C Hamano
2021-05-27 11:36           ` Ævar Arnfjörð Bjarmason
2021-05-24  7:53       ` [PATCH v4 11/13] perl: lazily load some common Git.pm setup code Ævar Arnfjörð Bjarmason
2021-05-24  7:53       ` [PATCH v4 12/13] send-email: move trivial config handling to Perl Ævar Arnfjörð Bjarmason
2021-05-27 15:57         ` Jeff King
2021-05-24  7:53       ` [PATCH v4 13/13] perl: nano-optimize by replacing Cwd::cwd() with Cwd::getcwd() Ævar Arnfjörð Bjarmason
2021-05-27 16:00       ` [PATCH v4 00/13] send-email: various optimizations to speed up by >2x Jeff King
2021-05-28  9:23       ` [PATCH v5 " Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 01/13] send-email tests: support GIT_TEST_PERL_FATAL_WARNINGS=true Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 02/13] send-email tests: test for boolean variables without a value Ævar Arnfjörð Bjarmason
2021-07-10 23:23           ` Jeff King
2021-05-28  9:23         ` [PATCH v5 03/13] send-email: remove non-working support for "sendemail.smtpssl" Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 04/13] send-email: refactor sendemail.smtpencryption config parsing Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 05/13] send-email: copy "config_regxp" into git-send-email.perl Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 06/13] send-email: lazily load config for a big speedup Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 07/13] send-email: lazily shell out to "git var" Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 08/13] send-email: use function syntax instead of barewords Ævar Arnfjörð Bjarmason
2021-05-28 16:10           ` Felipe Contreras
2021-05-29  8:17             ` Ævar Arnfjörð Bjarmason
2021-05-29 14:25               ` Felipe Contreras
2021-05-28  9:23         ` [PATCH v5 09/13] send-email: get rid of indirect object syntax Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 10/13] send-email: lazily load modules for a big speedup Ævar Arnfjörð Bjarmason
2021-05-28 15:55           ` Felipe Contreras
2021-05-29  8:12             ` Ævar Arnfjörð Bjarmason
2021-05-29 14:24               ` Felipe Contreras
2021-05-28  9:23         ` [PATCH v5 11/13] perl: lazily load some common Git.pm setup code Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 12/13] send-email: move trivial config handling to Perl Ævar Arnfjörð Bjarmason
2021-05-28  9:23         ` [PATCH v5 13/13] perl: nano-optimize by replacing Cwd::cwd() with Cwd::getcwd() Ævar Arnfjörð Bjarmason
2021-05-28 16:13         ` [PATCH v5 00/13] send-email: various optimizations to speed up by >2x Felipe Contreras
2021-05-31  5:48         ` Jeff King
2021-05-31  9:53           ` Ævar Arnfjörð Bjarmason
2021-05-31 14:38             ` Jeff King
2021-05-27  7:21 ` [PATCH 0/9] " Elijah Newren

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