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From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, Derrick Stolee <derrickstolee@github.com>,
	Taylor Blau <me@ttaylorr.com>
Subject: Re: [PATCH v5 0/4] Changed path filter hash fix and version bump
Date: Thu, 13 Jul 2023 15:16:46 -0700	[thread overview]
Message-ID: <xmqqlefjlanl.fsf@gitster.g> (raw)
In-Reply-To: <cover.1689283789.git.jonathantanmy@google.com> (Jonathan Tan's message of "Thu, 13 Jul 2023 14:42:07 -0700")

Jonathan Tan <jonathantanmy@google.com> writes:

> I did not implement the mitigation of not using the Bloom filters when
> a high-bit path is sought because, as Stolee says, this is useful only
> when mixing Git implementations and will slow down operations (without
> any increase in correctness) in the absence of such a mix [1].

Sensible, I guess.

>     @@ Commit message
>          This commit does not change the behavior of writing (Git writes changed
>          path filters when explicitly instructed regardless of any config
>          variable), but a subsequent commit will restrict Git such that it will
>     -    only write when commitgraph.changedPathsVersion is 0, 1, or 2.
>     +    only write when commitgraph.changedPathsVersion is a recognized value.

This is nicer.

>          Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
>          Signed-off-by: Junio C Hamano <gitster@pobox.com>
>     @@ Documentation/config/commitgraph.txt: commitGraph.maxNewFilters::
>      -	If true, then git will use the changed-path Bloom filters in the
>      -	commit-graph file (if it exists, and they are present). Defaults to
>      -	true. See linkgit:git-commit-graph[1] for more information.
>     -+	Deprecated. Equivalent to changedPathsVersion=1 if true, and
>     ++	Deprecated. Equivalent to changedPathsVersion=-1 if true, and
>      +	changedPathsVersion=0 if false.

I forgot to comment on this part earlier, but does the context make
it clear enough that these `changedPathsVersion` references are
about `commitGraph.changedPathsVersion` configuration variable
without fully spelled out?  They sit next to each other right now,
so it may not be too bad.  If they appeared across more distance,
I would be worried, though.

>      +commitGraph.changedPathsVersion::
>      +	Specifies the version of the changed-path Bloom filters that Git will read and
>     -+	write. May be 0 or 1. Any changed-path Bloom filters on disk that do not
>     ++	write. May be -1, 0 or 1. Any changed-path Bloom filters on disk that do not
>      +	match the version set in this config variable will be ignored.

So, any time the user configures this to a different value, we will
start to ignore the existing changed-path-filters data in the
repository, and when we are told to write commit-graph, we will
construct changed-path-filters data using the new version?

>      ++
>     -+Defaults to 1.
>     ++Defaults to -1.
>     +++
>     ++If -1, Git will use the version of the changed-path Bloom filters in the
>     ++repository, defaulting to 1 if there are none.

OK, that was misleading.  The configuration can say "-1" and it does
not mean "I'll ignore anything other than version -1"---it means
"I'll read anything".  The earlier statement should be toned down so
that we do not surprise readers, perhaps

    When set to a positive integer value, any changed-path Bloom
    filters on disk whose version is different from the value are
    ignored.

to signal that 0 and negative are special.  Then the readers can
anticipate that special cases are described next.

    When set to -1, then ...
    When set to 0, then ...
    Defaults to -1.
    
When set to the special value -1, what version will we write?

>      +If 0, git will write version 1 Bloom filters when instructed to write.

And we will only read 0 and refuse to read 1?  Or we will read both
0 and 1?

Thanks.

  parent reply	other threads:[~2023-07-13 22:16 UTC|newest]

Thread overview: 116+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-22 21:48 [PATCH 0/2] Changed path filter hash fix and version bump Jonathan Tan
2023-05-22 21:48 ` [PATCH 1/2] t4216: test wrong bloom filter version rejection Jonathan Tan
2023-05-22 21:48 ` [PATCH 2/2] commit-graph: fix murmur3, bump filter ver. to 2 Jonathan Tan
2023-05-23 13:00   ` Derrick Stolee
2023-05-23 23:00     ` Jonathan Tan
2023-05-23 23:51     ` Junio C Hamano
2023-05-24 21:26       ` Jonathan Tan
2023-05-26 13:19         ` Derrick Stolee
2023-05-30 17:26           ` Jonathan Tan
2023-05-23  4:42 ` [PATCH 0/2] Changed path filter hash fix and version bump Junio C Hamano
2023-05-31 23:12 ` [PATCH v2 0/3] " Jonathan Tan
2023-05-31 23:12   ` [PATCH v2 1/3] t4216: test changed path filters with high bit paths Jonathan Tan
2023-05-31 23:12   ` [PATCH v2 2/3] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-05-31 23:12   ` [PATCH v2 3/3] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-06-03  1:01   ` [PATCH v2 0/3] Changed path filter hash fix and version bump Junio C Hamano
2023-06-03  2:24     ` Junio C Hamano
2023-06-07 16:30       ` Jonathan Tan
2023-06-07 21:37         ` Jonathan Tan
2023-06-08 19:21 ` [PATCH v3 0/4] " Jonathan Tan
2023-06-08 19:21   ` [PATCH v3 1/4] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-06-08 19:52     ` Ramsay Jones
2023-06-12 21:26       ` Junio C Hamano
2023-06-08 19:21   ` [PATCH v3 2/4] t4216: test changed path filters with high bit paths Jonathan Tan
2023-06-08 19:21   ` [PATCH v3 3/4] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-06-08 19:21   ` [PATCH v3 4/4] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-06-08 19:50   ` [PATCH v3 0/4] Changed path filter hash fix and version bump Ramsay Jones
2023-06-09  0:08     ` Jonathan Tan
2023-06-12 21:31     ` Junio C Hamano
2023-06-13 17:16       ` Jonathan Tan
2023-06-13 17:29         ` [PATCH] CodingGuidelines: use octal escapes, not hex Jonathan Tan
2023-06-13 18:16           ` Eric Sunshine
2023-06-13 18:43             ` Jonathan Tan
2023-06-13 19:15               ` Eric Sunshine
2023-06-13 19:29                 ` Junio C Hamano
2023-06-13 19:16         ` [PATCH v3 0/4] Changed path filter hash fix and version bump Junio C Hamano
2023-06-13 17:39 ` [PATCH v4 " Jonathan Tan
2023-06-13 17:39   ` [PATCH v4 1/4] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-06-13 21:58     ` Junio C Hamano
2023-06-20 13:22       ` Derrick Stolee
2023-06-21 12:08       ` Taylor Blau
2023-06-22 22:26         ` Jonathan Tan
2023-06-23 13:05           ` Derrick Stolee
2023-06-13 17:39   ` [PATCH v4 2/4] t4216: test changed path filters with high bit paths Jonathan Tan
2023-06-13 17:39   ` [PATCH v4 3/4] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-06-20 13:28     ` Derrick Stolee
2023-06-21 12:14     ` Taylor Blau
2023-06-13 17:39   ` [PATCH v4 4/4] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-06-20 13:39     ` Derrick Stolee
2023-06-20 18:37       ` Junio C Hamano
2023-06-13 19:21   ` [PATCH v4 0/4] Changed path filter hash fix and version bump Junio C Hamano
2023-06-20 13:43     ` Derrick Stolee
2023-06-20 21:56       ` Jonathan Tan
2023-06-21 12:19       ` Taylor Blau
2023-06-21 17:53         ` Derrick Stolee
2023-06-22 22:27           ` Jonathan Tan
2023-06-23 13:18             ` Derrick Stolee
2023-07-13 21:42 ` [PATCH v5 " Jonathan Tan
2023-07-13 21:42   ` [PATCH v5 1/4] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-07-19 17:25     ` Taylor Blau
2023-07-20 20:20       ` Jonathan Tan
2023-07-21  1:38         ` Taylor Blau
2023-07-13 21:42   ` [PATCH v5 2/4] t4216: test changed path filters with high bit paths Jonathan Tan
2023-07-13 22:50     ` Junio C Hamano
2023-07-19 17:27       ` Taylor Blau
2023-07-19 17:55         ` [PATCH 0/4] commit-graph: avoid looking at Bloom filter data directly Taylor Blau
2023-07-19 17:55           ` [PATCH 1/4] t/helper/test-read-graph.c: extract `dump_graph_info()` Taylor Blau
2023-07-19 17:55           ` [PATCH 2/4] bloom.h: make `load_bloom_filter_from_graph()` public Taylor Blau
2023-07-19 17:55           ` [PATCH 3/4] t/helper/test-read-graph: implement `bloom-filters` mode Taylor Blau
2023-07-19 17:55           ` [PATCH 4/4] fixup! t4216: test changed path filters with high bit paths Taylor Blau
2023-07-19 19:24           ` [PATCH 0/4] commit-graph: avoid looking at Bloom filter data directly Junio C Hamano
2023-07-20 20:22           ` Jonathan Tan
2023-07-13 21:42   ` [PATCH v5 3/4] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-07-19 18:10     ` Taylor Blau
2023-07-20 20:42       ` Jonathan Tan
2023-07-20 21:02         ` Taylor Blau
2023-07-13 21:42   ` [PATCH v5 4/4] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-07-19 18:24     ` Taylor Blau
2023-07-20 21:27       ` Jonathan Tan
2023-07-26 23:32         ` Taylor Blau
2023-07-13 22:16   ` Junio C Hamano [this message]
2023-07-13 22:59     ` [PATCH v5 0/4] Changed path filter hash fix and version bump Junio C Hamano
2023-07-14 18:48     ` Jonathan Tan
2023-07-20 21:46 ` [PATCH v6 0/7] " Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 1/7] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 2/7] t/helper/test-read-graph.c: extract `dump_graph_info()` Jonathan Tan
2023-07-26 23:26     ` Taylor Blau
2023-07-20 21:46   ` [PATCH v6 3/7] bloom.h: make `load_bloom_filter_from_graph()` public Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 4/7] t/helper/test-read-graph: implement `bloom-filters` mode Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 5/7] t4216: test changed path filters with high bit paths Jonathan Tan
2023-07-26 23:28     ` Taylor Blau
2023-07-20 21:46   ` [PATCH v6 6/7] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-07-20 21:46   ` [PATCH v6 7/7] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-07-25 20:52   ` [PATCH v6 0/7] Changed path filter hash fix and version bump Junio C Hamano
2023-07-26 20:39   ` Junio C Hamano
2023-07-27  0:17     ` Taylor Blau
2023-07-27  0:49       ` Junio C Hamano
2023-07-27 17:39         ` Jonathan Tan
2023-07-27 17:56           ` Taylor Blau
2023-07-27 20:53             ` Jonathan Tan
2023-08-01 18:08               ` Taylor Blau
2023-08-01 18:52                 ` Jonathan Tan
2023-08-03  0:01                 ` Taylor Blau
2023-08-03 13:18                   ` Derrick Stolee
2023-08-03 18:45                     ` Taylor Blau
2023-07-27 18:44         ` Junio C Hamano
2023-08-01 18:41 ` [PATCH v7 " Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 1/7] gitformat-commit-graph: describe version 2 of BDAT Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 2/7] t/helper/test-read-graph.c: extract `dump_graph_info()` Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 3/7] bloom.h: make `load_bloom_filter_from_graph()` public Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 4/7] t/helper/test-read-graph: implement `bloom-filters` mode Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 5/7] t4216: test changed path filters with high bit paths Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 6/7] repo-settings: introduce commitgraph.changedPathsVersion Jonathan Tan
2023-08-01 18:41   ` [PATCH v7 7/7] commit-graph: new filter ver. that fixes murmur3 Jonathan Tan
2023-08-01 18:44   ` [PATCH v7 0/7] Changed path filter hash fix and version bump Junio C Hamano
2023-08-01 20:58     ` Taylor Blau
2023-08-01 21:07       ` Junio C Hamano

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