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From: "SZEDER Gábor" <szeder.dev@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>,
	git@vger.kernel.org, sandals@crustytoothpaste.net,
	"Junio C Hamano" <gitster@pobox.com>
Subject: Re: [PATCH v3 0/6] Create commit-graph file format v2
Date: Fri, 3 May 2019 16:16:14 +0200	[thread overview]
Message-ID: <20190503141613.GG14763@szeder.dev> (raw)
In-Reply-To: <04ac97c5-ab2b-2b23-4c84-8ed8aab0e2f5@gmail.com>

On Fri, May 03, 2019 at 08:47:25AM -0400, Derrick Stolee wrote:
> It would be much simpler to restrict the model. Your idea of changing
> the file name is the inspiration here.
> 
> * The "commit-graph" file is the base commit graph. It is always
>   closed under reachability (if a commit exists in this file, then
>   its parents are also in this file). We will also consider this to
>   be "commit-graph-0".
> 
> * A commit-graph-<N> exists, then we check for the existence of
>   commit-graph-<N+1>. This file can contain commits whose parents
>   are in any smaller file.
> 
> I think this resolves the issue of back-compat without updating
> the file format:
> 
> 1. Old clients will never look at commit-graph-N, so they will
>    never complain about an "incomplete" file.
> 
> 2. If we always open a read handle as we move up the list, then
>    a "merge and collapse" write to commit-graph-N will not
>    interrupt an existing process reading that file.

What if a process reading the commit-graph files runs short on file
descriptors and has to close some of them, while a second process is
merging commit-graph files?


> I'll start hacking on this model.

Have fun! :)


Semi-related, but I'm curious:  what are your plans for 'struct
commit's 'graph_pos' field, and how will it work with multiple
commit-graph files?

In particular: currently we use this 'graph_pos' field as an index
into the Commit Data chunk to find the metadata associated with a
given commit object.  But we could add any commit-specific metadata in
a new chunk, being an array ordered by commit OID, and then use
'graph_pos' as an index into this chunk as well.  I find this quite
convenient.  However, with mulitple commit-graph files there will be
multiple arrays...


  parent reply	other threads:[~2019-05-03 14:16 UTC|newest]

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-23 21:59 [PATCH 0/6] Create commit-graph file format v2 Derrick Stolee via GitGitGadget
2019-01-23 21:59 ` [PATCH 1/6] commit-graph: return with errors during write Derrick Stolee via GitGitGadget
2019-01-23 21:59 ` [PATCH 2/6] commit-graph: collapse parameters into flags Derrick Stolee via GitGitGadget
2019-01-23 21:59 ` [PATCH 3/6] commit-graph: create new version flags Derrick Stolee via GitGitGadget
2019-01-23 21:59 ` [PATCH 4/6] commit-graph: add --version=<n> option Derrick Stolee via GitGitGadget
2019-01-24  9:31   ` Ævar Arnfjörð Bjarmason
2019-01-23 21:59 ` [PATCH 5/6] commit-graph: implement file format version 2 Derrick Stolee via GitGitGadget
2019-01-23 23:56   ` Jonathan Tan
2019-01-24  9:40   ` Ævar Arnfjörð Bjarmason
2019-01-24 14:34     ` Derrick Stolee
2019-03-21  9:21   ` Ævar Arnfjörð Bjarmason
2019-01-23 21:59 ` [PATCH 6/6] commit-graph: test verifying a corrupt v2 header Derrick Stolee via GitGitGadget
2019-01-23 23:59   ` Jonathan Tan
2019-01-24 23:05 ` [PATCH 0/6] Create commit-graph file format v2 Junio C Hamano
2019-01-24 23:39 ` Junio C Hamano
2019-01-25 13:54   ` Derrick Stolee
2019-04-24 19:58 ` [PATCH v2 0/5] " Derrick Stolee via GitGitGadget
2019-04-24 19:58   ` [PATCH v2 1/5] commit-graph: return with errors during write Derrick Stolee via GitGitGadget
2019-04-24 19:58   ` [PATCH v2 2/5] commit-graph: collapse parameters into flags Derrick Stolee via GitGitGadget
2019-04-25  5:21     ` Junio C Hamano
2019-04-24 19:58   ` [PATCH v2 3/5] commit-graph: create new version flags Derrick Stolee via GitGitGadget
2019-04-25  5:29     ` Junio C Hamano
2019-04-25 11:09       ` Derrick Stolee
2019-04-25 21:31     ` Ævar Arnfjörð Bjarmason
2019-04-26  2:20       ` Junio C Hamano
2019-04-24 19:58   ` [PATCH v2 4/5] commit-graph: add --version=<n> option Derrick Stolee via GitGitGadget
2019-04-24 19:58   ` [PATCH v2 5/5] commit-graph: implement file format version 2 Derrick Stolee via GitGitGadget
2019-04-25 22:09   ` [PATCH v2 0/5] Create commit-graph file format v2 Ævar Arnfjörð Bjarmason
2019-04-26  2:28     ` Junio C Hamano
2019-04-26  8:33       ` Ævar Arnfjörð Bjarmason
2019-04-26 12:06         ` Derrick Stolee
2019-04-26 13:55           ` Ævar Arnfjörð Bjarmason
2019-04-27 12:57     ` Ævar Arnfjörð Bjarmason
2019-05-01 13:11   ` [PATCH v3 0/6] " Derrick Stolee via GitGitGadget
2019-05-01 13:11     ` [PATCH v3 1/6] commit-graph: return with errors during write Derrick Stolee via GitGitGadget
2019-05-01 14:46       ` Ævar Arnfjörð Bjarmason
2019-05-01 13:11     ` [PATCH v3 2/6] commit-graph: collapse parameters into flags Derrick Stolee via GitGitGadget
2019-05-01 13:11     ` [PATCH v3 3/6] commit-graph: create new version parameter Derrick Stolee via GitGitGadget
2019-05-01 13:11     ` [PATCH v3 4/6] commit-graph: add --version=<n> option Derrick Stolee via GitGitGadget
2019-05-01 13:11     ` [PATCH v3 5/6] commit-graph: implement file format version 2 Derrick Stolee via GitGitGadget
2019-05-01 19:12       ` Ævar Arnfjörð Bjarmason
2019-05-01 19:56         ` Derrick Stolee
2019-05-01 13:11     ` [PATCH v3 6/6] commit-graph: remove Future Work section Derrick Stolee via GitGitGadget
2019-05-01 14:58       ` Ævar Arnfjörð Bjarmason
2019-05-01 19:59         ` Derrick Stolee
2019-05-01 20:25     ` [PATCH v3 0/6] Create commit-graph file format v2 Ævar Arnfjörð Bjarmason
2019-05-02 13:26       ` Derrick Stolee
2019-05-02 18:02         ` Ævar Arnfjörð Bjarmason
2019-05-03 12:47           ` Derrick Stolee
2019-05-03 13:41             ` Ævar Arnfjörð Bjarmason
2019-05-06  8:27               ` Christian Couder
2019-05-06 13:47                 ` Derrick Stolee
2019-05-03 14:16             ` SZEDER Gábor [this message]
2019-05-03 15:11               ` Derrick Stolee
2019-05-09 14:22     ` [PATCH v4 00/11] Commit-graph write refactor (was: Create commit-graph file format v2) Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 01/11] commit-graph: fix the_repository reference Derrick Stolee via GitGitGadget
2019-05-13  2:56         ` Junio C Hamano
2019-05-09 14:22       ` [PATCH v4 02/11] commit-graph: return with errors during write Derrick Stolee via GitGitGadget
2019-05-13  3:13         ` Junio C Hamano
2019-05-13 11:04           ` Derrick Stolee
2019-05-13 11:22             ` Derrick Stolee
2019-05-09 14:22       ` [PATCH v4 03/11] commit-graph: collapse parameters into flags Derrick Stolee via GitGitGadget
2019-05-13  3:44         ` Junio C Hamano
2019-05-13 11:07           ` Derrick Stolee
2019-05-09 14:22       ` [PATCH v4 04/11] commit-graph: remove Future Work section Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 05/11] commit-graph: create write_commit_graph_context Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 07/11] commit-graph: extract fill_oids_from_commit_hex() Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 06/11] commit-graph: extract fill_oids_from_packs() Derrick Stolee via GitGitGadget
2019-05-13  5:05         ` Junio C Hamano
2019-05-09 14:22       ` [PATCH v4 08/11] commit-graph: extract fill_oids_from_all_packs() Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 09/11] commit-graph: extract count_distinct_commits() Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 10/11] commit-graph: extract copy_oids_to_commits() Derrick Stolee via GitGitGadget
2019-05-09 14:22       ` [PATCH v4 11/11] commit-graph: extract write_commit_graph_file() Derrick Stolee via GitGitGadget
2019-05-13  5:09         ` Junio C Hamano
2019-05-09 17:58       ` [PATCH v4 00/11] Commit-graph write refactor (was: Create commit-graph file format v2) Josh Steadmon
2019-06-12 13:29       ` [PATCH v5 " Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 01/11] commit-graph: fix the_repository reference Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 02/11] commit-graph: return with errors during write Derrick Stolee via GitGitGadget
2019-06-29 17:23           ` SZEDER Gábor
2019-07-01 12:19             ` Derrick Stolee
2019-06-12 13:29         ` [PATCH v5 03/11] commit-graph: collapse parameters into flags Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 04/11] commit-graph: remove Future Work section Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 05/11] commit-graph: create write_commit_graph_context Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 06/11] commit-graph: extract fill_oids_from_packs() Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 08/11] commit-graph: extract fill_oids_from_all_packs() Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 07/11] commit-graph: extract fill_oids_from_commit_hex() Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 09/11] commit-graph: extract count_distinct_commits() Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 10/11] commit-graph: extract copy_oids_to_commits() Derrick Stolee via GitGitGadget
2019-06-12 13:29         ` [PATCH v5 11/11] commit-graph: extract write_commit_graph_file() Derrick Stolee via GitGitGadget

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