From: Patrick Steinhardt <ps@pks•im>
To: Junio C Hamano <gitster@pobox•com>
Cc: Derrick Stolee <stolee@gmail•com>,
git@vger•kernel.org, Taylor Blau <me@ttaylorr•com>
Subject: Re: [PATCH 0/6] odb: track commit graphs via object source
Date: Fri, 26 Sep 2025 07:18:26 +0200 [thread overview]
Message-ID: <aNYiIsUxR6yNQy_1@pks.im> (raw)
In-Reply-To: <xmqqo6qyfijl.fsf@gitster.g>
On Thu, Sep 25, 2025 at 12:17:50PM -0700, Junio C Hamano wrote:
> Patrick Steinhardt <ps@pks•im> writes:
>
> > There is no inherent reason why a new backend would not be able to use
> > the existing commit-graph infrastructure indeed. But there are reasons
> > that specific backends may not want to do so. If objects are already
> > stored in a database table, then it may make way more sense to store
> > additional metadata that is currently stored in the commit-graph in a
> > secondary database table instead of in the commit graph.
> > ...
> > This is roughly what I have in my head right now. And I realize that
> > this information really should be sitting in a design document. I'm
> > working on that, but still need to land two more patch series before I
> > want to send such a patch series to the list.
>
> So is everybody happy with this line of thought that makes it
> mandatory for each backend to decide and implement the commit-graph
> support if they want to?
>
> My reading of the later part of Taylor's message[*] tells me that at
> least Taylor does not agree with that position, and I am not sure
> about this design choice, either. Surely, each backend can have its
> own optimization, but looking at the way data from the commit-graph
> and other auxiliary data files are used to optimize real operations
> (like populating the essential fields of the commit object first
> from the graph, only to read other things lazily from the object
> database, or switching to completely different traversal machinery
> when reachability bitmap is available), we cannot say that each
> backend can store whatever side data they please and leave it at
> that. The code paths that are supposed to be generic need to be
> aware of these side data used for optimization to some degree, so
> conceptually it is much cleaner (well, at least to my eyes, that is)
> to declare that the auxiliary data files like commit-graph and
> reachability bitmaps are defined on the objects in the repository,
> no matter what backend is used to store them.
Quick update: I haven't found the time to reply to review feedback yet.
I'll pick this topic up again in one or two weeks.
Patrick
next prev parent reply other threads:[~2025-09-26 5:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-04 12:49 [PATCH 0/6] odb: track commit graphs via object source Patrick Steinhardt
2025-09-04 12:49 ` [PATCH 1/6] blame: drop explicit check for commit graph Patrick Steinhardt
2025-09-11 22:09 ` Taylor Blau
2025-09-04 12:49 ` [PATCH 2/6] revision: " Patrick Steinhardt
2025-09-11 22:16 ` Taylor Blau
2025-09-04 12:49 ` [PATCH 3/6] commit-graph: return the prepared commit graph from `prepare_commit_graph()` Patrick Steinhardt
2025-09-11 22:25 ` Taylor Blau
2025-09-04 12:49 ` [PATCH 4/6] commit-graph: return commit graph from `repo_find_commit_pos_in_graph()` Patrick Steinhardt
2025-09-11 22:54 ` Taylor Blau
2025-09-04 12:49 ` [PATCH 5/6] commit-graph: pass graphs that are to be merged as parameter Patrick Steinhardt
2025-09-04 12:50 ` [PATCH 6/6] odb: move commit-graph into the object sources Patrick Steinhardt
2025-09-11 23:00 ` Taylor Blau
2025-09-04 23:12 ` [PATCH 0/6] odb: track commit graphs via object source Junio C Hamano
2025-09-05 18:29 ` Derrick Stolee
2025-09-08 11:17 ` Patrick Steinhardt
2025-09-08 14:46 ` Derrick Stolee
2025-09-10 11:38 ` Patrick Steinhardt
2025-09-25 19:17 ` Junio C Hamano
2025-09-26 5:18 ` Patrick Steinhardt [this message]
2025-10-02 11:21 ` Patrick Steinhardt
2025-10-02 11:35 ` Patrick Steinhardt
2025-10-02 16:49 ` Junio C Hamano
2025-10-03 16:56 ` Derrick Stolee
2025-09-11 23:08 ` Taylor Blau
2025-09-04 23:27 ` Junio C Hamano
2025-09-05 6:18 ` Patrick Steinhardt
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