Re: [PATCH 2/2] commit-graph: fix murmur3, bump filter ver. to 2

From: Jonathan Tan <jonathantanmy@google.com>
Date: May 23, 2023, 23:00 UTC
Message-ID: <20230523230049.1225412-1-jonathantanmy@google.com>
In-Reply-To: <def26c71-0fbb-58a3-f1cd-f8e532b67503@github.com>

Derrick Stolee <derrickstolee@github.com> writes:

> I notice that you didn't update the commit-graph format docs,

Ah, thanks for the reminder.

Show 5 quoted lines

> Here is a potential plan to consider:
> 
>  1. v2.42.0 includes writing v2 format, off by default.
>  2. v2.43.0 writes v2 format by default.
>  3. v2.44.0 no longer parses v1 format (ignored without error).

First of all, thanks for your comments on the migration process - that is indeed the most complicated part of this.

The code change to support 2 versions seems not too hard (duplicate murmur3_seeded() and modify one so that we have one version 1 and one version 2, and teach fill_bloom_key() to call the appropriate one based on the struct bloom_filter_settings) but this requires both the code author and reviewer(s) to check that we don't have cases in which we read or write one version when we're supposed to do it with the other. And the benefit of doing this seems to just be giving server administrators an opportunity to perform the migration at a more relaxed pace, which I think there are other ways to accomplish if we really wanted to do this, so I wanted to avoid having 2 versions in the Git codebase.