Re: [PATCH 3/3] commit-graph: respect 'core.useBloomFilters'

From: Son Luong Ngoc <sluongng@gmail.com>
Date: Jul 1, 2020, 09:58 UTC
Message-ID: <CAL3xRKdZyE+9r-bPTDo_Fiz=nT_Y7uve+rvBqQZxjL-DYMGYpw@mail.gmail.com>

Hi folks,

On Tue, 30 Jun 2020 15:33:40 -0400, Jeff King wrote:

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> > > It might even be worth considering whether "changed paths" needs more
> > > context (or would if we add new features in the future). On a "git
> > > commit-graph write" command-line it is perfectly clear, but would
> > > core.commitGraphChangedPaths be worth it? It's definitely more specific,
> > > but it's also way more ugly. ;)
> >
> > Here's a third option what about 'graph.readChangedPaths'. I think that
> > Stolee and I discussed a new top-level 'graph' section, since we now
> > have a few commit-graph-related configuration variables in 'core'.
>
> Yes, I like that even better. Probably "graph" is sufficiently specific
> within Git's context, though I guess it _could_ bring to mind "git log
> --graph". So many overloaded terms. :)

I would suggest using 'commitgraph.readChangedPaths' as I was planning on implementing the same config in [1] but never got around to it.

From an end-user perspective, not server admin, 'graph' is very much correlated to 'git log --graph'.

Using 'commitgraph' instead of core could also help us enabling more config down the line that equate to the current options in 'git commit-graph write'.

I.e. something like 'commitgraph.writeSplit' might be desirable to tune the behavior of 'gc.writeCommitGraph' to use '--split=replace' strategy.

---

@Taylor: Thanks a lot for implementing this.

On Tue, 30 Jun 2020 13:17:36 -0400, Taylor Blau wrote:

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> We're planning on using these patches as part of a two-phase roll-out of
> changed-path Bloom filters, where the first phase conditions whether or
> not repositories *write* Bloom filters, and the second phase (controlled
> via the new 'core.useBloomFilters') controls whether repositories *read*
> their Bloom filters.

Could you elaborate a bit more on the 'two-phase roll-out' mentioned here?

I was looking for a way to verify whether a commit-graph chain has been written with Bloom filter (and force it to rewrite if not) but there seems to be no straightforward way?

Do we need to implement a flag in 'git commit-graph verify' to check for Bloom filter existence?

[1]: https://github.com/gitgitgadget/git/pull/633

Regards, Son Luong.