Subject: Re: [PATCH v2 14/19] midx: teach `midx_fanout_add_midx_fanout()` about incremental MIDXs

From: Taylor Blau <[email-masked]>
Date: Thu, 1 Aug 2024 16:09:08 -0400

On Thu, Aug 01, 2024 at 06:29:06AM -0400, Jeff King wrote:
> On Wed, Jul 17, 2024 at 05:12:38PM -0400, Taylor Blau wrote:
>
> > The function `midx_fanout_add_midx_fanout()` is used to help construct
> > the fanout table when generating a MIDX by reusing data from an existing
> > MIDX.
>
> I'm not sure I understand the original function enough to know if we're
> doing the right thing. But I notice that after your series, we can only
> get into midx_fanout_add_midx_fanout() if !ctx->incremental. So is this
> code even used for an incremental midx?

Originally it was, but after 0c5a62f14b (midx-write.c: do not read
existing MIDX with `packs_to_include`, 2024-06-11) we no longer use this
function in that path. But...

> Or is it used if we are writing a non-incremental midx, but trying to
> reuse data from a chained one?

...we would use it in this one, so I think the patch stands. I added a
note at the end of the commit message to make sure that we don't forget
which paths do and don't reach this function.

Thanks,
Taylor