Re: [PATCH v2 6/8] repack: track the preferred pack explicitly in MIDX write steps

[Jeff King <peff@peff.net>]

On Fri, Oct 02, 2026 at 08:00:52PM -0500, Taylor Blau wrote:

> On Fri, Oct 02, 2026 at 07:28:34PM -0400, Jeff King wrote:
> > On Wed, Sep 30, 2026 at 11:11:58PM -0500, Taylor Blau wrote:
> >
> > > A MIDX write step marks preferred packs in its string-list entries and
> > > chooses the last marked entry when executing the step. That makes the
> > > choice depend on list order, preventing the list from being sorted for
> > > membership checks.
> > >
> > > Record the last candidate directly in the step, borrowing its name from
> > > the write list. This preserves preferred-pack selection while allowing
> > > the list to be sorted without changing that choice.
> >
> > This is certainly cleaner, though it looks like the existing code works
> > by marking item->util and then doing a linear search for it. So wouldn't
> > that work even after sorting?
> 
> It would if only one entry were marked, but we can mark several.
> 
> For example, when `repack_make_midx_compaction_plan()` folds multiple
> MIDX layers into one via a WRITE step, it marks each layer's preferred pack
> without clearing the earlier marks. The scan doesn't stop at the first
> such mark, and the last marked entry wins.
> 
> So sorting would of course preserve the marks, but may change which one
> comes last.

OK, that does make more sense. Re-reading your commit message again, I
see it even says that, but somehow it didn't quite sink in the first
time for me.

-Peff