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[104.178.186.189]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-894d36a9bdbsm5195396d6.11.2026.01.27.14.13.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jan 2026 14:13:29 -0800 (PST) Date: Tue, 27 Jan 2026 17:13:28 -0500 From: Taylor Blau To: Patrick Steinhardt Cc: git@vger.kernel.org, Jeff King , Elijah Newren , Junio C Hamano Subject: Re: [PATCH v2 17/18] midx: implement MIDX compaction Message-ID: References: <13336e864f4ed3a6954b782f0bcc090d92ac722c.1768420450.git.me@ttaylorr.com> Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Tue, Jan 27, 2026 at 08:35:10AM +0100, Patrick Steinhardt wrote: > > + if (!from_midx) > > + die(_("could not find MIDX: %s"), argv[0]); > > + if (!to_midx) > > + die(_("could not find MIDX: %s"), argv[1]); > > + if (from_midx == to_midx) > > + die(_("MIDX compaction endpoints must be unique")); > > + > > + for (m = from_midx; m; m = m->base_midx) { > > + if (m == to_midx) > > + die(_("MIDX %s must be an ancestor of %s"), argv[0], argv[1]); > > + } > > These new checks all feel sensible to me. Thanks for taking a look and suggesting them in the first place! > > diff --git a/midx-write.c b/midx-write.c > > index ca2469213e6..afa077a09cc 100644 > > --- a/midx-write.c > > +++ b/midx-write.c > > @@ -1120,12 +1216,23 @@ static bool midx_needs_update(struct multi_pack_index *midx, struct write_midx_c > > @@ -1162,6 +1270,19 @@ static int write_midx_internal(struct write_midx_opts *opts) > > die(_("unknown MIDX version: %d"), ctx.version); > > > > ctx.incremental = !!(opts->flags & MIDX_WRITE_INCREMENTAL); > > + ctx.compact = !!(opts->flags & MIDX_WRITE_COMPACT); > > + > > + if (ctx.compact) { > > + if (ctx.version != MIDX_VERSION_V2) > > + die(_("cannot perform MIDX compaction with v1 format")); > > Right. So if the user has configured "midx.version=1" they cannot > compact. Exactly. I think the limitation here is a fundamental one, too, since by its nature compaction *must* retain the pseudo-pack order concatenated across each MIDX layer in the compaction range. With midx.version=1, we don't have a way to express that information in a backwards-compatible way, so midx.version=2 here is a requirement. > > @@ -1354,12 +1491,19 @@ static int write_midx_internal(struct write_midx_opts *opts) > > ctx.large_offsets_needed = 1; > > } > > > > - QSORT(ctx.info, ctx.nr, pack_info_compare); > > + if (ctx.compact) { > > + if (ctx.version != MIDX_VERSION_V2) > > + BUG("performing MIDX compaction with v1 MIDX"); > > Isn't this `BUG()` redundant with the above call to `die()`? Technically, though I put it in here as a sanity check to ensure that any potential regressions with the above die() don't cause us to get into a worse situation that would result in bitmap corruption. Thanks, Taylor