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From: Derrick Stolee <>
To: Taylor Blau <>,
Subject: Re: [PATCH 3/7] midx.c: prevent `expire` from removing the cruft pack
Date: Thu, 22 Sep 2022 10:08:05 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 9/19/2022 9:55 PM, Taylor Blau wrote:
> The `expire` sub-command unlinks any packs that are (a) contained in the
> MIDX, but (b) have no objects referenced by the MIDX.

It is important to note that this can only happen if all objects in
the pack have duplicates in other pack-files.
> This sub-command ignores `.keep` packs, which remain on-disk even if
> they have no objects referenced by the MIDX. Cruft packs, however,
> aren't given the same treatment: if none of the objects contained in the
> cruft pack are selected from the cruft pack by the MIDX, then the cruft
> pack is eligible to be expired.
> This is less than desireable, since the cruft pack has important

(according to my spell-checker)

> metadata about the individual object mtimes, which is useful to
> determine how quickly an object should age out of the repository when
> pruning.
> Ordinarily, we wouldn't expect the contents of a cruft pack to
> duplicated across non-cruft packs (and we'd expect to see the MIDX
> select all cruft objects from other sources even less often). But
> nonetheless, it is still possible to trick the `expire` sub-command into
> removing the `.mtimes` file in this circumstance.

I was initially unconvinced that this scenario was super-critical
to keeping the .mtimes file, but I was able to think of cases where
objects are duplicated out of the cruft pack due to de-thinning or
otherwise inefficiently packing unreachable objects into these
other pack-files.


  reply	other threads:[~2022-09-22 14:09 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-20  1:55 [PATCH 0/7] midx: ignore cruft pack with `repack`, `expire` Taylor Blau
2022-09-20  1:55 ` [PATCH 1/7] Documentation/git-multi-pack-index.txt: fix typo Taylor Blau
2022-09-20  1:55 ` [PATCH 2/7] Documentation/git-multi-pack-index.txt: clarify expire behavior Taylor Blau
2022-09-20  1:55 ` [PATCH 3/7] midx.c: prevent `expire` from removing the cruft pack Taylor Blau
2022-09-22 14:08   ` Derrick Stolee [this message]
2022-09-20  1:55 ` [PATCH 4/7] midx.c: avoid cruft packs with `repack --batch-size=0` Taylor Blau
2022-09-20  1:55 ` [PATCH 5/7] midx.c: replace `xcalloc()` with `CALLOC_ARRAY()` Taylor Blau
2022-09-20  1:55 ` [PATCH 6/7] midx.c: remove unnecessary loop condition Taylor Blau
2022-09-20  1:55 ` [PATCH 7/7] midx.c: avoid cruft packs with non-zero `repack --batch-size` Taylor Blau
2022-09-20 14:39 ` [PATCH 0/7] midx: ignore cruft pack with `repack`, `expire` Christian Couder
2022-09-22 14:14 ` Derrick Stolee

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