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From: Michael Haggerty <mhagger@alum.mit.edu>
To: Junio C Hamano <gitster@pobox.com>
Cc: Shawn Pearce <spearce@spearce.org>, git <git@vger.kernel.org>,
	David Borowitz <dborowitz@google.com>,
	Stefan Beller <sbeller@google.com>, Jeff King <peff@peff.net>
Subject: Re: reftable [v7]: new ref storage format
Date: Thu, 17 Aug 2017 10:06:54 +0200	[thread overview]
Message-ID: <CAMy9T_GuU68mQTAvmPkaa6jPiNnoDAKCqA8y76rf3UrmMeyfTA@mail.gmail.com> (raw)
In-Reply-To: <xmqq60dnjka0.fsf@gitster.mtv.corp.google.com>

On Wed, Aug 16, 2017 at 11:05 PM, Junio C Hamano <gitster@pobox.com> wrote:
> I found it a slightly odd that we do not insist that update_indices
> that appear in a single reftable file are consecutive, yet we
> require that min_update_index of a reftable file must be one greater
> than the max_update_index of a previous one.  That is not a new
> issue in v7, though.

I think of `update_index` like a pseudo-time, and the
`min_update_index` and `max_update_index` to be stating that "this
reftable covers the time interval specified". So it's reasonable to
say that the reftable files, together, should cover all time.

But it might be that there are values of `update_index` for which no
events survived within a reftable file that covers that time interval.
This can happen if reference update records have been compacted away
because later reference updates overwrote their effects, and either

* reflogs were turned off for those updates, or
* the corresponding reflogs have been compacted into a separate file, or
* the corresponding reflog entries for those updates have been expired.

Michael

  reply	other threads:[~2017-08-17  8:07 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-16  2:48 reftable [v7]: new ref storage format Shawn Pearce
2017-08-16  6:15 ` Stefan Beller
2017-08-16 15:54   ` Shawn Pearce
2017-08-16 21:05 ` Junio C Hamano
2017-08-17  8:06   ` Michael Haggerty [this message]
2017-08-17 18:22     ` Junio C Hamano
2017-08-18  0:52 ` Shawn Pearce

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