From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: "Ted Ts'o" <tytso@mit.edu>, "Jakub Narebski" <jnareb@gmail.com>,
"Jonathan Nieder" <jrnieder@gmail.com>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Clemens Buchacher" <drizzd@aon.at>,
git@vger.kernel.org
Subject: Re: generation numbers
Date: Wed, 06 Jul 2011 16:22:23 -0700 [thread overview]
Message-ID: <7viprfhu4w.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <20110706181200.GD17978@sigill.intra.peff.net> (Jeff King's message of "Wed, 6 Jul 2011 14:12:00 -0400")
Jeff King <peff@peff.net> writes:
> Yeah, that would be fine. With a sorted list of binary sha1s and 32-bit
> generation numbers, you're talking about 24 bytes per commit. Or a 6
> megabyte cache for linux-2.6.
>
> You'd probably want to be a little clever with updates. If I have
> calculated the generation number of every commit, and then do "git
> commit; git tag --contains HEAD", you probably don't want to rewrite the
> entire cache. You could probably journal a fixed number of entries in an
> unsorted file (or even in a parallel directory structure to loose
> objects), and then periodically write out the whole sorted list when the
> journal gets too big. Or choose a more clever data structure that can do
> in-place updates.
As to the low level implementation detail I agree everything you said, but
I have been wondering how the generation number should intereact with
grafts and replaces. It certainly would be safest whenever you change
grafts (which should be a rare event anyway).
next prev parent reply other threads:[~2011-07-06 23:22 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-11 19:04 [PATCH 0/4] Speed up git tag --contains Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 1/4] tag: speed up --contains calculation Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 2/4] limit "contains" traversals based on commit timestamp Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 3/4] default core.clockskew variable to one day Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 4/4] Why is "git tag --contains" so slow? Ævar Arnfjörð Bjarmason
2011-07-06 6:40 ` [PATCH 0/4] Speed up git tag --contains Jeff King
2011-07-06 6:54 ` Jeff King
2011-07-06 19:06 ` Clemens Buchacher
2011-07-06 6:56 ` Jonathan Nieder
2011-07-06 7:03 ` Jeff King
2011-07-06 14:26 ` generation numbers (was: [PATCH 0/4] Speed up git tag --contains) Jakub Narebski
2011-07-06 15:01 ` Ted Ts'o
2011-07-06 18:12 ` Jeff King
2011-07-06 18:46 ` Jakub Narebski
2011-07-07 18:59 ` Jeff King
2011-07-07 19:34 ` generation numbers Junio C Hamano
2011-07-07 20:31 ` Jakub Narebski
2011-07-07 20:52 ` A Large Angry SCM
2011-07-08 0:29 ` Junio C Hamano
2011-07-08 22:57 ` Jeff King
2011-07-06 23:22 ` Junio C Hamano [this message]
2011-07-07 19:08 ` Jeff King
2011-07-07 20:10 ` Jakub Narebski
2018-01-12 18:56 ` [PATCH 0/4] Speed up git tag --contains csilvers
2018-03-03 5:15 ` Jeff King
2018-03-08 23:05 ` csilvers
2018-03-12 13:45 ` Derrick Stolee
2018-03-12 23:59 ` Jeff King
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