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Re: [Gnu-arch-users] a brief note on "delta compression"
From: |
Tom Lord |
Subject: |
Re: [Gnu-arch-users] a brief note on "delta compression" |
Date: |
Mon, 3 May 2004 16:04:02 -0700 (PDT) |
> From: Aaron Bentley <address@hidden>
> Tom Lord wrote:
> > * "delta compression" -- meaning "store pre-combined deltas"
> > The second meaning of "delta compression" is vaguer, but generally
> > refers to replacing a sequence of deltas (aka changesets), which are
> > meant to be applied sequentially, with a single changeset that
> > represents their composition.
> This is the same as "summary deltas", discussed here:
> http://mail.gnu.org/archive/html/gnu-arch-users/2003-09/msg01774.html
> Summary deltas could be produced by "changeset composition":
> http://mail.gnu.org/archive/html/gnu-arch-users/2004-01/msg01168.html
> Right?
(I haven't double checked your URLs but) yes, this is pretty much the
same as what we've been calling "summary deltas" and I think that's a
better name for the idea than "delta compression". To my ear, "delta
compression" is the right name for the first meaning I gave -- storing
revisions as deltas against other revisions.
If you want to split hairs, I guess you could conceive of compressed
(i.e., combined) deltas in a situation where you're throwing away the
intermediate history -- "summary deltas" wouldn't be a good name for
that. So there's maybe a very slight distinction between compressed
(combined) deltas in general and summary deltas in particular. I
don't think you'd ever want combined deltas (in an archive) unless
they were summary deltas, though.
-t