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Re: Size of revs file when deleting lines in a big text file

From: Daniel Berlin <dberlin_at_dberlin.org>
Date: 2006-12-12 06:18:43 CET

On 12/11/06, Martin Scharrer <mailinglists@madmarty.de> wrote:
> Hi Malcolm,
> thanks for the explanation in this detail. This makes most things much clearer
> for me.
> On Monday 11 December 2006 21:33, Malcolm Rowe wrote:
> > algorithm.
> Ok I understand the operation of the window-oriented delta algorithm now and
> there need for binary files. But it is not possible to fall-back on a
> diff-like patch in the case of small changes of a large text file, or is this
> not compatible with the overall delta-format etc.?

1. We don't know the size of the file when we start performing the
delta (because everything is stream oriented).
Thus, windows *have* to be used
2. Given a window size that is equal to file size, the delta algorithm
we use will produce smaller results than a diff-like patch.

IOW changing to a patch like format would not solve anything here. If
we knew the size of the files we were performing deltas on ahead of
time, we could make some reasonable estimate as to what window size to
use and get good delta performance.

There are times we know this information, but don't pass it along,
which is kinda sad, but c'est la vie.

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Received on Tue Dec 12 06:19:00 2006

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