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Re: Why do we check the base checksum so often?

From: Hyrum K Wright <hyrum.wright_at_wandisco.com>
Date: Mon, 6 Feb 2012 11:29:55 -0600

On Mon, Feb 6, 2012 at 11:18 AM, Julian Foad <julianfoad_at_btopenworld.com> wrote:
>> Hyrum K Wright wrote:
>
>>> What's driving this discussion is this:  Up until this point in the
>>> Ev2 shims we've been supplying a NULL base checksum for apply
>>> textdelta, which the receivers have dutifully ignored.  However, when
>>> the Ev2 shims attempt to be honest about the fact that they are using
>>> the empty stream for the text base, the receivers start complaining,
>>> because that's not what they expected---even though the end result is
>>> the same.  In essence, all these checks are returning false positives,
>>> which is extremely unpleasant.
>>>
>>> I don't know that there is an easy way around this, since by the time
>>> we're translated from Ev2->delta-editor, we don't have the original
>>> text base, or its checksum, available to us.  We have the full text,
>>> which is the reason the new text base is the empty stream: it's the
>>> only one we need.
>>>
>>> Does that make any sense?
>
>
> Yes that makes sense.  (Sorry I got sidetracked when I thought you were saying the producer should be able to choose any arbitrary base.)

Well, in the *future* I don't think that's as crazy as it initially
sounds, but such things will be left to the individual RA layers to
sort out, as Ev2 doesn't have (nor does it need) any concept of
deltas.

-Hyrum

-- 
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Received on 2012-02-06 18:30:28 CET

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