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Re: Does the delta editor guarantee that propchangess are precomposed?

From: Philip Martin <philip_at_codematters.co.uk>
Date: 2005-11-08 20:56:55 CET

Malcolm Rowe <malcolm-svn-dev@farside.org.uk> writes:

> In one or two places in libsvn_wc/diff.c, we rely on the fact that
> propchanges are 'precomposed'. That is, if a single node has property
> changes { [A=>x, B=>y], [A=>z] } over two revisions, the delta editor will
> only deliver (via change_file_prop() or change_dir_prop()) the changes
> [A=>z, B=>y], rather than call the function twice, once for each batch
> of changes.

The repository generates the delta by comparing the two trees, it
doesn't look at intermediate trees..

> Is this behaviour currently guaranteed by the tree-delta interface? (and
> if so, where?).

It probably depends on your interpretation of the documentation.

> If not, would it be better to change the tree-delta interface so it _is_
> guaranteed (i.e., document it in svn_delta.h) [and can we make that change
> without breaking compatibility?],

I don't see any harm in doing that.

> or would it be better to 'pessimise'
> libsvn_wc so that it can deal with the possibility that propchanges are
> delivered in batches, even though they aren't (or rather, don't appear
> to be).

I think that would be a mistake.

-- 
Philip Martin
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Received on Tue Nov 8 21:03:36 2005

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