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Re: svn commit: rev 1987 - branches/issue-654-dev/subversion/libsvn_fs

From: Alon Ziv <alonz_at_nolaviz.org>
Date: 2002-05-21 20:35:49 CEST

The lurker strikes again...
Why even ask this question? I mean, woudn't it be safer/easier/better to
always start
deltification _from_ the new version, get its predecessor ID, and deltify
that?

    -az

----- Original Message -----
From: "Bill Tutt" <rassilon@lyra.org>
To: <dev@subversion.tigris.org>
Sent: Tuesday, May 21, 2002 20:28 PM
Subject: RE: svn commit: rev 1987 -
branches/issue-654-dev/subversion/libsvn_fs

>
> > From: cmpilato@tigris.org [mailto:cmpilato@tigris.org]
> >
> [....]
> > +--
> > +
> > +Deltification is currently the only process in place that asks the
> > +question, "Where is my next successor?" Currently the question is
> > +answered by doing a little node revision id mathematics; that's no
> > +longer an option. Input to deltification is still root/path, so what
> > +might a new algorithm be?
> > +
> > +--
>
> This is kind of funky now. A portion of the answer is very similar to
> the problem of "What should my CopyID be for a new NodeRevision I need
> to create now?"
>
> The solution to this general question (as you noticed elsewhere) is to
> acquire it during your path walk.
> i.e.: svn_fs_node_id (&(args.id), root, path, pool)
>
> The other funky part is taking this "successor CopyID" calculation in
> combination with the TxnID ordering.
>
> i.e.:
> get TXN_ID from node revision id.
> Lookup REVISION with TXN_ID
> I = 1
> Lookup the POSSIBLE_SUCCESSOR_TXN_ID for REVISION+I
> While REVISION+I is valid
> AND Not Exists NodeID.<calculated
> CopyID>.POSSIBLE_SUCCESSOR_TXN_ID:
> I++
> Lookup the POSSIBLE_SUCCESSOR_TXN_ID for REVISION+I
>
> If you find a NodeRevision that exists, you've found your successor, and
> you should be able to assert that the predecessor is the NodeRevision
> you started from.
>
> Otherwise there is no possible successor.
>
> Bill
>
>
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Received on Tue May 21 20:37:47 2002

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