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Re: svn commit: r33075 - trunk/notes

From: Greg Stein <gstein_at_gmail.com>
Date: Mon, 15 Sep 2008 09:13:35 -0700

As Listman noted, that move operation is rare, and I tend to agree. I
can't recall a single time that I've moved a WC. Oh, sure, I probably
have... once. Maybe I'll give you twice even. But I'll take the
position that it is a rare occurrence.
[gstein now waits for the peanut gallery to start yelling "I do it
THREE TIMES A DAY!" and whatnot...]

If a person does it often, then I'd suggest one of two things:

1) keep metadata at the root
2) use <some command> to notify the centralized metadata about the move

And given my prelim thoughts on how the metadata will be structured, I
believe that option (2) will be an O(1) operation. So not a big deal,
but having to do it can be annoying.

Cheers,
-g

On Mon, Sep 15, 2008 at 8:30 AM, Karl Fogel <kfogel_at_red-bean.com> wrote:
> gstein_at_tigris.org writes:
>> --- trunk/notes/wc-ng-design Mon Sep 15 04:22:30 2008 (r33074)
>> +++ trunk/notes/wc-ng-design Mon Sep 15 04:33:54 2008 (r33075)
>> @@ -683,6 +683,16 @@ keyed/named by the MD5 of the file. The
>> appropriate mappings, content/compression types, and refcounts for the
>> base text files (for the shared case).
>>
>> +When the metadata is recorded in a central area (rather than the WC
>> +root), then it is possible for the metadata and the base files to
>> +become out of date with respect to all the working copies on the
>> +system. We will revamp "svn cleanup" to re-tally the base text
>> +reference counts, eliminate unreferenced bases, verify that the
>> +working copies are still present, ensure the metadata <-> WC
>> +integrity, deal with moves of metadata from central -> wc-root (can
>> +happen if somebody rm -rf's the wc, then does a checkout and wants the
>> +metadata at the wc-root (this time)), and other consistency checks.
>> +
>
> This implies bidirectional knowledge:
>
> 1) a working copy W knows where its text bases are
> 2) a text base T knows where its working copies are
>
> (1) obviously has to be true. But if (2) is true, it implies that
>
> $ mv some-wc-root new-wc-root
>
> would leave metadata dangling, because although new-wc-root would know
> where its metadata is, the metadata can't possibly know where
> new-wc-root is. At least until someone does some svn operation in
> new-wc-root.. but even then, how would the metadata know that
> new-wc-root is a rename of some old wc, rather than a copy of it?
>
> This may just mean that 'svn cleanup' can't do everything we want it to
> do, and maybe that's an okay price to pay. I just wanted to point out
> the problem.
>
> Reference-counting is hard; let's go shopping :-).
>

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Received on 2008-09-15 18:13:49 CEST

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