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Re: Path lookup table

From: Greg Hudson <ghudson_at_MIT.EDU>
Date: 2004-05-30 22:57:38 CEST

On Sun, 2004-05-30 at 16:38, Branko ibej wrote:
> I think that there's no question about using anything _except_ a table
> for directory lookups.

Actually, I think there is a big question. Unlike a regular filesystem,
in Subversion almost all FS usage involves iterating over whole
directories. With appropriate caching, that's very efficient with our
current representation.

> The only issue is optimizing the representation of directory changes.

I haven't the foggiest how we could make progress on this issue.

> I think we need experience with such a table before we can finalize
> any kind of design, that's why I'm proposing to start this transition
> and experience-gathering now.

As you've pointed out before, the ACL and lock tables are expected to be
sparsely populated, and they won't undergo changes in the same manner as
directories. Moreover, neither behaves like directories from a
versioning point of view (locks aren't versioned at all, and ACLs don't
become immutable). So what experience is to be gained here?

A better way to gain experience is to create a new branch (or new FS
module, although that would require a lot of symbol renaming), add the
path lookup table there, and run some performance benchmarks with
real-world data. That has nothing to do with locks and ACLs, of course.

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Received on Sun May 30 22:57:54 2004

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