[Dev] subversion replacement

[Brett Wooldridge]

Ryan,

Even though it wasn't on the official list for Nemo, it was on my personal list for this release.  A few months back, I put some work into it checked in as projects org.ziptie.xdiff and org.ziptie.xdiff.macosx.x86 ... using the native xdiff library which supports both text and binary differencing.  The security work I'm doing is moving along, so I was expecting to move on to the new configuration store in the first week of August.

As a brief overview it's pretty straightforward.  Use xdiff to generate "backward facing" differences ... that is, the most recent version of a file is the full version, with deltas that stream into the past.  This allows fast retrieval of the most recent version (like Subversion), with slower retrieval of historical versions due to the iterative application of deltas.  Versions will be stored in the database as BLOBs, one row per version, but the most recent version will be cached in the file-system for performance.  Like Subversion, I would like the version store  to be agnostic with respect to what is being stored, i.e. no explicit knowledge of devices, so that other kinds of things can be versioned if we so choose.  Where applicable by database (MySQL/PostgreSQL) I would like to employ a partitioned table scheme - partitioned by date - which should allow nearly infinite scaling of histories without performance penalty.

If the work is done properly, the existing IConfigStore façade should remain unchanged.  A 9/3 Nemo Beta will be tight, but I think achievable.  However, I doubt that a migration will be ready by that date.  Migrating the existing Subversion store to the new store, while not rocket science, is going to take a bit of work itself.  Historically we haven't had migration in the Release Candidates, but if we take two turns at the RC, it is likely migration would be in the second.

-Brett

On 7/24/08 6:32 AM, "Ryan Kruse" <rkruse at alterpoint.com> wrote:

Brett & Leo,

Let's discuss the subversion replacement strategy.  I think we would all like to see this in the Nemo release, we just need to call out who is working on it, and what 'it' really is.

Go.

Ryan

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